Two-Axle Steering Control Using a Bicycle Model for Vehicle Stability
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Solution Overview
Problem
Current multi-axle steering systems in vehicles, particularly in construction equipment, lead to instability at high speeds or on low friction surfaces due to rudimentary steering coordination, limiting vehicle freedom of movement and safety.
Innovation Solution
A system that determines steering angles for vehicles with two steered axles using a bicycle model, based on desired yaw rate and lateral velocity, allowing for decoupled yaw rate and lateral movement, and utilizing feedforward and path-following controllers for precise angle determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If simple counter-steering of one axle relative to the other is used, then the steering system is easy to implement, but vehicle stability deteriorates at high speeds or on low friction surfaces
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting steering angles based on vehicle speed, yaw rate, and lateral acceleration. The control system modifies steering parameters (front and rear axle steering angles) according to operating conditions, transitioning from simple proportional counter-steering to a comprehensive multi-parameter control strategy that maintains stability across diverse driving scenarios.
Solution Approach 2:
The patent implements dynamics by making the steering system adaptive and responsive to real-time vehicle states. The rear steered axle is actively controlled based on measured vehicle parameters (yaw rate, lateral acceleration, longitudinal velocity) rather than being fixed to a simple proportional relationship, enabling the system to dynamically adjust to high-speed cornering and low-friction conditions.
2Ease of operation
If rear steered axle is used only for translational lateral movement, then the steering system is simple to control, but vehicle freedom of movement is limited
Solution Approach 1:
The patent applies universality by enabling the rear steered axle to perform multiple functions: it provides both translational lateral movement and active steering control. The rear axle participates in comprehensive steering strategy alongside the front axle, allowing the vehicle to execute diverse maneuvers (lane changes, high-speed cornering, tight turns) that a single-function rear axle cannot achieve.
Solution Approach 2:
The patent adds another dimension to steering control by independently controlling both front and rear axle steering angles rather than using a single degree of freedom. This dual-axle independent control creates an expanded control space that enables more versatile vehicle motion patterns while maintaining manageable system control through coordinated angle determination.
3Adaptability or versatility
If comprehensive steering strategy with decoupled yaw rate and lateral movement is used, then vehicle freedom of movement increases, but system complexity increases
Solution Approach 1:
The patent applies segmentation by separating the determination of yaw rate and lateral velocity into distinct computational steps, then using these separate parameters to independently influence front and rear steering angles. The control system processes different vehicle motion parameters (yaw angle, lateral distance, longitudinal velocity) separately and combines them through the bicycle model to achieve comprehensive steering control without overwhelming system complexity.
Solution Approach 2:
The patent uses the bicycle model as an intermediary that translates desired vehicle motion parameters (yaw rate, lateral velocity) into specific steering angles for the front and rear axles. This mathematical model acts as a mediator between the high-level motion objectives and the low-level actuator commands, managing system complexity by providing a structured transformation layer.
4Use of energy by moving object
If simple proportional counter-steering is used, then computational resources required are minimal, but control precision for autonomous vehicles deteriorates
Solution Approach 1:
The patent implements feedback by continuously measuring actual vehicle states (yaw rate, lateral acceleration, longitudinal velocity) and using these measurements to determine appropriate steering angles. The control system compares desired motion parameters with actual vehicle response and adjusts steering commands accordingly, providing precise control for autonomous operation while using computational resources efficiently through model-based calculations.
Data Source
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AI summary
A computer system and computer-implemented method for determining a steering angle for a steered axle of a vehicle having two steered axles are disclosed. The computer system comprises processing circuitry configured to: acquire a desired yaw angle of the vehicle at a second location; determine a desired yaw rate for the vehicle based on the desired yaw angle and a time for the vehicle to travel from a first location to the second location; acquire a lateral distance between the first location and the second location; determine a desired lateral velocity for the vehicle based on the lateral distance and the time for the vehicle to travel from the first location to the second location; and determine a steering angle for a steered axle of the vehicle using a bicycle model and based on the determined yaw rate and the determined lateral velocity.