A Methodology for Integrating Sensor Feedback in Machine Tool Controllers

A reference model architecture for real-time hierarchical control systems has been proposed by researchers at the National Institute of Standards and Technology, and has been implemented on a variety of computing platforms for manufacturing and vehicle control applications. A fundamental aspect of this architecture is the notion of nested control loops, which incorporate sensory feedback in a hierarchy whose cycle times decrease in frequency as planning becomes more abstract. The nested control loops provide a hierarchy in which to model command and control. This architecture was formalized during work with the National Aeronautics and Space Administration on the Flight Telerobot Servicer for the space station, and is known as the NASA/NBS Standard Reference Model, or NASREM. Although NASREM was intended to serve as a guideline for space application robot control, it has applicability to a wide range of real-time control applications. This paper adapts the NASREM reference model architecture to a machine tool control model. A computational architecture will be presented that describes expected behavior at each layer. A functional analysis will outline a baseline task tree vocabulary. The task tree vocabulary is given by a set of command verbs for each layer and is a critical component of task description within a hierarchical control system.