Digital Positioner PWM Control for Valve Air Consumption
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Solution Overview
Problem
Existing continuous conversion electropneumatic converters in control valve positioners consume excessive air, leading to high costs and environmental waste, especially when using process media like natural gas, and result in unnecessary valve movement due to constant pressure signals.
Innovation Solution
A digital positioner that generates a discrete output in the form of a pulse-width modulated current signal, reducing air consumption by only providing pressure to the valve actuator when necessary, using a valve controller to produce a PWM current signal that is converted to a PWM pressure output, and employing a supply and exhaust relay system to manage pressure efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous pressure signal is used to control the valve actuator, then the valve can be precisely controlled, but air consumption increases and causes unnecessary valve movement
Solution Approach 1:
The patent applies periodic action by converting the continuous pressure signal into a pulsed pressure signal that periodically activates the valve actuator. The controller delivers pressure in discrete pulses rather than continuously, reducing air consumption while maintaining control precision through timed activation sequences that move the valve to desired positions only when necessary.
Solution Approach 2:
The patent substitutes the traditional continuous mechanical pneumatic control system with a digital control system that uses microprocessors and software algorithms. This replacement enables intelligent decision-making about when pressure should be applied, replacing the continuous mechanical signal with a smart, event-driven control approach that reduces unnecessary air consumption.
2Stability of the object's composition
If continuous pressure signal is used to control the valve actuator, then the valve position can be maintained, but unnecessary valve movement occurs and increases operational costs
Solution Approach 1:
The patent implements feedback control by continuously monitoring the valve position and comparing it with the desired setpoint. The controller receives feedback signals from position sensors and adjusts pressure application accordingly, maintaining valve position stability while avoiding unnecessary movements. The feedback mechanism enables the system to detect when the valve has reached its target position and stop applying pressure, preventing wasteful operational cycles.
Solution Approach 2:
The controller uses periodic monitoring and action by checking valve position at intervals and applying pressure only when deviation from the setpoint is detected. This periodic control approach maintains stability by responding to actual needs rather than continuously actuating, thereby improving operational efficiency by eliminating redundant valve movements.
3Adaptability or versatility
If process media like natural gas is used for fluid supply, then the system can operate with available resources, but constant air bleed becomes expensive and environmentally harmful
Solution Approach 1:
The patent changes the temporal parameters of pressure application from continuous to pulsed operation. By modifying the time-domain characteristics of the pressure signal, the system maintains adaptability to use available process media while dramatically reducing the total volume of gas consumed. This parameter change transforms the operation from a continuously harmful bleed to an efficient, on-demand pressure application.
Solution Approach 2:
The patent replaces the traditional mechanical continuous bleed system with a digital control system that intelligently manages gas consumption. This substitution enables the system to maintain operational flexibility while eliminating constant environmental harm by applying pressure only when and where needed, rather than through continuous passive bleeding.
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
Significantly reduces air consumption and associated costs, minimizes unnecessary valve movement, and decreases environmental impact by providing pressure only when required, thus optimizing valve control.
Implementation Method 1
the electropneumatic converter converts the PWM current signal to a PWM pressure signal
Data Source
AI summary
A digital positioner for a valve includes a valve controller configured to obtain a set point value for a valve travel of a valve, and generate a pulse-width modulated current signal based on the set point value. The digital positioner also includes a current-to-pressure converter configured to receive the pulse-width modulated current signal from the valve controller, convert the pulse-width modulated current signal to a pulse-width modulated pressure signal, and provide the pulse-width modulated pressure signal to a pneumatic actuator in the valve to adjust a position of the valve.