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javaautomationpid-controller

My PID Controller in Java is not operating correctly

I was looking for an implementation of a PID controller in Java and I found this one:

https://code.google.com/p/frcteam443/source/browse/trunk/2010_Post_Season/Geisebot/src/freelancelibj/PIDController.java?r=17

So, for what I could understand about it I am using it this way:

package lol.feedback;

public class dsfdsf {

    public static void main(String[] args) throws InterruptedException {
        final PIDController pidController = new PIDController(1, 1, 1);
        pidController.setInputRange(0, 200); // The input limits
        pidController.setOutputRange(50, 100); // The output limits
        pidController.setSetpoint(120); // My target value (PID should minimize the error between the input and this value)
        pidController.enable();
        double input = 0;
        double output = 0;
        while (true) {
            input = output + 30;
            pidController.getInput(input);
            output = pidController.performPID();
            System.out.println("Input: " + input + " | Output: " + output + " | Error: " + pidController.getError());

            Thread.sleep(1000);
        }
    }

}

But he never stabilizes. He doesn't behave like a PID at all... This is the output I get:

Input: 30.0 | Output: 100.0 | Error: 90.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0
Input: 80.0 | Output: 100.0 | Error: 40.0
Input: 130.0 | Output: 50.0 | Error: -10.0

Can someone help me tell me what I am missing?

Thank you!

Solution

  • Firstly, try with another set of PID parameters - for example final PIDController pidController = new PIDController(10, 1, 0.5); First parameter is responsible for gain of the closed-loop system. Second is responsible for eliminate fixed error on the output. Third is responsible for dynamic of control.

    Second thing - it is possible that real signal output is always out of limit, so it takes minimum/maximum value.

    Thirdly, why do you always add 30 to output and assign it to the input?