Intelligent Assembly Modeling and Simulation
Main Participants: Satyandra K.
J. Paredis, R. Sinha, and P. F. Brown
Sponsors: This research was funded in part by DARPA, Raytheon
and National Institute of Standards and Technology.
Keywords: Assembly Modeling, Assembly Planning, and Assembly
Developing high-performance electro-mechanical products is a very
task. In order to improve efficiency and reduce the product weight and
designers need to pack a large number of components in a very small
At the same time, in order to make products easier to assemble and
designers need to leave enough room for performing assembly and
operations. These requirements are quite often in conflict and make
of electro-mechanical products a highly iterative process. In the
of high fidelity simulation tools, most product development teams are
to include physical prototyping in the design loop to verify proper
and ease of assembly. Physical prototyping is a major bottleneck. It
down the product development process and seriously constrains the
of design alternatives that can be examined. Furthermore, after a
has been built and tested, a significant amount of time is spent
instructions for performing assembly and service.
Rapid technical advances in many different areas of scientific
provide the enabling technologies for creating a comprehensive
and visualization environment for assembly design and planning. We
that developing and maintaining a single monolithic system for assembly
will not be practical. Instead, we have built an environment in which
simulation tools can be composed into complex simulations. Our goal in
project is to develop high fidelity assembly simulation and
tools that can detect assembly related problems without going through
mock-ups. In addition, these tools will be used to create
instructions for performing assembly and service operations.
Main Results and Their Anticipated Impact
In our Intelligent Assembly Modeling and Simulation (IAMS) environment,
designer creates an assembly design using a commercial CAD package.
adding information about articulation and assembly features, the
stores the design in the assembly format. The designer then selects a
of simulation tools and composes them into a customized simulation. In
process engineers create a model of the work cell in which the parts
be assembled. The designer proposes an initial sequence in which this
can be performed - either interactively or through the use of assembly
software. He uses the simulation environment to analyze the assembly,
he makes changes in the assembly after discovering problems. Currently,
simulation environment includes the facilities for performing
detection, tool accessibility analysis, and detailed path planning.
When the designer is satisfied with the design, the process engineer
optimize the workspace and create a detailed animation of the assembly
This sequence is downloaded to the operator's desktop computer, where
can be consulted using a browser. The operator can start assembling the
immediately, without the need for extensive training.
Our software environment consists of four major components: (1) an
editor, (2) a plan editor, (3) an assembly simulator, and (4) an
generator/viewer. The assembly editor imports CAD files of individual
from an ACIS-based solid modeling system and organizes them into an
representation. Using feature recognition techniques, the assembly
recognizes joints between parts and assembly features on individual
The plan editor allows users to synthesize assembly plans
The assembly sequence and tooling information (i.e., macro plans)
by the user are automatically converted into low level tool and part
(i.e., micro plans). Using the assembly simulator, the user selects and
various simulations (such as interference and tool accessibility). The
viewer allows the assembly operators to view the modeled assembly
interactively. The users can randomly access any particular operation
the assembly sequence and interactively change their 3D viewpoint.
Practically, these components can be used in the following manner. A
creates an assembly design using a commercial CAD package. The design
imported into our environment using the assembly editor. The designer
uses the plan editor to enter a specific assembly sequence. The
selects a number of simulation agents in the simulation controller and
them into a customized simulation. Based on the feedback from the
he may have to change the assembly design. After several design
he is satisfied with the design and hands it over to the process
In parallel, using the workspace editor, the process engineer has
a model of the work-cell in which this assembly will be performed.
incorporating the assembly in the workspace, the process engineer
a detailed simulation to check for any problems in the final assembly
plan. He then generates an animation of the assembly process that is
to the operator's desktop computer where it can be viewed by the
using the animation viewer. The operator can start assembling the parts
without the need for extensive training or tedious creation of
During our field trips, we found that most assembly operators already
computers on their workbenches to display digitized drawings and images
the assembly operations. As a result, we do not expect any major
or social obstacles to adopting this technology in the workplace.
Our system has been implemented using C++ programming language. It
runs on SUN (under Solaris operating system) and SGI workstations. We
ACIS for representing various parts in the assembly model. We use RAPID
performing interference tests. We use OpenInventor for graphical
We use the LEDA class library for implementing various data structures.
Our simulation environment incorporates the following new features.
We believe that our assembly modeling and simulation infrastructure
in this paper will allow the creation of much more complex products in
much shorter time. Specifically, we envision the following three main
- Articulated Tools and Products: Most electro-mechanical
have articulated devices. However, most assembly planning systems do
properly handle articulated products and tools. Our assembly simulator
be able to handle products and tools with built-in articulation. This
important for a large variety of designs, for which the articulated
need to be moved to perform the assembly operations.
- Automatic Plan Completion: When designing a complex
product, the designer usually already has a coarse assembly sequence in
mind. However, to perform a high fidelity simulation, it is important
an assembly plan in full detail. Our framework provides plan completion
that automatically fill in the details of high-level assembly
specified by the design and process engineers.
- Assembly Process Modeling: Most research efforts have
on the geometric aspects of the assembly (i.e., finding a sequence of
operation without part-part interference). We believe that assembly
and the workspace play a very significant role. Many of the problems
to assembly cannot be recognized without taking process models into
We therefore model the workspace. This allows the process engineers to
various types of environments in which the assemblies can be performed.
- Reduction in Physical Prototyping: By reducing the need
physical prototyping, we will be able to complete each design iteration
faster and significantly reduce the cost of prototyping.
- Agile Work Force: Ability to provide easy-to-follow
eliminates the need for work-force training in specialized activities.
we can have an agile work force that can be deployed to handle a wide
- Better Assembly Analysis/Planning Software: We believe
our simulation environment can be combined with a number of assembly
tools to create much better software. In particular, we see the
three potential applications of this research: (1) automated assembly
(2) optimum design for assembly workspaces, and (3) automated assembly
to improve manufacturability.
The following papers provide more details on the above-described
Some of these papers are available at the publications
section of the website.
- R. Sinha, S.K. Gupta, C. J. Paredis, P.K. Khosla. Extracting
models from CAD models of parts with curved surfaces. Journal of
Design, 124(1):106--114, 2002.
- S. K. Gupta, C. J. Paredis, R. Sinha, and P. F. Brown.
assembly modeling and simulation. Assembly Automation,
For additional information and to obtain copies of the above papers
Dr. Satyandra K. Gupta
Department of Mechanical Engineering and Institute for Systems Research
2135 Martin Hall
University of Maryland
College Park, Md-20742