Disturbance rejection analysis of multiple impedance control for space free-flying robots

Multiple impedance control (MIC) is an algorithm that enforces designated impedance on all cooperating manipulators, the manipulated object, and the moving base, if applied to a space (or mobile) robotic system. It has been shown that the MIC algorithm can also satisfy force-tracking requirements in object manipulation tasks. In this paper, the disturbance rejection characteristics of this algorithm applied to complicated space free-flying robotic systems is studied. The results of this analysis reveal that the effect of disturbances substantially reduces through appropriate tuning of the controller mass matrix gain. Using MAPLE and MATLAB tools, a system of three manipulators mounted on a space free-flyer with eight D.O.F. is simulated in which a Remote Center Compliance (RCC) is attached to the second end-effector, subjected to force and torque disturbances applied on several points. The simulation results reveal the merits of the MIC algorithm in terms of disturbance rejection characteristics, i.e. negligibly small errors in both position and force tracking in the presence of significant disturbances.