Steering Reaction Force Control for Lane Keeping Assist
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Solution Overview
Problem
Conventional lane keeping assist devices with steer-by-wire systems fail to provide appropriate steering reaction forces at low speeds, leading to driver discomfort due to the disconnect between steering wheel input and turning wheel orientation.
Innovation Solution
A lane keeping assist device that controls steering reaction forces based on vehicle speed, using a combination of first and second reaction force command values to impart appropriate steering feedback, with a larger force when the vehicle is at low speeds and a reduced force at high speeds, ensuring alignment with the lane center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lane keeping control is carried out only through turning angle control in SBW system, then high-speed travel is comfortable, but low-speed travel causes driver discomfort due to disconnect between steering input and vehicle orientation
Solution Approach 1:
The system dynamically switches between two control modes based on vehicle speed: at high speeds, only the first turning angle (lane keeping) is applied, while at low speeds, both the first turning angle (lane keeping) and second turning angle (steering input correspondence) are combined. This dynamic adaptation resolves the contradiction by adjusting control behavior to match speed conditions.
Solution Approach 2:
The control parameters (turning angle composition) are changed based on vehicle speed threshold. Above the threshold, only lane keeping control is active; below the threshold, both lane keeping and steering correspondence controls are active. This parameter change enables the system to adapt to different speed conditions and eliminate driver discomfort.
2Device complexity
If steering reaction force is controlled based on lane keeping turning angle only, then system simplicity is maintained, but driver feedback becomes unrealistic at low speeds
Solution Approach 1:
The steering reaction force control is segmented into two independent components: first reaction force based on lane keeping turning angle, and second reaction force based on steering input amount. These segmented components are then combined based on speed conditions, allowing the system to maintain simplicity while improving feedback realism.
Solution Approach 2:
The system merges two separate reaction force calculations (lane keeping-based and steering input-based) into a unified control output. By combining these forces appropriately based on speed threshold, the system achieves realistic steering feedback without excessive complexity.
3Ease of operation
If mechanical connection between steering wheel and turning wheels is maintained, then natural steering feedback is provided, but steer-by-wire system advantages are lost
Solution Approach 1:
The patent replaces the mechanical connection between steering wheel and turning wheels with an electronic control system that calculates and applies appropriate reaction forces. By substituting mechanical coupling with electronic control, the system maintains SBW advantages while reproducing natural steering feedback through calculated reaction forces based on both lane keeping and steering input.
Data Source
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AI summary
The present invention prevents a vehicle in a low-speed region from deviating from a traveling lane and prevents the vehicle from wandering in the traveling direction. Specifically, the present invention is a lane keeping assist device that assists a vehicle, in which a steering wheel in the vehicle and a turning wheel for turning the vehicle are mechanically detached, to travel within traveling lanes, wherein the lane keeping assist device controls the turning angle of the turning wheel using a first turning angle calculated so as to cause the vehicle to travel in the traveling lane and a second turning angle corresponding to the steering amount of the steering wheel; detects the vehicle speed of the vehicle; calculates a first reaction force command value to the steering wheel corresponding to the first turning angle and a second reaction force command value to the steering wheel corresponding to the second turning angle; controls the steering reaction force to be imparted to the steering wheel to have a steering reaction force that corresponds only to the second reaction force command value when the vehicle speed is higher than a predetermined threshold value (predetermined vehicle speed), and controls the steering reaction force to be imparted to the steering wheel to have a steering reaction force that corresponds to the first reaction force command value and the second reaction force command value when the vehicle speed is at the predetermined threshold value, or less.