Design and development of a pneumatic powered lower limb exoskeleton for assistive mobility application

Abstract

Exoskeletons are built to be wearable and to improve human locomotion that increase the speed, strength and the endurance of the user. Singapore faces a rapid ageing population and a common disability among the elderly is their mobility. This project is to design and fabricate a lower limb exoskeleton, which can assist the elderly or rehabilitative patients in walking. The exoskeleton is designed to support the user’s lower limb during walking. The movement of the exoskeleton is to follow the human normal walking gait. The exoskeleton has been designed with the considerations of movements in the sagittal plane and assuming that the user still has the ability to balance and walk.

Pneumatics technology is selected for the actuation of the exoskeleton joints due to its robustness and high power density. Devices such as rotary actuators, directional valves, sensors and flow control valves are used to actuate and control the exoskeleton movements. The recommended pressure to use is 6 bars.

The design criteria are listed and function analysis is performed to generate the overall concept of the exoskeleton prototype. Various conceptual designs are introduced and discussed, and with the help of the morphological chart the most suitable design is selected. With the finalized conceptual design, embodiment designs are performed and finally a prototype is constructed.

Automation studio was used to design the ladder diagrams and incorporated with OMRON PLC to provide an operating system and the control of the electro-pneumatics devices.