Frequency response based feedforward control design with uncertainty considerations

System frequency response data is used to obtain a time domain impulse response model in contrast to the conventional way of deriving transfer function by curve fitting of frequency response or time domain system identification methods. This method is first applied to time response prediction and is shown to reduce prediction errors at frequencies where the model is in error. A feedforward controller is then designed by defining the desired controller behavior in the frequency domain. A design methodology for minimizing feedforward control tracking errors due to model uncertainty is developed and applied in conjunction with frequency response based feedforward controller design. Experimental results are shown for applying these approaches to an electrohydraulic system