Hydromechanical Transmission Control for Pump Saturation Limits
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Solution Overview
Problem
Hydromechanical transmission control strategies face issues such as motor overspeeding, hydraulic pump saturation, and inefficiencies, leading to reduced motor lifespan and constrained maximum output torque, which affect transmission performance.
Innovation Solution
A method is developed to maintain a displacement set-point of a variable displacement hydraulic motor within a working zone, with torque and kinematic constraints determining the boundaries of this zone, ensuring efficient operation and maximum output torque while preventing pump saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydromechanical transmission control strategies are used, then the system can operate, but the hydraulic motor experiences overspeeding which increases motor degradation and decreases motor lifespan
Solution Approach 1:
The patent implements dynamic control of the hydraulic motor displacement set-point by defining a working zone with boundaries that adapt to current operating conditions. The controller continuously adjusts the displacement set-point within this working zone based on real-time parameters such as motor speed, torque demand, and pump characteristics, preventing overspeeding while maintaining operational flexibility.
Solution Approach 2:
The control system uses feedback from motor speed sensors and torque measurements to continuously monitor operating conditions and adjust the hydraulic motor displacement set-point accordingly. The controller compares actual motor speed against the working zone boundaries and modifies the displacement command to keep the motor operating within safe speed limits, thereby preventing degradation and extending lifespan.
2Reliability
If conventional control strategies are used, then the transmission can operate, but the fluid in the hydraulic pump becomes saturated causing pump cavitation and degradation
Solution Approach 1:
The patent dynamically determines the working zone boundaries based on real-time pump operating conditions, including fluid saturation thresholds. The controller continuously adjusts the hydraulic motor displacement set-point to maintain pump operation below saturation levels, preventing cavitation and degradation while allowing maximum operational flexibility.
Solution Approach 2:
The control system proactively prevents pump saturation by establishing working zone boundaries that account for pump capacity limits and fluid saturation characteristics. Before saturation occurs, the controller adjusts the displacement set-point to reduce pump demand, thereby preventing cavitation and extending pump lifespan.
3Productivity
If conventional control strategies are used, then the transmission can operate, but inefficiencies occur and the maximum output torque is constrained
Solution Approach 1:
The patent implements dynamic optimization of the hydraulic motor displacement set-point within the working zone to maximize transmission efficiency and achieve maximum output torque. The controller continuously adjusts the displacement command based on torque demand, speed requirements, and efficiency maps, enabling the transmission to operate at optimal efficiency points while delivering maximum required torque.
Solution Approach 2:
The control system optimizes transmission performance by dynamically changing operating parameters including hydraulic motor displacement, pump displacement, and differential pressure within the working zone boundaries. These parameter adjustments enable the transmission to achieve maximum output torque while maintaining high efficiency by operating within optimal parameter ranges.
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 transmission efficiency, controllability, and motor longevity by maintaining motor torque control and avoiding pump saturation, allowing the transmission to achieve maximum output torque and efficient operation across a wide range of conditions.
Implementation Method 1
a variable displacement hydraulic pump (306) of the hydrostatic assembly (302)
Implementation Method 2
a variable displacement hydraulic motor (304) of the hydrostatic assembly (302)
Data Source
AI summary
Methods and systems for transmission control are provided. In one example, a transmission system operating method includes maintaining a displacement set-point of a variable displacement hydraulic motor in a hydrostatic assembly within a working zone, where at least a portion of a boundary of the working zone is determined based on a torque constraint of the hydrostatic assembly. The transmission system includes the hydrostatic assembly that includes the hydraulic motor that is hydraulically coupled in parallel with a variable displacement hydraulic pump and a gearbox mechanically coupled to the hydrostatic assembly and including one or more clutches.