Iterative Feedforward Tuning for A PMLSM with Unknown Time Delay and Current-Dependent Force Ripple

Permanent magnet linear synchronous motors (PMLSMs) have been widely used in industrial applications requiring high speed and positioning precision. Iterative feedforward tuning (IFFT) methods enhance the extrapolation ability to variant tasks without sacrificing the accuracy of iterative learning control methods. However, existing IFFT methods do not consider the compensation of the current-dependent force ripple. Meanwhile, the compensation of time delay is not taken into account. To cope with these two problems, this paper proposes a novel IFFT method for PMLSMs with unknown time delay and current-dependent force ripple. Time delay is approximated by Taylor expansion, whose coefficients can be tuned iteratively in the IFFT scheme. Control signal is incorporated into the polynomial basis of the IFFT, which can deal with the current-dependent force ripple. Simulation results based on an ironless PMLSM illustrate the validity of the proposed method.