Integrating WSN and Laser SLAM for Mobile Robot Indoor Localization

Localization plays a vital role in the mobile robot navigation system and is a fundamental capability for the following path planning task.In an indoor environment where the global positioning system signal fails or becomes weak,the wireless sensor network(WSN)or simultaneous localization and mapping(SLAM)scheme gradually becomes a research hot spot.WSN method uses received signal strength indicator(RSSI)values to determine the position of the target signal node,however,the orientation of the target node is not clear.Besides,the distance error is large when the indoor signal receives interference.The laser SLAM-based method usually uses a 2D laser Lidar to build an occupancy grid map,then locates the robot according to the known grid map.Unfortunately,this scheme only works effectively in those areas with salient geometrical features.The traditional particle filter always fails for areas with similar structures,such as a long corridor.To solve their shortcomings,this paper proposes a novel coarse-to-fine paradigm that uses WSN to assist mobile robot localization in a geometrically similar environment.Firstly,the fingerprints database is built in the offline stage to get reference distance information.The distance data is determined by the statistical mean value of multiple RSSI values.Secondly,a hybrid map with grid cells and RSSI values is constructed when the mobile robot moves from a starting point to the ending place.Thirdly,the RSSI values are thought of as a basic reference to get a coarse localization.Finally,an improved particle filteringmethod is presented to achieve fine localization.Experimental results demonstrate that our approach is effective and robust for global localization.The localization success rate reaches 97.0%and the average moving distance is only 0.74 meters,while the traditional method always fails.In addition,the method also works well when the mobile robot is kidnapped to another position in the environment.

Durability of Concrete with Different Improvement Measures and Its Ser-vice Life Prediction in Island and Reef Environment

To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were used as the influence factors,while the relative dynamic elastic modulus was used as the evaluation index.In addition,the law and time variability of the deterioration of concrete,the size effect,environmental similarity and the service life model were studied.The results showed that improving the strength grade of concrete could improve the durability of concrete,and corrosion inhibitor could slightly improve the durability of concrete.Time-varying law of the deterioration of concrete conformed to the univariate quadratic polynomial.Combined with the concrete damage equivalent theory,a size effect model based on the relative dynamic elastic modulus was proposed and verified,and the size effect coefficient was also given.An environmental similarity model between simulated and practical island and reef environment was proposed.Combined with the reliability theory and the first order second moment method,a new service life model of concrete structure was proposed.The authors were convinced that the research will be advantageous to researchers.