Design of a wearable shoulder exoskeleton robot with dual-purpose gravity compensation and a compliant misalignment compensation mechanism

This paper presents the design and validation of a wearable shoulder exoskeleton robot intended to serve as a platform for assistive controllers that can mitigate the risk of musculoskeletal disorders seen in workers. The design features a four-bar mechanism that moves the exoskeleton's center...

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Bibliographic Details
Published in:Wearable technologies 2024, Vol.5, p.e4, Article e4
Main Authors: Atkins, John, Chang, Dongjune, Lee, Hyunglae
Format: Article
Language:English
Subjects:
Center of mass
Compensation
Controllers
Degrees of freedom
Design
End effectors
Exoskeletons
Fatigue
Impedance
Injuries
Kinematics
Misalignment
Musculoskeletal diseases
Optimization
Performance Characterization
Range of motion
Robots
Shoulder
Torso
Wearable technology
Workers
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Summary:This paper presents the design and validation of a wearable shoulder exoskeleton robot intended to serve as a platform for assistive controllers that can mitigate the risk of musculoskeletal disorders seen in workers. The design features a four-bar mechanism that moves the exoskeleton's center of mass from the upper shoulders to the user's torso, dual-purpose gravity compensation mechanism located inside the four-bar's linkages that supports the full gravitational loading from the exoskeleton with partial user's arm weight compensation, and a novel 6 degree-of-freedom (DoF) compliant misalignment compensation mechanism located between the end effector and the user's arm to allow shoulder translation while maintaining control of the arm's direction. Simulations show the four-bar design lowers the center of mass by  cm and the kinematic chain can follow the motion of common upper arm trajectories. Experimental tests show the gravity compensation mechanism compensates gravitational loading within  Nm over the range of shoulder motion and the misalignment compensation mechanism has the desired 6 DoF stiffness characteristics and range of motion to adjust for shoulder center translation. Finally, a workspace admittance controller was implemented and evaluated showing the system is capable of accurately reproducing simulated impedance behavior with transparent low-impedance human operation.
ISSN:2631-7176
2631-7176
DOI:10.1017/wtc.2024.1