Steer-by-Wire Blending Function for Smooth Mode Transitions
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Solution Overview
Problem
Steer-by-wire systems in vehicles face challenges in seamlessly transitioning between manual and automated control modes, particularly in ensuring smooth operation and safety during state changes, due to the lack of effective methods for blending steering inputs and managing feedback torques across multiple independent steering actuators.
Innovation Solution
The implementation of a method that operates the steering system in manual steer-by-wire control, determines transitions to automated steer-by-wire control based on specific conditions, and uses blending functions to combine manual and automated steering angles, while applying feedback torques to the steering wheel using feedback models and actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If steer-by-wire system transitions between manual and automated control modes, then control flexibility and automation capability are improved, but transition smoothness and operational safety deteriorate due to abrupt steering input changes
Solution Approach 1:
The system dynamically adjusts the blending ratio between manual and automated steering inputs based on transition phase, vehicle speed, and steering angle rate. During mode transitions, the controller progressively shifts weight from manual to automated inputs rather than abrupt switching, creating smooth dynamic adaptation that maintains operational comfort while enabling control flexibility
Solution Approach 2:
The controller modifies steering input parameters by blending manual steering wheel inputs with automated actuator commands using variable weighting factors. The blending ratio is adjusted as a controllable parameter during transitions, allowing gradual shift from manual-dominant to automated-dominant control, thereby maintaining smooth operation while enabling mode flexibility
2Measurement precision
If multiple independent steering actuators are used, then steering precision and control accuracy are improved, but feedback torque management complexity increases
Solution Approach 1:
The system merges feedback from multiple independent steering actuators and road feel models into a unified feedback torque signal applied to the steering wheel. The controller integrates individual actuator position feedback, road interaction models, and driver intent estimation into a single coherent feedback loop, reducing management complexity while maintaining high steering precision through coordinated multi-actuator control
3Ease of operation
If blending functions are used to combine manual and automated steering angles, then transition smoothness is improved, but control system complexity increases
Solution Approach 1:
The blending function uses feedback from actual steering wheel position, actuator positions, and driver torque inputs to dynamically adjust the mixing ratio between manual and automated commands. This closed-loop feedback mechanism enables smooth transitions while the controller adapts blending weights based on real-time system state, managing complexity through intelligent adaptation rather than fixed complex algorithms
Data Source
AI summary
A steering system includes an actuator, a steering wheel that generates inputs for the actuator in a manual steer-by-wire control state, and a controller that determines operating conditions for the actuator, the steering wheel, or both. The controller determines blended steering angles based on manual steering angles of the steering wheel and automatic steering angles associated with an automated steer-by-wire control state. The controller transitions operation of the steering system from the manual steer-by-wire control state to the automated steer-by-wire control state when all operating conditions are satisfied and uses a blending function that applies weighting values to the manual steering angles and the automated steering angles to determine the blended steering angles. The controller controls the actuator using the blended steering angles.