Magnetic Field Sensor High-Resolution Mode Using Pulse Width Encoding
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Solution Overview
Problem
Magnetic field sensors lack the capability to output high-resolution signals, which are essential for accurate measurements and additional information derivation, particularly in applications like autonomous driving and parking, where precise wheel speed detection is critical.
Innovation Solution
A magnetic field sensor system comprising a sensor unit and a processing circuit that generates oscillation signals fluctuating around a mean value, with distinct pulse widths for mean value and limit value crossings to indicate high-resolution mode, enabling the generation of high-resolution output signals using a PWM protocol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field sensor uses a conventional PWM protocol with only mean value crossing pulses, then the device complexity is low and ease of operation is high, but the measurement precision is insufficient for high-resolution applications
Solution Approach 1:
The patent segments the oscillation signal evaluation into multiple discrete crossing events (mean value crossings and limit value crossings), where each crossing generates a separate pulse in the output signal. This segmentation enables high-resolution measurement by capturing multiple signal characteristics per oscillation cycle, while the processing circuit maintains relatively simple logic for generating and interpreting these segmented pulses.
2Loss of information
If a magnetic field sensor generates only mean value crossing pulses, then the device complexity is low, but the quantity of information provided to the receiver is insufficient
Solution Approach 1:
The patent adds another dimension to the output signal by incorporating limit value crossing pulses in addition to the conventional mean value crossing pulses. This dimensional expansion of the signal structure enables the transmission of additional information about the oscillation signal characteristics without significantly increasing processing circuit complexity, as both pulse types are generated using similar pulse generation logic.
3Measurement precision
If a magnetic field sensor operates in high-resolution mode across the entire vehicle speed range, then the measurement precision is improved at low speeds, but the risk of incorrect values and reliability issues increases
Solution Approach 1:
The patent implements a dynamic resolution mode that automatically adapts to the current operating conditions, specifically the detected wheel speed. At higher speeds where conventional resolution suffices, the sensor operates in standard mode for reliable operation. At lower speeds where high precision is critical, the sensor switches to high-resolution mode utilizing both mean value and limit value crossing pulses. This dynamic adaptation ensures measurement precision is improved when needed while maintaining reliability across the entire vehicle speed range.
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 allows for recognizable high-resolution output signals, enhancing measurement accuracy and enabling the derivation of additional information such as jitter values, with the capability to operate in high-resolution mode over the entire vehicle speed range, reducing the risk of incorrect values at lower speeds.
Implementation Method 1
a sensor unit (10) which is designed to generate on the basis of a varying magnetic field an oscillation signal (14) that fluctuates around a mean value
Data Source
AI summary
A magnetic field sensor includes a sensor and a processing circuit. The sensor is designed to generate on the basis of a varying magnetic field an oscillation signal that fluctuates around a mean value. The processing circuit is designed to generate an output signal on the basis of the oscillation signal. The processing circuit is designed, in a high-resolution mode different than a low-resolution mode, in each case to generate a mean value crossing pulse in the output signal when the oscillation signal attains the mean value, and to generate in each case a limit value crossing pulse in the output signal when the oscillation signal attains at least one limit value different than the mean value. A pulse width of at least either the mean value crossing pulse or the limit value crossing pulse is set to indicate that the magnetic field sensor is operating in the high-resolution mode.