Nonlinear Predictive Control for Gas-Phase Polymerization Stability

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Solution Overview

Problem

Existing control systems for gas-phase polymerization processes struggle with responsiveness and variability, leading to suboptimal performance and difficulty in maintaining process stability and efficiency.

Innovation Solution

A coordinated control system utilizing nonlinear dynamic models and predictive controllers that incorporate measured disturbing variables to anticipate process dynamics, allowing for coordinated manipulation of primary and secondary manipulated variables to achieve control objectives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If traditional control systems are used for gas-phase polymerization processes, then the system structure is simple, but the responsiveness and variability control are insufficient

Engineering Contradiction:
ImproveresponsivenessVSAvoidcontrol system complexity
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The control system is segmented into multiple independent nonlinear dynamic models, each responsible for specific process variables. This segmentation allows each model to specialize in predicting particular aspects of process behavior, improving overall responsiveness while maintaining manageable complexity through modular architecture

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system performs preliminary action by using projection values to predict future states of disturbing variables before they actually affect the process. This anticipatory approach allows the control system to prepare corrective actions in advance, significantly improving responsiveness to process changes

Inventive Principle:
Principle #10Preliminary action

2Reliability

If traditional control systems are used, then the device complexity is low, but the process stability and efficiency are suboptimal

Engineering Contradiction:
Improveprocess stabilityVSAvoidcontrol system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The control system implements comprehensive feedback mechanisms where actual process variables are continuously compared with predicted values from nonlinear dynamic models. This feedback loop enables real-time adjustments to maintain process stability, with the complexity justified by the significant improvement in reliability and consistency of polymerization outcomes

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts control parameters based on predicted process states and actual measurements. By continuously optimizing manipulation variables according to nonlinear model predictions, the system achieves superior process stability and efficiency, with the added complexity enabling precise parameter management

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If measured disturbing variables are incorporated into nonlinear dynamic models, then the control precision is improved, but the computational complexity increases

Engineering Contradiction:
Improvecontrol precisionVSAvoidcomputational complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system applies partial action by selectively incorporating only the most significant disturbing variables into the nonlinear dynamic models. This approach achieves sufficient control precision for critical process variables without the computational burden of modeling every possible disturbance, balancing precision with manageable complexity

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentEP3918427B1Process control
Publication Date: 2025.10.15 DOW GLOBAL TECHNOLOGIES LLC
  • EP3918427B1 patent drawingFigure 1
  • EP3918427B1 patent drawingFigure 2
  • EP3918427B1 patent drawingFigure 3

AI summary

Coordinated control systems and methods of controlling an actual process are provided. The coordinated control systems and methods of controlling an actual process utilize a nonlinear dynamic model, where measured disturbing variables are incorporated into the nonlinear dynamic model, and predictive controller calculations.