Hunt A. Sutherland

A High-Performance Pulsewidth Modulator for an Inverter-Fed Drive System Using a Microcomputer

An Intel 8086 microcomputer-based pulsewidth modulator (PWM) is described which receives digital voltage and frequency commands independently at the input, generates precision three- phase PWM waves at the output, and can be used to drive a transistor or thyristor inverter for ac drive systems. A computation intensive uniform sampling technique is used in the low-frequency region, whereas the higher frequency region is based on word recognition and pattern retrieval method. A laboratory breadboard of the modulator has been built and tested for the frequency range 0-250 Hz with resolution of 0.0077 Hz and smooth voltage variation up to square wave within a one-percent step in the whole range. The modulator has been extensively tested with a transistor inverter and hybrid computer simulated induction motor drive system and shows performance improvement over the currently available techniques.

A Microcomputer-Based Propulsion Control System of a Hybrid Electric Vehicle

This paper describes a hybrid electric vehicle drive control system under microcomputer control where the propulsion power is shared between a gasoline engine and a dc motor. The control functions have been developed, analyzed, and implemented with highlevel language in a dual Intel 8086 microcomputer system. The drive system has been integrated and tested, and shows excellent results.

A State Language for the Sequencing in a Hybrid Electric Vehicle

The application of a state language to the real-time control of a hybrid electric vehicle is explained. The state language has been developed both as a specification aid to the system designer and as a means for the programmer to produce microcomputer software. A translator program, which was developed on a VAX minicomputer, preprocesses the state language into a software module to be compiled by the standard Intel PL/M 86 compiler.

The TRAC mission manager autonomous control executive

Present autonomy technologies do not compensate for a vehicles structural, perceptual and control limitations through reflexive responses and rapid adaptation as a pilot typically does. For Uninhabited Air Vehicles (UAVs) to have more general application the mishap rates must be much reduced. Therefore the vehicle control systems must be capable of rigorously analyzing and predicting in real-time, component failures and other disturbance effects to determine the appropriate response much as a pilot does. The purpose of the Reliable Autonomous Control Technology (REACT) program, a jointly-developed mission management architecture by Lockheed Martin Aeronautics, General Electric, NASA Dryden, and Jet Propulsion Lab., is to autonomously accomplish this complex mission and subsystem management task. Based on prior analysis of recent UAV data, the Autonomous Control Executive (ACE) could play a role in preventing up to about 36% of these mishaps. We describe the ACE that would be part the Mission Management architecture and some initial results from rapid prototype of the architecture implemented using a PC based simulator.

OASIS: A Service-Oriented Architecture for Dynamic Instrumentation of Enterprise Distributed Real-Time and Embedded Systems

Performance analysis tools for enterprise distributed real-time and embedded (DRE) systems require instrumenting heterogeneous sources (such as application- and system-level hardware and software resources). Traditional techniques for software instrumentation of such systems, however, are tightly coupled to system design and metrics of interest. It is therefore hard for system testers to increase their knowledge base and analytical capabilities for enterprise DRE system performance using existing instrumentation techniques when metrics of interest are not known during initial system design. This paper provides two contributions to research on software instrumentation for enterprise DRE systems. First, it presents OASIS, which is service-oriented middleware for instrumenting enterprise DRE systems to collect and extract metrics without design time knowledge of which metrics are collected. Second, this paper empirically evaluates OASIS in the context of a representative enterprise DRE system from the domain of shipboard computing. Results from applying OASIS to a representative enterprise DRE system show that its flexibility enables DRE system testers to precisely control the overhead incurred via instrumentation.

DEPENDABLE SOFTWARE IN RAILWAY SIGNALLING

Abstract Railway signalling software and safety requirements are summarized, and three short examples of the application of new methods to the assurance of dependability are provided. The strengths and shortcomings of existing methods relative to application needs are illustrated. The analogy between railway signalling and other distribution processes in manufacturing and supply chain management is noted.