Motor Control

Motor Control is defined here as the control of an electromagnetic motor and the associated systems which are required to make it work in a system. There is many different types of electric motors to be controlled. Here we focus on those that are of most interest in the home and light industrial environments and the issues that result from this.

  • Brushed DC motors - limited life time applications
  • Stepper motors - low power applications
  • BLDC motors - fractional horsepower
  • PMSM motors - fractional horsepower
  • Induction motors - fractional horsepower

Today, unless energy efficiency is not an issue at all, the focus is on BLDC and PMSM electric motors because they offer lower lifecycle cost and more efficient operation. This has changed in the last few years as rare earth magnets actually reduced the size of these motors to make them smaller and therefore less costly than competitive motors.

Motor Control for these motors is unique though. Because commutation of the motor is electronic, the drive circuits must be electronically controlled to produce a rotating shaft with reasonable torque throughout the loading curve of the motor. The goal is generally to have a shaft velocity in RPM which can be controlled.

Velocity control of BLDC and PMSM motors is accomplished using a single PID loop in general. More advanced control schemes are required as users require less torque ripple or smoother operation and more efficient operation. Today most energy efficient systems use advanced vector or field oriented control algorithms to minimize torque ripple and maximize energy conversion.

DSPnano and Unison both offer motor control server software. It has a variety of options depending on the processors that it runs on. Both sensored and sensorless options are available in both six step (BLDC) and vector (PMSM) control versions