A position tracking control of two wheel mobile manipulator using COG trajectory based on zero dynamics

This paper proposes a method for tracking control of underactuated system such as two wheel mobile manipulator based on zero dynamics. This proposal makes it possible to control mobile platform position independently while stabilizing COG and servoing end-effector position, although mobile platform position depends on other control task in conventional methods. Proposed method is based on zero dynamics of the system that describes mobile platform response as the result of COG and end-effector position control. It is revealed that zero dynamics depends on only COG position if it is assumed that COG and end-effector position control is enough quickly controlled compared with mobile platform position. Therefore, proposed method generate COG command trajectory as mobile platform converges to desired position command. In order to make the system stable, COG trajectory is planned as it will converge to zero if mobile platform position converges to its command.