Wheelchair Sensor Arrangement for Zero Position Stability

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Solution Overview

Problem

Existing sensor arrangements for wheelchair wheels face challenges in reliably and reproducibly reaching a zero position due to fatigue of bending plates and irregularities/tolerances between the hand rim and running wheel, leading to overshooting and difficulty in precise positioning.

Innovation Solution

A sensor arrangement with two restoring elements that rest against stops with a prestressing force, allowing for reliable detection of hand rim movement in both directions, and are mounted on the running wheel fastening arrangement or hand rim fastening arrangement, ensuring a stable and precise zero position is maintained throughout the sensor's service life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bending plates are used to restore the hand rim fastening arrangement to zero position, then the hand rim can be actuated and restored, but overshooting occurs and exact zero position cannot be reached due to fatigue of bending plates

Engineering Contradiction:

Improvereliability of zero positionVSAvoidtime to reach zero position

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the mechanical bending plate system with a magnetic field-based sensor system. The sensor arrangement detects hand rim actuation through magnetic field changes rather than mechanical movement, eliminating the need for restoring elements and enabling precise zero position detection without overshooting or fatigue issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a magnetic field as an intermediary between the hand rim actuation and the detection system. Magnets are attached to the hand rim fastening arrangement, and Hall effect sensors detect their position, providing accurate zero position feedback without direct mechanical contact or restoring forces.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the sensor arrangement is situated between the rim of the running wheel and the hand rim, then it can detect hand rim actuation, but irregularities and tolerances of the hand rim and running wheel rim complicate fastening in position

Engineering Contradiction:

Improvedetection precision of hand rim actuationVSAvoidease of fastening the sensor arrangement

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent uses magnetic fields as an intermediary detection mechanism that is not affected by mechanical tolerances or irregularities of the hand rim and running wheel rim. The magnets and Hall effect sensors create a detection system that operates independently of the mechanical interface, eliminating positioning complications.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical sensor arrangement between the running wheel rim and hand rim with a magnetic field-based detection system. This substitution eliminates the need for precise mechanical fastening while maintaining accurate detection of hand rim actuation, as the magnetic field detection is insensitive to mechanical tolerances.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If spring elements are used to return the armature to zero position, then the armature can be actuated and restored, but it is difficult to define and reliably reach the zero position depending on design and fatigue of spring elements

Engineering Contradiction:

Improvereliability of zero positionVSAvoidcomplexity of spring element system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical spring element system with a magnetic field-based detection system. The Hall effect sensors detect the position of magnets attached to the hand rim fastening arrangement, providing reliable zero position feedback without mechanical restoring forces or complex spring mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 sensor arrangement allows for reliable and reproducible detection of hand rim actuation in both forward and backward directions, maintaining a precise zero position despite increasing fatigue, and is cost-effective to produce, with a design that simplifies assembly and tolerance compensation.

Implementation Method 1

Two restoring elements are situated on the running wheel fastening arrangement and rest against the hand rim fastening arrangement with a prestressing force at least in the zero position

Methodology Applied

Scientific EffectPrestressing force: Elasticity

Implementation Method 2

at least one sensor that detects a movement of the hand rim fastening arrangement relative to the running wheel fastening arrangement

Methodology Applied

Scientific EffectMagnetic field detection: Hall Effect

Data Source

PatentUS8657320B2Sensor arrangement

Publication Date: 2014.02.25 ALBER ANTRIEBSTECHN GMBH

AI summary

A sensor arrangement for a wheelchair wheel that has a running wheel with a hub and a hand rim includes a running wheel fastening arrangement that is fastened to the running wheel, a hand rim fastening arrangement that is fastened to the hand rim and at least one sensor that detects a movement of the hand rim fastening arrangement relative to the running wheel fastening arrangement. Two restoring elements are provided on the running wheel fastening arrangement and rest against the hand rim arrangement with a prestressing force at least in the zero position. Both restoring elements rest against at least one stop of the running wheel fastening arrangement in the zero position of the sensor arrangement.