Zero-Speed Maximum Torque (ZSMT) Algorithm

The ZSMT algorithm is designed for applications that require high torque at startup and operate at low speeds. In most applications, this is handled using specific hardware, such as quadrature encoders, resolvers or Hall sensors, all of which add cost and complexity to a design. By utilizing high-frequency injection principles combined with Field-Oriented Control (FOC) techniques, you can track exact rotor positions. Once optimal RPM is reached, the motor control can be switched over to regular FOC control using back-EMF measurement techniques.

While ZSMT is extremely versatile, especially in high-traction, high-torque and low-speed applications, it does pose some challenges, particularly in the physical motor design. Although the control hardware is the same as standard FOC, it does require the low-inductance and high-saliency motor typical of the Interior Permanent Magnet (IPM) type.