Applied Mechanics and Materials Vols. 635-637

Abstract: By studying on the nonlinear hysteresis characteristics of piezoelectric actuators,this paper proposes a neural network modeling method based on polynomial fitting algorithm and a compound control method for compensation of the hysteresis.Simulation shows that the fitting error of neural network model is 1.42%. According to the developed hysteretic model,PID and feed-forward control methods are applied to the system.The result is that the tracking relative error of control system is 1.59%,so the tracking precision of system is improved significantly.This indicates that the neural network model reflects the hysteresis characteristics of piezoelectric actuators accurately,and this control method is an effective compensation control for hysteresis in piezoelectric actuators.

Abstract: Abstract：The application of Gauss pseudospectral method (GPM) to hypersonic aircraft reentry trajectory optimization problem with maximum cross range was introduced. The Gauss pseudospectral method was used to solve the reentry trajectory of the hypersonic vehicle with the maximum cross range. Firstly, the model of hypersonic aircraft reentry trajectory optimization control problem was established. Taking no account of course constraint, the maximum cross range was chosen as optimal performance index, and angle of attack and bank was chosen as control variable. Terminal state was constrained by position and velocity. Then GPM was applied to change trajectory optimization problem into nonlinear programming problem (NLP), and the state variables and control variables were selected as optimal parameters at all Gauss nodes. At last, optimal reentry trajectory was solved by solving the NLP with the help of SNOPT. The simulation results indicate that GPM does not need to estimate the initial cost variable, and it is not sensitive to the initial states and effective to solve trajectory optimization problem.

Abstract: This paper describes one demisting system in vehicle camera. On the basis of fuzzy control algorithm, temperature sensor and humidity sensor were used to sample the temperature and humidity inside the dome's cover, single-chip microcomputer was used to get the dew point temperature and window glass's actual temperature through calculation and adjust the heating power consumption automatically. With these processes, the target of intelligent demisting system finally was achieved. This design is practical in vehicle domes.

Abstract: This paper investigates the problems of stabilization and control for time-delay switched fuzzy systems using output feedback controller. Based on the linear matrix inequality (LMI) technique, multiple Lyapunov method is used to obtain a sufficient condition for the existence of the controller for the output feedback. Then an algorithm is constructed to transform the sufficient condition into a LMI form, thus obtaining a method for designing the controller. The designed controller guarantees the closed-loop system to be asympototically stable. A numerical example is given to show the effectiveness of our method.

Abstract: Nonlinear characteristic hinder the effective use of piezoelectric smart materials in sensors and actuators. In this paper, the intelligent fuzzy PID controller is designed in the Matlab-Simulink environment. The piezoelectric smart actuator model is built. An adaptive fuzzy PID control scheme was proposed. The proposed control scheme was implemented in Matlab. The results of simulation and experiment indicate that the control method has good control ability.

Abstract: Take the traction wire rope cleaning and detection line of pay-off unit as an example, investigate the general law of the change during paying off of traction wire rope cleaning and detection line and build the mathematical model in each step of the paying off tension control system. Build the simulation model using MATLAB on the foundation of the mathematical model and research on the model. Afterwards, it is proved that the demand of keeping the tension of pay-off unit constant can be meet through regulating magnetic braking torque of pay-off unit.

Abstract: As a high precision attitude measuring instrument in arc-second level, star sensor has become a necessary component for satellites, spacecraft and space station. However, star sensor misalignment angle can reach the arc-minute level and reduce the accuracy of the star sensor’s output severely. Since it’s difficult to measure the initial alignment error precisely on the ground, research applicable to star sensor misalignment angle calibration technique is necessary. To make the system get a high precision attitude control, a GPS-assisted Kalman filter modeling of the system was carried out. Finally, the misalignment angle from the board axes to the star sensor axes can be estimated by employing the derived relationship. The mathematical simulation results show the effectiveness of the calibration algorithm.

Abstract: K-means algorithm is a traditional cluster analysis method, has the characteristics of simple ideas and algorithms, and thus become one of the commonly used methods of cluster analysis. However, the K-means algorithm classification results are too dependent on the choice of the initial cluster centers for some initial value, the algorithm may converge in general suboptimal solutions. Analysis of the K-means algorithm and particle swarm optimization based on a clustering algorithm based on improved particle swarm algorithm. The algorithm local search ability of the K-means algorithm and the global search ability of particle swarm optimization, local search ability to improve the K-means algorithm to accelerate the convergence speed effectively prevent the occurrence of the phenomenon of precocious puberty. The experiments show that the clustering algorithm has better convergence effect.

Abstract: In the context of the wide application of cloud computing technology, Internet crimes with the support of such technology will increase. In this article, the author proposed a holistic set of digital forensics method applicable in could computing environment from the point of the four stages of digital evidence collection, preservation, analysis and presentation. In evidence collection session, original resource of electric data collection was discussed. In evidence preservation session, electronic data storage system on Hadoop was designed. In evidence analysis session, two types of crime data were analyzed. In evidence presentation session, what the result should be shown were explained.

Abstract: Keyword extraction is important for information retrieval. This paper gave a hybrid keyword extraction method based on TF and semantic strategies for Chinese document. A new word finding method was proposed to find the new word not exist in the dictionary. Moreover the semantic strategies were introduced to filter the dependent words and remove the synonyms. Experimental results show that the proposed method can improve the accuracy and performance of keyword extraction.