Simulation based considerations in placement of capacitors near a dynamic voltage restorer

This paper addresses issues of capacitor placement in power distribution systems in the vicinity of a dynamic voltage restorer (DVR). A feedback controlled simulation model of an actual DVR in operation in the US is developed to perform case studies. Validity of this model is established by comparing the waveforms from the model with field measurements. Issues relating to maximization of a DVR in the vicinity of power factor correction capacitors are analyzed. Some considerations regarding the placement of capacitors in the vicinity of a DVR are drawn based on the simulation models.     

A design method for indirect iterative learning control based on two-dimensional generalized predictive control algorithm

Indirect iterative learning control (ILC) facilitates the application of learning-type control strategies to the repetitive/batch/periodic processes with local feedback control already. Based on the two-dimensional generalized predictive control (2D-GPC) algorithm, a new design method is proposed in this paper for an indirect ILC system which consists of a model predictive control (MPC) in the inner loop and a simple ILC in the outer loop. The major advantage of the proposed design method is realizing an integrated optimization for the parameters of existing feedback controller and design of a simple iterative learning controller, and then ensuring the optimal control performance of the whole system in sense of 2D-GPC. From the analysis of the control law, it is found that the proposed indirect ILC law can be directly obtained from a standard GPC law and the stability and convergence of the closed-loop control system can be analyzed by a simple criterion. It is an applicable and effective solution for the application of ILC scheme to the industry processes, which can be seen clearly from the numerical simulations as well as the comparisons with the other solutions.     

Rapid distributed model predictive control design using singular value decomposition for linear systems

The issue of model predictive control design of distribution systems using a popular singular value decomposition (SVD) technique is addressed. Namely, projection to a set of conjugate structure is dealt with in this paper. The structure of the resulting predictive model is decomposed into small sets of subsystems. The optimal inputs can be separately designed at each subsystem in parallel without any interaction problems. The optimal inputs can be directly obtained and the communication among the subsystems can be significantly reduced. In addition, the design of distribution model predictive control (DMPC) with constraints using the SVD framework is also presented. The unconstraint inputs are checked in parallel in the conjugate space. Without solving the QP problem of each subsystem, the suboptimal solution can be quickly obtained by selecting the bigger singular values and discarding the small singular values in the singular value space. The convergence condition of the proposed algorithm is also proved. Two case studies are used to illustrate the distribution control systems using the suggested approach. Comparisons between the centralized model predictive control method and the proposed DMPC method are carried out to show the advantages of the newly proposed method.     

Improved data-driven optimal TILC using time-varying input signals

A new improved data-driven optimal TILC (DDOTILC) is proposed for a class of nonlinear discrete-time systems by using time-varying control input signals to enhance control performance. An equivalent dynamical linear presentation is developed in the iteration domain for the repeatable nonlinear system, where the time-varying partial derivatives of the system with respect to the time-varying control inputs reflect the dynamical characters of the plant. Both the time-varying input signals and time-varying partial derivatives over the entire finite time interval are updated in batches, respectively. The proposed approach is a data-driven control scheme and only the boundedness of the partial derivatives is needed for control system design and analysis. Both rigorous mathematical analysis and the simulation results are provide to verify the applicability and effectiveness of the proposed approach further.     

Quantitative assessment of the effectiveness of using display techniques with a haptic device for manipulating 3D objects in virtual environments

Quantitative assessment is made of using two display techniques, providing two different levels of depth perception, in conjunction with a haptic device for manipulating 3D objects in virtual environments. The two display techniques are 2D display, and interactive 3D stereoscopic virtual holography display on a zSpace tablet. Experiments were conducted, by several users of different ages and computer training. The experiments involved selected pointing and manipulation tasks. The speed of performing the tasks using the two display techniques were recorded. Statistical analysis of the data is presented. As expected, the use of interactive 3D stereoscopic display resulted in faster performance of the tasks. The improvement in performance was particularly noticeable for the cases wherein the subjects needed to manipulate the haptic arm to reach objects/targets at different depths, and also when the objects/targets were occluded partially by the obstacles.     

基于小空间的火焰检测方法研究与实现

根据色度学和数字图像处理原理,讨论了如何计算数字图像区域周长和致密度.从理论分析及实验结果中得出了该方法具有精度高、适应性强、易于计算等特点,可以抵抗常见的干扰对系统的影响并较好的实现识别系统的鲁棒性与敏锐性的统一.     

A hierarchical system of on-line advisory for monitoring and controlling the depth of anaesthesia using self-organizing fuzzy logic

A hierarchical system has been developed to on-line advise on the concentration of inhaled volatile anaesthetics for controlling depth of anaesthesia. It merges on-line measurements (such as systolic arterial pressure and heart rate) and clinical information (such as sweating, lacrimation and movement) using a hierarchical architecture and self-organizing fuzzy logic for reasoning. It has been developed to predict depth of anaesthesia from either a “hand-crafted” anaesthetists’ or machine-learning rule-base using self-organizing learning system and control the drug levels using self-organizing fuzzy logic algorithm. In this paper, machine-learning rule-base has been validated via tests with 10 patients off-line and 17 patients on-line. The drug controller rule-base has also been validated via pre-tuning on 10 off-line patients and testing on 17 on-line patients. After extensive validation of this system, this on-line approach has shown promise and very successful for reducing the recovery time in comparison with either 10 patients off-line or other research.     

Multilayer design of hybrid phosphor film for application in LEDs

Crosslinked polydimethylsiloxane (PDMS) composite coatings containing luminescent micrometer-sized yellow Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) particles were prepared by spraying for potential applications in solid-state lighting. Blue light was down converted by phosphor particles to produce white light, yet poor color properties of YAG:Ce³⁺ stemmed from a deficiency of red. When nitride-based red phosphor was simply blended into the system, the electrostatic interaction of negatively charged YAG:Ce³⁺ and positively charged red phosphor particles caused remarkable clustering and heterogeneity in particle dispersion. Consequently, the light is dominantly blue and shifted to cold white. In other case, phosphor particles were sprayed onto the diffused polycarbonate substrate in stacked layers. Coatings with >80% inorganic content by mass with a thickness of 60 μm were subjected to thermal crosslinking, which the presence of the phosphor particles obstructed, presumably due to the hindrance of large phosphor particles in the diffusion of PDMS precursors. The coating of YAG:Ce³⁺ first followed by red phosphor in stacked layers produced better light output and color properties than the coating obtained by spraying the mixture at once. Monte Carlo simulation validated the hypothesis.     

Using head-mounted displays to examine adaptation and calibration under varying perturbations

Simulator sickness has been a pervasive problem as head-mounted displays (HMDs) grow in popularity. Recent work showed that people can adapt to constant latency in an HMD, but latency that varies has not been examined. In this study, participants performed a shooting task while wearing an HMD during three sessions separated by 48 h under conditions of constant or varying latency. Performance was assessed for both accuracy (targets hit) and speed (time-to-hit targets). It was hypothesized that participants would adapt to constant, but not varying latency as indicated by decreasing simulator sickness over time. Further, it was hypothesized that participants would improve performance over time for both conditions due to practice, but the constant latency group would improve at a faster rate. Results showed reduced sickness with session regardless of latency condition. A similar trend was shown where performance improved with each session, with no effect of the latency condition. Change in sickness and performance were not correlated, suggesting that the changes were independently driven. These findings showed that people reduced sickness and improved performance with repeated exposure, even when experiencing different perturbations. This finding has implications for both HMDs and general understanding of the relationship between latency and adaptation.     

Fuzzy goal-driven intelligent control for satellite environmental qualification

This paper reports on the application of Fuzzy Reference Gain-Scheduling Control (FRGS) to control a thermal-vacuum unit that emulates space environmental conditions for satellite and space device qualification. FRGS is a variation of fuzzy control that changes the controller gain surface in accordance to distinct operational conditions established by the reference (goal). This system allows to incorporate the experience of human operators by emulating human decision-making and reasoning, with the advantage of adaptation when parameters are adjusted on-line. The controller gain surface is adapted by modifying the shapes of the membership functions according to piecewise constant reference values. While the goal-driven adjustment is accomplished in a feedforward manner, feedback control technique is used to guarantee dynamical response. The experimental response obtained in the application to the real system has shown the effectiveness and flexibility of this control approach for such a nonlinear system.