Rear-Wheel Steering Backup Using Front-Wheel Delta Torque
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Solution Overview
Problem
Existing steering systems fail to optimally utilize engine, brakes, and all-wheel steering to maintain vehicle functionality and cornering behavior in the event of a front-wheel steering actuator failure, with a focus on restoring drivability with minimal energy expenditure.
Innovation Solution
The steering system maximizes the rear steering angle and defines a delta torque for the front wheels to achieve the required trajectory, ensuring optimal use of engine, brakes, and all-wheel steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steer-by-wire device fails, then the vehicle loses normal steering control, but the vehicle must maintain drivability and cornering behavior
Solution Approach 1:
The patent converts the harmful effect of steer-by-wire failure into a beneficial emergency steering mode. When the steer-by-wire device fails, the system automatically activates a backup steering mode that uses the rear-wheel steering device to provide steering control, thereby maintaining vehicle drivability and cornering behavior despite the failure of the primary steering system.
Solution Approach 2:
The patent changes the steering control parameters from normal steer-by-wire operation to emergency rear-wheel steering operation. The control device adjusts the steering angle, steering speed, and torque distribution parameters to accommodate the transition from front-wheel steer-by-wire to rear-wheel emergency steering, ensuring the vehicle can still be controlled effectively.
2Reliability
If the rear steering angle is maximized to restore drivability, then vehicle functionality is improved, but energy expenditure increases
Solution Approach 1:
The patent implements dynamic adjustment of the rear steering angle based on real-time vehicle operating conditions. The control device continuously monitors vehicle speed, steering demand, and system state to optimize the rear steering angle, maximizing drivability restoration while minimizing unnecessary energy consumption from excessive steering actuation.
Solution Approach 2:
The patent dynamically changes the rear steering angle parameter according to vehicle operating conditions. At lower speeds where maximum steering angle is needed for drivability, the system activates full rear-wheel steering capability. At higher speeds, the system reduces the rear steering angle to minimize energy expenditure while maintaining adequate control authority.
3Reliability
If delta torque is defined for front wheels to achieve required trajectory, then cornering behavior is maintained, but system complexity increases
Solution Approach 1:
The patent makes the control device multi-functional by enabling it to perform both normal steer-by-wire control and emergency rear-wheel steering control with delta torque adjustment. The same control device that manages the steer-by-wire system also takes over for emergency steering, eliminating the need for a completely separate emergency control system and reducing overall system complexity.
Solution Approach 2:
The control device acts as an intermediary that coordinates between the failed steer-by-wire system, the rear-wheel steering device, and the braking system. It calculates the required delta torque for the front wheels and coordinates the action of rear-wheel steering with differential braking to achieve the desired trajectory, simplifying the control architecture by using a single coordinating controller.
4Reliability
If all-wheel steering is utilized to maintain vehicle functionality, then steering performance is improved, but energy consumption increases
Solution Approach 1:
The patent implements dynamic activation of all-wheel steering based on failure detection and operating conditions. The system transitions from normal front-wheel steer-by-wire to emergency rear-wheel steering with delta torque only when failure is detected, and further activates differential braking only when needed to achieve the required trajectory, thereby maintaining steering performance while minimizing energy consumption from continuous all-wheel steering actuation.
Data Source
Figure 1~2
AI summary
The present invention relates to a steering device for a vehicle, comprising a steer-by-wire device (1) for the front wheels (7) of the vehicle, a rear-wheel steering device (2) capable of assuming a rear steering angle (δr), an individual wheel brake device (3), a single motor (4) on the front axle with a free differential, and a control device (5), characterized in that the steering device is configured to maximize the rear steering angle (δr) in order to drive with a maximum rear road wheel angle, and to define a delta torque for the front wheels (7) in order to achieve the required trajectory. The invention further relates to a vehicle with the steering device according to the invention, and to a method for controlling a steering device or a vehicle.