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Assessment and Future Directions of Nonlinear Model Predictive ...

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A <strong>Nonlinear</strong> <strong>Model</strong> <strong>Predictive</strong> Control Framework as Free S<strong>of</strong>tware 231Fig. 1. newcon Component diagrammedium companies is not to replace existing systems <strong>and</strong> components, but ratherto build upon them.The conceptual design <strong>of</strong> newcon (Figure 1) incorporates several moduleswith distinct features.The Controller block contains code necessary for the control problem formulation(as described in Section 2.1) <strong>and</strong> interface routines to an ODE <strong>and</strong> a QPsolvers. Besides, in order to reduce the communication overhead, the systemmodel also makes part <strong>of</strong> this module. Moreover, an Estimator component maybe used to update the model states <strong>and</strong> parameters, hence reducing model-plantmismatch.The purpose <strong>of</strong> the Data exchange <strong>and</strong> synchronization component is to providethe means for consistent dataflows <strong>and</strong> to ensure correct timing in theoverall system. This is achieved by the use <strong>of</strong> POSIX shared memory <strong>and</strong> synchronizationmechanisms. Alternatively, when the timing requirements are notstrict, this module may be based on a database engine.The function <strong>of</strong> the Communications block is to interface newcon to theexisting regulatory control system <strong>of</strong> the plant using open industrial communicationprotocols. Because <strong>of</strong> the widespread use <strong>and</strong> low cost <strong>of</strong> the hardware,open TCP/IP based protocols running over Ethernet hardware will be favored.This module may implement capabilities/protocols necessary in a particular application,adding to the flexibility <strong>of</strong> the overall system <strong>and</strong> reducing its size.The measurements <strong>of</strong> the plant, the controller states, setpoints, outputs, performanceindices, as well as other relevant information is recorded by the loggermodule. This module currently supports data saving in plain format in severaltext datafiles. Its functionality will be exp<strong>and</strong>ed to include database support.The graphical user interface (GUI) module provides a user friendly way tocontrol the system, to monitor graphically important variable trends <strong>and</strong> performanceindicators. In order to distribute computing resources evenly, <strong>and</strong> to

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