About Arduino PID Library Issue

Projects Programming
1

Hello,

I have some question and I would like to ask to who has idea about PID_V1 library.These lines are from this PID.

Code:

double input = *myInput;
double error = *mySetpoint - input;
double dInput = (input - lastInput);
outputSum+= (ki * error);
/Add Proportional on Measurement, if P_ON_M is specified/
if(!pOnE) outputSum-= kp * dInput;

  if(outputSum > outMax) outputSum= outMax;
  else if(outputSum < outMin) outputSum= outMin;

  /*Add Proportional on Error, if P_ON_E is specified*/
   double output;
  if(pOnE) output = kp * error;
  else output = 0;

  /*Compute Rest of PID Output*/
  output += outputSum - kd * dInput;

I could not understand the kd part. Why is not the Kd parameter error difference. As you can see, dInput is not error difference. Thanks for helping

2

double dInput = (input - lastInput);

doesn't dInput represent the change in the value of the input from the preceding value? only the proportional term is calculated from the difference between the target and current position

3

In theory, dInput is the time rate of change of input, and that should include a term for the input sample rate. Sometimes that is included in the Kd value.

One of many tutorials on PID.

4

For the PID_v1 library the sample time is a constant so scaling is not needed.

5

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