Chinese application note: AN2757 - Encoder-based sensored field-oriented control of three-phase permanent magnet synchronous motors (PMSM)

Permanent magnet synchronous motors (PMSMs) are widely used in various industries due to their high power density, small size, and high efficiency. For applications that require fast dynamic response to speed and torque changes, complex control techniques such as field-oriented control (FOC) must be used. Speed ​​sensor-based FOC is useful to avoid control inaccuracies that can occur in sensorless control because the physical parameters of the motor change with temperature and aging. However, the configuration of such applications must be equipped with a speed sensor, such as an incremental encoder.

The document recommended today introduces the implementation of a three-phase PMSM encoder-based sensored FOC algorithm using Microchip's 32-bit MCU.

Field Oriented Control of PMSM

Field-oriented control (FOC) refers to a method that considers one of the fluxes (rotor, stator or air gap) as the reference frame for all other quantities, with the goal of decoupling the stator current into a component that produces torque and a component that produces flux. This decoupling ensures that complex three-phase motors can be controlled as simply as DC motors with separate excitation. This means that the armature current is responsible for producing torque, while the field current is responsible for producing flux.

Block Diagram of PMSM Sensored FOC

Sensored FOC Implementation Flowchart

PID Controller

• PID Controller Background

• Adjust PID gain

• Control loop in FOC

Coordinate transformation

• Clarke Transform

• Park Transform

• Inverse Park Transform

• Clarke inverse transform

Space Vector Pulse Width Modulation (SVPWM)

Position measurement

Quadrature Decoder for SAME70 MCU

Quadrature Encoder Interface for PIC32MK MCUs

Motor starting and alignment

For more complete Chinese documents, please visit Dr. Mai's Library