Arm Support Exoskeleton With Position-Dependent Torque Relief
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Solution Overview
Problem
Existing arm support devices fail to automatically reduce assistance when the user rests their arm or picks a tool from their belt, leading to continuous lifting forces that inhibit motion and cause discomfort during non-working postures.
Innovation Solution
An arm support exoskeleton with a shoulder base, arm link mechanisms, and torque generators that adjust torque based on arm position, allowing zero or minimal torque when the arm is lowered, enabling free motion and reduced discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If passive support devices continuously apply lifting forces to support the arm weight, then the shoulder forces and torques are reduced during arm elevation, but the devices inhibit motion and create discomfort during non-working postures when assist is not desired
Solution Approach 1:
The torque generator dynamically adjusts the support torque based on arm position. When the arm is in working positions (below horizontal), the device provides full support torque to reduce shoulder load. When the arm reaches horizontal or higher positions (non-working postures), the torque automatically reduces to zero, allowing free motion without impedance. This dynamic adaptation resolves the contradiction between providing continuous support and enabling free motion during rest.
Solution Approach 2:
The device changes the torque parameter based on arm elevation angle. The torque generator is configured to provide maximum support torque when the arm is below horizontal position, and automatically reduces torque to zero when the arm reaches or exceeds horizontal position. This parameter change enables the device to adapt its assistance level to match the user's operational needs versus rest needs.
2Productivity
If passive support devices provide continuous lifting assistance, then arm elevation is facilitated, but the devices cannot automatically reduce assistance when the user intends to rest the arm or pick a tool from the tool belt
Solution Approach 1:
The torque generator is designed with dynamic torque adjustment capability that automatically adapts to different arm positions. The device transitions from providing full support torque during arm elevation (productivity mode) to zero torque when the arm is in rest positions (adaptability mode). This enables the device to serve both productivity and adaptability requirements without manual intervention.
Solution Approach 2:
The device incorporates position-dependent feedback where the arm angle relative to horizontal serves as the feedback signal. When the arm position sensor detects that the arm has reached or exceeded horizontal position, the system automatically reduces torque to zero. This feedback mechanism enables automatic adaptation to user intentions (rest or tool retrieval) without requiring separate controls.
3Force
If the torque generator provides support torque for arm elevation, then shoulder forces are reduced, but the device creates impedance during non-working postures where zero torque is desired
Solution Approach 1:
The torque generator automatically changes the torque parameter from a non-zero value during arm elevation to zero during non-working postures. When the arm position indicator shows the arm is at or above horizontal level, the torque generator reduces support torque to zero, eliminating the harmful impedance effect while maintaining the beneficial support effect during working positions.
Solution Approach 2:
The device dynamically adjusts the torque output based on real-time arm position detection. The system transitions between two distinct operational states: a support state with non-zero torque for arm elevation, and a free-motion state with zero torque for non-working postures. This dynamic state change eliminates the harmful impedance during rest while preserving the useful support during work.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides reduced shoulder forces and torques during arm elevation, allowing for comfortable free motion and zero impedance during non-working postures by automatically adjusting torque based on arm position.
Implementation Method 1
The torque generator provides a torque between the proximal link and the distal link
Data Source
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AI summary
An arm supporting exoskeleton comprises a shoulder base coupled to an arm link mechanism. The arm link mechanism comprises a proximal link and a distal link configured to rotate relative to each other about a rotating joint; at least one arm-coupler adapted to couple a user's arm to the distal link; a tensile force generator coupled to the proximal link and the distal link, and providing a torque to flex the distal link relative to the proximal link; and a protrusion located substantially at the rotating joint. When the distal link extends past a toggle angle, the protrusion constrains the tensile force generator, and the torque provided by the tensile force generator remains substantially small. When the protrusion does not constrain the tensile force generator, the torque tends to flex the distal link relative to the proximal link, thereby reducing human shoulder forces and torques required to raise the user's arm.