Hydraulic Branch Flow Control for Multi-Actuator Construction Machines
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Solution Overview
Problem
Existing construction machines, such as hydraulic excavators, face challenges in accurately controlling the operation velocity of hydraulic actuators due to hydrodynamic forces, errors in valve position sensors, and pressure sensors, especially when dealing with varying load conditions across multiple actuators.
Innovation Solution
The implementation of a system with pressure sensors to measure supply and meter-in pressures, and a controller that calculates target opening areas for meter-in and meter-out valves based on pressure differences, reducing differential pressures across meter-in valves and minimizing errors caused by hydrodynamic forces and sensor errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the differential pressure across a meter-in valve increases, then the opening area required for obtaining a desired meter-in flow rate decreases, but flow rate errors increase due to hydrodynamic forces and sensor errors
Solution Approach 1:
The controller dynamically adjusts the target opening area of the meter-in valve based on real-time differential pressure measurements. When differential pressure increases, the system compensates by adjusting the opening area to maintain accurate flow rate control, counteracting the effects of hydrodynamic forces and sensor errors that would otherwise cause flow rate deviations
Solution Approach 2:
The system employs pressure sensors to continuously measure the differential pressure across the meter-in valve and feeds this information back to the controller. The controller uses this feedback to calculate and adjust the target opening area, creating a closed-loop control system that maintains flow rate precision despite varying differential pressures and load conditions
2Productivity
If loads acting on multiple hydraulic actuators differ significantly, then hydraulic fluid flows preferentially to actuators with lower loads, but simultaneous supplying becomes difficult requiring complex valve adjustment
Solution Approach 1:
The system replaces complex mechanical valve adjustment mechanisms with an electronic control system. The controller receives pressure signals from sensors on multiple actuators and automatically calculates the appropriate opening areas for each meter-in valve, eliminating the need for manual mechanical adjustment and enabling simultaneous operation of multiple actuators with different loads
Solution Approach 2:
The controller serves multiple functions: it monitors differential pressures across multiple meter-in valves, calculates target opening areas for each valve based on load conditions, and adjusts all valves simultaneously to maintain balanced hydraulic fluid distribution. This multi-functional approach simplifies the overall system while enabling complex simultaneous actuator operations
3Measurement precision
If the opening area of a meter-in valve is adjusted to compensate for differential pressure, then flow rate control improves, but hydrodynamic forces on the valve body increase causing opening area errors
Solution Approach 1:
The system continuously measures the actual differential pressure across the meter-in valve using pressure sensors and feeds this information back to the controller. The controller uses this real-time feedback to dynamically adjust the target opening area, compensating for hydrodynamic forces that would otherwise cause opening area errors and maintaining accurate flow rate control
Solution Approach 2:
The controller dynamically changes the target opening area parameter based on the measured differential pressure. By adjusting this parameter in real-time, the system compensates for hydrodynamic forces acting on the valve body, ensuring that flow rate control precision is maintained despite the presence of these harmful forces
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 precise control of branch flows to multiple hydraulic actuators, independent of load conditions, by adjusting valve opening areas and flow rates, thereby reducing errors and improving operational accuracy.
Implementation Method 1
a first pressure sensor that senses a first meter-in pressure that is a pressure on the one of the supply and discharge ports of the first hydraulic actuator; a second pressure sensor that senses a second meter-in pressure that is a pressure on the one of the supply and discharge ports of the second hydraulic actuator; a third pressure sensor that senses a supply pressure that is a delivery pressure of the hydraulic pump
Implementation Method 2
a controller having a meter-in valve control section configured to calculate a target opening area of the first meter-in valve according to a pressure difference between the supply pressure and the first meter-in pressure, and calculate a target opening area of the second meter-in valve according to a pressure difference between the supply pressure and the second meter-in pressure
Implementation Method 3
the rates of flows passing through the valves are determined by the opening areas of the valves (the movement amounts of the valve bodies), and the differential pressures across the valves
Data Source
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AI summary
To provide a construction machine that can highly precisely control branch flows from a hydraulic pump to a plurality of hydraulic actuators without being affected by load conditions. A controller (100) has a meter-out valve control section (140) configured to calculate a target opening area of a second meter-out valve (65a) (65b) according to a pressure difference between a supply pressure and a second meter-in pressure, or calculate a target opening area of a first meter-out valve (55a) (55b) according to a pressure difference between the supply pressure and the first meter-in pressure.