PD control

by jmcjc5u

HTML

<div id="info">PD Control
  <br> Left click to choose reference
</div>
<script src="https://threejs.org/build/three.min.js"></script>

CSS

#info {
  position: absolute;
  top: 0px;
  width: 100%;
  padding: 10px;
  text-align: center;
  color: #ffff00
}

body {
  overflow: hidden;
}

JavaScript

var camera, scene, renderer;
var point;
/////////////////////
const KP = 150;
const KD = 20;
var yy, vv;
var gravity = true;
var yref = -2;
(function() {
  Math.clamp = function(val, min, max) {
    return Math.min(Math.max(val, min), max);
  }
})();

init();
animate();

function init() {
  renderer = new THREE.WebGLRenderer({
    antialias: true
  });

  renderer.setSize(window.innerWidth, window.innerHeight);
  renderer.setClearColor(0x888888);
  document.body.appendChild(renderer.domElement);

  scene = new THREE.Scene();
  camera = new THREE.OrthographicCamera(-10, 10, 10, -10, -10, 100);
  camera.position.z = 10;

	//////////////////////////////////////////////////
	let points = [];
  
	points.push(
    new THREE.Vector3(-4, 0, 0),
    new THREE.Vector3(4, 0, 0));
	
  let geometry = new THREE.BufferGeometry().setFromPoints (points);
  
  let border = new THREE.Line(geometry, new THREE.LineBasicMaterial({
    color: 0x0000ff
  }));
  border.rotation.z = Math.PI/2;
  scene.add (border);

  point = new THREE.Mesh(new THREE.CircleGeometry(0.4, 10),
    new THREE.MeshBasicMaterial({
      color: 0xff0000,
    }));
  scene.add(point);

  window.addEventListener('pointerdown', onDocumentMouseDown, false);
	yy = 0;
  vv = 0;
}

function onDocumentMouseDown(event) {
  event.preventDefault();
  // NDC: [-1,1]x[-1,1]
  //mouse.x = (event.clientX / window.innerWidth) * 2 - 1;
  //mouse.y = -(event.clientY / window.innerHeight) * 2 + 1;

	yref = 10 - 20*event.clientY/window.innerHeight;
  
  yref = Math.clamp (yref, -4, 4);
}

function controlLaw () {
	let u = KP*(yref - yy) - KD*vv;
  return u;
}

function animate() {
	
	var f = controlLaw();
	if (gravity) 
  	f += (-20.8);
    
  // plant dynamics
  let dt = 0.01;
  vv += f*dt;
  yy += vv*dt

	point.position.y = yy;
  
	requestAnimationFrame(animate);
  render();
}

function render() {
  renderer.render(scene, camera);
}