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Should I use PID or PIV?

This is a very commonly asked question. There are several things to consider when answering this question. First what are PID and PIV?

 
  • PID is a control algorithm based on position error.
    PID is a very common control algorithm in industry. It is used for systems as varied as precise motion control to fluid level control to temperature control to ..

  • PIV is a control algorithm based on velocity error for its inner loop and position error for its outer loop.
    PIV is similar in concept to a velocity drive that has a position loop around it. The XMP implements the velocity loop and position loop inside its DSP.

 

Here are some things to consider before making the decision between PID and PIV:

 
  • Are you already comfortable tuning one method? If you are comfortable with one, you likely will get better performance and reduce your tuning time significantly.

  • Many more people have experience with PID tuning. If you have experience tuning systems with tachometer feedback, you may find PIV more familiar.

  • Try both. If performance is critical to you, you should explore all reasonable possibilities. Trying PID and PIV is not an unreasonble amount of effort if performance is critical.

  • How linear is your system? PID has good results if the system is a simple mass with a force or torque transducer (i.e. simple permanent magnet motor) powering it. If you have a robot with linkages that change mass moment of inertia when it moves and an exotic motor that is not a perfect torque/force transducer, PIV may work better.

  • Systems that care more about velocity regultation than position error will likely have better velocity regulation with PIV than PID.

  • PIV has more parameters to adjust than PID. This is a pro and a con.

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