Time optimal control for induction motor servo system

A time-optimal position control scheme based on Pontryagins's minimum principle is proposed for the current-source-inverter (CSI)-fed induction motor system. An induction motor with field-oriented control is modeled by a fast time-optimal position control system of second order that has two modes of operation: a bang-bang mode that operates until the position is close to target, followed by a DC breaking mode that provides asymptotic stability. This is achieved by substituting the time-optimal controller for the speed controller in the conventional field-oriented control loop of the motor. The validity of the time-optimal approach has been verified by an experimental test carried out with a prototype MC68000-based microcomputer system and a 5 HP induction motor. Experimental and simulation results are in close agreement.<<ETX>>