The Rubber Hand Illusion is a well known multisensory illusion in which the participant feels their own unseen hand become a rubber hand that is placed at the position where their hand is supposedly placed, triggered by synchronized haptic stimuli on their hand and the rubber hand. Our previous study showed that a robotized 1-degree-of-freedom rubber hand in the form of a master-slave system significantly enhanced the illusion compared with the classic rubber hand illusion. The illusion gives the sense that the part of body becomes part of the robot - it is thus assumed that this multisensory illusion is a potentially effective way to increase intuitiveness, and therefore increase the operability of a multi-degrees-of-freedom master-slave system. To further investigate the concept, we built a multisensory illusion inducible microsurgical robotic system based on the findings of the previous study and conducted a series of psychophysical experiments. The experimental results reveal that the multisensory illusion and operability is significantly correlated.

Haptic perception is bidirectionally related to the exploratory movements. This means that exploration influences perception, but also perception influences exploration. We can optimize/change the exploratory movements according to the perception and/or the task, consciously or unconsciously. In this paper, a tactile sensing system including bidirectionality is proposed and its potential and application to laparoscopic surgery are discussed. The proposed system is composed of a tactile sensor and a tactile display. The tactile sensor is mounted on a forceps, and the tactile feedback based on the sensor output is provided by using the tactile display. The user can feel sensor outputs and adjust the forceps manipulation according to the environment and the target. This leads to collect adequate sensor outputs. Implementing the bidirectionality gets the most out of the capability of the tactile sensor. Furthermore, the developed system might have an additional effect due to using the tactile display to the other hand, not to the hand with the forceps. It is an enhancement of haptic perception by tactile feedback to distant part. The developed system is introduced and establishment of the bidirectionality and its effect are discussed. Psychophysical experiments on the enhancing effect are conducted. Experimental results show a potential of the proposed tactile sensing system.

Nowadays, several haptic devices are commercialized and becoming common not only in research fields but also in consumer use. In this paper, a new parallel link mechanism “DELTA-4” is proposed for a new haptic device within high quality force display capability and operability. DELTA-4 consists of 3 DOF of translational motions. The key features of DELTA-4 comparing with conventional parallel link mechanisms are: a redundant actuation, a wide working area and a small footprint. The prototype is equipped with a 3 DOF of rotation mechanism, which its center of motions is located on the wrist position of an operator. An evaluation test of force display was conducted on a prototype of DELTA-4 mechanism.

In this research, a buried suture simulator is developed from attention that there is a most complicated diversity in plastic surgery. Buried suture is one of suture techniques with difficult usage. In comparison with normal suture, buried suture needs more care because it is difficult to handle it. Moreover accuracy of surgical techniques or effect of skill on postoperative deformation are unknown. Furthermore buried suture have two advantages; less mark of wound on cosmetic advantage, and no necessity to thread removal on clinical advantage. Buried suture simulator developed from the two major needs is available in each need. One is manipulation simulator for experience, study and training through manipulation from high difficulty skill. The other is deformation simulator for confirmed postoperative deformation that has an effect on difference of suture pattern from clinical point that is largely-concerned with QOL (quality of life) of a patient. In suture simulator, usually operating time or efficiency and the number of mistakes as typified by failure in gripping an object are the points of the quantitative evaluation. In this research, keeping the evaluation of the postoperative deformation in mind, a suture simulator that can express 3D deformation of wounds and those vicinities is developed. The elemental technologies of the developed simulator are described. Moreover the effect of passing point in suture exerted on the post-operative ligation deformation is considered

Magnetorheological (MR) fluids are substances that respond to an applied magnetic field with a change in their theological behavior. Though they are functionally similar to electrorheological (ER) fluids, MR fluids exhibit much higher yield strengths for the applied magnetic fields than ER fluids for the applied electric fields. The devices using MR fluids have an ability to provide high-torque, low-inertia, a safe device and simple interface. In this study, we report on an actuator developed using the MR fluid, which consists of an input part, an output part and an MR fluid clutch between them. First, the basic experiments are examined to investigate the characteristics of the actuator. Next, the torque control system of the MR-fluid actuator is proposed. Finally, the closed-loop control experiments were carried out and it is confirmed that the torque-feedback control is effective for improving the response properties of MR actuators.

Force information is often required for tele-operation systems and virtual reality. Conventional force displays are active systems with actuators. This, however, is inherently active, so that it may become a danger. Consequently, passive force display is an effective method for assuring safety. The authors developed a brake using ER (electrorheological) fluid and passive force display using ER brakes. They discuss two degree of freedom passive force display and basic control experiments.

ER fluid is a kind of functional fluid. The ER fluids have a unique characteristic, which changes its rheology characteristic to apply the electric fields. The property of the actuator using ER fluid is different from conventional actuators such as DC or AC servomotors. In this study, we developed a new actuator using particle-type ER fluid, which is called ER actuator. The developed actuator can produce two directional torques by using two ER clutches. We derive the simple models of ER actuator from reference torque to output torque and velocity characteristics. Then, we verified the validity of the models and control performance of the actuator by conducting velocity and position control experiments.

In industrial robots, each joint is driven through a reduction gear unit such as a harmonic drive gear. The elasticity of the drive systems cannot be ignored when the high-speed and precise motion control is required for robots. Due to the elasticity of the drive systems, vibratory behaviors are caused, and the control performances of robot systems deteriorate. In this study, we develop a new actuator that consists of an AC servomotor, a harmonic drive gear and an electrorheological (ER) damper. The ER damper can change the damping coefficient by applying an electric field. Since the gap between electrodes of the ER damper is 80 /spl mu/m only the voltage of 160 V is needed for the electric field of 2 kV/mm. The ER damper consumes little electric power. The actuator is installed on a one-link robot arm. The mathematical model of the robot arm is derived, and the eigenvalues of the robot system are analyzed. Experiments were carried out, and the effectiveness of the actuator is confirmed.

Since a direct-drive (DD) motor system does not have the reduction gear, its structure is simple and has stiffness. In the DD motor system, the disturbance torque directly influences the control accuracy. The high servo stiffness is effective and important for reducing the influence of the disturbance torque. However, the high servo control often makes the system vibratory or unstable. Therefore, the servo gain must be lowered for assuring stability, and the influence of the disturbance becomes serious. In this study, the DD motor system using an electro-rheological (ER) fluid damper is developed. By applying the ER damper to the DD motor system, the gain margin of the control system is improved, so it is possible to realize the high servo control. Finally, it is experimentally shown that the proposed system is effective for high-speed and high-precision control.

We developed ER actuators with low inertia. ER actuator is a torque-controllable clutch which uses an electrorheological fluid. It is shown that this actuator has good properties for force display device, physical therapy treatment, etc. Then, we developed new force display devices for virtual reality by using the developed ER actuators.

A semiclosed-loop control which utilizes the signal of an encoder mounted on a servomotor is adopted in the control of industrial robots. In this method, the position of the end-effector is not controlled very accurately. Therefore, we aim to apply a closed-loop control which uses the positional signal measured directly at the end-effector. Because of the flexibility of the driving system, however, it is very difficult to control the arm based on this method. In this study, a robot arm is developed which has a variable damper using an electrorheological fluid (ER fluid). It is shown that the ER damper is very effective for precise position control based on a closed-loop control method.

A variable viscous damper using electrorheological (ER) fluid is developed to suppress torsional vibration of industrial robot. An integrated system consisting of drive motor, harmonic drive, arm linkage and ER damper was measured experimentally and found to be able to reduce the resonance/antiresonance phenomenon by increasing the viscosity of ER damper. A position control system, which is based on both the conventional semi-closed loop control and this new type ER damper, is analyzed and the relation between the ER damping coefficient and the bandwidth of the system is discussed using pole assignment technique. It is shown that the ER damper provides both vibration suppression and disturbance rejection.

The purpose of this study is to realize the bounce gait in articular-joint-type quadruped robots. We first develop a new robot which can realize bounce. A simulator is then made for the purpose of analyzing dynamic walking and efficiently developing its control methods. We formulate the leg-support-exchange phenomenon using Lagrangian impulsive equation. The control method is discussed, and the results of computer simulation are shown. Experimental results are also presented.