To conquer the problem of lack of direct torque in the under-actuated systems such as single wheel robots missiles satellites and spacecrafts

a device of torque generation is proposed in this paper.The research results are acquired under the theory of classic electromagnetism

and the details of the mechanism of the device are explained.The torque provided by the proposed mechanism is proportion to the speed

so it is rather convenient to perform exact control by motors.The experiments carried out on single wheel robot's lateral and yaw control respectively are included to demonstrate the superior performance the proposed method over some traditional ones

which illuminating the promising practical application potentiality of under-actuated systems.