Edge detecting is a f undamental issue in image analysis and image processing. In this paper, based on wavelet transform, an edge detector of SAR image is studied to serve the image aided navigation. Though wavelet ...Edge detecting is a f undamental issue in image analysis and image processing. In this paper, based on wavelet transform, an edge detector of SAR image is studied to serve the image aided navigation. Though wavelet transform is efficient as an edge detector, a l ot of false edges will be extracted from a SAR image, especially in areas of hig h reflectivity, with wavelet transform and a fixed threshold because SAR images are always contaminated by speckle. Therefore, this paper develops an algorithm by using a variable threshold with constant false alarm rates to help suppressin g the speckle in SAR images. Finally, two simulating tests are given and the res ults show that the effect of the multiplicative speckle is controlled and there are few false edges in the gotten edge images. Moreover, owing to the threshold from the wavelet transform coefficients, the algorithm can assure the real time of SAR image aided navigation.展开更多
To solve the problem of information fusion in the strapdown inertial navigation system(SINS)/celestial navigation system(CNS)/global positioning system(GPS) integrated navigation system described by the nonlinear/non-...To solve the problem of information fusion in the strapdown inertial navigation system(SINS)/celestial navigation system(CNS)/global positioning system(GPS) integrated navigation system described by the nonlinear/non-Gaussian error models,a new algorithm called the federated unscented particle filtering(FUPF) algorithm was introduced.In this algorithm,the unscented particle filter(UPF) served as the local filter,the federated filter was used to fuse outputs of all local filters,and the global filter result was obtained.Because the algorithm was not confined to the assumption of Gaussian noise,it was of great significance to integrated navigation systems described by the non-Gaussian noise.The proposed algorithm was tested in a vehicle's maneuvering trajectory,which included six flight phases:climbing,level flight,left turning,level flight,right turning and level flight.Simulation results are presented to demonstrate the improved performance of the FUPF over conventional federated unscented Kalman filter(FUKF).For instance,the mean of position-error decreases from(0.640×10-6 rad,0.667×10-6 rad,4.25 m) of FUKF to(0.403×10-6 rad,0.251×10-6 rad,1.36 m) of FUPF.In comparison of the FUKF,the FUPF performs more accurate in the SINS/CNS/GPS system described by the nonlinear/non-Gaussian error models.展开更多
This paper describes a reactive navigation proposed for a differentially driven robot. The aim of the reactive navigation is to prescribe behavior to the robot based on actual sensor values that is collision-free. Ana...This paper describes a reactive navigation proposed for a differentially driven robot. The aim of the reactive navigation is to prescribe behavior to the robot based on actual sensor values that is collision-free. Analysis of reactive navigation methods shows that there is no reliable reactive collision-free method. However, method VFH＋ is suboptimal reactive navigation method for static environment. Original method was proposed for ultrasonic rangefinders. Nowadays, much more sophisticated sensors are available. That is why our modification is proposed for a laser rangefinder attached to indoor mobile robot. Results are presented as simulation in Matlab and also as experiments with real robot. Based on these experiments, it can be claimed that VFH＋ is very effective reactive navigation method for various sensors and environments and it can be modified for different requirements on robot behavior.展开更多
英语首字母缩略词sonar(sound naviga-tion and ranging,声波导航和测距)的音译“声纳”曾经通行一时,几年前却改名为“声呐”,其主要原因就是为了避免同表示另一个概念的acoustic susceptance的译名“声纳”相重。这样改动是完全必要的...英语首字母缩略词sonar(sound naviga-tion and ranging,声波导航和测距)的音译“声纳”曾经通行一时,几年前却改名为“声呐”,其主要原因就是为了避免同表示另一个概念的acoustic susceptance的译名“声纳”相重。这样改动是完全必要的,因为异词同名常常导致概念上的混乱,是同术语标准化和规范化的要求不相容的。展开更多
文摘Edge detecting is a f undamental issue in image analysis and image processing. In this paper, based on wavelet transform, an edge detector of SAR image is studied to serve the image aided navigation. Though wavelet transform is efficient as an edge detector, a l ot of false edges will be extracted from a SAR image, especially in areas of hig h reflectivity, with wavelet transform and a fixed threshold because SAR images are always contaminated by speckle. Therefore, this paper develops an algorithm by using a variable threshold with constant false alarm rates to help suppressin g the speckle in SAR images. Finally, two simulating tests are given and the res ults show that the effect of the multiplicative speckle is controlled and there are few false edges in the gotten edge images. Moreover, owing to the threshold from the wavelet transform coefficients, the algorithm can assure the real time of SAR image aided navigation.
基金Project(60535010) supported by the National Nature Science Foundation of China
文摘To solve the problem of information fusion in the strapdown inertial navigation system(SINS)/celestial navigation system(CNS)/global positioning system(GPS) integrated navigation system described by the nonlinear/non-Gaussian error models,a new algorithm called the federated unscented particle filtering(FUPF) algorithm was introduced.In this algorithm,the unscented particle filter(UPF) served as the local filter,the federated filter was used to fuse outputs of all local filters,and the global filter result was obtained.Because the algorithm was not confined to the assumption of Gaussian noise,it was of great significance to integrated navigation systems described by the non-Gaussian noise.The proposed algorithm was tested in a vehicle's maneuvering trajectory,which included six flight phases:climbing,level flight,left turning,level flight,right turning and level flight.Simulation results are presented to demonstrate the improved performance of the FUPF over conventional federated unscented Kalman filter(FUKF).For instance,the mean of position-error decreases from(0.640×10-6 rad,0.667×10-6 rad,4.25 m) of FUKF to(0.403×10-6 rad,0.251×10-6 rad,1.36 m) of FUPF.In comparison of the FUKF,the FUPF performs more accurate in the SINS/CNS/GPS system described by the nonlinear/non-Gaussian error models.
文摘This paper describes a reactive navigation proposed for a differentially driven robot. The aim of the reactive navigation is to prescribe behavior to the robot based on actual sensor values that is collision-free. Analysis of reactive navigation methods shows that there is no reliable reactive collision-free method. However, method VFH＋ is suboptimal reactive navigation method for static environment. Original method was proposed for ultrasonic rangefinders. Nowadays, much more sophisticated sensors are available. That is why our modification is proposed for a laser rangefinder attached to indoor mobile robot. Results are presented as simulation in Matlab and also as experiments with real robot. Based on these experiments, it can be claimed that VFH＋ is very effective reactive navigation method for various sensors and environments and it can be modified for different requirements on robot behavior.
文摘英语首字母缩略词sonar(sound naviga-tion and ranging,声波导航和测距)的音译“声纳”曾经通行一时,几年前却改名为“声呐”,其主要原因就是为了避免同表示另一个概念的acoustic susceptance的译名“声纳”相重。这样改动是完全必要的,因为异词同名常常导致概念上的混乱,是同术语标准化和规范化的要求不相容的。
