Variable Wheel Speed Turn Control for GPS-Limited Agricultural Vehicles
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Solution Overview
Problem
Agricultural vehicles, such as windrowers, face inaccuracies in GPS positioning when making small movements, leading to difficulties in controlling steering, especially during differential turns, where opposite steerable wheels rotate at different speeds, and in navigating within boundary regions like headlands without damaging standing crops.
Innovation Solution
A controller system that determines a vehicle's position by monitoring the rotation speeds of opposite steerable wheels, allowing for accurate differential turning and navigation within defined boundaries by outputting specific rotation speed signals to the drivers and determining the vehicle's position based on these speeds, thereby eliminating reliance on GPS positioning for accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS positioning is used to control vehicle movement, then the system is simple to implement, but the positioning accuracy deteriorates when the vehicle moves only a small distance
Solution Approach 1:
The positioning function is segmented into two parts: GPS provides coarse positioning for general location, while wheel speed sensors provide precise relative position measurement for small movements. This segmentation allows each subsystem to operate in its optimal range, resolving the contradiction between simplicity and accuracy.
Solution Approach 2:
Wheel speed sensors act as an intermediary measurement device that bridges the gap between GPS updates. By measuring individual wheel rotations, the system can calculate precise vehicle displacement and orientation changes even when GPS cannot detect movement, thereby improving positioning accuracy without requiring more complex GPS hardware.
2Object-affected harmful factors
If opposite steerable wheels rotate at different speeds for differential turning, then the vehicle can navigate tight boundaries without damaging crops, but the control complexity increases
Solution Approach 1:
The system dynamically changes the rotation speed parameter of opposite wheels based on the required turn radius and boundary constraints. By independently controlling wheel speeds as variable parameters, the vehicle can achieve differential turning with precise control over the turn path, allowing navigation within tight boundaries without damaging crops.
Solution Approach 2:
The controller continuously monitors wheel speed sensor data and adjusts the rotation speeds of opposite wheels in real-time based on feedback about actual vehicle position and orientation. This closed-loop control enables precise differential turning while maintaining simplicity through automated feedback-based adjustment rather than complex manual control.
3Measurement precision
If GPS is relied upon for autonomous steering control, then the system is easy to operate, but the control accuracy deteriorates during small movements and turns
Solution Approach 1:
The system merges GPS positioning with wheel speed sensor measurement to create a hybrid positioning system. GPS provides absolute position reference while wheel speed sensors provide precise relative movement data, particularly during turns and small displacements. This combination maintains ease of operation through automated integration while dramatically improving control accuracy.
Solution Approach 2:
The system performs preliminary measurement of individual wheel rotations and speeds before calculating vehicle position and orientation. By capturing wheel speed data during the turning maneuver itself, the system can accurately determine vehicle displacement and heading change even when GPS cannot detect the movement, thereby improving control accuracy without requiring manual intervention.
Data Source
AI summary
A steering system includes a controller. The controller is configured to: enter a turn mode; determine respective, different rotation speeds of steerable wheels to turn the vehicle and reach a defined second position from a first position; output respective rotation speed signals to drivers to rotate the respective wheels at the determined respective rotation speeds in the turn mode; and determine the vehicle has reached the defined second position based at least partially on the rotation speeds and responsively exit the turn mode.