Magnetic Field Sensor Absolute Angle Detection at Zero Speed
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Solution Overview
Problem
Conventional magnetic field sensors fail to provide accurate absolute angle rotation information immediately upon movement from zero rotating speed or before slowing to zero, and they cannot identify the absolute or relative angle of rotation when the object is stationary, leading to inaccuracies in engine control systems.
Innovation Solution
A magnetic field sensor utilizing a circular vertical Hall (CVH) structure with multiple vertical Hall elements and a thresholding processor to generate a signal representative of the absolute angle of rotation continuously, even at zero speed, and output signals similar to those of a true power on state (TPOS) detector, allowing for accurate angle detection and rotation speed/dirction identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a running mode detector using PDAC and NDAC is used to track positive and negative peaks of magnetic field signal, then the sensor can provide rotation information during substantial rotation, but the output signal is not accurate immediately upon movement from zero rotating speed or before slowing to zero
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing threshold values corresponding to different absolute angle positions before the sensor begins operation. This allows the sensor to immediately compare the magnetic field signal against appropriate thresholds without requiring several cycles of signal peaks to occur first, thereby providing accurate absolute angle information from the very beginning of rotation or upon startup.
Solution Approach 2:
The patent implements dynamics by switching between two detection modes: a true power-on state (TPOS) detector for initial startup and low-speed conditions, and a running mode detector for substantial rotation. This dynamic mode switching optimizes measurement accuracy across different operating conditions, ensuring precise absolute angle information is provided whether the object is stationary, starting, running, or stopping.
2Measurement precision
If a TPOS detector is used to provide accurate output signal shortly after movement from zero rotating speed, then the sensor can provide absolute angle information at low speeds, but the sensor cannot identify absolute or relative angle of rotation when the object is stationary
Solution Approach 1:
The patent applies universality by designing a sensor system that performs multiple functions through the combination of TPOS detector and running mode detector. The TPOS detector handles startup and low-speed conditions by providing absolute angle information from a known reference position, while the running mode detector handles substantial rotation. The system universally covers all operating conditions including stationary, startup, low-speed, and high-speed rotation.
Solution Approach 2:
The patent uses an intermediary approach by introducing a mode selection mechanism that determines which detector output to use based on the current operating condition. This intermediary layer mediates between the TPOS detector and running mode detector, selecting the appropriate source of absolute angle information depending on whether the object is stationary, starting, or rotating substantially, thereby providing continuous accurate measurement across all states.
3Measurement precision
If conventional magnetic field sensors are used, then the device complexity is low, but the sensor cannot provide accurate absolute angle information immediately upon movement from zero speed or when stationary
Solution Approach 1:
The patent applies segmentation by dividing the sensor system into two functional segments: a TPOS detector segment for startup and low-speed conditions, and a running mode detector segment for substantial rotation. Each segment is optimized for its specific operating condition, and their outputs are combined through a mode selection mechanism. This segmentation allows accurate absolute angle measurement across all conditions while keeping each individual segment relatively simple.
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
Enables continuous and accurate absolute angle rotation sensing, even at low speeds or when stationary, with output signals compatible with existing engine control systems, improving the precision of engine timing and fuel injection control.
Implementation Method 1
The sensor includes a magnet configured to generate a magnetic field and a plurality of vertical Hall elements arranged in a circular pattern and responsive to the magnetic field
Data Source
Figure 1
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Figure 4~4A
AI summary
A magnetic field sensor (10) uses an angle sensor (72/172) to measure an angle of rotation of a target object to which a magnet (74) is attached. The angle sensor in combination with electronics (188) generates an angle sensor output signal (198a) related to a direction of a magnetic field of the magnet. The angle sensor output signal is compared with thresholds (Th1 to Th4) to generate a magnetic field sensor output signal the same as a known true power on state (TPOS) sensor output signal. A corresponding method is also described.