The design of a reference adjustment iterative learning scheme with pre-compensation module for CNC

This paper presents a tracking method in the context of repeating process by combining reference adjustment iterative learning control (ILC) scheme with a repeatability error module that perform the same tasks repeatedly. The general iterative learning algorithm is based on the iterations of controlled variable which may cause saturation. And due to the fact that many kinds of servo drivers are made up of commercial products, the system vendors won't open the interfaces of control signal which improves the difficulty of the iterations. For this, the Adjustment iterative scheme is proposed, but the application of the zero-phase filters in the scheme may cause the loss of useful information when filtering the noise signal and has bad influence on the rate of convergence. This paper proposes a compound ILC scheme with repeatability error module to increase the convergence speed and improve the tracing accurate, and in order to guarantee the effectiveness of the module, adequate processing data should be acquired.