Sliding Mode Control and Observer-Based Disturbance Compensation for a Permanent Magnet Linear Motor

Tracking control of permanent magnet linear motors is a demanding task due to a nonlinear dependency of the drive force on the currents. In order to simplify the cascaded control design proposed in this paper, the input nonlinearity is eliminated first. The inner control design achieves a high bandwidth of the currents. In the outer control loop, sliding mode control is combined with a nonlinear disturbance observer, which leads to a reduction of the chattering effect by reducing the switching height. The sliding mode controller contributes to the robustness of the overall control structure and addresses any kind of inaccessible external and internal disturbances – like external loads, induced voltages as well as parametric uncertainties. Successful simulation results indicate the potential of the proposed nonlinear control strategy.