initial commit

node_modules/node-pid-controller/lib/index.js

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+/**
+ *  PID Controller.
+ */
+var Controller = function(k_p, k_i, k_d, dt) {
+  var i_max;
+  if (typeof k_p === 'object') {
+    var options = k_p;
+    k_p = options.k_p;
+    k_i = options.k_i;
+    k_d = options.k_d;
+    dt = options.dt;
+    i_max = options.i_max;
+  }
+
+  // PID constants
+  this.k_p = (typeof k_p === 'number') ? k_p : 1;
+  this.k_i = k_i || 0;
+  this.k_d = k_d || 0;
+
+  // Interval of time between two updates
+  // If not set, it will be automatically calculated
+  this.dt = dt || 0;
+
+  // Maximum absolute value of sumError
+  this.i_max = i_max || 0;
+
+  this.sumError  = 0;
+  this.lastError = 0;
+  this.lastTime  = 0;
+
+  this.target    = 0; // default value, can be modified with .setTarget
+};
+
+Controller.prototype.setTarget = function(target) {
+  this.target = target;
+};
+
+Controller.prototype.update = function(currentValue) {
+  this.currentValue = currentValue;
+
+  // Calculate dt
+  var dt = this.dt;
+  if (!dt) {
+    var currentTime = Date.now();
+    if (this.lastTime === 0) { // First time update() is called
+      dt = 0;
+    } else {
+      dt = (currentTime - this.lastTime) / 1000; // in seconds
+    }
+    this.lastTime = currentTime;
+  }
+  if (typeof dt !== 'number' || dt === 0) {
+    dt = 1;
+  }
+
+  var error = (this.target - this.currentValue);
+  this.sumError = this.sumError + error*dt;
+  if (this.i_max > 0 && Math.abs(this.sumError) > this.i_max) {
+    var sumSign = (this.sumError > 0) ? 1 : -1;
+    this.sumError = sumSign * this.i_max;
+  }
+
+  var dError = (error - this.lastError)/dt;
+  this.lastError = error;
+
+  return (this.k_p*error) + (this.k_i * this.sumError) + (this.k_d * dError);
+};
+
+Controller.prototype.reset = function() {
+  this.sumError  = 0;
+  this.lastError = 0;
+  this.lastTime  = 0;
+};
+
+module.exports = Controller;