Quote:
|
Originally Posted by thinkpad
Hello,
We are having a similar problem with our PID control at high speed. Could you please direct me to some information on the 7474 signal stretcher circuit. Any circuit diagrams/types of chips used would be extremely helpful.
|
Kevin Watson posted this schematic:
http://kevin.org/frc/encoder_phase_b...ng_circuit.pdf
It works great (though it didn't solve the more mechanical issue in our case).
Quote:
|
Another thing I was thinking was putting in our PID code into the the Process_Master_IO part of the code which is being called every cycle at a faster rate than 26 ms. The thinking is if the phase-B will operate at a faster rate giving the code more consistency. If my idea is completely newbie and unfounded for, don't be cruel.
|
No, that won't do what you want it to. The PID function is written to work correctly only if it's called at a regular rate, and the "fast loop" doesn't have a guaranteed timing. It runs quickly most of the time, but gets delayed every time the 26 ms communication arrives, and there's no easy way to determine how often it runs.
You almost certainly don't need the PID sampling to run more quickly than 39 times a second anyway. If the mechanical response of a system is faster than that, it's probably not going to need PID control in the first place.