View Single Post
  #9   Spotlight this post!  
Unread 09-04-2016, 11:17
Alan Anderson's Avatar
Alan Anderson Alan Anderson is offline
Software Architect
FRC #0045 (TechnoKats)
Team Role: Mentor
 
Join Date: Feb 2004
Rookie Year: 2004
Location: Kokomo, Indiana
Posts: 9,112
Alan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond repute
Re: PIDController + Latency - related issues

If you are trying to analyze a system where you are controlling the velocity of a shooter wheel, you need to make sure that the process variable and set point are describing the same thing as the controller's output.

You can't just use RPM as the input and motor speed as the output. If you do that, then when the speed reaches the set point, the motor output will be zero. You either have to post-integrate the controller's output, or you have to reinterpret the PID as DPX. Among other things, that means the I constant in a velocity controller will have the same effect as the P constant in a position controller.

That is the reason your team found that you need Integral in order to get a shooter wheel to work. It has nothing at all to do with latency, or with the type of control device used by the driver, or with the graph of sin(x). Again, I urge to you to abandon this line of reasoning, because it is based on assumptions which do not match reality.
Reply With Quote