M L. Fitzgerald

Simulation and Implementation of an Open Architecture Controller

The National Institute of Standards and Technology has developed a modular definition of components for machine control, and a specification to their interfaces, with broad application to robots, machine tools, and coordinate measuring machines. These components include individual axis control, coordinate trajectory generation, discrete input/output, language interpretation, and task planning and execution. The intent of the specification is to support interoperability of components provided by independent vendors. NIST has installed a machine tool controller based on these interfaces on a 4-axis horizontal machining center at the Pontiac Powertrain Division of General Motors. The intent of this system is to validate that the interfaces are comprehensive enough to serve a demanding application, and to demonstrate several key concepts of open architecture controllers: component interoperability, controller scalability, and function extension. In particular, the GM-NIST Enhanced Machine Controller demonstrates interoperability of motion control hardware, scalability across computing platforms, and extensibility via user-defined graphical user interfaces. An important benefit of platform scalability is the ease with which the developers could test the controller in simulation before site installation. The EMC specifications are serving a larger goal of driving the development of true industry standards that will ultimately benefit users of machine tools, robots, and coordinate measuring machines. To this end, a consortium has been established and cooperative participation with the Department of Energy TEAM program and the US Air Force Title III program has been undertaken.

Sensor Robotics In The National Bureau Of Standards

For robots to operate effectively in the partially unconstrained environment of manufacturing, they must be equipped with control systems that have sensory capabilities. This paper describes a control system that consists of three parallel cross-coupled hierarchies. First is a control hierarchy which decomposes high level tasks into primitive actions. Second is a sensory processing hierarchy that analyses data from the environment. Third is a world model hierarchy which generates expectations. These are compared against the sensory data at each level of the sensory processing hierarchy. Deviations between expected and observed data are used by the the control hierarchy to modify its task decomposition strategies so as to generate sensory-interactive goal-directed behavior. This system has been implemented on a research robot, using a network of microcomputers and a real-time vision system mounted on the robot wrist.