Posts Tagged Springs

[Abstract] Improving Healthcare Access: A Preliminary Design of a Low-Cost Arm Rehabilitation Device

Abstract

A low-cost continuous passive motion (CPM) machine, the Gannon Exoskeleton for Arm Rehabilitation (GEAR), was designed. The focus of the machine is on the rehabilitation of primary functional movements of the arm. The device developed integrates two mechanisms consisting of a four-bar linkage and a sliding rod prismatic joint mechanism that can be mounted to a normal chair. When seated, the patient is connected to the device via a padded cuff strapped on the elbow. A set of springs have been used to maintain the system stability and help the lifting of the arm. A preliminary analysis via analytical methods is used to determine the initial value of the springs to be used in the mechanism given the desired gravity compensatory force. Subsequently, a multibody simulation was performed with the software simwise 4D by Design Simulation Technologies (DST). The simulation was used to optimize the stiffness of the springs in the mechanism to provide assistance to raising of the patient’s arm. Furthermore, the software can provide a finite element analysis of the stress induced by the springs on the mechanism and the external load of the arm. Finally, a physical prototype of the mechanism was fabricated using polyvinyl chloride (PVC) pipes and commercial metal springs, and the reaching space was measured using motion capture. We believed that the GEAR has the potential to provide effective passive movement to individuals with no access to postoperative or poststroke rehabilitation therapy.

 

via Improving Healthcare Access: A Preliminary Design of a Low-Cost Arm Rehabilitation Device | Journal of Medical Devices | ASME Digital Collection

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[Abstract] An Elbow Exoskeleton for Upper Limb Rehabilitation With Series Elastic Actuator and Cable-Driven Differential

Abstract

Movement impairments resulting from neurologic injuries, such as stroke, can be treated with robotic exoskeletons that assist with movement retraining. Exoskeleton designs benefit from low impedance and accurate torque control. We designed a two-degrees-of-freedom tethered exoskeleton that can provide independent torque control on elbow flexion/extension and forearm supination/pronation. Two identical series elastic actuators (SEAs) are used to actuate the exoskeleton. The two SEAs are coupled through a novel cable-driven differential. The exoskeleton is compact and lightweight, with a mass of 0.9 kg. Applied rms torque errors were less than 0.19 Nm. Benchtop tests demonstrated a torque rise time of approximately 0.1 s, a torque control bandwidth of 3.7 Hz, and an impedance of less than 0.03 Nm/° at 1 Hz. The controller can simulate a stable maximum wall stiffness of 0.45 Nm/°. The overall performance is adequate for robotic therapy applications and the novelty of the design is discussed.

via An Elbow Exoskeleton for Upper Limb Rehabilitation With Series Elastic Actuator and Cable-Driven Differential – IEEE Journals & Magazine

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[Abstract] Hand rehabilitation after stroke using a wearable, high DOF, spring powered exoskeleton.

Abstract:

Stroke patients often have inappropriate finger flexor activation and finger extensor weakness, which makes it difficult to open their affected hand for functional grasp. The goal was to develop a passive, lightweight, wearable device to enable improved hand function during performance of activities of daily living. The device, HandSOME II, assists with opening the patient’s hand using 11 elastic actuators that apply extension torques to finger and thumb joints. Device design and initial testing are described. A novel mechanical design applies forces orthogonal to the finger segments despite the fact that all of the device DOFs are not aligned with human joint DOF. In initial testing with seven stroke subjects with impaired hand function, use of HandSOME II significantly increased maximum extension angles and range of motion in all of the index finger joints (P<0.05). HandSOME II allows performance of all the grip patterns used in daily activities and can be used as part of home-based therapy programs.

Source: IEEE Xplore Document – Hand rehabilitation after stroke using a wearable, high DOF, spring powered exoskeleton

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