Fengying Wang

An Improved Chaotic Motion Path Planner for Autonomous Mobile Robots based on a Logistic Map

This paper presents a chaotic motion path planner based on a Logistic Map (SCLCP) for an autonomous mobile robot to cover an unknown terrain randomly, namely entirely, unpredictably and evenly. The path planner has been improved by arcsine and arccosine transformation. A motion path planner based only on the Logistic Chaotic Map (LCP) can show chaotic behaviour, which possesses the chaotic characteristics of topological transitivity and unpredictability, but lacks better evenness. Therefore, the arcsine and arccosine transformations are used to enhance the randomness of LCP. The randomness of the followed path planner, LCP, the improved path planner SCLCP and the commonly used Random Path Planner (RP) are discussed and compared under different sets of initial conditions and different iteration rounds. Simulation results confirm that a better evenness index of SCLCP can be obtained with regard to previous works.

A Bounded Strategy of the Mobile Robot Coverage Path Planning Based on Lorenz Chaotic System

According to the requirements of the mobile robot complete coverage path planning for some special missions, this paper introduces a bounded strategy based on the integration of the Lorenz dynamic system and the robot kinematics equation. Chaotic variables of the Lorenz system are confined in a limited range, while when they are used to produce the robots coordinate position, the trajectory range is determined by the starting point, iterative times, and iterative step. The proposed bounded strategy can constrain all the robot positions in the workplace by a mirror mapping method that can reflect the overflow waypoints returning to it. Moreover, the statistical characteristics of the Lorenz chaotic variables and the robot trajectory are discussed in order to choose the best mapping variable. The simulation results show that the bounded strategy that uses the chosen variable can achieve a higher coverage rate contrary to other similar works.

Research of the obstacle avoidance based on RBFNN for the mobile robot under dynamic environment

A new obstacle avoidance algorithm for the mobile robot is introduced. When the dynamic obstacle is in a nonlinear random movement, a radial basis function neural network (RBFNN) is used to build the prediction model. The next location of the obstacle is predicted based on the three adjacent value of time sequence. Thus the dynamic obstacle avoidance issue is converted into the instantaneous static one and the realization of real-time planning is achieved. The prediction model performance of RBFNN has been compared with a back propagation neural network (BPNN) forecast model which is normally used. The results show that RBFNN model has the higher forecast accuracy and faster learning rate. Combined with the designed N/M data division, the model is very suitable for systems of nonlinear time series prediction.

Security scheme research of digital products online transactions

This paper analyses the problems that the transaction scheme of existing digital products existed. We propose a relatively perfect transaction scheme. In the scheme, combining digital watermarking and fingerprinting with digital signatures, a relatively less amount of information is embedded in a digital product , so as to reduce phenomena of descending quality, as well as issues of mutual interference, and improve efficiency Before the trade, a robust symmetric watermarking was embedded in a product sample and get a new product. Then the new product is signed. Thus online buyer may verify legitimate copyright and find timely pirated products. During the trade, after an asymmetric digital fingerprinting was embedded in the digital product, could trace pirate by the trade fingerprint, could prevent merchant from bring a false charge against the buyer, and could also have an anonymous property for the buyer.

Chaotic Path Planner of Autonomous Mobile Robots Based on the Standard Map for Surveillance Missions

This paper proposes a fusion iterations strategy based on the Standard map to generate a chaotic path planner of the mobile robot for surveillance missions. The distances of the chaotic trajectories between the adjacent iteration points which are produced by the Standard map are too large for the robot to track. So a fusion iterations strategy combined with the large region iterations and the small grids region iterations is designed to resolve the problem. The small region iterations perform the iterations of the Standard map in the divided small grids, respectively. It can reduce the adjacent distances by dividing the whole surveillance workspace into small grids. The large region iterations combine all the small grids region iterations into a whole, switch automatically among the small grids, and maintain the chaotic characteristics of the robot to guarantee the surveillance missions. Compared to simply using the Standard map in the whole workspace, the proposed strategy can decrease the adjacent distances according to the divided size of the small grids and is convenient for the robot to track.

A comprehensive security policy research on web information system

In order to solve security problems in web-based information systems in the large-scale distributed environment, we design a comprehensive security policy. We realize the single entry mechanism of multi-system access by using the single-sign-on, create identity authentication mechanism of high-reliability and security based on Chinas second-generation ID card. We also propose the cross-domain setup and its strategies for the access from scattered information systems. This paper will show the access control policy which combines dynamic and static methods, bring up a combination of coarse-grained and fine-grained access control strategy through refining digital objects, operations and rights. Besides we realize encrypted data communication for VPN by using SSL encryption technology to make data encapsulation. Considering the database security, we adopt access control technology, separation control technology, encryption technology, data flow control technology, reasoning control technology and backup technology. We then track and check all users who accessed or tried to access the system by using the system audit, use the triple-right separation mechanism for reliable management to avoid the abuse of powerful rights owned by the system administrator.

A chaotic coverage path planner for the mobile robot based on the Chebyshev map for special missions

We introduce a novel strategy of designing a chaotic coverage path planner for the mobile robot based on the Chebyshev map for achieving special missions. The designed chaotic path planner consists of a two-dimensional Chebyshev map which is constructed by two one-dimensional Chebyshev maps. The performance of the time sequences which are generated by the planner is improved by arcsine transformation to enhance the chaotic characteristics and uniform distribution. Then the coverage rate and randomness for achieving the special missions of the robot are enhanced. The chaotic Chebyshev system is mapped into the feasible region of the robot workplace by affine transformation. Then a universal algorithm of coverage path planning is designed for environments with obstacles. Simulation results show that the constructed chaotic path planner can avoid detection of the obstacles and the workplace boundaries, and runs safely in the feasible areas. The designed strategy is able to satisfy the requirements of randomness, coverage, and high efficiency for special missions.

An improved sampling algorithm for landmark windows over weighted streaming data

This paper discusses the random sampling algorithm for landmark windows over weighted streaming data, and presents a new algorithm by improving weighted random sampling (WRS) algorithm with a reservoir. When a new data item vi with weight wi arrives, a random number ui is generated, and a key ki is calculated by wi and ui for the data item. We maintain a candidate sample set by the keys of data items, and the keys of older data items is decreased periodically. The theoretic analysis and experiments show that the algorithm is effective and efficient for continuous data streams processing.

Adaptive behavior analysis of WMR based on chaotic phase-space reconstruction

The chaotic theory of phase-space reconstruction is applied to the adaptive behavior analysis and construction of the robot due to the complex nonholonomic and non-linear characteristics of WMR (Wheeled Mobile Robot). The WMR and the operating environment as a whole, a set of control rules for the adaptive behavior which can produce local optimal planning path are obtained by QL (Q_Learning). Then a set of time series of the adaptive behavior are sampled utilizing the density of obstacles as a variable in the running environment and the phase-space is reconstructed. At last the data in the phase-space are discussed and analyzed based on the chaotic time series theory. The simulation results show that the one dimension adaptive time series sampled according to the obstacles density demonstrate the chaotic characteristics. So the chaotic theory can be used in the adaptive behavior analysis and forecast and provides an adequate theoretical basis for the more precise control to WMR.

A stratified sampling algorithm for landmark windows over data streams

In many applications, data does not take the form of traditional stored relations, but rather arrives in continuous, rapid, time-varying data streams,and data streams are potentially unbounded in size. Focusing on the problem of sampling from landmark windows over data streams, a new concept, which is called stratified sampling ratio function, is presented. Then a multistage stratified sampling algorithm for landmark window model is introduced. In the algorithm, a dynamic candidate sample set is maintained. When an arrived tuple is determined to enter the sample set and to be deleted from the sample, the arrival time of data items is considered, and the probability for selecting to enter and remain in the sample set of more recent arrived tuples is greater than that of older ones. The theoretic analysis and experiments show that the algorithm is effective and efficient for continuous data streams processing.