Pipe Inspection Cable Counter Using Composite Magnetic Field
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Solution Overview
Problem
Accurate measurement of cable deployment in pipe inspection systems is challenging due to difficulties in placing a rotating magnet and sensor along the axis of rotation, especially when the axle is solid, leading to errors in distance calculation.
Innovation Solution
A pair of cylindrical permanent magnets creates a distributed composite magnetic field, detected by a two or three-axis magnetic sensor, allowing precise measurement of angular motion and cable deployment, with the sensor positioned offset from the axis to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotating magnet and sensor are placed along the axis of rotation for measuring cable deployment, then measurement capability is provided, but placement difficulties arise when the axle is solid, leading to positioning errors
Solution Approach 1:
The magnetic field measurement function is segmented across multiple magnets arranged in a circle rather than using a single magnet-sensor pair along the axis. This circular arrangement of multiple magnets allows the sensor to be positioned off-axis while still achieving accurate angular motion detection through composite magnetic field analysis.
Solution Approach 2:
The measurement approach transitions from a one-dimensional axial arrangement to a two-dimensional circular arrangement. By positioning magnets and sensor in a circular configuration rather than along the rotation axis, the system enables accurate measurement while accommodating solid axle structures that prevent axial placement.
2Ease of manufacture
If the sensor is positioned offset from the axis of rotation to facilitate manufacturing, then placement ease is improved, but offset errors in distance calculation increase
Solution Approach 1:
Multiple individual magnetic fields from separately positioned magnets are merged into a composite magnetic field. The sensor detects this composite field, and through signal processing that combines information from all magnets, the system achieves accurate angular position measurement despite the sensor's offset position from the rotation axis.
Solution Approach 2:
The system uses feedback from the composite magnetic field detection to calculate and correct for offset errors. By analyzing the pattern of magnetic field changes as magnets rotate past the offset sensor, the system can accurately determine angular position and cable deployment distance while compensating for the non-ideal sensor placement.
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 enables precise calculation of cable extension and distance traveled, reducing offset errors and improving accuracy in pipe inspection systems, allowing for accurate location of blockages and pipe conditions.
Implementation Method 1
A magnetic sensor may be mounted on one of the frame and the rotatable member. The magnetic sensor may generate signals representing changes in a magnetic field in at least two axes. Two or more permanent magnets may be mounted in spaced apart relationship on the other one of the frame and rotatable member so that the magnetic sensor can detect changes in a composite magnetic field generated by the permanent magnets during relative rotational movement between the magnetic sensor and the magnets.
Data Source
AI summary
Apparatus for magnetically sensing, computing, and displaying cable distance, as well as computing and displaying other user-selectable information in a pipe inspection system or other system is disclosed. Two or more permanent magnets may be mounted in spaced apart fashion, on either a frame or a rotatable member supported on the frame for rotation about an axis. A magnetic sensor may be mounted on the other one of the rotatable member or frame on which the magnets are not mounted, so that either the magnets rotate around the magnetic sensor or the magnetic sensor rotates between the permanent magnets. The magnetic sensor may generate output signals representing changes in at least two axes in a composite magnetic field generated by the permanent magnets.