Design and Simulation Compliance Mechanism for Lower Extremities Exoskeleton

Peng, Foo Guan (2021) Design and Simulation Compliance Mechanism for Lower Extremities Exoskeleton. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Lower limb extremity exoskeleton can be said to have two main objectives which is the rehabilitation and helping human on work activities. According to the objectives, to improve the lower limb extremities especially in the location of actuators because the current is that using compliance mechanism and replacing hydraulic and pneumatic actuator will help to reduce cost, the weight for the wearable to wear and will simplify compare to the spring actuator. Moreover, the current design is only able to support a weight of 60kg human when walking. Then, the transfemoral lower extremity exoskeleton joints are developed as one of the enhancements on the overall structure of the transfemoral actuator. The knee joints are typically designed to mimic the flexion-extension motion of biological knees during human locomotion. While the knee joints required to provide sufficient rotation for locomotion, it also required to support the human body weight during knee flexion extension. Current lower extremity exoskeleton joints available are all rigid link mechanisms knee joints. However, the rigid link designs of current lower extremity exoskeleton joints subject to various limitations such as the wear and backlash of interconnection parts could result in the short lifespan of expensive knee joints. Besides that, to improve the rigid rink design, a compliance mechanism was discussed in the report because it has a lot of advantages compared to hydraulic and pneumatic actuators. Finite element analysis was discussed to be used when doing simulation to know the tensile strength and tensile force of the spring actuator. Solidworks was used to draw the lower limb extremities. Modification and optimization such as relative position, radius of curvature, type of material, number of holes and thickness of centre circle were carried out to the spring actuator in order to have perfect final iris spring. Two different sets of lower extremity exoskeleton were design for the wearable.