Research Papers

A Novel Shoulder Exoskeleton Robot Using Parallel Actuation and a Passive Slip Interface

[+] Author and Article Information
Justin Hunt

School for Engineering of Matter,
Transport and Energy,
Arizona State University,
Tempe, AZ 85287
e-mail: justin.p.hunt@asu.edu

Hyunglae Lee

School for Engineering of Matter,
Transport and Energy,
Arizona State University,
Tempe, AZ 85287
e-mail: hyunglae.lee@asu.edu

Panagiotis Artemiadis

School for Engineering of Matter,
Transport and Energy,
Arizona State University,
Tempe, AZ 85287
e-mail: panagiotis.artemiadis@asu.edu

1Corresponding author.

Manuscript received May 23, 2016; final manuscript received October 19, 2016; published online November 23, 2016. Assoc. Editor: Jun Ueda.

J. Mechanisms Robotics 9(1), 011002 (Nov 23, 2016) (7 pages) Paper No: JMR-16-1149; doi: 10.1115/1.4035087 History: Received May 23, 2016; Revised October 19, 2016

This paper presents a five degrees-of-freedom (DoF) low inertia shoulder exoskeleton. This device is comprised of two novel technologies. The first is 3DoF spherical parallel manipulator (SPM), which was developed using a new method of parallel manipulator design. This method involves mechanically coupling certain DoF of each independently actuated linkage of the parallel manipulator in order to constrain the kinematics of the entire system. The second is a 2DoF passive slip interface used to couple the user upper arm to the SPM. This slip interface increases system mobility and prevents joint misalignment caused by the translational motion of the user's glenohumeral joint from introducing mechanical interference. An experiment to validate the kinematics of the SPM was performed using motion capture. The results of this experiment validated the SPM's forward and inverse kinematic solutions through an Euler angle comparison of the actual and command orientations. A computational slip model was created to quantify the passive slip interface response for different conditions of joint misalignment. In addition to offering a low inertia solution for the rehabilitation or augmentation of the human shoulder, this device demonstrates a new method of motion coupling, which can be used to impose kinematic constraints on a wide variety of parallel architectures. Furthermore, the presented device demonstrates a passive slip interface that can be used with either parallel or serial robotic systems.

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Fig. 1

The SPM design. Conceptual model illustrating interface with user (top). Prototype (bottom).

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Fig. 2

Examples of alternative base mount configurations

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Fig. 3

Actuator pitch and stroke coupling using similar triangle relation

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Fig. 4

Actuator pitch and stroke coupling with offsets r′ and d′ to avoid mechanical interference

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Fig. 5

Motion coupled actuator. Conceptual model (top) with the following components: (A) motor, (B) custom gearbox, (C) pitch/stroke encoder, (D) roll measurement potentiometer, (E) wormscrew, (F) pitch/stroke coupling linkage, (G) pitch control slider, (H) enclosed limit switches, (I) tie rod joint, and (J) enclosed powerscrew and slider for linear actuation. Developed prototype (bottom).

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Fig. 6

Chosen exoskeleton shoulder orientation for given arm directions

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Fig. 7

Upper arm slip mechanism for joint misalignment

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Fig. 8

Upper arm slip mechanism with joint misalignment in 3D space

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Fig. 9

Error between the actual and commanded shoulder orientation expressed using the z–x–z Euler angles α, β, and γ, respectively

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Fig. 10

Maximum translation slip Smax of the cuff for given planar misalignment vmis

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Fig. 11

Maximum cuff misalignment angle ωmax for given planar misalignment vmis




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