Wearable robots suffer from issues of usability, cost-performance, and battery life. These drawbacks hinder the development of their market and their implementation in healthcare and industry. Back support exoskeletons in particular rely heavily on mechanical storing of energy but are still mostly using traditional mechanical elements and actuators to achieve the task. The core technology of our work, named MRLink, uses a smart fluid in combination with a compression spring to produce a unique energy store-and-release functionality. With only 5 Watts MRLink can produce over 500N of braking force. The braking force, variable viscosity, can be continuously controlled through the supply current. With appropriate selection of the spring and control method, the required assist energy can be acquired from body weight and movement dynamics, stored momentarily and, released at the appropriate timing to assist the body motion. The MRLink does not require an external power source like pneumatic actuators, does not require gearboxes and large batteries like DC motors, and comes in a compact package. Thus, this technology has the potential to significantly contribute to wearable exoskeletons in general, and back support exoskeletons in particular. In this work we present the development of a back support exoskeleton prototype based on MRLink, we describe its functional details, and a pilot test partially verifying the proposed functions.

In this paper, we study a compact wheeled robot that can jump while rolling. Some robots are capable of jumping or rolling, but as far as we know, those robots are not focused on jumping while rolling. We know that animals jump while running to escape from predators. Robots can move quickly by jumping while rolling. We consider a model of a robot jumping while rolling and evaluate the proposed robot. The proposed robot has two wheels and a jumping mechanism based on snap-through buckling of an elastic strip. The proposed robot can jump about 5.9 cm high and 22 cm wide on average while maintaining a traveling speed of about 1.2 m/s. The proposed robot can change the jumping angle without greatly decreasing the impulse for the moving speed.

This paper proposes a real-time method for estimating the shape of an elastic rod using a robot manipulator equipped with a sense of force. The proposed method does not use optical sensing devices, such as cameras or lasers, but relies only upon the sense of force in the manipulator. In the proposed method, the deformation of an elastic rod is calculated from the obtained force/torque information using the discretized Kirchhoff elastic rod model, and the three-dimensional shape of the rod is then estimated. Furthermore, by integrating the force information with the orientation of the manipulator end-effector, the proposed method can evaluate the effect of gravity on the shape estimation accurately. Experiments were carried out to verify the proposed method, where a thin elastic strip was employed as a typical elastic rod, attached to the end-effector of the robot manipulator, bent and twisted into various shapes. The results show that the proposed method that compensates for gravity is better than a method without gravity compensation, and it estimated the 142 mm length strip shape with a position error no greater than 7.76 mm and an average calculation time of 4.24 ms.

In this paper, we propose a real-time spatial shape estimation method for an elastic rod. Our proposed method does not use any image sensor nor shape sensor, but does use a six-axis force/torque sensor placed near one end of the elastic rod. In the proposed shape estimation method, the occlusion problem never occurs principally because the shape of a flexible object will be estimated based on an elastic rod model. We utilize the discretized Kirchhoff elastic rod for shape estimation, which can be viewed as a serial chain of rigid bodies connected with three-degree-of-freedom rotational spring joints. We show that real-time spatial shape estimation is possible based on real-time sensing of force/torque information. The computational time of the proposed shape estimation algorithm is linear in the number of rigid-body partition. Moreover, the required calculations are very simple owing to deep understanding of robot manipulator kinematics. Thus we can compute the spatial rod shape in realtime. We show experimental results in order to validate our proposed method.

In this paper, we proposed a model for a wire-driven continuum manipulator without assuming constancy in curvatures of the manipulator's shape as a natural extension of the famous and useful constant curvature model. We show that the tip orientation of the continuum manipulator can be decided completely by pulling-wire lengths, regardless of its whole shape, which is a useful property same as the constant curvature model. Moreover, we can derive the tip position, which depends on the whole shape, by assuming distributed forces along wires mainly due to the friction between the wires and their surrounding materials. Experimental validation results show that, based on the model, we can estimate the tip orientation from pulling-wire lengths with good accuracy and precision. We also provide experimental results for discussion about estimating the tip position with the realistic assumption on the force distribution along wires.

A closed elastica, which is an elastic rod whose both ends are fixed to prescribed two places, can be found in various situations in robotics. In this paper, we investigate validity of the discretized spatial model of a closed elastica. The discretized closed elastica model can be regarded as a series of rigid bodies connected with passive elastic joints physically, and represented by a set of nonlinear equations derived by discretizing differential equations with boundary conditions as well as Euler equations expressing local minimum elastic energy. The validity of the considered model was studied by comparing the measured shape and the calculated shape from the model. Experimental results using a laser position sensor for shape measurement show that good correspondence between measured and calculated shapes, which supports the validity of the considered model. The constrained force and torque at the tip of an elastica, which can be obtained simultaneously associated with shape calculation, are also verified from measurement by a 6-axes force/torque sensor.

In this paper, we investigate the property of an impulse force generator based on snap-through buckling of a robotic closed elastic rod which is considered as one of good examples of continuum robots. The impulse force generator considered here utilizes a snap through buckling of an elastic rod where its base end is pinned and driven by a rotary actuator forcibly while the tip end is pinned or clamped to the fixed point. One of the most fundamental design problems is to maximize the released elastic energy at each buckling state subject to limited ranges of driving torque and angle of a given actuator. From this design viewpoint, we show two findings obtained from quasi-static planar shape transition simulation of the closed elastica, which will be useful for a design of the robot, that is, the ratio of the elastica length and the endpoint distance decides 1) the buckling angle which relates to the range of an actuator driving angle, and 2) the released elastic energy per the maximum driving torque. We also provide a mathematical description of snap-through buckling based on which we can measure a distance to a buckling point.

In this paper, we propose a novel closed loop elastic structure which can generate snap-through buckling with bending and distortion. The proposed mechanical closed loop structure consists of two rotary shafts and a belt-shaped elastic material which two ends are connected to one active rotary shaft and one free joint type shaft, respectively. Driving the active rotary shaft continuously, we can obtain impulsive motion by using snap-through buckling repeatedly. The change of the driving torque and the angular momentum generated snap-through buckling are shown by numerical simulations. From these results, it is shown that an offset parameter of the proposed structure is useful for generating impulsive turning motions of the compact swimming robot. The proposed mechanism is applied to a compact swimming robot which can turn impulsively at a maximum rate of 135 deg/s underwater.

In this paper, we propose a shooting manipulation system for manipulating a distant object in an instant. The proposed system mechanistically acts on a remote target by constraining an end-effector catapulted by an impulsive air flow through a flexible string connected with an elastic cantilever. Experimental results shows that the proposed shooting manipulation system has excellent basic performances such as high motion straightness of a reaching path, quickness in a turning motion, and high reaching accuracy in spite of its simplicity. Furthermore, we show that, by making full use of the basic performances of the proposed system, it is possible to realize a quick capturing of a falling object 0.7[m] away with a high success rate of 92 percents.

In this video, we propose the robotic jerboa which is a compact bipedal kick-and-slide robot powered by unidirectional impulse force generators. The robotic jerboa moves fast not only running forward but also turning right and left by kicking and sliding on the ground repeatedly. The robotic jerboa kicks toward the direction which the horizontal component is large by its legs in order to jump forward effectively. The robotic jerboa is composed as its legs are protruded out of the side of its body respectively for realization of the quick turning. We show that the palm-top size robotic jerboa whose weight is of only 70[g] achieves the velocity of 1.5[m/s] and the turning angular velocity of 11.5[rad/s] instantaneously.

In this paper, we propose a robotic catapult based on closed elastica utilizing bending and twisting deformation of an elastic strip. By using snap-through buckling generated from not only bend but also twist of thin rectangle elastic strip, impulsive forces can be generated repeatedly by the frequency of 3[Hz] without changing added torque directions. The compact jumping robot based on the proposed robotic catapult can leap over 950[mm] away. In addition, by setting the parameters appropriately to make the best use of generating impulsive forces with high frequency, it can perform repeated low-altitude jumping motions with about 1.06[m/s] velocity including quick step of about 0.152[s].

In this paper, we propose a compact kick-and-bounce mobile robot powered by unidirectional impulse force generators. The unidirectional impulse force generator is a simple mechanical device for generating high-frequency impulse forces toward a certain direction unilaterally utilizing snap-through bucklings. The proposed kick-and-bounce robot has a pair of the unidirectional impulse force generators as the muscles of its biped legs. The robot moves forward rapidly by the repetition of the kicks and bounces to the ground. We show that the developed palm-top mobile robot whose weight is of only 67 [g] achieves the velocity of 0.8 [m/s] instantaneously.

In this paper, we propose a novel macro-micro tele-manipulation system based on body image embedding with contact feel, spatial motion and stereo vision for micro-manipulation under a microscope. The basic concept of body image embedding for macro-micro tele-manipulation has been already proposed by the authors. The system proposed here has three new realization ideas. The first idea is the realization of realistic contact feeling which is attained by driving a voice coil motor according to the binary on/off information of the switch between micro-tools. The use of a voice coil motor not only saves the cost of the system, but also generates clearer tactile and auditory stimuli than a piezo actuator for sending contact information in a micro world to an operator. The switch between micro-tools does not detect the contact between the object to be manipulated and the tool for manipulation directly, but can be useful for some tasks. The second idea is the realization of spatial motion of the manipulation tool relative to the object to be manipulated, which is realized by the appropriate coordination of the 2-degree-of-freedom motions of the slave manipulators. The third idea is the realization of stereo vision under the constraint of the position/orientation consistency of an operator's body image between proprioception and vision, which is achieved by the special placement of the dual joysticks of the dual micro-manipulators. The effectiveness of the proposed realization method is verified experimentally by micro-drawing tasks where we need appropriate hybrid position/force control of the micro-tool for manipulation in a three-dimensional space.

In this paper, we propose a new asymmetric robotic catapult based on the closed elastica. The conventional robotic catapults based on the closed elastica which the authors developed are the robotic elements for generating impulsive motions by utilizing a snap-through buckling. In a typical closed elastica, the two ends of an elastic strip are fixed to a passive rotational joint and an active rotational joint, respectively. Here we found that by adding only a range limitation to the passive rotational joint, compared to the conventional type, the deforming shape of the elastic strip becomes more complicated and 40% more elastic energy can be stored. Using this modification, we can develop a compact jumping robot which is able to leap over 700[mm] away and 200[mm] high.

In this paper, we propose a new robotic catapult with a high stiffness endpoint. The conventional robotic catapults based on the closed elastica are robotic elements for generating impulsive motions by utilizing the snap-through buckling. In a typical robotic catapult, the two ends of an elastic strip are fixed to a free joint and an active joint, respectively. Here we found that by adding only the high stiffness at the free joint, compared to the conventional type, more elastic energy can be stored and release surely without loss of a characteristic of generating impulsive motion repeatedly. By utilizing the high stiffness endpoint, we develop a faster impulsive swimming robot than the conventional one.

In this paper, we propose a novel robotic catapult for generating repeated impulsive motions which are considered as a key to achieve creature-like motions by a compact autonomous robot. The proposed robotic catapult is just a bended elastic strip whose two ends are fixed to two rotational joints, i.e., a mechanical closed-loop of an elastic material named the ‘closed elastica’. By only driving one joint back and forth gradually, we can obtain repeated impulsive motions of the elastic strip. It is shown that this robotic catapult can be applied to some robotic tasks such as impulsive robotic swimming and fly casting manipulation.

Two types of robotic catapults based on the closed elastica are proposed as robotic elements for generating impulsive motions. To obtain impulsive motions, these catapults utilize the snap-through buckling of an elastic material induced by applying driving torques to the ends of the elastic strip. In this paper, we show the effectiveness of the various types of the robotic catapults based on the kinematics and statics of a serialchain approximation model. The numerical simulations show that these catapults can increase the elastic energy necessary for impulsive motions even if the driving torques decrease.

This paper proposes a method to improve the operability of micro-macro tele-operations in biological researches and developments. In such fields, there are lots of labor intensive works and the smooth execution of the works requires some trained human skills. Thus, if we can improve the operability of the equipments, the efficiency of the researches and developments will be improved remarkably. The idea is to add a pseudo haptic feedback and artificial responding sounds beside the real magnified image. The image itself has enough information to operate, but adding other sensory information may ease the operation. Naturally, the real magnified haptic feedback must be helpful, but its realization is not so easy. Even pseudo or artificial sensory feedback may help enough to improve the operability. As a start of our research, this paper shows a simple experiment to ensure the effectiveness of adding the other sensory feedback.

Modeling of friction force is cumbersome because of its discontinuity at zero velocity. This paper presents a set of discrete-time friction models for the purpose of haptic rendering and virtual environment construction. These models allow friction to be treated as an admittance-type or impedance-type element of a virtual environment. They are derived from implicit Euler integration of Coulomb-like discontinuous friction and linear mass-spring-damper dynamics, and have closed-form expressions. They include rate-dependent friction laws, and their extension to multidimensional cases is easy in most practical cases. The validity of the models is demonstrated through numerical examples and implementation experiments

Friction force is cumbersome in numerical simulations due to its discontinuity at zero velocity. Fixed-step simulation techniques are especially desirable for control purposes, such as haptic friction rendering and friction compensation. Previous techniques have difficulties especially in numerical robustness and extensibility to multidimensional cases. This paper proposes two discrete-time friction models that can be used in fixed-step simulations. They can be used in multidimensional space, and can capture arbitrary velocity-dependent friction phenomena. The first one is a discrete-time discontinuous model. This model determines the friction force so that the velocity reaches zero in finite time by using the values of the mass and the timestep size. The second one is a discrete-time continuous model, which is a serial coupling of the discontinuous model and a linear viscoelastic element. This model is useful for haptic rendering because it is formulated as a velocity-input, force-output system. The second model can be extended into a more sophisticated friction model, which exhibits a hysteresis behavior in the presliding regime. Results of numerical simulations and an experiment are presented.

Human-machine cooperative systems have been proposed. Most of them consider carrying, positioning and assembling tasks. Precise tracking tasks are also required in factories. However, an assist system for tracking task has not been studied well. In this paper, we aim to realize the human-machine system that assists a tracking task. In order to achieve the goal, the virtual friction field is proposed. Isotropic and anisotropic friction fields are presented and they are applied to the rotating object which should be tracked. The tracking task experiments are carried out and it is shown that the virtual guide of the friction improves the tracking performance effectively.

This paper introduces a device for enhancing detection of surface undulation through active touch. This device, which we call a “tactile contact lens,” is composed of a sheet and numerous pins arranged on one side of the sheet. Experimental results show that a small bump on a surface can be detected more accurately through this device than by bare finger and than through a flat sheet. A mathematical analysis of this phenomenon suggests two possible explanations for this phenomenon. One lies in the lever-like behavior of the pins. The pins convert the local inclination of the object surface into the tangential displacement of the skin surface. The second is the spatial aliasing effect resulting from the discrete contact. Due to this effect, the temporal change in the skin surface displacement is efficiently transduced into the temporal change in the skin tissue strain. The results of this analysis are then discussed in relation to other sensitivity-enhancing materials, tactile sensing mechanisms, and tactile/haptic display devices.

A Hyper-Flexible Manipulator (HFM, for short) is a kind of continuum robots with a simple mechanical structure like a cable, rope and string, which are useful tools utilized everywhere in various forms. In this paper, in order to achieve dexterous and useful manipulation by this type of robot, we discuss kinematics and dynamics of an HFM. We rigorously derive a spatial, nonlinear and continuum dynamics model with an underactuated mechanism using special kinematics based on curve geometry and theory of robot manipulation.

In this paper, we propose a mechanical impedance for the whole arm of a serial-chain manipulator. The proposed impedance has a geometrically natural property owing to use of a spatial curve which describes a virtual reference of the impedance. The proposed impedance is useful for geometric task planning in whole-arm manipulation. Illustrative examples are shown for understanding of the impedance.

In this paper, task space control for the whole arm of a serial-chain manipulator is considered. The task space for the whole arm is interpreted in two ways, the space of rolled shapes or bunches of ordered n-frames. A rolled shape is a set of restricted points with rolling angles of links, and gives us intuitive viewpoint of the space. To represent the rolls of links, the concept of the canonical manipulator is introduced. A bunch of n-frames is a collection of frames each of which corresponds to the link orientation of the chain, and allows us to handle the space easily. A rolled spatial curve, which has a roll distribution over the curve, is used for specifying a desired rolled shape of the chain. A method generating the bunch of desired n-frames from a desired rolled curve is proposed. Based on the method, we derive a regulation law in the task space for the whole arm by Lyapunov design. The derived control law is very simple; recursive with respect to the link/joint number, and calculated by geometric operations in three-dimensional Euclidean space.

The shape Jacobian, which is the counterpart of the manipulator Jacobian, plays a key role to control the shape of a manipulator with extraordinarily many degrees of freedom. In this paper, we show some significant properties of the shape Jacobian, the structure, boundedness, determinant and singularity, in geometric aspects.

The kinematic structure of a manipulator with hyper degrees of freedom is discussed from a theoretical viewpoint. Conditions for the kinematic structure are derived from a geometrically natural requirement that its direct kinematics tends to Frenet-Serret formula as its number of degrees of freedom increases. It is shown that the manipulator has to have two-degree-of-freedom joints, each of which consists of a twist and a one-directional bend.

In this paper, we give a definition of a shape correspondence between a manipulator with hyper degrees of freedom and a spatial curve. The shape correspondence is defined by using the solution of a nonlinear optimization problem, termed the shape inverse problem. We also provide results on the existence and a well-posed region of the solution.

In this paper, a shape tracking control problem for a hyper degrees of freedom manipulator is discussed. The objective of shape tracking is to control its shape, which is characterized by all the joints and the tip positions, to follow a given time-varying curve. Crucial key to solve this problem is to introduce a 2nd-order estimator that infers the curve parameters corresponding to the target positions of the joints and the tip on the curve. The coupled dynamics of the manipulator and this estimator has the same properties as the manipulator dynamics which is useful for control design purposes. Therefore, familiar design methods for manipulator trading can be utilized to solve the shape tracking problem. Examples are shown to illustrate how to find shape tracking laws by two famous methods, that is, the ID (inverse dynamics)-based and Lyapunov-based method.

In this paper, a new shape control law is proposed to bring a serial rigid link manipulator with hyper degrees of freedom into a specified shape. Shape control is one of the most characteristic controls for a hyper degrees of freedom manipulator. This control law is derived by the Lyapunov design method. A homogeneously decentralized control scheme is also proposed for practical application of the control law to a hyper degrees of freedom manipulator, and it is shown that the derived control law can be realized in a homogeneously decentralized control scheme. The effectiveness of this control law is verified by a hardware model experiment.