Design and Fabrication of a Lightweight and Wearable Semi-Rigid Robotic Knee Chain Exoskeleton

Abstract With the population of people affected by lower limb disability and physical impairments continuing to grow, engineers in response have begun to develop exoskeletons designed to assist and rehabilitate those in need. While there have been great strides and advancements in the development of exoskeletons, many of them are still too cumbersome, heavy, and expensive for most people. The project described in this paper aims to design and manufacture a wearable robotic knee exoskeleton that helps solve some of the drawbacks that exoskeletons have today. The exoskeleton is designed with lightweight and durable three-dimensional (3D)-printed PETG, TPU, and PLA components combined with soft, flexible, and wearable materials to achieve improved human–robot interaction while providing support when bending and extending the knee joint. The three main assemblies designed in this project were a 3D-printed semirigid knee chain, a 3D-printed flexible shin brace, and a motor actuator assembly mounted on a carbon fiber back plate. The semirigid knee chain is actuated using a Bowden cable which allows the heavy motor to be relocated onto the user's back. solidworks topology optimization and finite element analysis (FEA) were used to reduce weight while keeping the overall strength of the chain and ensuring the safety factor of 2. The exoskeleton was observed to be able to withstand applied torques of up to 29 N·m during the walking functionality test. This exoskeleton is also designed to be integrated into a larger hip exoskeleton system.