Current Issue : October - December Volume : 2015 Issue Number : 4 Articles : 4 Articles
The accurate estimation of measurements covariance is a fundamental problem\nin sensors fusion algorithms and is crucial for the proper operation of filtering algorithms.\nThis paper provides an innovative solution for this problem and realizes the proposed\nsolution on a 2D indoor navigation system for unmanned ground vehicles (UGVs) that\nfuses measurements from a MEMS-grade gyroscope, speed measurements and a light\ndetection and ranging (LiDAR) sensor. A computationally efficient weighted line\nextraction method is introduced, where the LiDAR intensity measurements are used, such\nthat the random range errors and systematic errors due to surface reflectivity in LiDAR\nmeasurements are considered. The vehicle pose change is obtained from LiDAR line feature\nmatching, and the corresponding pose change covariance is also estimated by a weighted\nleast squares-based technique. The estimated LiDAR-based pose changes are applied as\nperiodic updates to the Inertial Navigation System (INS) in an innovative extended Kalman\nfilter (EKF) design. Besides, the influences of the environment geometry layout and line\nestimation error are discussed. Real experiments in indoor environment are performed to\nevaluate the proposed algorithm. The results showed the great consistency between the\nLiDAR-estimated pose change covariance and the true accuracy. Therefore, this leads to a\nsignificant improvement in the vehicle�s integrated navigation accuracy....
Automatic ship reporting systems (AIS ââ?¬â?? Automatic identification System, LRIT ââ?¬â?? Long\nRange Identification and Tracking, VMS ââ?¬â?? Vessel Monitoring System) today allow global\ntracking of ships. One way to display the results is in a map of current ship positions over\nan area of interest, the Maritime Situational Picture (MSP). The MSP is dynamic and must\nbe created by fusing the reporting systemsââ?¬â?¢ messages, constructing ship tracks and predicting\nship positions to correct for latency especially in the case of AIS received by satellite which\nforms the bulk of the data. This paper discusses the completeness of the resulting MSP and\nthe accuracy of its positions, quantifying the additional value of the individual data sources....
The study presents the influence of strong total\nelectron content (TEC) fluctuations occurring at high latitudes\non rapid static positioning. The authors propose an\nalgorithm mitigating the impact of dynamic temporal\nchanges in electron content using the rate of TEC corrections.\nIt consists of modifying the observations using the\nmeasured rate of TEC variations and hence allows reducing\nthe number of parameters to one ionospheric delay of a\nreference epoch per satellite and per session. An analysis\nwas carried out for a typical quiet day in solar minimum on\nSeptember 6, 2009 and a disturbed day during high solar\nactivity on March 17, 2013. For a standard geometry-based\nrelative model with weighted ionosphere and troposphere,\nthe results confirmed the dramatic drop of ambiguity resolution\nefficiency during a violent space weather event.\nThe results obtained for the new algorithm, however,\ndemonstrate its wide applicability and a 10-fold improvement\nin ambiguity success rate during the disturbed day....
Inertial technology has been used in a wide range of applications such as\nguidance, navigation, and motion tracking. However, there are few undergraduate courses\nthat focus on the inertial technology. Traditional inertial navigation systems (INS) and\nrelevant testing facilities are expensive and complicated in operation, which makes it\ninconvenient and risky to perform teaching experiments with such systems. To solve this\nissue, this paper proposes the idea of using smartphones, which are ubiquitous and\ncommonly contain off-the-shelf inertial sensors, as the experimental devices. A series of\ncurriculum experiments are designed, including the Allan variance test, the calibration test,\nthe initial leveling test and the drift feature test. These experiments are well-selected and\ncan be implemented simply with the smartphones and without any other specialized tools.\nThe curriculum syllabus was designed and tentatively carried out on 14 undergraduate\nstudents with a science and engineering background. Feedback from the students show that\nthe curriculum can help them gain a comprehensive understanding of the inertial\ntechnology such as calibration and modeling of the sensor errors, determination of the\ndevice attitude and accumulation of the sensor errors in the navigation algorithm. The use of\ninertial sensors in smartphones provides the students the first-hand experiences and intuitive feelings about the function of inertial sensors. Moreover, it can motivate students to utilize\nubiquitous low-cost sensors in their future research....
Loading....