共查询到20条相似文献,搜索用时 15 毫秒
1.
离轴式拖车移动机器人属于非完整系统,当车头线速度随时间变化且过零变号时,难以用一个控制器实现系统对期望路径的跟踪.本文研究离轴式拖车移动机器人系统的任意路径跟踪问题.首先由系统和虚拟小车的运动学方程得到误差状态模型,线性化后用坐标变换将其化为标准型,然后基于Lyapunov方法构造出一种跟踪控制律.只要车头的运动线速度有界且不趋于零,其导数有界,则所设计的控制律就可以保证系统跟踪任意的期望路径,且跟踪误差最终一致有界,最终界的大小与期望路径的曲率变化率成比例.当期望路径的曲率变化率为零或趋于零时,所设计的控制律可以保证拖车移动机器人指数收敛到期望路径.仿真结果证实了控制律的有效性. 相似文献
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Edge location to subpixel values in digital imagery 总被引:27,自引:0,他引:27
Tabatabai AJ Mitchell OR 《IEEE transactions on pattern analysis and machine intelligence》1984,(2):188-201
A new method for locating edges in digital data to subpixel values and which is invariant to additive and multiplicative changes in the data is presented. For one-dimensional edge patterns an ideal edge is fit to the data by matching moments. It is shown that the edge location is related to the so-called ``Christoffel numbers.' Also presented is the study of the effect of additive noise on edge location. The method is extended to include two-dimensional edge patterns where a line equation is derived to locate an edge. This in turn is compared with the standard Hueckel edge operator. An application of the new edge operator as an edge detector is also provided and is compared with Sobel and Hueckel edge detectors in presence and absence of noise. 相似文献
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PeerCast是一个基于P2P网络的流媒体传输系统,各节点被组织成树状来进行数据的分发.但没有一个有效的机制来维护树的平衡和保证所选取的父节点是最佳的节点.在此基础上,对该系统进行优化,在媒体数据包上加一个字节用来标识当前节点与根节点的距离,并对节点间响应消息进行优化.实验结果表明,这些优化措施能够有效的维护树的平衡和降底数据传输时延. 相似文献
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Constrained clustering as an optimization method 总被引:3,自引:0,他引:3
Rose K. Gurewitz E. Fox G.C. 《IEEE transactions on pattern analysis and machine intelligence》1993,15(8):785-794
A deterministic annealing approach to clustering is derived on the basis of the principle of maximum entropy. This approach is independent of the initial state and produces natural hierarchical clustering solutions by going through a sequence of phase transitions. It is modified for a larger class of optimization problems by adding constraints to the free energy. The concept of constrained clustering is explained, and three examples are are given in which it is used to introduce deterministic annealing. The previous clustering method is improved by adding cluster mass variables and a total mass constraint. The traveling salesman problem is reformulated as constrained clustering, yielding the elastic net (EN) approach to the problem. More insight is gained by identifying a second Lagrange multiplier that is related to the tour length and can also be used to control the annealing process. The open path constraint formulation is shown to relate to dimensionality reduction by self-organization in unsupervised learning. A similar annealing procedure is applicable in this case as well 相似文献
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以P89V51RD2FN单片机为控制核心,采用电容式倾角传感器实时测量车辆底盘的倾斜角,并用光电传感器检测车辆最终运动姿态和车速。光电传感器和倾角传感器将实时测量信号馈送至单片机,并采用增量式PID控制算法确保车辆能够达到平衡。利用CANBUS 2.0将数据传输至车载电脑来达到智能化车姿控制。实验结果表明:系统响应时间快,精度高,性能稳定。 相似文献
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Kato K. Masuda T. 《IEEE transactions on pattern analysis and machine intelligence》1992,18(7):631-645
Many recent complex object database systems support the concepts of object identity and object identifier. Following an object identifier to access the referenced object is called navigation operation and is an essential operation in dealing with complex objects. Navigation operation is a difficult operation to implement efficiently since every navigation operation inherently causes one disk access operation. A scheme to notably accelerate the navigation operation among a sea of complex objects, by increasing the effective number of objects in one disk page is proposed. The main concept of the presented technique is threefold. The first idea is to store a cached value within a complex object that is referencing another complex object. The second is that when the referenced object is to be updated the update propagation is delayed until the time when the cached value is referenced. The third is to utilize a hashed table on main memory to efficiently validate the consistency between the cached values and the original values 相似文献
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Specifications written in the formal specification language Z often make use of a form of decomposition that is novel to programmers. A published Z specification is rewritten using the form of decomposition familiar to programmers. Whenever decomposition is used, there must be some strategy for deciding what is to go in one component and what is to go in another. At the highest level, the strategy underlying the rewritten specification is the well-known strategy of separating user interface issues from deeper system functionality issues. The effectiveness of the strategy is put to a simple test by showing how a modification to the interface can be supported by a modification to only part of the specification. The conclusions drawn are that care over decomposition is important in specifications, just as it is in programs, and that lessons learned from programming about effective decomposition strategies can be applicable at the specification level, too. In particular, the lesson relearned is that it is important to separate information about a system's functionality from information about how this functionality is presented to users. 相似文献
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A strategy is presented for determining when it is advantageous to take some action to restore a system to full capacity. A determination is made of the types of data that need to be collected and circumstances under which the strategy is likely to be useful. Production traffic data is presented for a very large industrial telecommunications project, and the strategy is applied. An investigation is made of when the application of the strategy leads to increased system availability and decreased packet loss experienced by users. 相似文献
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含有等式约束优化问题的遗传算法 总被引:1,自引:0,他引:1
在遗传算法中最难处理的是有等式约束的优化问题,而等式约束在一般问题中常常遇到.许多算法采用引入惩罚函数降低适应度方法使其满足等式约束条件,但太难收敛或解根本不满足约束条件,因此它是遗传算法的一个瓶颈.根据遗传算法的性质及等式约束的特点,提出了另一种算法来解决这个瓶颈,并从理论上证明了算法的可行性.通过数值实验表明该算法是有效的. 相似文献
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一种新的删除AVL树的结点的算法 总被引:4,自引:1,他引:3
唐自立 《计算机应用与软件》2005,22(4):107-109
所有传统的删除AVL树的结点的算法的主要思想都是先删除结点再自下而上处理某些子树,涉及自下而上的后退。提出一种新的删除AVL树的结点的算法,其主要思想是先自上而下处理某些子树再删除结点,不涉及自下而上的后退。举例说明新算法的执行过程。证明新算法是正确的。与目前通常采用的Foster的算法相比,新算法不涉及辅助栈的使用。设n是AVL树的结点的个数。新算法的时间复杂性是O(log2n),与Foster的算法相同。实验结果表明新算法的平均执行时间比Foster的算法的短。新算法的空间复杂性是O(1),比Foster的算法的低。 相似文献
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光纤Bragg光栅损伤检测系统 总被引:1,自引:1,他引:0
损伤会导致结构局部刚度的下降,结果使损伤部位邻域的应变场分布发生显著变化。光纤Bragg光栅(FBG)传感器具有很高的灵敏度并能组成传感网络,适合于检测应变场的变化。通过应变场的变化也可以对失效螺钉进行定位。分布在结构表面的FBG传感器检测的应变数据组成向量,其单位向量定义为“模式”,该模式与载荷大小无关,与加载点位置有关,因此,能用于描述应变场。如果损伤前后模式的相关系数小于1,则加载点附件的螺钉可以判定为损伤。该方法在机翼盒段螺钉失效检测实验得到应用。 相似文献
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Hybridization of genetic algorithm with immune system for optimization problems in structural engineering 总被引:1,自引:1,他引:0
Optimization is the task of getting the best solution among the feasible solutions. There are many methods available to obtain
an optimized solution. Genetic algorithm (GA), which is a heuristic type of optimization method, is discussed in this paper.
The focus of the paper is the use of GA for large dimensionality design problems, where computational efficiency is a major
concern. The motivation of this paper is to hybridize GA with an immune system mechanism by avoiding the implementation of
penalty constants, which are highly sensitive to the choice of algorithm parameters. The principal advantage of the immune
system is in its seamless integration with GA-based search for optimal design. It is being hybridized with the immune system
mechanism. The hybrid GA and immune system is applied for the design of the optimal mix of high-performance concrete (HPC),
which is still based on trial mix and for which no rigorous mathematical approach is available. As such, to infer the values
of strength and slump, a wavelet back propagation neural network or wavelet neural network is used for any HPC mix. It is
necessary to minimize the cost of HPC/unit weight of HPC subjected to strength and slump constraints. The interwoven algorithm
is also applied to obtain optimal sectional areas for minimum weight of space trusses subjected to static loading. Formian
programming language is used for the generation of the space trusses, and Feast package is used for the static analysis of
the trusses. In addition to the induction of immune system in the GA for constraint handling, it is being applied in this
particular application for improving the search of GA in obtaining the best optimal solution. For obtaining the optimal sections
of space trusses subjected to earthquake loading, SAP 90 package is used, and reliable results are obtained. 相似文献
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详细给出了一种用微型电容式压力传感器镶入义齿基托的义齿受力检测系统。根据电容式压力传感器的工作原理,采用微机电系统(MEMS)工艺,研制出微型电容式压力传感器。通过传感器的埋入封装工艺,在与义齿基托相同材料的作底基的树脂上挖一个边长为2 mm平整的方形小坑,将传感器分布式埋植入底基,并用自制施加压力的装置对义齿对口腔下方组织的作用力进行测试。测量结果表明:本系统能够准确地测量出当牙齿咬合时,义齿基托所承受的力和力的分布。该传感器性能良好,具有比较稳定的输入与输出关系,适用于口腔恶劣环境下测量义齿对口腔下方的组织作用力。 相似文献
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主题爬行中的隧道穿越技术 总被引:2,自引:0,他引:2
由于网络环境的复杂性和网页内容的多主题性,要想得到更多的特定主题相关网页,就要穿越那些主题不相关网页来获取更多的主题相关网页,即隧道穿越.将隧道穿越分为灰色隧道穿越和黑色隧道穿越.对于灰色隧道,在爬行过程中,将一个多主题Web页面分割成数量不多的内容块分别处理来避免由于网页整体主题不相关给该块所带来的影响.对于黑色隧道的穿越,将隧道中主题不相关网页根据其父亲页面的主题相关性赋予一个深度值,然后根据其深度值的大小进行取舍,来达到扩展主题爬行区域的目的.实验结果显示,这两种方法都达到了预期效果,所以方法是有效、稳健和实用的. 相似文献
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Jaap Hage 《Information & Communications Technology Law》2000,9(3):219-240
This paper develops the theory that a set of rules is consistent if it is not possible that (1) the conditions of the rules in the set are all satisfied (2) there is no exception to either one of the rules, and (3) the consequences of the rules are incompatible. To this purpose the notion of consistency is generalised to make it cover rules and is relativised to a background of constraints. It is argued that a similar theory is also useful to characterise the consistency of deontic sentences of the ought-to-do type. The theory about rule consistency is formalised by means of Rule Logic, in which rules are treated as constraints on the possible worlds in which they exist. Rule Logic itself is introduced by giving a model-theory for it. It is characterised by means of constraints on worlds that are possible according to Rule Logic. The formal theory is refined by disallowing ungrounded exceptions to rules. To that purpose an additional constraint is imposed on worlds that are possible according to Rule Logic. 相似文献
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An algorithm CalcCycleTime to compute the cycle time of min-max systems is proposed. The computation is done by first calling CalcSpectralRadius to find the spectral radius, and then recursively calling itself to compute the cycle time of the reduced system. This algorithm is found to be efficient in practice. It is also used as a theoretical tool to analyze the structure of the eigenspace of min-max systems. It is found that a partial order, which is induced from the min-max function, is the key to characterize the structure of the eigenspace of min-max functions. 相似文献