ARCHITECTURAL STYLES - 3

InterpretersProcess Control

Other Architectures

Dr Reeja S RProfessorCSE Dept

SJEC, Vamanjoor, Mangalore

INTERPRETERSSuitable for applications in which the most appropriate language or machine for executing the solution is not directly available

Interpreter

An interpreter takes a program written in one language and interprets it to another language

Interpreter

Interpreter

An interpreter has 4 Components: “Program” being executed and its data Interpretation engine and its state

Connectors procedure calls and shared state.

Interpreter Examples

Programming Language Compilers: Java, Smalltalk

Rule Based Systems: Prolog, Coral Scripting Languages: Awk, Perl

PROCESS CONTROL ARCHITECTURAL STYLE

Terminologies Process variable – measurable property in the

process. Controlled variable – the process variable

whose value, the system has to control Set point – the desired value for controlled

variable Manipulated variable - the process variable

that in changed in order to keep the controlled variable at the set point

In a water tank, if the level of water (controlled variable) is not up to the mark (set point), then increase flow of water (manipulated variable)

Process Control

The purpose of a process control system is to maintain specified

properties of outputs (controlled variables) of the process at the given

reference values (set points)

Types of Process Control loops

1. Open Loop2. Closed Loop / Feedback

loop3. Feed Forward loop

Open Loop Control - Process runs without surveillance

An open-loop system is expected to faithfully follow its input command or set point regardless of the final result

Open Loop Control

This is an open loop system because, system does not monitor or measure the temperature of the output air to see if it is heated to the desired temperature

Closed Loop Control Closed-loop systems are designed to automatically achieve

and maintain the desired output condition by comparing it with the actual condition.

Feedback Loop

Feed forward Loop

It anticipates future effects on the controlled variable by measuring other process variables and adjusts the process based on these variables.

Feedback Vs Feedforward

Car's cruise-control system that maintains speed of the car even in varying terrains

If it has feedback control, when there is a slope and therefore a speed

reduction, the feedback controller would compensate by applying

additional throttle to the engine.

If it uses a feed-forward controller instead, the controller would calculate

the slope beforehand and throttle the engine before any speed reduction occurs. In this sense, the controller predicts the incoming deviation and compensates for it.

Feed forward Loop

It anticipates future effects on the controlled variable by measuring other process variables and adjusts the process based on these variables.

Other Familiar architectures Distributed processes

Other Familiar architectures

Main Program/ Sub-routine Centralized control, sequential execution in some order

Other Familiar architectures

Domain specific architectures Organizational structure tailored for a family

of applications such as avionics, command and control, vehicle-management, etc

Other Familiar architectures

State transition systems Applicable for Reactive systems