之后驱动臂通过弹簧拉动返回初始位置，此时驱动臂下面的小轮是滚动返回的，不产生相反的摩擦力。

The process is just like rowing a boat. And then, the driving arm return to the primary position by the pulling from the spring.

youdao

之后驱动臂通过弹簧拉动返回初始位置，此时驱动臂下面的小轮是滚动返回的，不产生相反的摩擦力。

The process is just like rowing a boat. And then, the driving arm return to the primary position by the pulling from the spring.

youdao