Rotational Angle Measurement with Eddy Current Compensation
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Solution Overview
Problem
Existing rotational angle measurement systems using magnetic sensors face accuracy issues when a non-magnetic conductor is present near the magnetic flux generator, as eddy currents generated during high-speed rotation affect the magnetic field detection, leading to incorrect angle measurements.
Innovation Solution
A rotational angle measurement apparatus that includes a magnetic sensor and a detection unit, which corrects the raw-angle signal using a correction function based on the rotational velocity of the rotatable body to account for the influence of the non-magnetic conductor, ensuring accurate angle measurement even at high speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-magnetic conductor is arranged near the magnetic flux generator, then the magnetic sensor can detect the magnetic field, but eddy currents are generated during high-speed rotation which causes measurement errors
Solution Approach 1:
The patent applies parameter changes by modifying the electrical conductivity parameter of the surrounding environment. Specifically, it replaces conductive materials with non-conductive materials (such as resin or plastic) in the housing or structural components near the magnetic flux generator. This parameter change eliminates eddy current generation while maintaining the mechanical structure, thereby resolving the measurement accuracy issue caused by eddy currents during high-speed rotation.
2Measurement precision
If non-conductive material is used to prevent eddy currents, then measurement accuracy improves, but mechanical strength and durability are reduced
Solution Approach 1:
The patent employs composite materials by combining non-conductive materials (resin, plastic) with reinforcing structures or using composite construction methods. The housing or structural components are made from composite materials that provide both mechanical strength and electrical non-conductivity. This allows the structure to maintain sufficient strength while preventing eddy current generation, thus resolving the contradiction between measurement accuracy and structural integrity.
3Adaptability or versatility
If the distance between the magnetic flux generator and magnetic sensor is increased, then design flexibility improves, but the magnetic field signal strength decreases
Solution Approach 1:
The patent applies parameter changes by modifying the magnetic flux generator parameters (such as using stronger magnets or optimizing magnetic pole configurations) to compensate for the increased distance. By changing these parameters, the magnetic field strength is maintained even at larger distances, allowing greater design flexibility while preserving measurement precision. This resolves the contradiction between adaptability and measurement accuracy.
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 system effectively measures rotational angles with high accuracy even when a non-magnetic conductor is nearby, by compensating for the eddy current-induced errors, thereby improving measurement reliability across various rotational velocities.
Implementation Method 1
The magnetic-field-angle-measurement sensor includes one which employs a Hall-effect element as a magnetic-field detection element
Implementation Method 2
The magneto-resistance element is an element of which the electrical resistance changes depending on the intensity of magnetic field or the angle of magnetic field
Implementation Method 3
when a non-magnetic conductor (electrical conductor) is arranged between a magnetic flux generator installed in a rotatable body and a magnetic sensor, when the rotatable body rotates or moves at high speed, there occurs the problem that it is difficult to measure an angle of magnetic field correctly due to an eddy current generated
Data Source
AI summary
Rotational angle measurement apparatus measuring magnetic-field angle or rotational angle with sufficient accuracy wherein a non-magnetic conductor is arranged in the vicinity of the magnetic flux generator or the magnetic sensor, even when the magnetic flux generator rotates at high speed. The rotational angle measurement apparatus is configured with a magnetic sensor 70 which responds to a magnetic-field angle and a detection unit 302 which inputs an output of the magnetic sensor. The rotational angle measurement apparatus is employed with a rotatable body 121 provided with a magnetic flux generator 202. The output of the magnetic sensor is a raw-angle signal set 155 corresponding to the magnetic-field angle. The detection unit outputs a corrected angle after a non-magnetic conductor in the vicinity of the magnetic sensor is corrected, using a correction value outputted by a correction function with rotational velocity of the rotatable body as an argument.