Hydraulic Meter-Out Control for Negative Load Sensor Failure
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Solution Overview
Problem
Construction machines with hydraulic actuators face operability issues and potential damage due to breathing phenomena caused by meter-out pressure loss variations, especially when the arm's attitude changes and pressure sensors malfunction, leading to inaccurate detection of negative loads.
Innovation Solution
A hydraulic control system with a control valve, meter-out flow line, variable restrictor, and pressure sensors that adjust the spool position and restrictor opening area based on detected negative load and operation lever position, ensuring reduced pressure loss and preventing damage even during pressure sensor failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the opening area of the meter-out restrictor is reduced to support negative load, then the rod side pressure increases to support the negative load, but the flow rate control precision deteriorates due to pressure sensor malfunction
Solution Approach 1:
The system changes the control parameter from direct pressure sensor feedback to operation lever position feedback. When the pressure sensor malfunctions, the controller switches to using the operation lever position to determine the required rod side pressure, thereby maintaining control precision without relying on the faulty pressure sensor
Solution Approach 2:
The operation lever position serves as an intermediary parameter to indirectly determine the required rod side pressure. Instead of directly measuring pressure, the system uses the operator's input position to calculate the appropriate pressure, bypassing the need for direct pressure sensor measurement
2Loss of energy
If the variable restrictor opening area is dynamically controlled based on pressure sensor detection, then the meter-out pressure loss is optimized, but the system reliability deteriorates when pressure sensor fails
Solution Approach 1:
The system dynamically adjusts the restrictor opening area based on real-time operation conditions. When the pressure sensor is functioning, it uses actual pressure feedback; when the sensor fails, it dynamically switches to using operation lever position data to maintain appropriate pressure control, ensuring continuous adaptive operation
Solution Approach 2:
The system prepares for potential pressure sensor failure by having a backup control method ready. The controller is programmed to switch to using operation lever position data if pressure sensor data becomes unavailable, providing a cushion against system failure and maintaining operability
3Productivity
If the meter-out restrictor opening area is increased to improve flow rate, then the operating speed increases, but the negative load support capability deteriorates
Solution Approach 1:
The restrictor opening area is dynamically adjusted based on the detected negative load magnitude. When negative load is detected, the opening area is reduced to increase pressure and support the load; when negative load is absent, the opening area is increased to improve flow rate and operating speed, achieving adaptive optimization
Data Source
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AI summary
Disclosed is a hydraulic control system of a construction machine capable of achieving a reduction in meter-out pressure loss in accordance with variation of a negative load acting on a hydraulic actuator and capable of preventing deterioration in operability even when an abnormal condition arises in a pressure sensor detecting the magnitude of a negative load. There are provided meter-out flow lines through which a hydraulic fluid discharged from a hydraulic actuator flows; variable restrictors provided in the meter-out flow lines; a load sensor detecting the magnitude of a negative load which is a load applied to the hydraulic actuator by an external force and which is a load in the same direction as the operating direction of the hydraulic actuator; and a control device which, when the load abnormality sensor does not detect any abnormality in the load sensor, reduces the sum total of the opening areas of the variable restrictors in accordance with an increase in the magnitude of the negative load detected by the load sensor and the operation amount detected by the operation amount sensor and which, when the load abnormality sensor detects abnormality in the load sensor, reduces the sum total of the opening areas of the variable restrictors to a predetermined value in accordance with the operation amount detected by the operation amount sensor.