Behavior and Design Intent Based Product Modeling

Abstract

A knowledge based modeling of mechanical products is presented for industrial CAD/CAM systems. An active model is proposed that comprise knowledge from modeling procedures, generic part models and engineers. Present day models of mechanical systems do not contain data about the background of human decisions. This situation motivated the authors at their investigations on exchange design intent information between engineers. Their concept was extending of product models to be capable of description of design intent information. Several human-computer and human-human communication issues were considered. The complex communication problem has been divided into four sub-problems, namely communication of human intent source with the computer system, representation of human intent, exchange of intent data between modeling procedures and communication of the represented intent with humans. Paper discusses the scenario of intelligent modeling based engineering. Then key concepts for the application of computational intelligence in computer model based engineering systems are detailed including knowledge driven models as well as areas of their application. Next, behavior based models with intelligent content involving specifications and knowledge for the design processes are emphasized and an active part modeling is proposed and possibilities for its application are outlined. Finally, design intent supported intelligent modeling is discussed.

Full text

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Behavior and Design Intent Based Product
Modeling
László Horváth, Imre J. Rudas
John von Neumann Faculty of Informatics, Budapest Tech
Népszínház u. 8, H-1081 Budapest, Hungary
horvath.laszlo@nik.bmf.hu
rudas@bmf.hu
Abstract: A knowledge based modeling of mechanical products is presented for industrial
CAD/CAM systems. An active model is proposed that comprise knowledge from modeling
procedures, generic part models and engineers. Present day models of mechanical systems
do not contain data about the background of human decisions. This situation motivated the
authors at their investigations on exchange design intent information between engineers.
Their concept was extending of product models to be capable of description of design intent
information. Several human-computer and human-human communication issues were
considered. The complex communication problem has been divided into four sub-problems,
namely communication of human intent source with the computer system, representation of
human intent, exchange of intent data between modeling procedures and communication of
the represented intent with humans. Paper discusses the scenario of intelligent modeling
based engineering. Then key concepts for the application of computational intelligence in
computer model based engineering systems are detailed including knowledge driven
models as well as areas of their application. Next, behavior based models with intelligent
content involving specifications and knowledge for the design processes are emphasized
and an active part modeling is proposed and possibilities for its application are outlined.
Finally, design intent supported intelligent modeling is discussed.
1 Introduction
Model based development of products uses advanced process-centric digital
product and manufacturing process definition techniques. Shapes, parts, assembly
relationships, joints, tolerances, finite element related parameters, cutting tool
paths for computer control of machining and product structures are main objects
to be described in feature and associativity driven product models. Products are
positioned for e-business among others by the help of using model-based
approach. Scope of engineering modeling is being extended to the entire life cycle
of products. Comprehensive application of virtual technology is the essence of the

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concept of digital enterprise where all engineering activities and equipment
controls are done within a highly integrated modeling system.
Key participants of engineering processes are still skilled engineers who are
sitting at their computers with advanced user communication features. Engineers
expect more and more computer assistance at their decisions in changed industrial
environments where quick and efficient engineering decisions are needed to
survive competition in the market. However, modeling methods that really
enhance human decision assistance capability of engineering modeling procedures
during interactive part modeling sessions are not available. Powerful decision
assistance use analyses that need behavior based modeling of engineering objects
in various circumstances. In other words, analysis of object behavior is done in
virtual. The authors investigate possibilities and means of new enhancements in
knowledge based active modeling procedures.
Advancements in part related engineering modeling is motivated both by
expectations for high performance parts with well-engineered shape. Performance
of modeled objects can be assessed by using of various implementations of finite
element analysis. Advanced shapes are best produced by advanced surface model
driven and computer controlled manufacturing of parts or tools for making parts
[6]. Stand alone part model objects are integrated into product models by using of
structure descriptions and associativity definitions. Results of the part design are
protected against modification by the definition of shape, dimensions and
associativities as constraints.
Despite these fantastic advancements some important aspects of modeling could
not follow this evolution. One of them is application of active models. The above
outlined scenario is a good starting point for development of virtual environment
based engineering modeling where advanced knowledge technology is integrated
with advanced product modeling technology. The purpose of this paper is to give
an outline of an advanced concept and a modeling method for intelligent model
features in engineering models. This modeling is suitable for implementation in
industrial CAD/CAM systems. Preliminaries of the reported research are
developments in methodology to integrate manufacturing process modeling with
form feature based part modeling by using of relationship and constraint
definitions [1].
Design intent covers results of a complex human thinking process. Modeling tools
in present day CAD/CAM systems are not suitable for description of this process.
Advanced, customer oriented product design requires frequent modification of
earlier decisions. Moreover, modification of result of a decision often causes a
need to modification of results of other decisions. This is impossible in the lack of
proper background information for the original decision. Consequently,
modifications of original decisions require contribution of the original decision-
maker or other authorized engineer. Because live communication between
engineers typically is not available, the only effective way is to describe their

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intent in the product model to be modified. Inevitably, computer modeling should
be extended to this area. The authors propose a computer method to assist the
modification of decisions by modeling of design intent.
Paper discusses some issues of intelligent modeling based engineering. As an
introduction, it outlines the scenario of the related activities and systems. Then
key concepts for the application of computational intelligence in computer model
based engineering systems are detailed including knowledge driven models as
well as areas of their application. Next, behavior based models with intelligent
content involving specifications and knowledge for the design processes are
emphasized, an active part modeling is proposed, and possibilities for its
application are outlined. Finally, design intent supported intelligent modeling is
discussed.
2 Intelligent Content in Virtual Environments
An important assumption in advanced models of mechanical systems is that the
model, in which new or modified features are defined, is created earlier using
other modeling system and by other engineer. At the same time multiple designer
operation mode in concurrent group work of engineers is assumed where several
engineers handle a model. Both modeling procedures and designers utilize model-
related knowledge in order to achieve effective product modeling process. Role of
knowledge communication associated with model data communication is
assistance of multiple designer and multiple modeling system related problem
solving.
Knowledge content of model entities can be utilized in the design process at
definition of product objects and simulations. An initial concept to integrate
knowledge in modeling was to include knowledge to modeling procedures of
CAD/CAM systems. This approach supports representation of generally
applicable and domain related knowledge. However, most of the knowledge is
company, product, even human related one and it changes from company to
company and product to product. The only effective way is integration this
knowledge in models of abstract or instance objects in the product model. This
approach is anticipated to be one of the most researched and developed areas in
model based engineering design during the next few years by the authors.
Significant part of knowledge necessary at later processing of a model is modeled
object, model and modeling system specific (Fig. 1). This knowledge is not
available at the application of the model so that it is to be exchanged with models
between modeling systems. Built-in knowledge then helps engineers at
development, modification and application of the model. It also prevents model
quality from deterioration at its later application and modification. Knowledge

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L. Horváth et al. Behavior and Design Intent Based Product Modeling
content and other advanced features resulted modeling where models can answer
most of important questions about the modeled real world object before, during
and after their manufacturing. Recently, advanced modeling systems that include
models of this kind are called as virtual environments.
Virtual environment
specific knowledge
Modeled object specific
knowledge
Model specific
knowledge
Model data exchange
Creation of product model
Model with built in knowledge
Application of knowledge
exchanged with the model
Exchanged model with built in knowledge

Figure 1
Knowledge in engineering modeling
Model with the capability of reaction using behavior related knowledge acts an
intelligent design of the modeled object that can communicate built in knowledge
with modeling procedure or human to save earlier decisions and human intent
while new decisions and intents are captured in the model. Knowledge content of
model is developed with its development. Behavior based models with intelligent
content involve specifications and knowledge for the design processes (Fig. 2).
Specifications are results of design with appropriate explanations. Model of
design intent is considered to be described as specification in [2]. Knowledge
normally is related to given specification but it is also can be independent of any
specification. Definition of specifications and knowledge needs authorization
according to role of engineers in the product development team and stage of the
design process.
Intent of engineers
Proven practice
Standards
Capturing intelligent content
Automatic creation, modification
and update of model entities
Goal-directed behavioral model
Simulation
Intelligent content of the model
For design process
Specification
Knowledge
Reusing intelligent content
(Emulation of intelligence)


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Figure 2
Knowledge assisted modeling
Forthcoming development and application of the model utilize its intelligent
content at automatic creation, modification and update of model entities.
Representation of knowledge should be as simple as can be so that it is easy to
define by engineers in their every day practice. Most appropriate forms of
knowledge are formulas, rules and checks because these are natural in engineering
design. Compliance of the model with proven practices and standards can be
ensured. Behavior based modeling offer conversion of implicit engineering
practice into explicit knowledge.
Creating a new model is enhanced by application of models of abstract objects.
An abstract object carries characteristics of a set of similar objects. At creating of
a new modeled object instance from the model of an abstract object, actual
characteristics of the instance object are set. This process can be automated by
including knowledge in model objects. Model of an abstract object may involve
domain, company and designer related knowledge. Model of an instance object
generally contains domain, company, product and designer related knowledge.
Information on origin and validation of the utilized knowledge should be included
otherwise responsibility for the product can not be evaluated.
An advanced form of model objects in virtual environments is autonomous
intelligent agent that is created by human or computer procedures (Fig. 3).
Intelligent agents are autonomously working procedures in the software system
with goal-directed behavior interacting with given environments [5]. Human
control is realized directly by interaction with model creating procedures or
indirectly by instruction or knowledge placed in agents. Behavior of agents is
modeled in a multi-agent system. This modeling environment constitutes a
reactive system. Reactive behavior of agents is controlled by appropriate creation
of the model. Series of circumstances are identified and responded. Models are
utilized in automatic or human controlled interactive, real-time simulations.
Simulations are applied for analysis of critical situations and events during
manufacturing and application of the modeled product. Simulation is a key
technique for virtual prototyping where advanced modeling is applied to move
physical prototyping activities into virtual environments. Real time assessment
and analysis are assisted by appropriate intelligent procedures.