Design of a robust H∞ PID control for industrial manipulators

Industrial manipulators are under various limitations against high quality motion control; for example, both frictional and dynamic disturbances should be dealt with a simple PID control structure. A robust linear PID motion controller, called the reference error feedback (REF), is proposed, which solves the nonlinear L-2-gain attenuation control problem for robotic manipulators. The stability, robustness, and performance tuning of the proposed controller are analyzed. Making use of the fact that the single parameter of the induced L-2-gain gamma controls the performance with stability attained, we propose a simple and stable method of performance tuning called the square law. The analytical results are verified through experiments of a six-degrees-of-freedom industrial manipulator. [S0022-0434(00)00104-0].