Steer-by-Wire Feedback Control for Automatic Driving
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Solution Overview
Problem
Steer-by-wire systems in vehicles face issues with driver discomfort during automatic driving modes due to vigorous steering wheel rotation and lack of feedback, and challenging transitions between automatic and manual driving modes, which can lead to safety hazards.
Innovation Solution
A method for controlling steer-by-wire systems that includes an automatic driving electronic control unit determining the drive mode and adjusting the steering device's rotation based on pre-set functions, with a factor less than one in automatic mode to reduce steering device movement, and an optional electronic clutch for decoupling the steering wheel from road wheel movement when desired.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steering wheel is mechanically coupled to road wheels in conventional systems, then the driver receives natural feedback, but steer-by-wire systems lack this mechanical link causing driver discomfort and confusion
Solution Approach 1:
The patent introduces an electronic intermediary system that mediates between the steering wheel and road wheels. The control unit processes steering wheel position data and generates corresponding road wheel position commands, creating a virtual mechanical coupling that provides driver feedback while maintaining the steer-by-wire architecture's safety benefits
Solution Approach 2:
The system implements a feedback mechanism where the control unit continuously monitors steering wheel position and communicates corresponding road wheel position information back to the driver through the steering wheel. This creates a closed-loop system that simulates natural mechanical feedback, resolving the contradiction between safety and driver comfort
2Ease of operation
If the steering wheel follows road wheel movement in automatic mode, then the driver receives feedback, but the steering wheel rotates vigorously causing distraction and potential injury
Solution Approach 1:
The patent implements dynamic control of the steering wheel based on driving mode. In automatic mode, the control unit dynamically adjusts the steering wheel position with reduced rotation range compared to manual mode. This dynamic adaptation provides necessary feedback while preventing excessive rotation that could cause driver distraction or injury
Solution Approach 2:
The system changes the parameter of steering wheel rotation range based on the detected driving mode. In automatic mode, the maximum rotation angle is limited to a smaller value, while in manual mode, the full rotation range is available. This parameter adjustment resolves the contradiction between providing feedback and preventing harmful effects
3Object-affected harmful factors
If a clutch is used to separate steering wheel from road wheels, then the steering wheel can stand still, but the driver loses feedback and transitions cause large offsets
Solution Approach 1:
The patent replaces the mechanical clutch system with an electronic control system. Instead of physically disconnecting the steering wheel from road wheels, the control unit electronically manages the connection, maintaining continuous feedback while enabling safe decoupling when needed. This substitution eliminates the information loss and transition offset problems associated with mechanical clutches
4Reliability
If the steering wheel is completely decoupled from road wheels, then driver safety is improved, but the driver receives no feedback of road wheel movement
Solution Approach 1:
The system implements an electronic feedback mechanism where the control unit receives road wheel position data and transmits this information back to the steering wheel control system. This creates a virtual feedback loop that maintains driver awareness of road wheel movement while keeping the physical steering wheel decoupled from direct mechanical connection, thus ensuring both safety and information flow
Data Source
AI summary
A steer-by-wire steering system may include an actuation control system to actuate road wheels via a rack and pinion steering gear and a steering wheel control system to simulate a steering feel of a mechanically linked steering system to a steering device. The actuation control system may have a second control unit, and the steering wheel control system may have a first control unit and an actuator. An automatic driving electronic control unit may decide if a drive mode is vehicle-controlled or driver-controlled. If driver-controlled, the first control unit may rotate the steering wheel by a turning angle by activating the actuator according to a pre-set function depending on a rotation angle of a pinion to simulate the steering feel. If vehicle-controlled, the first control unit may rotate the steering wheel by a reduced turning angle by activating the actuator according to a fraction of the pre-set function.