ESTIMATION IN MULTIPLE AUTOREGRESSIVE-MOVING AVERAGE MODELS USING PERIODICITY

Abstract. An estimation procedure for multiple autoregressive-moving average models is suggested which takes advantage of the possibility of transferring these multiple models to univariate periodic autoregressive-moving average models. The procedure is simple enough to be practicable using less efficient computers and it should give acceptable estimates for longer time series. By using this method for shorter time series, the obtained estimates may serve as the initial estimates for more complicated estimation procedures.     

Computing depth maps from descent images

In the exploration of the planets of our solar system, images taken during a landers descent to the surface of a planet provide a critical link between orbital images and surface images. The descent images not only allow us to locate the landing site in a global coordinate frame, but they also provide progressively higher-resolution maps for mission planning. This paper addresses the generation of depth maps from the descent images. Our approach has two steps, motion refinement and depth recovery. During motion refinement, we use an initial motion estimate in order to avoid the intrinsic motion ambiguity. The objective of the motion-refinement step is to adjust the motion parameters such that the reprojection error is minimized. The depth-recovery step correlates adjacent frames to match pixels for triangulation. Due to the descending motion, the conventional rectification process is replaced by a set of anti-aliasing image warpings corresponding to a set of virtual parallel planes. We demonstrate experimental results on synthetic and real descent images.Received: 7 November 2002, Accepted: 13 September 2004, Published online: 25 February 2005 Correspondence to: Clark F. Olson     

Linear mass balance equilibration: a new approach for an old problem

Interval analyses are well known in the mathematics literature but have found few applications in control engineering. Based on the interval concept, we present here a methodology for data reconciliation and mass balance equilibration which is a very classical problem in mineral and chemical engineering. Indeed, this problem is solved with the view of inequality constraints which allows us to represent measurements by interval without particular knowledge and hypothesis about the density probability function of the measurement errors. As a main result, the paper gives a set of solutions for the reconciled data under an interval form and not only one solution as is the case with classical approaches.     

Greenhouse gas production: a comparison between aerobic and anaerobic wastewater treatment technology

Anaerobic wastewater treatment offers improved energy conservation with potential reduction in greenhouse gas emissions. Pitfalls exist in that the methane produced in anaerobic treatment can offset any reductions in carbon dioxide emissions, if it is released to the environment. This paper analyzes greenhouse gas emissions from both aerobic and anaerobic treatment systems, including sludge digestion and the losses of dissolved methane in digested biosolids and process effluents. There exists cross over points, ranging from 300 to 700 mg/L influent wastewater BODu, which are functions of the efficiency of the aerobic treatment system. Anaerobic treatment becomes favorable when treating influents higher in concentrations than the cross over values. A technology to recover dissolved methane would make anaerobic treatment favorable at nearly all influent strengths.     

A satellite selection criterion incorporating the effect of elevation angle in GPS positioning

When positioning by global positioning systems, geometric dilution of precision is generally used as a satellite selection criterion. While it takes account of only geometric effects, there are other factors causing positioning error, such as ionospheric delay, tropospheric delay, and multipath. In this paper, a new criterion for satellite selection, which considers the effect of these errors, is proposed and the effectiveness of the proposed criterion is shown.     

Q control charts for negative binomial distribution

As we known, Q charts are SPC charts for approximate normal distribution. This paper proposes new kinds of Q charts for negative binomial random variable. First, define two transformations of approximate standard normal distribution for a negative binomial parameter p which it is known or unknown. Then, Q charts are constructed by transformed data, these Q charts are useful for monitoring process in real time from the beginning of sampling, especially, for p unknown in advance. In order to compare the goodness of the Q charts with conventional Shewhart charts with 3-sigma limits, an example is given. The results have shown that these Q charts are more efficient than classical Shewhart charts. Finally, some review are given.     

基于全局模型的产品特征造型系统

基于特征的设计在当今ＣＡＤ／ＣＡＭ技术中扮演了十分重要的角色，本文以我们自行开发的面向机械产品设计的参数货物上造型系统ＺＤ－ＭＣＡＤⅡ＾〔１〕为背景，介绍了ＺＤ－ＭＣＡＤⅡ中的全局产品数据模型，给出了特征及其依赖的描述方法，特征依赖以半序网的形式表示，设计特征与制造特征通过特征映射实现统一。文章对于产品模型的建立及特征形成规则与特征重构都作了详细的分析。     

红外导引头防空导弹剩余时间估算方法

探讨了红外导引头测得的热源信号峰值电压与导弹至目标之间距离、导弹剩余时间与热源信号峰值电压之间的关系。提出了两种估算导弹剩余时间的方法,并应用某型导弹的两条典型弹道进行了计算,给出了计算结果,做了初步精度分析。     

机器人卫星自主控制系统的研究

在国内首次研制成功了机器人卫星（或称空间自由飞行机器人）的自主控制系统及其地上实验平台。该自主控制系统在平台上实现的空间微重力环境条件下，通过运动规划系统能完成机器人卫星自主地避开障碍物，准确地捕捉目标的路径规划演示实验。这一成果对用机器人卫星捕捉失效卫星并对其进行维修、补给能量从而使其复活再生的研究具有实际应用意义。     

A linear air bearing stage with active magnetic preloads for ultraprecise straight motion

In this paper, we propose a linear motion stage designed with magnetically preloaded air bearings. The magnetic actuators for preloading air bearings were combined with permanent magnets and coils to adjust the air bearing clearance by actively controlling the magnetic force. The system was designed to achieve a simplified configuration of air bearing stage while providing ultraprecise straight motion by actively compensating for the motion errors. The porous aerostatic bearings and magnetic preload actuators were designed and analyzed numerically for a single-axis prototype linear stage driven by a coreless linear motor. A magnetic circuit model was derived for the magnetic actuators. The static stiffness and load capacity of the air bearing stage in the vertical (magnetically preloaded) direction were experimentally measured and compared with the results from the numerical analysis. Motion control laws for three degrees of freedom (i.e., vertical, pitch, and roll motions) were obtained with a high linearity and independence for each axis. The active compensation of three motion errors, the vertical, pitch and roll motion errors were performed through curve-fitting the three errors measured with combination of capacitive gap sensors and a laser interferometer. The errors were reduced from 1.09 to 0.11 μm for the vertical straightness error, from 9.42 to 0.18 arcsec for the pitch motion, and from 2.42 to 0.18 arcsec for the roll motion as level of measured repeatability.