Redundant Kinematic Chain Decouples Hand Movement in Rehabilitation Robot
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Solution Overview
Problem
Current robotic arms for upper limb rehabilitation lack the ability to accurately reproduce a wide range of movements, particularly those involving the fingers, and do not adequately consider patient and therapist comfort and safety, as well as the need for precise control of resistance during Proprioceptive Neuromuscular Facilitation (PNF) training.
Innovation Solution
A robotic arm with a kinematic chain providing redundancy in the distal region, equipped with artificial muscle actuators and sensors, allowing for decoupled hand movement and precise control of forces, along with a mechanism for flexing and extending fingers, and integrated with virtual reality technology for enhanced training.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the robotic arm uses a standard kinematic chain without redundancy, then the structure is simpler and easier to control, but the hand movement cannot be decoupled from other parts of the kinematic chain, reducing patient comfort and safety
Solution Approach 1:
The robotic arm is divided into multiple modular segments (shoulder module, elbow module, wrist modules) that can independently control different degrees of freedom. This segmentation allows the hand grip position to be decoupled from the orientation movements of other segments, enabling the hand to remain stationary while the arm repositions itself, thereby improving patient comfort without excessive complexity
Solution Approach 2:
The robotic arm implements a 7-degree-of-freedom kinematic chain by adding redundancy in the wrist region (two wrist modules with multiple rotation axes each). This additional dimension allows independent control of hand position and orientation, enabling decoupling of hand movement from arm movement and providing more flexible operation for patient comfort
2Adaptability or versatility
If the robotic arm has limited degrees of freedom, then the device complexity is reduced, but the ability to accurately reproduce complex movements including finger movements is insufficient
Solution Approach 1:
The robotic arm is divided into multiple modular segments (shoulder module, elbow module, wrist modules) that can independently control different degrees of freedom. This segmentation allows the hand grip position to be decoupled from the orientation movements of other segments, enabling the hand to remain stationary while the arm repositions itself, thereby improving patient comfort without excessive complexity
Solution Approach 2:
The robotic arm implements a 7-degree-of-freedom kinematic chain by adding redundancy in the wrist region (two wrist modules with multiple rotation axes each). This additional dimension allows independent control of hand position and orientation, enabling decoupling of hand movement from arm movement and providing more flexible operation for patient comfort
3Measurement precision
If the robotic arm uses traditional actuators, then the control system is simpler, but the ability to provide precise resistance control during PNF training is limited
Solution Approach 1:
The robotic arm incorporates force sensors and position sensors that continuously monitor the interaction forces between the patient's arm and the robotic arm. This feedback is used by the control system to precisely regulate the resistance provided during PNF training, ensuring accurate force control while maintaining a manageable system complexity through sensor-integrated actuators
Data Source
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AI summary
A robotic arm (100) for controlling a movement of a user's arm, said robotic arm forming a kinematic chain extending from a proximal to a distal end and comprising a grip (190) for positioning said user's hand at a distal end, characterised in that the kinematic chain possesses redundancy in a distal region, such that the movement of the user's hand can de decoupled from other parts of the kinematic chain.