Targets In Clutter Background Research Articles

A Composite Guidance Law for Suppressing Measurement Noise of LOS Angular Rate

To effectively intercept a low-altitude target in clutter background, a nonsingular fast terminal sliding mode guidance law is designed. The designed guidance law can fully exploit the fast convergence characteristics of linear sliding mode control and the finite-time-convergent characteristics of terminal sliding mode control to ensure that the line-of-sight (LOS) angle converges to a desired angle in a limited time at a faster rate. Utilizing the smooth switching characteristics of the hyperbolic tangent function similar to the saturation function, a finite-time-convergent differentiator is designed. Meanwhile, a new finite-time-convergent disturbance observer designed on the tracking differentiator can effectively track the ideal LOS angular rate, suppress the measurement noise, and make a smooth estimation of the target maneuvering acceleration in clutter background. Combining the estimated value of the disturbance observer, the sign function with switch coefficient is introduced to design a composite nonsingular fast terminal sliding mode guidance law. The simulation results show that the composite guidance law can not only effectively suppress the measurement noise of the LOS angular rate and improve the accuracy of low-altitude target intercepting, but also greatly reduce the energy consumption in the interception process.

Optical Correlation Recognition Technology of Small Moving Target Based on Wavelet Multi-Scale Edge Fusion

Moving target recognition has a wide application in varieties of domains and has received more attention in recent years. Among all the recognition methods, optical correlation technology, using hybrid optoelectronic joint transform correlator (HOJTC), has the merits of parallel, large capacity and high-speed, so it is considered as one of the most effective methods for moving target detection. But in the course of detecting, some targets are too small to be recognized by HOJTC. These small targets in cluttered background and strong noise may affect the brightness of the correlation peaks and have a serious influence on target recognition results. In order to solve this problem, this paper applies a wavelet multi-scale edge fusion algorithm which firstly extracts the edge at different scales by wavelet modulus maximum method, and then fuses the detected edge to obtain more edge information of the target. In addition, for the moving distortion problems, taking temporal state of the target as the template can achieve the template update. To prove this method, many detection experiments of small moving targets have been performed with optical correlation method. As an example a small target “boat” taking up only pixels is presented. The recognition results show that the brightness of the correlation peaks is enhanced and the target recognition ratio is increased. The conclusion can be drawn that applying this algorithm in optical correlation method can realize the small moving target recognition successfully and expand the application to scope of optical correlation technology.

Passive Range Estimation Using Two and Three Optical Cameras

In passive tracking of a flying object with bearing only measurements, range information is needed. This is accomplished by applying more than one passive optical imager. Active sensing systems have disadvantages for low-flying targets in cluttered backgrounds meanwhile are simply detected. In the observable regions of the target range, using two cameras, target range can be calculated by triangulation. If the target locates in the vicinity of sensors baseline, low observable target range will be resulted. This problem can be solved using three cameras. In this paper novel equations to calculate the target range using 3-D triangulation by two cameras are extracted, observability condition for target range is stated, target range is estimated by extended Kalman filter, observable target range is resulted by using three bearing sensors placed at a distance not along a straight line, and finally sensor fusion for estimated target range is performed.

低对比度目标探测技术

In order to improve joint transform correlator(JTC) for recognition ability of low-contrast target in cluttered background,a new object plane filtering method is proposed based on the combination of wavelet transform,gray stretching and Canny operator.Finally,a new object plane processing filter is designed.The computer simulation and optical experiments show that this method can extract the target feature accurately,reduce the noise effectively and obtain bright correlation peaks.The recognition problem of low contrast target in cluttered background is solved successfully.

Min-local-LoG filter for detecting small targets in cluttered background

A novel spatial filtering method is presented to detect small targets in a cluttered background for infrared search and track (IRST). The filtering process of localised directional Laplacian-of-Gaussian (LoG) filtering, and the minimum selection can then remove false detections around cloud edges maintaining a small target detection capability. Experimental results validate the feasibility of the proposed method (called min-local-LoG).