Improvement of Measurement and Control Scheme on Human Body Motion Interface

This research focuses on the electric wheelchair controlled by Human Body Motion Interface (HBMI). HBMI uses the body motion which is caused by the voluntary movement. From our previous research, it has been confirmed that HBMI, which uses the center of weight on the pressure sensor attached on the backrest, has the ability of an interface. However the problem has also remained. The velocities of each wheel have been determined in proportion to the difference between initial and present position of the center of weight. This difference is generated by the inclination of the body. In some cases, while user leans his/her upper body, the difference doesn't increase due to the contact condition between body and backrest. In this case, the user cannot control the wheelchair arbitrarily in spite of leaning his/her body. For this problem, the gain which is proportion parameter between difference of center of weight and velocity of each wheel should be increased. However, too big gain lets the wheelchair cannot keep a stop. In order to solve this problem, first, we consider extracting user's stop intention by using self-organizing map (SOM). Second, we eliminate constant pressure data on the backrest when calculating the center of weight. By these operations, the wheelchair can keep a stop while the user wants to keep a stop, and the velocities of each wheel are generated even if the difference of center of weight is small.