UAV Velocity Measurement for Ground Moving Target

To satisfy the demand of measuring the velocity of ground moving target through unmanned aerial vehicle(UAV)electro-optical platform,two velocity measurement methods are proposed.Firstly,a velocity measurement method based on target localization is derived,using the position difference between two points with the advantages of easy deployment and realization.Then a mathematical model for measuring target velocity is built and described by 15 variables,i.e.UAV velocity,UAV attitude angular rate,camera direction angular rate and so on.Moreover,the causes of velocity measurement error are analyzed and a formula is derived for calculating the measurement error.Finally,the simulation results show that angular rate error has a strong influence on the velocity measurement accuracy,especially the UAV pitch angular rate error,roll angular rate error and the camera angular altitude rate error,thus indicating the direction for improving velocity measurement precision.

Passive target tracking with intermittent measurement based on random finite set

In the tracking problem for the maritime radiation source by a passive sensor,there are three main difficulties,i.e.,the poor observability of the radiation source,the detection uncertainty(false and missed detections)and the uncertainty of the target appearing/disappearing in the field of view.These difficulties can make the establishment or maintenance of the radiation source target track invalid.By incorporating the elevation information of the passive sensor into the automatic bearings-only tracking(BOT)and consolidating these uncertainties under the framework of random finite set(RFS),a novel approach for tracking maritime radiation source target with intermittent measurement was proposed.Under the RFS framework,the target state was represented as a set that can take on either an empty set or a singleton; meanwhile,the measurement uncertainty was modeled as a Bernoulli random finite set.Moreover,the elevation information of the sensor platform was introduced to ensure observability of passive measurements and obtain the unique target localization.Simulation experiments verify the validity of the proposed approach for tracking maritime radiation source and demonstrate the superiority of the proposed approach in comparison with the traditional integrated probabilistic data association(IPDA)method.The tracking performance under different conditions,particularly involving different existence probabilities and different appearance durations of the target,indicates that the method to solve our problem is robust and effective.

Strain Measurement for Hollow Projectiles During Its Penetration of Concrete Targets

Gives a new technique to measure the dynamic deformation behavior and strain development of a hollow steel projectile during its penetration of concrete targets. Direct strain measurement was performed by applying strain gages attached to the inner walls of the hollow projectile, linked with on-board testing and storage recorder. This on-board test-record system is easy to operate, cost-effective and can provide reasonable, accurate and detailed information. Obverse ballistic experiments were carried out on ogival-nose hollow projectiles normally impacting concrete targets at velocities from 150 m/s to 300 m/s. The deformation process of projectiles was measured, recorded and played back. Profiles of voltage-time relationship were successively obtained and transfered to strain-time relationship with the aid of calibration tables. It was found that projectiles go through a series of compression and tension deformations intermittently. Relationships between strain development and projectile deformation process were discussed.

Scaled radar cross section measurement method for lossy targets via dynamically matching reflection coefficients in THz band

In the terahertz band,the dispersive characteristic of dielectric material is one of the major problems in the scaled radar cross section(RCS)measurement,which is inconsistent with the electrodynamics similitude deducted according to the Maxwell’s equations.Based on the high-frequency estimation method of physical optics(PO),a scaled RCS measurement method for lossy objects is proposed through dynamically matching the reflection coefficients according to the distribution of the object facets.Simulations of the model of SLICY are conducted,and the inversed RCS of the lossy prototype is obtained using the proposed method.Comparing the inversed RCS with the calculated results,the validity of the proposed method is demonstrated.The proposed method provides an effective solution to the scaled RCS measurement for lossy objects in the THz band.

Recognition of Multifunctional Coded Target in Single-camera Mobile 3D-vision Coordination Measurement

Single-camera mobile-vision coordinate measurement is one of the primary methods of 3D-coordinate vision measurement, and coded target plays an important role in this system. A multifunctional coded target and its recognition algorithm is developed, which can realize automatic match of feature points, calculation of camera initial exterior orientation and space scale factor constraint in measurement system. The uniqueness and scalability of coding are guaranteed by the rational arrangement of code bits. The recognition of coded targets is realized by cross-ratio invariance restriction, space coordinates transform of feature points based on spacial pose estimation algorithm, recognition of code bits and computation of coding values. The experiment results demonstrate the uniqueness of the coding form and the reliability of recognition.

Activation measurement of neutron distribution in intermediate energy heavy ion target area

ＡｃｔｉｖａｔｉｏｎｍｅａｓｕｒｅｍｅｎｔｏｆｎｅｕｔｒｏｎｄｉｓｔｒｉｂｕｔｉｏｎｉｎｉｎｔｅｒｍｅｄｉａｔｅｅｎｅｒｇｙｈｅａｖｙｉｏｎｔａｒｇｅｔａｒｅａＬｉＧｕｉＳｈｅｎｇ，ＷａｎｇＪｉｎｇ，ＺｈａｏＹａｎＳｅｎ，ＬｉＷｅｎＪｉａｎ，...

Tracking method based on separation and combination of the measurements for radar and IR fusion system

A new distributed fusion method of radar/infrared （IR） tracking system based on separation and combination of the measurements is proposed by analyzing the influence of rate measurement. The rate information separated from the radar measurements together with measurements of IR form a pseudo vector of IR, and the corresponding filter is designed. The results indicate that the method not only makes a great improvement to the local tracker＇s performance, but also improves the global tracking precision efficiently.

Non-contact angle measurement based on parallel multiplex laser feedback interferometry

We present a novel precise angle measurement scheme based on parallel multiplex laser feedback interferometry （PLFI）, which outputs two parallel laser beams and thus their displacement difference reflects the angle variation of the target. Due to its ultrahigh sensitivity to the feedback light, PLFI realizes the direct non-contact measurement of non- cooperative targets. Experimental results show that PLFI has an accuracy of 8＂ within a range of 1400＂. The yaw of a guide is also measured and the experimental results agree with those of the dual-frequency laser interferometer Agilent 5529A.

Best linear unbiased estimation algorithm with Doppler measurements in spherical coordinates

In an active radar-tracking system,the target-motion model is usually modeled in the Cartesian coordinates,while the radar measurement usually is obtained in polar/spherical coordinates.Therefore the target-tracking problem in the Cartesian coordinates becomes a nonlinear state estimation problem.A number of measurement-conversion techniques,which are based on position measurements,are widely used such that the Kalman filter can be used in the Cartesian coordinates.However,they have fundamental limitations to result in filtering performance degradation.In fact,in addition to position measurements,the Doppler measurement or range rate,containing information of target velocity,has the potential capability to improve the tracking performance.A filter is proposed that can use converted Doppler measurements（i.e.the product of the range measurements and Doppler measurements） in the Cartesian coordinates.The novel filter is theoretically optimal in the rule of the best linear unbiased estimation among all linear unbiased filters in the Cartesian coordinates,and is free of the fundamental limitations of the measurement-conversion approach.Based on simulation experiments,an approximate,recursive implementation of the novel filter is compared with those obtained by four state-of-the-art conversion techniques recently.Simulation results demonstrate the effectiveness of the proposed filter.

A pixel-level local contrast measure for infrared small target detection

Infrared(IR) small target detection is one of the key technologies of infrared search and track(IRST)systems. Existing methods have some limitations in detection performance, especially when the target size is irregular or the background is complex. In this paper, we propose a pixel-level local contrast measure(PLLCM), which can subdivide small targets and backgrounds at pixel level simultaneously.With pixel-level segmentation, the difference between the target and the background becomes more obvious, which helps to improve the detection performance. First, we design a multiscale sliding window to quickly extract candidate target pixels. Then, a local window based on random walker(RW) is designed for pixel-level target segmentation. After that, PLLCM incorporating probability weights and scale constraints is proposed to accurately measure local contrast and suppress various types of background interference. Finally, an adaptive threshold operation is applied to separate the target from the PLLCM enhanced map. Experimental results show that the proposed method has a higher detection rate and a lower false alarm rate than the baseline algorithms, while achieving a high speed.

State estimation in range coordinate using range-only measurements

In some tracking applications,due to the sensor characteristic,only range measurements are available.If this is the case,due to the lack of full position measurements,the observability of Cartesian states(e.g.,position and velocity)are limited to particular cases.For general cases,the range measurements can be utilized by developing a state estimation algorithm in range-Doppler(R-D)plane to obtain accurate range and Doppler estimates.In this paper,a state estimation method based on the proper dynamic model in the R-D plane is proposed.The unscented Kalman filter is employed to handle the strong nonlinearity in the dynamic model.Two filtering initialization methods are derived to extract the initial state estimate and the initial covariance in the R-D plane from the first several range measurements.One is derived based on the well-known two-point differencing method.The other incorporates the correct dynamic model information and uses the unscented transformation method to obtain the initial state estimates and covariance,resulting in a model-based method,which capitalizes the model information to yield better performance.Monte Carlo simulation results are provided to illustrate the effectiveness and superior performance of the proposed state estimation and filter initialization methods.

A deformation measurement method based on surface texture information of rocks and its application

Users of the digital image correlation method are faced with the problem of poor operability,low repeatability,and lack of standardized specifications for spraying speckles.To solve the problem,the research proposed a rock deformation measurement method that obviates the need to spray speckles.A local binary model was established by using the local binary pattern(LBP)operator based on deep texture features on rock surfaces.The resulting LBP digital speckle pattern can substitute artificial speckle patterns and demonstrates high quality and strong applicability.Based on the LBP digital speckle pattern,the target tracking algorithm was employed to achieve non-contact measurement of the dynamic displacements of rocks.The feasibility and effectiveness of the algorithm in practical application were verified by conducting shear tests on granite and siltstone.Test results show that the deformation characteristics in the displacement nephograms are in line with the measured data pertaining to rock fracturing and conform to the basic characteristics of the shear failure of rocks.The deformation measurement method based on surface texture information can realize non-contact displacement measurement of rocks under conditions without speckles:this obviates the influence of the quality of sprayed speckles on the accuracy of the measurement of deformation.

COMPLETE PARAMETER MEASUREMENT FOR MIMO BISTATIC RADAR WITHOUT SYNCHRONIZATION

In order to measure the range, angle, and Doppler frequency of the target without any synchronization in the bistatic radar, a novel complete parameter estimation method based on separability of a pair of Linear Frequency Modulation (LFM) signal is presented. The Doppler fre-quency is measured by the time difference between two peak positions corresponding to the positive and the negative LFM return signal respectively. Direction Of Departures (DODs) and Direction Of Arrivals (DOAs) of the target are estimated by constructing a special eigenmatrix in which the es-timated angles can be extracted from the eigenvalue or the eigenvector. The target position can be located in the presence of the estimated DODs, DOAs and the signal delay difference between the echo and the directive wave signal in Multiple Input Multiple Output (MIMO) bistatic radar without any synchronization. The correctness and effectiveness of the proposed method are verified by the computer simulation.

Constrained auxiliary particle filtering for bearings-only maneuvering target tracking

To track the nonlinear,non-Gaussian bearings-only maneuvering target accurately online,the constrained auxiliary particle filtering(CAPF)algorithm is presented.To restrict the samples into the feasible area,the soft measurement constraints are implemented into the update routine via the1 regularization.Meanwhile,to enhance the sampling diversity and efficiency,the target kinetic features and the latest observations are involved into the evolution.To take advantage of the past and the current measurement information simultaneously,the sub-optimal importance distribution is constructed as a Gaussian mixture consisting of the original and modified priors with the fuzzy weighted factors.As a result,the corresponding weights are more evenly distributed,and the posterior distribution of interest is approximated well with a heavier tailor.Simulation results demonstrate the validity and superiority of the CAPF algorithm in terms of efficiency and robustness.

On-orbit target tracking and inspection by satellite formation

A new type of estimator is developed for the satellite formation to track and inspect on-orbit targets. The follower satellite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and controllability are analyzed to qualitatively evaluate the convergence performance. Finally, an on-orbit target inspection scenario is numerically simulated to verify the performance of the estimator based on pseudo measurement.

Experimental investigation of laser-produced-plasma EUV source based on liquid target

A laser-produced plasma(LPP) source was built using liquid as target and a Nd:YAG laser as the irradiation laser, and the LPP source's radiation with ethanol and acetone target respectively was measured by an AXUV100 silicon photodiode combined with a McPHERSON model 247 grazing incidence monochromator of the resolution Δλ≤0.075 nm and the wavelength scanning interval 0.5 nm. Both ethanol and acetone target LPP source had EUV emission at 11～20 nm wavelength. The comparison between the spectra of the two kinds of target materials shows that all the two kinds of target source's spectra are the result of oxygen ions' transitions under current source's parameters, but the spectrum intensity from different target sources is different. The spectra intensity from the ethanol target is higher than that from the acetone target. In addition, the target liquid is forced into the vacuum chamber by the background pressure supported by the connected external high pressure gas, and the influence of the background pressure on the source's intensity is investigated.

Uncertain IMM Estimator for Multi-Sensor Target Tracking

Interacting Multiple Model (IMM) estimator can provide better performance of target tracking than mono model Kalman filter. In multi-sensor system ordinarily, availability of measurement from different sensors is stochastic, and it is difficult to construct uniform global observation vector and observation matrix appropri-ately in existing method. An IMM estimator for uncertain measurement is presented. By the method invalid measurement is regarded as outlier, and approximation is reconstructed by feedback of system state estima-tion of fusion center. Then nominally generalized certain measurement can be obtained by substituting re-constructed one for invalid one. The generalized certain measurement can be centralized to construct global measurement and provided to IMM estimator, and existing multi-sensor IMM estimation method is general-ized to uncertain environment. Theoretical analysis and simulation results show the effectiveness of the method.

Fundamental Properties and Optimal Gains of a Steady-State Velocity Measured <i>α</i>-<i>β</i>Tracking Filter

This paper clarifies the steady-state properties and performance of an α-β filter for moving target tracking using both position and velocity measurements. We call this filter velocity measured α-β (VM-α-β) filter. We first derive the stability condition and steady-state predicted errors as fundamental properties of the VM-α-β filter. The optimal gains for representative motion models are then derived from the Kalman filter equations. Theoretical and numerical analyses verify that VM-α-β filters with these optimal gains realize more accurate tracking than conventional α-β filters when the filter gains are relatively large. Our study reveals the conditions under which the predicted errors of the VM-α-β filters are less than those of conventional α-β filters. Moreover, numerical simulations clarify that the variance of the tracking error of the VM-α-β filters is approximately 3/4 of that of the conventional α-β filters in realistic situations, even when the accuracy of the position/velocity measurements is the same.

一种应用于大尺寸测量系统的坐标系自动标定方法

针对现有方法在标定过程中过于繁琐的问题,提出了一种应用于大尺寸测量系统的坐标系全自动标定方法。该方法通过固定两个在测量单元局部坐标系已知坐标的测量节点作为标记靶,测量单元之间相互测量彼此的标记靶获得标记靶上的测量点在不同坐标系下的坐标值,利用这些坐标值建立三维几何约束,从而自动标定不同坐标系之间的坐标转换关系。借助于精密激光定位系统平台进行实验验证,结果表明,所提方法可以实现测量单元局部坐标系之间的自动标定,降低了坐标系标定过程中的人工成本。在距离测量单元布站区域约2 m,大小为5 000 mm×5 000 mm×500 mm的测量空间中长度测量的精度在0.46 mm/m以内,测试点三维坐标测量的标准偏差在0.026 mm以内,可以满足绝大部分工业测量的需求。该方法极大的提高了系统的标定效率,有望为具有自动标定功能的大尺寸测量设备的产品化提供新的理论基础。