Georeferencing of UK DMC stereo-images without ground control points by exploiting geometric distortions

This article describes a new method for the georeferencing of UK-DMC imagery that does not require ground control points (GCPs). The proposed method utilizes satellite ancillary data, and the inter-imager offsets to determine the geolocation of individual pixels. The major step involved is the direct georeferencing of each pixel using satellite GPS and attitude sensor observations. The known separation between the sensors will allow us to determine the geolocations of all pixels that are taken at the same time using the same exterior orientation parameters. Traditional methods for georeferencing use GCPs, which are expensive and time-consuming tasks. Moreover, the traditional method is not suitable for a pushbroom imager because every scan line has a different set of exterior orientation parameters. Therefore, we propose a direct georeferencing approach without GCPs. The major source of error in direct georeferencing is the error in attitude measurements. The reason for this error is considered to be the thermo-elastic effects on the satellite, which affect the sensors’ positioning, causing deformation in the images. These effects have been modelled as a transformation matrix that describes the extent of deformation in the imagery, and is estimated by exploiting the geometric distortions in stereo Earth images. For this purpose, a mathematical model has been developed to demonstrate how inter-image offsets have been introduced into the imagery and affected by thermal deformation. The mathematical model is based on the sensor configuration of UK-DMC satellites. The model has been further inverted to extract the thermal deformation at a given row and column offset. The thermal deformation matrix has been found to mitigate the pointing error up to 1 km. The accuracy of the thermal deformation estimates is highly dependent on the accuracy of image offsets. The accuracy of image offsets is dependent on several factors, which include the image registration method, window size, along-track separation between the sensors, satellite attitude, and resolution of the sensors.     

基于虚拟力的混合感知网节点部署

感知网一般是由静态的或移动的节点组成,为保证感知网的感知功能,节点应该有自部署和自修复能力.然而全部由移动传感器组成的感知网的成本太高,为保证感知网的覆盖功能和低成本,提出了一种在静态传感器节点中加入移动传感器节点的混合感知网形式.为了更好地部署这些节点,最大化覆盖待感知区域,提出了一种基于节点间虚拟力的移动节点部署方法,利用静态节点和移动节点以及移动节点之间的虚拟人工势场产生的作用力来控制移动节点的运动,使移动节点能够在较短的时间内,以较少的能量消耗到达自己合适的位置.在理论上分析了算法的可行性,用仿真实验验证了此算法的有效性,并和其他3种类似算法进行了性能比较.     

A new space and time sensor fusion method for mobile robot navigation

To fully utilize the information from the sensors of mobile robot, this paper proposes a new sensor‐fusion technique where the sample data set obtained at a previous instant is properly transformed and fused with the current data sets to produce a reliable estimate for navigation control. Exploration of an unknown environment is an important task for the new generation of mobile service robots. The mobile robots may navigate by means of a number of monitoring systems such as the sonar‐sensing system or the visual‐sensing system. Notice that in the conventional fusion schemes, the measurement is dependent on the current data sets only. Therefore, more sensors are required to measure a given physical parameter or to improve the reliability of the measurement. However, in this approach, instead of adding more sensors to the system, the temporal sequences of the data sets are stored and utilized for the purpose. The basic principle is illustrated by examples and the effectiveness is proved through simulations and experiments. The newly proposed STSF (space and time sensor fusion) scheme is applied to the navigation of a mobile robot in an environment using landmarks, and the experimental results demonstrate the effective performance of the system. © 2004 Wiley Periodicals, Inc.     

Design and analysis of a z-axis tuning fork gyroscope with guided-mechanical coupling

This paper presents design and analysis of a z-axis tuning fork gyroscope. The sensor is designed to reduce noises and improve the sensitivity by using a drive coupling spring in the lozenge shape. The in-phase sensing mode is suppressed by using a self-rotation ring. The designed sensor prioritizes anti-phase driving and sensing modes. The frequencies of anti-phase driving and sensing modes are far from those of parasitic ones. The design also enables the sensing mode to decouple from the driving one, which is considered to decrease vibration-induced error. The proposed sensor structure is analyzed by finite element method. The simulated frequencies of the driving and sensing modes are 9.9 and 10.0 kHz, respectively, which show the bandwidth of sensor of 100 Hz. The frequency difference between the driving and sensing modes and the parasitic ones is obtained to be 50 %. The optimized gap between electrodes leads to the determination of the number of the sensing capacitor fingers and consequently the suitable dimension parameters of the whole device. The sensor performance in the time domain and the frequency domain having the transient response to a given rotation rate is also simulated showing the linear dependence of capacitance change on angular velocity. As a result, the sensitivity of the sensor is evaluated to be 11 fF/°/s.     

Vehicle navigation in GPS denied environment for smart cities using vision sensors

The transformation of the existing urban environment in digital smart cities has become a reality, which aimed to transform daily life activities into automated processes for the ease in human efforts and reduction in effort time. Vision based sensors are commonly used for monitoring cities, which acquire a huge amount of diverse data and store them for further computer vision processing. In this article, we aim to explore whether and how to navigate a vehicle using cost effective means (vision based sensors) in smart cities without using the calibrated sensors and Global Positioning System (GPS). Vehicle localization and navigation require on-board calibrated sensors and reliable GPS link. In an urban environment, these sensors fail to perform well in: indoor environment (tunnels), crowded and congested areas, and severe weather conditions. The most effective technique used for vision based navigation depends on image registration. The challenges of a successful and effective registration are: sufficient illumination in the environment, dominance of static scene over moving objects, high textured ratio to allow apparent motion and necessary scene overlap between consecutive frames. We proposed a novel approach for vehicle navigation based on vision sensors using modified normalized phase correlation. In the proposed approach, the distinction between textured and texture less surface is based on the identification of corresponding features. In this regard, the Gram polynomial basis function is used to remove the Gibbs error problem generated due to peak in the registration process. Similarly, entropy based tensor approximation is used to remove outliers for robust image registration. Experiments performed in real time during test drives show excellent results with respect to estimated position accuracy in comparison with GPS calculated data.     

On the problem of k-coverage in mission-oriented mobile wireless sensor networks

The problem of sensor deployment to achieve k-coverage of a field, where every point is covered by at least k sensors, is very critical in the design of energy-efficient wireless sensor networks (WSNs). It becomes more challenging in mission-oriented WSNs, where sensors have to move in order to k-cover a region of interest in the field. In this type of network, there are multiple missions (or monitoring tasks) to be accomplished, each of which has different requirements, particularly, in terms of coverage. In this paper, we consider the problem of k-coverage in mission-oriented mobile WSNs which we divide into two sub-problems, namely sensor placement and sensor selection. The sensor placement problem is to identify a subset of sensors and their locations in a region of interest so it is k-covered with a small number of sensors. The sensor selection problem is to determine which sensors should move to the above-computed locations in the region while minimizing the total energy consumption due to sensor mobility and communication. Specifically, we propose centralized and distributed approaches to solve the k-coverage problem in mission-oriented mobile WSNs. Our solution to the sensor placement problem is based on Helly’s Theorem and the geometric analysis of the Reuleaux triangle. First, we consider a deterministic (or disk) sensing model, where the sensing range is modeled as a disk. Then, based on the above analysis, we address the k-coverage problem using a more realistic sensing model, known as probabilistic sensing model. The latter reflects the stochastic nature of the characteristics of the sensors, namely sensing and communication ranges. Our centralized and distributed protocols enable the sensors to move toward a region of interest and k-cover it with a small number of sensors. Our experiments show a good match between simulation and analytical results. In particular, simulation results show that our solution to the k-coverage problem in mission-oriented mobile WSNs outperforms an existing one in terms of the number of sensors needed to k-cover a region of interest in the field and their total energy consumption due to communication, sensing, and mobility for the correct operation of the protocol.     

Meter-scale large-area capacitive pressure sensors with fabric with stripe electrodes of conductive polymer-coated fibers

We developed meter-scale large-area capacitive fabric pressure sensors for floor sensors to monitor human position. In the fabric pressure sensor, two fabrics with stripe electrodes of conductive polymer-coated fibers woven into them were stacked vertically, and the capacitance changes between the top and bottom stripe electrodes were measured when pressure was applied. By using the die-coating of a conductive polymer and weaving the resultant fibers with meter-scale automatic looming machines, the 1 m × 1 m area with stripe electrodes at a 20 cm pitch was constructed. The pressure sensitivity, which depends on the number of the sensor fibers forming the stripe electrodes, was characterized and optimized to increase output capacitance change. The stripe electrodes with five sensor fibers were found to exhibit a capacitance change of 1.37 pF when pushed with the average foot pressure (i.e., 2.6 N/cm²), which is large enough to detect with conventional capacitance measurement circuits. Finally, pressure sensing with our woven pressure sensor fabric is demonstrated. Our meter-scale pressure sensor fabric technology will be used for bed and floor sensors for monitoring old people in nursing homes and hospitals.     

Fabrication of micro-capacitive inclination sensor by resin molding

Capacitive inclination sensors have the advantage that they can easily provide a linear analog output with respect to inclination. Although inclination sensors featuring this advantages are already commercially available, they are generally too large. We fabricated a micro-capacitive inclination sensor by a combination of a resin forming method and a mold. Electrodes of the sensor are 40 μm in a gap and 12 mm² in area. The sensor detects difference of capacitance, which varies with movement of silicone oil accompanying with inclination of the sensor. Since the dimensions of the sensing region are 5 × 5 × 3 mm³ this inclination sensor is expected to be widely used in fields where efficient and reliable position control is a primary factor to be considered. The use of resins is also expected to contribute to a reduction in the costs of materials. We successfully fabricated a micro inclination sensor as a molded product. In future, we will wire up the device to complete this inclination sensor, and will then conduct performance evaluations. If techniques using resin-molded parts are introduced to the low-cost mass-production of Micro Electro Mechanical Systems devices, the range of applications will further expand to new areas of technology and industry.     

海上溢油遥感探测技术及其应用进展

介绍了海上溢油遥感探测常用的可见光、红外、紫外光学遥感器、微波辐射计、雷达、激光荧光器和油层厚度探测器等几种溢油遥感探测器的探测原理、能力及应用状况。可见光仪器的溢油探测能力非常有限；红外遥感器是有一定探测能力的最为实用的探测器；微波遥感具有全天候的特点，但空间分辨率低，识别能力也有一定的限制；而激光荧光器和油层厚度探测器等激光遥感器则是最有发展前景的一类溢油探测器。通过性能等方面的对比分析以及当前实际应用情况，分析了未来溢油遥感技术的发展趋势。     

Error sources on the land surface temperature retrieved from thermal infrared single channel remote sensing data

In this paper, a theoretical study complementary to others given in the literature about the errors committed on the land surface temperature retrieved from the radiative transfer equation in the thermal infrared region by remote sensing techniques has been analysed. For this purpose, the MODTRAN 3.5 code has been used in order to simulate different conditions and evaluate the influence of several parameters on the land surface temperature accuracy: atmospheric correction, noise of the sensor, land surface emissivity, aerosols and other gaseous absorbers, angular effects, wavelength uncertainty, full‐width half‐maximum of the sensor and band‐pass effects. The results show that the most important error source is due to atmospheric effects, which leads to an error on surface temperature between 0.2 K and 0.7 K, and land surface emissivity uncertainty, which leads to an error on surface temperature between 0.2 and 0.4 K. Hence, assuming typical uncertainties for remote sensing measurements, a total error for land surface temperature between 0.3 K and 0.8 K has been found, so it is difficult to achieve an accuracy lower than these values unless more accurate in situ values for emissivity and atmospheric parameters are available.     

A farmland multimedia data collection method using mobile sink for wireless sensor networks

Wireless sensor networks are applied to collect the information about farmland required to achieve unmanned agriculture. The major purpose of the deployed sensors is to collect data. However, if the data collected by the sensors are too large, such as an image, sensors quickly become unavailable. In this paper, a novel method for collecting image data from deployed sensors by using a mobile sink is proposed. Unlike the existing data gathering methods, in which sensors deliver data to a sink via long distance transmission, in the proposed method the mobile sink walks within the region of interest (ROI) to harvest the data. A virtual-grid method is proposed to determine the visiting locations of the mobile sink. An algorithm to eliminate redundant locations that uses set-conjunction operations is also proposed for reducing the number of unnecessary visiting locations. In addition, a cross-edge adjusting trajectory scheduling (CATS) algorithm is proposed to reduce the moving distance of the mobile sink. Simulation results show that the proposed virtual-grid method can effectively reduce the number of visiting locations by about 15–20 % as compared to the cluster-centroid method. The CATS algorithm can also shorten the moving distance of the mobile sink by about 25 % as compared to that of a heuristic minimum spanning tree method.     

Fabrication of high precision microstructure using ICP etching for capacitive inclination sensor

Capacitive inclination sensors have the advantage because it could easily provide a linear analog output with respect to inclination. Since the dimensions of the sensing region are very small, then this sensor is expected to be widely used in fields where efficient and reliable position control is a primary factor to be considered if this sensor could be mass produced at low cost. Therefore, we proposed fabrication process based on transfer to resin using mold. We successfully fabricated a micro capacitive inclination sensor by a combination of a resin forming method and a mold. The sensor consists of a gap distance of 80 μm between its electrodes. The sensor detects difference of capacitance, which varied with movement of silicone oil accompanying with inclination. When the sensor was inclined, linear analog output was obtained within the range of ?45 to +45°     

Multi-sensor data fusion methods for indoor localization under collinear ambiguity

Sensor node localization in mobile ad-hoc sensor networks is a challenging problem. Often, the anchor nodes tend to line up in a linear fashion in a mobile sensor network when nodes are deployed in an ad-hoc manner. This paper discusses novel node localization methods under the conditions of collinear ambiguity of the anchors. Additionally, the work presented herein also describes a methodology to fuse data available from multiple sensors for improved localization performance under conditions of collinear ambiguity. In this context, data is first acquired from multiple sensors sensing different modalities. The data acquired from each sensor is used to compute attenuation models for each sensor. Subsequently, a combined multi-sensor attenuation model is developed. The fusion methodology uses a joint error optimization approach on the multi-sensor data. The distance between each sensor node and anchor is itself computed using the differential power principle. These distances are used in the localization of sensor nodes under the condition of collinear ambiguity of anchors. Localization error analysis is also carried out in indoor conditions and compared with the Cramer–Rao lower bound. Experimental results on node localization using simulations and real field deployments indicate reasonable improvements in terms of localization accuracy when compared to methods likes MLAR and MGLR.     

Optimally overlapped ultrasonic sensor ring design for minimal positional uncertainty in obstacle detection

This paper presents the optimal overlapping arrangement of a circular array of ultrasonic sensors for minimal positional uncertainty in obstacle detection. First, it is shown that beam overlap among three adjacent ultrasonic sensors leads to significant reduction of positional uncertainty. Second, the positional uncertainty of an overlapped ultrasonic sensor ring is compared to a single ultrasonic sensor in terms of a collision-free region with obstacles. Third, the optimal design index for an overlapped ultrasonic sensor ring is defined as the area closest between the non-overlapped and overlapped sensing sub-zones. Fourth, using commercial low directivity ultrasonic sensors, an optimally overlapped ultrasonic sensor ring is given along with its prototype installed on top of a mobile robot. Finally, experimental results are given to demonstrate the validity and performance of our overlapped ultrasonic sensor ring prototype.     

Component design and testing for a miniaturised autonomous sensor based on a nanowire materials platform

We present the design considerations of an autonomous wireless sensor and discuss the fabrication and testing of the various components including the energy harvester, the active sensing devices and the power management and sensor interface circuits. A common materials platform, namely, nanowires, enables us to fabricate state-of-the-art components at reduced volume and show chemical sensing within the available energy budget. We demonstrate a photovoltaic mini-module made of silicon nanowire solar cells, each of 0.5 mm² area, which delivers a power of 260 μW and an open circuit voltage of 2 V at one sun illumination. Using nanowire platforms two sensing applications are presented. Combining functionalised suspended Si nanowires with a novel microfluidic fluid delivery system, fully integrated microfluidic–sensor devices are examined as sensors for streptavidin and pH, whereas, using a microchip modified with Pd nanowires provides a power efficient and fast early hydrogen gas detection method. Finally, an ultra-low power, efficient solar energy harvesting and sensing microsystem augmented with a 6 mAh rechargeable battery allows for less than 20 μW power consumption and 425 h sensor operation even without energy harvesting.     

基于局部信息的移动感知网覆盖方法

移动感知网是一个由许多带有传感器的自主移动机器人组成的分布式传感器网络。为了更好地部署这些移动机器人节点,形成最大化覆盖感知区域,提出了一种基于机器人局部信息的分布式感知网覆盖方法。每个节点利用与邻居节点之间的虚拟人工势场产生的虚拟作用力来控制移动节点的运动和节点间的避碰,使移动节点能够在允许的时间内,以较少的能量消耗移动到各自理想的位置。采用李亚普诺夫函数进行了感知网节点势场梯度的理论分析,用计算机仿真实验验证了该方法的有效性,并与模拟退火算法进行了性能比较。     

Adaptive data acquisition strategies for energy-efficient, smartphone-based, continuous processing of sensor streams

There is a growing interest in applications that utilize continuous sensing of individual activity or context, via sensors embedded or associated with personal mobile devices (e.g., smartphones). Reducing the energy overheads of sensor data acquisition and processing is essential to ensure the successful continuous operation of such applications, especially on battery-limited mobile devices. To achieve this goal, this paper presents a framework, called ACQUA, for ‘acquisition-cost’ aware continuous query processing. ACQUA replaces the current paradigm, where the data is typically streamed (pushed) from the sensors to the one or more smartphones, with a pull-based asynchronous model, where a smartphone retrieves appropriate blocks of relevant sensor data from individual sensors, as an integral part of the query evaluation process. We describe algorithms that dynamically optimize the sequence (for complex stream queries with conjunctive and disjunctive predicates) in which such sensor data streams are retrieved by the query evaluation component, based on a combination of (a) the communication cost & selectivity properties of individual sensor streams, and (b) the occurrence of the stream predicates in multiple concurrently executing queries. We also show how a transformation of a group of stream queries into a disjunctive normal form provides us with significantly greater degrees of freedom in choosing this sequence, in which individual sensor streams are retrieved and evaluated. While the algorithms can apply to a broad category of sensor-based applications, we specifically demonstrate their application to a scenario where multiple stream processing queries execute on a single smartphone, with the sensors transferring their data over an appropriate PAN technology, such as Bluetooth or IEEE 802.11. Extensive simulation experiments indicate that ACQUA’s intelligent batch-oriented data acquisition process can result in as much as 80 % reduction in the energy overhead of continuous query processing, without any loss in the fidelity of the processing logic.     

基于MEMS技术的复合型智能传感器设计

把微机电系统(MEMS)技术的加速度敏感元件和微处理器有机结合,借助智能算法,设计了一种多功能的复合传感器,可同时测量运动物体的的振动、冲击和倾斜角度。试验表明:该传感器能够足够同时精确地检测运动物体的振动、冲击和倾斜角度信息,用于汽车中时,能够及时检测汽车的动态信息与车体的姿态。     

含障碍物区域的移动传感器网络部署算法*

针对感知区域内含障碍物的移动传感器网络(MSN)的优化问题,提出一种基于免疫算法与维诺图的移动传感器部署算法。共分为两个阶段：第一阶段,使用多目标免疫算法最大化网络覆盖率并最小化MSN移动与感知的能耗,使用维诺图调节传感器的感知范围;第二阶段：采用基于二值抗体的免疫算法调节传感器的状态,在保持高覆盖率的前提下,最小化节点感知与冗余覆盖引起的能耗。多组仿真实验结果显示,本算法对于有、无障碍的两种场景均获得了较好的覆盖率与能耗指标,并实现了较低的处理时间。     

Effect of piezoresistor configuration on output characteristics of piezoresistive pressure sensor: an experimental study

Piezoresistive sensing is one of the most frequently used transduction mechanism in pressure sensors. The piezoresistor placement on the diaphragm and the piezoresistor configuration play a pivotal role in determining the output characteristics of a pressure sensor. In this work, two different pressure sensors with different transverse piezoresistor configurations are studied to determine the effect of piezoresistor configuration on the sensitivity and non-linearity of the pressure sensors. A sensor structure with a square diaphragm size of 1,480 µm edge length and diaphragm thickness of 50 µm is chosen for the study. The design considerations for piezoresistor placement and the piezoresistor shapes are discussed in detail. The sensors are fabricated with bulk micromachined diaphragm and polysilicon piezoresistors. The sensor characteristics are determined for three temperatures, namely, ?5, 25 and 55 °C and for a pressure range of 0–30 Bar. The characterization results indicate that the design with two piezoresistor arms in transverse piezoresistor configuration (2 × 2 Design) has higher sensitivity than the single arm configuration (2 × 1 Design) by about 25 % at 25 °C but it also has a higher non-linearity. The study shows the importance of selecting the proper piezoresistor configuration in the design of pressure sensors.