Tweaked dt behavior

Author: emersion

lib/index.js

@@ -7,9 +7,9 @@ var Controller = function(k_p, k_i, k_d, dt) {
   this.k_i = k_i || 0;
   this.k_d = k_d || 0;
 
-  // Time interval between two updates
-  // If set to true, the interval will be automatically calculated
-  this.dt  = dt;
+  // Interval of time between two updates
+  // If not set, it will be automatically calculated
+  this.dt = dt || 0;
 
   this.sumError  = 0;
   this.lastError = 0;
@@ -27,10 +27,10 @@ Controller.prototype.update = function(currentValue) {
 
   // Calculate dt
   var dt = this.dt;
-  if (this.dt === true) {
+  if (!dt) {
     var currentTime = Date.now();
     if (this.lastTime === 0) { // First time update() is called
-      dt = 1;
+      dt = 0;
     } else {
       dt = (currentTime - this.lastTime) / 1000; // in seconds
     }

test/index.js

@@ -12,13 +12,13 @@ var Controller = require('../')
  */
 describe('pid-controller', function(){
 
-  var k_p = 0.5
-    , k_i = 0.1
-    , k_d = 0.2
-    ;
+  var k_p = 0.5,
+      k_i = 0.1,
+      k_d = 0.2,
+      dt  = 1;
 
   // Create the controller
-  var ctr = new Controller(k_p, k_i, k_d);
+  var ctr = new Controller(k_p, k_i, k_d, dt);
 
   it('should have set the coefficient', function() {
     ctr.k_p.should.equal(k_p);
@@ -45,7 +45,7 @@ describe('pid-controller', function(){
     ctr.lastTime.should.equal(0);
   });
 
-  it('should return the correction for a given update interval', function(){
+  it('should return the correction for the given update interval', function(){
     ctr.dt = 2; // 2 seconds between updates
     var correction = ctr.update(115);
     correction.should.equal(4);