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PID constants

BINU K
Intellectual 935 points

Hai,

      I implemented a PID algorithm for a generator speed control by  adjusting  engine throttle valve  using a stepper motor. Here Iam measuring RPM of generator  axile output rotation  with hall effect  sensor as  a feedback.

It works fine, but in this algorithm I changed my Kp,Ki,Kd constants in different conditions. ie nearest of setpoint I changed these constants to get fine values and if there is a big difference changed to get large error value.

My question is , can i change, PID constants in running condition? Is it favourable ?

  • 0
    TI__Genius 16410 points

    Hello,

    This forum is typically for hardware questions about TI's automotive devices. I am not an expert on PID controllers, so let me ask some of my colleagues to try to get you an answer.

    Do you have any way to simulate your algorithm (eg. MATLAB)? If so, it could help you see if your algorithm works with changing PID constants.

    Regards,
    Karl

  • 0 in reply to Karl Wallinger
    Intellectual 935 points

    Here i built a small  working model with a dc motor,  attached with a position sensor on its shaft. Its RPM is 2000 , same as my real project.When potentometer change, the speed will change , so i attached this pot  togetherwith my  actual stepper motor.When stepper motor position change, the speed of motor change.So we can get a feedback, and error.

    Anyway it works fine with different pid constants. My doubt is because almost all article on internet is mentioned about one PID constants.

    thank you

  • 0
    TI__Expert 4760 points
    Hello BINU K,
    I don't see any problems with changing the PI gains during different operating conditions. For example, we typically lower the speed loop gain at higher speeds in some applications to enhance stability. Just remember...by doing this, you are creating a nonlinear system. That is not necessarily a bad thing, but sometimes it can lead to unexpected performance. But the bottom line is the results! If you are getting the results you need without any problems being created, then feel free to do this.