Quantitative speed control for SRM drive using fuzzy adapted inverse model

Quantitative and robust speed control for a switched reluctance motor (SRM) drive is considered to be rather difficult and challenging owing to its highly nonlinear dynamic behavior. A speed control scheme having two-degree-of-freedom (2DOF) structure is developed here to improve the speed dynamic response of an SRM drive. In the proposed control scheme, the feedback controller is quantitatively designed to meet the desired regulation control requirements first. Then a reference model and a command feedforward controller based on an inverse plant model are employed to yield the desired tracking response at nominal case. As the variations of system parameters and operating conditions occur, the prescribed control specifications may not be satisfied any more. To improve this, the inverse model is adaptively tuned by a fuzzy control scheme so that the model-following tracking error is significantly reduced. In addition, a simple disturbance cancellation robust controller is added to improve the tracking and regulation control performances further.     

High-resolution multiple target angle tracking

An approach to high-resolution multiple-target-angle tracking that uses the output of an array of sensors is presented. The results of direction-of-arrival estimation by eigenstructure analysis are extended to derive a recursive procedure for tracking moving sources. This procedure involves recursive eigenvalue decomposition and a zero-tracking algorithm, using the coefficient derived from the minimum-norm criterion. The algorithm has superresolution capability in that a pair of closely spaced target angles can be resolved and tracked even though the angular separation between them is less than the reciprocal of the aperture size. Simulation results verify that the algorithm works well in tracking multiple-target sources     

High-acceleration mass drivers

After testing an early, simplified mass-driver (35 gravity acceleration) a second, designated MD2, was designed and is now operating. MD2 is of axial geometry, with individually powered drive coils of 13.1 cm diameter. Timing is derived through the interruption of light beams by the moving armature (bucket). Electric power is provided by the resonant discharge of sector capacitor banks through silicon-controlled rectifiers in a two-phase, quadrature circuit. The bucket flies in vacuum, guided by passive dynamic eddy-current magnetic forces, those currents flowing in strip conductors lining the inside of a nonconducting vacuum pipe. The initial length of MD2 is 2.5 m, divided equally into acceleration and deceleration. Nominal acceleration is 5000 m/sec². For routine testing an ohmic bucket is used. Quantitative measurements are obtained with a solid bucket carrying two superconducting coils with a current density of 25 kA/cm². A cryogenic station for cooling the bucket to liquid helium temperature is connected to the vacuum pipe. The test program, now begun, will concentrate on guidance and acceleration forces, measurement of drive shielding losses, and possible couplings of drive forces into modes of oscillation.     

Inactivation probability of heavy ion-irradiated Bacillus subtilis spores as a function of the radial distance to the particle's [correction of paricle's] trajectory.

The understanding of the radiobiological action of heavy ions requires the knowledge of the dependence of the inactivation probability on the distance between the particle's trajectory and the biological test organism (the impact parameter). Spores of Bacillus subtilis with a cytoplasmic core of about 0.22 micrometer cross section are suitable test objects for the study of this radial inactivation probability in its microscopic details. The spores are irradiated at low fluences of some 10(6) ions/cm2 with very heavy ions at different specific energies up to 10 MeV per atomic mass unit u while in fixed contact with visual nuclear track detectors. The methods are described by which the biological response of individual cells can be evaluated and the impact parameter be determined with an accuracy typically better than 0.2 micrometer. The results demonstrate that the common characteristics of inactivation, e.g., an effective range of inactivation extending to at least 3 micrometers, a nonmonotonic dependence of the inactivation probabilities on the radial distance, and the fact that the inactivation probability even for direct central hits on the cytoplasmic core is substantially below one, are nearly independent of the particle energy and type. The results are incompatible with the assumption that the radiobiological effectiveness can be attributed to the dose of secondary electrons as currently understood. They also demonstrate that the widely held notion of an "overkill" at low impact parameters does not apply for the spores even with the most densely ionizing ions.     

Implicit Adaptive Control for a Class of MIMO Systems

Two implicit model reference adaptive control algorithms for multi-input multi-output systems are developed. These algorithms do not require either satisfaction of the perfect model following conditions or explicit parameter identification. The first algorithm ensures asymptotic stability of the output error provided that the output stabilized plant transfer matrix is strictly positive real. The second algorithm guarantees a bounded error under less restrictive conditions. The algorithms are applied to the lateral axis of an F-8 aircraft.     

Intrepid digital microwave. A new approach to bistatic radar

Southwest Microwave, Inc. (SMI) introduced the world's first commercially viable bistatic microwave intrusion detection sensor in 1971. Bistatic microwave has become the paradigm for high security perimeters, and SMI products have become industry standards. With the introduction of the Intrepid Digital Microwave, SMI brings the latest in Digital Signal Processing (DSP) and power and data networking to this proven sensor technology     

Welcome Address

Space Science Reviews -     

Common-Mode Noise Generation in a DC-to-DC Converter

Analytical and experimental considerations of the common-mode noise in a dc-to-dc connverterare discussed. Analyzing the mechanism of the common-mode noise generation by means of a high-frequency equivalent circuit, we estimate the output noise voltage generated during the transistor's turn-on time. This commonmode noise consists mainly of two frequency components distributed in several megahertz. The effects of parasitic parameters on the noise voltage and frequencies are clarified. In addition, the effect of a common-mode choke on the noise suppression is discussed experimentally.     

Satellite observations of power line harmonic radiation

In-situ spectral observations of power-line harmonic radiation (PLHR) are still quite rare and almost all the detailed characteristics have been derived from studies at Antarctic stations such as Siple and Halley, and their conjugates in North America. Because of the lack of more direct satellite evidence of PLHR and the difficulties in interpretation of morphological studies, such as those of Ariel 3 and 4, there is considerable controversy concerning the relative importance of PLHR and its contribution to wave-particle interactions (WPI) in the magnetosphere. The early Ariel 3 and 4 global surveys indicated that, in terms of true mean wave energy, there is no longitudinal localisation, the contribution of world-wide intense VLF emissions, associated with magnetic storms, being dominant. Also, the most intense wave emission, that of plasmaspheric hiss at ELF (< 1 kHz) exhibits little evidence of localisation. The PLHR phenomenon is most conspicuous by its persistence in quiet times (Kp ≤ 2+) at 45° < Λ < 55° over North America and its conjugate region, even though the less frequent strongest emissions, to which it gives rise in the summer, are located polewards at 3 < L < 5. In the northern winter, when spheric activity over both North America and its conjugate are low, there is a high occurrence of strong discrete emissions, which are more sharply localised than in the summer, on the NE industrial U.S.A. field line. The most recent Ariel 4 studies, particularly on the spheric wavefield over North America (using data from the Appleton Laboratory impulse counters) and on the character of the wavefield over the mainland and over the Atlantic immediately to the east (where the spheric contribution is similar) throw new light on the problem. It appears that the principal role of the PLHR may be to sustain duct structure and multihop propagation which is relatively much rarer over the Atlantic. Typical industrial PLHR consists of a series of narrow pulses at twice the mains frequency. It is suggested that these ‘artificial spherics’ may help to sustain the WPI and multihop duct structure. At L = 4, Yoshida et al. (1980) have shown that there is a strong, sharp maximum for WPIs originating in spherics, at f ? 3 kHz, in good agreement with Siple observations.     

Optimum spectral bands for land cover discrimination

An experiment was undertaken to select the optimum spectral bands for the discrimination of land use/cover for proposed Indian Remote Sensing Satellite. A feature selection method was used for the discrimination analysis on the multiband data collected by Bendix 11-channel Modular Multiband Scanner over Tirupati test site of Chittoor district, Andhra Pradesh, South India. Of the various combinations of bands analysed, the optimum combination of four bands was defined as that one which provided the greatest divergence distances to discriminate the specific land covers in the test sites. On the basis of the above studies the optimum bands so chosen are 0.49–0.54 μm, 0.62–0.66 μm, 0.66–0.70 μm and 0.77–0.86 μm.