David D. Grossman

A geometric modeling system for automated mechanical assembly

Very high level languages for describing mechanical assembly require a representation of the geometric and physical properties of 3-D objects including parts, tools, and the assembler itself. This paper describes a geometric modeling system that generates a data base in which objects and assemblies are represented by nodes in a graph structure. The edges of the graph represent relationships among objects such as part-of, attachment, constraint, and assembly. The nodes also store positional relationships between objects and physical properties such as material type. The user designs objects by combining positive and negative parameterized primitive volumes, for example, cubes and cones, which are represented internally as polyhedra. The data base is built by invoking a procedural representation of the primitive volumes, which generates vertex, edge, and surface lists of instances of the volumes. Several applications in the automatic assembly domain have been implemented using the geometric modeling system as a basis.

An Experimental System for Computer Controlled Mechanical Assembly

This paper describes the software and hardware architecture of a system designed as a research tool for experiments on programming the computer controlled assembly of mechanical objects. The software consists of a real-time control level and a background level in which an on-line interpreter permits interactive programming. The hardware consists of a manipulator with sensory feedback coupled to an IBM System/7. Additional facilities are available through a link to an IBM System/370 Model 145. The application of the system to sample assemblies is also discussed.

An integrated robot system architecture

This paper describes the architecture of a robot system designed both to work in an integrated manufacturing environment and to support continuing research in programmable automation. Major system components include a controller, robot and sensor hardware, operators pendant, and system software. A new high-level interactive language, AML, allows the user to combine manipulation, sensing, computational, and data processing functions provided by the system. Important aspects of the system design objectives, major functional components, and the AML language are described, and examples drawn from an actual production application are used to illustrate the interrelationship of the topics discussed.

Placement of Records on a Secondary Storage Device to Minimize Access Time

The problem considered is how to place records on a secondary storage device to minimize average retrieval time, based on a knowledge of the probability for accessing the records. Theorems are presented for two limiting cases. A numerical example for an intermediate case is also given.

Orienting Mechanical Parts by Computer-Controlled Manipulator

In order to assemble mechanical parts which are initially disordered, a computer-controlled manipulator needs some procedure for orienting these parts. An apparatus is described which assists the manipulator in performing this function. The device is a dihedrally tipped open box attached to a vibrator. When placed in the box, a typical mechanical part assumes one of a small finite number of possible orientations. Once the particular orientation is established, the manipulator shifts the part into the desired orientation.

Interactive Generation of Object Models with a Manipulator

Manipulator programs in a high-level language consist of manipulation procedures and object model declarations. As higher level languages are developed, the procedures will shrink while the declarations will grow. This trend makes it desirable to develop means for automating the generation of these declarations. A system is proposed which would permit users to specify certain object models interactively, using the manipulator itself as a measuring tool in three dimensions. A preliminary version of the system has been tested.

Procedural representation of three-dimensional objects

A system of PL/I procedures has been written that permits geometric objects to be described hierarchically. The objects are themselves represented as PL/I procedures, allowing very general use of variables. By effectively intercepting subprogram calls, the system provides a means of modifying the semantics associated with any object without modifying the objects procedural description.

XPROBE: An Experimental System for Programming Robots by Example

XPROBE extends the teaching-by-showing method of robot programming to the teaching of sensor strategies. The XPROBE system has a dialogue with the user, during which the user is directed to guide the robot through an example of the desired task. XPROBE then automatically writes an AML program that includes sensory decision making as a generalization of the taught example.

The value of multiple independent robot arms

Abstract When multiple independent robot arms attempt to perform concurrent operations at the same work cell, spatial interference imposes limits on the degree of parallelism that can be achieved. It is shown that as the number of independent arms approaches infinity, the degree of parallelism is bounded. Mathematical limiting values are derived for the extent of parallelism for two cases of an idealized simplistic application. The main value of these results is to demonstrate that under conditions of spatial contention, there is little merit in having more than two independent arms at a work cell. Designing the work cell to reduce contention increases the value of multiple independent arms.

Opportunities for research on numerical control machining

Numerical control (NC) machining could be reinvigorated by adapting robotic software technology. Regrettably, pressures are mounting in industry to constrain robots to NC standards, and the academic community views NC as an obsolete, solved problem, with little remaining scholarly challenge. Grossman examines the current status of APT, an NC language, and proposes the merging of APT with a modern robotics language.