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More agile tools are helping multivariable control become more effective for advanced process control and other applications than traditional model-based control (MPC) and real-time optimization. Learn where the matrix can help.
KEYWORDS: Matrix, advanced process control (APC)
Learn about a controller's (single-loop or multivariable) connections and directions.
Review theoretical vs. operational matrix design and design tips for all process interactions.
Examine an APC example of fired heater control.
The dominant aspect of process control activity for the next couple of decades will (most likely) be multivariable control. This is the next logical step in process automation progress. Better tools are making advanced process control (APC) methods available to more applications.
After several decades of multivariable control activity, the conventional multivariable control paradigm - model-based control (MPC) and real-time optimization - has never evolved into the multivariable control core-competency the process industry needs. It is evident much work remains to be done ("APCs missing metric") and more agile tools are needed to do it ("Multivariable control as core-competency")
A modern multivariable control paradigm will combine enduring single-loop process control principles that pre-date the MPC era with key multi-variable control lessons that have emerged from the MPC era (Table 1). The surviving core multivariable control principles and lessons will be important to know for control engineers. Chief among them is the concept of the matrix for its role in multivariable control, and also for its role in the bigger picture of effective process operation, constraint management, and process optimization.
APCconnections, directions
The first things to know about any controller, whether single-loop or multivariable, are its connections and directions.
In single-loop control, "connections" refers to which transmitter (or other process measurement) and which valve (or other final control element) are connected to the controller. These are often shown on piping and instrument drawings (P&IDs), control system graphics, and in many other types of process documentation. Each context may include additional controller details, but a controller's connections are always the minimum information necessary to grasp the role of the controller at a glance, that is, which variable is being controlled by which valve (or by which "handle").
A matrix diagram provides the same information for a multivariable controller (Figure 1). It shows which manipulated variables (MVs) are connected...