Adaptive Iterative Learning Control for High Precision Motion Systems

Adaptive Iterative Learning Control for High Precision Motion Systems

Rotariu, I.
Steinbuch, M.
Ellenbroek, R.

Mechanical, Maritime and Materials Engineering

Delft Center for Systems and Control

2008-06-30

Iterative learning control (ILC) is a very effective technique to reduce systematic errors that occur in systems that repetitively perform the same motion or operation. However, several characteristics have prevented standard ILC from being widely used for high precision motion systems. Most importantly, the learned feedforward signal depends on the motion profile (setpoint trajectory) and if this is altered, the learning process has to be repeated. Secondly, ILC amplifies non-repetitive disturbances and noise. Finally, its performance may be limited due to position-dependent dynamics. This paper presents the design and implementation of a time–frequency adaptive ILC that is applicable for motion systems which executes the same motion or operation. It employs the same control system block diagram as standard ILC, but instead of a fixed robustness filter it uses a time-varying filter. By using the results of the time–frequency adaptive ILC, i.e., the shape of the learned feedforward signal, a “piecewise ILC” is proposed that leads to the design of a single learned feedforward signal suitable for different setpoints. The results are experimentally shown to work for a high precision motion system.

adaptive filtering
learning control systems
motion control
time–frequency analysis
time-varying filters

http://resolver.tudelft.nl/uuid:c18b6a74-a194-4bd2-a51e-d167f7398c0c

IEEE

1063-6536

IEEE Transactions on Control Systems Technology, 16 (5), 2008

Institutional Repository

journal article

(c) 2008 IEEE