Cable-Actuated Exoskeleton Joint Actuator for Natural Ankle Gait
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Solution Overview
Problem
Individuals with muscle control disorders experience reduced physical activity and worsening gait function, leading to a decline in ambulatory ability, necessitating improved methods and devices for gait rehabilitation.
Innovation Solution
A cable-actuated, kinetically-balanced, parallel torque transfer exoskeleton joint actuator with a rotatable bearing and transmission linkage, mounted on the distal side of the calf, providing assistance or resistance to ankle motion through Bowden cables and a pulley system, eliminating medial interference and enhancing gait stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the actuator and transmission components are mounted on the medial side of the leg, then the gait rehabilitation function is provided, but the hardware interferes with the user's natural gait
Solution Approach 1:
The patent extracts the actuator and transmission components from the medial side of the leg and relocates them to the lateral side. This separation removes the harmful interference from the gait path while preserving the rehabilitation function, as the lateral mounting position does not obstruct the natural walking motion.
Solution Approach 2:
The patent introduces an extended tubular structural member as an intermediary carrier that houses the bearing and transmission components. This intermediary structure allows the components to be positioned laterally on the leg without directly interfering with gait, while still transmitting the necessary mechanical forces for rehabilitation.
2Stability of the object's composition
If a rigid structural member is used to support the bearing and transmission components, then structural stability is improved, but the weight of the device increases
Solution Approach 1:
The patent specifies that the extended tubular structural member is made from carbon fiber reinforced polymer composite material. This composite material provides high structural stability and stiffness while maintaining low weight, thus resolving the contradiction between structural stability and device weight.
Solution Approach 2:
The patent employs a thin-walled tubular structural member with optimized wall thickness and cross-sectional geometry. This design provides sufficient structural stability to support the bearing and transmission components while minimizing the amount of material used, thereby reducing overall device weight.
3Use of energy by moving object
If the pulley sheave is larger than the tubular member opening, then the cable transmission efficiency is improved, but the assembly complexity increases
Solution Approach 1:
The patent segments the pulley sheave into multiple parts, with the sheave body being removable from the tubular member. This segmentation allows the larger-diameter sheave to be assembled through the opening by separating it into manageable segments, reducing assembly complexity while maintaining the efficient cable transmission performance of the larger sheave diameter.
Solution Approach 2:
The patent designs the pulley sheave to be nested within or pass through the tubular structural member. The sheave is configured to fit through the opening during assembly, then positioned and secured within the tubular member, allowing the larger sheave to be integrated into the compact tubular structure without increasing overall device complexity.
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 exoskeleton device improves walking ability and reduces metabolic cost by providing timely assistance and resistance, maintaining range of motion and muscle strength, and facilitating rehabilitation.
Implementation Method 1
A rotatable bearing is mounted within the member, and is rotatable by a pulley connected to the cables
Implementation Method 2
The bearing is coupled to a footplate, and is rotatable in a plantar direction or a dorsal direction depending on the tension applied to the cables by the actuator
Data Source
AI summary
A low-weight, high performance wearable assistive device for assisting motion of a joint of a wearer (e.g., an ankle) and/or resistance training of motion of the joint includes a lightweight upright member that may be attached to the wearer (e.g., fastened to the wearer's outside calf). Forces to assist or resist movement of the joint are coupled to a rotation bearing via cables. The bearing is disposed within the upright member such torsional deflection of the device under load is reduced, allowing the upright member to be lighter and/or less obtrusive to the wearer and less susceptible to failure.