On an active prosthetic knee joint driven by a high thrust force helical motor

A variety of prosthetic legs are developed and some of them have electric motors controlled by the computer, which have drawback in terms of their weight, power consumption and so on. We are developing a high thrust force linear actuator with helical shaped mover and stator, which help generate high thrust force in spite of the compact size. Magnetic flux of the permanent magnet and windings cause the mover levitate, which can relieve loss of friction. In this paper, the prosthetic knee joint driven by a high thrust helical motor is proposed. To develop the helical motor applicable to the prosthetic knee joint, we designed a very thin lead-length helical motor. FEA simulation shows that continuous rated thrust force is approximately 101N. In addition, 662N of thrust force can be generated if the space factor of windings and the continuous rated current density can be improved. Moreover, the short-time allowable current can be flowed several times of the continuous rated current. This value shows that there is a potential to achieve the walking motion by the prosthetic knee joint driven by the high thrust force helical motor.