Stepper Motor Simulator

For CS 480, 3D Printing & Robotics, UAF 2015

Er, JavaScript or WebGL doesn't seem to be running, so basically all you're going to see is the bare code...

// Make simulated motor windings:
//   Each number is a current 
sim.coil=[1,-1];
sim.ncoil=2;
sim.coilangle=[0,90,180,270]; // degrees (second two are complementary)

// Make a simulated motor rotor:
sim.rotor={
  angle:0, // rotor's position, deg
  velocity:100, // rotor velocity, deg/sec
};

// Return the color of an object with this current
function make_color(charge) {
  var red=charge;
  if (red<0.0) red=0.0;
  var blue=-charge;
  if (blue<0.0) blue=0.0;
  var gray=0.3*(1.0-red-blue);
  return new THREE.Color(red+gray,gray,blue+gray);
}

// Create a THREE.js object for this cylinder
function make_cylinder(radius,distance,angle,charge)
{
  var colorCharge=make_color(charge);
  var C = new THREE.Mesh(
    new THREE.CylinderGeometry(radius,radius,0.5,8),
    new THREE.MeshLambertMaterial( {
       color: colorCharge, opacity: 1
    })
  );
  var a=angle*Math.PI/180;
  C.position.set(
    Math.cos(a)*distance,
    0.0,
    Math.sin(a)*distance
  );
  C.rotation.y=-a;
  C.rotation.z=Math.PI/2;
  C.castShadow=true;
  C.receiveShadow=true;
  return C;
}

// Add GUI elements for the motor coils:
sim.coilgui=[];
for (var i=0;i<2*sim.ncoil;i++) {
  var C=make_cylinder(0.5,1.4,sim.coilangle[i],sim.coil[i%sim.ncoil]);
  sim.coilgui[i]=C;
  scene.add(C);
}

// Add GUI elements for rotor:
sim.rotor.gui=new THREE.Group();
var N=make_cylinder(1.4,2.0,0.0,+1.0); 
var S=make_cylinder(1.4,2.0,180.0,-1.0); 
sim.rotor.gui.add(N);
sim.rotor.gui.add(S);
scene.add(sim.rotor.gui);

// Run simulator:
sim.rotor.update=function(dt) {
  var r=sim.rotor;
  
  for (var i=0;i<sim.ncoil;i++) {
    // Update coil color animation
    sim.coilgui[i].material.color.copy(
      make_color(sim.coil[i])
    );
    // complementary coils:
    sim.coilgui[2+i].material.color.copy(
      make_color(-sim.coil[i])
    );
    
    // Apply torques from coils
    var coil2rotor=100.0; // coil torque / rotor inertia
    var d=(r.angle-sim.coilangle[i])*Math.PI/180;
    var deltaV=coil2rotor*sim.coil[i]*Math.sin(d);
    r.velocity+=deltaV*dt;
    
    trace("sim.coil["+i+"]="+sim.coil[i].toFixed(2)
    	+" current -> "+deltaV.toFixed(2));
  }
  
  r.angle+=r.velocity*dt;
  r.angle=r.angle%360;
  r.velocity*=(1.0-0.2*dt); // damp out velocity
  
  trace("\nRotor angle (deg) and velocity (deg/sec)");
  trace(r.angle.toFixed(2));
  trace(r.velocity.toFixed(2));
  
  // Update GUI of rotor
  r.gui.rotation.y=-r.angle*Math.PI/180;
}

// Ground
sim.ground = new THREE.Mesh(
  new THREE.CubeGeometry(50,50,0.0001),
  new THREE.MeshLambertMaterial( {
     color: 0x228866, opacity: 1
  })
);
sim.ground.position.z=-2.5;  /* ground is at this Z */
sim.ground.receiveShadow=true;
scene.add(sim.ground);

// Sun-like spotlight (shadows help you see depth)
var l=new THREE.SpotLight();
sim.light = l;
l.position.set( -50, -100, 100 );
l.castShadow=true;
l.shadowCameraNear = 50; 
l.shadowCameraFar = 500; 
l.shadowCameraFov = 10; // degrees field of view
scene.add(l);