Adaptive closed-loop servo control

Abstract

A closed-loop control of a servo motor in which multiple closed-loop terms of a motor command are adaptively tuned and selectively activated to achieve both stable operation and improved performance. The motor command includes a first term proportional to an error signal, a second term based on the integral of the error signal, and a third term based on the rate of change of the measured feedback signal, and representing the kinetic energy of the system. The first term is continuously active, whereas the second term is only activated when the rate of change of the measured feedback signal is below a threshold, and the third term is only activated when the error signal is within a reference window, thereby allowing relatively high gains while ensuring stable operation. In applications involving an oscillatory load, changes in system response are detected based on variation in the rate of change of the measured feedback signal for purposes of adaptively adjusting the predefined gains and references, thereby eliminating the need to measure various ambient, system or load parameters that affect system performance and stability. Various other features of the control include a technique for reducing stress and energy consumption during anticipated stalling, processing techniques for sampling the feedback signal and identifying background noise, and biasing the system to zero error during static operation.