Electrohydraulic Positioning Control With Redundant Servo Paths
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Solution Overview
Problem
Hydraulic servo control systems face challenges in maintaining system uptime and reliability due to the lack of effective redundancy and online serviceability, leading to potential operational downtime and contamination buildup.
Innovation Solution
The implementation of a redundant hydraulic servo control system with primary and backup servo valves and controllers, along with automatic failover processes and online serviceability features, allows for continuous operation and air bleeding without interrupting active control, and reduces contaminant buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy is provided by including doubled coils on servo valves with shared hydraulic paths, then system reliability is improved, but device complexity increases
Solution Approach 1:
The system is divided into two independent redundant servo valve assemblies, each with its own hydraulic path from fluid supply to actuator. This segmentation allows one assembly to fail while the other continues operation, providing reliability without requiring complex shared path redundancy
Solution Approach 2:
A shuttle valve acts as an intermediary component that automatically directs fluid flow from either the primary or backup servo valve to the actuator. This mediator enables automatic failover without complex control logic, resolving the contradiction between reliability and complexity
2Productivity
If the closure member is actuated at high velocity for rapid air bleeding, then air removal efficiency is improved, but system stability deteriorates due to fluid turbulence
Solution Approach 1:
The closure member is actuated in periodic cycles rather than continuously, allowing the system to alternate between air bleeding mode (high velocity) and normal operation mode (low velocity). This periodic action maintains air removal efficiency while preventing sustained turbulence that would destabilize the fluid
Solution Approach 2:
The system performs air bleeding as a preliminary action before normal operation begins. By removing air upfront at high velocity when the actuator is stationary or moving minimally, the system avoids turbulence during critical positioning operations, thus maintaining both efficiency and stability
3Reliability
If multiple drain periods and flushing periods are implemented with varying velocities, then contaminant removal is improved, but operation time increases
Solution Approach 1:
The system implements a multi-phase flushing procedure where different velocities and durations are applied sequentially. Initial high-velocity phases remove major contaminants quickly, followed by lower-velocity phases that clear residual particles. This partial action approach removes sufficient contaminants without requiring exhaustive cleaning that would consume excessive time
Solution Approach 2:
The system dynamically changes operating parameters (velocity, drain period duration, flushing period duration) during the service cycle. By varying these parameters across multiple phases, the system achieves thorough contaminant removal at different stages without maintaining constant high-intensity operation, thus balancing effectiveness with time efficiency
Data Source
AI summary
The subject matter of this specification can be embodied in, among other things, an electrohydraulic positioning control system that includes a shuttle valve configured to direct fluid flow between a selectable one of a first fluid port and a second fluid port, and a fluid outlet configured to be fluidically connected to a fluid actuator, a first servo valve controllable to selectably permit and block flow between the first fluid port, a fluid source, and a fluid drain, a second servo valve controllable to selectably permit and block flow between the second fluid port, the fluid source, and the fluid drain, a first servo controller configured to provide a first health signal and control the first servo valve based on a second health signal, and a second servo controller configured to provide the second health signal and control the second servo valve based on the first health signal.