A power switching structure includes an input shaft, a detection shaft sleeve fit over the input shaft, an assisting power assembly, and an output assembly selectively drivable by the input shaft and the assisting power assembly. The output assembly includes first and transmission sleeves rotatably mounted to the input shaft. The assisting power assembly includes a power member rotatably mounted to the second transmission sleeve. A one-way bearing is arranged between the first and second transmission sleeves and the power member. An output member is mounted on the second transmission sleeve. A micro-motion static frictional force is induced between the first and second transmission sleeves and the input shaft to allow the detection shaft sleeve to directly and accurately measure a torque value of the input shaft. The one-way bearing arranged between the first and second transmission sleeves and the power member allows for selection among sources of power.