Joystick Magnet Orientation Sensing via Magnetic Field Gradients
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Solution Overview
Problem
Magnetic position sensor systems that measure the orientation of a pivotable magnet about a fixed reference point face challenges in achieving high accuracy and robustness against external disturbance fields, especially when the magnet has two degrees of freedom.
Innovation Solution
A sensor device comprising a semiconductor substrate with magnetic sensors configured to determine specific magnetic field gradients, and a processing circuit to calculate angles based on these gradients, providing a robust method for determining the orientation of a cylindrical or axially magnetized magnet, even in the presence of external disturbance fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors measure magnetic field components directly, then the system structure is simple, but the measurement accuracy deteriorates due to sensitivity to external disturbance fields
Solution Approach 1:
The patent transforms the measurement parameter from direct magnetic field components (Bx, By, Bz) to magnetic field gradients (dBx/dx, dBy/dy, dBz/dx, dBz/dy). This parameter transformation fundamentally changes the measurement characteristics, making the system insensitive to external disturbance fields while maintaining the ability to accurately determine magnet orientation angles α and β.
Solution Approach 2:
The patent introduces a new measurement dimension by measuring magnetic field gradients instead of field components. The gradient measurements provide additional spatial information that enables calculation of orientation angles through specific mathematical relationships, creating a more robust measurement system that operates in gradient space rather than field component space.
2Adaptability or versatility
If the magnet has two degrees of freedom, then the measurement capability is improved, but the device complexity increases
Solution Approach 1:
The patent creates a universal measurement system where four magnetic gradient sensors can measure two different orientation angles (α and β) simultaneously. The same sensor array and processing circuitry handle both degrees of freedom, making the system multi-functional without proportionally increasing complexity. The processing circuit calculates both angles from the same gradient measurements.
3Reliability
If magnetic field gradients are measured to reduce disturbance sensitivity, then robustness is improved, but the device complexity increases
Solution Approach 1:
The patent segments the measurement function across four distinct sensor locations, with each sensor measuring gradients in specific directions. This segmentation allows the system to capture the necessary gradient information (dBx/dx, dBy/dy, dBz/dx, dBz/dy) through distributed measurements, improving robustness while organizing complexity into manageable modular sensor units.
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 enables accurate determination of the orientation of a magnet with two degrees of freedom, significantly reducing sensitivity to external disturbance fields and improving measurement accuracy, making it suitable for applications like joysticks.
Implementation Method 1
a first magnetic field gradient (dBx/dx) of a first magnetic field component (Bx) oriented in a first direction (X) parallel to the semiconductor substrate along said first direction; and a second magnetic field gradient (dBy/dy) of a second magnetic field component (By) oriented in a second direction (Y) parallel to the semiconductor substrate and perpendicular to the first direction (X), along said second direction (Y)
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(d)
AI summary
A method of determining an orientation (α,β) of a magnet which is pivotable about a reference position (Pref) having a predefined position relative to a semiconductor substrate, comprising: a) determining a first magnetic field gradient (dBx/dx); b) determining a second magnetic field gradient (dBy/dy); c) determining a third magnetic field gradient (dBz/dx); d) determining a fourth magnetic field gradient (dBz/dy); e) determining a first angle (α) based on at least some of said magnetic field gradients; f) determining a second angle (β) based on at least some of said magnetic field gradients. A sensor device configured for performing this method. A sensor system comprising such sensor device and a magnet, optionally connected to a joystick.