4WS Vehicle Heading Control via Dynamic Pivot Point
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Solution Overview
Problem
4WS vehicles face challenges in maintaining stability and control due to a shifting pivot point, which affects the tracking of control points, and there is a need to minimize crop damage by ensuring rear wheels follow the same tracks as front wheels.
Innovation Solution
A method to determine the dynamic pivot point and true heading of a 4WS vehicle using GNSS and IMU data, combined with a Kalman filter, to stabilize control points and enable rear wheels to follow front wheels' tracks, utilizing existing 2WS controllers with modified inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If 4WS vehicle uses dynamic front to rear wheel angle ratio for sharper turns and crab steering, then vehicle maneuverability is improved, but the pivot point becomes unstable and control point tracking deteriorates
Solution Approach 1:
The patent applies dynamics by making the control point adaptive rather than fixed. The control point dynamically adjusts its position based on the instantaneous pivot point location, which changes with front to rear wheel angle ratio. This allows the system to maintain stable control point tracking even as the vehicle transitions between different steering modes (crab steering, sharp turns, normal driving), resolving the contradiction between maneuverability and stability.
2Productivity
If rear wheels are steered independently from front wheels in 4WS mode, then vehicle can make sharper turns and translate smoothly, but control point tracking becomes unstable
Solution Approach 1:
The patent implements feedback by continuously calculating the instantaneous pivot point based on current front and rear wheel angles, then using this information to dynamically adjust the control point position. This closed-loop approach ensures that the control point remains stable and predictable regardless of the wheel angle configuration, maintaining reliable tracking while enabling high-productivity 4WS operations.
3Ease of manufacture
If existing 2WS controller systems are used for 4WS vehicle, then system compatibility is maintained, but control accuracy deteriorates due to shifting pivot point
Solution Approach 1:
The patent introduces an intermediary computational layer that sits between the existing 2WS controller and the 4WS vehicle dynamics. This intermediary dynamically calculates the instantaneous pivot point and adjusts the control point position accordingly, translating the simple 2WS control signals into accurate 4WS control without requiring hardware changes. This maintains ease of manufacture while improving control accuracy for 4WS operations.
Data Source
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AI summary
Disclosed are a method and apparatus for determining the heading of a 4WS vehicle. The 4WS vehicle's dynamic pivot point is calculated from the steering angles. A distance between the dynamic pivot point and a Global Navigation Satellite System (GNSS) antenna is determined. A time delay is determined in the form of the distance between the GNSS antenna and the pivot point divided by the current vehicle horizontal velocity. The time delay is multiplied by a vehicle yaw rate to obtain a result which is added to a GNSS antenna heading to give a true heading. A control point for the 4WS vehicle is selected to allow that control point to follow a desired trajectory.