Phase-Shifted Absolute Track Sensors for Precision Length Measurement
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Solution Overview
Problem
Existing length or position measuring systems require multiple sensors to evaluate pseudo-random-coded tracks, leading to longer sensor arrays and higher production costs, with limitations in signal precision and air gap distance.
Innovation Solution
The phases of incremental and absolute tracks are shifted relative to each other, allowing for analog quantization of logical values, reducing the number of sensors needed and increasing measurable length by detecting multiple pole pairs with fewer sensors, enabling more precise signal measurement and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors are used to evaluate the PRC track, then measurement precision is improved, but device complexity and production costs increase
Solution Approach 1:
The patent changes the phase relationship parameter between incremental and absolute tracks. By shifting the phases relative to each other, the system enables analog quantization of logical values, allowing fewer sensors to detect multiple pole pairs while maintaining or improving measurement precision.
Solution Approach 2:
The patent introduces phase shifting as an additional dimension for encoding information. Instead of relying solely on the number of sensors, the system uses phase differences between tracks to create multiple detectable states, effectively adding a temporal/phase dimension to the spatial detection problem.
2Measurement precision
If multiple sensors are used to evaluate the PRC track, then measurement precision is improved, but the length of the sensor array increases
Solution Approach 1:
By changing the phase relationship parameter between tracks, the system allows each sensor to detect multiple pole pairs through analog quantization. This reduces the number of sensors needed and consequently shortens the sensor array length while maintaining measurement precision.
Solution Approach 2:
The patent merges the functions of multiple sensors into fewer sensors by utilizing phase-shifted tracks. The phase-coded absolute track allows a single sensor to effectively perform the work of multiple sensors through analog quantization of the phase-differentiated signals.
3Device complexity
If conventional digital coding is used with individual poles, then device simplicity is maintained, but air gap distance is limited
Solution Approach 1:
The patent changes from digital binary coding to analog quantization based on phase relationships. This parameter change allows the system to resolve pole positions even with larger air gaps, as the phase difference provides continuous information rather than discrete binary states.
Solution Approach 2:
The patent adds a phase dimension to the coding scheme. By utilizing phase shifts between incremental and absolute tracks, the system creates a more robust coding method that is less sensitive to air gap variations, effectively extending the usable air gap distance.
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 reduces the number of sensors required, lowers production costs, and enhances signal precision by allowing more steps per digit, resulting in a more robust and cost-effective length or position measuring system with improved signal quality.
Implementation Method 1
a sensor head is moved across a measuring gauge (incremental track) that is periodically magnetized with changing polarity
Implementation Method 2
in GMR or AMR sensors which measure the square of the magnetic flow density B2 or with each pole pair of the measuring gauge (e.g. in Hall effect sensors which provide an output voltage that is proportional to the product of the magnetic field strength and current)
Data Source
AI summary
In a length or position measuring system which has an at least locally substantially linear measuring gauge and at least one sensor able to be moved relative to the measuring gauge wherein the measuring gauge includes an incremental track and at least one absolute track and wherein the incremental track and the at least one absolute track have pole pairs arranged in the longitudinal direction of the measuring gauge, it is provided in particular that at least one pole pair of the absolute track is phase-shifted relative to a corresponding pole pair of the incremental track.