Research on DC motor speed control system based on PID

In engineering design and experiment, the speed of DC motor is often controlled. The common way is to generate PWM wave through timer, and adjust the speed of motor according to duty cycle. In theory, the velocity is proportional to the duty ratio. But in practice, because of the resistance, friction, motor performance parameters and so on, it often appears in a certain fixed duty ratio, the motor speed is uncertain. At this time, the speed of the DC motor is controlled by PID, and the speed of the DC motor is constant by adjusting the ratio, differential and integral coefficient.