Building an electronic motor simulator

Motion control has been one of my active research for more than a decade. To demonstrate an exercise to my students, I often have to carry a set of brushed DC motor, electronics, and power supply (Figure 1) to the class. Such motor is quite easy to operate. It’s their overall weight that I seem to have problem with. Also, due to limited budget, I have to fish for second-hand motors that are still working. From time to time I got a crippled one, such as a loose encoder wire. This could create a bug difficult to trace. It could also be dangerous when one experiments with control design on a real motor, especially when it is coupled mechanically to something.
Figure 1: Brushed DC motor

For teaching purpose, therefore, I have an idea of constructing an electronic motor simulator, which from now on I’ll call it emotor. Of course, it could not do the job of real motor when a mechanical system has to be driven. However, It should be useful for basic feedback control study in the sense that the benefits of feedback are illustrated clearly. Hopefully this could motivate students better than using pure simulation with Simulink or Scilab/Xcos.

In the past, I used to build a multi-axis motor simulator and called it ServoSim. That one could only generate quadrature encoder pulses for 4 axes, but it didn’t show rotation visually. This new emotor, whose prototype is wired as in Figure 2*, simulates a single motor. In addition to generating quadrature signals A, B and index signal Z, it has 6 LEDs located 60 degree apart on a circle. The LEDs are lid in accordance with motor rotation speed, which is commanded by a pair of PWM and DIR commands just like the original DC motor in Figure 1.

Figure 2: Prototype of emotor

*The emotor project has nothing to do with PCI interface. This general-purpose PCB is the only one I have on the shelf.



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