DESIGN AND PRELIMINARY TESTING OF A SELF-CONTAINED KNEE PROSTHESIS WITH PNEUMATIC ACTUATION

For a powered lower limb prosthesis, a fundamental requirement is to provide the desired joint power and torque to support the amputee user's locomotion. Considering the limited weight and space, such requirement poses a significant challenge to the design of such prosthetic devices. In this paper, the design of a powered knee prosthesis is presented, which addresses this challenge by using a pneumatic actuator to power the prosthetic joint, leveraging the multiple advantages of this high-power-density actuator. Through kinetic calculation, the powered knee is able to provide sufficient torque in level walking and stair climbing for an 85 kg user, as demonstrated by a graphical comparison on the joint angle-torque plane. The prosthesis is also instrumented with multiple sensors and a servo valve to enable the locomotive control. Furthermore, a compressed air tank and a microprocessor-based controller are incorporated to form a self-contained prosthetic device ready for untethered use. Implementing a finite-state impedance control, the powered knee prosthesis is able to provide a natural walking gait as demonstrated in the treadmill walking experiments conducted on a human subject.