Actuation design and assistive control for a soft wearable exosuit

The development of a portable assistive device to aid patients affected by neuromuscular disorders has been the ultimate goal of assistive robots since the late 1960s. Traditional robotic devices have been engineered to assist the users' limbs in both activities of daily living (ADLs) and physical therapy, mostly consisting of load-bearing exoskeletons made of rigid links that operate in parallel to the human skeleton. These devices can be extremely accurate and are able to deliver high forces/torques to their users, making them optimal solutions for improving physical therapy in clinical environments. However, their structural complexity cause them to be poor candidates for daily at-home use, where portability, lightweight, compliance, and low profile are preferable. A new frontier of assistive devices aims at designing exoskeletons based on fabric and flexible materials for applications where kinematic transparency is the primary requirement. Bowden-cable transmission is the widely employed solution in most of the aforementioned applications due to advantages in durability, lightweight, safety, and flexibility. The major advantages of soft assistive exoskeletons driven by Bowden-cable transmission can be identified in the superior ergonomics and wearability, allowing users to freely move and allocating the actuation stages far away from the end effector. Despite of having many advantages in assistive technology, this actuation strategy presents several intrinsic limitations caused by the presence of nonlinearities, such as friction and backlash of the cables, which make it difficult to predict and control the kinematics and dynamics between the device and the user. In this thesis, I present the design and control implementation of a soft, textile-based exosuit driven by Bowden-cable transmission for assisting human upper limb movements, especially elbowflexion/extension. I describe a model-based design, characterisation and testing of an actuation stage, driving a set of artificial tendons to apply torques to the human elbow joint. I also propose a novel hierarchical control paradigm for the actuation unit, considering all the aspects ranging from human motion intention detection for assistance, to adaptive compensation for the detrimental effects arising from the presence of nonlinear behaviours in the exosuit, i.e. friction and backlash. The resulting system is a low profile, lightweight, wearable exosuit with high accuracy, designed to intuitively assist the wearer in activities of daily living.Doctor of Philosophy (MAE