This paper presents a novel gripper capable of actively changing both shape and firmness. The gripper increases its grasp ability by changing its finger posture and firmness suitable for given target objects. In the proposed gripper, each finger is constructed by serially connecting multiple Juzu units. By controlling the angles between neighboring Juzu units individually using two actuators used for sending and bending, arbitrary finger shapes can be generated. In addition, by controlling the tension of the wire that penetrated all Juzu units in each finger, the friction between Juzu units is adjusted and the firmness of finger can be varied. A prototype gripper was designed and developed, and experiments to evaluate the capabilities of changing shape and firmness were conducted. Furthermore, through experiments of preshaping and grasping for various objects with different shape and size, the validity of the proposed method was demonstrated.

This paper presents a novel in-hand rolling manipulation method in which a ball on a cloth attached to fingertips is controlled using flexible and adaptive deformation of the cloth. First, an analytical model of the ball-on-cloth system is introduced. The shape of the cloth is simplified, and the rolling constraint of the ball on the cloth is defined focusing on the lowest point of the ball. Next, the relationship between the input to the cloth anchor point and the position of the lowest point of the ball is expressed by a linear approximation. Then, the input to generate the desired rolling orbit is designed. Next, as an example of utilizing the rolling orbits, a manipulation method to rotate the ball around a vertical axis is developed. Finally, a multi-fingered hand with a piece of cloth attached to the fingertips is developed, and the effectiveness of the proposed system is experimentally verified.

This paper proposes a novel flexible vibrational actuator with a structural anisotropy and its control method to diversify the vibrational behavior. First, the analytical model of the proposed actuator, which comprises a rectangular cross-sectional flexible beam and a rotational-type motor, is introduced. Regarding the structural anisotropy, the rotational axis of the motor is nonparallel to both principal axes of bending stiffness of the beam. Then, the vibrational phenomenon of the actuator is theoretically revealed. It is shown that using the synthetic wave input constituting two sine waves based on the resonance frequencies for the principal axes of the beam, the vibrational orbit of the tip of the beam can be controlled in the same manner as the Lissajous curve. Finally, the proposed method is experimentally validated. The Lissajous curve-based vibrational orbit control is performed using a prototype actuator. Furthermore, an application to underactuated-type locomotor is demonstrated.

This paper discusses a novel task-oriented design method for wire-driven flexible hands. For a monolithic hand fabricated using 3D printing, an analytical design method is proposed to enable it to perform the given tasks. First, the wiring-synergy equation, which relates the parameters of the hand mechanism, the wire tension, and the generated posture is derived based on an analytical model of a hand with wire drive systems. Next, the posture-synergy equation is derived, using principal component analysis for multiple desired postures given to perform a task. Based on the isomorphism of the mathematical structure in the two synergy equations, a method for designing a hand is developed. By quantitatively evaluating the posture reproducibility with respect to the number of wire drive systems, this method can analytically determine the mechanism parameters and wire tension for the desired postures. Subsequently, the proposed method is validated through case studies. Finally, a hand for an in-hand manipulation task is developed, and the feasibility of the proposed method is validated experimentally. The method potentially contributes to expediting the design procedure, increasing the accuracy of the posture reproduction, and reducing the number of actuators.

This paper presents a novel manipulation method utilizing dynamic deformation of a flexible body with a structural anisotropy. Employing a spiral flexible body, a dynamic underactuated manipulation using its various vibrational patterns is proposed. First, the orbit of the tip of flexible body for the vibrational input to its root is theoretically derived. Subsequently, for flexible bodies with and without the structural anisotropy, structural stiffness and vibrational orbit of the tip of body are analyzed. Through this analysis, the generation mechanism of the orbit change effect according to the input frequency is revealed. Finally, the proposed method is experimentally validated. After confirming the orbit change effect in a spiral flexible body, this effect is applied to an underactuated nonprehensile manipulation where three-Dof motion of an object is controlled by a single actuator.

This paper presents a nonprehensile manipulation based on the vibration of a plate, in which three degrees of freedom (DoF) of a planar part are controlled using only one actuator. First, the model of a manipulator with a flat plate end effector is proposed. The manipulator employs an underactuated mechanism including an active joint and multiple passive viscoelastic joints, in which the joint axes are arranged nonparallel to each other. Based on the model, the orbit of the plate for a sinusoidal displacement input to the active joint is theoretically derived. It is revealed that not only the orbital shape but also the orbital direction can be varied according to the input frequency. Based on the switching frequency of the orbital direction, a design index for the mechanical parameters is shown. Subsequently, the contribution of the switching of the orbital direction to the three-DoF manipulation of a part is explored via simulation. Eight primitives utilizing the plate orbital motions in both counter-clockwise and clockwise directions are provided. Finally, the proposed method is demonstrated by experiments.

An image-processing-based method for quantitatively evaluating the state of a food bolus formed via human oral processing is presented. The proposed method consists of the acquisition of the bolus image and the estimation of the mastication class using a convolutional neural network (CNN). The experimental evaluation was conducted using old-fashioned doughnuts. Images of boluses masticated 0-30 times by a subject were acquired, and they were classified into four and seven classes. After preprocessing for input images, the CNN model between the input images and the mastication class was trained. The experimental results showed that the proposed method can approximately estimate the mastication class of bolus by only one local image. In addition, it was indicated that the proposed method has a higher performance in class estimation than human visual observation.

This paper proposes a dexterous nonprehensile manipulation using the vibration of a plate, in which a three-degree-of-freedom (DoF) motion of a part is controlled based on a single actuator. First, a manipulator whose end effector is a flat plate is introduced. The manipulator employs a hybrid joint mechanism with a viscoelasticity and a nonparallel axis layout. The characteristic of the mechanism is that the shape, orientation, and size of the vibrational orbit of the plate vary based on the sinusoidal displacement input to the actuator. Subsequently, the trajectories of multiple point masses on the plate are analyzed to understand the approximated three-DoF motion of a part. The simulation results reveal that the whirlpool-like characteristics of the trajectory map, which aid in the rotational and translational motions of the part, can be managed by the input frequency, offset angle, and amplitude of the sinusoidal displacement input. Based on the trajectory maps, nine primitives for manipulating the part are designed. Finally, the proposed manipulation scheme is experimentally validated using a prototype. After confirming the nine primitives in the experiment, applications to one-DoF, two-DoF, and three-DoF parts feeding tasks are demonstrated.

This paper describes nonprehensile manipulation realized using the vibration of a plate. A novel manipulation strategy is proposed wherein the three degrees-of-freedom (DoF) of a part are controlled by only one actuator. First, a manipulator driven by a single actuator is introduced. The end effector of this manipulator is a flat plate. The manipulator employs an active-passive hybrid joint mechanism with nonparallel axes. Based on the sinusoidal displacement input to the actuator, the manipulator can generate the velocity of a part omnidirectionally on the plate. Next, simulation results are presented to show that the velocity map of the part varies depending upon the surface friction property of the plate. Further, the control of the rotational behavior of the part on the boundary of two areas with different friction properties by means of the input frequency is shown. Based on this control, a 3- DoF manipulation strategy using a virtual turntable is developed to realize the desired position and orientation of the part. Finally, the proposed method is demonstrated via experiments.

This paper proposes a nonprehensile manipulation scheme using the vibration of a plate, where a 3-DoF (degree of freedom) motion of a part is controlled using a single actuator. A manipulator is introduced, the end effector of which is a flat plate. The manipulator employs a hybrid joint mechanism with a twisted axis layout. The characteristic of this mechanism is that the shape of the trajectory of the plate can be varied three dimensionally based on the sinusoidal displacement input to the actuator. The behaviors of multiple point masses on the plate are then analyzed to understand the approximated 3-DoF motion of a part. The results of the simulation reveal that the whirlpool-like characteristics of the trajectory map, which aids in the rotational and translational motions of the part, can be governed. Based on the characteristics, five primitives for manipulating the part are defined and their arrangements for a 3-DoF parts feeding task are shown. Finally, the proposed approach is demonstrated via experiments.

This paper describes an underactuated robot finger whose link posture is controlled by using dynamical effect. The finger posture control method where the vibration center angles of the active joint and the passive one are controlled independently of each other, is proposed. First we introduce the analytical model of two-joint two-link system which has the active joint driven by an actuator and the passive joint with a viscoelastic element. Based on the model, we theoretically reveal Variable Vibration Center Effect (VVCE) of the viscoelastic joint with respect to the input frequency of the active joint. We then discuss how to control the finger link posture by utilizing the effect. We show the finger mechanism design for grasping an object and for expanding the working space. Finally, we experimentally confirm the proposed method and demonstrate a grasping motion by the prototype.

This paper presents a texture evaluation system for nursing-care paste foods with a biomimetic approach. To artificially reproduce human oral processing, an elastic imitation tongue is introduced to the compression test device of paste food. During the compression, the tongue is passively deformed and holds a paste sample. Such a tongue behavior varies with respect to characteristics of paste food. Based on this effect, we propose the method for extracting the cohesiveness of paste food by the pressure distribution measurement and the image processing. Then, we develop the texture evaluation system that estimates the value of human sensory evaluation from the feature value of the pressure distribution. The experimental results show that the proposed method can appropriately estimate the value of human sensory evaluation.

This paper discusses a dynamic nonprehensile manipulation by using a vibrating plate. The manipulation method, where two DOF (degrees of freedom) motion of an object on the plate surface is controlled by a single active joint, is proposed. For the plate vibration mechanism, we newly introduce an active-passive hybrid joint whose two axes are arranged in nonparallel to each other. This mechanism features the plate vibration trajectory is variable based on the input frequency. We then analytically derive the trajectory of object on the vibrating plate. Through this analysis, we reveal that two DOF motion of the object can be controlled by utilizing the variable vibration effect. Finally, we show experimental result by using the prototype robot, for confirming the validity of the proposed method.

This paper discusses a dynamic nonprehensile manipulation of a deformable object, where the shape of a thin object is dynamically controlled by the plate's rapid motion. After explaining the manipulation principle, we introduce a simplified analytical model where an object is modeled by two mass points and the plate has two degrees of freedom: a translational motion and a rotational one. After categorizing jump patterns of the mass point with considering the plate's acceleration, we show that gait-like behaviors of the object are generated on the periodic plate's motion. Through simulation analysis, we show the deformation velocity transition of the object with respect to the amplitude of plate's acceleration. We reveal that the transition is characterized by particular amplitudes which govern the jump patterns of the mass point. We make clear that the optimum plate's motion leading to the maximal deformation velocity exists on one of such particular amplitudes.

We have been studying an omnidirectional driving gear mechanism that can generate thrusting force in an arbitrary direction on one surface, which may be flat or curved. This omnidirectional gear is driven by spur gears that are perpendicular. When one spur gear rotates to drive the omnidirectional gear, the other slides between the teeth of the omnidirectional gear and vice versa. In this paper, we introduce gears with passive rollers to reduce the frictional resistance with a mechanism including smooth rolling motion of conical or flat passive rollers, which can boost the power transmission efficiency of the omnidirectional driving gear system. We also confirmed another useful function of this gear with passive rollers as a worm wheel to transmit power from a worm gear with higher energy efficiency than an ordinary worm wheel.

The finger mechanism equiped with omnidirectional driving roller is shown. The omnidirectional driving roller has two active rotational axes at the touching point. The finger mechanism with this roller can manipulate the grasped object with any arbitrary directional axes. Prototype model has been developed and basic motion of the finger has been confirmed though the experiments.

In this paper, the principles and the actual configurations of the omnidirectional driving gear mechanism that was implemented by the authors were described. The validity of the proposed structure was also confirmed and its basic characteristics understood through experiments using the actual prototypes.

As ordinary dual-axis driving mechanisms in X-Y directions, for example, commercially available X-Y stages with ball screws are familiar. However, such driving mechanisms have two stages, namely both upper and lower linear actuators, the latter of which must generate sufficient thrust to carry large weights, including that of the upper actuator mechanism, which has hampered efforts to achieve suitably fast and smooth driving motion due to the inertial force effect. It is also difficult to achieve a small and slimline driving mechanism with such overlapping two-stage structure. In these ordinary two-stage driving mechanisms, the motion of the X-Y stage can be disturbed by the wires of the upper actuator. In this research, we have considered the abovementioned problems, and propose a new omnidirectional driving gear mechanism that enhances its driving area from the normal X-Y plane to convex and concave curved surfaces respectively, and even various combinations of both. The smoothness of basic omnidirectional motion and effectiveness of the driving method of this proposed omnidirectional driving gear mechanism have been confirmed with several experiments involving our setups.

In this paper, additional manipulating function for limited narrow space with omnidirectional driving gear was described. The validity and advantage of the proposed function was also confirmed through experiments using the actual prototype of the planar omnidirectional driving gear units for the parallel gripper.

A rigid plate end-effector at the tip of a high-speed manipulator can remotely manipulate an object without grasping it. This paper discusses a dynamic nonprehensile manipulation strategy to rotate thin deformable objects on a rigid plate with two degrees of freedom (DOFs). The deformation of the object due to dynamic effects is exploited to produce fast and stable rotation. By varying the frequency of the rotational component of the plate's motion, we show that the dynamic behavior of the object mimics either a sliding, walking, or running gait of a biped. We introduce a model to simulate this type of system in which the object is constructed of multiple nodes that are connected by viscoelastic joint units with three DOFs. The joint's viscoelastic parameters are estimated experimentally in order to model real food. Afterward, simulation analysis is used to investigate how the object's rotational behavior and its angular velocity change with respect to the plate's motion frequency. We show how the object's behavior during rotation is analogous to bipedal sliding, walking, and running gaits and then obtain optimal plate motions leading to the maximal angular velocity of the object. We also reveal that an appropriate angular acceleration of the plate is essential for a dynamically stable and fast object's rotation. We further show that the friction coefficient that maximizes the object's angular velocity depends on its gait.

This paper presents an experimental study of the bio-inspired artificial skin consisting of silicone and embedded strain gages, in which silicone imitates the epidermis and dermis, and strain gages mimic corpuscles. The strain gages are embedded in silicone under different configurations like corpuscle in humans skin. Both static displacement and dynamic excitations are applied in arbitrary positions, with different magnitudes and frequencies. The responses are observed by measuring the output signals from strain gages. Comparison with FEM simulation of static displacement shows intuitive agreement. The responses to dynamic excitation in typical frequency range of human somatosensors are obtained both experimentally and with simulation of dynamic modeling. We found that each configuration has advantages and disadvantages. This paper shows how strain gages embedded in silicone will behave in response to both static and dynamic excitations, and suggests modeling and fundamental concepts to design a bio-inspired artificial skin sensor.

This paper discusses a nonprehensile dynamic manipulation of a deformable object, where the object is remotely manipulated on a plate attached at the tip of a bar. We have found that the object's deformation generated by dynamic effects can drastically contribute to a fast and stable object rotation. We introduce a new simulation model for a sheet-like object, where the object is constructed of multiple nodes connected by three DOFs viscoelastic joint units. We apply the model to real food after the viscoelastic parameters are estimated. Then, simulation analysis is used to show how the object's rotation behavior changes with respect to the plate's motion frequency, similar to the motion of human legs sliding, walking, and running. Finally we obtain an optimum plate motion leading to the maximal angular velocity of the object. We also reveal that an appropriate angular acceleration of the plate is essential for a dynamically stable and fast object rotation.

This paper describes a combination mechanism of a wheeground a paddle to realize an effective movement on the border of ground and water. For the conventional mobile mechanisms on water or on ground the combination of the mechanism to the body of the robot separately, and each one can be the interruption to the other in each field. In this research, we propose a hybrid mechanism of a wheeground a paddle as drive mechanism itself to realize an effective movement on the border such as a coast with debris after a disaster like a seismic sea wave or a tanker grounding accident. A prototype robot has been built and basic experiments on its motion have been conducted.

Non-contact stiffness sensor is often utilized especially for medical fields due to its advantage of avoiding damage to tissues and keeping sanitary. However, it is hard to measure the force accurately, because the fluid jet based force much depends upon the shape after deformation of object. This paper proposes an innovative approach where the external force is adaptively calibrated based on the deformation of object so that we can evaluate the internal stiffness parameters more accurately than that of conventional approaches. It is shown that the proposed method can improve the accuracy of force application with even 100% at an extreme case.

This paper describes a dynamic nonprehensile manipulation of a deformable object, where the shape of a thin rheological object is dynamically controlled by the combination of the inertial force and the frictional one generated by the plate's rapid motion. We first introduce a one-dimensional viscous model to approximate the object deformation characteristics, focusing on the final shape of the object. Assuming that the plate has two degrees of freedom: a translational motion and a rotational one, we derive two sufficient conditions to deform the object: one to enlarge it and the other to contract it. Then, we show the plate's cyclic motion leading to the object's continuous deformation. Finally, simulation and experimental results are shown in order to verify the proposed method.

This paper describes linear load-sensitive continuously variable transmission with the spherical driving unit. This CVT mechanism consists of spherical drive, drive axis, motor housing, fixed bracket and linear sliding plate. It changes the reduction ratio continuously by inclination angle of active rotational axis. Additionally, this linear mechanism has a load-sensitive function by changing inclination of active rotational axis in response to the load. We have developed a linear load-sensitive continuously variable transmission and confirmed the effectiveness of the proposed mechanism.

This paper discusses a shaping strategy of a rheological object whose deformation characteristic includes both elasticity and plasticity. We first introduce a seven-nodes viscoelastic model for approximating the outline and the dynamic characteristics of the object. Then, we show a shaping method of the object's outline, where the ratio between the object's length in the grasping direction and that in the perpendicular one is controlled by using a parallel jaw gripper. Based on the plastic deformation distribution for the integrated input stress, the proposed method can actively manage the final object's outline. In addition to the contribution on simplifying the gripper's degree of freedom, this method has the advantage that the handling time is drastically reduced, compared with the position based passive method. We finally show the experimental results for confirming the validity of the proposed method.

This paper discusses an active shaping method for an unknown rheological object by considering the characteristics of viscoelasticity. By utilizing a four-element model for approximating the dynamic characteristics of object's deformation, we drive the deformation decomposition into the elastic response and the plastic one. For shaping the object, we then propose a two-phase strategy for controlling the resultant deformation; in the first phase the viscoelastic parameters are estimated with avoiding the over deformation, based on the elastic response; in the second phase the desired resultant deformation is generated by actively managing the integral force, based on the plastic response. This strategy has an advance that the handling time of the robot is given by a finite time, while the desired resultant deformation is theoretically completed in the infinite time. We finally show experimental results for confirming the validity of the proposed strategy.

Cell stiffness could be an index for evaluating its activity. Although various systems measuring cell stiffness have been proposed so far, they are slow for adaptively connecting to cell sorters capable of handling more than 1000 [cells/sec]. This paper proposes a new approach that can indirectly evaluate the cell stiffness by measuring the passing time for a narrow channel. When a cell passes through the channel, it receives a viscous force depending upon how much deformation is exerted on the cell. We show that the stiffness is a function of both the passing time and the initial diameter of cell. We also show that the stiffness is proportional to the passing time and inversely proportional to the initial diameter, under the assumption that the thickness of fluid film is inversely proportional to the normal force. The experimental validation is given together with the basic working principle.

We discuss an empirical based design of Active Strobe Imager (ASI) that enables us to visualize the dynamic behavior of tissue, even under a high frequency vibration that cannot be followed by the naked eye. A pneumatic actuator imparts a vibration for the target object. By flashing light with slightly different frequency, we can see the dynamics by the naked eye. We discuss an approach for determining a set of optimal parameters of ASI by considering both the uncomfortability sensation due to light flickering, the sharpness of the motion, and the amplitude of the vibration of the object. We also give an example of optimal parameter determination for human skin.

In this paper, a new category of the wheel-leg hybrid robot is presented. The proposed mechanism can compose large wheel diameter compared with the previous hybrid robot to realize a greater ability to climb obstacles. A prototype model of one Wheel-Leg module of the proposed robot mechanism has been developed to illustrate the concept. Actual design and mode changing experiment with a test mechanical module is also presented. Basic movement tests and a test of the basic properties of the rotational fingertip are also shown. The Basic configurations of wheel-leg retractable is considered well. The integrated mode is also described.

Viscoelastic materials are known to exhibit temporal response that changes force or displacement at the contact interface under position or force control, respectively. In this paper, we conduct experimental study using force control to explore and observe creep phenomenon in robotic grasping in order to better understand the nature of such contact interface, which has been widely used in soft robotic fingers, robotic feet, and contact surface of robotic arms. We found that the creep response under a constant external force exhibits the characteristics of exponentially increasing or decreasing temporal response. Such characteristics are similar in nature to those found in the relaxation response of viscoelastic materials when the grasping is under position control. Two different types of creep responses are found, depending on the state of grasping. Both Types I and II in creep response mirror the Types I and II in relaxation response. We also found that different loading rates under force control result in different elastic response, in addition to the temporal response. This is an interesting finding because the Fung's model postulates for an elastic response that is independent of, and can be separated from, the temporal response. The experimental results do not show such independence.

In this paper, a nonlinear latency model is presented to describe the relationship between the strain and strain rate of the temporal responses in robotic grasping that involves viscoelastic contact interface. The results from experiments and simulation are presented, and are found to match well with each other. The nonlinear latency model was able to adequately represent both Type I and Type II relaxation responses. For the successive loading and holding with a soft contact, the model describes the behavior of step-wise increase of equilibrium strain and a polynomial relationship between the strain rate and the strain. The nonlinear latency model can successfully predict and model the behavior of anthropomorphic soft contact interface in grasping and manipulation when the grasped object is held in certain posture of prehension with repeated loading and/or unloading.

This paper discusses the non-grasp dynamic manipulation of a deformable object inspired by the handling mechanism of pizza master. The master handles a tool where a plate is attached at the tip of a bar, and he remotely manipulates a pizza on the plate. We found that he aggressively utilizes two DOFs (degrees of freedom), such that the linear motion along the bar and the rotational one around the bar, in order to produce quick plate motions for dynamically manipulating the object. Applying this handling mechanism to the robot system, we first show how to rotate an object by using the two DOFs of plate motion. We then reveal that the deformation of the object generated by dynamic effects can drastically contribute to high-speed and stable rotation, just like human steps for turn on the floor. By both simulation and experiment, we show that there exists the optimum plate motion leading to the maximum rotational speed of the object.

For an arbitrary force impartment on tissue, the tissue color changes from red to white due to the decrease of arterial blood. The dynamics leading to (or recovering from) ischemia is a good index for evaluating the vitality of tissue. This paper discusses the ischemia dynamics by using a newly developed active sensing system composed of an air jet nozzle for imparting an air pulse to tissue and a high-speed camera for capturing the change of color of tissue with respect to time. Through experiments, we found that the ischemia dynamics is particularly characterized by the recovery phase where the time constant changes depending upon the local physical condition of tissue. We also showed a map on color changing rate conveniently utilized for quickly understanding the location of ischemia area which is a candidate replaced by regenerated tissue.

The latency model is an analytical model for describing the behavior of nonlinear viscoelastic contact interface in robotic grasping and manipulation. The latency model is based on experimental observation of viscoelastic materials which exhibit the behavior of both elastic and temporal responses when subject to external force or displacement. It is postulated that such materials display latency in response of external influence by the rearrangement of molecules, holes, and structures in order to achieve an equilibrium state corresponding to the instantaneous loading. As a result, we propose that there are temporal latent activities in progress before the material reaches the equilibrium state. In the previous study [21], the latent activity of strain re-distribution with a prescribed constant displacement was presented using both theoretical modeling and experimental results. In this paper, we build upon this latency model to study the behavior of viscoelastic materials under different loading rates with experimental results. The latency model is employed to explain the behavior of responses of hard and soft viscoelastic materials typically found in robotic contact and grasping.

This paper discusses dynamic manipulation inspired by the handling mechanism of a pizza chef. The chef handles a tool called ldquopizza peel,rdquo where a plate is attached at the tip of a bar, and he remotely manipulates a pizza on the plate. We found that he aggressively utilizes only two degrees of freedom (DOFs) from the remote handling location during manipulation: translation along the bar and rotation about the bar. From the viewpoint of a dynamic system, the inertial loads for these specific DOFs are never affected by the length of the bar. This is important for the production of quick plate motions so that the object on the plate can be dynamically and remotely manipulated. Applying this handling mechanism to a robot system, we first reveal how to make the object's motion for three DOFs by using two DOFs of plate motion. We then show that it is guaranteed to achieve an arbitrary desired set of position and orientation of the object by the proposed manipulation scheme. The proposed method has good manipulability because the translational motion of the object can be fully decoupled from the rotational motion (though notviceversa). Finally, we show a couple of experiments that confirm the basic idea.

This paper discusses a dexterous hyper plate inspired by pizza manipulation. We first discuss the necessary combinations of active degrees of freedom of the plate for manipulating an object to arbitrary position and orientation on the plate, under the gravity. While there are nine patterns for choosing two active degrees of freedom of the plate, we show one of them can satisfy a sufficient condition for manipulating the object with the weakest coupling among object’s motions and eventually leads to a simple manipulation scheme. A couple of experiments are shown to confirm the basic idea.

This paper proposes a piercing based grasping by using the self-tightening effect of objects with elasticity. We suppose a piercing hand with palm where the piercing motion by needles can be independently achieved irrespective of the palm motion. The palm first approaches and touches with the object, with a slight pushing motion. This motion produces an increase of potential energy of object. After the motion, the needles pierce the object. When the object is lifted up, the accumulated potential energy is released and the object tries to recover the original shape under the piercing condition. We found a particular mechanical configuration between the object and the needle, under which the constraint of object is tightened due to the object deformation during the release of the potential energy. In order to confirm the robustness of the proposed method, we have done a couple of experiments. The results show that the proposed method keeps an extremely high robustness compared with the other piercing methods.

In this paper, we employ Fung’s viscoelastic model discussed by Tiezzi and Kao to study the experimental data presented by Sakamoto et al. for grasping viscoelastic objects using a parallel-jaw gripper. The viscoelastic contact modeling presented in this paper is characterized by two separate responses: elastic response and temporal response. Two main and intriguing results were found in the modeling and analysis of experimental data. The first is the consistency on the normalized coefficients for the curve fitting of the temporal response during the relaxation period of the grasping. Such consistency suggests that the proposed model is applicable to the grasping task at hand. The other result is the generic pattern of the elastic response deduced from the experimental data. The pattern of elastic response represents different physical significance of grasping which involves viscoelastic contact interface.

This paper proposes dynamic capturing strategies where a 2D stick-shaped object with both translational and rotational velocities is completely stopped by two robotic fingers. We first show the fingertip position and the object orientation for generating a desired velocity of the object under the friction independent collision. Once the object results in a pure translational motion whose direction is perpendicular to the longitudinal axis of object, it is guaranteed that two fingers can always capture the object irrespective of friction coefficient. By using this nature, we show both 2-step and 3-step capturing strategies for a 2D stick-shaped object whose width is negligibly small. The 3-step capturing strategy can guide the object in an arbitrary direction, while the 2-step one can do it only in a particular direction. The 3-step capturing strategy is demonstrated by experiment for verifying our idea.

This paper discusses an optimum design approach for robotic hands by considering the characteristics of visco-elasticity of food. "Norimaki-sushi" is taken as an example for food. We first show that the dynamic characteristics of such food can be expressed by utilizing the Maxwell model with two layers. Based on dynamic parameters obtained by experiments, we show the relationship among the total working time, the plastic deformation of food after the grasping motion, the hand stiffness, and the operating velocity of the hand. We newly found an interesting behavior of food that allows to find an optimum set of the design parameters for achieving the minimum plastic deformation of food.

This paper proposes dynamic capturing strategies where a 2D stick-shaped object with both translational and rotational velocity is completely stopped by two robotic fingers. We first show the fingertip position and the object orientation for generating a desired velocity of the object under the friction independent collision. Once the object results in a pure translational motion whose direction is perpendicular to the longitudinal axis of object, it is guaranteed that two fingers can always capture the object irrespective of friction coefficient. By using this nature, we show both 2-step and 3-step capturing strategies for a 2D stick-shaped object whose width is negligibly small. The 3-step capturing strategy can guide the object in an arbitrary direction, while the 2-step one can do it only in a particular direction. The proposed strategies are demonstrated by experiments for verifying our idea.

This paper discusses jumping pattern generation for a serial link robot in order to maximize its jump height under torque limitation. By applying a genetic algorithm (GA) for determining torque assignment, we obtain various jumping patterns with respect to the torque limitation for a fixed mass of the robot. With the increase of the torque limitation, double-leg based jump, single-leg based jump, and spring-type jump are generated for achieving the largest jump height. Under an additional joint angle limitation, we also obtain an interesting solution where one end of the link is first lifted up and the other end finally kicks the ground strongly

We discuss the optimum design issue for tracing type legged robots in the sense that it can jump as high as possible. By applying dimensional analysis techniques, we introduce four non-dimensional parameters that control the jump ratio(= h/l) for a jumping robot. An interesting observation is that there exists the optimum design point where the jump ratio becomes maximum. Through experiments, we found that the robot with the optimum design specification can achieve the jump ratio of 3.6, while the jump ratio decreases for other design points.

This paper newly proposes the four-fingered robot hand with dual turning mechanism where two and two other fingers can independently rotate inner and outer circles with the common center, respectively. Due to this mechanical configuration, it has the particular rotating axis where the manipulation around the axis can be completely decomposed into the velocity control around the axis and the internal force control in the contact plane. We achieved a manipulation task around the axis with the time of 0.8[sec] for one rotation, while it is relatively slow for another axis.

This paper discusses 2D dynamic preshaping issue for a stick-shaped object changing both position and orientation with respect to time. We propose the two-step grasping strategy where it first stops the rotational motion by choosing an appropriate finger position, and then stops the translational motion step by step for completely making the object stationary. We confirm the basic idea by simulation.

This paper discusses the design of high speed capturing robots based on dynamic preshaping. Focusing on a wire drive robot, we obtain an optimum pulley position so that all finger links can make contact with an object simultaneously. Based on the optimum design, we also develop the hardware so that we can confirm the validity of the optimum pulley position by experiment.

Dynamic preshaping is important for high speed capturing robot to catch a moving object successfully. This paper discusses dynamic preshaping for a capturing robot driven by a single wire. To control the finger posture while approaching an object, there are three essential factors, wiring, spring distribution among joints, and mass distribution in each finger link. Giving the final link posture of finger, mass distribution, and tension with respect to time, we explore hoe to determine both the wiring and the spring distribution. We first show how to find them under a quasi-static motion, where all dynamic effects are neglected. We further explore an approach to find them under a dynamic motion where the tension increases fast enough.

Dynamic preshaping is important especially for a high speed capturing robot to catch a moving object successfully. This paper discusses an issue on dynamic preshaping for a capturing robot driven by a single wire. To control the finger posture while increasing the wire tension, there are three essential factors, wiring, spring distribution among joints, and mass distribution in each finger link. Giving the final link posture of finger, mass distribution, and tension with respect to time, we explore how to determine the spring distribution. We first show how to find it under a quasi-static motion, where all dynamic effects are neglected. We further explore an approach to find it under a dynamic motion where the tension increases fast enough.

This paper discusses the transition stability in sliding an object enveloped by a multi-fingered robot hand whose joints are under constant torque command. We provide a new concept on transition stability, where a transition is called stable if the object is guaranteed to reach the goal section without moving away from a virtual cylinder defined in hand working space. To evaluate the transition stability, we introduce the force-flow-diagram enabling us to confirm whether the object moves to the designated direction or not. By using the diagram, we discuss the transition stability in lifting up an object to the palm under gravitational force. Simulation results show that the transition phase for a column object with concave surface is stable, while that having convex surface tends to be unstable. We also show experimental results to confirm the basic behaviours during the transition phase.

An algorithm for detecting the shape of a 2D concave surface by utilizing a tactile probe is proposed. Pulling a tactile probe whose tip lies on an object's surface can be easily achieved, while pushing it is more difficult due to stick-slip or blocking up with an irregular surface. To cope with the difficulty of pushing motion on a frictional surface, the proposed sensing algorithm makes use of the pulling motion of a tactile probe from a local concave point to an outer direction. The algorithm is composed of three phases, local concave point search, tracing motion planning, and infinite loop escape. The proposed algorithm runs until the tactile probe detects every surface which it can reach and touch. We show some computer simulations and experimental results obtained with the proposed algorithm.