Four-Wheel Steering In-Phase Control for Rear Corner Clearance
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Solution Overview
Problem
Conventional four-wheel steering systems fail to prevent the rear part of a vehicle from contacting obstacles during low-speed turns, as they only restrain further outward movement after contact and require additional sensors for detection.
Innovation Solution
A four-wheel steering system that switches from antiphase to in-phase control based on a driver-initiated trigger operation via the steering wheel, allowing the rear wheels to steer in the same direction as the front wheels, thereby preventing contact with obstacles without the need for sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If antiphase control is used when vehicle speed is equal to or lower than a vehicle speed threshold, then the overall turning radius of the vehicle is smaller, but the rear part of the vehicle moves more outward of the turn in the early stage of the turn
Solution Approach 1:
The patent applies dynamics by making the rear wheel steering mode switchable between antiphase and in-phase control based on driving conditions. The control device dynamically adjusts the rear wheel steering direction according to vehicle speed and driver input, allowing the system to adapt between small turning radius (antiphase) and preventing rear outward movement (in-phase) as needed.
Solution Approach 2:
The patent changes the steering control parameter from fixed antiphase control to a switchable parameter that can be set to either antiphase or in-phase mode. This parameter change is triggered by vehicle speed threshold and driver's trigger operation, allowing flexible adjustment of rear wheel steering behavior to prevent harmful effects while maintaining beneficial ones.
2Reliability
If touch sensors are mounted on outer side surfaces of the rear part of the vehicle to detect contact, then contact detection is enabled, but the configuration of the vehicle becomes more complex
Solution Approach 1:
The patent applies self-service by using the existing steering wheel as both a control interface and a trigger mechanism. The driver's natural steering input serves dual purposes: controlling vehicle direction and triggering the in-phase control mode when needed, eliminating the need for separate sensors or detection systems while maintaining safety functionality.
Solution Approach 2:
The patent makes the steering wheel multi-functional by using it not only for conventional steering control but also as a trigger operation device that switches the rear wheel steering mode. This universal use of the steering wheel eliminates the need for additional sensors or detection devices, simplifying the overall vehicle configuration while maintaining contact prevention capability.
3Length of moving object
If the rear wheels are steered in the opposite direction to that in which the front wheels are steered, then the turning radius is reduced, but the corner of the rear end of the vehicle may contact the obstacle
Solution Approach 1:
The patent applies dynamics by making the rear wheel steering direction switchable between antiphase (opposite direction) and in-phase (same direction) modes. The control device dynamically adjusts the rear wheel steering based on vehicle speed and driver input, allowing the system to use antiphase control for tight turns when safe, and switch to in-phase control when the driver detects obstacle proximity, preventing rear end corner contact.
Solution Approach 2:
The patent changes the steering control parameter from fixed antiphase to a switchable parameter that can be set to either antiphase or in-phase mode based on driving conditions. This parameter change is triggered by vehicle speed threshold and driver's trigger operation on the steering wheel, allowing flexible adjustment to prevent harmful effects while maintaining beneficial turning performance.
Data Source
AI summary
The four-wheel steering system includes a front-wheel steering system that steers front wheels of a vehicle and a rear-wheel steering system that steers rear wheels of the vehicle in accordance with a steering angle that is a rotation angle of a steering wheel. The rear-wheel steering system includes a second ECU that, when the vehicle speed is equal to or lower than a vehicle speed threshold, performs antiphase control in which the rear wheels are steered in the opposite direction to that in which the front wheels are steered. When the vehicle speed is equal to or lower than the vehicle speed threshold, the second ECU performs in-phase control in which the rear wheels are steered in the same direction as that in which the front wheels are steered, in response to a specific trigger operation that is performed via the steering wheel.