Adaptive Robust Motion Control of an Ironless Permanent Magnet Linear Synchronous Motor with Dead-zone Compensation

The ironless permanent magnet linear synchronous motor (ILPMLSM) is widely used in precision applications because of its advantages, such as direct drive, zero cogging and attractive force, and high speed and acceleration potential. In most of the existing control schemes, the adaptive robust control algorithm has special advantages in dealing with parameter uncertainties and uncertain nonlinearities of the linear motor systems. However, the previously ignored nonparametric uncertainty (noise and disturbance) is widespread in industrial applications. Furthermore, even small uncertainties may produce parameter drift possibly leading to instability of the control system, when the reference signals are not persistently exciting. In this paper, a nonlinear dynamic model of an ILPMLSM system including both the traditional various uncertainties and the previously ignored nonparametric uncertainty is given, leading to a better understanding of the parameter drift and system instability caused by the noise and disturbance. Additionally, an adaptive robust control scheme with dead-zone compensation is proposed. The dead-zone technique is employed to improve the discontinuous projection adaptation law. The approach of dead-zone compensation adaptive robust control is applied to synthesize the system controller for both accurate parameter estimation and a guaranteed robust performance to various uncertainties. Comparative experiments show that the proposed approach can achieve fast and accurate trajectory tracking, robustness, and stability against uncertainties mentioned above.