A biomimicking design for mechanical knee joints

• Published in: Bioinspiration & biomimetics Vol. 13; no. 5; p. 056012
• Main Authors: Russell, Felix, Zhu, Yipeng, Hey, William, Vaidyanathan, Ravi, Ellison, Peter
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 02.08.2018
• Subjects: above knee prostheses; Biomechanical Phenomena - physiology; biomechanics; Biomimetic Materials - chemistry; biomimetics; Biomimetics - methods; condylar knee; Humans; Knee Joint - physiology; ligaments; lower limb; robotics; Stress, Mechanical; Walking - physiology
• ISSN: 1748-3190; 1748-3190
• DOI: 10.1088/1748-3190/aad39d

In this paper we present a new bioinspired bicondylar knee joint that requires a smaller actuator size when compared to a constant moment arm joint. Unlike existing prosthetic joints, the proposed mechanism replicates the elastic, rolling and sliding elements of the human knee. As a result, the moment arm that the actuators can impart on the joint changes as function of the angle, producing the equivalent of a variable transmission. By employing a similar moment arm-angle profile as the human knee the peak actuator force for stair ascent can be reduced by 12% compared to a constant moment arm joint addressing critical impediments in weight and power for robotics limbs. Additionally, the knee employs mechanical 'ligaments' containing stretch sensors to replicate the neurosensory and compliant elements of the joint. We demonstrate experimentally how the ligament stretch can be used to estimate joint angle, therefore overcoming the difficulty of sensing position in a bicondylar joint.