Constraint estimation of spacecraft positions

The constrained Kalman filter is implemented for spacecraft formation-flying absolute positions estimation. The orbital motion of a spacecraft is characterized by two range extrema (perigee and apogee). At the extremum, the rate of change of a spacecraft\u27s range vanishes. This motion constraint can be used to improve the position estimation accuracy. The application of the constrained Kalman filter at only two points in the orbit causes filter instability. Two variables, α and β, are introduced into the constrained Kalman filter to maintain the stability and improve the estimation accuracy. Anextended Kalman filter is implemented as a benchmark for comparison with the constrained Kalman filter. Simulation results show that, with proper selection of α and β values, the constrained Kalman filter provides better estimation accuracy as compared with the extended Kalman filter. In this paper, two scenarios are studied. In the first scenario, a spacecraft\u27s absolute position is estimated by assuming the availability of radar measurements. In the second scenario, spacecraft formation absolute positions are estimated. It is assumed that the spacecraft formation is equipped with a Wireless Local Positioning System, which provides the relative-position measurements between spacecraft in the formation. Only relative measurements are assumed in this paper. Copyright © 2011 by Shu Ting Goh

Implementation of a Differential Geometric Filter for Spacecraft Formation Orbit Estimation

The differential geometric filter is implemented to estimate the absolute and relative positions of the spacecraft in a formation. The extended Kalman Filter is also implemented as a benchmark for the differential geometric estimation. Only relative positions between the spacecraft are measured. Relative positions are measured using a wireless local positioning system (WLPS) installed in all spacecraft. Two different scenarios are studied: (1) the observations include WLPS measurements only and (2) the observations include WLPS measurements in addition to measurements for the absolute position of one spacecraft made by a radar that takes measurements from the earth’s surface. Results show that the differential geometric estimation has better stability performance and a faster convergence rate compared to the extended Kalman filter

Spacecraft Formation Orbit Estimation Using WLPS-Based Localization

This paper studies the implementation of a novel wireless local positioning system (WLPS) for spacecraft formation flying to maintain high-performance spacecraft relative and absolute position estimation. A WLPS equipped with antenna arrays allows each spacecraft to measure the relative range and coordinate angle(s) of other spacecraft located in its coverage area. The dynamic base station and the transponder of WLPS enable spacecraft to localize each other in the formation. Because the signal travels roundtrip in WLPS, and due to the high spacecraft velocities, the signal transmission time delay reduces the localization performance. This work studies spacecraft formation positions estimation performance assuming that only WLPS is available onboard. The feasibility of estimating the spacecraft absolute position using only one-dimensional antenna array is also investigated. The effect of including GPS measurements in addition to WLPS is studied and compared to a GPS standalone system

Real-time signal processing of massive sensor arrays via a parallel fast converging SVD algorithm: Latency, throughput, and resource analysis

© 2016 IEEE. This paper introduces a parallel fast converging Jacobi-like singular value decomposition (SVD) algorithm applicable to real-time signal processing of massive sensor arrays. The proposed algorithm highly increases the SVD convergence rate for larger matrices when compared with traditional Jacobi-based methods. A highly modular system design is proposed, which retains the parallel nature of the Jacobi methods key to real-time implementation intended for field programmable gated arrays (FPGAS). The proof of design was provided via an implementation on Virtex-6 FPGA, and the improvement in performance was verified via simulations. The proposed design was compared with the traditional design in terms of FPGA resource consumption, maximum achievable frequency, and latency throughput tradeoff

1 CHAPTER WIRELESS POSITIONING SYSTEMS: OPERATION, APPLICATION, AND COMPARISON

R ECENT YEARS have seen rapidly increasing demand for services and systems that depend upon accurate positioning of people and objects. This has led to the development and evolution of numerous positioning systems. This chapter provides an overview of the main positioning techniques: time of arrival ( TOA), direction of arrival ( DOA), and received signal strength indicator ( RSSI). It then introduces positioning systems that are either in use or being developed for a variety of applications. Operations of these positioning systems are summarized using flowcharts and figures. In addition, the chapter compares positioning systems on the basis of system characteristics and performance parameters. Many of these positioning techniques and systems are introduced in greater detail throughout different parts of this handbook. The chapter concludes by reviewing a number of emerging positioning systems and outlining some future applications. 1.

A novel synchronization method for active positioning via DSSS: Achieving low resource usage and latency

This paper presents a new method for timing synchronization in mobile transceivers utilizing direct sequence spread spectrum signaling (DSSS) for target localization. Traditional methods of timing synchronization for DSSS produce variable latency that depends on channel characteristics and configuration. This latency produces bias in range measurements which causes errors in position estimation. Our method produces a fixed-time low-latency synchronization of sub-chip timing precision, via oversampling. Utilizing single bit quantization we are able to use exclusive-OR (XOR) based operations instead of expensive multiply-accumulate (MAC) functions. This reduces the hardware utilization significantly, allowing more logic efficiency. The proposed approach is particularly critical for hardened FP-GAs that have applications in space and extreme environments. © 2013 IEEE