Receding horizon control strategies have proven effective in many control and robotic applications. These methods simulate the state a certain time horizon into the future to choose the optimal trajectory. However, in many cases, such as in mobile robot navigation, the selection of an appropriate time horizon is important as too long of a time horizon can amplify the detrimental effects caused by environmental uncertainties in the prediction of the future state while too of a short horizon will lead to reduced performance. In this paper we strike a balance between these two conflicting objectives by first introducing a receding horizon method for navigation founded on schema-based behaviors. We then suggest a method of adapting the time horizon by minimizing a cost function which balances the performance of the underlying control problem (which prefers longer horizons) with the performance of our state prediction (which prefers shorter time horizons). We illustrate the operation with an example which shows the usefulness of our navigation scheme with an adaptive time horizon.
Terms for Religious Studies (Taylor 1998); it cannot be found even among the 3,200 articles in The HarperCollins Dictionary of Religion (Smith 1995). The absence of "fraud" from the disciplinary léxica is more than a little curious, especially since "fraud" is very much a part of religion's vocabulary, and, from a cynical view of religion's history, "fraud" might very well be regarded as the modus operandi religiosus. How is it that, within the history of religion, "fraud" can be an instrument of legitimation under one set of circumstances and an altogether illegitimate act under another? The article engages this question through an analysis and redescription of the phenomenon of the "holy book" in Mediterra nean antiquity. One is never simpleminded enough about the condemnation of forger ies. Pious frauds are frauds, for which one must show no piety-and no pity. (Momigliano 1987: 7) This just in ... Tomorrow on the Fox News Channel you hear the following story: Unnamed sources reveal that President George W. Bush will an nounce today that Chief Justice William Reinquist has just made an astonishing discovery. In an unused storage closet of the Supreme Court building in Washington, D.C., Justice Reinquist has found a previously unknown document that purports to be the lost second page of the Constitution of the United States. The signatures of Madison, Hamilton, and the other members of the Constitutional Convention affixed to the document have reportedly been authenti cated by Joseph Ellis, a well-known scholar of early American history and, coincidentally, a relative of Karl Rove, White House chief ad viser. The same sources are reporting that the newly restored Consti tution stipulates that the United States is a Christian nation, man dates prayer in public schools, prohibits a woman's right to an
Due to the increase in road transportation several projects concerning automated highway systems were initiated to optimize highway capacity. In the future, the developed techniques should be applicable in unstructured environment (e.g. desert) and adaptable for heterogeneous vehicles. But before, several challenges, i.e. independency of lane markings, have to be overcome. Our solution is to consider the back view of the preceding vehicle as a reference point for the lateral and longitudinal control of the following vehicle. This solution is independent from the environmental structure as well as additional equipment like infrared emitters. Thus, both the detection and tracking process of the back view are needed to provide automated highway systems with the distance and the deviation degree of the preceding vehicle. In this paper the first step, the detection and location of the back view on video streams, is discussed. For a definite detection in a heterogeneous platoon several features of the back view are detected. A method is proposed to run rejection cascades generated by the AdaBoost classifier theory on the video stream. Compared to other methods related to object detection, the proposed method reduces the running time for the detection of the back view to 0.03-0.08 s/frame. Furthermore, the method enables a more accurate detection of the back view.
Due to their low price and good quality, Stereo Vision Systems (SVS) are recently considered as a key factor to gather actual information about the object of interest. Today, automated highway systems (AHS) for urban and highway environment were developed without the use of a stereo vision system. In future, the application of AHS should be extended to unstructured environments (e.g. desert) and be adapted to heterogeneous vehicles. In this context, the stereo vision system could enable the platoon to be independent from environmental structure (e.g. lane markings) through its ability to detect, track, locate and recognize heterogeneous vehicles. So far, the need for high accuracy prevents SVS to be applied in automated heterogeneous platoon. In this paper a mechanism towards this is presented, where some behavioral properties have to be satisfied in terms of unstructured environment and heterogeneous platoons. Within a heterogeneous platoon, the back view of a preceding vehicle (BVPV) is considered as a reference point for the lateral and longitudinal control. The key idea of the proposed mechanism is to confirm that the distance of the BVPV can be extracted without depending on the movement of the preceding vehicle. Furthermore, the proposed mechanism has to ensure that features extracted from the back view are suitable to implement successfully the calibration process at around 10m distance. With the proposed SVS mechanism some of behavioral properties have to be satisfied in terms of unstructured environment and AHS. These properties are reliability, performance and robustness. Compared to other methods which use a SVS, the proposed mechanism distinguishes itself through adapting to dynamic environment and extracting the necessary features for the calibration process.
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