Abstract : This paper addresses the issue of speed control accuracy in DC speed control systems. A DC speed control system employing a CNC (Computer-Aided Controller) is proposed. This system utilizes a digital method of the PID algorithm and an optimal PID parameter setting method to improve the speed control accuracy. Keywords : DC speed control system; CNC; digital frequency converter; PID controller; optimal control strategy DC speed control systems have been widely used due to their excellent performance. Currently, in various closed-loop DC speed control systems, analog controllers are commonly used, with PID control algorithms employed for current and speed regulators. Theoretical research and practice have proven that this control algorithm can improve the closed-loop stability and steady-state control quality of the system. However, a drawback of this control algorithm is its slightly poor dynamic performance. Therefore, this paper proposes a DC speed control system with a CNC. This system employs a new control algorithm—the optimal PID algorithm—and its dynamic and static performance is studied. 1 Working Principle The structure of the DC speed control system is shown in Figure 1. It consists of a microcomputer controller (CNC), a digital frequency converter, a rectifier, a DC motor, and sensors. The microcomputer digital controller (CNC) is the heart of the DC speed control system. The photoelectric encoder sends the motor speed signal to the CNC. The given speed signal is converted into a photoelectric encoder specification signal by the A/P conversion circuit (a circuit converting the given speed signal to the photoelectric encoder specification signal) and then sent to the CNC. The photoelectric encoder specification signal sent to the CNC by the photoelectric encoder and MP conversion circuit must be converted into a digital quantity by the P/D conversion circuit (a circuit converting the photoelectric encoder signal to a digital signal) before it can be used in the digital PID control algorithm to achieve speed control. The digital frequency converter used is MF-3.7K-380, and the rectifier is a three-phase bridge full-wave uncontrolled rectifier circuit. [b][align=center]For more details, please click: DC Speed ​​Control System with CNC[/align][/b]