It is shown that the problem of observer design for estimating a set of linear combinations of state variables of a plant can be formulated in terms of linear matrix inequalities. An algorithm for constructing functio...
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It is shown that the problem of observer design for estimating a set of linear combinations of state variables of a plant can be formulated in terms of linear matrix inequalities. An algorithm for constructing functional observers is proposed based on a nonsingular transformation of a plant model in the state space by matrix canonization with subsequent solution of the system of linear matrix inequalities.
Optimal design of experiments for correlated processes is an increasingly relevant and active research topic. Present methods have restricted possibilities to judge their quality. To fill this gap, we complement the v...
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Optimal design of experiments for correlated processes is an increasingly relevant and active research topic. Present methods have restricted possibilities to judge their quality. To fill this gap, we complement the virtual noise approach by a convex formulation leading to an equivalence theorem comparable to the uncorrelated case and to an algorithm giving an upper performance bound against which alternative design methods can be judged. Moreover, a method for generating exact designs follows naturally. We exclusively consider estimation problems on a finite design space with a fixed number of elements. A comparison on some classical examples from the literature as well as a real application is provided.
A new design algorithm is presented for a symmetric universal vector quantiser based on the successive partitioning of normalised signal space. The universal vector quantiser of video signals is also shown as an example.
A new design algorithm is presented for a symmetric universal vector quantiser based on the successive partitioning of normalised signal space. The universal vector quantiser of video signals is also shown as an example.
A design algorithm, based on the exchanging search technique, was used for optimizing the visible antireflection coating design of substrates with refractive indices ranging from 1.45 to 1.784. In this method, a tunin...
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A design algorithm, based on the exchanging search technique, was used for optimizing the visible antireflection coating design of substrates with refractive indices ranging from 1.45 to 1.784. In this method, a tuning operation for the layer thicknesses of a two-material multilayer assembly was first carried out, followed by an exchanging operation for further refining the visible antireflection performance and simplifying the design structure. The average visible reflectivities of two-material thirty-layer exchanging search universal antireflection coating designs for a set of eight different substrates with indices 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75 and 1.784 were reduced to approximately 0.172-0.174% with 12-14 layer structures.
We report on the wavelength-multiplexing diffractive phase element (WMDPE) capable of generating independent spot patterns for different wavelengths. The iterative method proposed by Bengtsson [Appl. Opt. 37, 1998] fo...
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We report on the wavelength-multiplexing diffractive phase element (WMDPE) capable of generating independent spot patterns for different wavelengths. The iterative method proposed by Bengtsson [Appl. Opt. 37, 1998] for designing a kinoform that produces different patterns for two wavelengths is extended to the WMDPE for multiple wavelengths (more than two wavelengths). Effectiveness of the design algorithm is verified by design and computer simulations on the WMDPE's for four and nine wavelengths, The WMDPE for three wavelengths (441.6, 543.5. and 633 nm) is designed with five phase levels and is fabricated by electron-beam lithography. We observed that the individual spot patterns are reconstructed for the design wavelengths correctly. Performance of the WMDPE is evaluated by computer simulations on the uniformity error. the light efficiency, and the contrast. On the basis of the results, the characteristics of the WMDPE's are discussed in terms of various conditions of fabrication and usage. (C) 2001 Optical Society of America.
High-altitude test facilities are usually used to evaluate the performance of space mission engines. The supersonic exhaust diffuser, a main part of high-altitude test facility, provides the required test cell vacuum ...
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High-altitude test facilities are usually used to evaluate the performance of space mission engines. The supersonic exhaust diffuser, a main part of high-altitude test facility, provides the required test cell vacuum conditions by self-pumping the nozzle exhaust gases to the atmosphere. However, the plume temperature is often much higher than the temperature the diffuser structure is able to withstand, usually above 2500 K. In this study, an efficient cooling system is designed and analyzed to resolve the thermal problem. A water spray cooling technique is preferred among various existing techniques. Here, a new algorithm is developed for a spray cooling system for a supersonic exhaust diffuser. This algorithm uses a series of experimental and geometrical relationships to resize the governing parameters and remove the required heat flux from the diffuser surface. The efficiency of the newly designed cooling system is evaluated via numerical simulations. The utilized numerical technique is based on the discrete-phase method. Various computational studies are accomplished to enhance the accuracy of numerical prediction and validation. The present numerical study is validated using experimental results. The results show that the realizable k-e method is superior compared to other Reynolds-averaged Navier-Stokes models.
A novel technique is presented for the design and optimization of waveguide antenna arrays based on overlapping subarrays for limited field-of-view (FoV) applications. Each subarray consists of one directly fed antenn...
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A novel technique is presented for the design and optimization of waveguide antenna arrays based on overlapping subarrays for limited field-of-view (FoV) applications. Each subarray consists of one directly fed antenna element and several passive reactive-loaded elements. The proposed overlapping scheme exploits a free-space reactive coupling instead of more conventional schemes based on complex beamforming networks. This results in a drastic reduction in the number of waveguide components required in the feeding network. The optimization of the considered class of array structures using a full-wave electromagnetic (EM) solver is extremely time-consuming even in the presence of subarrays with a reduced number of passive elements. To overcome this limitation, an effective semi-analytical design algorithm has been specifically developed. Using this algorithm, a novel subarray structure with a predefined pulse-shaped radiation pattern was synthesized. The designed subarray is inherently matched and features reduced spurious EM coupling level with adjacent subarray elements. In particular, the analysis of an array consisting of 38 such subarray elements has been carried out with the main goal of illustrating the effect of the subarray pattern on the total array characteristics. To validate the subarray overlapping scheme, an array composed of three contiguous subarrays has been realized and measured experimentally. In this way, a scan range in the FoV [-4 degrees;4 degrees] with 15 dB grating lobe suppression has been demonstrated.
In multi-n-phase machines, the n-phases are grouped in separated stars. A particular subcategory of multi-n-phase machines is the multi-3-phase machines. This study presents the design considerations and their validat...
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In multi-n-phase machines, the n-phases are grouped in separated stars. A particular subcategory of multi-n-phase machines is the multi-3-phase machines. This study presents the design considerations and their validation for tooth coil wound multi-3-phase machines. A generic algorithm to design multi-3-phase machines is proposed. Although this study mainly focuses on multi-3-phase machines the approach is generalised and is applicable to any multi-n-phase machine. The resulting machines exhibit a low torque ripple value, and a mathematical formulation is proposed in order to justify this behaviour. All the multi-3-phase machines designed according to the proposed algorithm can be studied, and directly compared, thanks to the generalised harmonic formulation of the stator MMF and the torque performances here proposed. This study is enriched with some design hints useful to realise a machine with low mutual coupling between phases, and some considerations that can help the machine designer in the choice of the number of poles. The design algorithm is applied for the design of a triple-3-phase PM-inset machine solution, with nine slots ten poles. The performances, evaluated by finite element analysis and experimental analysis, demonstrate the effectiveness of the design algorithm proposed in a very simple structure machine.
The authors propose a technique for designing IIR (infinite impulse response) digital filters to have an arbitrary log magnitude frequency response. The technique is based on an iterative weighted least-squares (WLS) ...
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The authors propose a technique for designing IIR (infinite impulse response) digital filters to have an arbitrary log magnitude frequency response. The technique is based on an iterative weighted least-squares (WLS) approach in the frequency domain. A weight updating procedure is introduced to obtain a nearly optimal approximation to the given log magnitude function in the least-squares sense. The weighting function is updated using the results of the previous iteration in such a way that the weighted error approximates the log magnitude error. Filter coefficients at each iteration are efficiently computed using a fast recursive algorithm for a set of linear equations derived from the WLS problem. Several design examples demonstrate the rapid convergence of the design algorithm. The algorithm is extended to equiripple approximation by means of a minor modification of the weight updating procedure.
We designed a universal broadband visible antireflection coating for glass substrates with refractive indices ranging from 1.45 to 1.90 by a jumping search technique. The jumping search algorithm, based on the searche...
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We designed a universal broadband visible antireflection coating for glass substrates with refractive indices ranging from 1.45 to 1.90 by a jumping search technique. The jumping search algorithm, based on the searches of layer-thickness jump tuning and layer jump elimination, was used to refine the mean visible antireflection performance and simplify the design structure of a multilayer system. It was shown that the universal visible antireflection coating designs for a set of 10 different substrates with the refractive indices of 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, and 1.90, obtained by different types of Jumping search of a two-material 50-layer system, were reduced to 18-22-layered structures and their total average universal visible reflectivities reduced to approximately 0.307-0.309% were acceptable.
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