Design of a Wearable Walking Aid with Torsion Spring

Tan, Han Yuan (2022) Design of a Wearable Walking Aid with Torsion Spring. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Lower limb exoskeleton using robotic or pneumatic is not a new technology on the market, but the technology using torsion spring is rarely seen in the market.The rehabilitation and assisting humans in the work tasks are the two main goals of the lower limb extremities exoskeleton. Other than that, in order to using robotic or pneumatic actuator, torsion spring actuator will reduce cost and covenient for patient as it is just a simple and fully mechanical actuator. In this study, the actuation that discussed and design is torsion spring lower limb exoskeleton. To improve the performance of torsion spring, the shape of the torsion spring is design in circular shape with key at the outer part as it act as our human knee joint. The inner part is link with two member at the 180°. This is because this is the only design that had found which can rotate more than 10° with enough hardness. The torsion spring is design for support up to 60kg of user and able to bend about 120° which mean allow user to squad down their body. The main concept of it is when the user bend the knee, the energy will store in the member of torsion spring and release out when the leg is straighten. Finite Element Analysis is done by using Solidwork to do material and design testing, the Solidwork simulation is also done to know the design maximum von Misses stress and torsion spring rate. The conceptual design is drawn using Solidwork. Besides, different types of adjustments to the design were made, such as the relationship between the thickness of the coil, number of turn of coil, and the diameter of torsion spring to optimize the torsion spring. Other than that, a lot of calculation is done to get the optimum design of exoskeleton such as the diameter of the center shaft to withstand the torque generated, the ideal torsion spring, the number of torsion spring needed in the exoskeleton, and the thickness of the beam of the exoskeleton required to maintain the shape. The final design torsion spring have been design out. It able to rotate at 33° and the moment reaction is 101Nm. Finally, a set of complete lower limb exoskeleton have been designed out using Solidworks.