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To increase the acceptability of exoskeletons, there is growing attention toward finding an alternative soft actuator that can safely perform at close vicinity of the human body. In this study, we investigated the capability of the dielectric elastomer actuators (DEAs), for muscle-like actuation of rehabilitation robots. First, an artificial skeletal muscle was configured using commercially available stacked DEAs arranged in a 3x4 array of three parallel fibers consisting of four DEAs connected in series. The shortening and force generation capabilities of this artificial muscle were then measured. An alternate 3x5 version of this muscle was mounted on the forearm of an upper extremity phantom model to actuate its elbow joint. The actuation capability of this muscle was then tested under various tensile loads, 1 N to 4 N, placed at the center of mass of the forearm+hand of the phantom model. The active range of motion and angular velocity of the phantom model's tip of the hand were measured using a motion capture system. The 3×4 artificial muscle produced 30.47 N of force and 5.3 mm of maximum shortening. The 3x5 artificial muscle was capable of actuating the elbow flexion 19.5º with 16.2 º/s angular velocity in the sagittal plane, under a 1 N tensile load. The active range of motion was substantially reduced as the tensile loads increased, which limits the capability of these muscles in the current upper extremity exoskeleton design.Wearable, mechanically passive (i.e. spring-powered) exoskeletons may be more practical and affordable than active, motorized exoskeletons for providing continuous, home-based, antigravity movement assistance for people with shoulder disability. However, the biomechanical moment due to gravity is a nonlinear function of shoulder elevation angle and, thus, challenging to counteract proportionally across the shoulder elevation range of motion with a spring alone. We designed, fabricated, and tested an integrated spring-cam-wheel system that can generate a nonlinear moment to proportionally compensate for the expected antigravity moment at the shoulder. We then incorporated the proposed system in a benchtop model and a novel wearable passive cable-driven exoskeleton that was intended to counteract half of the gravitational moment during shoulder elevation movements. The rotational moment measured from the benchtop model closely matched the theoretical moment during simulated positive shoulder elevation. However, a larger moment (up to 12.5% larger) was required during simulated negative shoulder elevation to stretch the spring to its initial length due to spring hysteresis and friction losses. The wearable exoskeleton prototype was qualitatively tested for assisting shoulder elevation movements; we identified several aspects of the prototype design that need to be improved before further testing on human participants. In future studies, we will quantitatively evaluate human kinematics and neuromuscular coordination with the exoskeleton to determine its suitability for assisting patients with shoulder disability.Individuals with neurological impairment, particularly those with cervical level spinal cord injuries (SCI), often have difficulty with daily tasks due to triceps weakness or total loss of function. More demanding tasks, such as sit-skiing, may be rendered impossible due to their extreme strength demands. Design of exoskeletons that address this issue by providing supplemental strength in arm extension is an active field of research but commercial devices are not yet available for use. Most current designs employ electric motors that necessitate the addition of bulky power sources and extraneous wiring, rendering the devices impractical in daily life. The possibility of powering an upper extremity exoskeleton passively has been explored, but to date, none have delivered sufficient function or strength to provide useful assistance for sit-skiing. We seek to rectify this with the design of a passively actuated exoskeletal arm brace capable of operating in two, adjustable-strength modes one for low level gravity compensation to aid in active range of motion, and the other for more stringent weight bearing activities. The mechanism developed through this paper allows for an affordable, lightweight, modular device that can be adjusted and customized for the needs of each individual patient.Work-related musculoskeletal disorders (MSDs) are a major concern in industries and working environments. They cause not only suffering to the employee and decrease in performance, but also high economic losses to the companies and the society. Workers from assembly lines and machine operators are one of the most frequently affected working population. Moreover, one of the main types of MSDs in occupational environments are shoulder injuries. Exoskeletons have been applied and tested in rehabilitation and they are gaining ground in occupational environments as assistive devices to augment human force and minimize loads on muscles and joints. However, more evidence about the effects of several exoskeletons models in assisting different tasks is needed. We measured shoulder muscles activity (AD - anterior deltoid and MD - medial deltoid) of seven automotive workers using the SuitX® upper limb exoskeleton while performing different screwing tasks, at different shoulder levels while handling different tools. We found significant muscle activity reduction for 2 of the 4 proposed tasks, suggesting a task-specificity effectiveness. Therefore, it seems to be a viable option to reduce muscle effort in certain tasks.In this study, we present a new design of a shoulder perturbation robot that can characterise the dynamics of the shoulder in two degrees of freedom. It uses two linear electric motors to perturb the shoulder joint in internal/external rotation and abduction/adduction, and force and position sensors to measure the corresponding torque and angular displacement about the joint. System identification techniques are used to estimate the dynamics of the muscles around the joint. AZD9291 The advantage our apparatus offers over the existing ones is that it can efficiently transfer torque to the joint and measure its dynamics separately with minimal interference from soft tissues. We verified that the apparatus can accurately estimate joint dynamics by conducting tests on a phantom of known properties. In addition, experiments were conducted on a human participant. It has been demonstrated that the measured dynamics of participant's arm are repeatable. The potential impact of our apparatus is to be used in clinic as a diagnostic tool for rotator cuff injuries.
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