基于天文/GPS的HEO卫星自主导航方法

为了实现大椭圆轨道(HEO)卫星高精度自主导航,提出一种将直接敏感地平天文导航与全球定位系统(GPS)相结合的组合导航方法.首先,分析卫星轨道??2运动模型及其所受空间摄动,建立卫星轨道动力学模型;然后,分析单一使用天文导航和GPS的优缺点,根据HEO卫星对GPS的可见性,提出在远地点只采用天文导航,而在近地点采用以天文导航为主、适时引入GPS信号进行位速测量辅助修正的方法.通过计算机仿真和结果分析表明了所提出的设计方法导航精度比单一天文导航提高72.4%～85.6%.     

基于MEMS的低成本SINS/GPS组合导航系统研究

采用低成本的MEMS惯性传感器搭建了捷联惯导系统硬件平台,在此基础上对SINS/GPS组合导航系统进行实验研究.实验结果表明:系统精度比单纯的惯导系统高,接近GPS精度,达到了使用要求.同时,给出了MEMS捷联惯导系统的姿态解算算法,并进行实验验证.     

A MEMS surface fence for wall shear stress measurement with high sensitivity

In this paper, an optimized micro-fabricated surface fence with high sensitivity is presented for measurement of wall shear stress. In order to improve the bending stress and thereby enhance the sensitivity of the sensor, the cantilever structure of sensor (the sensing element) is designed and optimized by optimization analysis and orthogonal experimental design. Several sensors are fabricated using the micromachining technology with the sensing element having a width of 5 mm, a thickness of 20 μm and a height of either 2,200 or 1,700 μm. Calibration against a Preston Tube over a range of approximately ±0.7 Pa demonstrates that the sensors have sensitivity extended up to 2.3 mV/(V·Pa), at least 13 % improvement in sensitivity compared to the previous MEMS surface fence with the same thickness of sensing element. The paper also introduces an acoustic excitation method to detect the resonant frequency of the MEMS surface fence, which features a very little deviation compared with the modal FE-analysis.     

卫星导航信号高灵敏度接收技术研究

随着卫星导航应用范围不断拓展,对导航接收机的灵敏度要求越来越高,高灵敏度可以使接收机在室内或其他卫星信号较弱情况下仍然能够实现定位和跟踪。目前传统接收机为超外差中频采样结合基带信号处理架构,该架构降低了对ADC信号采集以及基带信号处理的压力,但接收机灵敏度性能已趋于极限。随着ADC技术的不断发展,对卫星导航信号进行直接数字采样已渐渐成为现实。提出了一种基于高速ADC对卫星导航信号进行直接数字采样的方案,通过与传统超外差中频采样方案对比分析、仿真论证及实际测试,验证了新方案切实可行,并且能较大程度提升接收机灵敏度等关键技术指标,具有明显的技术优势。     

Pedestrian navigation using the sense of touch

Haptics is a feedback technology that takes advantage of the human sense of touch by applying forces, vibrations, and/or motions to a haptic-enabled user device such as a mobile phone. Historically, human–computer interaction has been visual, data, or images on a screen. Haptic feedback can be an important modality in Mobile Location-Based Services like – knowledge discovery, pedestrian navigation and notification systems. In this paper we describe a methodology for the implementation of haptics in four distinct prototypes for pedestrian navigation. Prototypes are classified based on the user’s navigation guidance requirements, the user type (based on spatial skills), and overall system complexity. Here haptics is used to convey location, orientation, and distance information to users using pedestrian navigation applications. Initial user trials have elicited positive responses from the users who see benefit in being provided with a “heads up” approach to mobile navigation. We also tested the spatial ability of the user to navigate using haptics and landmark images based navigation. This was followed by a test of memory recall about the area. Users were able to successfully navigate from a given origin to a Destination Point without the use of a visual interface like a map. Results show the users of haptic feedback for navigation prepared better maps (better memory recall) of the region as compared to the users of landmark images based navigation.     

A new hybrid fabrication process for a high sensitivity MEMS microphone

A novel multi-layer stacking capacitive type microphone is designed in this study based on theoretical analysis and numerical simulations, while fabricated via two standard stable silicon-based MEMS processes—PolyMUMPs and SOIMUMPs. The adoption of two standardized processes helps greatly to increase yield rate. The sensitivity of the microphone is first determined by an analytical model based on an equivalent circuit, which is followed by finite element (FEM) analyses on the capacitance value, static pull-in voltage and dynamic characteristics. Based on the developed analytical model, varied dimensions of the microphone are optimized and then the performance is validated by analytical simulations. In the next step, micro-fabrication of the microphone is accomplished using two standard processes, PolyMUMPs and SOIMUMPs provided by MEMSCAP. Experiments are conducted to acquire the information of pull-in voltage for safe operation and frequency response in sensitivity for performance evaluation. In the static case, experimental results show a good agreement with the analytical results with 90 Mpa residual stress assumed. As for dynamic validation, the frequency response is measured in an anechoic room adopting the exciting frequency as the audible range from 100–10 kHz. The measured sensitivity is as around 0.78 and 1.7 mV/Pa from 100 to 10 kHz, under the biases of 2 and 4.5 V, respectively. Within the audible frequency range, the proposed device maintains the loss as less as 2.7 dB (ref. to V/Pa), under 3 dB—the commonly acceptable drop within audible frequency range.     

Pedestrian navigation aids: information requirements and design implications

Recent years have seen an increased interest in navigational services for pedestrians. To ensure that these services are successful, it is necessary to understand the information requirements of pedestrians when navigating, and in particular, what information they need and how it is used. A requirements study was undertaken to identify these information requirements within an urban navigation context. Results show that landmarks were by far the most predominant navigation cue, that distance information and street names were infrequently used, and that information is used to enable navigation decisions, but also to enhance the pedestrians confidence and trust. The implications for the design of pedestrian navigation aids are highlighted.     

MEMS技术在车载导航中的应用

基于MEMS技术,对由加速度计、磁场计和倾角传感器构成的车载导航仪进行了理论分析,对系统信息融合和软硬件设计进行了研究.在嵌人式平台上实现了组合导航系统,实时提供车载体的姿态、速度和位置信息,满足导航需求.通过实验对导航系统的可靠性和稳定性进行了分析研究,得出导航系统精度与误差满足车载体导航要求的结论.     

基于MEMS惯性传感器的行人航位推算系统

提出一种基于低成本MEMS自包含传感器,能自主完成数据采集、数据处理的行人航位推算（PDR）系统.硬件平台集成三轴加速度计、三轴陀螺仪、三轴数字罗盘及气压计,不需任何额外设施.通过自包含传感器测量行人行走的步长、方位及高度,实现行人室内、外三维定位.采用加速度信号实现跨步探测和步长估计.利用互补滤波器融合加速度计、陀螺仪和数字罗盘数据,矫正陀螺仪的测量误差和磁场干扰对数字罗盘的影响,提高行人行走的方位精度.测试结果表明：系统的定位误差低于行进距离的4％,满足行人定位要求.验证了系统的有效性和可靠性.     

基于运动姿态识别的行人惯性导航算法

针对室内定位惯性导航算法存在累积误差的问题,提出了一种基于运动姿态识别的行人惯性导航算法.在捷联惯性导航算法的基础上,引入了行人脚部姿态识别方法,将行人的位移以单步长为单位进行惯性导航解算.使用姿态识别与零速修正相结合确定每一步的静止时刻,改进步数检测结果,并对行人静止时刻的速度和位置信息进行校正,以降低累积误差;统计前期误差较小的行人惯性导航数据,并建立步频—步长模型,根据行人实时的步频和方向变化对当前步长进行校准,在行人以惯常运动姿态或运动姿态变化时分别采取对应的步长估计算法,以保证导航算法的准确性.实验结果表明:与传统捷联惯性导航算法相比,提出的算法提高了长距离导航的精度.     

Design optimisation of high sensitivity MEMS piezoresistive intracranial pressure sensor using Taguchi approach

Microsystem Technologies - MEMS piezoresistive pressure sensors have been contemporarily used to measure intracranial pressure. Since an intracranial signal is of the pulsating type, the...     

A MEMS piezoelectric solid disk gyroscope with improved sensitivity

Microsystem Technologies - This paper introduces a MEMS piezoelectric solid disk gyroscope. The gyroscope operates in an in-plane elliptic bulk acoustic wave mode with a frequency of...     

Model and experiment of scale factor acceleration sensitivity of MEMS gyroscope in high acceleration environment

With the development of MEMS gyroscope, acceleration sensitivity is becoming an important factor in application. The acceleration sensitivity would produce an obvious output error, and researchers mainly focus on bias acceleration sensitivity. Yet, in environment of high acceleration and angular rate, it is the scale factor acceleration sensitivity that influences the output most, and there is little research on it. In this paper, scale factor acceleration sensitivity of MEMS gyroscope in high acceleration environment is investigated with our established theoretical model and experimental measurement. Based on our proposed method of measuring the acceleration sensitivity in environment of high acceleration and angular rate, the MEMS tuning fork gyroscope is used for the measurement. The results show that the output error caused by acceleration can be up to − 30.1°/s and the scale factor acceleration sensitivity contributes the most. The coefficient of scale factor acceleration sensitivity is 35 ppm/g under 50g acceleration, and this coefficient increases linearly with acceleration that coincides with theoretical model. Lastly, some suggestions of decreasing scale factor acceleration sensitivity are given. This work is useful for the researchers to improve the performance of acceleration sensitivity of MEMS gyroscope.

     

Retraction Note: A new structure and modeling of a three-axis MEMS capacitive accelerometer with high dynamic range and sensitivity

Microsystem Technologies -     

RETRACTED ARTICLE: A new structure and modeling of a three-axis MEMS capacitive accelerometer with high dynamic range and sensitivity

Microsystem Technologies - In this paper, a three-axis capacitor accelerator has been analyzed, modeled and optimized using micro-electromechanical systems technology. In the proposed structure,...     

滚转条件下单天线GPS跟踪算法设计

提出了一种滚转条件下的单天线GPS跟踪算法。该算法能够在较低转速下,对间断的GPS信号进行跟踪,同时能够准确地计算出弹丸的滚转速度。该方法首先对单天线滚转条件下的接收信号进行分析与建模。然后,基于滚转对接收到的卫星信号的幅度调制特性的影响,利用旋转时信号幅度的对称性进行解旋,从而得到弹丸的滚动速率和角度。实际测试结果表明,利用信号的I/Q幅值信息,可以实时计算滚转弹丸的滚动速率和滚动角度,并且计算精度可以满足大多数实际应用的要求。     

MEMS-IMU/GPS/GPRS组合导航方案设计与实现

针对日益增长的低成本导航定位需求,提出了一个MEMS-IMU/GPS/GPRS组合导航方案,以MEMS-IMU模块和SIM908单板机为载体,以GPRS为通讯手段,实时获取GPS/IMU位姿信息.并编写程序分别对GPS和IMU数据进行预处理并以松组合方式进行组合导航数据融合.为验证系统的可靠性和精度,进行了实际静态试验和车载实验,事后数据处理分析结果表明,提出的低成本组合导航系统具有一定的可靠性,导航定位精度达到分米级.     

New anti-jamming technique for GPS and GALILEO receivers using adaptive FADP filter

Anti-jamming techniques to improve Global Positioning System (GPS) receiver's robustness have been mainly developed in military applications. None of civilian techniques can procure sufficient robustness against occasional or intentional jammers for civil GPS or GALILEO navigation receivers. The amplitude domain processing (ADP) filtering is a technique based upon Capon works and Neyman–Pearson theory. Several experiments concerning the ADP filtering have been considered at the 3DETSNAV division of LACIME laboratory at Ecole de technologie supérieure (ETS), which have proved that the technique is reliable in order to eradicate powerful interference present in the spread spectrum signal. However, the results show that the ADP filter has a real limitation when submitted to multiple interference scenarios. This paper shows that working in the frequency domain is more efficient because jamming signals added to a white Gaussian noise are easier to detect and to attenuate when represented in the frequency domain. The present paper gives mathematical elements to complete the ADP theory in the frequency domain and presents the performances of an ADP in the frequency domain (FADP) filter simulated in a Matlab Simulink environment. The filter is tested with a signal composed of a GPS C/A code (Gold sequence) drowned in a white Gaussian noise in presence of one or several additional jammers (CWI, PWI, chirp). Several analyses are made upon the filter output (signal to noise ratio, attenuation and power spectral density measurements). The results of the analysis show that the FADP can eradicate any kind of jammers of 20 dB above white Gaussian noise. Correlation losses are measured; they are always under 0.5 dB. In the presence of one or two jammers, the performances of the FADP filter are better than those of the ADP filter. The FADP filter can procure up to 20 dB processing gain with a maximum of 10 dB loss on SNR in worse jamming scenario. When the number of jammers increases, the performances remain convenient, whereas the time-domain ADP filter becomes unable to be effective. In this paper, measurements are made with a number of jammers up to 15.     

Optimization and design of a novel prescaler and its application to GPS receivers

In this work,a novel prescaler based upon new current mode logic (CML) flip-flop architecture applied to global positioning system (GPS) receivers is proposed.Compared to traditional static current mode logic (CML) flip-flop,it introduces a clock-controlling transistor to reduce the time constant at sensing period.As a result,the speed has been maximized and the working range has been enlarged.The phase noise of local oscillator (LO) signals coming from the prescaler can be lowered by 6 dB,and the interfere...     

GPS/INS组合导航及其数据同步的研究

建立在惯性原理基础上的惯性导航系统不需要任何外来信息,也不会向外辐射任何信息,仅靠惯性导航系统本身就能全在天候条件下在全球范围内和任何介质环境里自主地隐蔽地进行连续的三维定位和定向:但它也存在误差随时间积累的缺点.而GPS导航系统能提供长时间的高精度定位;但存在1 HZ慢速数据修正速率的缺陷.本文研究二者互补的组合导航系统,建立了组合导航的软件和硬件模型,并提出了基于卡尔曼滤波的导航实现算法.