Read more about PID controller. The ball represent Wall-E. Click to Set the Target. Let's FLY! The Red Line represent the thrusters in X and Y(红线表示当前X和Y轴的动力), the Blue is the Velocity(蓝线为当前速度), the Green is the Acceleration(绿线是当前加速度). 2副图表分别表示X和Y方向上的PID分量变化曲线图。