Radial Position Speed Sensor Assembly
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Solution Overview
Problem
Existing speed sensors for rotatable members often provide false indications of angular position due to radial displacement, leading to errors in speed measurement.
Innovation Solution
A sensor assembly comprising a generally annular target body, radial position sensors, a reference sensor, and an angular displacement sensor, where the angular displacement sensor is positioned to detect the angular position index passing between its inner end and the central axis, ensuring that the outputs from the reference and angular displacement sensors cancel each other's effects from radial movement, providing accurate angular position and speed measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inductive sensors are used to detect angular position, then speed measurement is enabled, but radial displacement causes false indications and measurement errors
Solution Approach 1:
A ferromagnetic target member with a non-ferromagnetic index portion is introduced as an intermediary between the sensor and the shaft. The index portion creates a distinct magnetic signature that allows the sensor to distinguish between radial displacement and actual angular position changes, eliminating false measurements while maintaining speed measurement reliability
Solution Approach 2:
The magnetic properties of the target member are changed by incorporating a non-ferromagnetic index portion in a ferromagnetic material. This parameter change creates a detectable difference in magnetic flux when the index passes the sensor, enabling accurate angular position detection independent of radial displacement
2Measurement precision
If radial displacement sensors are added to compensate for radial movement, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The single angular position sensor performs multiple functions: it detects both the angular position of the shaft and the radial displacement of the shaft. By processing the sensor output to distinguish between these two effects, the system achieves accurate angular position measurement without requiring separate radial displacement sensors, thereby avoiding increased device 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
The sensor assembly effectively eliminates false measurements caused by radial displacement, ensuring accurate determination of the rotatable member's angular position and speed by generating a pulse output only when the angular position index is detected, thus enhancing measurement precision.
Implementation Method 1
Often, such sensors are inductive sensors which detect ferromagnetic material, or the absence of such materials, on the rotatable member or a member (e.g., a sleeve) disposed about the member so as to determine angular displacement and thereby speed
Implementation Method 2
each one of the plurality of radial and axial sensors SR, SA is an inductance sensor that includes two core members each wound with a separate coil and arranged such that magnetic flux passes out of the end of one core member and into an adjacent end of the other core member
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A sensor assembly (10) includes an annular target body disposed about a rotatable member outer surface or integrally formed therewith and an annular angular position indicator (14) with at least one angular position index (22) corresponding to an angular position of the rotatable member. Radial displacement sensors (16) are spaced circumferentially about an axis (Ac) and radially outwardly from the target body outer surface (13). A reference sensor (18), which is disposed circumferentially between two of the radial displacement sensors, has an inner end spaced outwardly from the target body surface by a first spacing distance, and is configured to detect the target body. An angular displacement sensor (20) is spaced axially from the reference sensor (18) and has an inner end spaced outwardly from the position indicator surface (15) by a second spacing distance. The angular displacement sensor (20) is located such that the second spacing distance is generally equal to the first spacing distance and such that the position index (22) passes the sensor inner end during rotation of the rotatable member.