Inductive Sensor Segmentation for Signal Uniformity
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Solution Overview
Problem
Inductive absolute measuring systems face challenges in providing reliable and accurate position information under harsh environmental conditions and achieving high resolution over large measuring ranges, particularly due to sensitivity to external factors and limitations in signal strength and uniformity.
Innovation Solution
The design incorporates a sensor element with balanced receiver and emitter windings, using a coded pitch and compensating windings to generate almost offset-free signals, and employs a dual sensor structure with one sensor offset by half a period to stabilize signal processing, ensuring consistent signal amplitudes and reduced dependency on air gap variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a single emitter winding surrounds all receiver windings to generate position information, then the measuring range can be extended, but the induction gradient becomes too high causing signal amplitude to vary greatly and reducing measurement precision
Solution Approach 1:
The single emitter winding is divided into multiple separate emitter windings, each associated with specific receiver windings. This segmentation reduces the induction gradient in each local area, resulting in more uniform signal amplitudes across different receiver windings while maintaining the ability to measure over the entire extended range through coordinated operation of all segments.
Solution Approach 2:
Compensating windings are introduced as intermediary elements between the emitter and receiver windings. These compensating windings generate counteracting magnetic fields that balance out the excessive induction gradient, thereby equalizing the signal amplitudes received by different receiver windings and improving measurement precision across the full measuring range.
2Measurement precision
If the emitter winding area is increased to reduce induction gradient, then signal uniformity improves, but the overall excitation field strength decreases making signal evaluation more difficult
Solution Approach 1:
Instead of using one large emitter winding that would dilute the field strength, the system employs multiple smaller emitter windings distributed across the measuring range. Each emitter winding maintains high local field strength while the segmented arrangement ensures uniform signal distribution across all receiver windings, thus resolving both contradictions simultaneously.
Solution Approach 2:
Each emitter winding is optimized to provide strong local excitation for its associated receiver windings, while the overall distribution of multiple emitters ensures uniformity across the entire measuring range. This local optimization approach maintains high field strength where needed without sacrificing overall signal uniformity.
3Length of stationary object
If additional incremental divisions of further different periods are added to the scale, then the absolute measuring range can be increased, but the device complexity increases
Solution Approach 1:
The scale is divided into multiple sections, each with a specific graduation period, where each section is read by corresponding receiver windings. This segmentation allows the system to achieve a large absolute measuring range through coordinated reading of multiple sections without requiring an overly complex single-scale design, as each section can be independently optimized.
Solution Approach 2:
Instead of increasing the complexity of a single linear scale, the system transitions to a multi-dimensional approach by using multiple receiver windings at different positions and orientations, each reading specific sections of the scale. This dimensional expansion allows large measuring ranges to be achieved through spatial arrangement rather than scale complexity.
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 results in high accuracy and reliability for position detection, achieving resolutions of up to 60 nanometers over a maximum measuring range of 65536 mm, with improved signal stability and reduced sensitivity to environmental influences.
Implementation Method 1
inductively working absolute length and angle measuring system in which a coil structure and associated evaluation electronics in a scanning head along the measuring section moves relative to an absolutely coded scale and detects the position
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a measuring device for detecting absolution positions, comprising a sensor unit (N, M) as a planar coil structure and a scale having alternating areas of variable reluctance or conductivity along the measuring line. The invention is characterized in that the measuring device has at least two divisions (T1, T2) for determining the absolute position within the measuring length, the at least two divisions being coded aperiodically and in a bitwise manner and extending parallel to each other and, for each bit formation, having opposite effects on a coil element (S2, S3, S4) as part of the entire sensor structure. Preferably, each coil element (S2, S3, S4), comprising its own emitter and receiver windings (E, R), is balanced in offset, and the entire sensor structure provides approximately equal signal amplitudes for each individual bit of the absolute value at any position of the coded scale by means of compensation windings.