Simulation & Modelling

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Simulation & Simulation & Modelling Modelling Systems Engineering Training Systems Engineering Training Programme for DRDO Scientists at Programme for DRDO Scientists at IAT, Pune IAT, Pune 2 2 nd nd July 2003 July 2003 Lecture-2: Simulation Types, Tools Lecture-2: Simulation Types, Tools and Simulators and Simulators

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Simulation & Modelling. Lecture-2: Simulation Types, Tools and Simulators. Systems Engineering Training Programme for DRDO Scientists at IAT, Pune 2 nd July 2003. Lecture Outline. Software Simulation & Languages Concept of a Simulator. Engineering Simulators. - PowerPoint PPT Presentation

Transcript of Simulation & Modelling

Simulation & ModellingSimulation & Modelling

Systems Engineering Training Programme for DRDO Systems Engineering Training Programme for DRDO Scientists at IAT, PuneScientists at IAT, Pune

22ndnd July 2003 July 2003

Lecture-2: Simulation Types, Tools and SimulatorsLecture-2: Simulation Types, Tools and Simulators

Lecture Outline

• Software Simulation & Languages

• Concept of a Simulator.

• Engineering Simulators.

• Basic Philosophy of Simulator Building

• Examples of Software Simulators.

• Examples of Hardware Based Simulators.

Why Software Simulation?

– Software simulation is usually a low cost, quick turn-around time option for most of the design cycles.

– Ability to solve complex mathematical equations (e.g. CFD) enhances the utility of software simulation to the design & development process.

– Availability of fast and powerful digital computers have rendered software simulation quite popular.

– Pure software simulations can come fairly close to real system, as an aid in crucial decision making.

What is Software Simulation?

– Software simulation pertains to solution of a purely mathematical model.

– Software simulation generates system response to inputs, without actual product realization.

– In involves writing a program that is executed on a computer, to create the ‘real’ situation.

– Software simulations can be both “Offline” as well as “real-time” simulation.

Software Simulation Tools

– Software simulation is carried out by programming a digital computer suitably.

– Programming is usually carried out in a higher level language, either general purpose or special purpose.

– Extensive graphic support is needed to set up a software simulation.

– Operating System also plays an important role in setting up a software simulation.

Software Simulation Languages

– General purpose simulation languages are usually not designed for specific needs of simulation.

– FORTRAN, C, C++ etc. are examples of such general purpose languages which can be used for setting up a software simulation.

– These are designed for many different applications and programming effort, to create a specific simulation, can be quite large.

– However, these are highly portable across different computer hardware, Operating System & Compiler, resulting in cost-effective simulations.

Software Simulation Languages

– Special purpose simulation languages are designed keeping in mind, specific needs of simulation.

– These contain a library of pre-defined macros (or “tools”) which minimize overall programming effort.

– CSMP is a popular language for continuous system simulation.

– For discrete system models, GPSS, SIMLIB, ALGOL, SIMSCRIPT II, SIMULA, etc. are used.

– Non-portability is usually the main drawback for these special purpose language, making them costly.

Software Simulation Languages

– Another class of languages, called symbolic language, also find use in setting up simulations.

– These provide a library of mathematical functions which can be put together to create a simulation.

– MATLAB is one such symbolic language that has acquired significant popularity as a simulation language, mainly because of programming simplicity.

– Provision of a variety of tool boxes in MATLAB has made it applicable to a large set of Engg. problems.

Software Simulation in CSMP

Y = INTGRL(IC,x), Y(0) = IC

Y = LIMIT(P1,P2,x)

Y=STEP(P)

Y = EXP(x)

Y = ABS(x)

Y = ALOG(x)

Y = SIN(x)

Y = COS(x)

Y = SQRT(x)

Y = AMAX1(x1, x2, …, xn)

Y = AMIN1(x1, x2, …, xn)

INCON – Initial Conditions

CONST – Constant

PARAM – Parameter

TIMER – Time Interval

PRINT – Printing Variables

PRTPLT – Plotting Data

TITLE – Output Heading

LABEL – Intermediate Headings

END – End of Program

ENDJOB – Task Completion

CSMP provides for following macros.

Example of CSMP Code

• Suspension System - (Step Response)

M

K D

F

X

TITLE SUSPENSION SYSTEM

PARAM D = (5.56,16.9,39.5,56.5)

X2DOT = (1.0/M)*(K*F – K*X – D*XDOT)

XDOT = INTGRL(0.0,X2DOT)

X = INTGRL(0.0,XDOT)

CONST M = 2.0, F = 1.0, K = 400.0

TIMER DELT=0.005, FINTIM=1.5,

PRDEL=0.05, OUTDEL=0.05

PRINT X, XDOT, X2DOT

PRTPLT X

LABEL DISPLACE. VS. TIME

END

STOP

Software Simulation in SIMULINK

Discrete: Unit Delay, Integrator, 0 Order Hold, 1st Order Hold, DTF, DSS, Dfilter, Dzero-Pole

Sources: Constant, Signal Generator, Step, Sine, Chirp, Clock, File, Random No.

Linear: Gain, Sum, Integrator, TFunction, State-Space, Zero-Pole, Derivative, Dot Product

Tool Boxes: Communication, DSP, Control, Fuzzy, System ID, NNET, StateFlow, NCD

Connections: In, Out, Mux, Demux, From, Goto, Data Store/Read, Memory, Enable, Trigger, Ground, Terminator, IC, Subsystem, Selector, Width

Nonlinear: Abs, Math, Trig., Floor, MinMax, Product, Logic, Relation, Sign, Rate Limit, Saturation, Function, …. Etc.

Sinks: Scope, X-Y Graph, Display, File, Stop

SIMULINK provides following functional groups.

Example of SIMULINK Model

• Suspension System - (Step Response)

M

K D

F

X 1

s +2.845s+2002

Transfer FcnStep Scope

Simulation in FORTRAN or C

• Suspension System - (Step Response)

M

K D

F

X

Main Program

Data Structures

Data Communication Strategy

Integration Subroutine

Plotting Subroutine

Flight Simulation

– Flight simulation pertains to solution and visualization of controlled aircraft motion.

– There are many levels at which flight simulation is performed, depending on the need.

– At the lowest end, we have “Design Simulation”, which is a purely mathematical exercise. It contains highly idealized sub-system models.

– Next, is the Engineering Simulator, in which more accurate and detailed models of many sub-systems are available. However, no hardware is included.

Flight Simulation

– “Iron Bird” simulation is the next level of flight simulation wherein a majority of sub-system hardware, excepting aircraft, are integrated with software models.

– “Pilot-in-Loop” simulation caters for man-machine interface development and is usually carried out at number of stages.

– In-Flight simulation is a technique used to check out new sub-system designs (especially Control Laws) on an existing proven aircraft.

– Ground based Real Time Simulation, on a motion platform, is closest to “Flight Simulation” .

Summary of Software Simulation

– Software simulation is a design tool that needs to be configured based on specific needs.

– Computer, Operating System and Languages play an important role in software based simulations.

– Simulator is the system that is capable of performing simulations as per the need.

– Next part of lecture deals with simulator related issues.