Inductive Position Sensor Offset Calibration Without Digital Cores
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Solution Overview
Problem
Inductive position sensors face challenges in accurately compensating for sensor offset variations due to factors like airgap changes, temperature fluctuations, and aging, especially in analog-only ICs without digital cores, which affect the precision of position detection.
Innovation Solution
An analog dynamic compensation mechanism using offset compensation circuitry with current DACs and current mirrors to dynamically adjust offset correction based on excitation signal amplitude, ensuring accurate position sensing without relying on digital processors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital cores are used for offset compensation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces digital signal processing with an analog compensation mechanism. Current mirrors and DACs operate in the analog domain to dynamically adjust offset correction, eliminating the need for digital cores while maintaining position detection precision through continuous analog signal adjustment.
Solution Approach 2:
The offset compensation circuitry autonomously adjusts for offset variations using feedback from the excitation signal amplitude. The current mirrors automatically track and compensate for offset drift caused by airgap changes, temperature fluctuations, and aging without requiring external digital processing or calibration interventions.
2Reliability
If dynamic compensation is implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent dynamically adjusts compensation parameters by varying current amplitudes through DACs based on excitation signal amplitude. This continuous parameter adjustment enables the circuit to adapt to changing conditions (airgap, temperature, aging) and maintain reliable offset compensation without complex digital control logic.
Solution Approach 2:
The offset compensation mechanism uses feedback from the excitation signal amplitude to continuously adjust the compensation current. The current mirrors track the excitation signal variations and automatically adjust the offset correction, creating a self-regulating system that improves reliability through real-time adaptation.
3Device complexity
If analog-only ICs are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent achieves high measurement precision in analog-only ICs by substituting digital signal processing with carefully designed analog compensation circuitry. The current mirrors and DACs operate continuously in the analog domain to track and correct offset variations, maintaining position sensing accuracy without requiring digital cores or complex processing.
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 solution provides precise and cost-effective compensation for sensor offsets in both open and closed-loop applications, maintaining accurate position detection across varying conditions without the need for digital cores, suitable for both linear and rotary sensors.
Implementation Method 1
an excitation circuit to generate an excitation signal to drive one or more excitation coils, the excitation signal to produce a varying magnetic field around the one or more excitation coils for inducing a sinusoidal sense signal in a sense coil
Implementation Method 2
the varying magnetic field disturbed in accordance with a position of a target which modulates the sinusoidal sense signal
Data Source
AI summary
An apparatus comprises a position sensor circuit including an offset compensation circuitry to compensate for an offset voltage of a position signal. The offset compensation circuitry includes at least a first current digital-to-analog converter (DAC) and a second current DAC. The first current DAC includes a first reference input to receive a first input current that varies in response to changes in amplitude of an excitation signal. The first current DAC further includes first logic inputs to adjustably set to respective logic levels to produce a first output current to substantially match a predetermined constant current. The second current DAC includes a second reference input to receive the first output current from the first current DAC. The second current DAC further includes second logic inputs to adjustably set to respective logic levels to produce a second output current to compensate for the offset voltage.