Tuesday, July 26, 2011

Process Control Software Design





Imprison all kind of design choices during the process of development needs a variety of notations, each of them representing a certain point of view. Usually, three views are chosen to explain the functionality, the structure and behavior of a software design.

The functionality designates the what-to-do in the system to be planned, and might be stand for with the notations of functional-oriented, for example SA-RT, SADT, or charts of activity in a decayed hierarchical tree structure. The hierarchy of activity together with the flow of information comprises the view of functional.

The behavioral view indicates the dynamics of the system that is to declare when and in reaction to what event the activities are activated. The behavior could be stand for with state charts, a variety of types of Petri nets, or the temporal logic of formalized. The view of structural offers a hierarchical disintegration into the modules and the communication between them. Generally, those modules correspond to a natural mapping from actually existing objects, for example network nodes, devices, and the subsystems of manufacturing. In current research on official modeling, started to merge the modeling of real-time and plan with the formalism of object-oriented. Similarly, Douglass expanded the Unified Modeling Language with the techniques of instantaneous description. Stewart et al. built up a port-based model focusing on the real-time control systems of structural design.

The notations of visual modeling are vital to communicate design decisions and design ideas. They also assist to assign the design parameters and the functional requirements. In this article, it is utilizing state charts to explain the behavior and module-charts, which are identical to those projected to point out the structure of system. The state charts as well as module-charts are layering and orthogonal, independent state or module regions. Consequently, both notations are helpful for a design process of hierarchical decomposable. A module chart is at all times attended with a state chart. In all-purpose, the models of state transitions are beneficial because they support straight a cognitive mapping from the requirements of functional to design parameter, here into states. Additionally, the models of state transition may handle dependent behavior in a way of natural. As a third notation, the charts of ladder logic are applied to explicitly identify the conjunctions of Boolean between incoming events. Although the ladder logic could be observed as a redundant description to state charts, it will re-evaluate it because of its high approval in industry.

The Design Process Steps
The important design steps are summarized as following. Step 1 and 2 according to the manufacturing system design process, while step 3 and 4 specify the procedure of mapping from domain of the CSD-FR to the CSD-DP.

Step 1a. Make the MSD-FR and MSD-DP module architecture:
The modular architecture of manufacturing system specifies the devices to be monitored. The architecture of modular is not accessible a structural breakdown of the system shows the components dynamic.

Step 1b. The system structural decomposition to be managed:
The recognized physical components structural decomposition increases elementary functional actors or modules. I/O ports are employed to identify the margin of each module. They designate the flow of data between functional units and refer to the event/sensor of incoming or event/actuator of outgoing signals.

Step 2. Make an ontology to recognize the task-neutral system’s behavior of MSD-DP:
Identify an appropriate set of task-neutral visible states, in which the controlled system of manufacturing could be. By this means, the ontology about the system controlled is produced. The states of system are a disjoint states set of system components to be controlled, for example rotary actuators, gripper, linear drives, and shuttle.

Step 3. Categorize task-oriented CSD-FR and understand them into states transition of CSD-D):
Categorize the preferred high-level functional specifications on highest level and understand them into states transition. For example CSD-FRx = move pat bin from A to B with CSD-DPx = move state. Each recognized module has predefined high-level states, for example recovering state, Initializing state, on/off-state, requesting state, etc.

Step 4. Decomposition behavioral:
State charts support the decomposition of behavioral visually. The CSD-FRs describes the planned activities and controls that will be together with this within states of CSD-DPs. The activities and states of subordinate are recognized throughout a zigzagging procedure between the domains of CSD-DP and CSD-FR. A state is always attended by a triggering event and an action of internal or external. An action of external control makes a state or motion change of the system of manufacturing.

Step 5. Decouple of the design:
Customized design matrices, indicated as tables of state transition, have been built to model and examine the modules and states interdependencies. The decoupling process separates the design into a structure of software with modules having fewer communication of inter-modular, but high interaction of intra-modular. Additionally, openly modeling the modules and states interdependencies increases the design robustness. The procedure of decoupling helps to find a stable states set of among the frequently many possible the control system states.



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