Actuator Assembly with Magnetic Shield for Rotary Sensor
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Solution Overview
Problem
Existing rotary position sensors face challenges in accurately measuring angular displacement due to interference from external magnetic fields and leakage magnetic flux, which can lead to measurement errors in control and monitoring applications.
Innovation Solution
An actuator assembly is designed with a rotatable shaft, a magnet, non-magnetic material between the magnet and shaft, and a magnetic shield made of soft magnetic material surrounding the rotary sensor and magnet to shield from external magnetic fields, while the magnet's U-shaped magnetization and non-magnetic material reduce leakage flux and provide a uniform magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotary position sensor is used to measure angular displacement, then position measurement capability is provided, but measurement precision deteriorates due to interference from external magnetic fields and leakage magnetic flux
Solution Approach 1:
A magnetic shield made of soft magnetic material is introduced as an intermediary component between the external magnetic field environment and the rotary position sensor. This shield captures and redirects external magnetic field lines, preventing them from reaching the sensor and causing measurement errors. The shield acts as a mediator that protects the sensitive sensing components while allowing the desired magnetic field from the permanent magnet to reach the sensor.
Solution Approach 2:
Non-magnetic material is positioned between the permanent magnet and the shaft to extract and eliminate the harmful leakage magnetic flux that would otherwise travel along the shaft. By removing this magnetic flux path, the system prevents measurement errors caused by stray magnetic fields while maintaining the useful magnetic field for position sensing.
2Ease of operation
If a magnet is mounted on the shaft for sensing, then position sensing is enabled, but harmful factors increase due to leakage magnetic flux from the magnet to the shaft
Solution Approach 1:
Non-magnetic material serves as an intermediary barrier positioned between the permanent magnet and the shaft. This material blocks the leakage magnetic flux from traveling along the shaft while allowing the primary magnetic field to reach the rotary position sensor. The intermediary prevents the harmful interaction between the magnet and shaft without compromising the sensing functionality.
Solution Approach 2:
The magnetic shield provides localized magnetic field management by creating different magnetic environments in different regions. The shield allows the useful magnetic field from the permanent magnet to reach the sensor while capturing and redirecting external magnetic field lines away from the sensing area. This local differentiation of magnetic properties enables simultaneous achievement of sensing functionality and interference rejection.
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 enhances the accuracy of angular displacement measurements by shielding from external magnetic fields and reducing leakage flux, thereby improving the robustness and precision of rotary position sensing, especially in high-voltage and current applications.
Implementation Method 1
a magnetic shield surrounding at least a part of the rotary sensor and at least a part of the magnet mounted to the shaft to shield the sensor and the magnet from an external magnetic field
Implementation Method 2
non-magnetic material positioned between the magnet and the shaft... The non-magnetic material may reduce leakage magnetic flux from the magnet to the shaft
Implementation Method 3
Hall effect sensor senses and measures changes in the magnitude and/or direction of the magnetic field generated by a magnet
Implementation Method 4
a magnet mounted to the rotatable shaft... changes in the magnitude and/or direction of the magnetic field generated by a magnet
Data Source
AI summary
An actuator assembly comprises: a rotatable shaft, a magnet mounted to the rotatable shaft, non-magnet material positioned between the magnet and the shaft, a rotary sensor configured to be responsive to rotation of the magnet for generating a signal, and a housing comprising a magnetic shield surrounding at least a part of the rotary sensor and at least a part of the magnet mounted to the shaft to shield the sensor and the magnet from an external magnetic field. The actuator assembly further comprises a magnet holder fixing the magnet to the shaft. The magnetic shield encompasses the magnetic flux from the magnet to the rotary sensor and also shields the rotary sensor from any external magnetic field such as stray field or magnetic field from the outside of the housing. The non-magnetic material may reduce leakage magnetic flux from the magnet to the shaft.