Improvement and analysis of cam-follower mechanism for a passive parallel lower limb exoskeleton

This project aims to explore the potential of utilizing green composite, consists of biobased polylactic acid (PLA) filled with vetiver filler, as backsheet to replace the Tedlar. Vetiver is a plant that shows promising benefits, it has a naturally antiseptic and cooling property that is traditionally used as a cooling screen. To prepare this backing layer (backsheet), the vetiver powder is mixed with 5 g of coconut oil as the plasticizer and a varying composition of polylactic acid (PLA) of 80% wt, 85% wt, 90% wt, 95% wt and 100% wt.

Exoskeletons function to augment, reinforce and restore human function while increasing the strength and durability of users. This project focuses on passive exoskeletons, which makes use of mechanical means to augment the capacity of load carrying of the user. An exoskeleton must also have the ability to match the walking gait of the person wearing it; to maintain correct posture of the body and to ensure comfort while wearing the exoskeleton. An effective exoskeleton design system should reduce the energy expended by the wearer during tasks and reduce the risk of developing musculoskeletal disorders. The project is based on the improvement and analysis of a cam-follower mechanism for a passive parallel lower limb exoskeleton. The design was proposed by a MSc student at Taylor’s University School of Computer Science and Engineering and succeeded by a final year project student at SCE. The design was inspired by the mechanism of a retractable pen. The objective of this research project is to determine the effectiveness of the cam-follower mechanism design in matching the natural human walking gait of the wearer of the exoskeleton and to also determine the effectiveness in reducing the exoskeleton wearer’s energy usage and to make improvements where needed. The cam-follower mechanism in the exoskeleton consists of a ridged bushing, annular cam, rod and a cam sleeve that is made up of three different blocks which are the top block, spacer block and the cam sleeve. The three blocks that form the cam sleeve when assembled is a housing for the annular cam, ridged bushing and spring while the rod slides into the space between the annular cam and ridged bushing and rotates about its axis and is attached to a foot unit that attaches the leg of the wearer.

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