Magnetic Position Sensor for Extreme Environments
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Solution Overview
Problem
Conventional position sensing technologies face challenges in operating effectively in extreme environments, such as vacuum and high temperatures, due to sensitivity to contamination, temperature effects, and limited resolution, making them unsuitable for applications like lunar surface exploration and harsh industrial processes.
Innovation Solution
A system utilizing an incremental track with a plurality of sectors and a measurement subsystem comprising differential read-heads with primary and secondary coils, generating sinusoidal and cosine signals to determine position independently of amplitude changes, and an absolute track with non-uniform sections for absolute position detection, isolated from the external environment by a barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical encoders are used for precision motion control, then measurement precision is improved, but sensitivity to contamination increases
Solution Approach 1:
The patent replaces optical encoding with magnetic encoding, substituting an optical system with a magnetic field-based system. The magnetic encoder uses a magnetic wheel and magnetoresistive or Hall-effect sensors that are inherently insensitive to dust and dirt contamination, while maintaining precision motion control capabilities through detection of magnetic field variations as the magnetic wheel rotates.
Solution Approach 2:
The patent changes the physical parameter used for position encoding from optical properties (light transmission through transparent/opaque areas) to magnetic properties (magnetic field variations). This parameter change enables the system to operate in harsh environments with dust and dirt, as magnetic fields are not affected by particulate contamination in the same way optical paths are.
2Object-affected harmful factors
If conventional magnetic encoders are used in harsh environments, then sensitivity to contamination is reduced, but measurement resolution is limited
Solution Approach 1:
The patent segments the magnetic wheel into multiple magnetic poles arranged in specific patterns around the circumference. By increasing the number of magnetic poles and using differential sensor arrangements, the system achieves higher measurement resolution while maintaining ruggedness. The segmentation of the magnetic field into distinct poles allows for more precise position determination through differential measurement techniques.
Solution Approach 2:
The patent transitions from single-sensor magnetic detection to a differential sensor arrangement that measures magnetic field variations in multiple dimensions. The differential read-heads with multiple secondary coils detect changes in magnetic field strength and direction, creating a multi-dimensional measurement space that enables higher resolution position sensing while maintaining insensitivity to contamination.
3Adaptability or versatility
If conventional encoders operate in extreme environments, then adaptability to harsh conditions is improved, but reliability decreases due to out-gassing and temperature effects
Solution Approach 1:
The patent replaces optical components (glass or plastic disks, light sources, photo detectors) with magnetic components that have no out-gassing issues in vacuum environments. The magnetic encoder components, including the magnetic wheel and magnetoresistive or Hall-effect sensors, are inherently suitable for vacuum operation and can tolerate a broad temperature range, eliminating the reliability problems associated with optical systems in extreme environments.
Solution Approach 2:
The patent employs composite material strategies in the magnetic encoder construction, using materials that are specifically selected for their performance in extreme environments. The magnetic wheel may use specialized magnetic materials, and the sensor components use materials with appropriate thermal and vacuum characteristics, creating a composite system that maintains reliability across broad temperature ranges and vacuum conditions.
4Strength
If inductive encoders are used for position sensing, then ruggedness is improved, but temperature dependence increases
Solution Approach 1:
The patent changes the sensing mechanism from inductive (relying on eddy currents in iron cores) to magnetic field detection using magnetoresistive or Hall-effect sensors. This parameter change eliminates the temperature dependence associated with soft iron properties in inductive encoders, while maintaining the ruggedness advantage. The magnetic sensors used in the patent have significantly reduced temperature coefficients compared to inductive systems.
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 provides accurate and robust position sensing with high resolution, insensitivity to environmental changes, and resistance to contamination, enabling reliable operation in extreme conditions.
Implementation Method 1
each having at least one primary coil and at least two differential secondary coils, the at least two differential secondary coils of one of the at least two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track
Implementation Method 2
the at least two differential secondary coils of one of the at least two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track
Data Source
AI summary
A system for position sensing includes an incremental track including a plurality of sectors and a measurement subsystem. The measurement subsystem includes at least two differential read-heads each having at least one primary coil and at least two differential secondary coils, the at least two differential secondary coils of one of the at least two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track and the at least two differential secondary coils of the other of said two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track.