Steer-By-Wire Running Control for Low-Speed Turning Angle Lag
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Solution Overview
Problem
In vehicle running control systems with steer-by-wire steering apparatuses, the inability to achieve the target turning angle during stationary steering due to insufficient motor output leads to a turning angle difference that increases discomfort as vehicle speed rises, and existing solutions like booster circuits are costly.
Innovation Solution
A control device that executes a driving force limiting processing, reducing the target vehicle driving force when the turning angle difference exceeds a threshold at low speeds, using correction amounts adjusted by vehicle speed and turning speed coefficients to minimize yaw rate changes without requiring a booster circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a booster circuit is used to provide sufficient turning torque during stationary steering, then the turning angle difference is reduced, but the system cost increases
Solution Approach 1:
The patent replaces the electrical booster circuit with a control strategy that uses the existing mechanical components more effectively. The control device manages the turning motor output and vehicle drive unit coordination to achieve acceptable turning angle accuracy without adding expensive electrical boosting hardware.
Solution Approach 2:
The patent changes operational parameters (vehicle speed, driving force, turning angle) dynamically through control strategies. By adjusting these parameters during vehicle operation, the system achieves better turning angle control during stationary steering without requiring additional hardware.
2Speed
If the vehicle speed increases rapidly to eliminate turning angle difference, then the turning response is faster, but passenger comfort deteriorates due to large yaw rate changes
Solution Approach 1:
The patent implements dynamic control of vehicle speed and driving force based on real-time conditions. The control device continuously adjusts the vehicle drive unit output to balance turning response speed with passenger comfort, preventing abrupt speed changes that would cause large yaw rate variations.
Solution Approach 2:
The control device uses feedback from sensors monitoring turning angle difference, vehicle speed, and driving conditions to continuously adjust the vehicle drive unit output. This closed-loop control ensures that turning angle difference is eliminated at an appropriate rate that maintains passenger comfort.
Data Source
AI summary
A vehicle running control system includes: a steering apparatus that includes a turning device being mechanically separated from a steering wheel; a vehicle drive unit; and a control device. The control device is configured to execute: a turning processing that controls the turning device such that an actual turning angle of the wheel approaches a target turning angle; a vehicle driving processing that determines a target vehicle driving force according to a required vehicle driving force based on a vehicle driving request and that controls the vehicle drive unit so as to cause an actual vehicle driving force to the target vehicle driving force determined; and where a turning angle difference is greater than a turning angle threshold value in a low vehicle speed condition, a driving force limiting processing that limits the target vehicle driving force so as to become smaller than the required vehicle driving force.