Hydrostatic Transmission Pressure Compensation for Work Vehicle Speed Control
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Solution Overview
Problem
In work vehicles equipped with hydrostatic transmissions, the actual differential pressure in the hydraulic circuit may diverge from the target due to leakage, leading to inaccuracies in achieving desired vehicle speed and tractive force.
Innovation Solution
A controller system that includes pressure sensors, an accelerator operating sensor, and a compensation factor calculation to adjust the target displacement of the travel pump and travel motor based on the actual hydraulic pressure, ensuring accurate output even when differential pressure diverges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the displacement of the travel pump and travel motor is controlled to achieve desired vehicle speed and tractive force, then the output performance is improved, but the actual differential pressure diverges from target due to hydraulic fluid leakage
Solution Approach 1:
The controller continuously monitors the actual differential pressure through pressure sensors and compares it with the target differential pressure. Based on this feedback, the controller calculates a compensation factor and adjusts the displacement commands to the travel pump and travel motor, ensuring that the desired vehicle speed and tractive force are achieved despite hydraulic fluid leakage causing pressure deviations.
2Reliability
If hydraulic fluid leakage occurs in the hydraulic circuit, then the differential pressure control accuracy deteriorates, but the system can compensate by adjusting displacement commands
Solution Approach 1:
When hydraulic fluid leakage is detected through pressure deviation, the controller changes the operational parameters by calculating a compensation factor based on the ratio between target and actual differential pressure. This compensation factor is applied to adjust the displacement commands to the travel pump and travel motor, maintaining reliable output accuracy despite the energy loss from leakage.
3Measurement precision
If pressure sensors and compensation factor calculation are added to the control system, then the output accuracy is improved, but the device complexity increases
Solution Approach 1:
The controller integrates multiple functions into a single device: it serves as the control unit for displacement commands, the differential pressure calculation unit, the compensation factor calculation unit, and the adjustment mechanism. By making the controller multi-functional, the system achieves accurate differential pressure measurement and compensation without proportionally increasing device complexity.
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
This solution allows for precise control of vehicle speed and tractive force, ensuring accurate desired output by compensating for pressure discrepancies caused by leakage, thereby enhancing operational efficiency.
Implementation Method 1
a pressure sensor that outputs a signal indicating the hydraulic pressure in at least one of the first circuit and the second circuit
Data Source
AI summary
A controller determines a compensation factor from an operating amount of an accelerator operating member and a hydraulic pressure of at least one of a first circuit and a second circuit. The controller determines a target vehicle speed from the operating amount of the accelerator operating member. The controller determines at least one of a target displacement of a travel pump and a target displacement of a travel motor from the target vehicle speed and the compensation factor.