The OpenXO. 3D Printed Modular Exoskeleton Segment

Abstract: Exoskeletons are wearable devices that enhance or supplement the user’s natural abilities. They have been demonstrated to be efective in alleviating pain, reducing work related injuries, improving working conditions, and can play a pivotal role in improving recovery times and recovery outcomes. Commercial exoskeletons are expensive, specialised and not easily accessible to the average user. This thesis describes the design and manufacturing processes for the OpenXO, an open-source knee exoskeleton. The focus of the thesis is the design and manufacture of the exoskeleton drive system. It implements a cycloidal drive design. Additionally, a method of designing tapered crossed roller bearings was developed that allows for easy integration into elements of the drive system. The open source aspect is further supported by designing the OpenXO around commercially available additive manufacturing technologies. Rapid prototyping and iterative test-based design methods were used in conjunction with empirical testing and validation of both the design and manufacturing methods. Performance validations were conducted on an unpowered exoskeleton. The tests focus on ease of use and comfort. Validation on the exoskeleton and its components was performed at various stages during the design process. The resulting drive design was signifcantly lighter than commercially available solutions. The stator design implemented allows for press ft accuracy between the rotor and stator while allowing for smooth rotation. The fully assembled exoskeleton was tested by 5 individuals. All participants performed tasks to test the usability the exoskeleton in common day to day activities. The participants managed to perform several tasks with ease. However, the exoskeleton was prone to misalignment in specifc circumstances. Gait analysis on a user wearing the exoskeleton shows that the exoskeleton does infuence gait patterns. However, the user does not experience signifcant impact on their perceived range of motion. These tests do not demonstrate the efectiveness of the exoskeleton when it comes to powered assistance. Further work is needed to test and validate the powered assist functionality of the exoskeleton.