Valve Positioner Diagnostics Using Master Controller Approximation
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Solution Overview
Problem
Existing valve control devices in process plants face challenges in diagnosing faults due to incomplete consideration of interference effects from the interaction with master process controllers, and limited availability of process signals for slave valve control devices, making it difficult to identify the actual cause of issues within or outside the valve control device.
Innovation Solution
A positioner for valve control devices is designed to generate a control variable based on command and actual position signals, incorporating a configurable controller model and inversion module to approximate master process controller signals, allowing for diagnostic routines that account for signals not directly available, thereby identifying fault causes within and outside the valve control device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If diagnostic routines are carried out using only locally available signals in the valve control device, then device complexity is reduced, but measurement precision and reliability of fault diagnosis deteriorate due to incomplete consideration of interference effects from master process controllers
Solution Approach 1:
The patent introduces an intermediary element: a model of the master process controller that acts as a mediator between the limited local signals and the comprehensive diagnostic analysis. This model receives the process control signal and reconstructs the master controller's behavior, enabling accurate fault diagnosis without directly accessing all master controller signals. The intermediary model bridges the gap between available local data and the need for comprehensive system understanding.
Solution Approach 2:
The patent creates a copy or replica of the master process controller's behavior through a mathematical model. Instead of directly accessing the master controller's internal signals, the system generates an approximation of the master controller's output based on the process control signal. This copying approach allows the slave valve control device to perform accurate diagnostics as if it had direct access to all master controller signals, while maintaining device simplicity.
2Reliability
If all process signals from the master process controller are made available to the slave valve control device, then reliability of fault diagnosis improves, but device complexity and signal transmission requirements worsen
Solution Approach 1:
The patent extracts only the essential information needed for diagnostic purposes from the master process controller's signal set. Instead of transmitting all process signals to the slave valve control device, the system extracts the process control signal and uses it to generate an approximation of the master controller's behavior. This extraction approach maintains diagnostic reliability while significantly reducing signal transmission and processing complexity.
Solution Approach 2:
The patent creates a simplified copy of the master process controller's diagnostic functionality within the slave valve control device. By implementing a mathematical model that replicates the master controller's behavior based on limited input signals, the system achieves reliable fault diagnosis without requiring complex signal transmission infrastructure or additional hardware components.
3Loss of information
If approximation of master process controller signals is implemented, then completeness of diagnostic analysis improves, but device complexity and computational requirements worsen
Solution Approach 1:
The patent implements a mathematical model that copies the essential behavior of the master process controller. This model uses the available process control signal to generate an approximation of the master controller's output, thereby recovering diagnostic information that would otherwise be lost. The copying approach is implemented through software or firmware algorithms rather than additional hardware, minimizing the increase in device complexity while maximizing information completeness.
Solution Approach 2:
The patent transforms the diagnostic approach by changing parameters from direct signal measurement to mathematical approximation. Instead of relying on direct access to multiple master controller signals, the system changes the diagnostic parameters to use a single process control signal combined with a mathematical model. This parameter change reduces information loss while keeping the electronic implementation relatively simple through algorithmic processing.
Data Source
AI summary
In a position closed-loop controller (31) for a valve control device (1) of a process engineering plant (100), comprising a first signal input (11) for a pilot signal, such as a process control signal (pg) from a process closed-loop controller (120) of the process engineering plant (100), a second signal input for a position actual signal (i) with regard to a control valve (35), wherein the position control-loop controller (31) is designed to generate a more particularly pneumatic control variable (g) for an actuator (33) to actuate the control valve on the basis of the pilot signal and the position actual signal (i) and comprises a more particularly pneumatic control output for the control variable (g). According to the invention, the position closed-loop controller (31) is configured to calculate an approximation signal (ap), by means of a configurable closed-loop controller model based on a particular closed-loop controller, more particularly the process closed-loop controller (120), proceeding from the pilot signal, wherein the closed-loop controller model is configured such that a signal generated by the particular closed-loop controller proceeding from the approximation signal (ap) corresponds to the pilot signal.