Research On Autonomous Positioning Algorithm Of Mobile Robot Based On WLAN/RFID Information Fusion

In the system of autonomous mobile service robot, the accurateacquirement of current position of the robot is the prerequisite of completing thetask of navigation and tracking. WLAN and RFID are new positioning techniqueswhich have characteristics of high positioning accuracy, low power and low cost,so they are suitable for positioning of mobile robot. At present, single sensor isused to obtain information, but partial information of environmentalcharacteristics is responded due to the positioning inaccuracy of the system.Therefore, it is put forward that by using WLAN and RFID to establish thepositioning system and the information was combined using some method torealize the accurate positioning of the robot. This study is based on project of863Program “Research on Autonomous Positioning Key Technology of MobileRobot Based on WLAN/RFID Information Fusion”. Some key problems ofestablishing the WLAN and RFID system were studied in this dissertation. Thoseresearch works above lay the foundation for the development of multi-information fusion. The main contents of this dissertation are given as follows:In the WLAN wireless positioning system, aimed at the characteristics ofthe positioning system of mobile robot, the wireless positioning technology andwireless network positioning algorithm were analyzed, and the positioningmethod was determined based on RSSI, and the path loss model was analyzed.According to the experimental environment, the signal propagation model wasdetermined and simulation experiments were done, the experimental results wereanalyzed. Using wireless router and wireless NIC the wireless positioning systemof WLAN mobile robot was established and WLAN location method wasresearched based on RSSI. Through many experiments, trilateral locating methodwas determined for WLAN locating system.In the RFID (radio frequency identification) positioning system, aimed at the features of indoor positioning system of mobile robot such as complexenvironment and many obstacles, active radio frequency module was adapted andmobile robot location system indoors was built based on Visual C++6.0platform.In the system, four labels of the largest RSSI value were selected for positioningtabs, and based on maximum likelihood estimation method mobile error factorwas introduced, and the improved maximum likelihood estimation method wasproposed, and it was used in the system positioning system of mobile robot.In the Federated Filtering fusion structure, UKF was adopted to filter thelocal filtering results. Aimed at the features of UKF algorithm such as the resultbeing easy to diverge and slow calculation two improved UKF algorithms wereadopted. It was proposed that the most minimum skewness strategy should becombined with fading memory. For improving the calculation accuracy theminimum skewness strategy was introduced, which decreased the samplingnumbers. And take fading memory instead of covariance matrix in the recursiveoperation to decrease the filter divergence by calculation error. The proportionalrevision factor was combined with the minimum skewness to solve the problemof non local effect. Two algorithms were proposed in order to lay a foundationfor improving the positioning accuracy and positioning speed of the fusionsystem.On the basis of the WLAN and RFID system using single sensor could notmeet the positioning accuracy. So it was proposed that the Federated filteringtechniques was applied in the location system, and was combined with data fromWLAN and RFID to realize all accuracy improved. In the combined calculationprocess, because there was feedback reset of global filter in the local filters, theaccuracy of the local filter was also improved. It was proved from the result thatthe calculation improved was of feasibility.Consequently it is of important theoretical significance and academic valueto establish the information fusion and location system based on WLAN andRFID, such as reduce production cost, improve the positioning efficiency,improve the quality of design, and increase the ability of market competition.