Hydraulic Unit Flow Control With Pump Leakage Compensation
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Solution Overview
Problem
Hydraulic units with rotational-speed-controlled pumps face inefficiencies due to leakage, which affect the control and distribution of fluid flows for actuating slave cylinders and cooling/lubrication in drivetrains, particularly in electrically operated systems, where existing methods fail to accurately determine and correct for leakage-related losses.
Innovation Solution
A method that uses a rotational-speed-controlled pump with switching valves to manage fluid flows, determines efficiency by integrating fluid flow over filling time, and adjusts fluid output based on calculated efficiency, allowing for continuous correction of leakage-related losses, enabling precise control of fluid flows for both actuation and cooling/lubrication tasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rotational-speed-controlled pump is used to provide fluid flows for actuating slave cylinders and cooling/lubrication, then the pump can deliver required volume flows for multiple functions, but leakage occurs which reduces system efficiency and affects control precision
Solution Approach 1:
The control device continuously determines the actual volume flow delivered by the pump based on the actuation quantity of the slave cylinder and compares it with the theoretically expected flow. This feedback mechanism enables real-time detection of leakage and dynamic adjustment of pump output to compensate for losses, maintaining system efficiency despite the pump's inherent leakage characteristics
Solution Approach 2:
The system dynamically adjusts pump operational parameters (rotational speed, volume flow) based on determined efficiency values. By changing these parameters in response to detected leakage conditions, the system optimizes performance and compensates for leakage effects across varying operating conditions
2Quantity of substance
If the pump operates at high rotational speed to meet cooling/lubrication volume flow requirements, then sufficient fluid is provided for thermal management, but leakage increases proportionally reducing actuation precision
Solution Approach 1:
The pump output is segmented into different fluid flow paths: one for actuating slave cylinders and another for cooling/lubrication. The control device independently manages these flows by determining actual delivery quantity based on slave cylinder actuation and using this information to compensate for leakage effects, thereby maintaining precision in the actuation path while ensuring sufficient flow for cooling
Solution Approach 2:
The control device acts as an intermediary that processes information about actual pump delivery and slave cylinder actuation quantity. It uses this intermediate information to calculate efficiency and determine corrected volume flow requirements, enabling precise control despite the presence of leakage
3Device complexity
If leakage is not compensated for, then the system structure remains simple, but efficiency decreases and control accuracy deteriorates over time due to wear and temperature effects
Solution Approach 1:
The system performs self-diagnosis and self-correction by automatically determining its own efficiency based on the relationship between pump output and slave cylinder actuation. This self-service capability allows the system to detect and compensate for leakage without external intervention, maintaining reliability while keeping the overall structure relatively simple
Solution Approach 2:
The control device continuously monitors actual pump delivery versus expected delivery and uses this feedback to dynamically adjust control signals. This closed-loop feedback mechanism compensates for efficiency losses due to wear and temperature effects, maintaining consistent performance without requiring complex mechanical compensation mechanisms
Data Source
AI summary
A method for controlling a hydraulic unit with a rotational-speed-controlled pump, which, at an outlet side, provides at least two fluid flows in a manner switched by means of switching valves, for actuating at least one slave cylinder and for providing a volume flow which is controlled based on a rotational speed of the pump. To set the volume flow, an efficiency of the pump is calculated based on a comparison of a known slave cylinder volume of the at least one slave cylinder and a quantity of fluid of the pump for the filling of the at least one slave cylinder.