Rotating Field Sensor Angle Determination Using Multiple Detection Circuits
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Solution Overview
Problem
Existing rotating field sensors fail to accurately determine the angle of a rotating magnetic field when one of the detection circuits malfunctions, especially if the failure is subtle, such as a short circuit or anisotropy in magnetoresistive films, leading to incorrect angle detection values.
Innovation Solution
A rotating field sensor with multiple detection circuits and an angle calculation unit that calculates multiple angle values from groups of detection circuits, allowing for the identification of correct angle values even if one circuit fails, using angle differences to determine accurate angle detection values and potentially identifying the failed circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple detection circuits are used to improve reliability, then the system can tolerate failures, but the device complexity increases
Solution Approach 1:
The sensor is divided into multiple independent detection circuits (first, second, third, and fourth detection circuits), each capable of independently detecting the rotating magnetic field. This segmentation allows the system to tolerate failures in individual circuits while maintaining overall functionality, directly resolving the contradiction between reliability and complexity by distributing detection functions across multiple independent units.
Solution Approach 2:
The system changes the parameter of detection circuit quantity from a single circuit to multiple circuits (specifically four circuits arranged at different positions). This parameter change enables the system to achieve fault tolerance, where the angle detection can continue using remaining functional circuits even when one or more circuits fail, thus improving reliability without requiring complete system redundancy.
2Measurement precision
If traditional failure detection methods are used, then obvious failures can be detected, but subtle failures such as short circuits or anisotropy in magnetoresistive films cannot be detected
Solution Approach 1:
The system implements feedback by continuously monitoring the output signals from multiple detection circuits and comparing them against expected relationships (such as phase differences and amplitude relationships). When discrepancies are detected that indicate subtle failures like short circuits or anisotropy in magnetoresistive films, the system can identify and exclude affected circuits from angle calculation, enabling detection of subtle failures that traditional methods miss.
Solution Approach 2:
The four detection circuits are positioned asymmetrically at different locations around the rotating magnetic field source, with each circuit oriented at different angles. This asymmetric arrangement ensures that when one circuit experiences a subtle failure, the other circuits provide complementary detection data that can reveal the failure through inconsistency analysis, thereby improving failure detection precision for subtle defects.
3Device complexity
If only two bridge circuits are used to simplify the structure, then the device complexity is reduced, but the system cannot tolerate any circuit failures
Solution Approach 1:
Instead of using two bridge circuits as in traditional designs, the system segments the detection function into four independent detection circuits. Each circuit can be implemented as a bridge circuit, but the increased number of segments provides fault tolerance capability. When one circuit fails, the system can continue operating using the remaining functional circuits, resolving the contradiction by showing that moderate increases in circuit quantity provide both fault tolerance and acceptable complexity levels.
Solution Approach 2:
The system prepares for potential failures by having more detection circuits than strictly necessary for basic functionality. This beforehand cushioning approach ensures that even if one or more circuits fail, the system maintains sufficient detection capability to determine rotational angle accurately, thus achieving fault tolerance while keeping the complexity increase within acceptable bounds.
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 the determination of correct angle detection values even if one detection circuit fails, ensuring accurate rotational position sensing in applications like automotive steering systems by using multiple angle values and angle differences to compensate for faulty circuits.
Implementation Method 1
A known magnetic detection element for use in a bridge circuit is a magnetoresistive (MR) element that is formed by serially connecting a plurality of MR films each of which exhibits a magnetoresistive effect
Data Source
AI summary
A rotating field sensor includes four detection circuits each of which generates an output signal responsive to the direction of a rotating magnetic field, and an angle calculation unit configured to calculate four angle values in correspondence to four groups each consisting of two detection circuits selected from the four detection circuits. The angle calculation unit calculates each of the four angle values on the basis of two output signals of the two detection circuits constituting a corresponding one of the four groups.