Joint Assembly with External Pivot Axis for Walking Assistant Robot
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Solution Overview
Problem
Conventional walking assistant robots face challenges in mimicking the complex movements of the human ankle joint, particularly in maintaining stability and preventing unnecessary load on the user's ankle joint during pivot operations, especially when pivoting in the second direction.
Innovation Solution
The joint assembly includes a first joint unit for plantar-flexion/dorsi-flexion and a second joint unit for inversion/eversion, with a third joint unit and link units configured to maintain a consistent distance and pivot around a rotation axis outside the ankle joint, allowing parallel movement of links to mimic the user's ankle joint movements, thereby maintaining contact with the user's body and distributing load effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the joint assembly uses a simple pivot mechanism, then the device complexity is reduced, but the ability to mimic complex ankle joint movements deteriorates
Solution Approach 1:
The ankle joint is divided into two independent joint units: a first joint unit for plantar-flexion/dorsi-flexion movements and a second joint unit for inversion/eversion movements. Each joint unit can operate independently, allowing the system to simulate complex ankle movements through combination of simpler movements, thereby reducing overall device complexity while maintaining movement simulation capability.
Solution Approach 2:
The first and second joint units are combined within a single ankle joint assembly that integrates both degrees of freedom. The parallel linkage structures of both joint units share common components such as the foot structure and frame, merging multiple functions into a unified assembly that maintains complexity while enabling versatile movement simulation.
2Device complexity
If the joint assembly pivots around an axis inside the ankle joint, then the structure is simplified, but the stability and load distribution deteriorate
Solution Approach 1:
The assistant link acts as an intermediary element that connects the first and second link units while maintaining a constant distance between them. This intermediary structure ensures that the parallel linkage mechanism maintains proper geometric relationships during pivot operations, stabilizing the system and distributing loads effectively without requiring the pivot axis to be located inside the ankle joint.
Solution Approach 2:
The assistant link maintains a constant distance between the first and second link units, ensuring that both link units operate at equivalent positions relative to the rotation axis. This equipotential configuration ensures uniform load distribution and maintains stability during pivot operations, as both link units experience similar mechanical conditions throughout the movement cycle.
3Reliability
If the assistant link maintains constant distance between link units, then the stability is improved, but the device complexity increases
Solution Approach 1:
The assistant link maintains a constant distance between the first and second link units, ensuring that both link units operate at equivalent positions relative to the rotation axis. This equipotential configuration ensures uniform load distribution and maintains stability during pivot operations, as both link units experience similar mechanical conditions throughout the movement cycle.
Solution Approach 2:
The constant distance maintenance function is segmented into two separate assistant links (first assistant link and second assistant link), each responsible for maintaining distance between specific link units. This segmentation allows the complex constraint to be distributed across multiple simpler linkage elements, reducing the complexity of any single component while maintaining overall system stability.
Data Source
AI summary
According to an aspect of the present invention, it is possible to implement a joint assembly operating similar to a user's actual ankle joint. An ankle joint included in a walking assistant robot is pivotable around a rotation axis located outside the ankle joint.