Hydraulic Steering System with Rear Wheel Alignment Correction
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Solution Overview
Problem
Road cleaning machines with front-wheel steering face challenges in maintaining cleaning equipment alignment during curved path operations, while four-wheel steering machines exhibit unusual behavior in transit mode, affecting maneuverability and safety around traffic.
Innovation Solution
A hydraulic steering system with a control unit that monitors and corrects the orientation of rear wheels to maintain alignment, switching between two-wheel and four-wheel steering modes based on speed and operator input, ensuring seamless transitions and minimizing operator-perceptible motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If four-wheel steering is used to improve cleaning path efficiency around curved perimeters, then the machine can better follow outer perimeters, but the machine exhibits unusual behavior in transit mode that affects maneuverability and safety
Solution Approach 1:
The system dynamically switches between two-wheel steering mode (for transit) and four-wheel steering mode (for work operations). The control unit automatically selects the appropriate steering mode based on machine speed and operational state, allowing the machine to exhibit normal vehicle behavior during transit while achieving improved cleaning path efficiency during work mode
Solution Approach 2:
The steering system changes the steering parameter by locking the rear wheels at zero steering angle during transit mode and allowing variable rear wheel steering angles during work mode. This parameter change enables the machine to maintain normal maneuverability characteristics in transit while achieving optimized cleaning paths during work operations
2Ease of operation
If rear wheels are locked at zero steering angle to maintain normal transit behavior, then maneuverability in traffic is improved, but alignment deviation occurs during work mode operations
Solution Approach 1:
The control unit continuously monitors the actual steering angle of the rear wheels and compares it with the desired zero-angle position. When deviation exceeds a threshold during transit mode, the control unit activates the alignment correction function to automatically adjust and realign the rear wheels, ensuring precise alignment while maintaining normal transit behavior
3Measurement precision
If alignment correction function is activated to correct rear wheel orientation, then alignment accuracy is improved, but operator-perceptible motion increases
Solution Approach 1:
The alignment correction function applies only when the deviation threshold is exceeded, rather than continuously correcting minor deviations. This partial action approach achieves sufficient alignment accuracy while minimizing unnecessary corrections that would cause perceptible motion and discomfort to the operator
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances cleaning path efficiency around curved perimeters in work mode while maintaining normal maneuverability in transit mode, reducing the turning circle by nearly 15% and improving alignment accuracy, thus ensuring safer operation and reduced operator input.
Implementation Method 1
a control unit is configured to monitor the orientation of the second set of wheels when locked at the steering angle of substantially zero degrees relative to the longitudinal axis of the machine and to correct deviation of the second set of wheels from said orientation
Data Source
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AI summary
The invention is directed to a steering system for a four-wheeled two-axle mobile machine (10), and in particular to a hydraulic steering system suitable for road surface cleaning machines. The invention comprises a hydraulic steering system for a machine having a longitudinal axis, comprising: a first steering axis having a first set of wheels (11); a second steering axis having a second set of wheels (12), the second set of wheels being operable to be locked at a steering angle of substantially zero degrees relative to the longitudinal axis of the machine; and a control unit configured to monitor the orientation of the second set of wheels when locked at the steering angle of substantially zero degrees relative to the longitudinal axis of the machine and to correct deviation of the second set of wheels from said orientation.