Inductive Steering Torque Sensor With Ferrite Shielding
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Solution Overview
Problem
Existing inductive sensors in steering systems face interference issues due to their shared electromagnetic field, making it difficult to accurately determine the angular deflection and torque applied to the steering wheel, and they lack the ability to track the absolute angular position of the vehicle wheels effectively.
Innovation Solution
The design includes non-overlapping receiving coils of different diameters on a PCB with ferrite sheets to minimize interference, and an additional gear-based system with a Hall effect sensor to provide absolute rotational angle measurement, ensuring accurate torque and angle sensing with reduced computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two inductive position sensors are placed in the same area to measure angular deflection, then the measurement capability is improved, but electromagnetic interference between the sensors increases making signal extraction difficult
Solution Approach 1:
The patent positions the two inductive sensors at different radial distances from the torsion bar axis, creating a spatial separation in the radial dimension. This dimensional arrangement allows both sensors to operate in the same general area while experiencing different electromagnetic field strengths, thereby reducing mutual interference and enabling accurate signal extraction for both angular position measurements.
2Measurement precision
If additional computing resources are used to decouple mixed signals from interfering sensors, then signal accuracy is improved, but device complexity increases
Solution Approach 1:
The patent performs signal processing operations directly on the PCB where the sensors are located, rather than relying on post-processing computational algorithms. By implementing filtering and signal extraction circuitry at the source, the system achieves accurate signal decoupling without requiring complex computational resources in the vehicle's management system.
3Measurement precision
If inductive sensors are used to measure angular deflection, then torque measurement capability is improved, but the ability to track absolute angular position over multiple revolutions is lost
Solution Approach 1:
The patent combines two inductive sensors into a single integrated sensor assembly that simultaneously provides both differential angular deflection measurement (for torque) and absolute angular position tracking. By merging the measurement functions of both sensors and processing their combined outputs, the system recovers absolute position information that would otherwise be lost in differential measurements.
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 solution effectively minimizes electrical interference between sensors, providing reliable and accurate measurements of torque and angle, and allows for precise tracking of the steering wheel's rotational position, reducing computational requirements and improving signal clarity.
Implementation Method 1
Each receiving coil, furthermore, comprises a plurality of circumferentially adjacent, oppositely wound coils so that, when excited by a high frequency signal, the voltage output from each receiver coil will vary depending upon the angular position of its associated coupler.
Implementation Method 2
The PCB has two sets of receiving coils... A ferrite sheet is then positioned on the PCB between the two coils.
Data Source
AI summary
A torque sensor for a steering mechanism having an input shaft joined to an output shaft by a torsion bar. A first coupler is connected to the input shaft while a second coupler is connected to the output shaft. A first and second receiving coils, each having a plurality of oppositely wound loops, are arranged adjacent the first and second coils, respectively, while a circuit determines the angular offset between the couplers.