哪位老大有关于DADS的资料？

playboy2618

偶想学DADS，可是没有资料，有哪位大哥帮帮小第，不胜感激。

robertyang

______________________________
*CADSI Senior Applications Engineer, 703-925-9743
†CADSI Applications Engineer, 319-626-6700
Copyright © 1997 by the American Institute of Aeronautics and Astronautics, Inc.
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American Institute of Aeronautics and Astronautics
CAD Embedded CAE Tools for Aircraft Designers
as Applied to Landing Gear
Matthew S. Schmidt,* Chris Paulson†
CADSI, Mid-Atlantic Region CADSI, Corporate
One Fountain Square 2651 Crosspark Road
11911 Freedom Dr., Suite 590 Coralville, IA 52241
Reston, VA 20190
ABSTRACT
In the aerospace community the
perception of quality no longer relates to only
whether the product performs to specification.
The perception now includes whether or not the
hardware was produced “on-time and on-cost”.
To live up to the expanding expectations and
maintain a competitive stance, design cycles
times have to be reduced to maintain sound
control on program costs and schedules. As the
continuous change occurs, traditional analytical
approaches are being scrutinized for streamlined
efficiency. When shown to be antiquated, new
approaches are adopted to rise to the challenge.
A major challenge has been to transform old
paradigms into new paradigms. Once such
change has been to remove the barriers between
disciplines and form product development teams
to encourage cross-pollination of engineering
activities. As part of the natural evolution of the
teams, CAE tools have to become embedded
within the CAD environment. This embedding
of tools tremendously reduces duplication of
effort, redundant data bases, amount of
coordination, and thereby program costs.
The foundation of the paper being
presented here is the application of CAD
embedded CAE tools. The “new paradigm” that
will be demonstrated by this paper is the
Simulation Driven Design (SDD) environment.
The application example that will be used is a
landing gear exposed to the following
environments: variable speed drop test and
retraction. The CAD tool that will be applied is
CATIA. CATIA provides a solid modeling
environment for designing components and
mechanical assemblies. The CAE tools that will
be applied are CATDADS, PolyFEM and
EASY5. CATDADS is a tool that is used to
predict the behavior of mechanical assemblies.
The equations of motion are automatically
formed and solved. Positions, velocities,
accelerations and reaction loads are predicted
for all components in the assembly. PolyFEM is
a finite element analysis package that includes
interfaces to CAD products, an automatic
mesher, and a p-type finite element solver.
EASY5 is a control design tool which
distinguishes itself from other tools on the
market by its hydraulics libraries. The
CAD/CAE tools are used in conjunction to
achieve the desired “total system prototype”
prior to any physical devices being constructed.
1.0 Introduction
The foundation of the paper being
presented here is the application of CAD
embedded CAE tools. The “new paradigm” that
will be demonstrated by this paper is the
Simulation Driven Design (SDD) environment.
SDD is a tool applied by designers, analysts and
system engineers alike. The SDD is the manner
in which the “total system prototype” is
achieved electronically within the CAD
environment prior to the development of any
physical apparatus. The “total system
prototype” operates on the CAD systems solids
and assembly database. The electronic
prototypes considered by the SDD are assembly,
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American Institute of Aeronautics and Astronautics
control/assembly and component. Integrating
tools with the CAD programs have been a move
in the right direction to improve efficiency and
reduce cost; however, to a large extent databases
are still being duplicated, too much training is
required to use the integrated products, and too
much non-value added activity is needed to
assist in each phase of the integration. SDD is
the embedding of the motion and structural
analysis tools into the design environment such
that CAD/CAE activities occur in parallel with
the same database. By embedding CAE tools
the results of the engineering process are
naturally available for upstream processing in
the CAD environment. Simply stated, SDD
allows the engineer to electronically prototype
during the design process ensuring that the final
product is the most efficient compromise
possible. Physical testing then becomes a tool
for final verification rather than a part of the
iterative design process.
The CAD tool that will be applied is
CATIA. CATIA provides a solid modeling
environment for designing components and
mechanical assemblies. The CAE tools that will
be applied are CATDADS, PolyFEM and
CATDADS/Plant EASY5. As part of the SDD,
the “look and feel” of the CAD package is
maintained by the menu items and functionality
of the CAE embedded tools. CATDADS
operates directly off of the CAD systems solids
and assembly database. The software is a tool
that is used to predict the behavior of a
mechanical assembly.1 Force elements such as
actuators, tires and controls can be added to the
assemblies within this tool. The equations of
motion are automatically formed and solved.
Positions, velocities, accelerations and reaction
loads are predicted for all components in the
assembly. The results are available for visual
animation and graphical plotting. PolyFEM is a
finite element analysis package that includes
interfaces to CAD products, an automatic
mesher, and a p-type finite element solver. 2
The software is design engineer oriented and
geometry based. EASY5 is a control design tool
which distinguishes itself from other tools on
the market by its hydraulics libraries. 3 The
control models are assembled from a variety of
components in hydraulics, mechanical, multiphase
fluid, pneumatic and thermal libraries.
The application example that will be
presented in this SDD paper is a landing gear
exposed to the following environments: variable
speed drop test and retraction. The paper will
demonstrate the application of CATDADS,
PolyFEM and CATDADS/Plant EASY5 (CAE
tools) while embedded within CATIA (CAD
tool). The CAE tools will be used to understand
the performance and requirements of the
landing gear without duplicating the CAD
database. Each phase required to go from the
CAD tool to each of the CAE tools as applied to
the landing gear will be demonstrated by this
paper without ever having to leave the CAD
environment. Above all else, this is critical
because any changes made to the system are
immediately available for upstream processing.
2.0 Total System Prototype
Figure 1 - Flowchart and Process for Applying SDD
CATIA CATDADS
PolyFEM
EASY5
additional
boundary
conditions
excitation
input
disturbance
input
Total System Prototype Control/Assembly Prototype
Component Prototype
Assembly Prototype
KINEMAT/
KINEMUSE
SOLIDE/
SOLIDM
CATIA FUNCTION CATIA FUNCTION
BRASSBOARD
TEST
Figure 1 shows the flowchart and
process for the application of SDD. CATIA is
shown to be the beginning and the end of the
SDD environment. The entire flowchart
represents a model for the “total system
prototype”. The overall prototype consists of an
assembly, control/assembly, and component
prototype. Each of the prototypes will be
presented in detail in subsequent sections. The
regions enclosed by dashed lines indicate subcategories
of the “total system prototype”. The
single lines connecting the boxes show the flow
of information from the CATIA database. The
double lines show the upstream processing path
for design modifications back to the design
database from each of the prototyping
categories. The core CATIA functions needed
for this prototyping environment are SOLIDE,
SOLIDM, KINEMAT and KINEMUSE. These
functions will be described in the next section.
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American Institute of Aeronautics and Astronautics
The strength of SDD is having the
CAE tools embedded inside of the CAD tools
such that a true “total system prototype” can be
achieved by allowing product development
teams (PDT) take full advantage of the design
database. SDD facilitates the mission of PDTs
by merging the system, design and analysis
databases. As the design modifications are
made, and due to the manner in which the tools
are embedded, the prototyping automatically
reflects the changes. Therefore, design trade
studies, performance assessments and complex
system behavior can be quickly and efficiently
investigated by the PDT without having to
depart from the CAD system.
3.0 CATIA
The prototyping components are
designed using CATIA exact and mock-up
solids (SOLIDE/SOLIDM). The exact solids
provide the precise geometric representation of
each part, while mock-up solids provide a
faceted geometric representation. The designed
parts are arranged into different sets. From a
mass and inertia point of view, all of the parts
within a CATIA set are rigidified such that the
composite characteristics are available to the
assembly prototyping. The KINEMAT function
allows the different geometric sets to be
connected by appropriate joint types. As the
boundary conditions are specified, ICONS
(indicate condition) appear on the assembly
indicating the joint location and type. The joints
allow articulation or relative motion to occur
between the geometric sets. The KINEMUSE
function allows prescribed motion to be superimposed
onto the sets which are kinematically
coupled. The bi-product of the solution is the
system motion in which part interference’s and
collisions can be checked. As a side note, the
output of a kinematic solution is purely related
to the position, velocity and acceleration of the
system components which results from
prescribed motion. It is believed that the reader
understands the fact that reaction loads are not a
bi-product of kinematic analysis.
Two types of kinematic sets can be
defined in KINEMAT: complete and incomplete
systems. A complete system is one in which all
the systems paths of least resistance (degrees of
freedom) are controlled by joint boundary
conditions and prescribed motion. In other
words, a complete system has zero degrees of
freedom. Only complete systems can be solved
with the CATIA KINEMUSE function. To
solve an incomplete system, one in which
degrees of freedom exist, the analysis type has to
switch from kinematic to one that also includes
dynamics. The CATDADS function provides
this additional capability. CATDADS is the
trade name for the DADS software embedded in
the CATIA environment. In order to use
CATDADS, the CATIA installation must first
have authorization for the KINEMAT function.
CATDADS requires additional information
beyond the system kinematics, which is readily
available in the solids database: mass, center of
mass location, and inertia tensor. Furthermore,
the CATDADS entities are stored within the
CATIA model and can be modified.
4.0 CATDADS
Figure 2 - Assembly Prototype Process
CATDADS excitation
input PolyFEM
Actuation
Requirements
Interference/
Collision/
Trace
Transient
Response
Reaction
Loads
Motion
Prediction/
Animation
Performance Assesment
CATIA Design Database
Control/Assembly Prototype Component Prototype
KINEMAT/
KINEMUS
SOLIDE/
SOLIDM LIBRARY
Assembly Prototype
component
characteristics
Figure 2 shows an expanded view of
the “assembly prototype” referenced by Figure 1.
The “assembly prototyping” occurs both in
KINEMUSE and CATDADS. CATDADS
provides the kinematic/dynamic response of the
system as a result of load transmission through
the systems kinematic chain. The system can
contain various types of force elements,
externally applied loads, motion drivers, etc.,
and the resulting descriptive equations of motion
are integrated forward in time. The system
equations of motion are automatically formed
and solved. Positions, velocities, accelerations
and reaction loads are predicted for all
components in the assembly. The CATDADS
analysis executables can be customized by the
engineers to add additional capability to the
commercial software as needed. The solution
types available within CATDADS are
kinematic, inverse dynamic, dynamic and static.
As has been previously stated, reaction loads are
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American Institute of Aeronautics and Astronautics
recoverable in all the analysis types except for
kinematics.
The starting point for the “assembly
analysis” is from CATIA KINEMAT/
KINEMUSE functions in which the sets are
kinematically coupled and motion drivers
applied to the system such that the system is
complete. Once the KINEMAT set, complete or
incomplete, has been represented, CATDADS is
invoked and the kinematic mechanism is
automatically converted to a CATDADS model.
Multiple kinematic mechanisms can be
managed by the same database with out having
to leave the CATDADS function. The
kinematic mechanism conversion takes place
entirely within CATIA, and the CATDADS
menu items and nomenclature maintain the
“look and feel” of the CAD system. In the
CATIA KINEMAT function, as joints are built
ICONS appear that give reference to the
boundary condition type. Once the CATDADS
convert function is applied, the ICON concept is
maintained, and as new elements are created
additional ICONS appear on the system. The
significant depth in which CATDADS is
embedded is evidenced by being able to apply
the CATIA LIBRARY functionality to manage
action/reaction elements (tires, bushings and
actuators), mechanical assemblies and subassemblies.
This indicates that existing
components can be taken “off the shelf” and
mated to a larger configuration or duplicated in
a different design without having to recreate the
database.
The excitation input to the “assembly
prototype” (CATDADS software) are external
loads that actuate the system or provide
resistance to component motion. The actuation
may be due to a commanded motor input, preloaded
spring cartridge, or some other action.
The load resistance may be due to joint friction,
aerodynamics or hydrodynamics. In future
releases of CATDADS and PolyFEM component
characteristics will be directly importable from
PolyFEM. After the modal or flexible
characteristics of a component has been
determined to be important to the assembly
performance assessment, the component
characteristics will be retrievable from PolyFEM
in the form of normal modes, static modes, and
attachment modes. 4 Presently, the inclusion of
the mode types is available through NASTRAN,
IDEAS and ANSYS.
The system performance assessment is
visualized from within CATIA. As further
evidence of the CATDADS depth of integration
is the usage of CATIA functionality to
determine interference and collision of assembly
components. The collision information can be
used as feedback for modifying the design or for
determining impact loads between any of the
solids which would affect the resulting motion
of the system. Inverse dynamics can be used to
determine the system actuation requirements.
This analysis type first solves for the system
motion, and then determines what the required
input was to enforce the desired motion. The
results can be used as input to the
“control/assembly prototype”. The transient
response and reaction loads of any component in
the system can be graphically plotted to gain
further insight into the system behavior. The
component accelerations and reaction loads are
also available as input to the “component
prototyping” process (PolyFEM). Since the
prototyping is taking place within the confines
of CATIA the results are immediately available
for upstream design processing.
5.0 CATDADS/Plant EASY5
Figure 3 - Control/Assembly Prototype Process
EASY5 commands
CATDADS/
Plant
disturbances excitation
REACTION
LOADS
TRANSIENT
RESPONSE
INTERFERENCE/
COLLISION/
TRACE
MOTION
PREDICTION/
ANIMATION
sensors
actuators
Assembly Prototype
Performance Assesment
Control/Assembly Prototype
Figure 3 shows the “control/assembly
prototype” process. The roots of this process are
closely related to the “assembly prototype”.
Once the CATDADS assembly has been created,
the bi-products (actuation requirements and
Plant representation) are easily applied to the
control design tasks. The actuation
requirements can be used for the sizing of the
control system, and the assembly prototypes can
easily be embedded as the Plant within the
control circuit. An extension of CATDADS is
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American Institute of Aeronautics and Astronautics
the Plant option. CATDADS/Plant has the
capability to be automatically embedded inside
of EASY5’s Fortran Block, MATRIXx/
SystemBuild’s User-Code Block, and Matlab/
Simulink’s S-Function. EASY5 is the control
software that will be applied in the application
section. EASY5 is a software used to model,
analyze and design complex control systems.
Models are assembled from discipline-specific
components, such as hydraulics, as well as
primitive functional blocks, such as summers,
dividers and integrators. Analysis tools include
non-linear simulation, steady-state, linear
analysis, control system design, data analysis
and plotting. 3 The open architecture allows the
“assembly prototype” to be embedded as the
Plant via the EASY5 Fortran Block. In this
manner all of the control design tools are
available for assessing the “control/assembly
performance”. The Plant model can be
represented in either the non-linear or linear
form. The non-linear form is that in which the
resulting non-linear equations of motion are
solved simultaneously with the control states.
The linear form is achieved by linearizing the
Plant about an operating point. And once again,
due to the nature of the tool embedding, the
“system prototype” may be linearized from
within the control software or from the Plant
software.
The manner in which the CATDADS/
Plant is readied for control system
implementation is very natural. First, sensors
are attached to the mechanical system. The
sensors are applied to the system in the same
manner as force element mounting locations are
defined. The sensor types exist such that
component states, relative component states and
impact forces can be fed back to the controller.
Secondly, actuators are attached to the
mechanical system. The actuators introduce a
corrective reaction load back to the plant based
upon the sensory feedback and commanded
input. The last step required is to set the
method of integration to the appropriate control
software. This action toggles CATDADS to
operate as a subroutine for the respective control
software. Once the control simulation is
complete the results can be imported back into
CATIA for visual and graphical interpretation.
The manner in which CATDADS is
embedded within the control software is unique.
The control states and mechanical states are
appended into a single state vector and
integrated forward in time simultaneously with
the same integrator. In this manner actuation
commands, control disturbances and external
excitation are allowed to interact with the Plant
in a closed-loop fashion. This leads the way to
performing control structure interaction studies.
The performance assessment can be further
carried out to investigate how well the control
affects the assembly. The depth of tool
embedding allows interactive simulations to be
performed which allows manual fine tuning of
control gains. Since the “control/assembly
prototyping” is taking place within the confines
of CATIA the results are immediately available
for upstream design processing.
6.0 PolyFEM
Figure 4 - Component Prototype Process
PolyFEM
SHAPE
OPTIMIZATION
STRESS/
MODAL/
THERMAL
COMPONENT
CHARACTERISTICS
CONTOUR
PLOTS/
ANIMATION
Assembly Prototype
Component Assesment
Material
Properties
Database
CATDADS
EXTERNAL
LOADS
reaction loads
accelerations
CATIA Design Database
PARAM SOLIDE/
SOLIDM
Component Prototype
aero loads
thermal loads
Figure 4 shows the “component
prototype” process. Once again, the starting
point is CATIA, and the prototyping occurs in
PolyFEM. PolyFEM is a finite element analysis
package that is completely embedded within the
CAD package. An automatic mesher is utilized
and the solution is achieved by a p-type finite
element solver. PolyFEM was developed with
ease of use and finite element modeling for the
masses as the main focus. No expertise in finite
element analysis is required to apply the
technology. Since p-elements are used, features
do not have to be suppressed and the mesh does
not need to be manually altered to achieve first
level analysis results. PolyFEM is not intended
to act as a substitute for high end finite element
analysis tools. The intent is to provide the
means for the designer, analyst and systems
engineer to gain insight into how the component
will perform as the design matures. The steps
required to obtain stress, thermal or modal
results are as simple as fixing the part, applying
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American Institute of Aeronautics and Astronautics
the loads, material properties and selecting
solve. The immediate graphical and visual
feedback of results allows the engineer to
determine whether the solution has converged.
If convergence has not taken place, then
additional solves can be initiated to achieve the
desired accuracy. The first visual image the
engineer sees is the component displacement
which is compared with engineering judgment
to validate how the loads and boundary
conditions were applied.
As boundary conditions and loads are
applied, ICONS appear along the selected
surfaces and boundaries with different colors
indicating the condition. Furthermore, the
ICONS are adaptive in nature. For example, if a
load is at an angle with respect to a surface or
coordinate system, the vectors emanating from
the ICON reflects the angle. This further
provides visual feedback to the engineer that the
boundary conditions and loads were applied
correctly. The input to PolyFEM is the CATIA
SOLIDE/SOLIDM database and PARAM3D,
external loads, material properties database, and
CATDADS accelerations and reaction loads.
PolyFEM only operates on the CATIA solids
database without any IGES translations taking
place. To assist in the component assessment
part optimization, stress, thermal and modal
solutions are available along with contour plots
and animation’s to act as graphical and visual
aids to the engineering judgment process.
7.0 Application Example
Figure 5 - Landing Gear Drop
Table 1 - Landing Gear Drop Test Values
Test
No.
Weight
(lbf)
Vertical Sink
Speed (ft/sec)
Landing Air
Speed (mph)
1 40000 5.0 150.0
2 40000 10.0 150.0
The landing gear shown in Figure 5 is a replica
of an F-15 Eagle main gear. The three images
show the gear at three different stages of a drop
test. The load case for part one of the
application example is a simulated drop test.
The variables for the load case are aircraft
weight, vertical sink speed, and landing
airspeed. Table 1 shows the variable values for
the two drop tests. Starting with SOLIDE
geometry and an incomplete KINEMAT set
inside of CATIA, the kinematic model is
converted to a dynamics model using the
CATDADS functionality. The dynamic model
has 3 DOF: tire rotation, oleo shock translation,
aircraft vertical motion. Figure 6a shows the
oleo strut force, and Figure6b shows the planar
load on the lower torque arm. The transient
responses were obtained using both sets of test
conditions shown in Table 1. The interference
and collision features of CATDADS were also
used to insure that no obstructions developed
during the drop tests.
Figure 6a - Oleo Strut Force
Figure 6b - Planar Load
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American Institute of Aeronautics and Astronautics
Figure 7 - Landing Gear Retraction
The second part of the application
example involves fixing the aircraft’s vertical
motion and releasing the retraction actuator
such that the system still has 3 DOF. Figure 7
shows the gear undergoing retraction. The
CATDADS/Plant EASY5 extension was used
for simulating the retraction hydraulics. The
hydraulic circuit is shown in Figure 8. From
within CATDADS, control sensors were
connected to the retraction axis for feeding back
the stroke, velocity and acceleration to the
controller. An actuator was also connected to
the retraction axis for applying the output of the
hydraulic circuit to the gear.
-
Figure 9 shows the actuation force required to
retract the gear.
Figure 9 - Hydraulic Actuation Force
The third part of the application
example involves applying the peak load shown
in Figure 6b to the lower torque arm shown in
Figure 10. The part was fixed, loaded and a
stress solution was performed. The same part
was re-evaluated with a web and fillet. The
deformed and undeformed lower torque arm is
shown in Figure 11 before and after the
redesign. The deflection and stress summary is
shown in Table 2.
Figure 10 - Landing Gear Lower Torque Arm
Figure 11 - Lower Torque Arm
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American Institute of Aeronautics and Astronautics
Table 2 - Deflection and Stress Summary
Torque Arm Deflection (in) Stress (ksi)
before 0.070 100.0
after 0.011 35.0
8.0 Summary
The SDD process applies to all types of
systems encompassing kinematic, component
and controlled motion design. The paper has
presented “CAD embedded CAE tools”. The
CAD tool applied was CATIA, and the CAE
tools were CATDADS, EASY5 and PolyFEM.
The application example was an electronically
prototyped aircraft landing gear exposed to a
drop test and retraction simulation. The
performance assessment resulted in the CAD
database being naturally updated to achieve a
more efficient design. The efficiency was
achieved by operating from a single CAD
database with the results being available for
upstream processing. With this approach,
training requirements and the number of experts
are significantly reduced which suggests that
virtually all related engineering establishments
can apply this technology without having to
maintain a high level of readiness to apply the
CAE tools when the need arises.
SDD brings PDT to their full fruition.
The teams, designed and configured to eliminate
the “over the wall” approach to design, still have
inter-team barriers due to the need to translate
data from the design database to “integrated”
CAE tools. The “integrated” CAE tool
approach contributes more non-value added
activity and fractures the system, design and
analysis databases. The SDD approach
facilitates the mission of PDTs by merging the
system design and analysis databases. During
the process of applying the SDD, the CAD
environment provided the framework for the
“total system prototype”. As shown in Figure 1,
at the end of the SDD process is the “brass
board”. The “brass board” is the physical
prototype that is used for final verification and
system checkout. Without applying SDD, the
physical prototype would be a “bread board”
requiring a series of costly iterations to approach
the quality of the “brass board”. Thus the brass
board approach is the achievement of the “new
paradigm” through the application of the SDD
environment.
References
1. E. J. Haug, Computer Aided Kinematics
and Dynamics of Mechanical Systems,
Volume 1: Basic Methods. Needham
Heights, Massachusetts: Allyn and Bacon
(1989).
2. Anon., PolyFEM User’s Guide, Computer
Aided Design Software Inc., 1997.
3. Anon., EASY5 User’s Guide, The Boeing
Company., 1997.
4. S. Wu, E. J. Haug, and S. Kim, “A
Variational Approach to Dynamics of
Flexible Multibody Systems,” Mechanics of
Structures and Machines, Vol. 17, No. 1,
1989, pp. 3-32.

playboy2618

谢谢了，呵，呵，呵，我想要一点教程什么的，他的帮助太差近了，看不懂，软件介绍可以看恒润公司的网页，中文介绍的

haoya

一汽的吧？

playboy2618

一汽有什么好的？偶就不能在别的地方活了？

playboy2618

也用不着拿一个破烂地方来唬人

haoya

别那么大的火气，有什么问题我可以帮你。

haoya

另外我不觉得它的帮助不好，非常清晰明白，因为它的帮助是美国人写的。