Extracting DC bus current information for optimal phase correction and current ripple in sensorless brushless DC motor drive

Brushless DC motor （BLDCM） sensorless driving technology is becoming increasingly established. However, op- timal phase correction still relies on complex calculations or algorithms. In finding the correct commutation point, the problem of phase lag is introduced. In this paper, we extract DC bus current information for auto-calibrating the phase shift to obtain the correct commutation point and optimize the control ofBLDC sensorless driving. As we capture only DC bus current information, the original shunt resistor is used in the BLDCM driver and there is no need to add further current sensor components. Software processing using only simple arithmetic operations successfully accomplishes the phase correction. Experimental results show that the proposed method can operate accurately and stably at low or high speed, with light or heavy load, and is suitable for practical applications. This approach will not increase cost but will achieve the best performance/cost ratio and meet market expectations.     

Appropriateness of communications media use in organizations: situation requirements and media characteristics

The purpose of this paper is to examine media use in organizations as affected by situation requirements and media characteristics. This paper discusses the strength of four existing models describing communications media use in individuals and organizations. The paper also presents research which evaluated interactions of multiple situation variables affecting communications media appropriateness in a survey population. Participants rated die acceptability of each of twelve communications media in each of eight hypothetical organizational situations. Situations varied based on high or low levels of three factors: message urgency, amount of message content, and distance between communicators. Results indicated (1) situations have unique and significant contributions to media appropriateness; (2) appropriateness of media usage depends on the match between situation requirements and media characteristics, and (3) situation effects are more salient in some 'situation-dependent' media. Another survey of 1072 voice mail users confirmed die validity and reliability of these results.     

Mixed H2/H∞ fuzzy output feedbackcontrol design for nonlinear dynamic systems: an LMI approach

This study introduces a mixed H₂/H_∞ fuzzy output feedback control design method for nonlinear systems with guaranteed control performance. First, the Takagi-Sugeno fuzzy model is employed to approximate a nonlinear system. Next, based on the fuzzy model, a fuzzy observer-based mixed H₂/H_∞ controller is developed to achieve the suboptimal H₂ control performance with a desired H_∞ disturbance rejection constraint. A robust stabilization technique is also proposed to override the effect of approximation error in the fuzzy approximation procedure. By the proposed decoupling technique and two-stage procedure, the outcome of the fuzzy observer-based mixed H₂/H_∞ control problem is parametrized in terms of the two eigenvalue problems (EVPs): one for observer and the other for controller. The EVPs can be solved very efficiently using the linear matrix inequality (LMI) optimization techniques. A simulation example is given to illustrate the design procedures and performances of the proposed method     

An image authentication scheme based on digital watermarking and image secret sharing

This paper presents an image authentication scheme that can verify the origin of the received image and, moreover, detect if the image has been tampered with. The underlying technologies of the scheme are digital watermarking and image secret sharing. Different from other schemes that use one piece of watermark information for one purpose and a different piece for another, the watermark information used for original verification is also utilized for tamper detection. Moreover, unlike other schemes that employ a fixed strength value for embedding watermarks, the scheme automatically utilizes two different strength values, one for flat regions and the other for complex regions. The experimental results prove that using different strength values increases the robustness of the watermark with little sacrifice in image quality. The results also demonstrate the effectiveness of the scheme for the origin verification as well as the tamper detection.     

Use of active control algorithm for optimal design of base-isolated buildings against earthquakes

This study presents a new design method that concurrently determines the stiffness and damping coefficient in a base isolation system. This design method is developed based on the similarity between the active and passive control system. Then, the stiffness and damping coefficient are derived from the linear quadratic regulator control algorithm to a single degree of freedom superstructure and formed as a function of single weighting. The best design of a base isolation system is determined by optimizing this weighting from the minimum H_∞-norm responses of base displacement and roof acceleration. A parametric study is performed to understand the influence of superstructures to the resulting optimized base isolation system. Moreover, this study also provides a numerical example to validate the optimal design of base isolation systems. The potential to design nonlinear lead-rubber bearings with added viscous dampers based on the proposed method is also investigated. As a result, the proposed method yields a high-performance base isolation system for a known superstructure.     

Robust path tracking control of mobile robot via dynamic petri recurrent fuzzy neural network

This study focuses on the design of robust path tracking control for a mobile robot via a dynamic Petri recurrent fuzzy neural network (DPRFNN). In the DPRFNN, the concept of a Petri net (PN) and the recurrent frame of internal feedback loops are incorporated into a traditional fuzzy neural network (FNN) to alleviate the computation burden of parameter learning and to enhance the dynamic mapping of network ability. This five-layer DPRFNN is utilized for the major role in the proposed control scheme, and the corresponding adaptation laws of network parameters are established in the sense of projection algorithm and Lyapunov stability theorem to ensure the network convergence as well as stable control performance without the requirement of detailed system information and the compensation of auxiliary controllers. In addition, the effectiveness of the proposed robust DPRFNN control scheme is verified by experimental results of a differential-driving mobile robot under different moving paths and the occurrence of uncertainties, and its superiority is indicated in comparison with a stabilizing control system.     

A consensus sampling technique for fast and robust model fitting

In this paper, a new algorithm is proposed to improve the efficiency and robustness of random sampling consensus (RANSAC) without prior information about the error scale. Three techniques are developed in an iterative hypothesis-and-evaluation framework. Firstly, we propose a consensus sampling technique to increase the probability of sampling inliers by exploiting the feedback information obtained from the evaluation procedure. Secondly, the preemptive multiple K-th order approximation (PMKA) is developed for efficient model evaluation with unknown error scale. Furthermore, we propose a coarse-to-fine strategy for the robust standard deviation estimation to determine the unknown error scale. Experimental results of the fundamental matrix computation on both simulated and real data are shown to demonstrate the superiority of the proposed algorithm over the previous methods.     

Fuzzy tracking control design for nonlinear dynamic systems via T-Sfuzzy model

This study introduces a fuzzy control design method for nonlinear systems with a guaranteed H_∞ model reference tracking performance. First, the Takagi and Sugeno (TS) fuzzy model is employed to represent a nonlinear system. Next, based on the fuzzy model, a fuzzy observer-based fuzzy controller is developed to reduce the tracking error as small as possible for all bounded reference inputs. The advantage of proposed tracking control design is that only a simple fuzzy controller is used in our approach without feedback linearization technique and complicated adaptive scheme. By the proposed method, the fuzzy tracking control design problem is parameterized in terms of a linear matrix inequality problem (LMIP). The LMIP can be solved very efficiently using the convex optimization techniques. Simulation example is given to illustrate the design procedures and tracking performance of the proposed method     

On the thermal annealing conditions for self-synthesis of tungsten carbide nanowires from WC(x) films

The thermal annealing conditions in nitrogen ambient for the self-synthesis of tungsten carbide nanowires from sputter-deposited WC(x) films were investigated. Experimental results show that the temperature window for the growth of nanowires lies in the range of 500-750?°C with the corresponding annealing time interval ranging from 2.5 to 0.25?h. The diameter, length, and density of the grown nanowires are in the range of 10-15?nm, 0.1-0.3?μm, and 210-410?μm(-2), respectively. The degree of carbon depletion in the annealed WC(x) films plays a crucial role in determining both the shape and density of the self-synthesized nanowires. Nanowires synthesized at lower temperatures were seen to be smaller in dimension but higher in density. Material analysis reveals that the phase transition from WC to W(2)C arising from decarburization of the WC(x) film during thermal annealing should be responsible for the self-synthesis of nanowires.     

Effect of Synthesis pH and H2O Molar Ratio on the Structure and Morphology of Aluminum Phosphate (AlPO-5) Molecular Sieves

AlPO-5 molecular sieves were prepared by the hydrothermal reaction of a gel mixture with the following compositions: Al₂O₃ : P₂O₅ : Et₃N : H₂O = 1:1:1.5:x, where x is between 100 and 750 H₂O molar ratio. The structure and morphology of the AlPO-5 molecular sieves depend on the gel mixture's composition, hydrothermal temperature, hydrothermal reaction time, and pH. Without pH control, the AlPO-5 structure changed from a spherical shape at H₂O = 100 to a hexagonal pillar shape at H₂O = 450. With pH control in the range of about 2.5-3.5, the hexagonal pillar crystals began to form at H₂O = 100 and an island of hexagonal pillars with radiation form appeared at H₂O = 300-450 due to the formation of a tridymite type of dense AlPO₄ phase. It appears that the formation rate of hexagonal pillar crystals to form a dense AlPO₄ phase is favorable under acidic conditions, and an amorphous AlPO-5 structure forms under basic conditions. Thus, the H₂O concentration and pH value have a dramatic effect on the AlPO-5 structure.