Optimal estimation of rational feedforward controllers: An instrumental variable approach

Iterative control enables a significant control performance enhancement by learning feedforward command signals from previous tasks in a batch-to-batch fashion. The aim of this paper is to develop an approach to estimate the parameters of rational feedforward controllers that provide high performance and extrapolation capabilities towards varying tasks. An instrumental variable-based algorithm is developed that leads to unbiased parameter estimates and optimal accuracy in terms of variance. The approach also enables optimal estimation of a feedforward controller using a polynomial basis. Simulation results confirm that optimal accuracy is obtained with the proposed approach.