Shaft Angle Measurement Using Dual Magnet Gear Ratio
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Solution Overview
Problem
Existing magnetic sensing technologies, such as GMR sensors, face inefficiencies when mounted on the end of a rotating shaft due to space limitations, particularly in applications like vehicle steering systems where a knuckle assembly impedes such configurations, necessitating improved angle sensing techniques.
Innovation Solution
The use of two magnets rotating at different rates with a predetermined gear ratio, coupled with stationary angle sensors measuring magnetic field directionality, allows for the determination of both relative and absolute angular positions of a rotating shaft, enabling accurate angle measurement systems even in constrained spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GMR sensors are mounted on the end of the shaft on its axis of rotation, then the angular position sensing is achieved, but space limitations prevent this configuration due to interference from the knuckle assembly
Solution Approach 1:
The patent moves the GMR sensor from the traditional axial mounting position (on the shaft end at the axis of rotation) to a radial mounting position (on the shaft surface). This dimensional change allows the sensor to be positioned in a location that does not interfere with the knuckle assembly while still accurately measuring the angular position of the steering shaft.
2Device complexity
If a single GMR sensor is used on the shaft, then the setup is simple, but it cannot provide absolute angular position measurement beyond a single 360° rotation
Solution Approach 1:
The patent combines multiple GMR sensors (at least two sensors positioned at different angular locations on the shaft) to create a sensor array that can determine absolute angular position. By merging the outputs from multiple sensors and using signal processing algorithms, the system achieves absolute position measurement capability while maintaining relative simplicity in the individual sensor elements.
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 enables precise measurement of absolute angular positions by correlating relative angles from multiple sensors, providing flexibility and accuracy in determining shaft positions beyond a single 360° rotation, suitable for various applications including vehicle steering systems.
Implementation Method 1
Magnetic sensing devices, such as Giant Magnetoresistive (GMR) sensors, for example, are used in a wide variety of applications. For example, GMR sensors are often used for sensing the angular position of a rotating shaft.
Data Source
AI summary
Some aspects of the present disclosure relate to techniques for measuring an angular position of a rotating shaft. As will be described in greater detail below, some angle measurement systems of the present disclosure include at least two magnets that cooperatively rotate at different rates according to a predetermined relationship (e.g., a predetermined gear ratio). Two or more magnetic field sensing elements, which are often stationary, measure the directionality of the resultant magnetic field at different positions for a particular angular shaft position. Based on the directionality measured by the magnetic field sensing elements, the techniques can determine an absolute angular position of the rotating shaft, which can be greater than three-hundred and sixty degrees.