Constant-current versus constant-voltage VCM drive analysis

A voice-coil-motor (VCM)-driven actuator is analyzed for both constant-current and constant-voltage drive operation. Through the use of dimensional analysis, the solutions to the two drive methods are directly compared. This allows for quick evaluation of an actuator design. The analysis compares the actuator performance parameters, including seek time, switching time, and maximum angular velocity. The relationship between constant-current and constant-voltage drive is shown to depend on the value of a dimensionless parameter. For actuators with low values of this parameter (<1.43), the current is not back-EMF limited when constant-voltage drive is used. It is shown that such actuators have the same seek time for the same average power dissipated in the coil, regardless of which drive approach is chosen. Therefore, a single equation was derived to describe power generated at the source for both constant-current and constant-voltage drives. The ratio of average power generated at the source average power dissipated in the coil is equal to the ratio of source voltage to stall voltage. A given actuator dissipating the same power in the coil will always have a lower stall voltage and a higher peak voltage if constant-current drive is used instead of constant-voltage drive     

Parallel N-ary speculative computation of simulated annealing

Simulated annealing is known to be an efficient method for combinatorial optimization problems. Its usage for realistic problem size, however, has been limited by the long execution time due to its sequential nature. This report presents a practical approach to synchronous simulated annealing for massively parallel distributed-memory multiprocessors. We use an n-ary speculative tree to execute n different iterations in parallel on n processors, called generalized speculative computation (GSC). Execution results of the 100- to 500-city traveling salesman problems on the AP1000 massively parallel multiprocessor demonstrate that the GSC approach can be an effective method for parallel simulated annealing as it gave over 20-fold speedup on 100 processors     

Error Analysis of Camera Movements in Stereo Vehicle Tracking Systems

In an outdoor navigational environment, cameras of an autonomous vehicle or robot are subjected to uncontrollable movements relative to the vehicle or robot body. In this paper, the effect of such camera movements in stereo vision-based vehicle tracking systems is analyzed. In other words, it is shown how the computation of the range and heading angle of a lead vehicle is affected as a result of camera movements. The parameter space of the stereo system is divided into a controllable subspace consisting of the baseline and an uncontrollable subspace consisting of relative camera movements and the coordinates of a tracked point on the lead vehicle. The optimal baseline value with respect to the uncontrollable subspace is found by employing the mini-max and minimum mean-squared error estimators. The mini-max estimator is used to obtain the worst case performance while the minimum mean-squared estimator is used to obtain the average performance. Based on this analysis, it is shown how an optimal imaging geometry for a stereo vision-based vehicle tracking system can be designed in order to have the least amount of range and heading angle errors.     

Design and Implementation of a Ubiquitous Robotic Space

This paper describes a concerted effort to design and implement a robotic service framework. The proposed framework is comprised of three conceptual spaces: physical, semantic, and virtual spaces, collectively referred to as a ubiquitous robotic space. We implemented a prototype robotic security application in an office environment, which confirmed that the proposed framework is an efficient tool for developing a robotic service employing IT infrastructure, particularly for integrating heterogeneous technologies and robotic platforms.     

Vision-based arm gesture recognition for a long-range human–robot interaction

This paper proposes a vision-based human arm gesture recognition method for human–robot interaction, particularly at a long distance where speech information is not available. We define four meaningful arm gestures for a long-range interaction. The proposed method is capable of recognizing the defined gestures only with 320×240 pixel-sized low-resolution input images captured from a single camera at a long distance, approximately five meters from the camera. In addition, the system differentiates the target gestures from the users’ normal actions that occur in daily life without any constraints. For human detection at a long distance, the proposed approach combines results from mean-shift color tracking, short- and long-range face detection, and omega shape detection. The system then detects arm blocks using a background subtraction method with a background updating module and recognizes the target gestures based on information about the region, periodical motion, and shape of the arm blocks. From experiments using a large realistic database, a recognition rate of 97.235% is achieved, which is a sufficiently practical level for various pervasive and ubiquitous applications based on human gestures.     

Thermodynamic study on the effect of CaF2 on the nitrogen and carbon solubility in the CaO-Al2O3-CaF2 slag system

The nitrogen and carbon solubilities in the CaO-Al₂O₃-CaF₂ slag system at 1723K were measured to understand the effect of CaF₂ on the nitrogen and carbon dissolution behaviour using thermochemical equilibration technique. The nitride capacity in the CaO_satd.-Al₂O₃-CaF₂ system was constant until X_Al2O₃ / X_CaF2 = 0.23, followed by decrease with an increase in X_Al2O₃ / X_CaF2 ratio, and then showed a constant value. The carbide capacity in the CaO_satd.-Al₂O₃-CaF₂ system also showed the similar behaviour to the nitride capacity, however, the effect of CaF₂ on the activity coefficient of nitride and carbide ions showed some differences in case of X_CaF2 = 0.2. The effect of CaF₂ on the activity coefficient of carbide and nitride ions would not be significant in case of CaO-rich region of X_CaO / X_CaF2 = 0.31. However, CaF₂ could be expected to affect the activity coefficient of each ion in case of the Al₂O₃-rich region, causing compensating effect of the incorporated nitride (carbide) mechanism. The relationship between nitride and carbide capacity was also discussed.     

Fuzzy QFD for supply chain management with reliability consideration

Although many products are made through several tiers of supply chains, a systematic way of handling reliability issues in a various product planning stage has drawn attention, only recently, in the context of supply chain management (SCM). The main objective of this paper is to develop a fuzzy quality function deployment (QFD) model in order to convey fuzzy relationship between customers needs and design specification for reliability in the context of SCM. A fuzzy multi criteria decision-making procedure is proposed and is applied to find a set of optimal solution with respect to the performance of the reliability test needed in CRT design. It is expected that the proposed approach can make significant contributions on the following areas: effectively communicating with technical personnel and users; developing relatively error-free reliability review system; and creating consistent and complete documentation for design for reliability.     

Effect of inter-ionic interaction on photoluminescence property of yttrium aluminate garnet phosphors

The photoluminescence of Terbium-activated yttrium aluminate with the general formula Y_3-xTb_XAl₅O₁₂was investigated as a function of Tb³⁺concentration. The main attention is focused on the ⁵D₃/⁵D₄fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb³⁺concentration and analyzed in view of the application for plasma display panel (PDP). Also, the diffuse reflectance spectra were measured and analyzed in the range from VUV to UV. As a result, the yttrium aluminate was found to have a broad excitation band extending from VUV to UV range and to show the typical concentration quenching behaviors both for ⁵D₃and ⁵D₄fluorescence. The energy transfer was investigated by analyzing the decay curve of ⁵D₃and ⁵D₄emission based on the multipolar interaction or the exchange interaction. The decay curves of ⁵D₃emission, for which well known cross relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula based on the direct quenching scheme. The decay curves of ⁵D₄emission were analyzed by Yokota and Tanimoto's formula based on the diffusion limited quenching scheme.