Closed Loop Speed Control

[Ether]

Originally Posted by kgzak

I want to make a closed loop speed control VI to get a very accurate speed for the motors to run. I know how to calculate the speed using encoders but is there a different way to tell the victor what speed to set the motor to? I feel that the Se Motor Speed VI is not very accurate.

The Set Motor Speed VI is a mis-nomer. It doesn't set motor speed, it sets motor voltage (via PWM). Under certain idealized conditions motor speed will be proportional to motor voltage, but this is rarely the case with the motorized applications in FIRST. That's why it is not accurate.

If you want closed-loop speed control, you can run the encoder signal to the cRIO and create your own PID control or use a library function. Or, use the Jaguars instead of the Victors. The Jags have built-in closed-loop speed control if you command them via CAN bus and feed the encoder signal directly to them. Which raises the question: has there been a clear ruling from GDC whether or not this is permissible?


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