中文摘要：

自由摆利用旋转编码器测量摆杆角度变化，控制安装于摆杆末端的电机使平板保持稳定状态，保证放置在平板上的硬币不滑落；在平板上固定一激光笔，根据摆杆角度、方向、平板角度以及距靶子距离之间的三角函数关系，控制平板角度使激光笔照射在中心线上，在自由摆摆动时，利用PID算法来实现平板角度的控制，使激光笔始终照射中心线。实验数据表明：在控制平板转动过程中，其角度误差小于5°；摆杆在±60°范围内自由摆动，平板上的8枚硬币可保持叠放状态；在自由摆动过程中，激光笔照射点与目标偏移小于3cm。

英文摘要：

The system measures the angle change of the pendulum using the rotation encoder to control the motor mounted on the end of the pendulum in order to make the plate fixed on the motor shaft stable, ensures that the coins on the plate is stable. According to the trigonometric relation among the angle and direction of pendulum, the angle of the plate, and the distance between the pendulum and the point from a laser pointer fixed on the plate, the system controls the angle of the plate and makes the laser pointer irradiating on the center line. When the pendulum swings freely, the system uses the PID algorithm to control the angle of the plate, so that the laser pointer always irradiates on the center line. The experimental data show that the angle error is less than 5 ° during the rotation of the plate, 8 coins on the plate can be kept stacked state when the pendulum swing freely within the range of ± 60°, and the offset between the laser irradiation point and the target is less than 3 cm during pendulum free - swinging.