Command-based iterative learning control for compensation of servo lag and friction effects

A command-based iterative learning control (ILC) architecture is proposed to compensate for friction effect and to reduce tracking error caused by servo lag. The proposed methodology utilizes the learning algorithm which updates the input commands based on the tracking errors from the previous machining process. It is shown that, for tracking a circle, the quadrant protrusions caused by friction can be reduced substantially by the updated command containing a concave shape located at the crossing of the zero velocity. Finally, analytical simulation and experimental results demonstrate that the command-based ILC algorithm can enhance the tracking performance significantly