Linear Positioning Sensor Using Orthogonal Magnetic Sensors
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Solution Overview
Problem
Existing elevator control systems face challenges in achieving precise vertical positioning of elevator cars with respect to building floors due to cost and sensitivity to temperature and humidity variations, using lasers and mirrors which are costly and unreliable.
Innovation Solution
A linear positioning system utilizing a pair of magnets with common poles facing each other and a magnetic sensor housed orthogonally to detect motion along the X, Y, and Z axes, providing a low-cost solution with self-canceling magnetic variations for precise sub-1 mm accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lasers and mirrors are used for vertical positioning, then positioning precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the optical mechanical system (lasers and mirrors) with a magnetic field-based sensing system. Magnets mounted on the elevator car interact with a magnetic sensor in the shaft to generate position signals, eliminating the need for complex optical alignment and reducing system complexity while maintaining positioning precision.
Solution Approach 2:
The patent uses magnetic field patterns as a substitute for optical laser lines. The magnetic field serves as an invisible 'copy' of the optical measurement path, allowing position detection without the physical constraints and complexity of optical components. The magnetic sensor detects field variations that correspond to the elevator car's position, providing a simplified measurement approach.
2Measurement precision
If lasers and mirrors are used for vertical positioning, then positioning precision is improved, but reliability deteriorates due to temperature and humidity sensitivity
Solution Approach 1:
The patent substitutes the optical measurement system with a magnetic field-based system. Magnetic fields are inherently less sensitive to environmental factors like temperature and humidity compared to optical systems. The magnetic sensor detects changes in magnetic flux caused by the movement of magnets, providing stable positioning data even in varying environmental conditions.
Solution Approach 2:
The patent changes the physical parameter used for measurement from optical (light) to magnetic (magnetic field). This parameter change fundamentally alters the system's response to environmental conditions. Magnetic field measurements are less affected by temperature and humidity variations, improving reliability while maintaining the ability to achieve precise positioning through careful sensor and magnet configuration.
3Device complexity
If magnetic sensors are used for positioning, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent employs asymmetric magnet configurations and non-uniform magnetic field distributions to create distinct signal patterns for different positions. By carefully designing the magnet arrangement and gap dimensions, the system generates uniquely identifiable magnetic field signatures that enable precise position determination. The asymmetric configuration ensures that the magnetic sensor produces distinguishable outputs for different elevator car positions.
Solution Approach 2:
The patent transitions from one-dimensional optical measurement to three-dimensional magnetic field sensing. The magnetic sensor detects field variations in multiple dimensions (strength, direction, and spatial distribution), providing richer position information. This dimensional expansion allows the simplified magnetic system to achieve precision comparable to complex optical systems by utilizing the additional information available in the magnetic field vector components.
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 system achieves precise sub-1 mm vertical and horizontal positioning accuracy, resistant to temperature and humidity variations, using a low-cost dual magnet arrangement with magnetic sensors, applicable beyond elevators for any two objects requiring linear alignment.
Implementation Method 1
A magnetic flux sensor is positioned within the magnetic field to sense varying magnitudes of magnetic flux density along the axis through a sensing plane oriented substantially perpendicular to the axis. The magnetic flux sensor generates an output signal uniquely representative of a sensed magnitude of the magnetic flux density.
Implementation Method 2
The pole pieces are formed of a composite material comprising a non-magnetic material and a magnetizable material. The pole pieces cooperate with the magnets to generate a magnetic field that is substantially symmetrical relative to the axis and which has a magnetic flux density that linearly varies along the axis.
Data Source
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AI summary
A linear positioning system including a pair of magnets disposed adjacent one another and defining a gap therebetween, the magnets having common poles facing one another, and first, second, and third magnetic sensors disposed within a housing and oriented orthogonally with respect to one another for detecting linear motion along X, Z, and Y axes of a Cartesian coordinate system, respectively, the housing being movable along an axis passing through the gap.