I am working on implementing an analog (yes, op-amps, possibly digital in the future) PID controller to regulate current for a laser. There is more to come...
For now, I have the PID match various inputs from function generator (sine waves, square waves, triangle waves i.e. AC input, haven't tried the "step process" yet as described in all tuning procedures) with a set point also coming from function generator to see how the thing is supposed to work as I have no formal background, I have read quite a bit and followed all the lins advised on the site.
On to my question - I am trying to figure out why I am able to get the input signal to match the setpoint by adjusting all the gains, but at lower (below 50 Hz) it always has a sine wave riding on top of it. It is not random noise and it disappears at higher frequencies. Is it the undamped oscillations that from improper tuning? Does it have something to do with the fact that the signal is AC? I cannot find any reference discussing this.
Another question is this - if my setpoint is AC signal with a frequency of 100kHz, is PID capable of getting the input perfectly close to the setpoint, what are acceptable standards? I understand that it depends on the tuning...
Thank you for any input; if needed, I will try to get a pic of that waveform tomorrow.
For now, I have the PID match various inputs from function generator (sine waves, square waves, triangle waves i.e. AC input, haven't tried the "step process" yet as described in all tuning procedures) with a set point also coming from function generator to see how the thing is supposed to work as I have no formal background, I have read quite a bit and followed all the lins advised on the site.
On to my question - I am trying to figure out why I am able to get the input signal to match the setpoint by adjusting all the gains, but at lower (below 50 Hz) it always has a sine wave riding on top of it. It is not random noise and it disappears at higher frequencies. Is it the undamped oscillations that from improper tuning? Does it have something to do with the fact that the signal is AC? I cannot find any reference discussing this.
Another question is this - if my setpoint is AC signal with a frequency of 100kHz, is PID capable of getting the input perfectly close to the setpoint, what are acceptable standards? I understand that it depends on the tuning...
Thank you for any input; if needed, I will try to get a pic of that waveform tomorrow.