Mid-wheel Drive Wheelchair Linkage for Obstacle Navigation
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Solution Overview
Problem
Mid-wheel drive electric wheelchairs face challenges in stability, traction, and comfort when navigating obstacles and uneven surfaces, particularly in climbing and descending curbs, due to limited capability to maintain all wheels in contact with the ground.
Innovation Solution
The wheelchair design features a chassis with pivotally connected front and rear link arms, a coupling mechanism between the link arms to ensure all wheels remain in contact with the ground, and adjustable shock absorbers for enhanced traction and comfort, utilizing a minimal number of components for simplicity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional link arm and suspension arrangements are used in mid-wheel drive wheelchairs, then the wheelchair can navigate uneven surfaces, but the capability to maintain all wheels in contact with the ground when climbing and descending obstacles is limited
Solution Approach 1:
The patent employs asymmetric link arm configurations where front and rear link arms have different lengths and pivot point positions. This asymmetry allows the wheelchair to maintain all wheels in contact with the ground during obstacle navigation, as the unequal arm configurations provide different mechanical advantages for lifting front versus rear wheels over curbs and steps.
Solution Approach 2:
The link arms are designed with multiple pivot points that allow dynamic adjustment of wheel positions relative to the chassis. As the wheelchair encounters obstacles, the link arms pivot at designated points to maintain ground contact, providing adaptive movement that preserves stability while navigating uneven terrain.
2Stability of the object's composition
If complex link arm and suspension arrangements are implemented to improve obstacle navigation, then wheel contact maintenance improves, but the number of components and moving parts increases
Solution Approach 1:
The patent combines multiple functions into integrated link arm assemblies that simultaneously provide suspension, obstacle navigation, and wheel contact maintenance. By merging these functions into unified link arm structures with strategically positioned pivot points, the design achieves stable wheel contact without requiring separate complex mechanisms for each function.
Solution Approach 2:
The link arms serve multiple purposes: they act as suspension elements, obstacle negotiation mechanisms, and wheel position controllers. This multi-functionality reduces the overall component count while maintaining the ability to keep all wheels in contact with the ground during various operating conditions.
3Adaptability or versatility
If more components and moving parts are added to enhance obstacle navigation capability, then the wheelchair can handle uneven surfaces better, but the construction becomes less rugged and more complex
Solution Approach 1:
The wheelchair chassis is divided into modular sections connected by link arms with defined pivot points. This segmentation allows each section to move independently when encountering obstacles, providing adaptability while maintaining a rugged overall structure. The modular design enables obstacle navigation through controlled segment movement rather than requiring complex mechanisms throughout the entire chassis.
Data Source
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Figure 3a~3b
AI summary
A wheelchair of the mid-wheel drive type comprises a chassis frame (10), a pair of front link arms (30) and a pair of rear link arms. The link arms are pivotally connected to the chassis frame. Front caster wheels (32) and drive wheels (53) are fixed to the front link arms. Rear caster wheels (42) are fixed to the rear link arms. Each front link arm (30) is operatively connected to an adjacent rear link arm (40) by a respective coupling (70), which is arranged to transmit pivotal movement of one of the front (30) and rear (40) link arm to an opposite pivotal movement of the other of the front (30) and rear (40) link arm.