A soft wearable elbow exosuit: design considerations

In this chapter we describe an alternative approach for assisting motion of the upper limbs using a wearable robotic device: designing a frame made of fabric (i.e., an exosuit) instead of metal reduces the weight, power requirements, and cosmetic impact of the system. Specifically, we focus on the design of an exosuit for assisting elbow movements. We start by identifying the major requirements that the device needs to fulfill to assist a subject in daily activities: these guide the mechanical design of the actuators, the choice of a Bowden cable transmission and the architecture of the suit. We propose a control paradigm to initiate and modulate the level of assistance and ensure high tracking accuracy of the joint in spite of the complex dynamics deriving from the device’s soft architecture. We show that wearing the exosuit results in an ≈50% reduction in muscular effort and that the proposed controller is able to tune the level of assistance according to the subject’s ability of movement, paving the way for a clinical application.