Second-Order Sliding Mode Control with State and Disturbance Estimation for a Permanent Magnet Linear Motor

As the drive force depends in a nonlinear way on the currents, tracking control of permanent magnetic actuators requires sophisticated control approaches. In this contribution, a cascaded control strategy is proposed that cancels the effect of the nonlinearity and allows for an accurate trajectory tracking. The strategy involves the combination of an inversion-based current control, a second-order sliding mode control (SMC), and a Kalman filter (KF) that provides estimates for the state variables as well as a lumped disturbance force from noisy measurements. The combination of second-order sliding mode control and estimator-based disturbance compensation contributes to the robustness of the overall control structure, reduces chattering effects significantly and addresses unknown disturbances as well as parametric uncertainties. Successful simulation results indicate the potential of the proposed nonlinear control strategy.