Precise contour following for biaxial systems via an A-type iterative learning cross-coupled control algorithm

•An A-ILC CCC and an algebraic equation based contour error model are combined for contour following improvement.•The convergence condition is succinctly analyzed in the frequency domain.•Perfect contour following is achieved by the proposed method regardless of whether the tracking errors are small or large.

This paper proposes an A-type iterative learning cross-coupled control (CCC) algorithm for biaxial systems. An algebraic equation based contour error model is used as the CCC input. This model has the advantage that it is zero if and only if the real value vanishes. The iterative learning CCC is designed to make its input converge to zero. Hence, it is expected to that the contour error will converge to zero as well. After analyzing the control algorithm convergence condition in the frequency domain, the proposed method is implemented on a motion stage. Experimental results show that the algorithm perfectly follows contours as the cycles approach infinity regardless of whether tracking errors are small or large.