Double-Acting Pneumatic Actuator Stiffness Control for Stable Positioning
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Solution Overview
Problem
Double-acting pneumatic actuators in control valves face challenges in maintaining optimal stiffness to balance rapid position control and minimizing the impact of buffeting forces, leading to reduced durability and accuracy.
Innovation Solution
A system that dynamically controls the pressures in the pneumatic chambers of a double-acting pneumatic actuator to adjust its position and stiffness by measuring pressures and computing control signals to minimize position errors, allowing for real-time adjustment of actuator stiffness and position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the actuator stiffness is increased to rapidly control actuator position, then the position control speed is improved, but the effect of buffeting forces on position fluctuations increases
Solution Approach 1:
The patent applies dynamics by making the actuator stiffness adjustable rather than fixed. The control system dynamically modifies the pneumatic pressure in the actuator chambers in real-time, allowing the stiffness to adapt to different operating conditions. This resolves the contradiction by enabling high stiffness for rapid response when needed while reducing stiffness to minimize buffeting effects during steady-state operation.
Solution Approach 2:
The patent changes the physical parameter of pneumatic pressure to control actuator stiffness. By adjusting the pressure levels in the pneumatic chambers, the system can modify the stiffness characteristic of the actuator. This parameter change enables the system to optimize between rapid position control (higher pressure/stiffness) and minimizing position fluctuations (lower pressure/stiffness) based on process requirements.
2Stability of the object's composition
If the actuator stiffness is decreased to minimize the effect of buffeting forces, then the position stability is improved, but the position control speed deteriorates
Solution Approach 1:
The system uses dynamic control of pneumatic pressure to adjust actuator stiffness in real-time. During steady-state operation, the system maintains lower pressure to reduce stiffness and minimize the impact of buffeting forces on position stability. When rapid position changes are required, the system increases pressure to enhance stiffness and improve response speed, thus resolving the trade-off dynamically.
Solution Approach 2:
The control system modifies the pneumatic pressure parameter to regulate actuator stiffness. By decreasing pressure, the system reduces stiffness to minimize buffeting effects and improve position stability. Conversely, pressure can be increased to enhance stiffness for faster positioning, allowing the system to adapt to different operational demands.
3Speed
If fixed high pressure is maintained in pneumatic chambers to ensure rapid response, then the position control speed is improved, but the actuator wear increases and durability decreases
Solution Approach 1:
The system employs periodic or intermittent high-pressure application rather than continuous high pressure. The control system applies high pressure only when rapid position control is required, then reduces pressure during steady-state operation. This periodic action maintains the ability for rapid response while significantly reducing cumulative wear on actuator components, thereby improving durability.
Solution Approach 2:
The system dynamically changes the pneumatic pressure parameter based on control requirements. Instead of maintaining fixed high pressure, the system adjusts pressure levels - using high pressure temporarily for rapid positioning maneuvers and lowering pressure during normal operation. This reduces wear on seals and other components while preserving the capability for fast response when needed.
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 approach enhances the precision and durability of the actuator control system by allowing for real-time adjustments in stiffness, improving the ability to manage buffeting forces and maintain accurate position control.
Implementation Method 1
A double-acting pneumatic actuator changes position by adjusting pressures in two pneumatic chambers, where the pressures push on a piston connected to a stem
Implementation Method 2
The goal of the positioner and actuator combination is to quickly and accurately control actuator position and to minimize deviations in the actuator position in response to the forces generated by the process fluids flowing through the valve
Data Source
AI summary
A control loop for a double-acting pneumatic actuator is configured to generate two control signals, one for each of the two pneumatic chambers for the purpose of controlling the actuator position in view of operating constraints on the chamber pressures or the stiffness of the actuator. A numerical indicator of the stiffness may be computed in a variety of ways, for example, as the average of the two chamber pressures. In one embodiment a numerical indicator of stiffness is treated as an output of the system along with the position of the actuator. A multi-input multi-output control loop with position and pressure feedback may be used to simultaneously control the position and the stiffness of the actuator.