Hydraulic Valve Control for Load-Independent Branch Flow Precision
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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 and errors in valve position and pressure sensors, leading to flow rate errors that are affected by varying load conditions on multiple actuators.
Innovation Solution
The implementation of a construction machine with a controller that calculates target opening areas for meter-in and meter-out valves based on pressure differences between supply and actuator pressures, reducing differential pressures across valves and minimizing errors caused by hydrodynamic forces and sensor errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the differential pressure across the meter-in valve increases to supply hydraulic fluid to multiple actuators with different loads, then the flow rate increases, but the hydrodynamic force on the valve body increases causing flow rate errors
Solution Approach 1:
The system uses feedback control by continuously monitoring the actual flow rate and comparing it with the target flow rate. The controller adjusts the valve opening area based on the deviation between actual and target flow rates, compensating for hydrodynamic forces and sensor errors to maintain precise flow rate control.
Solution Approach 2:
The system dynamically changes the valve opening area parameter based on operating conditions. By adjusting the valve opening area in response to differential pressure changes and load variations, the system maintains accurate flow rate control across different operating conditions despite hydrodynamic forces and sensor inaccuracies.
2Measurement precision
If the differential pressure across the meter-in valve decreases when loads on actuators are similar, then flow rate control precision improves, but sensor errors become more significant
Solution Approach 1:
The feedback control mechanism continuously monitors flow rate deviations and compensates for sensor errors by adjusting the valve opening area. This ensures reliable control even when differential pressure is low and sensor errors have a larger relative impact on the control signal.
Solution Approach 2:
The system prepares for potential control deviations by using feedback compensation that anticipates and corrects for sensor errors before they significantly affect operation. The controller continuously adjusts valve opening areas to cushion against the impact of sensor inaccuracies.
3Productivity
If the opening area of the meter-in valve is reduced to control flow rate, then the differential pressure increases, but the hydrodynamic force on the valve body increases causing larger opening area errors
Solution Approach 1:
The feedback control system monitors the actual flow rate and adjusts the valve opening area to compensate for manufacturing precision errors and hydrodynamic forces. By continuously comparing target and actual flow rates, the system corrects opening area deviations caused by differential pressure variations and hydrodynamic effects.
Solution Approach 2:
The system dynamically adjusts the valve opening area parameter based on real-time operating conditions including differential pressure and flow rate requirements. This adaptive parameter change compensates for manufacturing tolerances and hydrodynamic forces that would otherwise cause significant opening area errors.
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 to reduce flow rate errors and maintain accurate operation velocities.
Implementation Method 1
a hydraulic pump (2a) and a controller (100). The controller (100) has a meter-in valve control section (130) that calculates a target opening area of a first meter-in valve (53a, 53b) according to a pressure difference between the supply pressure and the first meter-in pressure
Implementation Method 2
hydrodynamic forces that act on control valves, errors of valve position sensors and errors of pressure sensors are not taken into consideration
Data Source
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.