Cooperative Motion Control of Multimanipulator Based on Workspace Disturbance Observer with Variable Compliance Gain

This paper proposes a cooperative motion control strategy of multimanipulator based on workspace disturbance observer with variable compliance gain. The workspace disturbance observer as an acceleration controller provides a simple, robust and flexible controller structure and computation while the addition of variable compliance gain will maintain the performance of the system in free motion as well as in contact conditions. It is assumed that the goal of the system is to move the grasped object tracking the desired motion trajectory in the presence of a stiff contact environment with a relatively constant system's performance. To achieve the goal of system, the motion trajectory control of the cooperative control is realized using an impedance control approach enhanced by a variable compliance gain. The compliance gain is considered as a reflexive response against the interaction force which plays an important role in adjusting the stiffness of the cooperative system. The value of this gain increases exponentially with the increasing interaction force to resemble the response of muscle against an external force disturbance. The experimental results show that the use of variable compliance gain has advantages over that of conventional impedance control aproach such as it does not no longer require a switching mechanism to set the system's compliance according to the object motion condition.