MMC is easy to design and tune.
MMC is a model-based controller. Each PV-CO relationship is modeled as a first order lag plus deadtime. One single tuning parameter (fast or medium or slow speed) is required for each PV-CO loop. Process variables are caused to track desired trajectories.
MMC is structurally robust.
Any control loop can be put on manual without loss of performance of the rest of the control system. This feature is difficult to achieve using centralized multivariable control systems.
MMC is flexible.
Coordinated Controller and Modular Multivariable Controller blocks can be assembled in various configurations to meet specific control objectives.
The control outputs are coordinated.
The order in which the control outputs are used to compensate for a process variable deviation from its setpoint can be specified.
MMC control of a heavy oil fractionator.
Top draw rate (CO1) is used to control top end concentration (PV1).
Side draw rate (CO2) controls side end concentration (PV2).
Bottoms reflux duty (CO3) has its target value.
CO1 hits the low constraint (Time~100) due to the change in setpoint of PV1 (SP1).
CO3 is used to compensate for PV1 deviation from the setpoint during the transient period.
After the transient period and change in setpoint of PV2 (SP2), the value of CO1 increases and CO3 can be driven to its target value.
Heavy Oil Fractionator
MMC maintains a selected control output at its target value.
Two control outputs maintain two process variables at their respective setpoints while the third control output is driven to its user-specified target value. Control output target values can be changed without disturbing process variables. The control output target value can result from a process optimization criterion or an economic criterion.
MMC accounts for the relative importance of process variables.
One process variable is considered more important than the other, and is maintained at its setpoint with highest priority. With all three control outputs available, there are three goals you can accomplish in the following order of importance:
- Maintain one process variable at its setpoint with higher priority
- Maintain second process variable at its setpoint with lower priority
- Maintain a selected control output at its target value
MMC handles control output and process variable constraints.
In order to improve performance of the MMC, you can enter constraints on all control outputs and process variables, and can also feed back to the controller the control outputs that were actually applied to the process.
MMC software is easy to maintain.
The MMC code is relatively short. The algorithm uses our Coordinated Controller (CC) 1xN code according to the controller configuration. The MMC procedure is easy to understand and maintain.
The Modular Multivariable Controller (MMC)
Economic Benefits of the MMC
We provide the Modular Multivariable Controller with comprehensive technical description and user manual. We describe step-by-step procedures for design and tuning. The controllers can be downloaded to your existing platform. Consulting is available.
Our model predictive controller toolkit offers solutions to basic multivariable 1x2, 1x3, 2x2, 2x3 and other controller design configurations according to your needs. The controllers can be used for split range control problems, boiler control, distillation column control, constraint control, and many other control applications. The controllers are available in FORTRAN, C-language, Bailey User Defined Functions (UDF), Honeywell Control Language and other platforms.
The Modular Multivariable Control (MMC) and the Coordinated Control (CC) are patented technologies by ControlSoft, Inc., Cleveland, Ohio.
The Modular Multivariable Control technology was developed by process control experts Doctors Coleman Brosilow, Irving Lefkowitz and Tien-Li Chia.
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