A basic study for a robotic transfer aid system using a high power MH actuator

In this paper, some experiments concerning the human motion pattern were carried out and the results were evaluated from a viewpoint of biomedical engineering in order to obtain the optimal parameters for the transfer aid. Sagittal plane kinematics, surface electromyographic signals (EMG) obtained from lower limbs, ground reaction forces and foot pressure distribution were measured using a 3 dimensional motion analyzer. From the experimental results, it was found that the motion of the transfer aid was smoothly moved when an initial angle of the ankle was 70/spl deg/. The initial angle of the trunk was also found to be the best about at 45/spl deg/ while standing from a bed. The initial angle of trunk was the best at 60/spl deg/ while sitting down to the wheelchair. Furthermore, a knee pad which supports the lower limbs needs the flexibility in the range from 0.1 to 0.2 kgf/mm. From the above results, some parameters for the design of the transfer aid system were determined. In our transfer aid, a high power MH actuator was adopted since the actuator can smoothly move the transfer arm. The MH actuator uses the reversible reaction between heat energy and mechanical energy of a hydrogen absorbing alloy. Therefore, the MH actuator works smoothly without any noise. Moreover, the actuator is compact, light, and has an adequate compliance.