数字PID控制示例，原来是这样！以液位控制为例

var i = PID();//根据PID控制算法输出电流信号，用于控制闸阀
var maxA = 3;
i = Math.max(Math.min(i, maxA), -maxA);
if (Math.abs(i) < 0.001) {
  i = 0;
}

volume=0.99*volume+i*2;//这一刻留出了原来1%的体积，并灌入了2i的水,注水量正比于控制电流i
y += v/3.14/1/1;//增加的液位高度是体积除以半径1的底面积

function PID() {
  var error = setpoint - lastLastY;
  integral += error;

  if (integral < -windup) {
    integral = -windup;
  } else if (integral > windup) {
    integral = windup;
  }

  var derivative = error - prevError;
  prevError = error;

  lastLastY = lastY;
  lastY = y;

  return 0.001 * (kp * error + ki * integral + kd * derivative);
}