Working Machine Steering Ratio Control for Accurate Four-Wheel Steer
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Solution Overview
Problem
Existing four-wheel steer systems with secondary steering devices, such as joysticks or rollers, suffer from overly sensitive steering ratios in four-wheel steer mode, making control difficult due to the limited range of motion, which restricts their use in working machines.
Innovation Solution
A steering system that adjusts the steering ratio based on the selected mode (2WS or 4WS) and vehicle speed, using a controller to modify the hydraulic flow and actuator response, particularly in 4WS mode, to provide a reduced steering ratio when using secondary steering devices, ensuring better control and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If four-wheel steer mode is used with secondary steering devices (joystick, roller, lever), then steering control is provided, but the steering ratio becomes overly sensitive making control difficult
Solution Approach 1:
The steering ratio is made dynamic and adjustable based on the operating mode (2WS or 4WS) and vehicle speed. The controller modifies the hydraulic flow and actuator response in real-time, reducing the steering ratio in 4WS mode to provide better control and accuracy while maintaining ease of operation.
Solution Approach 2:
The system changes the steering ratio parameter based on the selected steering mode and vehicle speed conditions. By adjusting the hydraulic flow parameters and actuator response characteristics, the system optimizes the steering ratio for different operating conditions, preventing excessive sensitivity in 4WS mode.
2Measurement precision
If the steering ratio is reduced in four-wheel steer mode, then control accuracy is improved, but the steering response becomes slower
Solution Approach 1:
The steering system dynamically adjusts the steering ratio based on vehicle speed and operating mode. At lower speeds, the system provides a reduced steering ratio for improved accuracy, while at higher speeds, the steering ratio increases to maintain responsive steering control, thus balancing accuracy and response speed across different operating conditions.
Solution Approach 2:
The controller modifies hydraulic flow parameters and actuator response characteristics based on real-time vehicle speed and steering mode detection. This dynamic parameter adjustment allows the system to optimize both steering accuracy and response speed by adapting the steering ratio to current operating conditions rather than using a fixed ratio.
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
The system enhances control and accuracy in four-wheel steer mode by reducing the steering ratio, especially with secondary steering devices, allowing for improved maneuverability and safety in various working conditions.
Implementation Method 1
The prime mover drives the hydraulic pump, in order to provide hydraulic pressure for the working arm arrangement and, in some examples, to power one or more hydraulic motors located in the undercarriage
Implementation Method 2
a front steering actuator for adjusting the steering angle of each of the front pair of wheels to effect front wheel steering; and a rear steering actuator for adjusting the steering angle of each of the rear pair of wheels
Data Source
AI summary
A working machine including: a ground engaging structure having front steerable wheels and rear steerable wheels; a front steering actuator for adjusting the steering angle of each of the front wheels; a rear steering actuator for adjusting the steering angle of each of the rear wheels; an operator steering device configured to provide a steering demand; and, an operator steering mode selector configured to select either a two wheel steer mode or a four wheel steer mode; wherein the front and rear steering actuators are selectively operable in accordance with the steering demand and selected two wheel steer mode or four wheel steer mode, wherein a steering ratio, which is the ratio of steering demand to turning angle of the front wheels and/or rear wheels is different in the two wheel and four wheel steer modes.