GMR Wheel Speed Sensor Using Earth's Magnetic Field
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Solution Overview
Problem
Conventional magnetic sensor systems for detecting vehicle wheel speed and acceleration are complex, costly to manufacture, and only measure rotational speed, lacking the capability to detect acceleration.
Innovation Solution
A magnetic sensor unit utilizing a Wheatstone bridge circuit with GMR sensor elements, which generates a differential voltage based on changes in the external magnetic field, allowing for the calculation of both speed and acceleration by a processor, without the need for additional magnets or magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic encoder wheels with alternating north and south poles are used, then rotational speed can be detected, but the system becomes complex and expensive to manufacture
Solution Approach 1:
The patent extracts the magnetization from the encoder wheel itself and uses the Earth's magnetic field instead. The encoder wheel retains only the magnetic sensor and processing circuitry, while the magnetic field source (Earth's field) is external and requires no additional components in the system.
Solution Approach 2:
The patent introduces the Earth's magnetic field as an intermediary between the encoder wheel and the magnetic sensor. This external magnetic field serves as the reference field that the sensor detects, eliminating the need for complex alternating pole structures on the wheel.
2Measurement precision
If conventional magnetic encoder wheels with alternating north and south poles are used, then rotational speed can be detected, but manufacturing costs increase
Solution Approach 1:
The patent extracts the magnetization from the encoder wheel itself and uses the Earth's magnetic field instead. The encoder wheel retains only the magnetic sensor and processing circuitry, while the magnetic field source (Earth's field) is external and requires no additional components in the system.
Solution Approach 2:
The patent replaces expensive magnetized encoder wheels with alternating poles with a simpler encoder wheel that uses the free, ubiquitous Earth's magnetic field. This substitution dramatically reduces manufacturing costs while maintaining measurement functionality.
3Measurement precision
If conventional speed sensor devices are used, then rotational speed can be detected, but acceleration detection capability is lost
Solution Approach 1:
The patent makes the speed sensor device universal by enabling it to perform both speed detection and acceleration detection functions. The same magnetic sensor and processing circuitry that detect rotational speed can also calculate acceleration by analyzing changes in speed over time, eliminating the need for separate sensors.
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 simplifies the detection of both speed and acceleration, reduces manufacturing costs, and provides accurate measurements using the earth's magnetic field, making it suitable for various applications beyond vehicles.
Implementation Method 1
each be formed by one GMR (giant magneto resistance) sensor element, the GMR sensor element changing its resistance based on a change in magnetic field intensity with respect to an external magnetic field
Implementation Method 2
A Hall effect transducer uses a transverse current flow that occurs in the presence of a magnetic field. Applying a direct current (DC) voltage at both ends of the Hall effect transducer creates a longitudinal current flow over its body. With the presence of the magnetic field, a transverse voltage is induced in the Hall effect transducer
Data Source
AI summary
Systems and/or methods for detecting a rotating wheel's speed and/or acceleration are provided. A sensor is attached to the rotating wheel. The sensor includes a circuit (e.g. a Wheatstone bridge circuit) having a plurality of resistors (e.g. 4 resistors). Each resistor includes a giant magnetoresistance (GMR) element and has a resistance changeable based at least in part on a change in magnetic field intensity with respect to an external magnetic field. The sensor generates a signal based at least in part on the resistors' resistances. A processor is operable to calculate the rotating wheel's speed and/or acceleration based at least in part on the signal.