Self-aided manipulator system for bed-ridden patients - Evaluation of psychological influence for the generated approach motion -

Rehabilitation robots that are used to assist patients should be able to move naturally and cause no discomfort to the patients. In this study, a self-aided manipulator system that can generate natural motion and assist bed-ridden patients has been developed. The self-aided manipulator is designed so that it can grasp a glass of water from a side table for the patient. The system can detect the starting position (position of the glass) and the target position (position of the patient´s lips) by using a video camera. The direction angle of the patient´s face is also determined, and approach motions are generated on the basis of these angles. Approach motions are generated by changing the peak velocity time, maximum speed, and detour point position of the manipulator, and the psychological influence on the patient is evaluated on the basis of their heart rate variability (HRV), skin potential response (SPR), and response to questionnaires. The results suggested that a peak velocity time of 75% of the total movement time, a maximum speed of 36 cm/s, and an approach path from the right when the patient´s head is facing straight or to the left tended to have the strongest psychological influence on the patient. From these results, it was indicated that the following conditions are preferable for the approach motion of the manipulator: a peak velocity time of approximately 25 to 50% of the total movement time, a maximum speed from 18 to 24 cm/s, and an approach path in the direction in which the head faces.