Hybrid Control Scheme for Permanent Magnet Gear Motor

A gear motor is a special motor that integrates an AC motor and gearbox within a single housing. Typically, a permanent magnet (PM) motor is used in a gear motor. Due to its special construction, high torque accuracy, minimal torque ripple and a sensorless control scheme has to be considered. Consequently, a hybrid control scheme is proposed in this paper for a PM gear motor. At low speed, an I/F control is proposed to generate high starting torque and stable speed control. For medium to high-speed range, a flux vector (FV) sensorless control with an adaptive observer is proposed to achieve high efficiency and accurate torque control. During the transition between low and high speed, a blending method is used to seamlessly transfer from I/F to FV control during speed ramp-up, and vice versa during ramp-down. Experiment results, obtained from a general variable speed drive with a PM gear motor, validate the robust and high performance of this control scheme.