width modulation, are described and qualitatively compared. With the employment of MOS Controlled Thyristors (MCT) in these inverters, the pulse width modulation control technique is preferred. Both quantitative and qualitative analyses are presented. The series-parallel inverter has potential application where the ratio of peak power average power demand is not large (not greater than 4:1). For the pulse power applications with large ratios of peak power/average power demand, the hybrid resonant inverter is best suited. The parallel resonant inverter is reserved for those applications which have severe short circuit requirements. For DC/DC power conversion, the pulse width modulated series, parallel and series-parallel resonant topologies are presented. Again, both quantitative and qualitative analyses are performed. These analyses show that the series resonant converter is suitable for all applications except low voltage, high current outputs. For low voltage and high current outputs, the seriesparallel converter is preferred. For AC/DC power conversion, two new converter configurations (Type-1 and Type-2) employing CAL's proprietary design are introduced. These converters convert high frequency AC voltage to controlled DC voltage by using a single conversion stage and draw close to sinusoidal input current with a near unity power factor. This results in the highest efficiency and lowest mass. The Type-1 converter is suitable for the lower range of high power application (up to approximately 1 kW). However, the Type-2 converter is best suited for higher power ratings. (Paper number IAF-ICOSP89-6-5.) 6-6. Real-time Symbolic Inference & Control for a Space Station Type Power System J. H. Painter & E. Glass Department of Electrical Engineering, Texas A&M University, College Station, TX 77843- 3128, USA (Tel: 409-845-7441). This paper presents results of research to develop combined real-time symbolic and numerical processing architectures for purposes of diagnostics and control of dynamic systems. Previous developments are extended and applied to the control of generation and loads for an electrical power system of the type used aboard the IOC Space Station. Results are demonstrated for a discrete Monte Carlo simulation of a configuration of minimum complexity. The simulation embodies two phase-regulated 20-KHz alternators, several pi-section transmission line emulations, and a variety of distributed loads. The control strategy hinges on symbolic inference of system ‘state', including load requests, and indirect management of a high-speed ‘hard-wired' numerical controller. The Symbolic Controller is loosely coupled to the controlled system via ‘message passing'. Generator management is effected by control of tuning parameters in the Numerical Controller. Load management is effected through exercise of rules concerning load priority. The realized Symbolic Controller operates as an expert system. Symbolic inference and control is achieved using object-oriented programming for realization of the Symbolic Controller shell (inference engine), which is programmed in LIPS. Two-way asynchronous communication is implemented between the LISP Controller and the emulated dynamic power system, which is programmed in C. The LISP and C modules run as concurrent processes. Simulation results are produced graphically. (Paper number IAF-ICOSP89-6-6.) 6-8. Satellite Attitude Control Through Solar Radiation: A New Approach K. Kumar Department of Aeronautical Engineering, Indian Institute of Technology, Kanpur-208016, India. The precise satellite pointing is of considerable importance for successfully accomplishing the scientific and technological space mission objectives. Numerous methods have been proposed for
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