Numerous robot grippers have been developed to reduce energy consumption by utilizing contact forces with fixed objects. In underwater environments, most objects are not fixed, particularly in the mid and surface layers, posing a challenge for obtaining contact forces. To address this issue, this study proposes a multi-finger gripper that utilizes water resistance for opening and closing actions underwater. As the gripper ascends in water, it closes its fingers, each equipped with a locking mechanism at the tip. This mechanism allows the fingers to maintain a closed shape when converged towards the center and locked. Unlocking occurs when the gripper descends underwater, as the direction of water resistance changes. This design enables locking and unlocking without actuators, offering a solution for grasping underwater objects. The gripper’s underwater movement has speed limits. Below the lower limit, fingers may not achieve sufficient bending, while exceeding the upper limit can cause vibrations and affect the locking function. Therefore, maintaining an appropriate speed is crucial. Finally, gripping experiments were conducted to confirm the gripper’s ability to grasp objects underwater.

Robotic end-effectors have been developed for various applications. Most of them are driven by electric or pneumatic actuator/actuators, which usually make the end-effector bulky and vulnerable due to the external cables and air tubes. In this study, we propose a novel passive robotic gripper with a locking mechanism that does not require any actuators. Locking and unlocking of the gripper fingers are performed through contact with external environment, such as ground, table, and conveyor. To facilitate gripper design, modeling of the deformed finger shape was conducted, and experimental validation was performed. A robotic gripper with eight such passive fingers were fabricated using 3D printer. Experiments were conducted to investigate the grasping capacities in terms of object size and weight. We found that the larger the object, the greater the weight capacity of the gripper, which increased significantly when the object exceeded a certain size. In addition, experiments on grasping various food products were carried out and results suggested that the proposed gripper could grasp objects with complex shapes and soft fragile properties, but damages were caused on very fragile objects due to the rigid structure of the gripper.

Soft actuators are compliant structures that are generally made of elastomers and generates large deformation. The behavior of these structures cannot be estimated accurately using infinitesimal strain theories. The objective of soft robotics applications is the controlled large deformation of these structures. In this article, we propose an analytical model for a pneu-net soft actuator. The model is based on the Euler–Bernoulli finite strain hyperelastic thin cantilever beam theory. The deformation of the air chambers is modeled using finite strain membrane theory. The analytical model is developed for two different states of the actuator: 1) free space; and 2) when the actuator was subjected to tip contact. The proposed theoretical model predicts the deformation and force characteristics of the actuator for the grasping state. The theoretical formulation of the developed model is different from previously developed infinitesimal strain models for the actuator, as it considers the axial stretch and forces applied to the actuator. In addition, it can be theoretically implemented on similar structured actuators for various applications. The theoretically calculated deformation and force characteristics of different actuators are compared with the finite element (FE) model and experimental characteristics. The results suggest that the proposed model can predict the actuator deformation and force characteristics as accurately as the FE model, but the computation time of the proposed model is less than 1% that of the FE model. The proposed model is further implemented on a three-finger gripper to predict the air pressure required for a stable grasp of different objects and is validated experimentally.

In this paper, we propose a simple analytical model for pneu-net soft actuator. The model is based on Euler– Bernoulli finite strain hyperelastic thin cantilever beam theory. The deformation of the air chambers is modelled using infinitesimal strain membrane theory. The proposed theoretical model estimates the deformation and force characteristics of the actuator. The developed model accounts the axial stretch and forces applied to the actuator. The theoretical deformation and force characteristics of different actuators are compared with finite element (FE) model and experimental characteristics. The theoretically estimated deformation and force of the actuator are similar to the FE model, but the theoretical model computation time is less than 1% of the FE model.

Previously, we presented the concept of a novel haptic display device that could generate lateral localized displacement on a human fingertip. This device is characterized by a bundle of haptic pins whose ends gently make contact with a human fingertip. In this paper, we proposed a dynamic model of interaction between haptic pins and finger for investigation of mechanical response of stress or strain on human fingertip under operation of the proposed haptic device. We also conducted preliminary experiment to determine the possible setups that maximizes the sense of partial slippage. The results presented in this paper may help assess human slip perception for the development of haptic display devices.

This paper presents a new approach for active tactile sensation that utilizes soft morphological computation. This work is inspired by human finger's wet-induced wrinkles, which appear after a long time soaking in water, and has been indicated as an efficient means for enhancement of gripping in wet environment. We created a tactile sensing system that is an integration of actuation (pneumatic actuator) and sensing elements (strain gauges). This device can change its morphology so that the posture of embedded sensing elements can vary, then generate different responses depending on the sensing tasks. As a result, this device can actively select its sensing functions depending on different sensing tasks. In this paper, the sensing device is both sensitive to indentation contact and sliding action on its surface by using only one type of strain gauge. This preliminary work is an example of soft morphological control in sensing, and expected to open a new trend in development of tactile sensing system.

This paper describes an active tactile sensing system that selects sensing modalities based on specific sensing tasks, by changing its morphology, called Wrin'Tac. This paper was inspired by the human finger wet-induced wrinkle, which is usually observed when one soaks in warm water for a period, and has been indicated as an efficient transformation for enhancement of gripping stability in a wet environment. We proposed a device which is an integration of actuation (pneumatic actuator) and sensing elements (strain gauges) inside a thin, multilayered substrate. Under pressurization, the morphology of the substrate surface (both geometrical and mechanical characteristics) change with appearance of wrinkles. Especially, by formation of wrinkles, this device can change its shape so that the posture of embedded sensing elements (strain gauges) can vary and generate different responses depending on external load conditions. As a result, this device can actively select its sensing functions depending on specific sensing tasks. First, we created a model to investigate the dynamic changes in a strain gauges' mechanical response under formation of wrinkles. Then, a prototype of this sensing device and its fabrication process were proposed to accomplish sensing tasks under vertical indentation and horizontal sliding action on its surface by using one type of strain gauge. This paper is an example of soft morphological control in tactile sensing, and is expected to open a new avenue to development of tactile sensing systems.

A novel three axis force sensor, based on magnetic flux measurements, was used in the fingers of a gripper. The force sensor uses three Hall Effect sensors orthogonally placed at the base of a hemisphere made of silicon rubber. A neodymium permanent magnet was inside the hemisphere. When a force was applied to the perimeter of hemisphere, it compressed the hemisphere displacing the magnet. This displacement caused change in the magnetic field around the Hall-effect sensors. By analysing these changes, we calculated the force in three directions using a lookup table. This sensor can be used in robot grippers to manipulate objects dexterously with tactile feedback. The cheap construction, robustness and reliability are few advantages of this sensor for it to be used in industrial applications. The sensor design, simulation and its characterization are presented in this work. Furthermore, as an application, a peg in a hole experiment was carried out to present the ability of the sensors to be used in robot grippers for manipulation tasks.

Human-in-the-loop task involving soft contact has become common in robotic application, especially in physical human-robot interaction. In this task, it is required that robot would sense interactions with human by touching, as well as assess possibility of human approaching by proximity sensation. In addition, it is also essential to fabricate an interface so that human does not feel uncomfortable during physical interaction with robot. This paper presents an attempt on fabrication of sensing elements that can be utilized for construction of a soft interface (or a robotic skin). Each element is made from fabrics and soft materials that can sense both proximity and applied force from human's touch. In addition, each sensing element can sense the relative distance of conductive object (or human body) that is approaching the sensing element's surface, and the 2×2 contact force distribution when the object makes contact with the sensing element. By exploiting simultaneous measurement of capacitance, each fabric sensing element can smoothly switch the proximity mode and tactile mode based on position of the object. We also constructed a model that can predict variation of capacitance measurement of proximity and tactile modes during operation for further analysis. The methods and results presented in this paper can be extended to construct a larger scale of robotic skin for robot's body, and act as a platform for study human-robot interaction.

In recent researches relating to robotic fingers, a novel power transmission mechanism had been designed, and developed as Twist-drive Actuators or Twisted String Actuator systems (TSA). These actuation structures, state of the art, include compact designs, light-weight mechanical structures, inherent compliance, and variable gearing, resulting in the fabrication of anthropomorphic robotic hands. However, those studies mentioned position control of the joint, and focused on the control performance of the pulling forces of a twisted string. This paper, therefore, introduces a novel joint mechanism composed of an Antagonistically-twisted Round-belt Actuator (ARA), which is able to make rotating motion by means of contraction forces induced by twisting small-diameter elastic round-belts. A noteworthy point in this paper is that the ARA robot is extremely well-suited for contact force control, which is exerted on the tip of the single joint robot. First, we demonstrate the existence of hysteresis characteristics of static contraction forces induced by the round-belt twisting, in which three belts are simultaneously twisted at constant low-speed. In addition, there exists a stress relaxation phenomenon when strongly twisting the elastic round-belts. We reveal that such sorts of discontinuous and nonlinear properties do not influence control performance in either the contraction force on the belts or contact force on the tip of the robot. Finally, this paper clearly shows stable and accurate tracking performance of the contact force of the ARA robot. In these experiments, we newly develop a twin/triple-twisted round-belt structure for the agonist side actuator, thus enhancing the contact forces effectively.

Difficulties in automatic handling of many food materials are due to their softness and easy deformability by external forces. Excessive deformation of food materials damages their quality and must be avoided. Another difficulty in automatic food handling is the irregular shape and size of food materials, requiring robotic hands to adjust for differences in shapes and sizes. This study describes binding-based robotic handling of food materials, applying the concept of binding to the grasping of food materials. A tension-sensitive elastic thread was used to bind a food material, enabling the force applied to the material to be measured. Based on the concept, we developed a binding hand prototype and performed preliminary experiments to show that this binding hand could pick up a cup with food materials despite its location.

Materials and textures identification is a desired ability for robots. Developing such systems require tactile sensors that have enough sensitivity and spatial resolution, and the computational intelligence to meaningfully interpret sensor data. This paper introduces a texture classification algorithm utilizing support vector machine (SVM) classifier. Data taken from a novel three axis tactile sensor that utilize magnetic flux measurements for transduction was used to obtain the three dimensional tactile data. Frobenius norm calculated from the covariance matrix of the above data and the mean values of the three dimensional sensor data were used as features. Palpation velocity and small vertical load variances had minimum influence on the proposed algorithm. We have compared this algorithm with two other classification methods. They are: classify using the feature spatial period that is calculated from principal frequencies of the textures/material, and classify using neural network classifier with special properties of each material's tactile signals as features. For eight classes of material, the proposed algorithm performed faster and more accurately than the comparators when the scanning velocity and the vertical load varied.

This paper develops a novel robotic joint mechanism by means of twisting a small-diameter round-belt, which enables slow movements of joint rotation unlike direct-drive actuator mechanisms. The actuator mechanism proposed in this manuscript is composed of two small-diameter round-belts located near the joint with opposite configurations. The two round-belts are twisted by DC motors placed on a motor stage, which can be activated by a step motor. This novel mechanism realizes movement of the robotic joint around its axis due to contraction forces generated by twisting both round-belts. That is, these round-belts act as agonist and antagonist actuators for the robotic joint, which give a human-like compliance to the rotational motion of the joint. Experimental results using the proposed one-link robot show that a high position resolution of the joint control can be achieved by increases and decreases in the amount of twisting. In addition, we clearly indicate a linear relationship between twisting and the joint angle of the robot. Finally, this paper reveals that the antagonistic twist-actuator system has a secondary role as a gear reducer that is capable of largely decreasing the velocity of joint movement.

We describe an aerial robot equipped with an upward directed hand on top of a quadrotor airframe for realizing an aerial manipulation task at high altitude, considering a work space above the robot. The aerial robot in this study consists of a small quadrotor platform, a robotic hand module including a gripper and slider mechanism, and an embedded vision system. Positioning of the hand is autonomously performed through a vision-based control system. In this system, position and orientation of a bar-like object is measured and detected through a monocular camera image and FPGA-based on-board processing. Through experiments, the grasping of a bar located above the robot, keeping the grasp with shut off propellers and succeeding take off by releasing a bar was achieved.

This paper describes small-sized pneumatic valves applicable to wearable robotic systems. Pneumatic actuators, especially McKibben actuators and balloon actuators, have been utilized in wearable robotic systems. Although these actuators are light in weight, their control valves are heavy and bulky, hindering the performance of wearable systems. Compact control valves to drive pneumatic actuators are therefore needed. Miniaturized unconstrained valves are novel pneumatic control valves, which, together with their driver circuits (PZT drivers), can drive pneumatic actuators. We have developed miniaturized valves and PZT drivers. A prototype valve 7mm in radius and 9mm in height was capable of controlling 0.5 MPa pressure with 3 l/min flow. Experiments performed to evaluate the developed system showed that these miniaturized unconstrained valves could drive a robotic finger and a manipulator.

This paper focuses on sensing of McKibben actuator shrinkage using a fiber sensor. Control of McKibben actuators requires sensing their shrinkage without preventing their deformation. We applied electro-conductive yarn, with resistance related to its extensional strain, suggesting that measuring the resistance of the yarn can determine its length. The yarn is also bendable and light in weight, thus not preventing the deformation of a McKibben actuator. A fiber sensor consisting of these electro-conductive yarns was attached onto the membrane of a McKibben actuator to measure the distance between both ends of the sensor along the membrane. This paper describes a fiber sensor model that can calculate McKibben actuator shrinkage from the fiber sensor measurement. Based on the model, we investigated the arrangement of a fiber sensor so that the fiber extensional stress is within its allowable range. We then show a prototype of the fiber sensor that was utilized to measure McKibben actuator shrinkage. Experimentally, we found that the shrinkage of an actuator could be measured within 20 % error of its length.

The success in real applications of PID regulator has thought us that it is desirable a simple controller with clear and intuitive policy for tuning of feedback gains, as well as minimum or null dependency on the dynamics of the system. In this paper, theoretical and experimental results of PD-like structures for tracking of robots subject to friction and disturbances is presented. The salient feature of our proposal is a neuro-fuzzy schemes used to a single gain that multiplies the regressor-free PID structure. This bounded time-varying gain plays the role of enforcing a dissipative mapping to obtain exponential stability. Stability is obtained in the sense of Lyapunov and experimental study is presented and discussed, which highlights the viability and feasibility for real applications.

We have proposed a Beam Bundle Model for modeling of a human fingertip during pushing and sliding action with friction, especially stick-to-slip transition, to overcome mentioned issues. In order to construct its three-dimensional non-homogeneous structure, we took sequence of magnetic resonant images, which bring consecutive cross-sectional layers of the human fingertip with distribution of skin, tissue, bone, and nail. Simulation results show a twofold aspect. Firstly, it can generate not only normal force distribution caused by pushing, but also response of friction force during sliding. Secondly, and more interestingly, the model dynamically produces localized displacement phenomenon on the contact area during stick-to-slip phase, which indicates how slippage erodes the contact area before the total slippage of the fingertip occurs. Finally, we investigated role of sliding mechanism acting on human fingertips' contact area in stable lifting of an object, in order to show the potential of the model in studying tactile mechanism of human and apply to robotic systems.

In this paper, we describe the rolling of a tensegrity robot driven by a set of pneumatic soft actuators. Tensegrity is a mechanical structure consisting of a set of rigid elements connected by elastic tensional elements. Introducing tensegrity structures, we are able to build soft robots with larger size. Firstly, we show the prototype of a six-strut tensegrity robot, which is driven by twenty-four pneumatic McKibben actuators. Second, we formulate the geometry of the tensegrity robot. We categorize contact states between a six-strut tensegrity robot and a flat ground into two; axial symmetric contact and planar symmetric contact. Finally, we experimentally examine if rolling can be performed over a flat ground for individual sets of the actuators and discuss the strategy of rolling.

This paper explores the role of anisotropic friction properties in vibratory parts manipulation. We show that direction-dependent surface friction properties can be used in conjunction with a vibrating plate to help design friction-induced velocity fields on the surface of the plate. Theoretical, simulation, and experimental results are presented quantifying the anisotropic friction effects of textured surfaces such as micromachined silicon and fabrics.

A method to generate an appropriate path for manipulation of a belt object is proposed. It is important for automatic manipulation of a belt object such as a film/flexible circuit board to generate an appropriate path for a manipulator because such object is flexible in a certain direction but fragile in another direction and an inappropriate path which causes deformation in the fragile direction may lead to wiring disconnection. First, deformation of a rectangular belt object is modeled considering its bending and torsional deformation under the force of gravity. Next, a method to generate a path for belt object manipulation with quasi-static and non-excessive deformation is proposed. After that, deformation and loaded condition in the path generated by our proposed method and those in a common path based on linear interpolation are compared. Finally, the validity of our proposed method is verified by measuring the deformed shape of a polyethylene sheet during manipulation with the generated path.

In this paper, we are interested in a scheme that proves effective use of soft fingertips for human-in-the-loop telemanipulation. Motion planning is carried out by the human-in-the-loop to grasp and manipulate an object using viscoelastic soft fingertips. In addition, to grasp an object firmly, an estimated torque is synthesized based on fuzzy inference. Experimental results show that the user confidence presents small variations using soft fingertips. Then, the soft fingertips in pHRI induce a more user dexterity than rigid fingertips.

Humans usually distinguish objects by sliding their fingertips on the surface to feel the texture via mechanoreceptor underneath the skin. We have developed a human-imitated system for robotic fingertip to sense object's texture via sliding action. Design of the sensory skin was inspired by the localized displacement phenomenon of a sliding soft fingertip ([1]) to capture stick-slip events on the contact surface that mainly represent texture characteristics. The soft skin is knitted by electro-conductive tension-sensitive yarns, then covered over a hemispherical fingertip. The pile-shaped surface of the fabric sensor enhances tangential traction detection ability of the sensor, even though the normal load is also sensible. Our aim is to exploit this sensor in applications regarding relative sliding between the touched object and the surface of the sensor, such as slip detection ([2]), and surface identification in this paper. In surface encoding, we have experimentally investigated ability of the fabric sensor in recognition touched objects via multiple machine learning algorithms, such as naive Bayes, Multi-Layer Artificial Neural Network (ANN) with input extracted from autoregressive models, and ANN with input extracted from Discrete Wavelet Transformation (DWT), have been trained to distinguish three typical textures. As a result, we have found that the last method outperforms the remains with an average successful rate of 90%.

In modern clinical practices, accurate orientation for needle-like tools inserting into soft tissues is cumbersome, mainly due to the tissue's non-linear deformation and the complicated combination of forces between the tissue and the tool. In this paper, the interaction between tissue deformation and friction forces has been discussed. We consider the relative velocity and contact length as the main factors of friction force during tissue deforming. An available friction model has been built for dynamic needle insertion simulation based on Finite Element (FE) framework. A Local Constraint Method (LCM) is proposed to calculate the tissue deformation and apply the friction forces to the tissue frame for avoiding remeshing. In our approach a series of equivalent constraints and forces are generated by decomposing them inside Local Regions (LRs) to nodal points. Simulations based on this method to realize the dynamic needle insertion have been conducted for validation.

We have proposed a dynamic model to investigate the sliding motion of a 3-dimensional soft fingertip on a plane with friction. The fingertip is comprised virtually of a finite number of elastic compressible and bendable cantilevers whose free ends act as infinitesimal contact points. The contact surface is afterward meshed using finite element method based on coordinates of contact points. By introducing Coulomb's law and contact compliance into each contact point, we are able to assess the frictional characteristic during sliding motions of the fingertip. We also successfully described dynamically localized displacements on the contact surface during stick slip transition, which occurs substantially on hemispherical soft fingertip. Moreover, each simulation trial was implemented in a very small amount of time comparing to commercial softwares, promising use of this model in realtime application In addition, we conducted experiments to valid proposed simulation, including force/moment and vision setups.

Rheological object, such as clay, various food products, biological organs and tissues, has both elastic and plastic properties. Modeling of such objects has not been studied intensively comparing with elastic objects. Previous rheological models were mostly based on linear constitutive law of stress and strain, which is limited to small deformation. In this paper, finite element (FE) model of rheological objects based on linear Cauchy strain tensor was summarized at first. Nonlinear FE model formulated with Green strain tensor was then presented for simulating large deformation and deformation with rotation motion. Instead of constant and symmetrical connection matrices in the linear model, nonlinear model yields non-constant and unsymmetrical connection matrices, which vary with displacements of nodal points. Simulation results with both linear and nonlinear FE models were presented to show the differences. We found that the nonlinear model formulated with Green strain tensor demonstrates more natural simulation behaviors.

We have developed a slip sensor which is knitted by tension-sensitive electro-conductive yarns. When elongating this yarn, its resistance will drop remarkably. Because the yarn is mainly sensitive to deformation along its main axis, a special way to knit these yarns has been proposed to form a slip sensor. This sensor is used in detection of the human fingertip's slip during rubbing action on its surface. We found that, a simple derivative of the sensor's output was sufficient to detect slippage. However, in some cases, the sensor gets troublesome to distinguish between change of normal load and the occurrence of slip, since human implements their action without caring much about keeping the stable applied force on the sensor. Therefore, a well-known DWT (Discrete Wavelet Transform) method is employed to overcome this problem. As a result, depending on the purpose of the application, several data processing methods are employed to detect slippage of human's rubbing action, or robotic fingertip. Results in this paper promise an applicable sensory mean, which can be employed in haptic devices, teleoperation, or robotic skin.

We describe the development of a tactile hemispherical soft fingertip (FT) of a size similar to that of a human thumb. The sensory core consists of a microscaled force/torque sensor that can output one component of force and two components of moment simultaneously, which was developed beforehand. This sensor is embedded in a polyurethane rubber hemispherical dome to form a complete soft, compliant, and perceptible robotic FT. This system is designed for easy fabrication, high reliability in outputting signals, and stable operation. Static and dynamic mathematical analyses were utilized to investigate the responses of the sensor during the typical sliding motion of an FT. This was followed by experiments to show its potential in tactile and texture recognition. Especially, incipient-slip detection, which is critical in grasping manipulations, can be assessed properly and in a timely way. The development of this tactile FT is considered significant in the field of dexterous manipulation.

This paper describes our initial research on development of a tactile sensor, which can be employed in anthropomorphic soft fingertips, with multi-sensing points that uses 3-DOF micro force moment sensing chips (MFMS) which are able to measure forces up to nearly a Newton. Three sensing points are integrated on a compact printed circuit board with an in-built multiplexer circuit for the purpose of saving energy and reducing the number of outputs. This system was designed for the purpose of manipulating small-scaled objects, and realizing special characteristics of the objects such as distribution of edges/borders. The process including design, fabrication, and calibration will be explained in detail in this paper.

We describe here our proposed method to investigate the sliding motion of a soft fingertip in the dexterous manipulation. This paper focuses on analyzing dynamic sliding motion of a 2-dimensional (2-D) soft fingertip on a plane. To investigate the deformation of the fingertip during this process, we consider the soft fingertip as if it was composed of a finite number of elastic cantilevers which are compressible and bendable. Simulation will be carried out firstly on this 2-D model of soft fingertip, focusing on the analysis of incident slip-page. After that, various experimental results will be shown to verify this model.

We have previously shown that hemispherical soft fingertips are at equilibrium when they are in contact with objects, suggesting that the contact force and flexibility of these soft fingertips are important for stable grasping and manipulation. Hence, by making use of these characteristics, soft fingers can manipulate objects dexterously. While our previous work has focused on pairs of 1-DOF fingers with soft fingertips, we present here a control scheme by which a pair of 2-DOF soft fingers can control a grasped object's planar location. This new control scheme consists of a proportional controller of finger joint angles and an integral controller of object location. We subsequently describe our formulation of the equations of motion of manipulations performed by a pair of 2-DOF soft fingertips. We then apply this control scheme to an experimental situation and to a simulation based on a parallel distributed virtual spring model to control the planar location of a grasped object. These findings demonstrate the validity of the proposed scheme. Finally, we show that extending the theory of the proposed controller can lead to the control of grasping forces.

A differential geometry based modeling of a belt object to represent its deformation path is proposed. Adequate deformation path of a belt object such as film circuit boards or flexible circuit boards must be generated for automatic manipulation and assembly. First, deformation of a belt object is described using the curvature of its central axis, torsion around the central axis and the curvature in the transverse direction. Second, a method to derive an adequate transition of the object shape from the initial state to the final state is proposed. It can be derived by minimizing the maximum of the local potential energy in the belt object during its manipulation. This is because locally excessive potential energy often leads to the excessive stress that makes fractures in the belt object. Finally, the validity of our proposed deformation path is verified by estimating the maximum local potential energy in a belt object.

This paper formulates the dynamics of 5 degrees-of-freedom (DOFs) robotic hand that consists of an index finger and an opposable thumb like the human hand. This system has two geometrical constraints and five velocity constraints generated during the object manipulation task. The three of the velocity constraints are associated with the joint angles of the robot, and are combined to the proposed system on the basis of observations about the fact that the distal two joints of the index finger are mechanically coupled. Based on the equations of motion including these constraints, we perform precise orientation control of a rectangular object grasped by the 5-DOFs robotic hand in the situation that grasping forces are not defined during the manipulation. The manipulation task given is one-finger control (index finger), for which a serial two-phased (STP) controller that had previously been proposed is modified. In experiments, we demonstrate that a simple integral controller designed by eliminating the second stage of the STP controller works well in the soft-fingered manipulation. In both simulations and experiments, it is clearly indicated that Jacobian matrices and the grasping forces are not necessarily required in the control law for accomplishing dexterous manipulation tasks. In other words, it is implied that a complete modelless and grasping-forceless control can be achieved in the task-space control.

Traditional Japanese sweets have long history and intense cultural background. In order to automate the manufacture process and also hand down the skillful techniques of sweets making, it is necessary to investigate the mathematical models of such objects and estimate their physical properties. This paper introduced a five-element physical model to describe the deformation behaviors of such materials. Using finite element (FE) method, a 2D/3D FE dynamic model was formulated to simulate arbitrary shaped objects. An approach for estimating physical parameters was then proposed based on FE simulation and nonlinear optimization. To capture both forces and deformation behaviors, two sets of parameters were identified and employed to simulate real Japanese sweets. A series of experimental results validated the FE model and property estimation method.

We have investigated the deformation of a soft fingertip when it slides. This process was first simulated using the non-linear Finite Element Analysis (FEA) method. Based on the results of this simulation, we designed experiments to observe the sliding and object grasping of a soft fingertip, in which a 3-DOF (degree of freedom) micro force/moment sensor was embedded. With this sensor, forces and moments acting in the fingertip are measured based on the piezoresistive effect. These measurements provide information on the status of contact and sliding of a soft fingertip on a surface. Based on these results, incipient slip, which has an important role in object gripping by a robot manipulator, can be realized. Textile's texture recognition experiments were also conducted to assess potentials of the fingertip in tactile and texture perception.

This paper focuses on three-dimensional grasping and manipulation by robotic fingers with soft fingertips. The authors have proposed two-dimensional parallel-distributed model of a soft fingertip to describe the dependency of its potential energy to the relative orientation between the fingertip and the object. Here we extend the previous two-dimensional model to three-dimensional model, incorporating the rotation in three-dimensional space. We formulate the elastic potential energy stored in a soft fingertip due to the contact with the planar surface in three-dimensional space. We sketch the Lagrangian of the system consisting of a rigid prism grasped by three fingers with soft fingertips.

This paper presents wiping motion as a task during which the movement and deformation of a deformable object occur simultaneously. During the wiping motion of a deformable object, there is contact, but no relative movement, between the manipulator and the object, while there is both contact and relative movement between the object and the floor during the displacement of the object. We first describe wiping motion and distinguish wiping slide from wiping deformation by displacement of the internal points of an object. In addition, we show that a wiping motion is an extended system of pushing and sliding of rigid objects. As an example of wiping motion, we utilize grasping of a fabric, and we demonstrate the grasping motion of a fabric using a single-armed gripper.

In this paper, we describe the design of a deformable robot with a tensegrity structure that can crawl and we show the results of experiments showing the ability of these robots to crawl. We first describe a tensegrity structure, composed of struts and cables, and its characteristics. We next explain the principle of crawling by robot body deformation, followed by a classification of the methods by which a body can be deformed and the contact conditions of the robot through the cable-graph of the tensegrity structure. We also describe topological transition graphs that can visualize crawling from each initial contact condition. We then discuss the characteristics of the proposed robot in terms of design freedom. Finally, we show experimentally that the prototype of a tensegrity robot can crawl.

A differential geometry based modeling to represent belt object deformation is proposed. Deformation of a belt object such as film circuit boards or flexible circuit boards must be estimated for automatic manipulation and assembly. First, the fishbone model to describe deformation of a rectangular belt object is explained. In this model, the object shape is represented by the curved ldquospine linerdquo and straight ldquorib linesrdquo. We can estimate deformation of the object by minimizing its potential energy under geometric constraints. Next, this model is modified to represent deformation in which the rib line at an endpoint does not coincide with the transverse edge. Moreover, the modified model is applied to a belt object with angles. The deformed shape of an angled object can be derived by separating it into rectangular parts and angled parts and by assuming that each angled part forms a part of a cylindrical surface. Finally, the validity of our proposed model is verified by comparing the computed shape of an L-shaped belt object with its measured shape.

There are many kinds of deformable objects in our living life. Some of them exhibit rheological behaviors when they are subject to external force, such as human tissues, human organs, and food. If we want to simulate or control such behaviors, we have to know the physical parameters of the object in advance. In this paper, we propose an approach to identify these parameters based on 2D finite element (FE) simulation and measurement of deformation and force. At first, 2D FE model used to simulate rheological deformation was described. Then, identification method was presented according to the analysis of simulation results. Identification results for simulation were also given. Finally, this method was applied to a object made of clay. Deformation and force were measured by camera and tactile sensor respectively. The identification results show the validity and effectiveness of this method.

There are many kinds of deformable objects in our living life. Some of them such as human tissues, human organs, and food exhibit rheological behaviors when they are subject to external force. In surgery simulation and food engineering, we need to simulate or control such behaviors. In this paper, four-element model associated with finite element (FE) method was employed to model rheological deformation. This model can reach a good approximation of rheological force response when the object experience a standard strain input. An identification approach for estimating physical parameters of rheological deformation was presented based on 2D FE simulation and nonlinear optimization. This identification method aimed at minimizing the difference of force response between the simulation and experiment by using nonlinear least square method. Finally, experiments and identification results were given and both modeling and identification method were validated by comparing the results of simulation and experiments.

This paper describes a stochastic static analysis of link angle driven by actuator bundles. We first demonstrate a movement of a link driven by actuator bundles in terms of high driving force. The variation of actuator parameters influences the movement of this mechanism. We confirm the link may shift and twist because of the variation of actuator parameters. We then introduce stochastic analysis to investigate the link angle considering the variation of actuator parameters. In the result, the variation of the link angle converges to zero when the number of actuator is large enough. In addition, we reinforce the result through dynamic simulation considering the variation of the parameters of actuators.

We have investigated the deformation of a soft fingertip when it slides. This process was first simulated using ANSYS software with non-linear Finite Element Analysis (FEA). Based on the results of this simulation, we designed experiments to observe the sliding and object grasping of a soft fingertip, in which, a 4-DOF (degree of freedom) micro force/moment sensor was embedded inside the soft fingertip. With this sensor, values of force and moment acting in the fingertip are measured, based on the piezoresistive effect. These measurements provide information on the status of contact and sliding of a soft fingertip on a surface. Based on these results, incipient slip, which has an important role in object gripping by a robot manipulator, can be realized.

Microparts can be fed along an asymmetric surface using simple planar symmetric vibrations, because they adhere to the surface asymmetrically. We assessed an asymmetric surface microfabricated by femtosecond laser process. The tribological characteristics were evaluated by measuring the angle of friction of these capacitors. Using the results of feeding experiments of these capacitors, we assessed the relationship between driving frequency and feeding velocity.

This study clarifies that secure dynamic manipulation by a pair of soft fingertips can be achieved easily without any information of a grasped object, which is called Blind Manipulation. First, we describe two holonomic constraints and two nonholonomic constraints induced by minimum dof soft-fingered grasping. Next, we represent Lagrangian of the soft-fingered hand system that includes the elastic energy of the fingertip, the four constraints, and also gravity effect. Furthermore, we express equations of motion of the grasped object from the Lagrangian, and simulate the dynamic behavior of the object. Finally, we clarify that the position and posture of the object always converge to a corresponding point when a pair of fingers is freely activated.

As jumping is an effective method of moving over rough terrain, there is much interest in building robots that can jump, and deformation of a soft robot's body is an effective method to induce jumping. Our aim was to investigate the effect of the initial shape of deformation of a circular shell made of spring metal. Four initial shapes of deformation: dish, peanut, cup and cap, jumped the highest in that order, with the dish jumping twice as high as the cap. A simulation of a model was in good agreement with the observations.

We introduce a robotic prototype of an arm with a loosely coupled joint, modeled on the human joint. A viscoelastic object functions as cartilage and soft actuators as muscles. First, we show that although viscoelastic object affords smooth movement owing to shift in the center of rotation, the repeat accuracy of the joint is poor under open-loop control. The repeat accuracy was much improved by visual feedback. Under P control, the prototype was shown to be highly robust against mechanical disturbance owing to its good mechanical compliance.

This paper describes realtime and robust tracking of a planar motion target by matched filter implemented on the CMOS+FPGA vision system. It is required to obtain positional and angular signals around 1,000 Hz to control a mechanical system. A vision sensor must obtain visual features of a target object, synchronizing its sampling rate to the sampling rate of the control. The CMOS+FPGA vision system has been proposed to realize 1,000 Hz visual feedback. Matched filter can compute the position of a target robustly against occlusion, change of illumination, and background texture but requires much computation time since it includes 2D Fourier transform of images. Thus, matched filter algorithm is implemented on the system so that the matched filter can be performed in realtime. First we briefly introduce the CMOS+FPGA vision system. Second, we summarize the algorithm of matched filter to describe the design of the circuit performing matched filter on an FPGA. Finally, we show the experimental results of planar motion tracking by matched filter implemented on the system.

The greatest characteristic of soft-fingered manipulation is its softness and flexibility during manipulating operations. In previous works, this intrinsic property had been quantitatively explained from the viewpoint of physical and mechanical perspective that the deformation energy induced by large elastic distortion automatically has a minimum equilibrium point. Hence this report first derive equations of motion of two-fingered soft finger robotic hand on the basis of energybased analysis, and explain that an equilibrium point on a combined energy function exists even in the case of manipulating motions by the hand. In this paper, the equilibrium point is called LMEEwC that is unfolded as Local Minimum of Elastic Energy with Constraints. Next, we show that the posture control of a rigid object grasped by the minimal degrees-of-freedom hand can easily be achieved by applying a two-phased controller associated with each joint angle of the hand, which is newly proposed in this report. This control scheme is constructed by two parts: a PD controller with respect to the finger angle and an integral controller with respect to the orientation of the grasped object. The characteristics of the control method of the latter part is that the desired joint angle of the hand is produced dynamically by the integral controller with respect to the object orientation. Finally, we clarify the effectiveness of the proposed control method in the case of the soft-fingered manipulation.

We describe here a mechanism for controlling angles of a human-like joint using length sensors in threedimensional (3D) space. This joint mechanism, which is called a loosely coupled mechanism, includes a viscoelastic object and soft actuators in place of the cartilage and muscles of a human arm. To confirm motion of the link using one length sensor, we constructed a prototype of the mechanism in two-dimensional (2D) space. Based on this prototype, we constructed a 3D loosely coupled mechanism with length sensors, and we were able to control two projecting angles of the 3D prototype. In addition, we propose an appropriate method of measurement to reduce errors in measurement due to the length sensors. Using this method, we found that, for each projecting plane, the errors were less than 1.0 deg in our 3D prototype.

This paper describes the measurement of inner deformation of a rheological object using ultrasonic and MR images and comparison the measured and simulated deformations. We apply finite element (FE) model to simulate elastic, viscoplastic, and rheological deformation of soft objects. Ultrasonic and MR images are used to reveal the inner deformation of a soft object. Here we report the measurement and its evaluation by comparing measured and simulated deformations

This paper describes the dynamic modeling of linear object deformation considering geometrical constraints and contact with obstacles. Deformable linear objects such as cables and strings are widely used in our daily life, some industries, and medical operations. Modeling, control, and manipulation of deformable linear objects are keys to many applications. We have formulated the static deformation of a linear object using the differential geometry coordinates. In this paper, we apply differential geometry coordinates to the dynamic modeling of linear objects. First, we formulate dynamic 2D deformation of an inextensible linear object based on a differential geometry coordinate system. Second, we consider dynamic deformation of the linear object when forces/moments and geometrical constraints are imposed on the object. Third, we model contact of a linear object with a circular obstacle. It can be applied to self-contact of the linear object. Finally, we show simulation results using the proposed modeling technique

This paper provides that an elastic force and an elastic potential energy due to the deformation of soft fingers, which are previously derived, can be calculated into straightforward equations in an analytical way. These formulae lead to the fact that the potential energy of a soft fingertip is a function of two variables, and has a local minimum through the elastic rolling of a contacting object. We formulate four geometric constraints in grasping motions of a rigid object by means of two degrees of freedom robotic hand that has two rotational joints. We define a basic motion including translational and rolling motions when two fingers rotate by infinitesimal angle, and propose a quasi-static manipulation and its algorithm by using the local minimum of elastic potential energy (LMEE) of soft fingers with geometric constraints. In this theory, we define an energy function included in the LMEE algorithm. By solving that function we simulate the path of the center of gravity and the change of orientation of the grasped object, and compare those values with measurements experimentally obtained from a CCD camera equipped above the manipulated object. Finally, we confirm the effectiveness of the quasi-static manipulation theory based on the LMEE algorithm from experiments

One of features of soft object manipulation is motion during deformation of the soft body. We analyze the stability of soft object manipulation by simultaneous control of motion and deformation. We model and formulate manipulation by simultaneous control of the motion and deformation of soft object. We then use the symmetric linear mass-damper-spring model for a simple analysis of its dynamical behavior. Second, we analyze the stability of the system. Thus, we show that an adequate feedback gain stabilized the system in PID control. This adequate feedback gain ranges between two positive values. The object cannot be stably controlled at too high a gain; neither can, it be regulated at too low a gain since the object is movable. Furthermore, we unravel the features of soft object manipulation by simultaneous control of motion and deformation

This paper describes a 1,000 Hz visual feedback using the CMOS+FPGA vision. It is required to obtain positional and angular signals around 1,000 Hz to control a mechanical system. A vision sensor must obtain visual features of a target object, synchronizing its sampling rate to the sampling rate of the control. Thus, we need 1) image capturing over 1,000 Hz with high resolution, 2) visual feature computation at the capturing rate, and 3) visual feature transmission to a control system with little delay. We propose the CMOS+FPGA vision system to realize 1,000 Hz visual feedback. This system consists of a CMOS image detector to capture images at 1,000 Hz and an FPGA to compute image features at this sampling rate. First we introduce the CMOS+FPGA vision system. Second, we show the implementation of the computation of the image gravity center. Then, we show the implementation of matched filter. Finally, we apply the image gravity center circuit to the visual control of a flexible link

A planning method for unraveling manipulation of deformable linear objects is proposed. In manipulation of a linear object, its raveling must be avoided. It takes much time to unravel it once it is raveled. Therefore, it is important to generate unraveling plans efficiently. First, a manipulation process of a linear object including its unraveling is represented as a sequence of its crossing state transitions. Then, possible manipulation processes can be generated once the initial and the objective crossing states are given. Second, qualitative actions to realize manipulation processes are determined. Third, a method for unraveling a linear object as far as possible when its crossing state can not be identified completely is proposed. Finally, an example of unraveling process generation is demonstrated

This paper describes a 1,000 Hz visual feedback using the CMOS+FPGA vision. It is required to obtain positional and angular signals around 1,000 Hz to control a mechanical system. A vision sensor must obtain visual features of a target object, synchronizing its sampling rate to the sampling rate of the control. Thus, we need 1) image capturing over 1,000 Hz with high resolution, 2) visual feature computation at the capturing rate, and 3) visual feature transmission to a control system with little delay. We propose the CMOS+FPGA vision system to realize 1,000 Hz visual feedback. This system consists of a CMOS image detector to capture images at 1,000 Hz and an FPGA to compute image features at this sampling rate. We implement two vision algorithms to track planar motion on the CMOS+FPGA vision system. First we introduce the CMOS+FPGA vision system. Second, we show the implementation of the computation of the image gravity center. Then, we show the implementation of matched filter

A planning method for unraveling deformable linear objects based on 2D information about their crossing states is proposed. In manipulation of a linear object, its raveling must be avoided. It takes much time to unravel it once it is raveled. Therefore, it is important to generate unraveling plans efficiently. First, an unraveling process of a linear object is represented a sequence of crossing state transitions. It can be generated on a computer if 3D information about the current crossing state is given. Second, the crossing sequence of a linear object, which corresponds to its 2D information, is categorized into two types: unravelable and not-unravelable. Third, a procedure to generate efficient unraveling processes based on unravelability of the crossing sequence is explained. Finally, examples of unraveling process generation with our developed system are demonstrated

We propose a straightforward static elastic model of a hemispherical soft fingertip undergoing large contact deformation, as occurs when robotic hands with the fingertips handle and manipulate objects, which is suitable for the analysis of soft-fingered manipulation because of the simple form of the model. We focus on formulating elastic force and potential energy equations for the deformation of the fingers which are represented as an infinite number of virtual springs standing vertically. The equations are functions of two variables: the maximum displacement of the hemispherical fingertip and the orientation angle of a contacting planar object. The elastic potential energy has a local minimum in our model. The elastic model was validated by comparison with results of a compression test of the hemispherical soft fingertip

We derive a local minimum of an elastic potential energy due to the deformation of a hemispherical soft fingertip, and propose a quasi-static manipulation algorithm using the local minimum of the potential energy by means of two rotational fingers, on which the soft fingertips are mounted. In this model, a geometrical constraint between the grasped object and two fingertips, which includes the deformation of the fingertip, is derived. Using the constraint and the local minimum of the potential energy, we newly propose a numerical algorithm in the quasi-static manipulation. Finally, we conclude that the existence of the local minimum allows us to stably grasp an object in soft fingered manipulation.

This paper proposes a new contact deformation model between a hemispherical soft fingertip and an object. First, we develop our proposed contact model, in which an elastic potential energy is formulated. Second, we show that the elastic potential energy due to the deformation of the soft fingertip is proportional to the cube of the maximum displacement of that fingertip. Also, it is firstly shown that the elastic force and the potential energy are functions of two variables: the maximum displacement and the orientation angle of the contact object. The most important point is that the potential energy of the fingertip have a local minimum when the object contacts with the soft fingertip keeping a vertical direction. Finally, we show that the local minimum of the elastic potential energy also appears in experiments.

This paper investigates micro-parts feeding using a saw-tooth surface. In parts feeding, the driving force applied on each part must vary according to the direction of motion of the part so that the part moves in one direction. Traditional feeders employ oblique or asymmetric vibration of the feeder surface, which often causes unstable motion of micro-parts. In this paper, we propose micro-parts feeding using a saw-tooth surface with simple planar and symmetric vibration. First, we describe the principle of the proposed technique. We then develop a model describing the contact between a micro-part and a saw-tooth, and formulate the condition for feeding. Next, we conduct experiments to assess the feasibility of micro-parts feeding by the proposed method. Finally, we discuss how well the feeding model fits experimental results.

We describe circular/spherical robots for crawling and jumping. Locomotion over rough terrain has been achieved mainly by rigid body systems including crawlers and leg mechanisms. This paper presents an alternative method of moving over rough terrain, one that employs deformation. First, we describe the principle of crawling and jumping as performed through deformation of a robot body. Second, in a physical simulation, we investigate the feasibility of the approach. Next, we show experimentally that prototypes of a circular robot and a spherical robot can crawl and jump.

A planning method for knotting/unknotting and tightening manipulation of deformable linear objects is proposed. It is important for linear object manipulation in industrial/medical field to analyze knotting. Modeling of knotting/unknotting process is useful for design of knotting/unknotting system with different mechanism from human arms/hands and manipulation planning suitable for such system. Firstly, knotting/unknotting processes of a linear object is represented as a sequence of finite crossing state transitions. Secondly, grasping points and their moving direction to perform each state transition are defined. Then, possible qualitative manipulation plans can be generated on a computer system once the initial state and the objective state of a linear object are given. Thirdly, a planning method for tightly tying is proposed. Pulling parts for tightening knots can be determined by using this method. Finally, an experiment for tying an overhand knot by our developed system is shown.

This paper describes the dynamic modeling of linear object deformation based on differential geometry coordinates. Deformable linear objects such as cables and strings are widely used in our daily life, electric industries, medical operations. Modeling, control, and manipulation of deformable linear objects are keys to many applications. We have proposed the differential geometry coordinates to describe the 2D/3D deformation of a linear object with the minimum number of parameters. Based on this description, we have formulated the static deformation of a linear object using the differential geometry coordinates but the dynamic deformation has not been investigated yet. In this paper, we apply differential geometry coordinates to the dynamic modeling of linear objects. First, we formulate the dynamic 2D deformation of an inextensible linear object based on a differential geometry coordinate system. Second, we show simulation results using the proposed modeling technique. Next, we apply the proposed dynamic modeling to the control of a flexible link.

We analyze the stability of dynamic control on contact with a soft interface, the viscoelastic material between a manipulating finger and manipulated object. First, we model a dynamic control system on contact with a soft interface. The system is described in continuous-discrete time. Second, we formulate the dynamics using the modified z-transform in the continuous-discrete time system for feedback and feedforward control. Thus, we show that the stability of the system depends on viscoelasticity of the soft interface for feedback control. In particular, we point out that, in critical stability, the relationship between material viscosity and sampling time is not monotonous. Next, we analyze this phenomenon by the root locus method. Finally, we compare the stability analysis by the modified z-transform, simulations based on the Runge-Kutta method, and a regular z-transform. Thus, we demonstrate that the relationship is specific to the continuous-discrete time system.

In this work, we propose a new framework for better deployment and utilization of robots in our uncertain, unstructured everyday environments. Programming robots can be a very time-consuming process and seems almost impossible for ordinary end users. To cope with many challenges in the user programming, this work is to provide an open environment for building robot programming automatically, where we have robots learn how to accomplish commanded tasks interacting with the object. An integrated sensing and computing tag is embedded into every single object in the environment. In the robot controller, only the basic software libraries for low-level robot motion control are provided by the robot manufacturer. The main contributions of this work is to develop the knowledge integrator platform that we call Omniscient Organizer that generates the application programs and send them to the robot controller through networks. In the Omniscient Organizer, the object-related information downloaded from the object Web server merges into robot control software based on the task commands from the human. We have built a test bed and demonstrated that a robot can perform common household tasks such as clearing the table within the proposed framework.

This paper proposes a new contact model of a soft fingertip attached on a rotational finger of one degree-of-freedom. We analyze the deformation of the soft fingertip statically, and introduce a virtual spring as an infinitesimal component of the soft fingertip. We correlate the derived force equation with a pressure distribution acting on a sensing plane. Finally we compare simulation results and experimental results to demonstrate our theoretical pressure model.

This paper characterizes the dynamic deformation of soft fingertips applied to multi-fingered object manipulations of humanoid robots and analyzes its significance for multi-fingered operations. To this end, we present a dynamic model for soft-fingered object manipulations. For analyzing the control performance of soft-fingered manipulating tasks, we present a dynamic manipulation control scheme that considers the deformation effects of soft fingertips. The simulation results validate the influence of the dynamic deformation of soft fingertips during manipulation in a two-fingered operation, and will enable us to recognize its significance for precise manipulating tasks.

In this paper, we propose a novel approach to extracting rheological properties of deformable objects based on Haptic vision, which was proposed for vision-based automatic construction of virtual environment simulators. The method consists of two parts: 1) the "touch and see" part to cause deformation behavior by exerting known contact force on the object using a robot hand, and then observe how the deformed shape return to the original after contact force is removed, using a range sensor and a force-feedback sensor mounted on the robot hand, 2) the analysis and parameter extraction part from the acquired range images and force-feedback data. Experimental results using springs and wheat dough demonstrated the validity and effectiveness of the proposed approach to viscoelastic parameter extraction of rheological objects.

A planning method for linear object manipulation including knotting/unknotting by one hand is proposed. Firstly, topological states of a linear object are represented as finite permutations of crossing points. Secondly, transitions among topological states are defined. Then, we can generate possible sequences of state transitions, that is, possible manipulation processes from the initial state to a given objective state. Thirdly, a method for determination of grasping points and their moving direction is proposed in order to realize derived manipulation processes. Furthermore, a planning method for one-handed manipulation is proposed. Knotting by one hand is possible as any manipulation processes can be realized by iteration of one-handed operations. Finally, it is demonstrated that our developed system based on the above method can generate manipulation plans for raveling out of an overhand knot.

We describe the implementation of a vision algorithm based on matched filtering on an FPGA. Detection of a reference image in an input image must be performed in real-time and robustly against occlusion and change of illumination. Vision algorithm based on matched filtering can perform the detection robustly but requires much computation time since it includes 2D FFT/IFFT and polar transform. In this article, we implement the algorithm on an FPGA so that the detection is performed in real-time and robustly.

This paper provides the fundamental dynamic deformation features for soft-fingered object manipulation tasks. To this end, we present a dynamic model for an object manipulation system by a two-fingered hand using soft fingertips. The model reveals that soft fingertips employed in a multi-fingered hand lead to certain deformation effects during object manipulation that are closely related to the motion control of the manipulated object. Through several experimental works, we discuss on the deformational influence of soft fingertips during manipulation in a two-fingered operation.

In this paper, we compare two major structures of MSD (mass-spring-damper) particle models. One is the lattice (hexahedral) structure, and the other is the truss (tetrahedral) structure. They (especially, the truss structure) have been frequently used for representing elastic and/or visco-elastic object. The MSD model efficiently calculates shape deformation of the above materials. In addition, in order to maintain shape precision of each deformation, we carefully calibrate coefficients of damper and spring of Voigt part and a coefficient of damper of the other part in the basic MSD element under many surface points capturing a real rheologic object. A genetic algorithm is used for probabilistic calibration. After the comparison, we get the following properties: (1) the lattice structure has too many elements for calculating force propagation. Therefore, it precisely leads shape deformation with the help of the local (feedforward) volume constant condition. (2) The truss structure does not have enough elements for propagating internal forces, therefore, in order to keep a reasonable volume by expanding its virtual rheology object, we need the global (feedback) volume constant condition. (3) The global condition is time consuming, but can directly control the total volume of virtual rheology object. On the other hand, the local one is quick, but directly expands only a part (voxel) of the virtual object. Therefore, the volume and shape in the lattice structure with the local condition are better than those in the truss structure including the global one. (4) The number of MSD elements in the lattice structure is about two times larger than that in the truss one. Therefore, the former calculation is about two times slower than the latter one. As contrasted with this, the global volume constant condition is strictly two times or slower than the local one. As a result, calculation time of the lattice structure with the local condition is smaller than that of the truss structure with the global one. In conclusion, the lattice structure with the local volume constant condition is the best concerning to calculation cost and shape precision.

This paper describes a stability and graspability analysis in grasping task, taking fingertip dynamics into consideration. First, a soft-fingered grasping task is modeled and formulated. A stability analysis is presented using formulated equations. We also show that grasping force converges to a constant value that is independent of fingertip dynamics. Using a soft-fingered hand mechanism that we built, we confirm that grasping force can easily be regulated by controlling saturated P. Second, through simulation, we verify the effect of fingertip dynamics on sampling time. We investigate the dependency of fingertip dynamics and sampling time on graspability. In addition, we build a variable dynamics fingertip (VDF) to confirm the simulation results.

We describe crawling and jumping by a deformable soft robot. Locomotion over rough terrain has been achieved mainly by rigid body systems including crawlers and leg mechanisms. This paper presents an alternative method of moving over rough terrain, one that employs deformation. First, we describe the principle of crawling and jumping as performed through deformation of a robot body. Second, in a physical simulation, we investigate the feasibility of the approach. Next, we show experimentally that a prototype of a circular soft robot can crawl and jump.

A physical modeling of rheological objects is presented. Objects showing rheological nature involve foods and biological tissues yet no systematic approach to build their virtual objects is not established. In this article, we will construct 2D/3D virtual rheological objects.

In this paper, a hemisphere-shaped soft fingertip for soft fingers is developed and its modeling based on force distribution is presented. We first analyze the geometrical relation of the soft fingertip when it is deformed. Secondly, the force distribution of the soft fingertip is investigated by using a compressional strain mechanism. And then, we propose a nonlinear model of the soft fingertip which enables us to obtain the total contact force at the contact surface of each finger in manipulating tasks. Finally, the proposed force function is verified by experiment, where a tactile sensor is used to measure the contact force distribution in the contact surface and its total force. The developed soft fingertip and its force function can be usefully applied to soft-fingered manipulations.

Real-world objects exhibit rich physical interaction behaviours on contact. Such behaviours depend on how heavy and hard it is when held, how its surface feels when touched, how it deforms on contact, etc. Recently, there are thus growing needs for haptic exploration to estimate and extract such physical object properties as mass, friction, elasticity, relational constraints etc.. In this paper, we propose a novel paradigm, we call haptic vision,which is a vision-based haptic exploration approach toward an automatic construction of reality-based virtual space simulator, by augmenting active vision with active touch. We apply this technique to mass, relational constraints estimation and elasticity, and use these results to construct virtual object manipulation simulator. Experimental results show that feasibility and validity of the proposed approach.

We propose a simple contact model of a soft fingertip based on geometrical analysis and statics of the fingertip. First, we introduce a virtual spring system to the soft fingertip corresponding to one and two-dimensional contact between a planar object and a soft fingertip. Second, we describe pressure distribution, and estimate that equation by simulating and measuring total force and pressure center using tactile sensors. Finally, we describe how to obtain the orientation of an grasped object and the maximum displacement of a soft fingertip from the tactile sensor measurement.

This paper focuses on the fundamental deformation effect of soft fingertips as applied in soft-fingered object manipulations. In order to analyze the deformation effect, we first describe the dynamic relation of a two-fingered object manipulation using soft fingertips. From the dynamic relation, we show that the fundamental deformation effect of soft fingertips is essential for soft-fingered manipulations. A dynamic manipulation control method considering the deformation effect is also proposed. Simulation results show that the deformation effect of soft fingertips during the manipulation process is crucial for stable manipulation. Finally, we conclude that the deformation effect of soft fingertips is desirable to be properly considered in a manipulation control law for successful soft-fingered manipulation tasks.

A simple but useful concept for the actuation of finger prosthesis, using the ability of remaining natural fingers of a partially deformed human hand, is presented in this work. The design is based on very simple principles drawn from the concept of opposition space. A prosthetic mechanism for a hand, which has lost a thumb but retains the abilities of the other fingers, is developed as an example to demonstrate the concept. This presentation is a system integration of the concept, design, modeling, simulation and development of the prosthetic mechanism. The system is modeled using the powerful technique of bond graphs. Effects such as extensibility of actuation strings and their internal damping, bearing friction at joints, etc., which are encountered in the prosthetic system, have been modeled and simulated. A simple prototype has been developed based on the proposed concept and demonstrated the effectiveness of the design. The prosthesis is very affordable and simple, and holds great promise for persons with such prehensile disabilities.

A planning method for linear object manipulation including knotting/raveling in the three-dimensional space is proposed. Firstly, topological states of a linear object are represented as finite permutations of crossing points including the crossing type of each crossing point. Secondly, transitions among the topological states are defined. They correspond to operations that change the number of crossing points or crossing point permutation. Then, we can generate possible sequences of crossing state transitions, that is, possible manipulation processes from an initial state to a given objective state. Thirdly, a method for determination of grasping points and their moving direction is proposed in order to realize derived manipulation processes. Furthermore, criteria for evaluation of manipulation processes are introduced in order to reduce the candidates of manipulation plans. Finally, it is demonstrated that our developed system based on the above method can generate manipulation plans for raveling from an overhand knot.

It is interesting to study the phenomenon of contact interaction with an object and its manipulation using prosthetic mechanism proposed earlier by the authors. The task is made challenging due to the presence of soft fingertips, and the combined action of sliding and rolling at the contact interface. Detailed bond graph modeling of the contact phenomenon for one and two degrees of freedom of the prosthesis is presented. Effects due to softness of the fingertips while manipulating an object, extensibility of actuation strings and their internal damping, bearing friction at joints, etc., which are encountered in the prosthetic system, are modeled.

We will develop a manipulator system that can handle randomly located, moving parts. Vision algorithm to detect the planar motion of a part is implemented on an FPGA-based realtime vision system. Trajectory of a manipulator is replanned in realtime according to the detected location of a part. We will present the control architecture and will show experimental results,.

A vision-based approach to the motion control of pneumatic group actuators is presented. Sensing of plate locations consisting of the pneumatic group actuator is essential to cope with the variation of elastic tubes of the actuator. Plate locations are measured by a vision system and the motion of the actuator is controlled using a roughly identified relationship between air pressure imposed on individual tubes and the plate locations. Proposed motion control is evaluated experimentally.

An approach to the separation of multiple stacked cards is presented. Separation of multiple stacked cards is a key operation in many mechatronic devices such as copy machines and cash dispensers. Separation must be performed in small operation area despite water and oil on the cards. We develop a system to separate multiple stacked cards using an array of absorptive holes. First, we show the principle of the separation of multiple stacked cards. Second, we develop a prototype card separation system using an array of absorptive holes. Next, we show experimental results of card separation and evaluate the performance of the prototype. Finally, we analyze the separating process of stacked cards in a quasi-static manner to determine appropriate absorptive pressure.

A approach to forming control using a forming process model of rheological food dough is presented. Manipulative operations of rheological objects can be found in many industrial fields such as the food industry and the medical product industry. For example, automatic operations of rheological objects such as food dough are eagerly required in food industry. Since food dough deforms during operation processes, it is necessary to estimate their deformation for the automatic operations. We propose a forming control of rheological food dough using a forming process model. First, an extensional forming system of food dough is developed. Second, we examine the deformations of actual food dough. Third, we propose a forming process model consisting of the expansion, part and the residual part. Finally, we propose forming control using forming process model and demonstrate the validity of the proposed forming control experimentally.

In this article, we develop parallel processing of one-sided Radon transform for the detection of the position and orientation of a planar motion object. Detection of planar motion based on one-sided Radon transform can be applied to arbitrary shapes and is robust against overlapping of objects, but it requires much computation time. Thus, we construct a parallel computation of one-sided Radon transform to reduce the computation time. The developed parallel algorithm is evaluated by comparing it with the original algorithm.

In this paper, we calibrate Mirtich's approach (1996) for computing a collision impulse by two kinds of randomized algorithms, and then apply the model for an air hockey game. Mirtich proposed a smart dynamic simulation called impulse-based simulation. He considers twin goals of physical accuracy and computational efficiency. The simulation can accurately model complex dynamic system in real-time. However, whether his impulse-based model is reasonable or not has not been investigated at all by any experimental result. For example, his impulse model requires the dynamic friction coefficient /spl mu//sub D/ and the coefficient e of restitution in advance. However, they strongly depend on shape and material of colliding objects. Because of noise and error of sensing, it is difficult for us to measure the parameters exactly. For this reason, in this paper, we calibrate these by using two kinds of randomized algorithms based on many reductions of momentums before and after the collision. Each momentum (multiplying mass and velocity) can be easily obtained by measuring relative linear velocities and angular velocities before and after the collision. They are practically and easily measured by a smart imaging of two objects. The air hockey game designed consists of two PC with two joysticks including force feedback, which are connecting each other by the fast Ethernet.

We develop pneumatic actuators composed of multiple elastic tubes. Elastic tubes with mechanical constraints have the capability of performing a single various motion while multiple motions cannot be performed. Actuators composed of single-motion tubes can realize multiple motions by controlling air pressure imposed on individual tubes. We present the concept of group actuators and develop their prototypes.

Manipulative operations of rheological objects can be found in many industrial fields such as food industry and medical product industry. Automatic operations of rheological objects are eagerly required in these fields. In this paper, we realize a vision-based automatic forming of rheological objects using deformation transition graphs. First, we develop a forming machine of rheological objects with multi-degrees of freedom. Next, we analyze the forming processes of rheological objects. Then we introduce a deformation transition graph so that the forming processes can be described in a systematic manner. Finally, we propose a forming control method of a rheological object based on the deformation transition graph.

A new approach to the detection of the position and the orientation of planar motion objects based on one-sided Radon transform is presented. Detection of position and orientation of planar motion objects is a key to advanced object handling. First, one-sided Radon transform is introduced and its properties are investigated. Next, algorithms to detect planar motion of objects are constructed based on the properties of one-sided Radon transform. The algorithms are then implemented on a computer and are evaluated experimentally.

Robust manipulation strategies of deformable objects is presented. Manipulation of deformable objects can be found in many fields such as the garment industry and food industry. Guidance of multiple points on a deformable object is a primitive operation in the manipulation of deformable objects. In this guidance, the points often cannot be manipulated directly. A model of the manipulated deformable object is needed in order to perform these operations. It is, however, difficult to build a precise model of a deformable object. Thus, we need a robust control scheme that allows us to realize the operations successfully despite discrepancy between a manipulated deformable object and its model. We firstly derive a mathematical model of deformable objects for their manipulation. Second, indirect simultaneous positioning operations of deformable objects are formulated. Then, we propose a PID feedback control law with the rough object model to realize the manipulation. Furthermore, we propose a simple PID feedback control law without deformation model. The validity and the robustness of the proposed manipulation method is shown through simulation results.

Manipulative operations of rheological objects can be found in many industrial fields such as food industry and medical product industry. Automatic operations of theological objects are eagerly required in these fields. In this paper, deformation transition graphs are proposed for the forming operations of rheological objects. First, a novel forming machine with multi degrees of freedom is developed for the automatic forming of rheological objects such as dough and paste. Second, we will introduce a deformation transition graph so that the forming process can be described. We will then develop a method to generate the deformation transition graph through experiments. Finally, we will explain a forming control method of a rheological object based on the deformation transition graph.

Behavior of deformable cylindrical actuators is qualitatively investigated with respect to constraint topology. Elastic shells expanded by air pressure have a capability of generating various motion directly by imposing mechanical constraints on the shells. In this paper, we propose a qualitative analysis of the motion of deformable cylindrical actuators with mechanical constraints.

A systematic approach to the modeling of deformable rodlike objects is presented. Various rodlike objects such as cords and wires are manipulated in many manufacturing processes. In such processes, it is important for successful manipulation to evaluate their shapes on a computer in advance because their shapes can be changed easily and their deformation often shows hysteresis properties. In this paper, we develop an analytical method to model the shape of deformable rodlike objects including hysteresis properties. First, we investigate the mechanism of hysteresis. Second, the potential energy of a rodlike object and the geometric constraints imposed on it are formulated. The shape of the object can be derived by minimizing the potential energy under the geometric constraints. Thirdly, a procedure to compute the shape of a deformed rodlike object is developed by applying a non-linear programming technique. Finally, we show some numerical examples with hysteresis using our proposed method.

A new object sorting device using impulsive manipulation and air floating is developed. First, two methods for impulsive object sorting are evaluated using computer simulation for the design of a sorting device. Second, an object sorting system with air floating is developed. Finally, the developed system is evaluated experimentally.

Since viscoelastic objects deform during operation processes, it is necessary to simulate the behavior of the objects and to estimate their deformation for the automatic operations. Consequently, a model of a viscoelastic object is needed for the simulation and the estimation of its deformation. We propose a lattice structure based modeling method for viscoelastic object deformation. First, the behavior of four element models is briefly explained. Next, a viscoelastic object is modeled as a lattice structure, where mass points are connected through four element models. We simulate shape deformation of the model when force input is applied to it. Validity of the model is then discussed. We also introduce a nonlinear damper (NLD) into a four element model in order to solve a discrepancy between an actual viscoelastic object and its linear model. By comparing the behavior of the two models, we show the validity of the model using NLDs.

A control method for positioning operations of deformable objects is presented. In many manipulative operations of deformable objects, it is required to guide multiple points on on object simultaneously. Moreover, the points often cannot be manipulated directly. A model of the manipulated deformable object is essential to perform these operations. It is, however, difficult to build a precise model of a deformable object. Thus, we need a new control scheme that allows us to perform the operations successfully despite of discrepancy between a manipulated deformable object and its model. We introduce a coarse model of a deformable object and develop a control law for its positioning operation. First, we propose a mathematical model of deformable objects for their positioning operations. Second, indirect simultaneous positioning operations of deformable objects is formulated. Then, we propose an iterative control method to realize a given positioning operation. The validity of the proposed method and the effect of model errors on the operation are examined through experiments using textile fabrics. Experimental results show that coarse model of deformable objects is effective for their positioning operations. Finally, we discuss the locations of robotic fingers, which apply forces to a manipulated object.

A novel control method for the indirect simultaneous positioning operation of soft deformable objects will be proposed. In some operations, multiple points on a deformable object should be positioned to desired regions simultaneously. In addition, these positioned points often cannot be operated directly and we have to perform these operations indirectly by controlling other points. We call these operations indirect simultaneous positioning operations. First, a simplified physical model of deformable textile fabrics is developed for their positioning operations. Second, the indirect simultaneous positioning operations are formulated using the proposed model. Based on the linearized model of the deformable objects, we will propose a novel control method for the indirect simultaneous positioning operations with visual sensors. In this method, positioned points can be guided to the desired locations by controlling the positions of operation points. It should be noted that our control method works well even if exact physical properties of fabrics cannot be given. Experimental results will show the validity of our proposed method. In addition, a condition to examine whether a given operation is feasible or not will be considered based on the linearized model.

A new approach to the modeling of plain knitted fabrics is presented for their deformation control. There exist many manipulative operations that deal with deformable soft objects such as clothes, papers, wires etc. At present, most of these operations are still done manually by skilled workers. Therefore, it is important to automate this process, especially the process of knitted fabrics manipulation in the garment industries. However, automatic handling of knitted fabrics is difficult to perform by machines since the knitted fabrics are often deformed and extended during the operations. Furthermore, it is difficult to control the shape of the knitted fabrics. In order to control the deformation of knitted fabrics, a physical model of the fabrics is essential. In this paper, we present a physical model of plain knitted fabrics. Firstly, the structure of plain knitted fabrics is explained. Secondly, the behavior of cross points of a plain knitted fabric is investigated experimentally. Then, a physical model of the fabrics is developed based on the iterative structure of the fabrics. Model parameters are selected considering the behavior of the cross points. Finally, the validity of the proposed model is examined by comparing computed shape of a fabric with its real image.

A human-demonstration based approach to the recognition of process state transitions in the insertion of a deformable tube is presented. First, human demonstration of the insertion of a deformable hose into a rigid plug is measured by use of a position sensor and a force sensor. Secondly, the measurements are analyzed with regard to the process states during the insertion. Human recognition laws to detect process state transitions from force sensation are then extracted through the analysis of human demonstration. Finally, human motion during the insertion is transplanted to a mechanical manipulator to examine whether the human recognition laws are useful or not for the insertion performed by mechanical manipulators.

A static analysis of deformable object grasping based on bounded force closure is presented. There are many manipulative operations that deal with deformable objects in manufacturing processes. Manipulative operations for these objects are often performed by utilizing their deformation actively while the operations may result in failure because of unexpected deformation of the objects during the manipulation process. In order to perform the manipulative operations for deformable objects successfully, it is necessary to evaluate their deformation by building object models and to derive task strategies by analyzing manipulation processes using the object models. In this paper, we will analyze stable grasping of deformable objects based on the concept of bounded force closure. Firstly, we will introduce the concept of bounded force closure, which is an extension of force closure condition. Secondly, we will investigate the necessary condition for bounded force closure in order to derive the properties of bounded force closure grasping. Thirdly, we will formulate the deformation of linear objects as an example of deformable objects and we will propose a procedure to evaluate stability of deformable object grasping. Finally, some numerical examples will be shown in order to demonstrate the effectiveness of our proposed method.

One approach to the learning of admittance matrix elements in, damping control is presented. It is difficult to determine admittance matrix elements analytically since they depend upon many physical properties, which are not identified easily, of manipulated objects. We propose a method to obtain admittance matrix elements through iterative trials of a manipulative operation. First, mating processes are kinematically analyzed and conditions for admittance matrix elements are derived based on modifiability analysis. Second, reaction forces during a mating process are investigated and a function to evaluate the process is defined. A learning algorithm, is then, developed based on nonlinear programming techniques. The developed algorithm is applied to a mating operation in a computer simulation. Finally, an experimental result is shown to demonstrate the validity of the proposed method.

One approach to the transplantation of human skilful motion to a manipulator is presented. First, human motion during the insertion of a deformable hose into a plug is measured by use of a position sensor and a force sensor. The measurements are then analyzed with regard to the contact between the hose and the plug. It is found that an alternating motion during the process is effective on the successful insertion of a deformable hose into a plug. Next, human motion is embedded in a manipulator program directly. It turns out that the manipulator can perform the insertion successfully as far as the positional error of the hose is involved in a certain range. Finally, it is shown that refining human motion helps a manipulator perform the operation more quickly.

Various deformable objects are manipulated in many manufacturing processes. Deformation of these objects is often utilized in order to manipulate them successfully while the manipulation sometimes fails because of unexpected deformation of the objects. Modeling of deformable objects is thus required so that the shape of the objects can be evaluated on a computer in advance. In this paper, we develop an analytical method to model the shape of a deformable linear object such as cords and tubes. First, a geometric representation to describe the shape of a linear object with bending and torsional deformation is introduced. The potential energy of the object and the geometric constraints imposed on it are then formulated. The shape of the object in the stable state can be derived by minimizing the potential energy under the geometric constraints. Next, procedure to compute the deformed shape is developed by applying a nonlinear programming technique. Finally, some numerical examples are shown in order to demonstrate how deformed shapes of linear objects are computed using the proposed approach.

Various deformable parts such as cords, leather products, and sheet metals are manipulated and are handled in many manufacturing processes. Deformation of these parts is often utilized in order to manipulate them successfully while the manipulation sometimes fails because of unexpected deformation of the parts. Modeling of deformable objects is thus required so that the shape of the soft parts can be analyzed and evaluated on a computer. In this paper, we develop an analytical method to model the shape of a deformable object. Especially, we deal with deformation of a bendable thin object. The process of manipulating a deformable object is analyzed with regard to how the object interacts with other objects around it. The model of a bendable thin object is formulated according to the principle that the potential energy of the object reaches the minimum at its stable shape. An algorithm to compute the deformed shape of the object is developed by applying a nonlinear programming technique. Finally, a simple experiment is done to demonstrate the validity of the modeling method proposed in this paper.>

The estimation of contact states by using force information acquired in the mating process is discussed, and a method for generating the state classifiers based on geometric models of workpieces on a computer is developed. A symbolic representation of contact states is addressed. Static behavior of workpieces at each contact state is analyzed by applying the theory of polyhedral convex cones. State classifiers that discriminate contact states are formulated by using the polyhedral convex cones, which directly provide a set of discriminant functions. To reduce real-time computations, the classifiers are simplified to a minimum set by using reduction rules of polyhedral convex cones. The algorithm to generate the state classifiers was implemented on a computer. An experiment to identify the current contact state from the measured reaction force is described to demonstrate the usefulness of the approach.>

A model-based approach to the generation of damping control law for part-mating is presented. Partmating operation must be achieved despite positioning errors of workpieces. Applying d amping control, a robot can m odify its motion according to reaction forces acting on it in order to achieve the operations. A modification matrix, which characterize the d amping control law, depends upon t he operation to be done. Few research has been, however, studied about the derivation of modification matrices suitable for operations. Thus, a method to derive modification matrices from the geometric model of workpieces is developed. First, the process of part-mating operation is modeled as a set of transitions of contact states. Second, static property at each contact state is analyzed. Desired motion set is then formulated in order to derive conditions for modification matrices that reduce the positioning error between workpieces. These conditions can be solved by applying the theory of polyhedral convex cones.