Position Sensor Eccentric Web Design for Tolerance Compensation
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Solution Overview
Problem
Existing position sensors for actuators in safety-critical applications, such as emergency shut-off valves, face limitations in measurement accuracy due to manufacturing, assembly, and storage tolerances, and suffer from wear issues in cabling, leading to unreliable detection of actual angular positions.
Innovation Solution
A position sensor design featuring a pivoting measuring shaft with a pivot axis that allows less than 360° rotation, equipped with an angle sensor, such as an AMR or GMR sensor, and a second measuring shaft section with a fixed angle sensor component, along with eccentric webs, to improve measurement accuracy and reduce assembly-related tolerances, and includes a position detector for precise angular position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Hall sensor is attached to a rotating measuring shaft to detect angular position, then the actuator position can be monitored, but the sensor wiring experiences wear due to continuous rotation
Solution Approach 1:
The system is divided into a rotating part (measuring shaft with magnet) and a stationary part (Hall sensor mounted on housing). This segmentation allows the sensor to remain stationary while only the magnet rotates, eliminating wiring wear on the sensor side.
Solution Approach 2:
A magnet is introduced as an intermediary between the rotating shaft and the stationary Hall sensor. The magnet's rotational position encodes the shaft position, allowing the stationary sensor to detect angular position without physical connection to rotating components.
2Measurement precision
If manufacturing, assembly, and storage tolerances are present in the measuring shaft and sensor mounting, then the position sensor can be manufactured, but measurement accuracy is limited
Solution Approach 1:
The mechanical direct-contact measurement system is replaced with a magnetic field-based measurement system. The Hall sensor detects the magnetic field position of the magnet, which is less sensitive to mechanical assembly tolerances and shaft runout, thereby improving measurement accuracy.
Solution Approach 2:
The measurement approach changes from direct mechanical position sensing to magnetic field position sensing. By measuring the magnetic field parameters (flux density, field direction) instead of direct mechanical contact, the system achieves higher precision that is less affected by manufacturing tolerances.
3Reliability
If a lever mechanism is used to convert linear valve rod displacement to rotational movement of the measuring shaft, then the actuator position can be measured, but sudden actuator movements negatively affect the magnetization of permanent magnets
Solution Approach 1:
The mechanical lever mechanism that directly couples to the magnet is replaced with a magnetic field-based detection system. The magnet remains mounted on the shaft but is no longer subjected to mechanical stresses from levers during sudden movements, protecting it from demagnetization while still enabling position detection.
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 significantly improved measurement accuracy and reduced wear on sensor cabling, enabling precise and reliable detection of actual angular positions, particularly in safety-critical applications, with enhanced tolerance compensation and simplified assembly.
Implementation Method 1
the angle sensor, in particular an AMR sensor or a GMR sensor
Implementation Method 2
the angle sensor, in particular an AMR sensor or a GMR sensor
Implementation Method 3
the Hall sensor allows the actual angular position of the measuring shaft relative to the housing to be detected
Data Source
Figure 1a~1b
Figure 1c
Figure 2a~2b
AI summary
Position sensor (1) for an actuator of a process plant, comprising a measuring shaft (3) pivotable by less than 360° about a pivot axis (W) and an angle sensor (5) for determining the actual angular position of the measuring shaft (3) relative to a stationary reference point, comprising at least one web (11, 13) extending eccentrically to the pivot axis (W) in the axial direction (A), which is arranged in the axial direction (A) between a first measuring shaft section (15) and a second measuring shaft section (17) and connects the measuring shaft sections (15, 17) in a rotationally fixed manner, and a free space (21) arranged in the axial direction (A) between the measuring shaft sections (15, 17) and in the radial direction (Q) at the level of the pivot axis (W), in which the angle sensor (5) is at least partially arranged, wherein the at least one eccentric web (11, 13) provides access to the free space (21) in a radial direction (Q) perpendicular to the axial direction (A) is permitted; as well as.