Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

Chapter 8 / Simulation
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8.5 Internal Data Communication between Software Modules
Communication between modules, other than utilities, is performed using a
global pool of variables, the “global common block (GCB). These data are
defined in isolated code segments, compiled into the relevant modules using
the INCLUDE statement, and include variable definitions, scaling factors
and units used for automated I/O. The major program variables required for
data logging and windows display are contained in the GCB defined in code
segment COMMON.FTN. Here variables are mapped to a location in a 64
bit real vector, or a 32 bit integer vector. Logical and character types are not
supported since they require conversion for automated I/O purposes. This
code segment also contains an initialisation flag, typed utility functions,
work variables, vectors and matrices that are available for local use in each
module containing it. Data is automatically “SAVED” between invocations.
The use of a GCB, contrary to the usual software ethos based on argument
lists, was adopted to promote:
• Rapid software development
• Consistent use of unique variable names and units
• Use of general plotting, printing and data management facilities
• Interactively changing variables prior to, and during, execution
• Interactive parameter browsing and plotting facilities
Supporting the GCB are subsidiary common blocks dealing with data
transfer between modules comprising localised functionality, or parameters
that are not required for data logging, or windows visualisation. These
additional common blocks have the extension “*.FTN”, their purpose being:
• COMAER: Missile aerodynamics and their derivatives
• COMCNG: User defined in-run change data
• COMGEN: Transformation matrices, random seeds, etc.
• COMGPS: GPS sensor local common block
• COMMAP: DLMS map data
• COMOPT: Missile trajectory optimisation data
• COMSFF: Tracking and Missile Observer data
• COMTWF: Target wire frame model data
• COMWIN: FORTRAN / C++ interface data
• PRIPLO: Automated printing and plotting data
Where practicable these files contain data structures identical to those used
in the GCB to facilitate transfer between them as designs evolve.
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