Grooved Magnetic Structure for Position Sensor Error Reduction
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Solution Overview
Problem
Magnetic position sensor systems face challenges in achieving high accuracy and reducing position errors without increasing processing resources or storage capacity, especially in automotive applications where robustness against external disturbance fields is crucial.
Innovation Solution
The system employs a magnetic structure with strategically placed grooves on the magnet surface and an off-axis sensor device configuration, measuring magnetic field components or gradients to calculate angular or linear positions using predefined functions, thereby reducing position errors and enhancing robustness against external fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex algorithms or additional sensor elements are used to reduce position errors and improve accuracy, then measurement precision improves, but device complexity and processing resources increase
Solution Approach 1:
The magnet is divided into multiple poles (at least two poles) with distinct magnetic polarities. This segmentation creates a non-uniform magnetic field pattern that enables more accurate position detection through simple sensor element measurements, reducing the need for complex correction algorithms
Solution Approach 2:
The sensor elements are positioned at a specific radial distance from the rotation axis (at least 1.6 mm) where the magnetic field has optimal characteristics for measurement. This localized positioning ensures that the magnetic field gradient at the sensor location provides maximum measurement precision without requiring complex field distribution management
Solution Approach 3:
The patent transitions from measuring only magnetic field components to measuring magnetic field gradients (spatial derivatives of the magnetic field). This dimensional change in the measurement approach provides more information about the magnetic field structure, enabling accurate position determination with simpler processing
2Measurement precision
If processing resources and storage capacity are increased to reduce position errors, then measurement precision improves, but use of energy and system cost increase
Solution Approach 1:
The magnetic field structure is pre-configured with multiple poles and specific geometries that inherently produce measurement signals suitable for accurate position calculation. The grooves and pole arrangements are designed in advance to create optimal magnetic field patterns, eliminating the need for complex real-time processing or calibration procedures
Solution Approach 2:
The magnetic field structure self-corrects for common errors such as axial and radial offsets through its symmetric multi-pole configuration. The geometric arrangement of poles and grooves automatically compensates for position errors, reducing the need for additional processing resources or storage for correction data
3Reliability
If robustness against external disturbance fields is improved through complex algorithms or additional sensors, then reliability improves, but device complexity increases
Solution Approach 1:
The magnetic field structure employs asymmetric groove patterns and non-uniform pole distributions that create a distinctive magnetic field signature. This asymmetry makes the measurement signals highly characteristic of the intended magnetic field source, enabling the system to distinguish between desired signals and external disturbance fields without complex filtering algorithms
Solution Approach 2:
By measuring magnetic field gradients rather than just field components, the system gains an additional dimensional perspective on the magnetic field structure. This enables the detection of subtle differences between the intended multi-pole field pattern and external disturbance fields, improving robustness through enhanced signal discrimination
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 approach significantly reduces position errors by at least a factor of 2 to 10, improves accuracy to less than 1°, and maintains robustness against external disturbances without increasing processing power or storage, making it suitable for automotive applications.
Implementation Method 1
a non-uniform magnetic field is generated (e.g. by means of a permanent magnet) and is measured by a sensor device comprising one or more sensor elements
Data Source
Figure 1(a)~2(b)
Figure 3(a)~3(c)
Figure 3(d)~3(f)
AI summary
A linear or angular position sensor system comprising a magnetic structure for generating a magnetic field, and a sensor device movable relative to the magnetic structure. The sensor device comprises a plurality of sensor elements for measuring at least two characteristics of said magnetic field, and a processing circuit for determining a linear or angular position of the sensor device relative to the magnetic structure in accordance with a predefined function of these characteristics (e.g. components or gradients). The magnetic structure comprises one or more grooves, having a shape and size which can be described by a limited set of parameters, having values optimized to reduce a maximum error between the actual position of the sensor device, and the calculated position based on said predefined function, by at least a factor of 2.