Axial Piston Pump Speed Control Using Adaptive Pressure Modeling
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Solution Overview
Problem
Existing hydrostatic axial piston pumps for mobile machines face challenges in achieving precise speed control, especially under varying loads, due to load sensitivity, high complexity, and accuracy issues, leading to reduced dynamics and increased parameterization complexity.
Innovation Solution
A hydrostatic axial piston pump with an adjustable swept volume and a learning and/or adaptation device that adapts a model of the actuating pressure dependent on the requested speed, allowing for precise speed control and reduced complexity by refining the model over time, potentially eliminating the need for conventional regulation and detection devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional regulation devices (EP-regulated or DA-regulated pump) are used for speed control, then speed control capability is provided, but load sensitivity and accuracy deteriorate under varying loads
Solution Approach 1:
The patent replaces mechanical feedback systems (EP-regulation with mechanical angle feedback) and pressure-dependent mechanical regulators (DA-regulation) with an electrically actuated pressure reducing valve controlled by an electronic control unit. This substitution of mechanical control systems with electronic control enables precise current-based actuation independent of load conditions, resolving the load sensitivity problem while maintaining speed control capability
Solution Approach 2:
The patent changes the control parameter from pressure-dependent mechanical regulation to current-dependent electrical actuation. The pressure reducing valve is actuated by an electromagnet whose coil current is directly controlled by the electronic control unit based on desired speed, rather than being indirectly controlled by mechanical feedback or pressure-dependent mechanisms. This parameter change enables accurate speed control independent of load variations
2Speed
If EP-regulated pump with mechanical feedback is used, then speed control is achieved, but device complexity and cost increase
Solution Approach 1:
The patent eliminates the mechanical feedback system (measure device for actual pivoting angle, mechanical feedback connections) by replacing it with an electrical control system. The electronic control unit receives speed signals and directly actuates the pressure reducing valve via an electromagnet, removing the need for mechanical angle sensors and feedback linkages, thus reducing device complexity and cost while maintaining speed control
Solution Approach 2:
The patent introduces an electronic control unit as an intermediary between the speed control signal and the pressure reducing valve actuation. This electronic intermediary processes the control signal and generates the appropriate coil current for the electromagnet, replacing the need for complex mechanical feedback intermediaries while achieving the same control objective
3Measurement precision
If additional pilot control for disturbance compensation is added to ET-regulated pump, then accuracy improves, but device complexity and parameterization requirements increase
Solution Approach 1:
The patent implements a self-adjusting pressure reducing valve where the electromagnet's coil current is directly controlled by the electronic control unit based on the desired speed signal. The system self-regulates the actuating pressure to achieve the target speed without requiring external pilot controls or disturbance compensation mechanisms, thereby maintaining accuracy while minimizing 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 enables robust speed control with high precision and dynamics, reduces the risk of control loop oscillations, and simplifies startup processes, achieving higher system robustness and accuracy while minimizing the need for detection devices.
Implementation Method 1
a first actuating pressure can be set via a first pressure reducing valve, said first actuating pressure being dependent on a first current at a first electromagnet of the first pressure reducing valve
Data Source
AI summary
A hydrostatic axial piston pump has adjustable swept volume and is configured for fluidic connection to a hydraulic motor of a hydrostatic propulsion drive in a hydraulic circuit. The hydrostatic axial piston pump includes an adjusting unit configured to adjust the swept volume. The adjusting unit has an actuating cylinder with a first actuating pressure chamber, in which a first actuating pressure can be set via a first pressure reducing valve. The first actuating pressure is dependent on a first current at a first electromagnet of the first pressure reducing valve. An electronic control device is configured to store a model of the first current in a manner which is dependent on a requested speed.