Variable Steering Gain for Agricultural Machine Rear Wheels
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Solution Overview
Problem
Agricultural machines with dual-path hydrostatic systems face steering lag due to the mass of the machine, which affects the responsiveness of the front drive wheels, and conventional rear steering systems provide jerky steering responses when making small or large adjustments, compromising handling and controllability.
Innovation Solution
A hydraulic steering system with a secondary steering system that includes independent actuators for the rear caster wheels, controlled by a controller that outputs non-linear steering gain rates based on the steer command, allowing for gentle corrections and aggressive maneuvers, improving steering responsiveness and controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional rear steering system is used, then the machine can make direction changes, but the steering response becomes jerky when making small or large adjustments
Solution Approach 1:
The patent applies dynamics by making the steering gain variable rather than fixed. The controller dynamically adjusts the steering gain rate based on the current steering state and operator input, transitioning from a static system to a dynamic one that adapts to different operating conditions to eliminate jerky responses.
Solution Approach 2:
The patent changes the parameter of steering gain from a constant value to a variable rate that depends on steering state. By implementing non-linear steering gain rates that vary with steering angle and speed, the system smooths out jerky movements while maintaining responsiveness.
2Speed
If the machine mass is accounted for in the dual-path hydrostatic system, then speed changes can be managed, but steering lag occurs due to the mass of the machine
Solution Approach 1:
The system performs preliminary action by anticipating the steering requirements based on the operator's input and machine state. The controller proactively adjusts the steering system parameters before the full steering command is executed, reducing the perceived lag time.
Solution Approach 2:
The patent makes the steering system dynamic by continuously adjusting the steering gain rate based on real-time machine state and operator input. This dynamic adjustment allows the system to compensate for the machine's mass and reduce steering lag by optimizing the steering response at each moment.
3Adaptability or versatility
If a fixed steering gain rate is used in the secondary steering system, then the system is simple to control, but it cannot provide both gentle corrections and aggressive maneuvers
Solution Approach 1:
The patent implements dynamics by making the steering gain rate variable rather than fixed. The controller dynamically adjusts the gain based on the current steering state and operator input, allowing the same system to provide both gentle corrections and aggressive maneuvers without requiring multiple separate control systems.
Solution Approach 2:
The patent achieves universality by designing a single secondary steering system that can perform multiple functions - providing both gentle corrections for precise positioning and aggressive maneuvers for rapid direction changes. The variable steering gain rate enables one system to adapt to different operational requirements.
Data Source
AI summary
A steering system for controlling an agricultural machine having a pair of front wheels and a pair of rear wheels includes a controller, an operator steer input for communicating a steer command, a steer input sensor for detecting and outputting the steer command to the controller, a primary differential steering system for operably controlling the pair of front wheels, and a secondary steering system for operably controlling the pair of rear wheels. The secondary steering system includes a first actuator for controlling a first rear wheel and a second actuator for controlling a second rear wheel. The primary differential steering system is controlled based on the steer command. The controller outputs a control signal to operably actuate the first and second actuators at a non-linear steering gain rate as a function of the steer command.