Parameter identification for multibody systems expressed in differential-algebraic form

The ability of a multibody dynamic model to accurately predict the response of a physical system relies heavily on the use of appropriate system parameters in the mathematical model. Thus, the identification of unknown system parameters (or parameters that are known only approximately) is of fundamental importance. If experimental measurements are available for a mechanical system, the parameters in the corresponding mathematical model can be identified by minimizing the error between the model response and the experimental data. Existing work on parameter estimation using linear regression requires the elimination of the Lagrange multipliers from the dynamic equations to obtain a system of ordinary differential equations in the independent coordinates. The elimination of the Lagrange multipliers may be a nontrivial task, however, as it requires the assembly of an orthogonal complement of the Jacobian. In this work, we present an approach to identify inertial system parameters and Lagrange multipliers simultaneously by exploiting the structure of the index-3 differential-algebraic equations of motion.     

Spatio‐temporal scanning backlight mode for field‐sequential‐color optically‐compensated‐bend liquid‐crystal display

Abstract— A spatially and temporally scanning backlight consisting of ten isolated micro‐structured light guides has been developed to be combined with a fast‐response optically‐compensated‐bend‐mode field‐sequential‐color LCD in which the liquid‐crystal cell does not contain color filters. The sequential fields of three primary colors are generated by illumination of the red‐, green‐, and blue‐light‐emitting diodes, each illuminating for one‐half of the field, resulting in a luminance of 200 cd/m² for the LCD. The effect of light leakage between the blocks in the scanning backlight in field‐sequential‐color applications was measured and will be described.     

差动式平面精密角度定位控制研究

精密角度定位是X-Y-θ三自由度平面精密定位的关键,为了在保证定位精度的前提下提高角度定位速度,在李萨如平面上建立RBF神经网络预测模型,由当前位置多步递推预测未来角度偏差变化,为当前高速角度定位控制提供操作指导.在定位过程中通过预测位置与实际位置比较,灵活调整定位速度;在定位误差带附近自动降为单步驱动,保证定位精度.实验达到预期效果,表明神经网络预测控制是实现高速高精度定位的有效手段.     

Spatial frequency-specific visual adaptation may cause paradoxical transient improvements in visual acuity: computer simulation and confirmatory experiments

In the visual cortex of monkeys and humans, several types of processing are conducted, such as orientation-selective edge detection. It was also reported by Campbell and associates that the cerebral visual cortex conducts processing consisting of spatial-frequency-and-orientation-specific multiple narrow-band channels. It has also been reported that spatial-frequency-and-orientation-specific visual stimuli cause adaptations in the corresponding channels, resulting in reductions of the visual sensitivity around some frequency ranges. In the course of simulation studies using Landolt rings to measure visual acuity, we found that spatial-frequency-specific adaptations would cause paradoxical transient improvements in visual acuity. We therefore conducted perceptual experiments to see if these improvements in visual acuity take place after spatial-frequency-specific visual adaptation, with positive results. These findings may be significant in designing road information boards for car drivers, because such an adaptation often occurs while driving a car. This work was presented in part at the Sixth International Symposium on Artificial Life and Robotics, Tokyo, January 15–17, 2001     

Analysis of speckle‐reduction performance in a laser rear‐projection display using a small moving diffuser

Abstract— Recently, a practical method of speckle reduction in laser rear‐projection displays that uses an optical system with a small moving diffuser has attracted much attention. In this paper, a model of the speckle generation and reduction mechanism in the system is presented. Speckle in the system was investigated, focusing on the physical aspects of its generation rather than treating it statistically, and it was found that the granularity of the speckle patterns generated by the small diffuser corresponded to the size of the coherent regions on the projection screen. This determined the efficiency of the speckle reduction when the small diffuser was rotated. By using these results, a method to estimate the performance of speckle reduction on the system was developed.     

A high‐contrast front‐projection display system optimizing the projected light‐angle range

Abstract— The problem with front‐projection displays is that the screen contrast ratio decreases under bright‐ambient conditions. To overcome this problem, the design of a special screen, composed of the diffuser whose diffusing property shows top‐hat characteristics and a sawtooth reflector, is proposed. The screen diffuses the incident image light arriving at a projection‐angle range that is a lower‐angle range than the viewing‐angle range, and reflects the ambient light out of the viewing‐angle range. In this paper, the projection‐angle range and the viewing‐angle range was optimized to improve the contrast ratio of a front‐projection display. As a result, a special screen with the above‐mentioned diffusing property was realized, and a high‐quality front‐projection display with a high contrast ratio, even in a bright room, was achieved.     

Some properties of four-dimensional parallel Turing machines

Informally, the parallel Turing machine (PTM) proposed by Wiedermann is a set of identical usual sequential Turing machines (STMs) cooperating on two common tapes: a storage tape and an input tape. Moreover, STMs which represent the individual processors of a parallel computer can multiply themselves in the course of computation. On the other hand, during the past 7 years or so, automata on a four-dimensional tape have been proposed as computational models of four-dimensional pattern processing, and several properties of such automata have been obtained. We proposed a four-dimensional parallel Turing machine (4-PTM), and dealt with a hardware-bounded 4-PTM in which each side-length of each input tape is equivalent. We believe that this machine is useful in measuring the parallel computational complexity of three-dimensional images. In this work, we continued the study of the 3-PTM, in which each side-length of each input tape is equivalent, and investigated some of its accepting powers.     

Active and Reactive Power Control Techniques Based on Feedback Linearization and Fuzzy Logic for Three‐Phase Grid‐Connected Photovoltaic Inverters

This paper discusses two techniques based on the feedback linearization (FBL) method to control the active and reactive output powers of three‐phase grid‐connected photovoltaic (PV) inverters. The first control scheme is an application of the direct FBL approach. The other is an appropriate combination of the FBL and fuzzy logic (FBL‐FL), and is the main proposed method of this study. Wherein, a unique fuzzy logic controller (FLC) is designed to enhance effectiveness of the linear control method used in the direct FBL. In detail, its major objectives are to improve the transient response and reduce steady‐state oscillations in the output powers. In this research, the illustrative PV inverter utilizes a three‐level DC‐AC converter, an R‐L filter and a 250 V/10 kV wye‐wye transformer to inject the energy, obtained from PV array with a nominal power of 100 kW, into the 10 kV/60Hz three‐phase grid. Numerical simulations in MATLAB and PSIM illustrate that the two FBL‐based structures perform very well in independently regulating the active and reactive output powers to the reference values, even within the parametric uncertainties and the unbalanced grid voltage condition. Moreover, comparisons of simulation results, obtained from the traditional proportional–integral (PI) control and the two FBL‐based structures, show advantages of the proposed FBL‐FL hybrid technique in terms of fast response, small overshoot, acceptable steady‐state fluctuation and high robustness.     

Synthesis of LaB6 from BN and lanthanum-citrate-hydrate

Lanthanum hexaboride was synthesized by reacting a powdered mixture of hexagonal boron nitride and lanthanum-citrate-hydrate carbonized substance which had been prepared by heating lanthanum-citrate-hydrate at 1000° C in a nitrogen atmosphere. The optimum conditions for the synthesis were a ratio of boron to lanthanum in the starting mixture between 5.0 and 6.0 with heating in the temperature range 1480 and 1600° C in an evacuated atmosphere.