Double-Acting Pneumatic Actuator Pressure Control for Position and Stiffness
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Solution Overview
Problem
Double-acting pneumatic actuators in control valves face challenges in simultaneously controlling position and stiffness, leading to undesired variations and reduced durability due to the effects of process fluid forces and actuator wear.
Innovation Solution
A method and system that measure pressures in the pneumatic chambers to compute a numerical indicator of stiffness, allowing for the adjustment of pressures to control the actuator position while simultaneously increasing or decreasing stiffness by activating pneumatic devices to provide controlled flow rates, thereby minimizing position and stiffness errors.
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 from process fluids 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 stiffness characteristic of the actuator based on operational requirements, allowing the system to optimize between rapid position control and resistance to buffeting forces. This is achieved through active control of pneumatic pressure in the actuator chambers, which changes the force characteristics in real-time.
Solution Approach 2:
The patent changes the physical parameter of actuator stiffness by adjusting pneumatic pressure levels. By varying the pressure in the pneumatic chambers, the system modifies the stiffness parameter of the actuator, enabling it to adapt between different operational states - higher pressure for rapid response and lower pressure for reduced sensitivity to external forces.
2Stability of the object's composition
If the actuator stiffness is reduced to limit the effect of buffeting forces on position fluctuations, then the position stability is improved, but the ability to rapidly control actuator position deteriorates
Solution Approach 1:
The system dynamically adjusts stiffness characteristics to overcome the trade-off between stability and speed. Rather than being constrained to a fixed stiffness value, the actuator can transition between different stiffness states, providing high stability when needed and rapid response when required, thus resolving the contradiction through time-varying control.
Solution Approach 2:
The patent utilizes parameter changes in pneumatic pressure to modify actuator stiffness. By controlling the pressure levels in the pneumatic chambers, the system can shift the stiffness parameter to appropriate values based on whether position stability or response speed is the priority at any given moment.
3Ease of operation
If conventional position control methods are used without stiffness consideration, then the actuator position can be controlled, but undesired variations in position occur due to process fluid forces
Solution Approach 1:
The patent implements feedback control by monitoring actuator position and comparing it to the desired position, then adjusting pneumatic pressures to eliminate position errors. This closed-loop control system continuously corrects deviations caused by process fluid forces, maintaining both ease of operation and position precision.
Solution Approach 2:
The system achieves precise position control by dynamically adjusting pneumatic pressure parameters in response to position feedback. When position deviations are detected, the control system modifies pressure levels to counteract the effects of process fluid forces and restore the desired position.
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 enables precise control of the actuator position and stiffness, improving the quality and durability of the process control system by reducing unwanted variations and wear on actuator components.
Implementation Method 1
A method is disclosed for controlling a double-acting pneumatic actuator... by controlling the two pneumatic signals to the actuator chambers... activating each of the pneumatic devices to provide a constant flow rate
Data Source
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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.