Experiment on trajectory tracking control of high precise positioning system based on iterative learning controller with wavelet filtering

For the objects with repeated motion characteristics such as Integrated Circuit(IC) packaging, Iterative Learning Control (ILC) offers a good scheme for achieving the control of high precise positioning and fast system response. However, in actual production, the performance is significantly deteriorated because of the unavoidable related disturbances when the learning data of a specific position are transferred to other positions, even in the same leading length motion condition. To improve the trajectory tracking performance of the same leading length operations in total workspace, this study proposes an iterative learning controller with wavelet filtering method to eliminate the dependence of iterative learning feed-forward on the special positions of different trajectory conditions. Through the wavelet analysis of the tracking errors with two different starting points, corresponding wavelet coefficients are obtained separately. Then by means of adjusting the wavelet coefficients, the non-consistent disturbance related to positions are removed, thus a universal feed-forward sequence unrelated to the special position is acquired which can be used for trajectory tracking of the same leading length operations in total workspace. Finally, the effectiveness of the proposed method has been demonstrated with the experimental results of a voice coil motor actuating positioning system.