FPGA Implementation of a Recursive Algorithm for Time Optimal Control of AC Drives

In modern high dynamic applications the acceleration performances of the permanent magnet synchronous motor (PMSM) drives are limited by the torque control, which delivers the required variations of current amplitudes in the stator inductive phases. In principle, time optimal control (TOC) of stator currents assures the fastest transients, within the boundaries imposed by the voltage inverter and the thermal limits. Nevertheless, the time optimal control implementation for a PMSM drive lacks of a closed form solution. A transcendental set of equations has to be solved to get the suitable voltage references. The computational load is excessive, at least for the digital signal processors (DSPs) presently used in electric drives. The proposed work shows how a field programmable gate array (FPGA) can be profitably used to implement the time-critical part of the sophisticated TOC algorithm, as a bright example of the new possibilities of hardware/software integration in embedded control systems.