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Unread 29-01-2015, 08:02
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Re: PID Issue

Quote:
Originally Posted by rclothier View Post
When the gain gets above 0.007, the wheels ramp up directly to full speed (+/- 1); the encoder velocity (process variable) goes to about 250 in/s. Its basically all or nothing.
This makes me think you may have a sign issue in the math. Do not set it on the floor until you check for this or else you might damage something or someone.

Run the test you described above again and compare your axis value and your rate value. Do they have the same sign (i.e. are both positive or both negative?). If they have different signs, your controller will become unstable (i.e. the speed will quickly ramp up to full speed). In this case, you will need to negate the encoder rates, then try again. The controller should become well behaved after that.

One other thing: are you scaling the axis values from -1 to 1 to a value in in/sec?
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