Preliminary Design and Experimental Studies of a Compliant Knee Joint for Pediatric Above Knee Amputees

This study presents a passive, self-actuated, 3D printed compliant knee joint for children in developing regions to decrease the overall expense of above knee prosthesis as well as increase the ease to print multiple prosthesis during their growing cycle. A single piece designed five-bar mechanism is proposed to provide adequate human-like gait instead of the traditional pegleg gait provided in previous rigid models. This gait is achieved through the use of both compliant links as well a novel 3D printed approach which is more accustomed to children because of the mechanism’s lightweight. In addition to the compliant knee joint, a compliant ankle possessing a flexure hinge placed at the toe is also designed to provide required bending during the gait cycle. The approach of using a fully passive knee joint enables to limit the weight of the prosthesis to create less of a burden to children and by isolating the need to utilize motors. A test bench consisted of a rack-pinion, two parallel rods, supports, and two servo motors are fabricated to experiment the performance of the knee joint. While the test bench is 3D printed using polylactic acid (PLA), the compliant knee joint is 3D printed in thermoplastic polyurethane (TPU) to emulate the gestures of a real human leg. Simulations are performed in Matlab Simscape to validate that the proposed knee joint mimics the human knee and desired angles.