Variable Trajectory Sharing for Multi-Controller Process Control
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Solution Overview
Problem
In control systems with multiple controllers, differing trajectory forecasts for common process variables due to varying constraints make effective control challenging, leading to difficulties in implementing control actions.
Innovation Solution
A technique for sharing predicted desired variable trajectories between multiple controllers, where one controller is designated as dominant to prioritize control, allowing only the dominant controller to write the shared manipulated variable set point, ensuring that constraints are honored and control objectives are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple controllers independently predict trajectories for common process variables, then each controller can optimize for its specific constraints and objectives, but conflicting trajectories arise making effective control difficult
Solution Approach 1:
A trajectory sharing mechanism acts as an intermediary between multiple controllers. Each controller predicts its desired trajectory for common process variables, shares these predictions with other controllers, and adjusts its control actions based on received trajectories. This mediator approach allows controllers to maintain independence while coordinating their actions to avoid conflicts.
Solution Approach 2:
Controllers continuously exchange trajectory information and adjust their predictions based on feedback from other controllers. When a controller receives a trajectory from another controller for a common variable it also controls, it incorporates this information into its own trajectory prediction, creating a feedback loop that resolves conflicts while preserving each controller's ability to optimize for its specific constraints.
2Reliability
If controllers share trajectory information, then control coordination improves, but system complexity increases
Solution Approach 1:
The trajectory sharing mechanism is implemented as a modular addition to existing controllers rather than a complete system redesign. Each controller maintains its independent prediction capability while adding a sharing and coordination layer. This segmentation allows the system to gain coordination benefits without requiring complete inter-controller integration, thus limiting complexity growth.
Solution Approach 2:
The trajectory sharing mechanism serves multiple functions simultaneously: it enables conflict detection, facilitates coordination, preserves controller independence, and maintains individual optimization capabilities. This multi-functionality means that a single added component achieves multiple objectives, reducing the overall complexity that would result from implementing separate mechanisms for each function.
Data Source
AI summary
One or more techniques are provided for the sharing of variable trajectories between multiple controllers in a control system. In general, the present technique is based upon the sharing of predicted desired variable trajectories between multiple controllers requiring a common input variable. In one embodiment, a common input variable is shared between two controllers, wherein one controller is tuned to have dominant control with regard to the shared variable. Each controller determines and communicates their own desired trajectory for the shared variable to the other controller and in doing so, the constraints associated with each controller are shared and honored by the other controller. Based on the communicated trajectories, the dominant controller may exercise control over the shared variable, thus improving overall process control.