Electric Power Steering Angle Verification via PWM Signal Averaging
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Solution Overview
Problem
The existing electric power steering systems face challenges in ensuring high reliability of the absolute steering angle calculation, particularly in emergency situations, due to the limitations of torque sensors using hall ICs for measuring absolute angles.
Innovation Solution
The system incorporates a torque sensor with a first and second rotor, angle devices for measuring absolute and relative steering angles, and an electronic control unit that determines a reference steering angle, generates PWM signals, and verifies differences between these angles to calculate a final absolute steering angle by averaging measurements, while also providing warning outputs for abnormal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a torque sensor using one hall IC is used to measure absolute steering angle, then the device complexity is reduced, but the reliability of the absolute steering angle measurement deteriorates
Solution Approach 1:
The patent creates a virtual copy of the absolute steering angle measurement by generating a PWM signal from the single hall IC measurement and comparing it with the accumulated relative steering angle. This virtual copy allows verification of the absolute angle without adding a second physical hall IC, thus maintaining low device complexity while improving reliability through redundant measurement paths.
Solution Approach 2:
The patent introduces a PWM signal as an intermediary between the single hall IC measurement and the final absolute steering angle verification. The PWM signal serves as a mediating representation that can be compared with the relative steering angle accumulation, enabling reliability verification without direct dual-sensor comparison.
2Reliability
If verification of absolute steering angle is implemented, then the reliability is improved, but the processing time and complexity increase
Solution Approach 1:
The patent performs preliminary accumulation of relative steering angles during normal operation before verification is needed. This pre-computed relative angle data is readily available when verification is required, eliminating the need for real-time calculation during the verification process and reducing processing time.
Solution Approach 2:
The patent implements a feedback mechanism where the PWM signal (derived from absolute angle) is continuously compared with the accumulated relative angle, and the difference is used to verify measurement reliability. This feedback loop enables automatic verification without manual intervention or complex processing.
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 approach enhances the reliability of the absolute steering angle calculation, ensuring fail-safety and providing accurate steering conditions by averaging redundant angle measurements and outputting warning information for abnormal states, thus improving the overall stability and safety of the electric power steering system.
Implementation Method 1
a first angle device configured to measure an absolute steering angle of the first rotor
Implementation Method 2
second and third angle devices configured to measure a relative steering angle of the second rotor
Implementation Method 3
a first tracing unit (a first angle follower) configured to generate a PWM signal based on the absolute steering angle and the reference steering angle
Data Source
AI summary
The present invention provides a system and method of providing high reliability for an absolute angle in an electric power steering system in which the final absolute steering angle is calculated using a device configured to measure an absolute steering angle and a relative steering angle.