Online reference shaping with end-point position feedback for large acceleration avoidance on manipulator control

A nonlinear reference shaping method for manipulators which are operated in living environments is proposed. It generates an intermediate reference position, and it is combined with a control based on the virtual spring-damper hypothesis proposed by Arimoto et al. The initial acceleration is moderated by an intermediate reference position inserted between the original target and the current position of the manipulator´s endpoint and by a second-order-lag filter. The endpoint position is fed back to the proposed controller to prevent from excessive trailing force and large acceleration. As the result, human-like smooth reaching motions and pliant behaviors against external forces are achieved. The validity of the proposed method is shown through computer simulations on a planar 4-DOF manipulator.