Electric Power Steering Assist Compensation for Road Feedback
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Solution Overview
Problem
Conventional electric power steering systems suppress road-surface input torque, considering it unnecessary, which hinders the driver's ability to feel grip and vehicle vibrations, making steering less intuitive.
Innovation Solution
An electric power steering control apparatus that calculates an assist compensation amount using two signals to transmit road-surface input torque effectively, ensuring the driver feels road grip and vibrations, while suppressing frequency alterations at resonance points due to vehicle-state variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If road-surface input torque is suppressed from being transmitted to the steering wheel, then steering wheel manipulation is assisted more effectively, but the driver cannot feel road grip and vehicle vibrations
Solution Approach 1:
The patent inverts the conventional approach by not suppressing road-surface input torque but rather transmitting it to the steering wheel. The control unit allows road-surface input torque to be transmitted while still providing motor assist, enabling drivers to feel road grip and vehicle vibrations through the steering wheel, thus resolving the contradiction between ease of operation and information loss
Solution Approach 2:
The patent changes the control parameter from complete suppression of road-surface torque to selective transmission. By adjusting the control strategy to transmit road-surface input torque while maintaining motor assist functionality, the system achieves both easy steering operation and preservation of road surface information feedback
2Loss of information
If road-surface input torque is transmitted to the steering wheel, then drivers can feel road grip and vibrations, but steering wheel manipulation becomes harder
Solution Approach 1:
The patent merges two functions: motor assist for easy steering and road-surface torque transmission for information feedback. The control unit combines these functions by providing motor assist while simultaneously transmitting road-surface input torque to the steering wheel, achieving both ease of operation and information preservation without compromise
3Reliability
If assist compensation amount is calculated using multiple signals, then steering control is improved, but system complexity increases
Solution Approach 1:
The control unit performs multiple functions using the same hardware components. It calculates assist compensation amounts based on multiple signals (steering wheel torque, motor torque, motor speed) and uses this information for both steering assist control and road-surface torque transmission, achieving improved reliability without proportionally increasing device complexity
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
Facilitates easier steering by transmitting road-surface input torque and stabilizing the steering system, allowing drivers to feel road grip and vehicle vibrations, thereby enhancing steering control and reducing resonance frequency variations.
Implementation Method 1
a torque detector detecting torque applied to a torsion bar on the basis of a torsion angle of the torsion bar
Data Source
AI summary
An electric power steering system includes a basic assist amount calculation section calculating a basic assist amount for assisting the manipulation of a steering wheel, and an assist compensation amount calculation section calculating an assist compensation amount for correcting the basic assist amount. The system includes an assist amount correction section calculating a corrected assist amount by correcting the basic assist amount based on the assist compensation amount, and a motor drive section driving a motor using the corrected assist amount. The assist compensation amount calculation section uses a reverse input specification that more transmits the signal components of specific frequency in road-surface input torque, to a steering wheel than in the case of using only the basic assist amount, and calculates the assist compensation amount suitable for a vehicle-state value, such as a steering torque, to suppress variation in the transmission characteristics due to variation of the vehicle-state value.