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101.
    
This study is concerned with the integrated system of a robot and a machine tool. The major task of robot is loading the workpiece to the machine tool for contour cutting. An iterative learning control (ILC) algorithm is proposed to improve the accuracy of the finished product. The proposed ILC is to modify the input command of the next machining cycle for both robot and machine tool to iteratively enhance the output accuracy of the robot and machine tool. The modified command is computed based on the current tracking/contour error. For the ILC of the robot, tracking error is considered as the control objective to reduce the tracking error of motion path, in particular, the error at the endpoint. Meanwhile, for the ILC of the machine tool, contour error is considered as the control objective to improve the contouring accuracy, which determines the quality of machining. In view of the complicated contour error model, the equivalent contour error instead of the actual contour error is taken as the control objective in this study. One challenge for the integrated system is that there exists an initial state error for the machine tool dynamics, violating the basic assumption of ILC. It will be shown in this study that the effects of initial state error can be significantly reduced by the ILC of the robot. The proposed ILC algorithm is verified experimentally on an integrated system of commercial robot and machine tool. The experimental results show that the proposed ILC can achieve more than 90% of reduction on both the RMS tracking error of the robot and the RMS contour error of the machine tool within six learning iterations. The results clearly validate the effectiveness of the proposed ILC for the integrated system.  相似文献   
102.
In a multi-server authentication environment, a user only needs to register once at a central registration place before accessing the different services on the different registered servers. Both, from a user point of view as for the management and maintenance of the infrastructure, these types of environments become more and more popular. Smartcard- or smartphone-based approaches lead to more secure systems because they offer two- or three-factor authentication, based on the strict combination of the user’s password, the user’s biometrics and the possession of the device. In this paper, we propose an efficient anonymous authentication protocol in multiple server communication networks, called the EAAM protocol, which is able to establish user anonymity, mutual authentication, and resistance against known security attacks. The novelty of the proposed scheme is that it does not require a secure channel during the registration between the user and the registration center and is resistant to a curious but honest registration system. These features are established in a highly efficient way with the minimum amount of communication flows between user and server during the establishment of the secret shared key and by using light-weight cryptographic techniques such as Chebyshev chaotic map techniques and symmetric key cryptography. The performance and security of the protocol are analyzed and compared with the latest new proposals in this field.  相似文献   
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There are presented in this paper the investigation results of microstructure as well hardness investigation of the surface layer of cast aluminium alloys in as‐cast state and after laser surface treatment using a high power diode laser (HPDL) with Al2O3 ceramic powder. The purpose of this work was to determine the proper laser treatment conditions for surface treatment of the investigated alloys and to describe the structural changes occurred in the surface layer after laser treatment. For investigation of the obtained structure there was used light as well scanning and transmission electron microscopy. The morphology and size of the ceramic powder particles as well the structure of the remelted aluminium surface layer was possible to determine. After the laser surface treatment carried out on the aluminium cast alloys there are visible structural changes concerning the microstructure as well as distribution and morphology of the fed particles occurred in the sample surface. Concerning the laser treatment conditions for surface hardening also the laser power and ceramic powder feed rate was studied. The structure of the surface laser tray changes in a way, that there are zones detected like the remelting zone and the heat influence zone. This investigation with appliance of a high power diode laser for Al alloys makes it possible to obtain or develop an interesting technology very attractive for different industry branches.  相似文献   
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Abstract

This work suggests a maximizing set and minimizing set based fuzzy multiple criteria decision‐making (MCDM) model, where criteria are classified into cost and benefit criteria. The final fuzzy evaluation value of each alternative is developed based on the concept of subtracting the summation of weighted normalized benefit ratings from that of weighted normalized cost ratings. Using interval arithmetic of fuzzy numbers can develop the membership functions for the final fuzzy evaluation values. Chen's maximizing set and minimizing set is then applied to defuzzify all the final fuzzy numbers for ranking alternatives. Formulas for the membership functions and ranking procedure of the final fuzzy numbers are clearly presented. The suggested method provides an extension to the fuzzy MCDM techniques available. A numerical example demonstrates the computational process of the proposed method.  相似文献   
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Abstract

The computer prediction of turbogenerator behaviour following fault or disturbance conditions has become an important feature in the assessment of machine system design, pre‐commissioning test appraisals, system operational procedures, machine monitoring strategy and post‐event damage diagnoses. In this paper computer methods are described to assess the comparative severity of various electrical faults and disturbances, the effect of specific operational practices together with the prediction of peak torsional transient behaviour. This paper is supported by realistic examples simulating the transient behaviour of a number of generational units.  相似文献   
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Abstract

In this paper the design of a self‐constructing recurrent fuzzy neural network (SCRFNN)‐based digital channel equalizer is proposed. It is found that a digital channel equalizer based on SCRFNN can recover channel distortions effectively. We compare the performance of SCRFNN with adaptive‐based‐network fuzzy inference system (ANFIS) and the Bayesian equalizers in complex‐valued linear channels. Our simulations show that the performance of SCRFNN is close to the Bayesian optimal solution. Furthermore, the hardware requirement of the trained SCRFNN equalizer is relatively lower than the other two structures.  相似文献   
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