Rotation Detection Device for Electric Power Steering
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Solution Overview
Problem
Existing rotation detection devices for electric power steering systems face challenges in accurately calculating absolute angles and counting rotations due to limitations in sensor precision and noise interference, which can lead to errors in steering control.
Innovation Solution
A rotation detection device comprising plural sensor units and a control unit that acquires and processes first rotation information related to the rotation angle and second rotation information related to the number of rotations, using magnetic field detection elements and signal processing units to calculate absolute angles and count values, with phase difference correction and redundant configurations to enhance accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional rotation angle sensors are used to detect motor rotation, then basic rotation information can be obtained, but measurement precision and reliability are insufficient due to sensor precision limitations and noise interference
Solution Approach 1:
The patent divides the rotation detection function into two independent sensor units, each with its own detection elements. The first sensor unit detects rotation angle within one rotation (0-360 degrees), while the second sensor unit detects the number of rotations. This segmentation allows each sensor to be optimized for its specific function, improving overall measurement precision and reliability by reducing the complexity and error potential of a single comprehensive sensor system.
2Loss of information
If absolute angle calculation is performed based on rotation angle and number of rotations, then complete rotation information can be obtained, but calculation errors may occur due to noise interference and sensor precision limitations
Solution Approach 1:
The control unit continuously monitors the relationship between the first rotation information (rotation angle) and second rotation information (number of rotations) and performs feedback correction. When the calculated absolute angle shows discontinuities or inconsistencies, the system uses the complementary information from both sensors to correct errors and ensure continuous, accurate absolute angle measurement throughout the motor's rotation range.
Solution Approach 2:
The patent changes the measurement parameters by using two different sensor configurations that measure different aspects of rotation. The first sensor measures angular position within a single rotation cycle, while the second sensor measures cumulative rotation cycles. By combining these different parameter measurements, the system achieves accurate absolute angle calculation that overcomes the precision limitations of individual sensors.
3Reliability
If redundant sensor units are added to improve accuracy, then measurement reliability increases, but device complexity increases
Solution Approach 1:
Each sensor unit is designed with multi-functionality to reduce overall system complexity. The detection elements can detect both rotation angle and number of rotations depending on the specific sensor configuration and signal processing applied. This universal design approach allows the system to achieve redundant measurement capability without proportionally increasing the number of different sensor types or complexity of individual sensor units.
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 effectively calculates absolute angles and counts rotations with improved accuracy, reducing errors and noise interference, thereby enhancing the precision and reliability of steering control in electric power steering systems.
Implementation Method 1
Each sensor unit includes at least one detection element for detecting a rotation of a motor
Data Source
AI summary
An ECU includes plural sensor units and plural control units. The sensor units include magnetic field detection elements for detecting a rotation of a motor, and output mechanical angles related to the rotation angle in one rotation and count values related to the number of rotations of the motor, respectively. One rotation of the motor is divided into indefinite regions, in which detection deviation of the count values may occur, and definite regions, in which no detection deviation occurs. The definite region of the count value is set to deviate from the definite region of the other count value. Absolute angle calculation units calculate the absolute angles using the count values of the definite regions.