node-pid-controller

Simple Node.js PID controller.

Installation

$ npm install node-pid-controller

Example

Let's take the example of a car cruise control. We want the car driving at 120km/h.

Create a Controller instance

k_p, k_i and k_d are the proportional, integral and derivative terms. dt is the interval of time between two measures. If not set, it will be automatically calculated.

let Controller = require('node-pid-controller');

let ctr = new Controller({
  k_p: 0.25,
  k_i: 0.01,
  k_d: 0.01,
  dt: 1
});

You can also pass options as arguments:

let ctr = new Controller(0.25, 0.01, 0.01, 1); // k_p, k_i, k_d, dt

Set the target

ctr.setTarget(120); // 120km/h

Get the correction

let correction = ctr.update(110); // 110km/h is the current speed

Real example

Normally, you use the correction to a measure, in a closed loop.

let goalReached = false
while (!goalReached) {
  let output = measureFromSomeSensor();
  let input  = ctr.update(output);
  applyInputToActuator(input);
  goalReached = (input === 0); // in the case of continuous control, you let this variable 'false'
}

Options

• k_p, k_i, k_d: the PID's coefficients
• dt: interval of time (in seconds) between two measures. If not provided, it will be automatically calculated.
• i_max: the maximum absolute value of the integral term (optional)

Test

mocha test

Author

Philmod <philippe.modard@gmail.com>