Microprocessor-Based Speed Control System for High-Accuracy Drives

A digital speed control system for a dc motor with a pulse tachogenerator for speed sensing is described. A microprocessor is used for fast speed measurement with a response time constant of the order of 8 ms and a resolution of 0.0125 percent of the top speed. This has become possible because of the principle of obtaining the latest speed value based on the previous speed value. This paper describes the principle of speed measurement and control, the flowchart, and the experimental results. A closed-loop speed holding accuracy of ±0.025 percent of the top speed is obtained.