MODULAR PRECISION ASSEMBLY SYSTEMS

http://www.cs.cmu.edu/~msl

The Microdynamic Systems Laboratory in the Robotics Institute at
Carnegie Mellon University has embarked on a new project to improve
the way automated assembly systems are designed, programmed, deployed,
and operated.  We are concerned with the creation of new hardware and
software technologies and methods for automated assembly of precision
high-value products such as magnetic storage devices, palmtop and
wearable computers, and other high-density equipment.  Our developing
Agile Assembly Architecture (AAA) supports the creation of miniature
assembly factories (minifactories) built from small modular robotic
components.  The goals are to substantially reduce design, deployment,
and product changeover times, to greatly improve quality levels by
using sensor-moderated precision motion, and to achieve new levels of
manufacturing system portability by shrinking the sizes of typical
assembly systems from large room size to tabletop size.

We believe these goals can only be achieved through careful
integration of hardware and software tools in a manner heretofore
unseen in the robotics and automation community.  We are building a
distributed system of tightly integrated mechanical/computational
agents endowed not only with information about their own capabilities
but also with the ability to appreciate their role in the factory as a
whole and negotiate with their peers in order to participate in
flexible factory level cooperation.

AAA will use defined procedures, protocols, and well-structured agent
autonomy to simplify the process of designing and programming large
high-precision assembly systems [1].  The unified design and
programming tools of AAA will allow a user to select agents over the
Internet and program them in a simulated factory environment.  AAA
will take advantage of agents' self-knowledge and ability to explore
their environments to make the transition between simulation and
reality as painless and seamless as possible.  To facilitate the
design and operation of distributed systems of this type, each
minifactory agent will be capable of representing itself to its peers
and providing detailed models (both geometric and behavioral) for use
in its simulation.  To support a suitably extensible simulation
environment, we expect to make use of distributed models and
processing by relying on agents to represent their own behavior during
simulation [2].  This mitigates the need to develop necessarily
restricted models for agent behavior and allows for simplified
integration of new types of agents into AAA.  

Figure 1 illustrates how a designer might develop a specific
minifactory for a particular family of related products.  The designer
is shown interacting with a comprehensive modeling and simulation
environment.  Functional models of the minifactory components are
distributed: they reside within each minifactory module at the
geographic location of the module vendor company.  By accessing and
incorporating data from each on-line module remotely (by Internet),
the modeler/simulator has only up to date and reliable information
instead of catalog or faxed data sheet information which might not
reflect the currently available module product.  During the creation
of the minifactory design, the designer is free to select and simulate
a wide variety of configurations using modules from many different
sources to arrive at a final design (virtual minifactory).  The
designer may also make use of various tools such as automated assembly
sequence planners, schedulers, and layout tools.  Many other steps
will be required successfully program, deploy, and operate a complete
minifactory.  Figure 2 is a representative sketch of the minifactory
hardware we are developing [3].  Products move through the factory on
the backs of couriers based on closed loop planar linear motors
interacting with overhead devices which place parts and perform other
operations.

Our hope is that AAA and minifactory can provide viable high-precision
assembly alternatives for industries that would benefit from
drastically reduced factory design and deployment time.  More
generally we project that the resulting class of factory automation
will be suitable for use in the production of short-lead-time products
consisting of moderate-sized high-precision parts and assemblies.  We
see this distributed approach to factory design, modeling and control
affording a number of advantages including modularity, robustness,
efficiency, and simplicity.

Acknowledgements

This research is supported in part by the National Science Foundation
under grants CDA-9503992, DMI-9523156, and DMI-9527190, and by the
CMU Engineering Design Research Center and CMU Data Storage Systems
Center. 

Dr. Ralph Hollis
The Robotics Institute
Carnegie Mellon University
Pittsburgh, PA 15213 USA
E-mail: rhollis@cs.cmu.edu


References
    
[1]  R. L. Hollis and A. Quaid,
     "An Architecture for Agile Assembly,"
     Proc. Am. Soc. of Precision Engineering, 10th Annual Mtg.,
     Austin, TX, October 15-19, 1995.

[2]  A. A. Rizzi, J. Gowdy, and R. L. Hollis,
     "Agile Assembly Architecture: An Agent-Based Approach to Modular
     Precision Assembly Systems,"
     IEEE Int'l Conf. on Robotics and Automation, Albuquerque,
     April 20-25, 1997.

[3]  A. Quaid and R. L. Hollis,
     "Cooperative 2-DOF Robots for Precision Assembly,"
     IEEE Int'l Conf. on Robotics and Automation, Minneapolis,
     April 22-28, 1996.   


Figure Captions

Figure 1. Minifactory Design Scenario

Figure 2. Operating Minifactory