Applying Distributed Systems concepts to SCADA

By

Padmanabha Kamath.

SCADA and its uses

SCADA stands for Supervisory Control and Data Acquisition.Most commonly used in- Manufacturing industry - Critical areas like missile control- Quality control - Material distributionAn invaluable ( and indispensable ) tool for control systems of any nature.

SCADA – The hardware architecture

SCADA – The software architecture

Communication concepts in SCADA systems

Client – server based . Algorithm used is the “publish – subscribe” algorithm.Central servers collect, analyze and present data to displays and to other servers.Important interfaces - Human – Machine Interface - Machine-device interface.Real – time communication is of the utmost importance.

Framework for SCADA systems analysis

Major vendors for SCADA systems - Wonderware Inc.- Intellution Inc.- National Instruments.Some of the items provided by these vendors are

- Device handling. - Alarm Handling and reporting. - Data Archiving/Trending. - User Interface building tools.

General architecture (object – oriented approach)

Abstract Behavior Modeling for SCADA systems

Main Requirements A transparent communication system (location

transparency). Modeling the control system. Visualizing the whole system. Easy access to data (Interchangeable data

formats). Redundancy and real time monitoring( Performance

transparency).

Distributed systems issues handled by DIM/SMI++

Handled by DIM Location Transparency. Easy visualization of servers/clients/resources. Performance Transparency.Handled by SMI++ Modeling of the control system. Framework for simulation. Support for files produced using the SML language.

DIM framework class diagram

Valve Valve

Pump

Sensor

Tank

A Simple control system

Domain representation in SMLobject:PUMP

state:OFF

action:ERROR

do CLOSE_VALVE VALVE

terminate_action/state = OFF

action:OK

do SENSOR_CLOSE SENSOR

terminate_action/state = OFF

SMI++/DIM implementationModeling the DELPHI (DEtector with Lepton,Photon and Hadron Identification) experiment at CERN Switzerland.The full system comprises about 1000SMI objects in 50 different domains and running on 40 machines.

What I learned

The SMI++ framework / SML language.Applying object – oriented concepts to control systems.Implementation of publisher-subscriber algorithm.Hope to model more detailed control systems with multiple domains.

Scope for improvements

To go beyond the framework and extend it.To model more complex control systems.To hack Xlib so that custom windows can be incorporated.To extend DIM so that it can support more complex file services and RPC.