Fail Operational Modes for Electro-Hydraulic Valve Assemblies
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Solution Overview
Problem
Existing electro-hydraulic systems in work machines fail to maintain operational stability when pressure or position sensors fail, rendering hydraulic actuators inoperable, as they lack effective fail-safe modes to manage sensor faults.
Innovation Solution
The method involves providing valve assemblies with pressure sensors in communication with an electronic system controller, detecting fault conditions, and initiating specific fail operational modes based on the sensor location relative to the hydraulic actuator, allowing the system to transition to alternative operational states to maintain functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are installed in electro-hydraulic systems to monitor system state, then system control precision is improved, but system reliability deteriorates when sensor failures occur
Solution Approach 1:
The system performs preliminary actions by detecting sensor faults and transitioning to fail operational modes before complete system failure occurs. The electronic system controller continuously monitors sensor signals and proactively switches to alternative operational modes when faults are detected, preventing total system shutdown and maintaining limited functionality.
Solution Approach 2:
The system changes operational parameters by switching between different operational modes based on sensor fault conditions. When a pressure sensor fault is detected, the controller modifies system parameters by activating fail operational modes that adjust valve assembly operations and hydraulic flow characteristics to maintain safe and functional operation despite the sensor failure.
2Reliability
If multiple pressure sensors are installed in the hydraulic system, then system monitoring capability is improved, but device complexity increases
Solution Approach 1:
The electronic system controller performs multiple functions by serving as both the primary control unit and the fault detection system. The same controller that manages normal hydraulic operations also monitors sensor signals for faults and executes fail operational mode transitions, eliminating the need for separate monitoring hardware and reducing overall system complexity.
Solution Approach 2:
The system provides self-service through autonomous fault detection and mode transition capabilities. The electronic controller automatically monitors sensor signals, detects faults without external intervention, and independently switches to fail operational modes, eliminating the need for external monitoring systems or manual fault detection procedures.
3Reliability
If fail operational modes are implemented based on sensor location, then system safety is improved, but control system complexity increases
Solution Approach 1:
The control system is segmented into distinct operational modes corresponding to different sensor fault locations. Each fail operational mode is specifically designed for particular sensor failure scenarios (upstream vs. downstream pressure sensors), allowing targeted responses that simplify the control logic for each specific fault condition rather than requiring a single complex universal response.
Data Source
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AI summary
Methods for initiating and implementing fail operational modes in an electro-hydraulic system are disclosed. In one step, a plurality of valve assemblies is provided wherein each of the valve assemblies has a pressure sensor and a position sensor in communication with an electronic system controller. The valve assemblies are in fluid communication with a hydraulic actuator, for example a linear actuator or hydraulic motor. In one step, a fault condition with one of the sensors is detected. The method may also include the steps of determining the type and location of the sensor associated with detected fault condition. In another step, an actuator state is determined wherein the actuator is in a passive state or overrunning state. Another step is initiating and implementing one of a plurality of fail operational modes based on the determination of the sensor type and location, and the actuator state.