Robust tracking performance of linear induction motor-based automatic picking system using a high-gain disturbance observer

To operate the movable ejectors of an automatic picking system (APS) with high dynamics and high precision, a robust speed tracking controller design for a single-sided linear induction motor (LIM) is presented using a high-gain disturbance observer method. The thrust disturbance as well as the mechanical parameter variation due to the mass change influences directly the tracking control performance of APS. To guarantee robustness in the presence of such uncertainty, a high-gain disturbance observer-based linear quadratic regulator (LQR) is designed from the mechanical dynamics. Since the estimated disturbance effectively cancels out real uncertainties in the system, the resulting system behaves like the closed-loop system consisting of the disturbance-free nominal model and the LQR. Since MATLAB-Simulink does not support a library for a LIM, a Simulink library model has been developed using the LIM dynamics. To verify that the proposed scheme has a robust control nature, the comparative simulations are carried out based on the library. The whole control system is implemented using DSP TMS320F28335 for a LIM driven by a three-phase voltage-fed pulse-width modulation inverter. Through comparative experimental results in the presence of disturbances, the effectiveness and robustness of the proposed scheme are verified.