Page 266 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes languages. Following a brief introduction to very high level languages, design principles for
continuous system simulation languages are presented. These principles are illustrated by
examples from the Continuous System Modelling Program (CSMP) and the Partial Differential
Equation Language (PDEL). A typical program in each language is included. Batch and interactive
implementation techniques for continuous system simulation languages are discussed. The
classical batch implementation technique is to provide a preprocessor which translates the
simulation language into an algorithmic language such as FORTRAN or PL/1. The PL/1
preprocessor is described as a useful language for the implementation of very high level language
translators. The final section of the paper presents an interactive implementation technique
which interfaces a batch program processor to interactive graphics display and updating routines.
In this manner, efficient simulation code is interfaced to flexible interaction routines.

Did u know? What is batch processor?
The batch processor is preserved intact, thus requiring only one implementation of the
language for both batch and interactive applications.

Currently available Continuous System Simulation Languages (CSSLs) are sensibly effective in
providing a more user-oriented interface to the computer. However, the fact that CSSLs represent
a tool and not a panacea has not always been kept in perspective. Operational problems have
hindered the use and consequent improvement of the languages. Designers and implementers
must be willing to stay in the loop and smooth out the operational interface for the users. The
future for CSSL is very bright. The increasing use and importance of remote, interactive terminals
is based on the same user-problem approach that is the foundation of CSSL. It is in this area that
CSSL will probably be most effective and will experience broad acceptance by new users.

It is distinguished as one of the first uses ever put to computers, dating back to the Eniac in 1946.
Continuous simulation allows prediction of rocket trajectories, hydrogen bomb dynamics (N.B.
this is the first use ever put to the Eniac), electric circuit simulation, and robotics. Established in
1952, The Society for Modeling & Simulation (SCS) is a nonprofit, volunteer-driven corporation
dedicated to advancing the use of modeling & simulation to solve real-world problems. Their
first publication strongly suggested that the Navy was wasting a lot of money through the
inconclusive flight-testing of missiles, but that the Simulation Council’s analog computer could
provide better information through the simulation of flights. Since that time continuous
simulation has been proven invaluable in military and private endeavors with complex systems.
No Apollo moon shot would have been possible without it.
Modern Applications

Continuous simulation is establish inside Wii stations, commercial flight simulators, jet plane
auto pilots, and advanced engineering design tools. Indeed, much of modern technology that
we enjoy today (along with technology that can destroy the planet) would not be possible
without continuous simulation.

Mathematical Theory

In continuous simulation, the continuous time response of a physical system is modeled with
ODEs.Newton’s 2nd law, F = ma, is a good instance of a single ODE continuous system. Numerical
integration methods such as Runge Kutta, or Bulirsch-Stoer are used to solve the system of
ODEs. By coupling the ODE solver with other numerical operators and methods a continuous
simulator can be used to model many different physical phenomena such as flight dynamics,
robotics, automotive suspensions, hydraulics, electric power, electric motors, human respiration,

260 LOVELY PROFESSIONAL UNIVERSITY