Rotating Cylinder Speed and Position Sensing
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Solution Overview
Problem
Existing systems for monitoring axial displacement and rotational speed of rotating cylinders, such as propeller rotor stages, are limited by restricted bandwidth due to the large proportion of the cylinder circumference used by each pair of grooves, resulting in few possible groove pairs and reduced measurement efficiency.
Innovation Solution
A sensing arrangement comprising a stationary magnetised core and two coils connected in series, wound around the core, which induces current as the cylinder rotates, allowing calculation of rotational speed from frequency and longitudinal position from current amplitude, eliminating the need for separate excitation and enabling simultaneous measurement of both parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pair of grooves (one angled and one longitudinal) is used to measure axial displacement and rotational speed, then both parameters can be measured, but the bandwidth of measurement is restricted because each pair uses a relatively large proportion of the cylinder circumference
Solution Approach 1:
The single groove pair is segmented into two independent single-phase coils positioned at different axial locations. Each coil independently detects the passing features on the cylinder, generating separate signals that are processed to derive both rotational speed and axial displacement. This segmentation allows multiple measurement cycles per rotation, significantly increasing measurement bandwidth while reducing the angular span required for each measurement pair.
2Measurement precision
If separate excitation is used for the sensing arrangement, then the sensing can be performed, but the complexity, weight, and cost increase
Solution Approach 1:
The rotating cylinder with magnetic features serves its own excitation function by inducing voltage in the stationary coils during rotation. The relative motion between the magnetized cylinder and the coils generates the necessary electromagnetic induction without requiring any external excitation source. This self-excitation approach eliminates separate excitation systems, reducing overall device complexity, weight, and cost while maintaining full sensing capability for both rotational speed and axial displacement.
Solution Approach 2:
The mechanical or electrical excitation system is replaced with an electromagnetic induction-based self-excitation mechanism. The kinetic energy of the rotating cylinder directly converts to electrical signals in the coils through electromagnetic induction, eliminating the need for separate excitation equipment and simplifying the overall system architecture.
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 solution enhances measurement efficiency by deriving both rotational speed and longitudinal position from a single sensing arrangement without separate excitation, improving resolution and reducing complexity, weight, and cost.
Implementation Method 1
current is induced in the coils by the cyclic variation of magnetic flux in the core
Data Source
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AI summary
Apparatus, for example for a pitch change mechanism, comprising a cylinder having a magnetically encoding portion defining an annular array of features extending parallel to the longitudinal axis of the cylinder, the cylinder rotating in use and able to translate longitudinally. There is a sensing arrangement comprising a stationary magnetised core and two coils connected in series and wound around the core. In use the cylinder rotates and current is induced in the coils. Monitoring equipment is arranged to calculate rotational speed of the cylinder from the frequency of the current and to calculate longitudinal position from the relative amplitude of the current in each coil.