Variable Torque Feedback Steering for Off-Road Machines
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Solution Overview
Problem
Off-road work machines face challenges with steering stability due to varying load conditions and operator preferences for steering sensitivity, leading to undesirable 'oversteer' and 'understeer' characteristics, and a lack of feedback control in existing systems.
Innovation Solution
An electrohydraulic steer-by-wire system with a controller, operator control, steering wheel position sensor, road wheel angle sensor, speed sensor, and feedback device, allowing operators to adjust sensitivity levels and receive feedback torque based on predicted lateral acceleration, using stored torque curves and on-center steering ratio curves to enhance steering control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the steering system uses a fixed steering ratio, then the system is simple to control, but it cannot adapt to varying load conditions and operator preferences
Solution Approach 1:
The patent implements a dynamic steering ratio that automatically adjusts based on operating conditions such as vehicle speed and load. The controller modifies the steering ratio in real-time to optimize steering characteristics, transitioning between understeer and oversteer modes as needed. This dynamic adjustment allows the system to adapt to varying conditions without requiring multiple physical steering mechanisms.
Solution Approach 2:
The system changes the steering ratio parameter dynamically based on detected operating conditions. By monitoring vehicle speed, lateral acceleration, and other parameters, the controller adjusts the steering ratio to provide appropriate steering sensitivity for each operating mode, thereby achieving adaptability through parameter modification rather than structural complexity.
2Force
If the steering system is heavily loaded, then the machine can handle heavy implements, but the steering becomes unstable with oversteer characteristics
Solution Approach 1:
The system uses feedback from sensors monitoring lateral acceleration, vehicle speed, and steering angle to detect oversteer conditions. When heavy loads are detected or oversteer characteristics are observed, the controller provides corrective feedback torque to the steering wheel, guiding the operator back to stable steering inputs. This feedback mechanism maintains steering stability even when the vehicle is heavily loaded.
Solution Approach 2:
The system anticipates oversteer conditions by monitoring load indicators and vehicle dynamics, then applies counteracting steering torque before the oversteer becomes severe. By detecting early signs of instability and providing preliminary corrective feedback, the system prevents full oversteer development, maintaining steering stability under heavy load conditions.
3Productivity
If the steering system is lightly loaded, then the machine operates efficiently, but the steering becomes overly sensitive with understeer characteristics
Solution Approach 1:
During light-load operations, the system monitors steering inputs and vehicle response to detect excessive sensitivity or understeer characteristics. The controller provides feedback torque to dampen overly sensitive steering responses, stabilizing the steering system during efficient light-load operation. This feedback ensures stable steering even when the vehicle is lightly loaded and operating at peak efficiency.
Data Source
AI summary
A method of controlling a work machine having at least one wheel includes providing a controller, an operator control, and a steering system including a steering wheel position sensor, a road wheel angle sensor, a speed sensor, and a feedback device. The method includes detecting a change in steering wheel position via the steering wheel position device and a wheel speed of the at least one wheel via the speed sensor. A predicted lateral acceleration is calculated by the controller as a function of wheel speed and a feedback torque is determined by the controller as a function of the predicted lateral acceleration. The feedback torque is determined from a plurality of feedback torque curves stored by the controller, where each of the plurality of feedback torque curves corresponds to a sensitivity level selectable from the operator control. The feedback torque is commanded to the feedback device.