Orthogonal Drive Exoskeleton for Shoulder Kinematic Alignment
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Solution Overview
Problem
Existing arm therapy systems, particularly exoskeleton-type devices, face challenges in accurately mimicking human shoulder joint kinematics, leading to misalignment and instability, especially during larger motions, and lack adaptability for left/right arm use and varying body sizes.
Innovation Solution
A system with a second drive oriented orthogonally to the first drive, using a hinged profile for easy switching between arm uses, and incorporating weight compensation and laser guidance for precise anatomical alignment, allowing for a statically determined exoskeleton with correct anatomical axes and misaligned technical axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an exoskeleton-type device with one degree-of-freedom movement for the glenohumeral joint is used, then the device is cost-effective and anatomically correct, but it cannot be easily converted for left/right use and lacks shoulder guidance
Solution Approach 1:
The device employs asymmetric design elements that allow configuration for either left or right arm therapy. The shoulder guidance mechanism and exoskeleton structure can be mirrored or adjusted to accommodate different sides, enabling versatility while maintaining cost-effectiveness through standardized components
Solution Approach 2:
The device incorporates dynamic adjustment capabilities that allow the shoulder guidance and exoskeleton configuration to be changed between left and right arm use. This dynamic reconfigurability enables a single device to serve multiple purposes without requiring complete redesign
2Device complexity
If the human shoulder joint is simplified to a three degree of freedom ball and socket joint, then the robot structure is simplified, but misalignment between robot and human limb occurs during larger motions
Solution Approach 1:
The shoulder complex is segmented into two interconnected subsystems: the shoulder girdle (sternum/thorax/torso, clavicle, scapula) and the glenohumeral joint (humerus connecting to scapula). This segmentation allows each subsystem to be modeled and controlled separately, improving kinematic accuracy during large motions while maintaining manageable system complexity
Solution Approach 2:
The invention accounts for the third dimension of shoulder movement by incorporating scapular rotation and clavicular movement in addition to glenohumeral joint rotation. This multi-dimensional approach captures the complex kinematics of shoulder elevation, which cannot be achieved by a simple three-degree-of-freedom ball-and-socket model alone
3Force
If high torques are applied to overcome spastic resistance in the elbow joint, then elbow movement is achieved, but reaction forces in the shoulder joint can cause humerus head dislocation
Solution Approach 1:
The shoulder guidance acts as an intermediary mechanism between the exoskeleton and the patient's shoulder. It provides stable support and proper positioning of the humerus head in the glenoid cavity, preventing dislocation while allowing the transmission of necessary torques for elbow movement. The guidance mechanism absorbs and distributes reaction forces, protecting the unstable shoulder joint
Data Source
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AI summary
A system for arm therapy comprises a first drive (M2) that can be fixedly connected to an element (10) determining the position of a user (19) and rotationally driving, about a first axis (A2), a part (21, 22, 23, 24, 25, Ml, 26) of the arm therapy system which can be connected to an upper arm module (26, M3, M4). The driven part of the arm therapy system comprises a second drive (M1) adapted to rotationally drive said upper arm module (26, M3, M4) about a second axis (A1), wherein said second axis (A1) is oriented orthogonal to the first axis (A2). The system can provide a statically determined exoskeleton with correct anatomical axes and misaligned technical axes.