Pneumatic Actuator Pressure Equalization for Stick-Slip Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pneumatic actuators experience the stick-slip effect due to high static friction and low sliding friction, leading to sluggish control and overshooting of control valves, which is difficult to control and results in inefficient energy use and imprecise positioning.
Innovation Solution
A pneumatic drive system with a movable partition wall between working chambers, connected by a pneumatic short-circuit line that can be opened and closed by a compensating valve to equalize pressure and prevent overshooting, allowing for precise control and reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high pressure difference is applied to overcome static friction, then the control valve can be moved from rest position, but the actuator overshoots the target position due to sluggish pneumatic response
Solution Approach 1:
The system continuously monitors the actual position of the control valve and compares it with the target position. When the valve approaches the target position, the positioner reduces the pneumatic pressure difference to prevent overshooting, enabling precise positioning despite high static friction.
Solution Approach 2:
The pneumatic pressure difference is dynamically adjusted during the actuation process. High pressure difference is applied initially to overcome static friction, then gradually reduced as the valve approaches the target position to prevent overshooting and achieve precise positioning.
2Loss of energy
If the actuator remains idle for a long period with the control valve in the same position, then energy consumption is reduced, but static friction increases leading to stick-slip effect
Solution Approach 1:
Before actuating the control valve from a resting position, the positioner applies a preliminary high pressure signal to overcome the increased static friction that develops during idle periods. This preliminary action ensures reliable valve movement without requiring continuous high pressure during normal operation.
Solution Approach 2:
The system applies periodic pressure pulses or elevated pressure signals during idle periods to prevent excessive static friction buildup, maintaining actuator responsiveness while minimizing continuous energy consumption.
3Productivity
If a large pressure difference is used to break out of rest position, then the control valve can be actuated, but control precision is lost due to sluggish pneumatic response
Solution Approach 1:
The pneumatic pressure difference is dynamically adjusted during the actuation process. High pressure difference is applied initially to overcome static friction and achieve rapid actuation, then gradually reduced as the valve approaches the target position to enable precise positioning.
Solution Approach 2:
The positioner uses feedback from the position sensor to continuously adjust the pneumatic pressure. When the valve is far from the target, high pressure is applied for rapid movement; when接近 the target, pressure is reduced for precise positioning, optimizing both speed and precision.
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
The solution significantly improves control reactivity and precision by compensating for pressure differences, reducing overshooting, and optimizing energy use by allowing for immediate pressure equalization and precise positioning of control valves.
Implementation Method 1
If there is a pressure difference in the working chambers, the dividing wall is shifted in an adjusting direction, depending on which of the two chambers the adjusting pressure is higher
Implementation Method 2
The control valve is coupled to the movable partition wall in a force-transmitting manner, so that when the partition wall is displaced, the control valve is shifted in accordance with the regulation
Implementation Method 3
A compensating valve for closing and/or opening the short-circuit line is arranged in the short-circuit line. The compensating valve can be set electrically and is controlled by the positioner in such a way that in the event of a specific operating situation, the compensating valve can pneumatically short-circuit the first and the second working chamber for a working chamber pressure equalization
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The drive (1) has a working chamber (5) and a resetting chamber (21) that are pneumatically separated from each other by a movable adjusting piston (23) that is moved to an adjusting position during pressure difference in the chambers. A position regulator (7) outputs a pneumatic adjusting signal to the chambers. A counterbalance valve closes and opens a pneumatic bypass line, and is controlled by the regulator such that the valve short-circuits the chambers for chamber-pressure balance during exceeding of predetermined pneumatic actual-pressure difference between the chambers. An independent claim is also included for a method for operating a pneumatic drive for adjusting an adjustment fitting i.e. adjusting valve.