Abstract: In this paper a control system is designed, which is aimed at DC dynamoelectric valve used in the petrochemical field production. It tests the rotating speed of motor and the displacement with photoelectric encoder and constructs digital phase-locked-loop based on DSP (DSPLL), which produces PWM logic and adjusts the frequency and dumpy to control the input voltage and input currency of DC motor. At last, it controls the valve to be open or closed. This system adjusts automatically the rotating speed and torque of DC motor according to the piston of the dynamoelectric valve, the rotating speed of DC motor and torque of load and ensures that rotating speed and torque of DC motor are optimal matching. Experiment with DC motor (80ZY24-200) proves that the system does not only guarantees high precision of speed and position, but also adapts the change of torque when it is changable continuously and protects DC motor effectively. So system is applicable to control the valve used in the petrochemical field production.

Key words: phase locking loop based on DSP, pulse width modulation, DC motor, control, dynamoelectric valve