Magnetic Closed-Loop Sensors with Diagnostics
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Solution Overview
Problem
Magnetic field sensors face challenges with stray field effects and limited linearity, which can lead to non-linear responses and sensitivity drifts, affecting their accuracy and reliability in applications such as robotics and automotive systems.
Innovation Solution
The implementation of a magnetic closed-loop system using magnetoresistance elements (TMR and GMR) with diagnostic circuitry operating in a separate frequency band, which generates a feedback signal to mask stray field effects and maintain the sensing elements within a linear operational range, thereby enhancing sensitivity and gain independently of the sensing elements' sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic-field sensing elements are used to detect magnetic fields, then motion or position detection capability is provided, but stray field effects and limited linearity cause non-linear responses and sensitivity drifts
Solution Approach 1:
The patent implements a magnetic closed-loop system where a feedback coil generates a feedback magnetic field that opposes the applied magnetic field. The magnetoresistance circuitry detects the residual field (difference between applied and feedback fields) and produces an output signal that is fed back through the feedback coil. This negative feedback mechanism linearizes the sensor response and masks stray field effects, resolving the contradiction between measurement linearity and sensitivity drift.
Solution Approach 2:
The patent changes the operational parameters of the magnetoresistance circuitry by operating it in a closed-loop configuration where the feedback magnetic field dynamically adjusts the residual field magnitude. This parameter change ensures the sensing elements operate within their linear range regardless of applied field strength, eliminating sensitivity drift and improving measurement linearity.
2Measurement precision
If a closed-loop system is implemented to mask stray field effects, then measurement linearity is improved, but device complexity increases
Solution Approach 1:
The feedback coil serves multiple functions: it generates the feedback magnetic field for linearization, acts as a magnetic actuator, and works in conjunction with the magnetoresistance circuitry to create the closed-loop system. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while achieving improved measurement linearity.
3Reliability
If diagnostic circuitry operates in a separate frequency band, then loop component functionality can be verified, but signal processing complexity increases
Solution Approach 1:
The patent segments the signal processing into two distinct frequency bands: the main signal path processes the magnetic field sensing output, while the diagnostic signal path operates at a separate frequency band. This frequency-domain segmentation allows independent processing and verification of loop component functionality without interfering with the primary sensing function, managing complexity through spectral separation.
Solution Approach 2:
The diagnostic signal acts as an intermediary that traverses the closed-loop system at a separate frequency, allowing verification of component functionality without directly interfering with the main sensing signal. This intermediary approach enables diagnostic capability while maintaining signal processing manageability through frequency separation.
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
This approach effectively linearizes the response of magnetic field sensors, reduces the impact of stray fields, and maintains the sensors in a linear operational range, improving their accuracy and reliability by masking non-linear effects and sensitivity drifts.
Implementation Method 1
Magnetoresistance elements are another class of magnetic sensing elements that have a variable resistance that changes in response to changes in an applied or sensed magnetic field
Implementation Method 2
Hall effect elements are one class of magnetic field sensing elements that have a variable voltage in response to changes in an applied or sensed magnetic field
Implementation Method 3
The magnetic field sensing elements (e.g., TMR elements and/or GMR elements) can be used in a first stage of a high gain amplifier which provides a feedback signal to a feedback coil in a closed loop to provide a magnetic feedback field
Data Source
AI summary
Magnetic-field sensors use magnetic closed-loops with magnetic-field sensing elements, e.g., magnetoresistance (MR) elements, and diagnostic circuitry operating in a separate frequency band than that used for magnetic field sensing. The MR elements can be used in a first stage of a high gain amplifier which provides a feedback signal to a feedback coil in a feedback configuration to provide a magnetic feedback field. The magnetic feedback field attenuates the sensed magnetic field so that the MR elements operate in a linear range. Magnetic stray field effects and any limited linearity of magnetic-field sensing elements can be masked by the loop gain of the closed loop. For a magnetic closed-loop, a negative feedback configuration can be used or a positive feedback configuration can be used with a loop-gain of less than one. The diagnostic signal traverses the closed-loop and provides information regarding correct or incorrect functioning of the loop components.