Hydraulic Pilot Valve Control for Solenoid Stuck-Open Faults
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Solution Overview
Problem
Existing work machines cannot accurately determine if a solenoid valve is stuck-open, leading to either unnecessary actuator inoperability or failure to stop the actuator when a stuck-open condition occurs, due to sensor abnormalities.
Innovation Solution
A work machine equipped with a hydraulic pump, directional control valve, solenoid valve, shut-off valve, and sensors, where a controller determines sensor abnormalities and adjusts the shut-off valve based on lever operation and sensor signals to manage the solenoid valve's state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shut-off valve is closed to make the actuator inoperable when sensor abnormality is detected, then the reliability of safety control is improved, but the availability of the actuator deteriorates due to unnecessary inoperability
Solution Approach 1:
The control system dynamically changes its behavior based on the operational state. When sensor abnormality is detected during neutral state, the system transitions to a restrictive mode (closing shut-off valve). When operation is detected, it transitions to a permissive mode (opening shut-off valve), allowing the actuator to operate dynamically despite the sensor abnormality, thus maintaining productivity while ensuring safety during idle periods.
Solution Approach 2:
The system changes the operational parameters of the shut-off valve based on the combination of sensor abnormality detection and lever operation state. The valve position parameter is adjusted from closed (during neutral with abnormality) to open (during operation with abnormality), allowing flexible control that balances safety requirements with operational needs.
2Productivity
If the shut-off valve is opened when sensor abnormality is detected, then the availability of the actuator is improved, but the reliability of safety control deteriorates due to inability to stop actuator when stuck-open occurs
Solution Approach 1:
The control system dynamically adjusts the shut-off valve state based on real-time detection of lever operation. When operation is detected despite sensor abnormality, the system opens the shut-off valve to maintain productivity. When neutral state is detected, it closes the valve to restore safety control, creating a dynamic response that adapts to operational context.
Solution Approach 2:
The lever operation state acts as an intermediary signal that mediates between the sensor abnormality condition and the shut-off valve control. This intermediary information allows the system to make informed decisions about valve positioning, balancing the conflicting requirements of safety and availability based on actual operational context.
3Device complexity
If the system cannot determine sensor abnormality, then the complexity of the control system is reduced, but the precision of stuck-open detection deteriorates
Solution Approach 1:
The system implements feedback by continuously monitoring the second sensor's output and comparing it against expected ranges. When the sensor output falls outside the normal range, the controller identifies this as an abnormality condition and adjusts control accordingly. This feedback mechanism enables precise detection of both sensor abnormalities and stuck-open conditions without requiring complex additional hardware.
Solution Approach 2:
The system replaces complex mechanical detection mechanisms with electronic sensor-based detection and software-based abnormality determination. The controller uses programmed logic to analyze sensor signals and determine abnormalities, substituting mechanical complexity with electronic control and signal processing, thereby maintaining measurement precision while reducing mechanical device complexity.
Data Source
AI summary
In a work machine including a solenoid valve that generates a pilot pressure to drive a directional control valve with use of the delivery pressure of a pilot pump as a source pressure, a shut-off valve that shuts off a hydraulic operating fluid from the pilot pump to the solenoid valve, a first sensor that senses the amount of operation of an operation lever, and a second sensor that senses a state amount relating to operation of the solenoid valve, whether or not an abnormality of the second sensor exists is determined on the basis of a sensing signal of the second sensor. When it is determined that the second sensor is abnormal, on the basis of a sensing signal of the first sensor, an opening command is made to the shut-off valve if operation of the operation lever is sensed, and a closing command is made to the shut-off valve if the neutral state of the operation lever is sensed.