Steer-by-wire rack-limiting condition detection and torque feedback
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Solution Overview
Problem
Steer-by-wire (SBW) steering systems lack the ability to detect rack-limiting conditions, such as mechanical or environmental restrictions, which prevents the system from providing adequate torque feedback to the driver, leading to potential synchronization issues between the handwheel and roadwheel.
Innovation Solution
A processor-based system that receives handwheel velocity and vehicle speed signals to determine simulated end stop positions and generates feedback signals when the rack position exceeds these limits, allowing for the detection of rack-limiting conditions and providing notification torque to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steer-by-wire system uses electrical signals to connect handwheel and roadwheels without direct mechanical connection, then system reliability and precision are improved, but the driver loses tactile feedback about rack-limiting conditions
Solution Approach 1:
The system implements a feedback mechanism where the processor monitors rack position and compares it with simulated end stop positions, then generates torque feedback signals sent to the handwheel actuator. This closed-loop feedback restores tactile information to the driver about rack-limiting conditions, resolving the information loss caused by eliminating direct mechanical connection.
Solution Approach 2:
The processor acts as an intermediary that detects rack-limiting conditions through electrical signals and translates them into torque feedback. This intermediary component bridges the gap between the electrical signal transmission system and the driver's tactile perception needs, preserving information without requiring direct mechanical connection.
2Loss of information
If the system generates torque feedback for all rack position conditions, then driver awareness is improved, but energy consumption and system complexity increase
Solution Approach 1:
The system applies torque feedback selectively rather than continuously. The processor generates torque feedback signals only when the rack position approaches or exceeds the simulated end stop positions, rather than providing constant feedback. This partial action approach maintains driver awareness of limiting conditions while minimizing unnecessary energy consumption during normal operation.
3Adaptability or versatility
If the system uses simulated end stop positions based on handwheel velocity and vehicle speed, then adaptability to different driving conditions is improved, but measurement and detection complexity increases
Solution Approach 1:
The system dynamically adjusts the simulated end stop positions based on real-time handwheel velocity and vehicle speed inputs. Rather than using fixed thresholds, the processor calculates adaptive limits that respond to changing driving conditions, improving versatility while managing detection complexity through algorithmic approaches.
Data Source
AI summary
Technical solutions are described herein for steer-by-wire (SBW) steering systems to detect a rack-limiting condition and generate feedback signal that can provide responsive handwheel torque for a driver. According to one or more embodiments the steer-by-wire steering system includes a processor that receives input signals comprising a handwheel velocity signal and a vehicle speed signal. The processor determines a simulated left end stop position of a rack based on the input signals, and a simulated right end stop position of a rack based on the input signals. The processor compares a rack position with the simulated left end stop position and the simulated right end stop position. The processor generates a feedback signal based on a determination that the rack position is not within a range bound by the left end stop position and the right end stop position.