Hydrostatic Transmission Angle Control Without RU Sensor
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Solution Overview
Problem
The existing infinitely variable hydro-mechanical transmissions in agricultural and industrial vehicles require an RU angle sensor to control the displacement of hydrostatic units, which increases costs and decreases reliability.
Innovation Solution
The method eliminates the need for an RU angle sensor by using existing signals and new control algorithms to indirectly determine and control the hydrostatic unit angles, leveraging existing signals and control algorithms to manage the displacement of hydrostatic units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an RU angle sensor is used to control the displacement of hydrostatic units, then the control precision is improved, but the cost increases and reliability decreases
Solution Approach 1:
The patent uses the CU hydrostatic unit as an intermediary to indirectly measure the RU hydrostatic unit angle. By measuring the CU unit's position and using the known mechanical relationship between CU and RU through the planetary gear set, the system determines RU angle without directly sensing it. This intermediary approach eliminates the need for a dedicated RU angle sensor while maintaining measurement precision.
Solution Approach 2:
The patent replaces the mechanical/electrical sensor system with a computational approach. Instead of using a physical angle sensor to directly detect RU position, the system uses control algorithms that calculate RU angle based on CU position measurements and the predetermined mechanical relationship. This substitution of physical sensing with computational determination improves reliability by eliminating the sensor while maintaining measurement accuracy.
2Measurement precision
If an RU angle sensor is installed, then the control accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The patent makes the existing CU hydrostatic unit and its angle sensor serve multiple functions. The CU unit not only performs its primary hydrostatic function but also acts as an indirect sensor for RU angle measurement. The existing angle sensor for CU is reused to determine RU position through computational methods, eliminating the need for additional dedicated sensors and reducing overall system complexity.
Solution Approach 2:
The patent extracts the angle measurement function from the RU hydrostatic unit itself and relocates it to the CU unit through computational methods. By separating the measurement function from the specific hydrostatic unit being measured, the system uses the CU unit's position data and the known mechanical relationship to derive RU angle, thereby eliminating the need for a separate RU angle sensor and reducing device complexity.
3Force
If a synchronizer is used to couple the CU hydro to C1 or C2, then the torque delivery is improved, but the speed difference requirement increases the control difficulty
Solution Approach 1:
The patent uses feedback control to monitor the speed difference between the CU hydrostatic unit and the gear to be engaged (C1 or C2). The control system continuously measures this speed difference and adjusts the CU hydro unit's speed accordingly to minimize the difference before synchronizer engagement. This feedback mechanism ensures that the speed difference remains within the required threshold for proper synchronizer engagement, making the operation easier and more reliable.
Solution Approach 2:
The patent performs preliminary speed matching before synchronizer engagement by using the control system to adjust the CU hydro unit's speed to closely match the target gear speed. This preliminary action of pre-synchronizing the speeds ensures that when the synchronizer engagement is commanded, the speed difference is already minimal, facilitating smooth and reliable torque delivery without requiring the operator to manually manage the speed difference.
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 reduces costs and enhances reliability by eliminating the need for an additional sensor, allowing for precise control of hydrostatic unit angles without the sensor's limitations, thereby improving the overall performance of the transmission system.
Implementation Method 1
Two hydrostatic units are used in a closed hydraulic loop
Implementation Method 2
The hydrostatic unit's respective displacements per revolution vary with the angle between their swashplate and piston block
Implementation Method 3
The planetary gear set sums torque provided directly from the engine with that provided by the hydrostatic units
Implementation Method 4
two electro-hydraulic proportional valves
Data Source
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AI summary
A method is provided for adjusting the displacement angles of two hydrostatic units in an infinitely variable hydro-mechanical transmission.