Non-Holonomy in Induction Machine Torque Control

In this brief, induction machine (IM) torque control is studied as an example of a 3-D non-holonomic integrator including drift terms. By expanding Brockett's controller derived for the driftless systems, a control structure is proposed that provides simultaneous modulation of both the amplitude and the frequency of the sinusoidal stator current vector. Although not explicitly controlled or programmed, the rotor flux linkage vector is implicitly forced to track natural periodic orbits satisfying non-holonomic constraints of the IM. The proposed control assures high dynamics in the torque response, maximal torque per amp ratio during transients and in steady-state and global asymptotic stability. The overall IM control scheme includes cascaded high-gain current controllers based on measured electrical and mechanical quantities together with rotor flux linkage vector estimator. Simulation and experimental results illustrate the main characteristics of the proposed control.