Spherical Parallel Manipulator Shoulder Exoskeleton

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Solution Overview

Problem

Conventional shoulder exoskeletons face inaccuracies and mechanical interference due to joint misalignment between the device and the user, particularly in complex joints like the shoulder, which requires both rotational and translational motion, and existing solutions like serial actuation suffer from low stiffness and high inertia.

Innovation Solution

A spherical parallel manipulator with a passive slip mechanism is used, featuring three linear actuators with two rotational and one translational degree of freedom, allowing for modular motion coupling and a spherical workspace centered on the user's shoulder, along with a passive cuff joint for translational and rotational slip to mitigate misalignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If serial actuation is used to accurately emulate shoulder motion, then positioning accuracy is improved, but stiffness decreases and inertia increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidstiffness

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The shoulder motion is segmented into spherical rotation components handled by the parallel manipulator and translational slip components handled by the passive degree of freedom. This segmentation allows the system to achieve accurate positioning through parallel actuation while maintaining high stiffness and avoiding the accumulation of positioning errors inherent in serial actuation chains.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A passive translational degree of freedom acts as an intermediary between the spherical parallel manipulator and the user's shoulder. This intermediary allows translational slip to occur, accommodating the mismatch between the spherical motion of the manipulator and the complex translational-rotational motion of the shoulder, thereby maintaining positioning accuracy without requiring the manipulator to directly control translational motion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a fully actuated 6-DoF parallel manipulator is used to control all degrees of freedom, then positioning accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of fully actuating all six degrees of freedom, the system applies partial action by using only three actuators to control the spherical rotation components. The remaining translational degree of freedom is left passive, allowing the system to achieve sufficient positioning accuracy for shoulder rehabilitation without the complexity of a fully actuated 6-DoF parallel manipulator.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The passive translational degree of freedom provides self-service by automatically accommodating translational misalignment between the manipulator and the user's shoulder. This eliminates the need for complex control systems to quantify and correct for joint misalignment, simplifying the overall device while maintaining positioning accuracy.

Inventive Principle:

Principle #25Self-service

3Device complexity

If conventional spherical parallel manipulator designs are used, then device complexity is reduced, but they cannot accurately handle the complex translational-rotational motion of the shoulder

Engineering Contradiction:

Improvedevice complexityVSAvoidmotion emulation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system transitions from a static spherical parallel manipulator design to a dynamic configuration by incorporating a passive translational degree of freedom. This allows the manipulator to adapt its configuration in real-time, maintaining accuracy in emulating the complex translational-rotational motion of the shoulder while keeping the device complexity manageable through the use of only three actuators.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10800031B2Spherical parallel manipulator architecture for shoulder robotic exoskeleton

Publication Date: 2020.10.13 THE ARIZONA BOARD OF REGENTS ON BEHALF OF THE UNIV OF ARIZONA

AI summary

Implementations involve a shoulder exoskeleton having a spherical parallel manipulator with a plurality of parallel linear actuators connected to a base coupled to a user's arm. A passive slip mechanism is operatively coupled to the spherical parallel manipulator as well as being coupled to the user's arm. The slip mechanism increases system mobility and prevents joint misalignment caused by the translational motion of the user's glenohumeral joint from introducing mechanical interference.