Shuichi Ino

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>>

Objective method to determine the contribution of the great toe to standing balance and preliminary observations of age-related effects

The purpose of this study was to examine the relationship between toe pressure and tactile sensitivity in the great toe and to describe two newly developed measurements of postural stability. The subjects of the study were 21 healthy volunteers. The subjects were divided into two age groups, the young group (mean 21.0 +/- 1.6 years, 7 males and 6 females), and the elderly group (mean 71.4 +/- 2.8 years, 4 males and 4 females). The methods and materials used for the first experiment (balance test): The instrument for measuring standing balance was a force plate. Data were analyzed to provide two main variables: 1) body sway index (SI: mm) and 2) toe pressure (%BW/cm2). The subjects were asked to stand in a relaxed posture for 20 s. The variables of body sway were measured in four conditions: normal surface with eyes open or closed, and soft surface with eyes open or closed. Second experiment (tactile sense test): This experiment utilized a new system which was developed for measuring the tactile sensation. The tactile threshold value was measured with the subject seated in a chair, the back supported, and the hips and knees flexed at 90 degrees. The contactor pulled and pushed the toe longitudinally along its axis at a constant velocity of 1 mm/s. There were significant differences between the young and elderly groups in the tactile sense of the great toe (p < .001). No significant difference between age groups was found for postural sway while the subjects stood on the normal surface with eyes open; however, when they stood on the soft surface with their eyes open and closed, the elderly showed significantly more sway (p < 0.01) than the young. Moreover, the maximal great toe pressure in the elderly group was significantly greater than that in the young group. The results suggest that the reduced tactile sense, deprivation of visual information, and toe pressure weakness are all important factors associated with postural instability.

The influence of moving auditory stimuli on standing balance in healthy young adults and the elderly

The maintenance of postural balance depends on effective and efficient feedback from various sensory inputs. The importance of auditory inputs in this respect is not, as yet, fully understood. The purpose of this study was to analyse how the moving auditory stimuli could affect the standing balance in healthy adults of different ages. The participants of the study were 12 healthy volunteers, who were divided into two age categories: the young group (mean = 21.9 years) and the elderly group (mean = 68.9 years). The instrument used for evaluation of standing balance was a force plate for measuring body sway parameters. The toe pressure was measured using the F-scan Tactile Sensor System. The moving auditory stimulus produced a white-noise sound and binaural cue using the Beachtron Affordable 3D Audio system. The moving auditory stimulus conditions were employed by having the sound come from the right to left or vice versa at the height of the participants ears. Participants were asked to stand on the force plate in the Romberg position for 20 s with either eyes opened or eyes closed for analysing the effect of visual input. Simultaneously, all participants tried to remain in the standing position with and without auditory stimulation that the participants heard from the headphone. In addition, the variables of body sway were measured under four conditions for analysing the effect of decreased tactile sensation of toes and feet soles: standing on the normal surface (NS) or soft surface (SS) with and without auditory stimulation. The participants were asked to stand in a total of eight conditions. The results showed that the lateral body sway of the elderly group was more influenced than that of the young group by the lateral moving auditory stimulation. The analysis of toe pressure indicated that all participants used their left feet more than their right feet to maintain balance. Moreover, the elderly had the tendency to be stabilized mainly by use of their heels. The young group were mainly stabilized by the toes of their feet. The results suggest that the elderly may need a more appropriate stimulus of tactile and auditory sense as a feedback system than the young for maintaining and control of their standing postures.

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.

A basic study for a robotic transfer aid system based on human motion analysis

A metal hydride (MH) actuator uses the reversible reaction between heat energy and mechanical energy of a hydrogen-absorbing alloy and moves smoothly without any noise. Moreover, the actuator is compact, light and has adequate compliance. In this paper, some experiments concerning human motion patterns were carried out in order to adopt the MH actuator to the transfer aid system. The results were evaluated from a biomedical engineering viewpoint in order to obtain the optimal parameters for transferring the disabled from a bed to a wheelchair and vice versa (transfer aid). Sagittal plane kinematics, surface electromyographic signals (EMG) obtained from lower limbs, ground reaction forces and foot pressure distribution were measured using a three-dimensional motion analyzer. From the experimental results, it was found that the motion of the transfer aid was smooth when the initial angle of the ankle was 70°. The best initial angle of the trunk was also found to be about 45° while standing from a bed. However, the initial angle of the trunk was best at 60° when a person was in the process of sitting down on a wheelchair. Furthermore, a knee pad which supports the lower limbs requires flexibility in the range of 0.1-0.2 kgf/mm.

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>>

Proposal of a new tactile display method of speech signals as a nonverbal communication for the profoundly hearing impaired

We have designed a fingertip tactile vocoder which has a 16/spl times/4 vibrator matrix for the deaf. In order to investigate whether or not sweeping display method is useful for recognizing Japanese consonants, vibratory patterns corresponding to the speech spectrum of monosyllables were swept from right to left on a fingertip surface using 4 columns of the vibrator matrix at fixed speeds. The best sweeping velocity was estimated to be 10 cm/sec from the experimental results of the absolute threshold, the two-point threshold and the identification rate of monosyllables. The sweeping display method was shown to overcome the problems such as temporal masking for the consonants, especially for the plosives.<<ETX>>

A proposal to correct depth perception of virtual objects by using tactile feedback

Mixed reality (MR) is a technique which can combine a virtual environment and a real environment without making users feel that anything is unnatural. We propose a method using a see-through head mounted display (STHMD) to improve the precision of depth perception using tactile feedback. The visual accuracy of depth perception was measured when virtual objects were displayed through a STHMD. Subjects perceived the real objects to be closer to them than the virtual objects. The reason for this may be due to the optical characteristics of the HMD. We then manipulated our fingers while watching virtual objects through the STHMD. After decreasing the visual depth gap, we measured how accurately subjects moved their fingers to the exact location where the virtual objects appeared. From the results, it was found that there were depth gaps between our fingers and the virtual objects. Finally, vibratory tactile feedback was presented to the fingertip when the finger was near the virtual object. We measured how accurately subjects moved their fingers to the virtual objects. There was a range where subjects did not perceive the gap between their fingers and the virtual objects when tactile feedback was presented. The reason for this improvement was the integration between visual and tactile information. Accordingly, by controlling the degree of perceptual error through various tactile feedback, we assume that the precision of depth perception would improve. From the above results, we have proposed that using visual and tactile integration is one method that could solve the problem of inaccurate virtual objects depth perception.

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>>