Collaborative Steer-By-Wire Control for Smooth Driver Handover
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Solution Overview
Problem
Steer-by-wire (SBW) systems in vehicles lack mechanical connection between the steering wheel and steerable wheels, leading to altered feedback torque and driver discomfort, confusion, and inconsistent responses, especially in automated driving scenarios.
Innovation Solution
A collaborative steering system that includes sensors, a steering rack motor, and a steering emulator, with a controller executing programmatic control logic to adjust steering ratios, provide torque, and smooth transitions between automated and manual steering, enhancing driver comfort and connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If steer-by-wire system is implemented without mechanical connection, then automation capability is improved, but driver comfort and sense of connectedness deteriorate
Solution Approach 1:
A feedback torque mechanism is introduced as an intermediary between the steering wheel actuator and the road wheel actuator. This feedback torque, generated based on road wheel actuator position and velocity, creates a virtual mechanical connection that provides the driver with tactile feedback and sense of connectedness while maintaining the wireless steer-by-wire architecture.
Solution Approach 2:
The patent replaces the traditional mechanical connection between steering wheel and road wheels with an electronic control system that uses sensors, actuators, and control algorithms to simulate mechanical feedback. The feedback torque mechanism substitutes physical mechanical coupling with electronic feedback loops.
2Device complexity
If feedback torque is reduced or removed in SBW systems, then system complexity is reduced, but vehicle dynamics feedback is lost
Solution Approach 1:
The system implements a feedback control mechanism where the road wheel actuator's position and velocity are continuously measured and used to generate feedback torque on the steering wheel. This closed-loop feedback preserves vehicle dynamics information while using relatively simple sensor and actuator components.
3Ease of operation
If road wheel actuator response is made consistent with steering wheel movement, then driver comfort is improved, but control system complexity increases
Solution Approach 1:
The steering ratio is made dynamically adjustable rather than fixed. The system can switch between manual steering ratio and automated driving assistance system steering ratio based on operational mode. This dynamic adjustment allows consistent response characteristics across different operating conditions without requiring overly complex continuous control mechanisms.
Data Source
AI summary
A system for collaborative steering in steer-by-wire (SBW) vehicles includes sensors, a rack motor altering a position of the vehicle's steerable road wheels and an emulator altering a torque and position of a vehicle hand wheel. A collaborative steering system application (CSSA) obtains, static and dynamic information about the vehicle and the vehicle's environment, and generates a rack torque and/or angle command to the rack motor and an emulator torque and/or angle command to the emulator. The CSSA adjusts between ADAS and manual steering ratios and automatically transitions control between ADAS SBW control and manual control. The CSSA smooths transitions between ADAS SBW control and manual steering control and adjusts hand wheel stiffness by altering the emulator torque command, and causes the rack motor and emulator to operate according to a kinematic model while adapting road wheel response and vehicle operator steering feel based on scenarios and features currently enabled.