Hybrid pedestrian positioning system using wearable inertial sensors and ultrasonic ranging

Pedestrian positioning system(PPS)using wearable inertial sensors has wide applications towards various emerging fields such as smart healthcare,emergency rescue,soldier positioning,etc.The performance of traditional PPS is limited by the cumulative error of inertial sensors,complex motion modes of pedestrians,and the low robustness of the multi-sensor collaboration structure.This paper presents a hybrid pedestrian positioning system using the combination of wearable inertial sensors and ultrasonic ranging(H-PPS).A robust two nodes integration structure is developed to adaptively combine the motion data acquired from the single waist-mounted and foot-mounted node,and enhanced by a novel ellipsoid constraint model.In addition,a deep-learning-based walking speed estimator is proposed by considering all the motion features provided by different nodes,which effectively reduces the cumulative error originating from inertial sensors.Finally,a comprehensive data and model dual-driven model is presented to effectively combine the motion data provided by different sensor nodes and walking speed estimator,and multi-level constraints are extracted to further improve the performance of the overall system.Experimental results indicate that the proposed H-PPS significantly improves the performance of the single PPS and outperforms existing algorithms in accuracy index under complex indoor scenarios.

An aerial ammunition ad hoc network collaborative localization algorithm based on relative ranging and velocity measurement in a highly-dynamic topographic structure

In the internet of battlefield things, ammunition is becoming networked and intelligent, which depends on location information. Therefore, this paper focuses on the self-organized network collaborative localization of munitions with an aerial three-dimensional(3D) highly-dynamic topographic structure under a satellite denied environment. As for aerial networked munitions, the measurement of munitions is objectively incomplete due to the degenerated and interrupted link of munitions. For this reason, a cluster-oriented collaborative localization method is put forward in this paper. Multidimensional scaling(MDS) was first integrated with a trilateration localization method(TLM) to construct a relative localization algorithm for determining the relative location of a mobile cluster network. The information related to relative velocity was then combined into a collaborative localization framework to devise a TLM-vMDS algorithm. Finally, an iterative refinement algorithm based on scaling by majorizing a complicated function(SMACOF) was employed to effectively eliminate the influence of incomplete link observation on localization accuracy. Compared with the currently available advanced algorithms, the proposed TLM-vMDS algorithm achieves higher localization accuracy and faster convergence for a cluster of extensively networked munitions, and also offers better numerical stability and robustness for highspeed motion models.

Performance analysis of a novel chip tracking loop used for regenerative pseudo-noise ranging clock recovery

To improve the performance of composite pseudo-noise （PN） code clock recovery in a regenerative PN ranging system at a low symbol signal-to-noise ratio （SNR）, a novel chip tracking loop （CTL） used for regenerative PN ranging clock recovery is adopted. The CTL is a modified data transition tracking loop （DTTL）. The difference between them is that the Q channel output of the CTL is directly multiplied by a clock component, while that of the DTTL is multiplied by the Ⅰ channel transition detector output. Under the condition of a quasi-squareware PN ranging code, the tracking （ mean square timing jitter） performance of the CTL is analyzed. The tracking performances of the CTL and the DTTL, are compared over a wide range of symbol SNRs. The result shows that the CTL and the DTTL have the same performance at a large symbol SNR, while at a low symbol SNR, the former offers a noticeable enhancement.

A novel x-ray circularly polarized ranging method

Range measurement has found multiple applications in deep space missions. With more and further deep space ex- ploration activities happening now and in the future, the requirement for range measurement has risen. In view of the future ranging requirement, a novel x-ray polarized ranging method based on the circular polarization modulation is proposed, termed as x-ray circularly polarized ranging （XCPolR）. XCPolR utilizes the circular polarization modulation to process x-ray signals and the ranging information is conveyed by the circular polarization states. As the circular polarization states present good stability in space propagation and x-ray detectors have light weight and low power consumption, XCPolR shows great potential in the long-distance range measurement and provides an option for future deep space ranging. In this paper, we present a detailed illustration of XCPolR. Firstly, the structure of the polarized ranging system is described and the signal models in the ranging process are established mathematically. Then, the main factors that affect the ranging accuracy, including the Doppler effect, the differential demodulation, and the correlation error, are analyzed theoretically. Finally, numerical simulation is carded out to evaluate the performance of XCPolR.

基于WiMAX系统的初始Ranging检测算法

初始Ranging过程是WiMAX系统上行链路中的重要过程,首先对基于差分法的Ranging检测算法进行了深入分析,然后提出了一种改进算法,该改进算法提高了低SNR下的检测率,且时偏估计的准确度大大提高,能够直接支持超远距离覆盖,解决了WiMAX系统上行接入受限问题。最后通过计算机仿真比较了改进算法的性能,仿真结果表明,所提出的改进算法在技术复杂度和系统性能上具有较大的优势。

Dual-Comb Ranging

Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement.Using two coherent frequency combs,dual-comb ranging allows time and phase response to be measured rapidly.It breaks through the limitations related to the responsive bandwidth,ambiguity range,and dynamic measurement characteristics of conventional ranging tools.This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool.As optical frequency comb technology progresses,dualcomb ranging shows promise for various professional applications.

Bearing splitting and near-surface source ranging in the direct zone of deep water

Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.

IEEE802.16e多天线系统的初始ranging检测算法

针对初始ranging检测未与多天线通信系统特点相结合的问题,在比较分析了几种传统多天线合并数据算法的基础上,提出了一种时域与频域相结合的多天线系统初始ranging检测算法.该算法利用检测到各天线上用户时偏值,将接收到的多天线数据按信道条件分别处理,这样既最大程度利用了多天线分集增益又避免了此增益使检测误差变大,起到了抑制多径衰落的作用.仿真实验结果表明,该算法在多径衰落信道条件下实现高速移动通信的同时较传统检测方法拥有更好的检测性能.

Influence of high overload on the collimating lenses of laser ranging systems

Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.

X-ray communication based simultaneous communication and ranging

To improve the link efficiency and decrease the payloads in space explorations, a novel simultaneous communication and ranging method based on x-ray communication（XCOM） is proposed in this paper. A delicate signal symbol structure is utilized to achieve simultaneous data transmission and range measurement. With the designed symbol structure, the ranging information is imbedded into the communication signal and transmitted with it simultaneously. The range measurement is realized by the two-way transmission of the range information. To illustrate the proposed method, firstly, the principle of the method is introduced and the signal processing procedure is presented. Then, the performance of the proposed method is analyzed theoretically in various aspects, including the acquisition probability, the bit error rate, the ranging jitter,etc. Besides, numerical experiments are conducted to verify the proposed method and evaluate the system performance.The simulation results show that the proposed method is feasible and that the system performance is influenced by the parameters concerning the signal symbol structure. Compared with the previous methods, the proposed method improves the link efficiency and is beneficial for system miniaturization and integration, which could provide a potential option for future deep space explorations.

Development of a 170-mm hollow corner cube retroreflector for the future lunar laser ranging

Over the past 50 years, lunar laser ranging has made great contributions to the understanding of the Earth–Moon system and the tests of general relativity. However, because of the lunar libration, the Apollo and Lunokhod corner-cube retroreflector（CCR） arrays placed on the Moon currently limit the ranging precision to a few centimeters for a single photon received. Therefore, it is necessary to deploy a new retroreflector with a single and large aperture to improve the ranging precision by at least one order of magnitude. Here we present a hollow retroreflector with a 170-mm aperture fabricated using hydroxide-catalysis bonding technology. The precisions of the two dihedral angles are achieved by the mirror processing with a sub-arc-second precision perpendicularity, and the remaining one is adjusted utilizing an auxiliary optical configuration including two autocollimators. The achieved precisions of the three dihedral angles are 0.10 arcsecond,0.30 arc-second, and 0.24 arc-second, indicating the 68.5% return signal intensity of ideal Apollo 11/14 based on the far field diffraction pattern simulation. We anticipate that this hollow CCR can be applied in the new generation of lunar laser ranging.

Analyses of noncommensurate sampling used in high-precision regenerative pseudo-noise ranging systems

A high-precision pseudo-noise ranging system is often required in satellite-formation missions. But in an actual PN ranging system, digital signal processing limits the ranging accuracy, only level up with meter-scale. Using non-integer chip to sample time ratio, noncommensurate sampling was seen as an effective solution to cope with the drawback of digital effects. However, researchers only paid attention to selecting specific ratios or giving a simulation model to verify the effectiveness of the noncommensurate ratios. A qualitative analysis model is proposed to characterize the relationship between the range accuracy and the noncommensurate sampling parameters. Moreover, a method is also presented which can be used to choose the noncommensurate ratio and the correlation length to get higher phase delay distinguishability and lower range jitter. The simulation results indicate the correctness of our analyses and the optimal ranging accuracy can be up to centimeter-level with the proposed approach.

Performance analysis of an indoor UWB ranging system

To evaluate the ranging performance of impulse radio ultra wideband （IR-UWB） signals, an experiment is performed in a typical indoor environment. In order to mitigate the ranging error caused by theoretical algorithm and practical circuits, one way-time difference of the arrival （OW-TDOA） ranging method and corresponding approaches are proposed and carried out according to the structure of UWB transceivers. Generalized maximum likelihood （GML） estimator based on energy detection is applied for the time of arrival estimation. The obtained results show that this UWB ranging system can achieve a relative high ranging accuracy in a multipath environment （e.g. about 5 cm at ranges up to 6 m）, which is practical and meaningful for many sensor applications.

The use of laser ranging to measure space debris

Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avoidance. Laser ranging is a kind of real-time measuring technology with high precision for space debris observation. The first space-debris laser-ranging experiment in China was performed at the Shanghai Observatory in July 2008 with a ranging precision of about 60-80 cm. The experi- mental results showed that the return signals from the targets with a range of 900 km were quite strong, with a power of 40W （2J at 20 Hz） using a 10ns pulse width laser at 532 nm wavelength. The performance of the preliminary laser ranging system and the observed results in 2008 and 2010 are also introduced.

A correction method of encoder bias in satellite laser ranging system

In a satellite laser ranging telescope system, well-aligned encoders of the elevation and azimuth axes are essential for tracking objects. However, it is very difficult and time-consuming to correct the bias between the absolute-position indices of the encoders and the astronomical coordinates, especially in the absence of a finder scope for our system. To solve this problem, a method is presented based on the phenomenon that all stars move anti-clockwise around Polaris in the northern hemisphere. Tests of the proposed adjustment procedure in a satellite laser ranging （SLR）system demonstrated the effectiveness and the time saved by using the approach, which greatly facilitates the optimization of a trackin~ svstem.

Design, analysis and optimization of random access inter-satellite ranging system

In this paper, a random access inter-satellite ranging(RAISR) system is designed. The ranging accuracy is optimized by an algorithm to greatly improve the ranging accuracy. This paper verifies the feasibility of the RAISR system through a series of theoretical analysis, numerical simulation, hardware system design and testing. The research work brings the solution to the design and accuracy optimization problem of the RAISR system,which eliminates the main error caused by the satellite dynamic characteristics and frequency source drift of the RAISR system.The accuracy of the measurement system has been significantly improved.

Key technologies implementation of high-repetition-rate satellite laser ranging

Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation of high-repetition-rate SLR system. Compared with traditional technology, using kHz and 8ps pulse width laser component, the data quantity and quality of high-repetition-rate satellite laser ranging （SLR） can be significantly improved. The characteristics of high-repetition-rate laser ranging and the key technologies are presented, including the event timer with the precision of picosecond, the generation of range gate signal, and so on. All of them are based on the Field Programmable Gate Arrays （FPGA） and tested on China mobile SLR system-TROS1000. Finally, the observations of satellite Beacon-C are given.

A passive source ranging method based on the frequency warping transform of the vertical intensity flux in shallow water

The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component(MAC) and modal cross-correlation component(MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux(RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented.

Progress of the satellite laser ranging system TROS1000

The mobile satellite laser ranging system TROS1000, successfully developed in 2010, achieves a high repetition rate and enables daytime laser ranging. Its measurement range has reached up to 36000 km with an accuracy as precise as 1 cm. Using recent observations in Wuhan, Jiufeng, Xianning, and Rongcheng, Shandong, we introduce the progress made using this mobile observation system.

The progress of laser ranging technology at Shanghai Astronomical Observatory

As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological progress,There are a lot of improvements for overall system performance,such as annual observation passes,measurement precision and quality of observation data.SLR technology with repetition rate of 10 kHz is accomplished firstly in China,and space debris laser ranging technology with200 Hz laser is promoted and proved to be more detective for weak echo,which lead to successful measurement for 40,000 km satellites and space debris within 3000 km.At the same time,SLR based on multi-telescopes and 1064 nm wavelength are planned to make a breakthrough of detection capabilities,and also to expand its application fields.These progresses will be introduced in this paper in detail.