Shunji Shimizu

A tactile display for presenting quality of materials by changing the temperature of skin surface

Tactile information processing was studied based on psychophysical experiments in order to design a tactile display for tele-existence robots or virtual reality devices. First, the identification characteristics of the tactile sensing concerned with the quality of materials were investigated when human fingertips touched the surface of various materials in a vertical direction. In addition to obtaining the tactile characteristics, the temperature change of the skin surface of a fingertip was measured when the fingertip contacted the surface of materials. From these experimental results, the temperature difference from the normal skin temperature was found to be very important to recognize what kind of materials contacted the skin surface. Next, the tactile display for presenting the quality of materials was designed on the basis of the above experimental results. The tactile display system was composed of a Peltier module and a PID controller.<<ETX>>

Application of hydrogen absorbing alloys to medical and rehabilitation equipment

As power sources for rehabilitation equipment, electric, hydraulic, and pneumatic actuators have been used. However a more human-sized and higher powered actuator that can reduce the equipment size is desired. A new metal hydride (MH) actuator that uses the reversible reaction between the heat energy and mechanical energy of a hydrogen absorbing alloy has recently attracted much attention. The MH actuator is characterized by its small size, low weight, noiseless operation and a compliance similar to that of the human elbow joint. Therefore, the MH actuator has the characteristic of being light and easy to use and so is suitable for use in medical and rehabilitation applications. Some lifting devices using this actuator have already been developed and are being used for the care of the aged and disabled. The characteristics of the MH actuator are presented and then some applications are introduced in this paper. It is our opinion that in our aging society the MH actuator will play an important role in the development of medical and rehabilitation equipment.

Proposal of a new method for narrowing and moving the stimulated region of cochlear implants: animal experiment and numerical analysis

The authors have proposed the tripolar electrode stimulation method (TESM) for narrowing the stimulation region and continuously moving the stimulation site for cochlear implants. The TESM stimulates the auditory nerve array using three adjacent electrodes which are selected among the electrodes of an electrode array within the lymphatic fluid. Current is emitted from each of the two lateral electrodes and received by the central electrode. The current received by the central electrode is made equal to the sum of the currents emitted from the lateral electrodes. Here, the authors evaluate whether or not TESM works according to a theory which is based on numerical analysis using an electrical equivalent circuit model of the auditory nerve fibers. In this simulation, the sums of the excited model fibers are compared to the compound action potentials (CAPs) which the authors obtained through animal experiments. To identify the main parameter while maintaining the amplitude of the CAP (the sum of the fired fibers), the authors assumed the presence of some parameters from the radial current density profile. In the case of the width value among the parameters being kept constant, the amplitude of the CAP was almost constant; thus, the number of the fired fibers was also almost constant. The width value equals the distance between the points at which the profile of the radial current density of the electrode array and the line of the radial threshold current density of the electrode array intersect. It is possible to determine the measure of the stimulation region or site by controlling the width value and the ratios of the currents emitted from the lateral electrodes. As a result, the authors succeeded in narrowing the stimulation region by controlling the sum of the currents emitted from the two lateral electrodes. Also they succeeded in continuously moving the stimulation site by modifying the currents emitted from the two lateral electrodes.

A basic study of a force display using a metal hydride actuator

A new method of a force display is proposed for presenting the sense of force to an elbow joint using a metal hydride (MH) actuator to be used in artificial reality and tele-existence robot. An MH actuator is very suitable for the force display because it works smoothly without any noise. In addition, the actuator is compact, light weight, and it has an adequate compliance. From simple tests, it was found that the actuator could raise a load of 10 kg up to a height of 50 mm at a speed of 9 mm/sec using a 6 g MH alloy. A force display made by the MH actuator was attached to a human elbow joint and two psychophysical experiments were carried out to investigate whether or not the actuator is useful for the force display to create an artificial reality.<<ETX>>

A basic study on the tactile display for tele-presence

Tactile informtion processing was studied based on psychophysical experiments in order to design the tactile display for tele-existence robots or virtual reality. The characteristics of the tactile sense were obtained when strain forces with various velocities and directions were applied horizontally on a fingertip surface. The absolute thresholds of the contactor displacement were measured as functions of the contactor temperature, roughness and viscosity. From the experimental results, it was found that the minimum threshold was 32 degrees centigrade. The display method of the tactile information was discussed from the viewpoint of the physical parameters which determine the sensation of the material quality.<<ETX>>

A new method of variable compliance for a force display system using a metal hydride actuator

A new method of a force display with variable compliances is proposed to give the force sense to an elbow joint using a metal hydride (MH) actuator for the sensory displays for artificial reality and tele-existence robots. An MH actuator is very suitable for the force display because it works smoothly without any noise, and it is compact, light weight and has adequate compliance. From the experimental results, it was proved that the force display system using MH actuators which were attached to a human elbow by using an orthosis could produce variable compliance by changing the hydride pressure inside the MH actuators simultaneously. In addition, the compliance was able to be smoothly controlled by a computer. It was shown that the subject could receive the force sense information with a realistic feeling.<<ETX>>