Steerable Caster Control for Stationary Turn Stability
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Solution Overview
Problem
Agricultural vehicles, such as harvesters, face challenges when attempting to steer stationary turns due to the risk of front wheels spinning or rear wheels skidding, which can damage rear axle components, as existing methods rely on passive castering that does not effectively manage torque distribution during turns.
Innovation Solution
A method and control system that senses steering commands, determines turn direction and magnitude, and adjusts the steerable caster and wheels to rotate in a direction consistent with the turn, applying proportional torque to avoid component damage by ensuring the rear wheels rotate about their vertical axes, thereby stabilizing the vehicle during stationary turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the vehicle uses passive castering for stationary turns, then the vehicle can achieve zero radius turns and enhanced mobility, but the rear wheels may skid sideways or front wheels may spin, resulting in damaged rear axle components
Solution Approach 1:
The patent replaces the passive mechanical castering system with an active control system that uses sensors to detect steering commands and controllers to coordinate wheel rotations. This substitution allows the system to manage torque distribution electronically rather than relying solely on passive mechanical following, preventing wheel spinning and skidding that damage rear axle components.
Solution Approach 2:
The patent implements feedback control by using sensors to detect steering commands and providing this information to controllers that adjust wheel rotations in real-time. This closed-loop feedback system ensures the rear wheels rotate appropriately during stationary turns, preventing harmful skidding and spinning motions while maintaining the desired maneuverability.
2Adaptability or versatility
If the vehicle rotates front wheels in opposite directions while passively following with rear casters, then the vehicle can execute stationary turns, but torque distribution is not effectively managed causing component stress
Solution Approach 1:
The patent transforms the static passive castering system into a dynamic active system where wheel rotations are continuously adjusted based on real-time sensor feedback. This dynamic control allows the system to adapt torque distribution during stationary turns, ensuring rear wheels rotate in coordination with front wheels and preventing excessive stress on rear axle components.
Solution Approach 2:
The patent introduces controllers as intermediary devices between the steering input and the wheel rotation mechanism. These controllers act as mediators that process steering commands and coordinate the rotation of all wheels, including the rear casters, to ensure proper torque distribution and prevent component stress during stationary turns.
3Device complexity
If the vehicle employs traditional castering without active control, then the system remains simple in structure, but the rear wheels cannot rotate about their vertical axes properly during turns
Solution Approach 1:
The patent makes the steering system universal by enabling it to perform multiple functions: traditional passive castering for normal operation and active coordinated control for stationary turns. The same steering system can adapt to different operating modes, providing both simplicity for straightforward maneuvers and precise control for complex stationary turns without requiring separate dedicated systems.
Data Source
AI summary
For a vehicle having left and right powered front wheels and a rear axle having left and right casters, with at least one of the casters being steerable, the steering angle of the steerable caster is controlled when the vehicle is stationary and executing a direction orientation maneuver prior to transitioning to a turn. The rotations of the steerable caster and at least one of the left and right wheels may be autonomously adjusted using a controller. The controller rotates the steerable caster about a caster axis in a direction consistent with the direction of the turn through a steering angle proportion to the magnitude of the turn, and rotates at least one of the left and right wheels to turn the vehicle in a direction consistent with the direction of the turn and in proportion to the magnitude of the turn.