Magnetic Position Sensing Using In-Plane Field Gradients
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Solution Overview
Problem
Magnetic position sensor systems are sensitive to external disturbance fields, leading to position errors, and existing solutions compromise the signal-to-noise ratio when attempting to reduce this sensitivity.
Innovation Solution
A position sensor system using two distinct magnetic sensors spaced apart by a predefined distance, measuring in-plane magnetic field gradients to determine out-of-plane position, reducing sensitivity to external disturbances while maintaining a high signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single magnetic sensor is used to measure out-of-plane position based on amplitude of Bz field component, then the measurement is simple, but the system is highly sensitive to external disturbance fields resulting in position errors
Solution Approach 1:
The system divides the measurement function into two separate magnetic sensors instead of using a single sensor. Each sensor measures in-plane magnetic field components, and the controller calculates the out-of-plane position based on the difference between these measurements, thereby segmenting the measurement process to achieve disturbance rejection
Solution Approach 2:
The controller acts as an intermediary that processes the measurements from two separate sensors. By calculating the difference between measurements from two sensors positioned at different locations, the system eliminates the common-mode external disturbance field and isolates the signal related to the out-of-plane position
2Object-affected harmful factors
If two separate magnetic sensors are used to reduce sensitivity to disturbance fields, then the sensitivity to external fields is reduced, but the device complexity increases
Solution Approach 1:
The system uses two separate magnetic sensors positioned at different locations to measure in-plane magnetic field components. This segmentation allows the system to reject external disturbance fields by taking the difference between the two measurements, while the complexity is managed through a straightforward controller algorithm
Solution Approach 2:
The system changes the measurement parameter from directly measuring the out-of-plane Bz component to measuring in-plane components at two different locations. This parameter change enables disturbance rejection while maintaining a relatively simple device architecture
3Measurement precision
If in-plane field gradients are measured using two sensors spaced apart, then the signal-to-noise ratio is improved, but the distance between sensors must be precisely controlled
Solution Approach 1:
The system incorporates a lookup table that stores pre-calculated position information corresponding to different sensor spacing values. The controller uses this lookup table to compensate for variations in the actual distance between sensors, thereby maintaining measurement accuracy without requiring extremely precise manufacturing tolerances
Solution Approach 2:
The system performs preliminary calculations during the manufacturing or calibration phase to create a lookup table that accounts for the specific sensor spacing. This preliminary action allows the system to operate accurately with a range of spacing values without requiring precise real-time measurement of the sensor distance
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 determines out-of-plane position with reduced sensitivity to external fields and maintains a high signal-to-noise ratio by calculating in-plane field gradients using a two-step approach with separate sensors, enhancing accuracy and robustness.
Implementation Method 1
a first magnetic sensor (102, 202), distinct from a second magnetic sensor (103, 203), both adapted for measuring only one magnetic field component in a plane
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3~4
AI summary
A position sensor system (200) for measuring a position (Z) of a target (220) movable outside a plane (230), the system (200) comprising: a first magnetic sensor (201) and a second magnetic sensor (202) fixedly arranged in said plane (230) and spaced apart by a distance (D); the first respectively second magnetic sensor (201, 202) adapted for measuring at least one first respectively second in-plane magnetic field component (Bu1, Bv1),(Bu2,Bv2) in said plane to obtain at least a first respectively second value; a controller (240) connected to the sensors for obtaining said values, and adapted for determining the out-of-plane position (Z) as a function of the values and of the predefined distance (D). A method (1200) of determining said position.