Design and Analysis of a Compliant Constant-Torque Mechanism for Rehabilitation Devices

Abstract

Medical or healthcare devices assisting the rehabilitation of human joints often rely on functional mechanisms that could provide stable output torque. To achieve this target, available equipment usually uses motorized mechanisms combined with complicated sensorized control system. This paper presents a novel design concept of a monolithic compliant constant-torque mechanism (CTM). It could produce an output torque that does not change in a prescribed input rotation. Thanks to the monolithic nature of the compliant mechanism, the device is more compact, lightweight and portable regardless of sensors or actuators. However, to be used in the rehabilitation equipment, the mechanism must produce a stable output torque in a sufficiently wide range of operation. The design methodology of this compliant CTM uses a genetic algorithm shape optimization. After obtaining the optimal configuration, finite element analysis is used to verify the design. This chapter also proposes a general design formulation to find the CTMs with a certain constant output torque in a specified input rotation range that can be used for human joint rehabilitative devices or human mobility-assisting devices.