Shared compliant control: a stability analysis and experiments

Active compliance providing a damped spring for each Cartesian axis of a robot hand is implemented by low-pass-filtering the outputs of the force/torque sensors mounted on the robot hand and using these signals to alter the position commands. In this implementation, larger compliance needs higher feedback gain, which tends to destabilize the system. A graphical stability analysis based on Bode magnitude and phase plots is used to determine the maximum bandwidth of the low-pass filter for a given desired compliance value. This graphical method enables the stability region to be easily determined. This method is also applied to examine the stability of the shared compliant control in the presence of time delay in the feedback loop. Experimental results obtained from an implemented compliant robot hand agree well with those of the graphical method. The approach can be extended to investigate the stability of the force-reflecting system combined with shared compliant control.>