Development of Soft Pneumatic Actuator Based Wrist Exoskeleton for Assistive Motion

Exoskeletons are gaining traction for their use as motion assistive devices for human performance augmentation in occupational settings and rehabilitation in clinical settings. When considering upper body exoskeletons, soft robotic systems are more suitable due to their intrinsic compliance, lighter weight, and lower complexity in comparison to conventional rigid robotics. Regardless of many efforts to make soft robotic exoskeletons for the upper body, current marketed exoskeletons are only focused on the hand, and there is a need for development of this type of device for the wrist. This manuscript reports the design and development of a pneumatically driven wearable wrist exoskeleton made with hyperelastic materials. The exoskeleton is comprised of soft actuators using half-bellow architecture which can create bidirectional motion by applying pressure and vacuum. Two exoskeleton configurations are presented: (1) one actuator on either the dorsal or palmar side of the wrist and (2) two actuators with one on each side of the wrist. Simulation and experimental studies were performed to evaluate the range of motion and torque capabilities of the two configurations. The single actuator configuration produced a range of motion of 45 degrees flexion and 7 degrees extension when the actuator was on the dorsal side. Inverse angles were obtained when the actuator was on the palmar side. These ranges of motion and the torque produced by this configuration demonstrated its potential to assist in object manipulation and load bearing. However, it is still limited in bidirectionality, which may reduce its ability to assist in tasks that require both flexion and extension. The two-actuator configuration produced higher bidirectionality with 45 degrees flexion and 45 degrees extension range of motion, as well as sufficient torque for both directions. Therefore, this configuration has higher potential for assisting tasks in occupational, rehabilitation, and activities of daily living scenarios.