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| Question on PID for speed control of DC motor in treadmill application |
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| XaviPacheco:
In treadmill applications with DC motor, you can't go from 0.5 mph to 1 mph instantly. The speed should be gradually increasing. If I want to design a PID for speed control, my setpoint should be a ramp instead of steps, right? Or, I can give the setpoint in steps and the P gain adjust the time response of the system? Which one is the right approach? I think that once the final setpoint is reached as ramp, the PID controller should compensate the output for changes in the load. My feedback is a speed sensor that will tell the controller the actual speed. If I said my setpoint is 0.5 mph, the PID doesn't care if gave the setpoint as a ramp or step. Am I right? |
| jbb:
Generally I would try to use fixed controller gains (P, I, optional D) and ramp the reference signal. |
| XaviPacheco:
--- Quote from: jbb on November 02, 2018, 06:12:54 pm ---Generally I would try to use fixed controller gains (P, I, optional D) and ramp the reference signal. --- End quote --- That's what I think. As far as I know, for me to achieve the speed ramping, I shoud use a ramp as setpoint. But I've been told I'm wrong, that the PID should do the ramping itself by slowing the system time response with the P gain. So, I don't find a way to explain him that ramping the setpoint should not have to do with the PID purpose. |
| krisRaba:
If you set PID for slow response to use it for ramping you will also get very poor response to load changes etc. In treadmills acceleration and deceleration is different so it's quite hard to find parameters that ideally fits both situations. It is easier to separate ramping algorithm and let fast PID just follow it as SP. |
| james_s:
Ramping the throttle signal is very easy once you have good closed loop control of the speed. All you need is what is essentially a very crude digital low pass filter. |
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