Clutch Actuator Position Sensor Stray Field Compensation
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Solution Overview
Problem
Magnetic field sensors in automotive transmissions are susceptible to stray magnetic fields, leading to inaccurate position measurements due to interference, which current shielding methods cannot fully address without adding weight and occupying space.
Innovation Solution
An additional dedicated magnetic field sensor is used to detect ambient magnetic fields and provide a signal to a compensating circuit to cancel out stray fields, improving the accuracy and reliability of active magnetic field sensors by isolating them from parasitic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetic field shielding materials (mu metal) are provided proximate the magnetic field sensor, then stray magnetic field interference is reduced, but weight increases and space is occupied
Solution Approach 1:
A compensating magnetic field sensor is introduced as an intermediary element to detect stray magnetic fields. The signal from this compensating sensor is then used to mathematically compensate for the interference in the active sensor readings, eliminating the need for physical shielding materials.
Solution Approach 2:
The patent replaces the mechanical/physical shielding approach (using mu metal barriers) with an electronic/software-based compensation system. The compensating sensor and associated signal processing substitute for the physical shielding mechanism.
2Object-affected harmful factors
If magnetic field shielding materials (mu metal) are provided proximate the magnetic field sensor, then stray magnetic field interference is reduced, but device complexity increases
Solution Approach 1:
A compensating magnetic field sensor is introduced as an intermediary element to detect stray magnetic fields. The signal from this compensating sensor is then used to mathematically compensate for the interference in the active sensor readings, eliminating the need for physical shielding materials.
Solution Approach 2:
The patent replaces the mechanical/physical shielding approach (using mu metal barriers) with an electronic/software-based compensation system. The compensating sensor and associated signal processing substitute for the physical shielding mechanism.
3Measurement precision
If additional compensating magnetic field sensors are utilized, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The compensating magnetic field sensor provides feedback information about the stray magnetic field environment. This feedback signal is processed and used to adjust/compensate the readings from the active position sensors, creating a closed-loop system that improves measurement accuracy.
Solution Approach 2:
A compensating magnetic field sensor is introduced as an intermediary element to detect stray magnetic fields. The signal from this compensating sensor is then used to mathematically compensate for the interference in the active sensor readings, eliminating the need for physical shielding materials.
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 eliminates stray magnetic field interference, enhancing the integrity and accuracy of position sensor signals, ensuring precise actuator position detection without increasing weight or occupying additional space.
Implementation Method 1
a permanent magnet is mounted to a translating component such as the actuator piston, the output shaft or an associated shift rail and the magnetic sensor, which is stationary, is secured in proximate, sensing relationship with the permanent magnet to a housing, flange, web or other stationary transmission component. Translation of the permanent magnet thus varies the magnetic field strength sensed by the sensor
Implementation Method 2
provides a signal to a compensating circuit which actively and in real time corrects the signals from the active magnetic field sensors by cancelling out the stray magnetic field as detected by the additional sensor
Data Source
AI summary
A method of improving linear position sensing of clutch actuators with magnetic field sensors utilizes a dedicated magnetic field sensor solely to detect the ambient magnetic field. Typical three position hydraulic clutch actuators include a pair of active magnetic field sensors, one of such active sensors associated with each of a pair of pistons in such actuator and an adjacent pair of permanent magnets, one of such magnets associated with each of such pistons. The invention provides an additional magnetic field sensor disposed proximate the active magnetic field sensors which senses the surrounding (stray, background or parasitic) magnetic field proximate the active magnetic field sensors and provides a signal to an electronic circuit or software which actively and in real time corrects the signals from the active magnetic field sensors by cancelling out the magnitude of the stray magnetic field as detected by the additional sensor.