scholarly journals Refining Inaccurate Transmitter and Receiver Positions Using Calibration Targets for Target Localization in Multi-Static Passive Radar

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3365 ◽  
Author(s):  
Yongsheng Zhao ◽  
Dexiu Hu ◽  
Yongjun Zhao ◽  
Zhixin Liu ◽  
Chuang Zhao
Keyword(s):  
Lower Bound ◽  
Closed Form Solution ◽  
Form Solution ◽  
Measurement Noise ◽  
Target Localization ◽  
Passive Radar ◽  
Localization Accuracy ◽  
Position Errors ◽  
Simulation Results ◽  
Calibration Step

Transmitter and receiver position errors have been known to significantly deteriorate target localization accuracy in a multi-static passive radar (MPR) system. This paper explores the use of calibration targets, whose positions are known to the MPR system, to counter the loss in target localization accuracy arising from transmitter/receiver position errors. This paper firstly evaluates the Cramér–Rao lower bound (CRLB) for bistatic range (BR)-based target localization with calibration targets, which analytically indicates the potential of calibration targets in enhancing localization accuracy. After that, this paper proposes a novel closed-form solution, which includes two steps: calibration step and localization step. Firstly, the calibration step is devoted to refine the inaccurate transmitter and receiver locations using the BR measurements from the calibration targets, and then in the calibration step, the target localization can be accurately achieved by using the refined transmitter/receiver positions and the BR measurements from the unknown target. Theoretical analysis and simulation results indicate that the proposed method can attain the CRLB at moderate measurement noise level, and exhibits the superiority of localization accuracy over existing algorithms.

scholarly journals An Efficient Estimator for Target Localization in a Multistation Redundancy System without Matrix Inversion

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Xiwen Zhang ◽  
Jiyan Huang ◽  
Yiyuan Wang ◽  
Yineng Zhou
Keyword(s):  
Low Cost ◽  
Closed Form Solution ◽  
Form Solution ◽  
Matrix Inversion ◽  
Target Localization ◽  
Weighting Coefficient ◽  
Algebraic Solution ◽  
Location Based Service ◽  
Positioning Accuracy ◽  
Minimum System

This paper focuses on target localization problem in a multistation redundancy system which finds broad applications in sonar, radar, and location-based service. Previous solutions can only be applied to the minimum system, such as the TOA method with three sensors and the AOA method with two sensors or need matrix inversion. To solve this problem, we propose a simple closed-form solution for a multistation redundancy localization system by using the estimation variance as the weighting coefficient to compute an average of each group’s localization result. The proposed method, with simple algebraic solution, requires no matrix inversion and can be used for low-cost hardware devices. We derive the method in TOA solution and AOA solution, respectively. The proposed method can also be extended to other locating technologies. Numerical examples are provided to illustrate the performance of the proposed method in root-mean-square error. The positioning accuracy of the proposed method is close to Cramér-Rao low bound both in TOA solution and AOA solution.

scholarly journals Metrological Characterization of a Vision-Based System for Relative Pose Measurements with Fiducial Marker Mapping for Spacecrafts

Robotics ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 43 ◽  
Author(s):  
Marco Pertile ◽  
Sebastiano Chiodini ◽  
Riccardo Giubilato ◽  
Mattia Mazzucato ◽  
Andrea Valmorbida ◽  
...  
Keyword(s):  
Measurement Errors ◽  
Closed Form Solution ◽  
Measurement Procedure ◽  
Form Solution ◽  
Bundle Adjustment ◽  
Physical Parameters ◽  
Position Measurement ◽  
Position Errors ◽  
Relative Pose

An improved approach for the measurement of the relative pose between a target and a chaser spacecraft is presented. The selected method is based on a single camera, which can be mounted on the chaser, and a plurality of fiducial markers, which can be mounted on the external surface of the target. The measurement procedure comprises of a closed-form solution of the Perspective from n Points (PnP) problem, a RANdom SAmple Consensus (RANSAC) procedure, a non-linear local optimization and a global Bundle Adjustment refinement of the marker map and relative poses. A metrological characterization of the measurement system is performed using an experimental set-up that can impose rotations combined with a linear translation and can measure them. The rotation and position measurement errors are calculated with reference instrumentations and their uncertainties are evaluated by the Monte Carlo method. The experimental laboratory tests highlight the significant improvements provided by the Bundle Adjustment refinement. Moreover, a set of possible influencing physical parameters are defined and their correlations with the rotation and position errors and uncertainties are analyzed. Using both numerical quantitative correlation coefficients and qualitative graphical representations, the most significant parameters for the final measurement errors and uncertainties are determined. The obtained results give clear indications and advice for the design of future measurement systems and for the selection of the marker positioning on a satellite surface.

scholarly journals A NEW CLOSED FORM SOLUTION FOR DYNAMIC STABILITY ANALYSIS OF ROLLING AIRFRAMES HAVING ONE PAIR ON-OFF ACTUATOR

Aviation ◽  
2021 ◽  
Vol 25 (2) ◽  
pp. 92-103
Author(s):  
Jalal Karimi
Keyword(s):  
Stability Analysis ◽  
Closed Form ◽  
Dynamic Stability ◽  
Linear Theory ◽  
Closed Form Solution ◽  
Form Solution ◽  
Control Surface ◽  
Closed Form Solutions ◽  
Forcing Term ◽  
Simulation Results

In this paper, the dynamic stability analysis of a rolling airframe actuated by one pair ON-OFF actuator using linear theory is presented via developing a new closed form solution. The effect of discontinuous forcing term on rolling airframe stability is studied. In contrast to tricyclic motion with constant forcing term (constant non-homogeneous term) in which only the amplitude of nutation and precession is affected, it is found that ON-OFF control affects both amplitude and phase of nutation and precession motions. In the case of discontinuous control surface, there are two sources for resonance instability. Finally, through simulation results of closed form solutions, a comparison between airframe’ response to ideal and real ON-OFF command is achieved. The effect of ON-OFF control on angular motion is also evaluated.

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