Inductive Sensor Absolute Positioning via Spatial Phase
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Solution Overview
Problem
Existing inductive sensor devices for absolute position measurement are complex, costly, and require significant space, while also being sensitive to noise and having limited accuracy and range.
Innovation Solution
An inductive sensor device with a scale unit having scale elements arranged in a single line with varying pitch, detected by two receive coil sets that create distinct spatial phases for accurate absolute position determination, allowing for reduced space usage and improved noise resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple lines of scale elements with different pitches are used for absolute position determination, then measurement accuracy is improved, but device complexity and space requirements increase
Solution Approach 1:
The sensor device divides the measurement function into two separate receive coil sets, each detecting spatial phase information from scale elements. The first receive coil set detects a first spatial phase while the second receive coil set detects a second spatial phase, allowing absolute position determination through phase comparison without requiring multiple physical scale element lines
Solution Approach 2:
The invention transitions from using multiple scale element lines (spatial dimension) to using multiple receive coil sets with different spatial phase detections (phase dimension). By measuring spatial phase differences between coil sets rather than using multiple physical lines, the device achieves absolute position measurement with reduced structural complexity
2Measurement precision
If scale elements with varying dimensions are used to create aperiodic patterns for absolute position measurement, then measurement range is extended, but sensitivity to noise and displacement errors increases
Solution Approach 1:
The invention uses scale elements with constant dimensions and uniform pitch, changing the measurement approach from varying physical dimensions to varying detection parameters. The receive coil sets detect different spatial phases from the same uniform scale element pattern, extending measurement range through phase unwrapping while maintaining noise immunity of constant-dimension scale elements
3Measurement precision
If receive coils with varying wavelengths are used for absolute position detection, then position measurement capability is improved, but device complexity and cost increase
Solution Approach 1:
The invention uses receive coils with identical or substantially the same wavelength in both the first and second receive coil sets. The spatial phase difference between coil sets provides the absolute position information without requiring wavelength variation, simplifying the coil configuration while maintaining measurement capability
Solution Approach 2:
The invention introduces spatial phase as an intermediary measurement parameter between the scale elements and the final position reading. The receive coil sets detect spatial phases that are then processed to determine absolute position, avoiding the need for complex varying-wavelength coil designs
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 device achieves high accuracy and extended measurement range with reduced sensitivity to noise, using a single line of scale elements and two receive coil sets with non-linearly varying spacing, enabling precise position detection with minimal space and power consumption.
Implementation Method 1
The transmit coil creates a magnetic field, that is varied by means of the scale elements. Depending on the relative position between the sensor unit and the scale unit, a field pattern is thus created that is detectable by means of the respective receive coil.
Implementation Method 2
a field pattern is thus created that is detectable by means of the respective receive coil. A receive signal provided by each receive coil can be used to determine a relative position between the sensor unit and the scale.
Data Source
AI summary
An inductive sensor device (23) having a scale unit (24) and a sensor unit (25) that can be moved relative to each other in a measuring direction (M) is described. The scale unit contains scale elements (26) that are adapted to create a field pattern (P(x)) in measuring direction (M) that is detected by means of a receive circuit (35) of the sensor unit (25). The receive circuit (35) contains at least a first receive coil set (36) and a second receive coil set (37) that are offset in measuring direction (M). In so doing a first spatial phase and a second spatial phase receive signal is provided by these receive coil sets (36, 37) respectively. These spatial phases can be used for absolute position determination.