Rondall E. Jones

The Archimedes 2 mechanical assembly planning system

We describe the implementation and performance of Archimedes 2, an integrated mechanical assembly planning system. Archimedes 2 includes two planners, two assembly sequence animation facilities, and an associated robotic workcell. Both planners use fully 3 dimensional data. A rudimentary translator from high level assembly plans to control code for the robotic workcell has also been implemented. We can translate data from a commercial CAD system into input data for the system, which has allowed us to plan assembly sequences for many industrial assemblies. Archimedes 2 has been used to plan sequences for assemblies consisting of 5 to 109 parts. We have also successfully taken a CAD model of an assembly, produced an optimized assembly sequence for it, and translated the plan into robot code, which successfully assembles the device specified in the model.

On constraints in assembly planning

Constraints on assembly plans vary depending on product, assembly facility, assembly volume, and many other factors. Assembly costs and other measures to optimize vary just as widely. To be effective, computer-aided assembly planning systems must allow users to express the plan selection criteria that apply to their products and production environments. We begin by surveying the types of user criteria, both constraints and quality measures, that have been accepted by assembly planning systems to date. The survey is organized along several dimensions, including strategic versus tactical criteria; manufacturing requirements versus requirements of the automated planning process itself; and the information needed to assess compliance with each criterion. The latter strongly influences the efficiency of planning. We then focus on constraints. We describe a framework to support a wide variety of user constraints for intuitive and efficient assembly planning. Our framework expresses all constraints on a sequencing level, specifying orders and conditions on part mating operations in a number of ways. Constraints are implemented as simple procedures that either accept or reject assembly operations proposed by the planner. For efficiency, some constraints are supplemented with special-purpose modifications to the planners algorithms. Fast replanning enables an interactive plan-view-constrain-replan cycle that aids in constraint discovery and documentation. We describe an implementation of the framework in a computer-aided assembly planning system and experiments applying the system to a number of complex assemblies, including one with 472 parts.

Constraint-based interactive assembly planning

Constraints on assembly plans vary depending on product, assembly facility, assembly volume, and many other factors. This paper describes the principles and implementation of a framework that supports a wide variety of user-specified constraints for interactive assembly planning. Constraints from many sources can be expressed on a sequences level, specifying orders and conditions on part mating operations in a number of ways. All constraints are implemented as filters that either accept or reject assembly operations proposed by the planner. For efficiency, some constraints are supplemented with special-purpose modifications to the planners algorithms. Fast replanning enables a natural plan-view-constrain-replan cycle that aids in constraint discovery and documentation. We describe an implementation of the framework in a computer-aided assembly planning system and experiments applying the system to several complex assemblies.

Lessons learned from a second generation assembly planning system

Briefly describes Archimedes 2, a second generation assembly planning system that both provides a general high-level assembly sequencing capability and, for a smaller class of products, facilitates automatic programming of a robotic workcell to assemble them. Because Archimedes can input CAD data in several standard formats, the authors have been able to test it on a number of industrial assembly models more complex than any before attempted by automated assembly planning systems. These experiments, and the authors, interaction with industrial manufacturing engineers, have led them to a number of conclusions about the state of assembly planning research, and their own future directions in particular.

Synchronization and control of parallel algorithms

Abstract We propose a modest collection of primitives for synchronization and control in parallel numerical algorithms. These are phrased in a syntax that is compatible with FORTRAN, creating a publication language for parallel software. A preprocessor may be used to map code written in this extended FORTRAN into standard FORTRAN with calls to the run-time libraries of the various parallel systems now in use. We solicit the readers comments on the clarity, as well as the adequacy, of the primitives we have proposed.

Usage and Argument Monitoring of Mathematical Library Routines

Usage of mathematical library (MATHLIB) routines on the Control Data 6600 system at Sandia Laboratories, Albuquerque, New Mexico, has been momtored for over three years. The value of one input argument during the first execution of each library routine in each job along with the identification number of the user has been monitored for about two years. The selection and implementation of the method used for monitoring and the impact of monitoring on the user and on the system are discussed. The significance of the usage data is discussed for several actual applications, and additional possible uses of the data and planned extensions of monitoring are mentioned.

XERROR, the SLATEC error-handling package

The XERROR package is a collection of portable Fortran routines for processing of errors that occur in other routines. It was developed as the error‐handling package for the SLATEC Common Mathematical Library, which is currently in use at a number of U.S. Department of Energy and other facilities. This paper describes how to use the package, from the viewpoint of the writer of library routines that need to call the XERROR package to handle errors, and from the viewpoint of the user of those library routines.

Features Automated assembly and fixture planning at Sandia National Laboratories

The Intelligent Systems and Robotics Center at Sandia National Laboratories supports several ongoing projects oriented towards enabling the creation of more automatic and effective robotic assembly systems, especially for small lot production. Two of these projects are Archimedes, which is an automatic assembly planning system, and HoldFast, which automatically designs optimal form‐closure fixtures. These technologies have application in many automated assembly contexts, whether robotic or not. Discusses the current state and applications of these two technologies. Both are based on use of a 3D CAD model, which currently must be converted to ACIS form for processing. Archimedes reasons about the liaisons between parts, then derives an assembly plan that is geometrically valid. This plan is improved by interaction with the user, who adds “constraints” to guide replanning. Facilities to define and search for a user’s “optimal” plan are under development. Given a workpiece shape, task constraints, and a description of a fixture kit, HoldFast finds the optimal fixture that can be made from the kit to hold the workpiece in form‐closure.

Notes from the second department of energy library Workshop

The U.S. Atomic Energy Commission (AEC) and its successors, first the U.S. Energy Research and Development Administration and now the U.S. Department of Energy (DOE) and Nuclear Regulatory Commission, has been and continues to be one of the nations major purchasers and users of large scale scientific computers. Historically, each of the more than dozen computer centers at different laboratories evolved independently of the others so that each was self-contained. In particular, each computer center developed mathematical software libraries according to its own needs. In 1975, representatives for the mathematical software libraries at the various AEC computer centers met, with Argonne National Laboratory as the host, to hold the first Workshop on the Operational Aspects of Mathematical Software Libraries. Among the purposes of the first Workshop were: (1) to meet colleagues doing similar work at other AEC computer centers, (2) to share experiences in the management of mathematical software libraries, and (3) to discuss ideas and issues in the operation of libraries. The first Workshop was sufficiently rewarding that the participants felt it appropriate to hold a second Workshop in three years, an interval that would encompass sufficient progress in library operation that new experiences and ideas could be discussed.

Activities of the DOE Advanced Computing Committee Language Working Group

The Language Working Group is a technical arm of the DOE Advanced Computing Committee. The purpose of the Group is to work toward providing a compatible Fortran environment at the ACC sites. A brief history of the efforts of the Group is given, and the general features of the language the group will recommend are discussed. This language is a multi-level Fortran with Fortran 77 as the core.