Threshold-Based Rear-Wheel Steering for Stability and Maneuverability
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Solution Overview
Problem
Existing four-wheel steering systems for vehicles do not optimally manage rear wheel steering angles across various driving conditions, leading to suboptimal performance in stability, maneuverability, and fuel efficiency.
Innovation Solution
A method for controlling rear steering wheels using independent actuators, an electronic control unit, and a threshold-based steering angle adjustment strategy that adjusts rear wheel steering angles differently based on driving conditions, including in-phase and counter-phase steering during curves and toe adjustments on straight roads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rear wheels are steered in-phase at high speeds, then vehicle stability is improved, but steering radius increases and maneuverability decreases
Solution Approach 1:
The patent applies dynamics by making the rear wheel steering angle variable rather than fixed. The control unit dynamically adjusts the steering angle based on real-time detection of driving conditions (curve detection unit), transitioning between in-phase steering for stability at high speeds and counter-phase steering for maneuverability at low speeds, thus resolving the contradiction between stability and maneuverability
Solution Approach 2:
The patent changes the parameter of steering angle magnitude and phase relationship. By detecting curve parameters and vehicle speed, the system varies the rear wheel steering angle parameter - using smaller in-phase angles for stability during high-speed curving and larger counter-phase angles for tight turns at low speeds, thereby optimizing both stability and maneuverability across different operating conditions
2Ease of operation
If rear wheels are steered counter-phase at low speeds, then steering radius is reduced and maneuverability is improved, but vehicle stability decreases
Solution Approach 1:
The system dynamically switches steering modes based on detected conditions. The control unit monitors vehicle speed and curve detection results to determine when counter-phase steering is appropriate (low-speed maneuvers) versus when in-phase steering is needed (high-speed curving), thus providing maneuverability when needed while maintaining stability during normal operation
Solution Approach 2:
The patent implements feedback through the curve detection unit and control unit that continuously monitor vehicle state. The system uses feedback from speed sensors and curve detection to automatically adjust rear wheel steering angles, switching between counter-phase and in-phase modes based on real-time conditions, thereby optimizing maneuverability without compromising stability
3Device complexity
If fixed steering angles are used for rear wheels, then system complexity is reduced, but adaptability to different driving conditions deteriorates
Solution Approach 1:
The patent replaces complex mechanical linkage systems with an electronic control system. Instead of using mechanical linkages to automatically impose fixed steering angles, the system uses electronic sensors, control units, and actuators to dynamically adjust rear wheel angles based on detected driving conditions, achieving adaptability while keeping the mechanical structure relatively simple
Solution Approach 2:
The control unit serves multiple functions: it processes sensor data, detects curves, determines appropriate steering angles, and controls the actuators. This multi-functional electronic system replaces what would require separate dedicated mechanisms for each function, reducing overall system complexity while maintaining high adaptability to various driving conditions
Data Source
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AI summary
A method to control a road vehicle (1) with rear steering wheels (3) and having, while driving along a curve, the steps of: determining a desired steering angle (αTGT) for the rear wheels (3); comparing the desired steering angle (αTGT) with a threshold value (TH); applying, while driving along a curve and if the desired steering angle (αTGT) is greater than the threshold value (TH), to both rear wheels (3) a same actual steering angle (α) that is equal to the desired steering angle (αTGT); and applying, while driving along a curve and if the desired steering angle (αTGT) is smaller than the threshold value (TH), to a rear wheel (3) on the outside of the curve an actual steering angle (α) greater than the desired steering angle (αTGT) and applying to a rear wheel on the inside of the curve a zero actual steering angle (α).