Robust Current Decoupling in a Permanent Magnet Motor Combining a Geometric Method and SMC

In this work, a new control strategy for a permanent magnet linear motor is conceived. Geometric methods and sliding mode control are combined to reduce the effects of the nonlinearities due to the interaction between the coil currents and to achieve robust positioning. In fact, due to the presence of the induced voltage, the effects of nonlinearities cannot be cancelled without the help of other auxiliary and intrinsically robust techniques. Indeed, the sliding mode controller which is devised makes the whole structure robust with respect to any kind of inaccessible external and internal disturbance, such as induced voltages, loads, and parametric uncertainties. In particular, the paper indicates necessary conditions for the existence of a so-called decoupling sliding mode control scheme. The proposed method has the advantage of providing a controller which has a very simple structure, can be applied to a large variety of actuators and guarantees very good power performance with respect to the non-compensated decoupling controller. Simulation results are reported to validate the proposed methodology.