Microchip Sensorless Control Algorithm

Maximizing torque at low speed in permanent magnet synchronous motors

Microchip has introduced a new algorithm for the control of a Permanent Magnet Synchronous Motor (PMSM) which reduces system cost in applications requiring high torque at stand-still or low motor speeds.


The Zero Speed/Maximum Torque (ZS/MT) control algorithm by Microchip is a new implementation of Field-Oriented Control (FOC), a control technique for use in high-torque or low-speed motor-control applications.


These types of applications typically require three Hall effect position sensors. The new ZS/MT algorithm eliminates the need for Hall effect sensors, connectors and cables by using a reliable initial position detection method based on high-frequency injection to determine the exact rotor position at zero and low speeds. This enables the control algorithm to deliver maximum torque when starting from stand-still.


Because the algorithm enables a motor system to operate without sensors and their associated connectors and cables, it reduces component count and system cost. It also offers improved reliability, as it eliminates the potential for faults in cables or in ESD-sensitive Hall effect sensors.


Microchip supplies a rich set of resources to support customers’ development of high-performance sensorless motor-control systems. As well as a comprehensive FOC motor control library, it also provides:

  • The motorBench® development suite
  • Simulation support for MATLAB®, Simulink® and Scilab®


  • ZS/MT algorithm runs on various Microchip controllers:
    • dsPIC33 motor control digital signal controllers
    • SAM C2x microcontrollers
    • SAM D5x/E5x MCUs
    • SAM E7x MCUs
    • PIC32MK MCUs
  • Suitable for interior and surface permanent magnet motors


  • Drilling machines
  • Garage door openers
  • Automotive starters
  • E-bikes

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