Differential Transformer Position Sensor for Cylinder Interference
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Solution Overview
Problem
Existing position determination methods using single-coil magnetic field sensors are prone to inaccuracies due to interference and lack of precision.
Innovation Solution
A differential transformer with a primary winding and two secondary windings is used, excited with AC voltage, to detect magnetically scannable structures on a metallic surface, employing differential measurement methods to generate continuous, sinusoidal signals for high-resolution position determination, and additional magnetically scannable structures are used for absolute position measurement with lower resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-coil magnetic field sensor is used for position determination, then the device complexity is low, but the measurement precision deteriorates due to interference and inaccuracies
Solution Approach 1:
The single coil sensor is divided into two separate secondary windings (S1, S2) that are spatially segmented and functionally independent. Each winding detects magnetic flux from the primary winding P1 independently, allowing differential measurement that eliminates interference signals while maintaining structural simplicity.
Solution Approach 2:
The outputs of the two secondary windings are merged through differential evaluation (subtracting the signals). This combining of multiple sensor outputs creates a differential measurement system that cancels out common-mode interference and improves position determination accuracy without requiring a completely new sensor design.
2Measurement precision
If additional magnetically scannable structures are added for absolute position measurement, then the measurement precision improves for absolute position, but the device complexity increases
Solution Approach 1:
The metallic surface of the component serves multiple functions: it provides the structural base of the component itself and simultaneously carries the magnetically scannable structures (first and second structures with different magnetic permeabilities). This multi-functionality allows absolute position measurement without adding separate reference structures or increasing overall device complexity.
Solution Approach 2:
Different regions of the metallic surface are given different magnetic properties through localized treatment. The first magnetically scannable structure and second magnetically scannable structure have distinct magnetic permeabilities, allowing the sensor to differentiate between them and determine both relative and absolute positions using the same sensor head.
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 significantly improves the accuracy of position determination by eliminating interference and achieving high resolution through continuous, sinusoidal output signals, while allowing for absolute position measurement with a lower resolution sector pointer arrangement.
Implementation Method 1
a first sensor, in particular a differential transformer, with a primary winding P1 and two secondary windings S1, S2... The primary winding P1 is excited with AC voltage
Implementation Method 2
The scannable structure of the metallic surface of the rotor is designed in the form of teeth / gaps with different permeability or magnetic properties in such a way that the magnetic coupling of the windings changes with the relative movement
Data Source
Figure 1a~2
Figure 3~4
Figure 5a~5b
AI summary
The invention relates to a method and an arrangement for determining a position of a first component (14) such as a piston rod in relation to a second component (12) such as a hydraulic, electrical or pneumatic cylinder, wherein at least one first magnetically scannable structure (34) such as a measurement strip formed on a surface (18) of said first component (14) is detected by means of at least one first magnetic flux sensor (22) connected to the second component (12) during a relative movement between the first component (14) and the magnetic flux sensor (22). To improve the accuracy of the position determination, the method is executed according to the invention as a differential measuring method, wherein a differential transformer is used as the magnetic flux sensor (22), and wherein the position of the first component (14) in relation to the second component (12) is determined absolutely, wherein a second magnetically scannable structure (28) arranged on the surface (18) of the first component (14) is detected by means of at least one second magnetic flux sensor (32) connected to the second component (12), and wherein the absolute position of the first component (14) is determined from the signal sequence of the first magnetic flux sensor (22) and the continuous output signal of the second magnetic flux sensor (32).