What is FOC control? FOC control motor jitters when load increases

What is FOC control

FOC (Field-Oriented Control), also known as vector control, is a motor control technology for controlling AC motors. This technology can control the direction and size of the motor's magnetic field, thereby achieving precise control of the motor.

FOC control decomposes the actual current signal of the three-phase AC motor into a DC current perpendicular to the direction of the magnetic field and a sinusoidal AC current in the same direction as the magnetic field in the "stationary coordinate system", thereby controlling the speed, position, acceleration, etc. of the motor. FOC control usually requires precise definition of the direction and strength of the magnetic field, and the use of some advanced algorithms to control the movement of the AC motor.

FOC control usually involves PID control algorithm and inverter (or drive) controller. PID control algorithm controls the motor by adjusting the direction and size of the motor's magnetic field, and the inverter is used to convert the power supply voltage into variable motor voltage and frequency to control the motor.

FOC control is an advanced control technology currently widely used in brushless DC motors (BLDC) and AC motors in a wide range of applications. It is characterized by high control accuracy, high efficiency, good stability, and the ability to provide smoother motion. It is suitable for a variety of applications, such as electric vehicles, motor vehicles, industrial robots, precision instruments, compressors, etc.

foc control motor jitter when adding load

When the FOC control motor increases the load, the jitter is usually caused by unreasonable settings of the speed loop and current loop parameters. It can be optimized in the following aspects:

1. Increase the proportional gain of the speed loop: When the load is increased, the speed loop controls the speed regulation of the motor and responds slowly. If the proportional gain of the speed loop is insufficient, the speed control accuracy will be insufficient, thus causing jitter. The proportional gain of the speed loop can be appropriately increased to increase the sensitivity of the speed loop to changes in the motor load.

2. Adjust the speed and current loop parameters: The speed loop and current loop are the core links of FOC motor control. Reasonable parameters need to be set according to the specific motor parameters to ensure the accuracy and stability of motor control. When the load increases, you can consider optimizing the speed loop and current loop parameters, adjusting the appropriate PID parameters, and enhancing the control ability of motor load changes.

3. Increase the dead zone of the current loop: When FOC controls the motor, the current loop dead zone problem is often encountered, especially in low-speed operation. Increasing the dead zone of the current loop can reduce the oscillation of the current loop and improve the control accuracy of the motor load change.

4. Increase the system sampling frequency: The system sampling frequency is one of the key factors affecting the FOC control accuracy. The higher the sampling frequency, the higher the control accuracy and stability. Increasing the system sampling frequency can improve the calculation accuracy of the FOC controller, thereby reducing the jitter problem when the motor load changes. It should be noted that when FOC controls the motor, it is necessary to continuously adjust the parameters and optimize the control strategy according to the experimental results to obtain better control effects. When optimizing the FOC controlled motor, the jitter problem when the load changes can be reduced by adjusting the PID parameters, increasing the controller calculation accuracy, and increasing the system sampling frequency.