Frequently Asked Questions
Q. What is Integrated Modeling?
A. Integrated
Modeling is a Multidisciplinary Modeling approach that assembles
disparate physical process models into an "all-up" model representing
the coupled dynamics. The general approach is to develop Linear Time
Invariant (LTI) models of each process, including the input/output
relationships at process interfaces. The LTI models are then
automatically coupled using linear algebra.
Q. Can nonlinearities be handled within the
framework?
A.Theoretically, arbitrary nonlinear functions
of time, inputs, and state trajectories can be accommodated by
the DOCS parameter-varying model. To date, development activities
have concentrated on linear and time invariant parameters
(such as moduli which do not change over the timescale of the
dynamics). However, many types of spacially localized nonlinearities,
for example angles of revolute joints, can be analyzed
in arbitrary domains. Furthermore, time domain implementations of
many performance objective functions (with gradients)
are available within DOCS, so many types of nonlinearities can be
analyzed using external simulation tools.
Q. What problem sizes can DOCS accommodate?
A.
From its inception, DOCS was designed for applicability to present
and future real-world design needs. DOCS tools were designed and optimzed
for large problem sizes. A set of test problems, representative
of current space-based observatory missions in terms of the number
of states, inputs, outputs,
and parameters, was used to benchmark and refine the DOCS toolset.
There is no inherent limit within DOCS on the size of the
structural Finite Element model, in terms of number of nodes. The
relevant quantities are the number of modes in the frequency range
of interest, the number of disturbance inputs, and the number
of performance outputs. DOCS has been successfully applied to
systems with 2000+ modes, 36 disturbance inputs, and 600+ outputs
representing optical pointing and wavefront error.
Q. What structural modeling tools does DOCS interface
to?
A.DOCS can synthesize structural models from
any Normal Modes solution sequence.
For NASTRAN users, DOCS supplies a very complete set of tools for
importing, modifying, and writing bulk data decks.
The NASTRAN interface also allows the user to specify structural
parameter dependencies in terms of entity name and ID. DOCS
automatically assembles the parameter-varying model without
further user intervention. DOCS can support physical
parameter-varying models under other structural modeling packages,
through a user-provided interface that conforms to the
documented DOCS syntax.
Q. Does DOCS require any MATLAB® toolboxes?
A.No. DOCS is a set of standalone routines that
does not require any additional toolboxes to
function. DOCS provides routines to convert between DOCS and the
Control Systems Toolbox, so that users who have access to the Control
Design Toolbox can synthesize and analyze controllers in that
environment. DOCS also provides an interface to Simulink so that
users can define the Integrated Model graphically within Simulink.
Q. What platforms are supported?
A.Currently only Windows is supported. A
Linux port of DOCS is under development.
