本文介绍直流电机的调速原理，在此基础上，以AT89C51单片机为控制核心，设计了直流电机调速控制系统的外围电路，软件的实现上采用PI（比例-积分）控制算法，给出程序流程图。该调速系统容易实现，成本低廉，具有很好的实用价值-This article describes the principle of DC motor speed control, on this basis to AT89C51 single-chip microcomputer to control the core of the design of the DC motor speed control system of the external circuit, the software used to achieve the PI (proportional- integral) control algorithm to flow chart of a process. The speed control system easy to implement, low-cost and has good practical value