A Continuum Exoskeleton for Upper Extremity
September 2010 to present
Exoskeleton research attracted a lot of attentions in the past decades. Numerous exoskeleton systems were developed for upper and lower limbs for military and medical purposes. These exoskeleton systems either aim at augmenting a healthy wearer’s physical capabilities with robotic actuation or to allow rehabilitation for neuromuscular defects after stroke or injury.
Despite their different applications in military or medicine, many existing exoskeleton systems yet followed one similar design approach: using different control and sensing schemes, rigid kinematic chains are actuated to mobilize an attached human wearer. The use of rigid links in an exoskeleton might be justified in applications for strength augmentation to undertake excessive external loads and shield the wearer. But the use of rigid links introduced drawbacks such as bulkiness, high inertia, and most importantly the difficulty of maintaining kinematic compatibility between exoskeleton and human anatomy. In a clinical setting for rehabilitation where one exoskeleton consisting of rigid links is shared by multiple patients, it is even more difficult to guarantee the on-site adjustments performed by therapists can make the rigid exoskeleton fit each individual patient perfectly. Hence design approaches of using non-rigid components could be explored.
This project covers design concepts, kinematics, actuation, transmission scheme, shape identification, and manikin trials of the continuum shoulder exoskeleton as shown in the figure. Backbones in the continuum brace were pushed and pulled to orient an arm sleeve and so to assist a patient with upper arm motions. During the assisted motions, the continuum exoskeleton was deformed and passively adapted to different anatomies because of its intrinsic flexibility. Although shapes of the exoskeleton were different for different anatomies, the same actuation was able to assist the anatomically different upper arms with similar motions. This is particularly advantageous for its application in a clinical setting. When the exoskeleton is shared by a group of patients, without performing any hardware adjustments, the exoskeleton can match each patient’s anatomy passively and assist his/her upper arm motion. During assisted motions, no firm attachment between the arm sleeve and the arm is needed. When the arm sleeve is oriented by the shoulder brace, the arm rests in the sleeve naturally, preventing the exoskeleton from exerting excessive forces on the shoulder joint. In other words, the proposed design could potentially provide safe and effective rehabilitation to a group of anatomically different patients in an operation-friendly manner.