Steered Axle Speed Limiting Based on Combined Slip Control
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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, limiting vehicle maneuverability and safety.
Innovation Solution
A system for determining a rotational speed limit for steered axles based on a slip diamond, which sets a combined slip limit for longitudinal and lateral slip, allowing for safe control of torque to saturate rotational speed when lateral slip is high, thereby increasing lateral traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple counter-steering of one axle relative to the other is used, then the steering system is easy to implement, but the vehicle becomes unstable at high speeds or on low friction surfaces
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the rotational speed limit of the steered axle based on multiple variables including lateral slip, longitudinal velocity, wheel radius, and combined slip limit. Instead of using a fixed simple counter-steering approach, the system continuously modifies control parameters (rotational speed limits) according to real-time vehicle state and environmental conditions, thereby achieving stability across varying speeds and friction surfaces while maintaining reasonable system complexity through algorithmic control
2Device complexity
If a rear steered axle is used only for translational lateral movement, then the steering strategy is simple, but the freedom of movement of the vehicle is limited
Solution Approach 1:
The patent implements dynamics by enabling the rear steered axle to perform multiple functions dynamically. The rear axle transitions between being used for simple translational lateral movement and active steering participation based on driving scenarios. The control system dynamically determines the appropriate role of the rear axle according to vehicle state and maneuver requirements, allowing the same hardware configuration to adapt to diverse driving conditions including high-speed cornering and low-friction surfaces
Data Source
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AI summary
A computer system and computer-implemented method for determining a rotational speed limit for a steered axle of a vehicle having two steered axles are disclosed. The computer system comprises processing circuitry configured to: acquire a combined slip limit for the steered axle based on a slip diamond; determine a longitudinal slip limit for the steered axle based on the combined slip limit and a current lateral slip of the steered axle; and determine a rotational speed limit for the steered axle based on the determined longitudinal slip limit, a radius of a wheel of the steered axle, and a current longitudinal velocity of the vehicle.