How to design force sensorless power assist robot considering environmental characteristics-position control based or force control based

In this paper, as one of important support for aged people, we present how to design force sensorless power assist robot assisting aged people´s work and caregiver´s motion. The proposed control methods in this paper are based on robust control and consider environmental characteristics because many kinds of environments exist in power assist motions. Two basic power assist methods, position control based and force control based, are compared through some experiments using a DD robot. The proposed position control based method makes use of impedance control. In force control based method, environmental observer is introduced to make robust against environmental parameter change. Both of them can realize stable power assist motion even if environmental characteristic is unknown. Some experimental results show the effectiveness of these methods.