An impedance function is proposed to achieve accurate force tracking under the presence of uncertainties in robot dynamics and environment models. The new impedance function is formulated on the basis of PID control of the force tracking error which compensates for the unknown environment stiffness and position. The robot dynamics uncertainties are compensated by a simple time-delayed robust control algorithm. Stability and convergence of the control scheme are analyzed. Simulation studies with a three link rotary robot manipulator are shown. Furthermore, experimental results on a PUMA 560 arm are carried out to confirm the proposed impedance controller's performance.
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