Fuzzy adaptive Kalman filter for indoor mobile target positioning with INS/WSN integrated method

Pure inertial navigation system(INS) has divergent localization errors after a long time. In order to compensate the disadvantage, wireless sensor network(WSN) associated with the INS was applied to estimate the mobile target positioning. Taking traditional Kalman filter(KF) as the framework, the system equation of KF was established by the INS and the observation equation of position errors was built by the WSN. Meanwhile, the observation equation of velocity errors was established by the velocity difference between the INS and WSN, then the covariance matrix of Kalman filter measurement noise was adjusted with fuzzy inference system(FIS), and the fuzzy adaptive Kalman filter(FAKF) based on the INS/WSN was proposed. The simulation results show that the FAKF method has better accuracy and robustness than KF and EKF methods and shows good adaptive capacity with time-varying system noise. Finally, experimental results further prove that FAKF has the fast convergence error, in comparison with KF and EKF methods.

Metrology for sub-Rayleigh-length target positioning in~10^(22)W/cm^(2)laser-plasma experiments

Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.

An automated, 0.5 Hz nano-foil target positioning system for intense laser plasma experiments

We report on a target system supporting automated positioning of nano-targets with a precision resolution of 4 μm in three dimensions. It relies on a confocal distance sensor and a microscope. The system has been commissioned to position nanometer targets with 1 Hz repetition rate. Integrating our prototype into the table-top ATLAS 300 TW-laser system at the Laboratory for Extreme Photonics in Garching, we demonstrate the operation of a 0.5 Hz laser-driven proton source with a shot-to-shot variation of the maximum energy about 27% for a level of confidence of 0.95. The reason of laser shooting experiments operated at 0.5 Hz rather than 1 Hz is because the synchronization between the nano-foil target positioning system and the laser trigger needs to improve.

A real-time detection and positioning method for small and weak targets using a 1D morphology-based approach in 2D images

A small and weak target detection method is proposed in this work that outperforms all other methods in terms of real-time capability.It is the first time that two-dimensional(2D)images are processed using only one-dimensional1D structuring elements in a morphology-based approach,enabling the real-time hardware implementation of the whole image processing method.A parallel image readout and processing structure is introduced to achieve an ultra-low latency time on the order of nanoseconds,and a hyper-frame resolution in the time domain can be achieved by combining the row-by-row structure and the electrical rolling shutter technique.Experimental results suggest that the expected target can be successfully detected under various interferences with an accuracy of 0.1 pixels(1σ)under the worst sky night test condition and that a centroiding precision of better than 0.03 pixels(1σ)can be reached for static tests.The real-time detection method with high robustness and accuracy is attractive for application to all types of real-time small target detection systems,such as medical imaging,infrared surveillance,and target measurement and tracking,where an ultra-high processing speed is required.

Ionized gas clouds near the Sagittarius Arm tangent

Radio recombination lines（RRLs） are the best tracers of ionized gas. Simultaneous observations of multi-transitions of RRLs can significantly improve survey sensitivity. We conducted pilot RRL observations near the Sagittarius Arm tangent by using the 65-m Shanghai Tian Ma Radio Telescope（TMRT） equipped with broadband feeds and a digital backend. Six hydrogen RRLs（H96α-H101α）at C band（6289 MHz-7319 MHz） were observed simultaneously toward a sky area of 2°× 1.2° by using on-the-fly mapping mode. These transitions were then stacked together for detection of ionized gas. Star forming complexes G48.6＋0.1 and G49.5-0.3 were detected in the integrated intensity map.We found agreements between our measured centroid velocities and previous results for the 21 known HII regions in the mapped area. For more than 80 cataloged HII region candidates without previous RRL measurements, we obtained new RRL spectra at 30 targeted positions. In addition, we detected 25 new discrete RRL sources with spectral S/N 〉 5σ, and they were not listed in the catalogs of previously known HII regions. The distances for 44 out of these 55 new RRL sources were estimated.

A Novel Imaging Algorithm for Airborne Bistatic Squint SAR with Unparallel Trajectories

A novel analytical imaging algorithm is proposed for the strip-map mode of airborne bistatic squint SAR with unparallel trajectories. The algorithm derives the two-dimensional （2D） spectrum formula of the point target echo by using the contribution ratios of Doppler frequency modulation ratios of the transmitter and receiver as the weighting coefficients. Through decoupling the target position against the tracks of the transmitter and receiver, the range parameter and the azimuth one in the spectrum formula are separated. In 2D frequency domain, 2D Chirp-Z transform （2D-CZT） is applied to correcting the migrations of the echo along the range and azimuth after the bistatic deformation term has been compensated, so the target image is precisely focused. The advantage of the algorithm is easy to be expanded to the virtual wide swath by blocking the radar data along the range and azimuth to limit the 2D residual migrations. Simulation results confirm the validity of the 2D-CZT algorithm.