Graduate Thesis Or Dissertation

Direct digital speed control system for a DC motor using a minicomputer

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  • Direct digital control is becoming quite common in the control of industrial processes. However, due to the relatively high accuracy of both analog and conventional digital systems for controlling the speed of a dc motor, there has been a reluctance to try DDC for this purpose. This thesis describes a direct digital control system for speed control of a dc motor, and shows the significant advantages it has over the more conventional methods. The system consists of a dc tachometer, an A/D converter, a clock, a time shared PDP-8 minicomputer, interface logic, and a resistor switching circuit. Computer simulation is used to optimize various system parameters and check the feasibility of the control scheme. The final system is capable of regulating speed to an accuracy of 0.2% and can also control the acceleration of the motor. The control program only uses 2% of the core storage and 0.3% of the computer's time, thus enabling the computer to be time-shared with many other control loops. Overall, this thesis shows the feasibility of a direct digital speed control system for a dc motor.
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