Non-holonomy in im torque control

In the paper IM torque control is studied as an example of non-holonomic system with drift terms. Following the famous Brockett integrator problem several control propositions are introduced. The paper extends the control scheme from the state to the output control in several steps. By introducing adjusted amplitude, frequency and phase modulation of the IM stator current vector, the rotor flux linkage vector is implicitly forced to generate required periodic orbits that satisfy nonholonomic constraint. Improvements in the transient feedback performance, maximal steady-state efficiency, avoidance of singularities and sufficient robustness are actually achieved by making the current modulation dependent from the torque error signal. In the contrast with the original work instead of global only local stability could be assured. Simulation and experimental results illustrate main characteristics of the proposed control