Hydrostatic Transmission Pump Displacement Control for Vehicle Braking
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Solution Overview
Problem
Current hydrostatic transmission systems in work vehicles, such as wheel loaders, face challenges in improving braking performance, which is essential for efficient operation and safety, particularly under varying load conditions and terrain.
Innovation Solution
A control method and apparatus that determines dynamic quantities such as vehicle mass, speed, and slope to adjust the displacement of the hydrostatic transmission's pump, optimizing braking by decreasing displacement with increased momentum and adjusting for slope and deceleration requests, using a mapping function to emit appropriate pump commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the displacement of the pump is reduced to brake the vehicle, then the vehicle speed is reduced, but the braking performance is insufficient under varying load conditions and terrain
Solution Approach 1:
The pump displacement is dynamically adjusted based on real-time vehicle conditions including momentum, slope, and deceleration requests. The control unit continuously modifies the pump displacement command value to optimize braking performance across varying load conditions and terrain, transforming a static system into an adaptive dynamic one.
Solution Approach 2:
The control unit receives feedback from multiple sensors measuring vehicle speed, engine output speed, pump displacement, and deceleration requests. This feedback loop enables the system to determine actual vehicle momentum and adjust pump displacement accordingly, improving braking performance while adapting to changing conditions.
2Speed
If the pump displacement is reduced to brake the vehicle, then the vehicle speed is reduced, but the engine output speed must be maintained for auxiliary functions
Solution Approach 1:
The control system separates the control of vehicle speed (via pump displacement) from the control of engine output speed (via engine control unit). This segmentation allows independent optimization: pump displacement is reduced for braking while engine output speed is maintained for auxiliary functions, resolving the contradiction between these two requirements.
Solution Approach 2:
The hydrostatic transmission acts as an intermediary between the engine and the drive wheels. By controlling the pump displacement within this intermediary system, the vehicle speed can be reduced for braking while the engine continues to operate at optimal speed for auxiliary functions, decoupling the speed requirements of the two systems.
3Reliability
If a complex control system is implemented to improve braking performance, then braking efficiency is enhanced, but the device complexity increases
Solution Approach 1:
The control unit performs multiple functions: it controls pump displacement for braking, monitors vehicle momentum, processes deceleration requests, and communicates with the engine control unit. By consolidating these functions in a single multi-functional control unit, the system achieves improved braking performance without proportionally increasing overall system complexity.
Solution Approach 2:
The control system merges the braking control function with the existing transmission control architecture. The control unit integrates momentum determination, pump displacement control, and engine coordination into a unified system, reducing the need for separate dedicated components and minimizing the increase in 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 approach enhances braking performance by intelligently controlling the hydrostatic transmission, reducing the effort needed to brake the vehicle based on real-time dynamic conditions, thereby optimizing braking efficiency and safety.
Implementation Method 1
a variable displacement pump (5), in particular connected to the engine (2) to receive at least a portion of the engine output power, and a hydraulic motor (6) arranged to be supplied by the pump (5) with a fluid flow and configured to convert the fluid flow into mechanical power
Data Source
Figure 1
Figure 2~3
AI summary
A method for controlling a hydrostatic transmission (4) of a vehicle (1), the hydrostatic transmission (4) comprising a variable displacement pump (5) and a hydraulic motor (6) arranged to be supplied by the variable displacement pump (5) to drive an axle (3) of the vehicle (1), the method comprising the steps of determining a first dynamic quantity positively correlated to an overall mass of the vehicle (1) and/or a second dynamic quantity indicative of a slope of a road traveled by the vehicle (1), and controlling a displacement of the variable displacement pump (5) to brake the vehicle as a function of the first and/or second dynamic quantity.