Process Optimization Using Slack Variables and Simulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing process control systems face challenges in optimizing industrial processes due to limitations in model predictive control (MPC) implementations, particularly when dealing with multiple input/multiple output control strategies, as they often fail to provide solutions outside predefined ranges and limits, and lack flexibility in handling constraints effectively.
Innovation Solution
A system and method that utilizes simulated process outputs from concurrent simulation to develop target values for optimization, incorporating slack variables to extend the search range beyond primary constraint variables, allowing for optimal solutions within any process condition, and employing multi-objective linear programming optimization techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If model predictive control (MPC) is used for optimization, then control performance is improved, but the system fails to provide solutions outside predefined ranges and limits
Solution Approach 1:
The patent transforms the static optimization problem into a dynamic one by introducing a moving horizon approach. The optimizer continuously updates the search range based on current process conditions and measured inputs, allowing the solution space to adapt dynamically rather than being constrained by fixed predefined ranges. This enables the system to provide solutions outside traditional limits while maintaining control performance.
Solution Approach 2:
The patent changes the parameters of the optimization problem by incorporating slack variables that modify the constraint boundaries. These slack variables allow the optimizer to temporarily violate predefined ranges and limits when beneficial, then correct deviations. This parameter transformation enables flexible adaptation while preserving the core control objectives.
2Device complexity
If conventional optimization methods are used, then computational simplicity is maintained, but flexibility in handling constraints is insufficient
Solution Approach 1:
The patent introduces slack variables as intermediary elements between the optimizer and the process constraints. These slack variables act as buffers that absorb constraint violations, allowing the optimizer to explore a broader solution space without directly violating hard constraints. This intermediary mechanism provides flexibility in handling constraints while maintaining computational tractability through standard optimization algorithms.
Solution Approach 2:
The patent extends the optimization problem into an additional dimension by incorporating slack variables that represent constraint violation margins. This dimensional extension transforms the problem from a constrained optimization in n-dimensions to an unconstrained (or softly constrained) optimization in n+1 dimensions, providing greater flexibility while maintaining computational simplicity through established mathematical programming techniques.
3Reliability
If predefined ranges and limits are strictly enforced, then safety and operational constraints are satisfied, but optimal solutions may be missed
Solution Approach 1:
The patent applies beforehand cushioning by introducing slack variables that anticipate and buffer constraint violations before they occur. These slack variables create a cushioning layer between the optimizer and hard constraints, allowing the system to explore solutions that temporarily exceed predefined ranges while ensuring that actual process constraints are never violated. This approach prevents suboptimal solutions caused by overly restrictive constraint enforcement.
Solution Approach 2:
The patent employs partial or excessive action by allowing the optimizer to temporarily exceed predefined ranges and limits through slack variables. Rather than strictly enforcing constraints at all times, the system permits controlled excesses when beneficial for optimization, then corrects deviations. This partial relaxation of constraints enables discovery of superior solutions while maintaining overall constraint satisfaction through feedback control.
Data Source
AI summary
A system and method for controlling a process includes simulating the process and producing a simulated output of the process, developing a set of target values based on measured inputs from the process and based on the simulated output from the process simulator, and producing multiple control outputs configured to control the process based on the set of target values during each operational cycle of the process control system. The simulated outputs include one or more predicted future values up to the steady state of the process.


