Steer-by-Wire Conjunction Reaction Force Control
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Solution Overview
Problem
In steer-by-wire vehicles, the driver may experience a feeling of strangeness due to unintended vehicle behavior during driving assist control, as the steering wheel does not reflect the intended vehicle turning direction.
Innovation Solution
A vehicle control system that applies a steering reaction force component to the steering wheel in conjunction with vehicle turning, using feedforward reaction force control to move the steering wheel in the same direction as the driving assist control without relying on the steering angle, thereby enhancing driver awareness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If driving assist control automatically turns the vehicle independently of driver steering operation, then automation of vehicle turning is improved, but driver awareness of vehicle turning direction deteriorates
Solution Approach 1:
The system implements feedback by detecting the steering wheel operation amount and using it as a basis for generating the steering reaction force. When the driver operates the steering wheel, the system detects this operation and applies an appropriate reaction force to provide tactile feedback, maintaining the driver's awareness of steering actions even during automated driving assist control.
Solution Approach 2:
The steering reaction force acts as an intermediary between the automated driving assist control system and the driver. Instead of directly connecting the automated turning command to the driver, the system uses the reaction force mechanism to mediate this interaction, providing tactile information about the vehicle's turning state to the driver through the steering wheel.
2Measurement precision
If steering reaction force is calculated based on feedback axial force from turning actuator, then accuracy of road surface reaction force representation is improved, but responsiveness to driving assist control deteriorates
Solution Approach 1:
The system performs preliminary action by calculating the feedforward axial force in advance based on the detected steering wheel operation amount, before the actual turning occurs. This pre-calculated force component is then combined with the feedback axial force, ensuring that the steering reaction force responds quickly to driving assist control while maintaining accuracy through the feedback component.
Solution Approach 2:
The system merges two different axial force components - the feedforward axial force (calculated in advance based on steering operation) and the feedback axial force (measured from the turning actuator). By combining these two components, the system achieves both responsiveness (from feedforward) and measurement precision (from feedback) in the steering reaction force calculation.
Data Source
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AI summary
A vehicle control system (10) controls a vehicle (1) of a steer-by-wire type. The vehicle control system (10) is configured to execute: driving assist control that assists driving of the vehicle (1); and conjunction reaction force control that applies a steering reaction force component to a steering wheel (3) in conjunction with turning of the vehicle (1) caused by the driving assist control. A driving assist direction (Da) is a direction of the turning of the vehicle (1) caused by the driving assist control. The conjunction reaction force control includes feedforward reaction force control that moves the steering wheel (3) in a same direction as the driving assist direction (Da) without depending on a steering angle (θs) of the steering wheel (3).