MIMO FIR feedforward design for zero error tracking control

This paper discusses a multi-input multi-output (MIMO) finite impulse response (FIR) feedforward design. The design is intended for systems that have (non-)minimum phase zeros in the plant description. The zeros of the plant (either minimum or non-minimum phase) are used in the shaping of the reference signals whereas the poles of the plant are used in constructing feedforward forces. The FIR coefficients themselves are obtained from data-based optimizations which are the result of iterative machine measurements on an industrial wafer scanner. The resulting experimental results demonstrate the ability to obtain zero error tracking.