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Position Location and Navigation Symposium (PLANS), 2010 IEEE/ION

Date 4-6 May 2010

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Displaying Results 1 - 25 of 161
  • RS9000, a novel MEMS accelerometer family for Mil/Aerospace and safety critical applications

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (856 KB) |  | HTML iconHTML  

    Mid accuracy navigation and control systems require gyros and accelerometer to predict the position of a moving object in free space. Accelerometers are used to perform initial levelling and correct the gyro drift on the move. Typically, accelerometer with a range of ±10g with overall bias stability better than 2 mg and scale factor composite repeatability of better than 1000 ppm is required for the AHRS application. Current solutions in the market are mainly based on either vibrating quartz structures or traditional precision mechanics. These solutions suffer from high cost and fragility. MEMS is an inherently rugged technology and has great potential to bring forth novel solutions on the harsh environment and safety critical applications and enable new solutions due to its size, ruggedness and potential cost benefits. We report a new technological platform termed IRIS and a new accelerometer product based on that is called RS9000 family. RS9000 is interfaced with an open-loop electronic circuit and is comprised of a novel MEMS element designed specifically for high bias stability. RS9010 is a ±10g accelerometer with in run bias stability of better than 120µg, long term composite bias repeatability of better than 1.5mg, scale factor repeatability of 400ppm and vibration rectification of better than 65µg/g2. To our knowledge, this is the highest accuracy reported for a MEMS sensor operating in open-loop. View full abstract»

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  • SAR500 - A high-precision high-stability butterfly gyroscope with north seeking capability

    Publication Year: 2010 , Page(s): 6 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB) |  | HTML iconHTML  

    This paper describes a novel high-precision, low-noise, high-stability, calibrated and compensated digital oscillatory gyroscope with SPI interface, housed in custom-made ceramic packages. The device is factory-calibrated and compensated for temperature effects to provide high-accuracy digital output over a broad temperature range. Optimized tuning of the excitation and detection frequencies, as well as optimized mechanical and electrical balancing result in low sensitivity to shock and vibrations. By utilizing a unique sealed cavity technology, the vibrating elements of the gyroscope are contained within the low-pressure hermetic environment needed for high Q factors. Further on, improved stability of the device is achieved by full design symmetry, high thermal efficiency and choice of crystalline materials in the entire structure. View full abstract»

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  • The exploratory research of a Novel gyroscope based on superfluid Josephson effect

    Publication Year: 2010 , Page(s): 14 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    A new concept gyroscope based on superfluid Josephson effect was described and analyzed to improve the performance greatly. It is a new Sagnac effect that an interferometer “loop”, formed by placing double weak links in a toroid filled with superfluid He4, can detect the interference of superfluid matter waves generated by the AC Josephson oscillation in weak links. In this paper, the potential advantages of superfluid gyroscope were estimated. The most important advantage is the very high sensitivity which could be increased theoretically by a factor of 1010 than the sensitivity of traditional Ring Laser Gyroscope. But such a superfluid gyroscope still faces some difficulties when it is used as an angular velocity measuring device for navigation, the most important one is the conflict between the high sensitivity and wide measurement range. Then, two methods were discussed to solve that conflict which is a key problem in current superfluid gyroscope research. The first method is “flux-locking”, which is a technique used in superconducting dc-SQUIDs. The principle of the method and analysis of performance were presented. It can increase measurement range to 500 times of original one. In another hand, such a superfluid gyroscope should work in a situation with limited angular acceleration. Author presented another method, called “history tracing”, and its work principle. The performance of the second method also be studied, and results showed that “history tracing” overcomes the problem of measurement range totally. Comparisons showed that “history tracing” is a better choice to develop high performance superfluid gyroscope. View full abstract»

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  • Accurate real time inertial navigation device by application and processing of arrays of MEMS inertial sensors

    Publication Year: 2010 , Page(s): 20 - 26
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (743 KB) |  | HTML iconHTML  

    Two adaptively combined gyro and triaxial accelerometer arrays of commercial-grade Micro Electro-Mechanical Systems (MEMS) inertial sensors and a real-time embedded algorithm suite significantly enhance accuracy over that of single commercial-grade devices. Denoised sensor data is combined with a Kalman-filter bias compensation algorithm to achieve better than 0.1 degree/hour in-run gyro bias stability (standard deviation). One denoise-filtered triaxial accelerometer sensor array provides better than 30µg accelerometer bias stability. The hardware is embedded in an exoskeleton that maintains accurate fine alignment adjustments and provides protection when in rugged environments. Analysis of results measured from Allan variance computations of real-time data from several different IMU hardware units demonstrates that each of three orthogonally positioned precision gyro arrays, and their associated processing, achieve less than 0.03 deg integrated angle drift over 5 hours. New IMU hardware is now in fabrication for delivery in early 2010, when received, we expect to overcome the limits of the present hardware design to produce additional significant improvements. The size, weight, and power of these new IMU's are suitable for man-portable, hand-held systems, UAVs, and munitions systems. Early work for this technology was first published at ION/PLANS 2008. View full abstract»

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  • Navigation in vehicle crash test using MEMS-based IMU

    Publication Year: 2010 , Page(s): 27 - 31
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (657 KB) |  | HTML iconHTML  

    Results from our experiments on inertial navigation in crash testing of vehicles are presented. A custom designed inertial measurement unit (IMU) has been developed, and several tests in dummy calibration rigs including full-scale Euro NCAP collisions have been performed at our partners' crash test laboratories. For reference, the IMU data is compared to camera data and traditional single-axis inertial sensors. View full abstract»

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  • High performance inertial navigation grade sigma-delta MEMS accelerometer

    Publication Year: 2010 , Page(s): 32 - 36
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1517 KB) |  | HTML iconHTML  

    Traditional inertial grade accelerometers, based on vibrating quartz structures, which have excellent dynamic range, are vital components in avionics. However, such kinds of accelerometers suffer from high cost and exhibit post-shock stability degradation in particular high-shock, high-vibration environments. MEMS fabrication process is an inherently rugged technology and has great potential to bring forth novel solutions on the harsh environment and safety critical applications. This paper reports on a very high performance closed-loop MEMS accelerometer targeted at inertial navigation applications. The chasing primary goal is not for the lower costs and small size, but the performance; the MEMS accelerometer's specifications compete with very high performance accelerometers. The demonstrated MEMS accelerometer is a bulk manufactured capacitive sensor with 11g input full scale over a 300 Hz bandwidth, which is controlled by highly optimized closed-loop electronics. The one-bit sigma-delta 5th-order regulation loop leads to dramatic linearity improvement and consequently vibration rectification factor (VRE). The major improvement in bias stability comes from MEMS design and process flow. Measurements show a long-term bias stability of ±0.1mg, a VRE of better than 10µg/g2, an in-band noise floor of 1µg/vHz and a 120dB dynamic range in a 100 Hz bandwidth. Additional attraction is the low power consumption of the MEMS accelerometers, which makes the power consumption critical applications feasible in the future unmanned air vehicles (UAV). View full abstract»

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  • Evaluating the performance of low cost MEMS inertial sensors for seamless indoor/outdoor navigation

    Publication Year: 2010 , Page(s): 157 - 167
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4166 KB) |  | HTML iconHTML  

    For all mobile, location based applications, location availability (either on demand or continuously) is the primary performance requirement of the positioning technologies used. In most cases, this requirement outweighs that of meeting a specified accuracy, as the granularity of information provided to the user can be scaled around the computed positioning accuracy. What is therefore important is being able to generate a position solution and its accuracy at a specified level of confidence. For these applications, meeting the requirement of 100% availability is a significant challenge for individual positioning technologies, even more so when navigating between indoor and outdoor environments. Whilst operating under ideal operating conditions, GPS provides excellent positioning coverage. In indoor environments, position solutions can be generated using infrastructure based technologies such as RFiD and WiFi or augmentation sensors such as inertial navigation systems. Micro- Electromechanical Sensor (MEMS) inertial sensors are a popular option as they offer an autonomous capability that can potentially augment performance seamlessly across indoor and outdoor environments with marginal cost implications. This paper presents the results of a practical test undertaken to evaluate the performance of commercially available MEMS inertial sensors. In particular, results obtained that characterize the performance of these sensors against GPS in the transition zone between indoor and outdoor environments will be presented. View full abstract»

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  • Development of a MEMS gyroscope for northfinding applications

    Publication Year: 2010 , Page(s): 168 - 170
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    We report progress toward a MEMS gyroscope suitable for northfinding in pointing and targeting applications. In-run bias stability of 0.03 deg/hr and ARW of 0.002 deg/rt(hr) have been achieved. Gyro performance was measured on tuning-fork type MEMS gyroscopes using DSP-based breadboard electronics. These bias stability and ARW results are within about 6X and 2X, respectively, of meeting the typical gyrocompass requirements for pointing and targeting applications (1 milliradian azimuth precision at 65 degrees latitude with 5 minute integration time). A MEMS gyrocompass meeting these requirements would substantially reduce the size, weight and power of pointing and targeting instruments. The test methodology will be presented, as well as test data on carouseling the sensor to reduce the effects of long-term bias drift. View full abstract»

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  • Vibratory gyro skewed pick-off and driver geometry

    Publication Year: 2010 , Page(s): 171 - 179
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB) |  | HTML iconHTML  

    This report is based on recent patent applications by Watson Industries, which are available to the industry through licensing. Essentially, Watson Industries has developed several novel new means of applying and extracting signals for vibratory gyros. The method involves using a slight skew in alignment for pickoffs and/or drivers to control the drive and sensing vectors to electrically optimize gyro performance. The main example presented is based on the ceramic cup vibrating structure gyro, but these same principles may apply to almost all other vibrating structure gyro mechanisms. View full abstract»

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  • Low-cost, compact Fiber-Optic Gyroscope for super-stable Line-of-Sight stabilization

    Publication Year: 2010 , Page(s): 180 - 186
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (734 KB) |  | HTML iconHTML  

    This paper presents a new Interferometric Fiber Optic Gyroscope (IFOG) optimized for Line of Sight (LoS) stabilization being developed by IFOS and its prime subcontractors InFiber Technology and Optiphase under sponsorship of AFRL as a Phase II SBIR program. To date IFOS designed, built and tested five prototypes. Four gyros were delivered to Lockheed Martin (LM) for further testing. View full abstract»

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  • Performances comparison of different MEMS-based IMUs

    Publication Year: 2010 , Page(s): 187 - 201
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1992 KB) |  | HTML iconHTML  

    MEMS inertial sensors are widely used for navigation applications where size, weight, power and cost are key sides, such as autonomous vehicular control and pedestrian navigation. Otherwise, if there is no doubt that MEMS technologies represents an interesting turning point for low cost inertial-based sensors and applications, nevertheless it is absolutely true that, in order to obtain good positioning accuracies, it is necessary to investigate very well the behaviour of these MEMS sensors and realize special test calibrations, both in static and kinematic conditions. In order to evaluate the potentialities (and the limits) of these sensors, comparative tests have been realized considering MEMS inertial sensors with different characteristics and different performances, First of all, a static calibration of the sensors has been made, in order to compare the bias values and their stability with respect to the time. In particular, an Allan-variance analysis and a modified six position static test were carried out for each sensor, preserving carefully the same environment conditions for all the tests. After the lab tests, the performances of all the sensors were compared in a field kinematic test, integrating their data with a GPS solution. View full abstract»

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  • Evaluation of a double equipped MEMS IMU based on real flight trial scenarios

    Publication Year: 2010 , Page(s): 202 - 213
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1771 KB) |  | HTML iconHTML  

    The Inertial Measurement Unit (IMU) investigated within the presented work consists of two (optional three) dissimilar sets of MEMS accelerometers and gyros, respectively. Both sets are mounted in one enclosure and thus are subject to the same calibration procedure. Different combinations of these dual sensor sets can be used to exploit the complementary sensor properties, e.g. measurement range, resolution and noise characteristics as well as to benefit from redundancy in airborne applications. View full abstract»

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  • MEMS based AHRS with adaptive bias estimation for high performance rate sensor replacement

    Publication Year: 2010 , Page(s): 214 - 220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (893 KB) |  | HTML iconHTML  

    Presented is the unique retrofit application of a MEMS based Attitude Heading Reference System (AHRS) into an existing high performance pan and tilt surveillance platform. The platform imaging sensors must provide stable imagery from fixed and moving locations, rejecting external rate disturbances. The quaternion based attitude estimator provides gyro bias estimates that are removed before output to the pan and tilt control system. The sensor replacement unit outputs analog voltages corrected for temperature and other environmental conditions to provide a drop in replacement capability costing an order of magnitude less. View full abstract»

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  • Analysis of deeply integrated and tightly coupled architectures

    Publication Year: 2010 , Page(s): 382 - 396
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB) |  | HTML iconHTML  

    This paper analyzes the impact that architectural features have on the performance of deeply integrated and tightly coupled algorithms. The effects of two specific architectural features are investigated. The first is the design of the Kalman filter used in the algorithms. The performance degradation caused by using a federated filtering architecture instead of a single, centralized filter is analyzed. The second feature is the usage of scalar and vector tracking loops. The advantage offered by vector tracking loops over scalar tracking loops is quantified. The effects of these two architectural features are determined by analyzing the comparative performance of three different algorithms. One algorithm uses a single Kalman filter to process the GPS signals and the inertial sensor data. The other two algorithms use a federated filtering architecture. One federated algorithm uses scalar tracking loops and the other uses vector tracking loops. Comparing the performance of the three algorithms allows the effects of filter design and tracking loop operation to be isolated. Covariance analysis and Monte Carlo simulations are used to study the performance of the algorithms with different inertial sensor grades and satellite constellations. The analysis reveals that the federated algorithm with vector tracking and the centralized filtering algorithm perform virtually identically. The federated algorithm with scalar tracking loops performs poorer. However, the performance of all three algorithms converge as the carrier to noise power density ratio declines. At low signal powers, all three algorithms provide identical performance. The results quantify how the architectural features of coupled systems affect their performance. View full abstract»

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  • Tightly coupled GPS/INS integration for differential carrier phase navigation systems using decentralized estimation

    Publication Year: 2010 , Page(s): 397 - 409
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1074 KB) |  | HTML iconHTML  

    Much research has been conducted in the area of tightly coupled GPS/INS, and this work has resulted in a vast array of navigation algorithms. A common theme of these methods is that they operate on low rate GPS ranging measurements of code and carrier phase together with high rate raw inertial measurements, such as specific force and inertial angular velocity. For stand-alone (i.e., non-differential) GPS navigation applications, high data rate INS outputs can be properly accommodated with today's computer processors. For relative (i.e., differential) GPS navigation applications, the optimal analogous solution would be for the mobile user to have access to the reference station's raw inertial measurements along with its own. However, due to communication bandwidth limitations, it is generally not possible to broadcast high data rate inertial navigation data. In response, an alternative tightly-coupled, differential GPS/INS navigation system is developed here using a decentralized Kalman filtering approach, which can operate at manageable broadcast data rates. View full abstract»

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  • An alternative erection procedure for on-ground transfer alignment

    Publication Year: 2010 , Page(s): 410 - 417
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (547 KB) |  | HTML iconHTML  

    This paper presents a procedure for computing the relative orientation between two static inertial navigation systems: a primary and a secondary. The primary system is assumed to be of navigation quality and therefore capable of gyro-compassing to the desired accuracy. The secondary is lower quality and requires external aiding for azimuth and accurate leveling initialization. The assumption that allows the transfer alignment is that the primary and the secondary are rigidly mounted on a mechanical structure that allows for joint rotation around one or more axis while maintaining the relative orientation between the two systems. A pitch axis is typical in practical systems and hence the name “Erection Procedure.” As opposed to the Kalman-filter based procedures in use in several systems today, the new method does not require the computation of a navigation solution while the mechanical system is been erected. Instead, measurements from the navigation sensors are required at a number of discrete stages, and then these measurements are processed to compute the relative orientation between the primary and the secondary. The procedure is easy to implement and yields an exact solution to the problem whenever the underlying assumptions are exactly met. It has been shown to work well both in simulations and in practice. In addition to its practical relevance, this work also sheds additional light into the general question of aligning two static navigation systems. View full abstract»

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  • A self-resetting method for reducing error accumulation in INS-based tracking

    Publication Year: 2010 , Page(s): 418 - 427
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (825 KB) |  | HTML iconHTML  

    The error accumulation in the INS systems is one of the major drawbacks which limits their applicability. Several efforts have been made to improve the performance of the INS systems in the tracking applications with limited success in terms of efficiency, complexity and cost. This paper proposes a new method for modelling the actual INS error accumulation and use of automatic self-resetting for reducing error accumulation within the INS system without the need of any external sensors or devices. The new method has been verified and tested for the case of a single-axis accelerometer. Furthermore, the method has been used to recover the trajectory of moving objects in outdoor environments when a full INS system is used. The testing results show that the new method considerably reduces the error accumulation in the INS systems. Moreover, the new method increases the operation time of the INS-based systems from few second to a few minutes. View full abstract»

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  • Error modeling and characterization of environmental effects for low cost inertial MEMS units

    Publication Year: 2010 , Page(s): 598 - 612
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (810 KB) |  | HTML iconHTML  

    The accurate modeling of MEMS based inertial sensor errors is one of the most challenging tasks in the design of low cost navigation systems. Although the design process of inertial navigation systems mainly depends on the sensor model parameters, a standard procedure for error characterization has yet to be developed. In the first part of this study we present a new method of stability error modeling for MEMS based multi-IMU systems. The developed method uses correlation of low pass filtered sensor outputs to derive sensor error models. In the second part the effects of i) temperature ii) time and iii) G and vibration on MEMS units' outputs are analyzed using a series of laboratory test results. A method compensating for the effect of temperature variation and modeling for residual compensation error is also explained. Better sensor models obtained with the methods presented in this paper will lead to more robust navigation systems with low cost MEMS units. View full abstract»

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  • Inertial instrument error identification algorithm based on reverse navigation data

    Publication Year: 2010 , Page(s): 613 - 616
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (797 KB)  

    Accurate positioning and attitude information is very important for remote sensing, the key point of Virtual Test is researched in the paper to obtain accurate model of the actual system. In order to identify the actual inertial navigation system error model from flight data, a new identification method was proposed. Through the reverse process of strapdown inertial navigation, the ideal inertial instrument output data could be solved from navigation result. The error compensation system can be established, with ideal data input and the actual data of the inertial instrument output. Finally, the error model and error coefficient of inertial instrument were obtained with the system identification method. The test results show that the method is effective and has reference value and directing significance for engineering application. View full abstract»

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  • Towards volume medium-accuracy MEMS gyro manufacturing: Challenges and solutions

    Publication Year: 2010 , Page(s): 617 - 620
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2136 KB) |  | HTML iconHTML  

    Stepping up from a working prototype to a volume production with adequate yield is a challenge for every type of MEMS hardware. That especially applies to precise inertial sensors, among which gyros have always been of special attention. This paper provides an overview of development of medium accuracy MEMS gyro and associated steps that led to a running manufacturing facility with current production capacity of thousands of MEMS tri-axial systems a year. The core technology behind all of our IMUs and gyrometers is a multi-layer silicon gyrochip - a 3D structure assembled using WLP (wafer level packaging) technology with a deeply vacuumed cavity inside that contains a vibrating structure. Reliable and proven silicon wafer anodic bonding process guarantees long lasting vacuum without use of inner getters - numbers for vacuum reliability inside the gyrochip through indirect Q-factor measurements over time are given. An all silicon structure also provides significantly better temperature linearity compared to common SOI (silicon on insulator) gyro assemblies. The top silicon layer contains feed throughs for gyro excitation and pick-off that are manufactured using novel TSI (through silicon insulator) technology. The gyrochip dimensions are 12.6×4.6×1 mm and 3 gyrochips are packaged into a 3-axis gyrometer via glass substrate with overall volume of the sensor module just below 4 in3. Statistics for angular rate performance show in-run bias stability better than 10 deg/hour, angular random walk below 0.1 deg/sqrt(h) and quite good bias repeatability. The paper talks about problems that were successfully solved in short-loop and pilot gyrochip manufacturing, such as selection of proper type of VIA trenches and each wafer thickness to minimize parasitic capacitances, reliable bonding of thin silicon wafers, testing of dies (for single sliced dies and automated wafer level testing equipment). For the 3-axis - - system manufacturing, issues of silicon gyrochips mounting through glass substrates, overall vibration and thermal analysis and shock reliable design are discussed. Examples of performance are also given. Currently, the overall production yield of the gyrochips at the MEMS foundry is close to 50%, and the yield from a successful batch is close to 70%. The yield from the 3-axis system (IMU or gyrometer) manufacturing line is close to 80%. Those numbers are still increasing and have potential to get to 90's digits in one year. View full abstract»

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  • Calibration enhancement of ShapeAccelArray technology for long term deformation monitoring applications

    Publication Year: 2010 , Page(s): 621 - 626
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (603 KB) |  | HTML iconHTML  

    ShapeAccelArray (SAA) provides precise 3D position along a continuum using hundreds of low cost MEMS sensors. The technology has been applied to long term soil monitoring applications, where long-term accuracies in the 50 part-per-million (ppm) range have been achieved. Industrial demand for the technology in structural monitoring applications where 10 ppm would be desirable has magnified the importance of modelling and compensating for temperature sensitivities of each sensor. In such applications, dramatic temperature changes are possible, unlike the relatively stable, sub surface environment. View full abstract»

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  • Analysis of sculling motion errors caused by sensor transfer function imperfections in strapdown inertial navigation systems

    Publication Year: 2010 , Page(s): 627 - 631
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (347 KB) |  | HTML iconHTML  

    Sculling compensation algorithms implemented in strapdown inertial navigation systems are designed to treat low frequency acceleration signals originated from a simultaneous linear and angular high frequency vibration through the strapdown navigation equations nonlinearity. However, if the inertial sensor transfer functions are imperfect, the low frequency terms might not be completely compensated, thus causing an effective bias in the accelerometer output. In the present work a quantitative analysis of the uncompensated sculling errors caused by the sensor transfer function imperfections is carried out in the case of the pure sculling motion. The obtained results can be used to facilitate the selection of the appropriate inertial sensors to meet the prescribed navigation accuracy requirements. The presented analysis is especially important if low cost (e.g., MEMS) sensors are considered for implementation in strapdown INS. View full abstract»

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  • Observability of integrated navigation system states under varying dynamic conditions and aiding techniques

    Publication Year: 2010 , Page(s): 632 - 638
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (923 KB) |  | HTML iconHTML  

    The performance of integrated navigation systems not only depends on the quality of the used inertial measurement unit (IMU) and aiding sensor information, but also on the correct observation of the system's state vector. As a classical example, an integration filter shows a good performance if it manages to estimate the sensor errors properly. As the observability varies with the current system states as well as the quality of the aiding information, a meaningful characterization of the system's performance is difficult to obtain. The aim of this paper is to analyze the impact of the influences named above on the observability of the system model that is part of the navigation filter. For linear and linearized systems, e.g. Kalman Filter and Extended Kalman Filter, different measures of observability can be derived from control theory. This paper will show the necessary basic algorithms and methods to evaluate a system's observability. Based on these insights an evaluation of a standard filter model of an integrated navigation system is performed. Therefore, different dynamic conditions as well as aiding information are taken into account. The main focus of this work lies on the examination of real flight data and correlation between system states and their observability. Based on these investigations this paper presents a detailed view on the assessment and first results towards a better characterization of IMU performance. View full abstract»

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  • Development of a low cost sun sensor using quadphotodiode

    Publication Year: 2010 , Page(s): 639 - 644
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1164 KB) |  | HTML iconHTML  

    This paper describes about the design and hardware implementation of a low cost model of a two axis sun sensor using a quad photo diode, which can determine the azimuth and elevation angles of Sun in sensor's body frame of reference. The sensor uses quad photodiode to obtain angular information of Sun. It weighs less than 100g (which can be further reduced by optimizing the housing design). The relevant software requires 50K bytes of memory and little processing. We have also developed sensor calibration test bed (SCTB) which will also be the part of this paper. SCTB is used to calibrate the developed Sun Senor; during calibration the whole surface of sun sensor (quad photodiode) is scanned for a field of view (FOV) equal to 60 × 60. Step size during calibration is set to one degree so we get elevation and azimuth matrices each having 3721 values. The calibration process is fully automated with the help of algorithms written in Matlab. The step size used in calibration is adjustable and we can calibrate the sensor even less than one degree using this SCTB. Azimuth and elevation matrices generated during calibration are used as error correcting tables during real-time measurements taken by the sun sensor. Sun sensor is calibrated in front of Sun simulator made by the Optical Energy Technologies USA. View full abstract»

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  • Sensitivity analysis of object space geometry for TLS-aided navigation

    Publication Year: 2010 , Page(s): 850 - 857
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (699 KB) |  | HTML iconHTML  

    In GPS-impeded environments, due to cumulative error characteristics of inertial sensors, a GPS/IMU system is unable to maintain high navigation accuracy during extended GPS outages. In particular, vegetated and urban environments present unique challenges in applications where high absolute and/or relative navigation accuracy is required. To remedy this deficiency, a method that integrates 3D laser ranging to deployable spherical targets with an inertial system to enable centimeter-level navigation accuracy of a mobile unit under heavy canopy is discussed here. This paper is focused on the requirements for geometry and spatial distribution of the spherical targets and their impact on the achievable navigation accuracy. The sensitivity analysis is performed based on simulations as well as the actual field test data. View full abstract»

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