Towed Implement Guidance Using Offset Path Planning
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Solution Overview
Problem
Existing agricultural autopilot systems face challenges in efficiently guiding towed or pushed implements to and from desired paths, often resulting in slow alignment, potential jack-knifing, and violation of constraints such as maximum allowed angle between the vehicle and implement.
Innovation Solution
Implement guidance systems that utilize feedback and path-planning autopilots to estimate and control offsets, guiding vehicles toward an offset path and back to the desired path, while adhering to constraints like maximum vehicle curvature and implement angle, using techniques like tractrix paths for pushed implements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If feedback gain is increased to provoke overshoot for faster implement alignment, then implement alignment speed is improved, but tractor path stability deteriorates and jack-knifing risk increases
Solution Approach 1:
The system pre-calculates an optimal offset distance from the desired path before the tractor reaches it. This offset is determined based on implement length, hitch geometry, and vehicle dynamics parameters. By preparing this offset path in advance, the system enables controlled overshoot that brings the implement online faster while maintaining tractor stability through predetermined geometric relationships rather than reactive feedback adjustments.
Solution Approach 2:
The offset path serves as an intermediary between the desired path and the tractor-implement system. Instead of directly guiding the tractor onto the desired path (which causes slow implement alignment) or using aggressive feedback (which causes instability), the system introduces an intermediate offset path that mediates the transition. This intermediary path allows the implement to naturally swing onto the desired path while the tractor follows a stable, pre-calculated trajectory.
2Measurement precision
If traditional feedback autopilot is used to guide tractor to desired path, then tractor path accuracy is improved, but implement alignment efficiency deteriorates
Solution Approach 1:
The system pre-calculates an optimal offset distance from the desired path before the tractor reaches it. This offset is determined based on implement length, hitch geometry, and vehicle dynamics parameters. By preparing this offset path in advance, the system enables controlled overshoot that brings the implement online faster while maintaining tractor stability through predetermined geometric relationships rather than reactive feedback adjustments.
Solution Approach 2:
The system transitions from one-dimensional path following (staying on the desired path) to two-dimensional path planning (using an offset path perpendicular to the desired path). By adding the perpendicular dimension of offset distance, the system creates a new control space where both tractor accuracy and implement efficiency are optimized simultaneously through geometric relationships rather than conflicting feedback adjustments.
3Speed
If aggressive feedback tuning is used to speed up implement alignment, then implement alignment speed is improved, but system reliability deteriorates due to jack-knifing and draw bar stress
Solution Approach 1:
The system applies preliminary anti-action by pre-calculating and limiting the maximum offset distance based on vehicle-implement geometry and stability criteria. Before the tractor-implement system encounters potential jack-knifing conditions, the offset path is designed to prevent excessive hitch angles. This proactive geometric constraint prevents the harmful condition (jack-knifing) from occurring in the first place, rather than reacting to it after it develops.
Solution Approach 2:
The system changes the control parameter from feedback gain (which causes instability when increased) to offset distance (which can be optimized geometrically). By transforming the control approach from adjusting feedback intensity to selecting an optimal geometric offset, the system achieves faster implement alignment through parameter optimization rather than aggressive feedback, thereby maintaining system reliability while improving alignment speed.
Data Source
AI summary
Efficient towed implement guidance to a desired path is achieved by guiding a towing vehicle toward a path on the opposite side of a desired path, then guiding the vehicle back to the desired path. Efficient forward implement guidance to a desired path is achieved by guiding a pushing vehicle along a tractrix. A vehicle leaves a straight line along a tractrix to keep a rear implement on the line as long as possible.