We have developed a contraction and expansion-type artificial muscle by using the plasticized polyvinyl chloride (PVC) gel and mesh electrodes. The PVC gel artificial muscle exhibits a fast response in air, large deformation, variable stiffness, high output force and low power consumption under an electrical field, so it has a great potential to use as a new type of artificial muscles. In a previous study, we designed variable stiffness spats for walking assistance by incorporating the variable stiffness PVC gel artificial muscles with the generally used spats. The spats can assist walking by the generation force of the variation of stiffness with the on and off switching of an electric field. It was found that both the integrated electromyogram (IEMG) and maximal voluntary contraction (%MVC) of the rectus femoris muscle decreased during the walking when wearing the variable stiffness gel spats which showed that it was possible to use the PVC gel artificial muscles for walking assistance. However, the variable stiffness spats has small generation force and lower robustness to external forces. In this study, we propose a novel approach to make a high-performance light-weight walking assist wear using the PVC gel artificial muscles. We use the contraction-expansion output force for motion assist to get a bigger generation force. An expansion type structure unit is introduced to make the assist wear more robust to external forces. Insole force sensors are used to detect the gait changes during walking. The proposed walking assist wear has the characteristics of a simple structure, light weight, easy to put on and take off and with a high flexibility. In this paper, the framework involving the proposed walking assist wear is described in detail.

In a previous study we developed an expansion and contraction actuator using PVC gel. We investigated the characteristics of the PVC gel actuator and found that its stiffness changed noticeably with a variation in the applied DC field. In this study, we designed new variable stiffness spats for walking assistance by incorporating the variable stiffness PVC gel actuator in generally used spats. The stiffness of the spats can be varied with the on and off switching of an electric field. We believe that the spats can assist walking by restraining and releasing body motion with different stiffness while walking, and conducted experiments to evaluate their effectiveness. It was found that the integrated electromyogram (IEMG) and maximal voluntary contraction (%MVC) of the rectus femoris muscle decreased during walking when wearing them which indicated that the gel spats designed in this study were effective in assisting walking.

To investigate the effects of a car interface robot that behaves like a fellow passenger, we examined the effectiveness of the robot from the view point of psychology, physiology, and driving operations by using a driving simulator. We asked impressions of the driving to the participants after the driving experiments with the fellow passenger robot. Also we measured the car speed, acceleration and steering angle and so on during the driving experiments. The results of questionnaires showed that the driving became more pleasant and cheerful due to the fellow passenger robot. Average speed in the driving experiments with the fellow passenger robot was slower than that without the robot. Therefore, the fellow passenger robot seems to improve the driver's pleasantness and the driving safety.

A new synchronization-based control is proposed for a robotic suit which is designed for walking assistance. Neural oscillators are connected to each joint of the robotic suit to synchronize suit's movement with human user's movement (outer-synchronization). At the same time, mutual inhibition is incorporated between neural oscillators at each left and right joint of the suit to help to maintain a human-gait-like anti-phase relationship (inner-inhibition). We have developed a 2-DOF robotic suit, which consists of two actuators fixed to the places where the human hip joints are. Each actuator has a built-in torque sensor, which helps to measure the mutual joint torque generated by once there is any difference between the movement of a user and that of the suit. The mutual joint torque is used as input to neural oscillators, which control each actuator of the robotic suit through outer-synchronization with the mutual joint torque and inner-inhibition. The inhibitory weight, used to adjust the inhibitory strength between neural oscillators, is designed properly using series of simulations. We have conducted walking experiments to show the validity of our proposal for walking assistance of the robotic suit with mutual inhibition between neural oscillators.

In this paper we propose a framework for synchronization based control (SBC) using neural oscillators for motion assist. A neural oscillator is used to accomplish synchronization and entrainment between periodic motions by the human and robot. The mutual joint torque between the human and robot is used as an external input signal for the neural oscillator, which generates the desired trajectory of a robot joint angle, so that the robot motion synchronizes with the external mutual joint torque. The validity and feasibility of the proposed method is examined from three points of view. The first is whether synchronization of action between human and robot can be realized. The second is whether the assist effect can be obtained, and the third is whether the proposed method has an acceptable level of usability for the user. We explored those three points of view by conducting computer simulations on a human-motion assist system and experiments with a joint torque sensing robot suit.

A poly vinyl chloride (PVC) gel actuator shows great potential for use as an artificial muscle because of such positive characteristics as movement in the air, large deformation, and being lightweight. A bending type actuator using PVC gel was studied previously [4]-[6]. We have proposed the structure of a contraction type actuator to construct an artificial muscle, and we have conducted some experiments using the single-layer PVC gel actuator [8]. In this paper, we investigate the characteristics of the multi-layer PVC gel actuator experimentally and evaluate its specifications in terms of the composition of PVC gel and the structure of the mesh electrode. The experimental results showed that the contraction rate of the actuator was about 14%, the response rate was 7Hz, and the output force was 4kPa. Also, we found that the stiffness of the actuator increased as the applied dc field increased like human muscle. The characteristics of the PVC gel actuator are shown to be very effective for constructing an artificial muscle.

Human-robot communication is an important subject for housekeeping, elderly care and entertainment robots. To make a natural communication entrainment between human and robot, emotion plays a vital role. From this view point we have developed a KANSEI communication system based on emotional synchronization. The robotic emotion was entrained to human emotion by using a vector field of dynamics, and then the robot made a facial expression to express the robot emotion. In this paper we investigate the effect of the emotional synchronization in human-robot KANSEI communications. We conducted experiments to evaluate the effects of the proposed system based on emotional synchronization. In the experiments of human-robot interaction using the emotional synchronization, we found that human feeling became comfortable when the robot made the synchronized facial expression to human emotion. Then it was confirmed that emotional synchronization in human-robot interaction could be effective to keep a comfortable state.

Human-robot communication is an important subject for housekeeping, elderly care and entertainment robots. To make a natural communication entrainment between human and robot emotions plays a vital role. From this view point we propose to make a KANSEI communication system based on emotional synchronization. We developed a robotic KANSEI communication system using entrainment of dynamics, and its effectiveness was examined by experiments of human-robot communication. The robotic emotion was entrained to human emotion by using a vector field of dynamics. The robotic facial expression using a communication robot ldquoKamin_FA1rdquo was realized dynamically based on the robotic emotion. In the experiment of communication, the human impression was changed by the strength of synchronization of robot. Then we confirmed that this method could utilize human-robot communication to keep a comfortable state.

This paper describes gaze guidance with emotional motion of a head robot, called Kamin-FA1. We propose to use not only the gaze control of the robot but also the facial expression combining with the head motion to guide a human beingpsilas gaze to the target. We provide the information of the gaze target intuitively to human based on the shared attention with the emotional communication robot Kamin-FA1. The robot has a facial expression function using a curved surface display. We examined the effect of emotional expression to the gaze guidance in terms of the reliability and the reaction speed. We conducted the experiments of gaze measurement during the gaze guidance with emotional expression to evaluate the role of emotional expression. The results of the gaze guidance experiments showed that the gaze guidance with emotional expression caused more reliable and quick eye movement than that without emotional expression. Specially, the expression of surprise has the best performance in the gaze guidance among the six basic emotions.

When robots communicate with humans, expressions play an important role. This paper explains the design and prototyping of a facial expression robot which imitates human's muscular structures. The feature of this robot is to create expressions based on a human being's muscular structure. It is composed of three structures (the skin, the muscle, and the frame). The facial expression is generated with the contraction of the robotic muscle. The robotic muscle consists of a motor, wires and a urethane sponge. The robotic muscles are controlled based on human's muscle activities to make natural facial expressions

In this study we propose a framework using neural oscillators for human-robot physical interaction such as “handshaking”. Neural oscillators are used for synchronization and entrainment between human and robot motions. Passiveness of the handshake can be changed by adjusting strength of the synchronization. Joint torque information is taken as an input signal for the neural oscillators, and the neural oscillator generates the desired trajectory of a robot joint. This paper addresses a model structure of the neural oscillator for human-robot physical interaction. The computer simulations of handshaking show the synchronization and the entrainment. Also the experiments with a joint torque sensing robot arm show that a handshake between a robot and a human being is realized by the proposed method. Lastly the validity of the proposed method is examined by a psychological evaluation with a paired comparison method, and it is found that the proposed method is better than conventional impedance control in terms of “Flexible”, “Natural”, “Kind” and “Affinity”.

Ultrasonically activated scalpels are used clinically to provide hemostatic cutting in endoscopic surgery. To assist the physician during endoscopic surgery, we have developed an ultrasonically activated bending scalpel constructed of super elasticity alloy (SEA in short). We analyzed the vibration characteristics of the probe in the bending state by the finite element method. And the proposed active bending mechanism is prototyped. Moreover the vibration characteristics were measured to examine its effectiveness. Also, a cutting experiment was conducted. We demonstrate that ultrasonic vibration of the proposed scalpel is possible using a conventional vibration controller, since the change of the natural frequency due to the bend is negligible. In the prototyping, we realized the bending mechanism by using a linkage. The range of the bending angles varies from 0/spl deg/ to 60/spl deg/.

This paper proposes a method of robotic facial expressions using a curved surface display. A robot's face image is displayed on the curved surface screen. By using this method we can make a facial expression easily compared with other methods of mechanical facial expression. Also there is a three-dimensional effect caused by the curved surface, which is not in a plane image. We develop a face robot with a curved surface display, which is composed of a dome screen, a fish-eye lens and a projector. Also the face robot has a neck mechanism to move the head. This paper describes a composition of a dome display, a compensation of distorted image, a drawing method of shadow images with detecting a direction of a light source. The animation of facial expression and the motion using the neck mechanism are performed, and the effectiveness of the system is examined.

Manipulation of deformable objects is an important subject for housekeeping and care robots. Dynamic manipulation of a string is studied in this paper as an example of deformable objects. The string is modeled by a rigid body link with passive joints in two-dimensional space. The parameters of the joint stiffness and viscosity of the string model are identified experimentally using a high-speed video camera. The desired trajectory of the manipulator is searched by using the optimal control method. The manipulator is controlled with the desired trajectory to manipulate the string. In this paper many experiments of flinging-up motion are conducted using two-link and three-link models of the string. The experimental results show the validity of the proposed method.

In this paper, we propose a winding control technique using a physical index of horizontal constraint force for a 3D snake-like robot, and it is shown that a winding motion of the robot can be realized with small joint torque. If it approaches a target point, it is necessary to raise the head and to work like a manipulator. Therefore, a control method of the head configuration using a criterion function, which can be used in both redundant and insufficient number of link cases is proposed. In order to show the validity of the proposed methods, we constructed a snake like robot called SMA. Using the experimental system, we show that the winding pattern with which the robot can avoid singular postures is generated automatically, and head position and head orientation can be controlled properly.

Ultrasonically activated scalpels are used clinically to provide hemostatic cutting in endoscopic surgery. To assist the physician during endoscopic surgery, we developed an ultrasonically activated bending scalpel constructed of super elasticity alloy (SEA). First, we performed the vibration analysis and its verification in bending state of ultrasonically activated scalpel. The results show that longitudinal vibration was transmitted even if probe was bent. The influence of transverse vibration is very small. There is no trouble destroying tissue contacts with the probe. Next, a SEA bending probe and its bending angle control system were manufactured as an experiment. From the experiment using chicken, we evaluated the validity of the bending scalpel.

In our previous works (2000), we have proposed "virtual passive dynamic walking" utilizing modified gravity condition with virtual gravity field. The virtual passive walking motion critically depends on the physical parameters and the steady walking pattern is not easily obtained without suitable physical parameters. In this paper we propose a more generalized method of virtual passive walk and a virtual passivity mimicking control law. With the effect of the control laws, we can generate the steady walking pattern even if the physical parameters are not suitable. We call the walking pattern generated by the control methods as "extended virtual passive dynamic walking". The validity of the proposed method is examined by numerical simulations and tested by a prototype experimental machine.

We have proposed practical torque sensing which utilizes a flexible part of a harmonic drive gear. The sensing technique provides joint torque sensing without reducing stiffness of the robot and changing the mechanical structure of the joints. The characteristics of the torque sensing have been studied under an immovable condition. The dependence of characteristics on the rotational velocity have not been discussed. We describe the characteristics under rotational conditions of the harmonic drive. The experimental results show that the accuracy of the torque sensing under high velocity rotation is 2% of the gear torque capacity.

Torque sensing built into harmonic drives has advantages in its size and stiffness comparing to the torque sensors added to the robot joints. A relatively high fluctuation signal of a built-in torque sensor is a drawback in its practical applications. However, we present a simple and effective method to compensate the fluctuation signal and thus improve an overall accuracy of the harmonic drive built-in torque sensing. The method does not require precise positioning of the strain gauges, does not require online-estimations of the fluctuation signal, and does not increase the number of applied strain gauges. It requires initial tuning of the gains. For the signals of the separate strain gauges, two techniques to define the gains are presented: one is based on a mathematical model of the fluctuation signal, and the other employs a heuristic approach. Practical results show the effectiveness and usefulness of the proposed method.

Even though a particle model based on the mechanical properties of woven cloth has been proposed by D.E. Breen et al. (1994), there are problems in describing the cloth behavior precisely and in reflecting the cloth dynamics. In this paper, we describe a precise relationship between the measured mechanical properties of cloth and the particle model. Moreover, a collision model describing the rotation as well as the movement of particles resulting from an impulse is integrated into the particle model. Some experiments involving two cloth materials are performed in order to validate the proposed cloth model.

We have developed a forceps system which includes an active mechanism. This forceps is intended to assist the physician during laparoscopic surgery, and is constructed of four shape-memory alloy tubes. The temperature of the Ti-Ni shape-memory alloy is controlled electrically, achieving a fast response. The paper describes the design and the prototyping of the active forceps system.

We developed a force display system for atomic bonding state in material. The force display aims to help scientists make discoveries by improving their perception for the atomic world. This paper describes the overview of the force display system in which we can feel the atomic bonding state with the dynamic force. We propose a control method of the force display device and a decision procedure of the scaling factors between the atomic and human worlds. The validity of the force display device is proved by the virtual experiment of atomic bonding states with various kinds of material.

A mechanical design of a parallel link compliant wrist is described based on the passive compliance analysis. The compliant wrist has a three degrees of freedom parallel link mechanism and provide the necessary flexibility for pick-and-place, grinding and polishing operations. It is shown that using the design method we can construct a compliant wrist which has a desired Cartesian stiffness and a suitable work space. We built a compliant wrist as an example and examined the characteristics.>

The authors propose a joint torque sensing technique making use of the existing structural elasticity of robots. The technique provides joint torque sensing without reducing the stiffness of the robot or changing the mechanical structure of the joints. The elasticity of the flexsplines of the harmonic drives is utilized to measure the joint torque. The flexsplines are flexible thin cups, made from steel, in the harmonic drives that are driven by the wave generators. A finite-element analysis of the flexsplines shows that a special configuration of strain gauges, mounted on the flexspline, has to be employed to eliminate errors in sensor information due to rotation of the wave generator. Characteristics of the torque sensor are examined experimentally. The linearity and the dynamic response are almost the same as those of a conventional sensing technique. For a one-link robot arm, both theoretical and experimental investigations support the validity of the sensing technique.>

The authors have proposed a torque sensor which utilizes elasticity of harmonic drives. The characteristics of joint torque control were experimentally examined using this torque sensor. Three types of torque control laws were implemented with a one-link arm to find a control method which provides excellent friction reduction and dynamic response in joint torque. The experimental results of the joint torque control showed that the torque sensor was very useful for compensating for the nonlinear friction. The torque control was effective in improving the accuracy of motion control at low velocity and suppressed the vibration caused by the joint flexibility.>

In, th.k paper, tue propose (1 practiccil m,otio.n eon,trol sch,eme for- industrial robots th,iit is effective for the compensation of the nonlinear dynumic coupling and suppression oj the vihration due to joint jlezibility. The con.trol system is hased on, th,e 3oin.t torque sensky and its jeedback con,troI. Th,e joint torque is measured hy a huilt-in torque sensor with. u haymonic drive. Th.e ch,aracteristics of the proposed control is examined by the numer-ical simulations and e3:per.iments using a one-lint robot arm,. The simulated und experimented results show the validity of the pr-uposed control meth.od to industl.%al mbots.

When positive feedback of joint torques is applied to the motion control of robot arms, the nonlinear dynamic couplings between links are canceled and a servo system with high stiffness is obtained. The problems which arise due to joint flexibility in robot motion control based on joint torque positive feedback are discussed. The effects of joint flexibility are investigated by numerical and experimental studies on a one-link arm with a harmonic drive. It is shown that the joint flexibility destabilizes the control system with joint torque positive feedback. A low-pass filter is used in the torque feedback loop to improve the oscillation characteristics of the control scheme.>

A joint torque sensing technique for robots with harmonic drives is proposed. Elasticity of harmonic drives is utilized to measure the joint torque. The technique provides joint torque sensing without reducing the stiffness of the robot and changing the mechanical structure of the joints. A finite-element analysis of flexsplines, which are flexible thin cups made from steel in harmonic drives, is performed. The analysis shows that a special configuration of strain gauges on the flexspline has to be employed to eliminate errors in sensor information due to rotations of wave generators. Characteristics of the torque sensor are examined experimentally. The linearity and the dynamic response are almost the same as those of a conventional sensing technique. Both theoretical and experimental investigations support the validity of the proposed sensing technique.>

The author proposes a joint-torque feedback (JTF) control scheme with a conventional position compensator for robot motion control. The advantage of this control scheme is that real-time computation is not required for the dynamic compensation. Also, the control system is robust against unexpected external disturbances, such as the action of gravity on objects picked up and put down, and other interactions with the environment. The author discusses the modeling and analysis of the JTF control and proposes a joint-torque sensing technique using the elasticity of the harmonic drive. The JTF control system worked well and insulated the conventional PD control loop from dynamic interventions in experiments with a two-link robot arm.>