Experimental study of time-frequency based ILC

In this paper, a frequency tuning method based on time-frequency analysis of error signal is presented for iterative learning control (ILC). Qualitative analysis and experimental investigation are presented. The method uses wavelet packet algorithm to decompose the error signal so that the maximal error component at any time step can be identified. The cutoff frequency of the filter at each time step is set to cover the frequency band up to the frequency region where the maximal error component resides. The proposed method allows high frequency error components enter the learning at proper time steps. While at other time steps, the cutoff frequency is set low to guarantee the good learning transient and long-term stability.