Agricultural Steering Control with Variable Rear Gain Profiles
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Solution Overview
Problem
Agricultural machines, such as self-propelled windrowers, face challenges in steering responsiveness due to steering lag at the front drive wheels and inadequate rear steering assistance, especially when transitioning between field and transport modes, leading to unsatisfactory steering performance.
Innovation Solution
A steering control system that differentiates between front differential motor displacements to change handling characteristics between field and transport modes, providing distinct steering gain rates for a given vehicle parameter and motor displacement, and includes a rear steering system with variable gain profiles to enhance steering responsiveness and stability across operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a primary differential steering system is used to control front drive wheels, then steering capability is provided, but steering lag occurs and responsiveness is insufficient
Solution Approach 1:
The steering system is segmented into a primary differential steering system for front wheels and a secondary rear steering system with independent actuators. This segmentation allows each system to operate independently, with the rear system compensating for the lag inherent in the primary front-wheel steering mechanism, thereby improving overall steering responsiveness.
Solution Approach 2:
The secondary rear steering system acts as an intermediary that enhances the primary steering system's performance. By adding rear wheel steering capability, the system reduces steering lag and improves responsiveness without replacing the entire primary steering mechanism.
2Ease of operation
If rear steering system is added to improve steerability, then steering performance is enhanced, but system complexity increases
Solution Approach 1:
The secondary rear steering system with actuators serves multiple functions: it provides steering assistance during direction changes, improves straight-line holding capability, and can be independently controlled based on operating conditions. This multi-functionality justifies the added complexity by delivering comprehensive steering performance improvements.
Solution Approach 2:
The rear steering system incorporates variable displacement actuators that can dynamically adjust their operation based on machine speed and operating mode (field vs. transport). This dynamic adaptability optimizes steering performance across different conditions while managing system complexity through intelligent control rather than mechanical complexity.
3Adaptability or versatility
If variable displacement motors are used for front wheels, then speed and torque control is improved, but steering gain matching becomes complex
Solution Approach 1:
The system changes the displacement parameter of the variable displacement motors based on operating mode (field or transport). The controller receives motor displacement inputs and uses this information to select appropriate steering gain profiles, thereby adapting steering characteristics to match the current operating conditions without requiring complex mechanical adjustments.
Solution Approach 2:
The controller continuously monitors motor displacement status and uses this feedback to determine which steering gain profile to apply. This closed-loop feedback mechanism ensures that steering gains are properly matched to the current operating mode, managing control complexity through intelligent algorithms rather than mechanical complexity.
4Reliability
If distinct steering gain profiles are implemented for different motor displacements, then steering performance across modes is improved, but control complexity increases
Solution Approach 1:
The controller changes steering gain parameters based on motor displacement status. By implementing distinct steering gain profiles for different motor displacement ranges (first and second operating modes), the system ensures consistent and optimized steering performance across all operating conditions while managing control logic complexity through programmed parameter selection.
Data Source
AI summary
A steering system for controlling an agricultural machine having a pair of front and rear wheels includes a controller and a steer input sensor for detecting a change in an operator steer input corresponding to a steer command. The system includes a displacement input for communicating a motor displacement associated with an operating mode. A primary differential steering system includes a drive motor for operably controlling the pair of front wheels and a secondary steering system controls the pair of rear wheels. The controller determines if the motor displacement is being controlled according to a first motor displacement or a second motor displacement, and outputs a control signal to actuate first and second actuators as a function of the steer command. The control signal includes a rear steering gain that is a function of machine speed and either the first motor displacement or the second motor displacement.