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The NOAA G-IV aircraft routinely measures vertical aircraft acceleration from the inertial navigation system at 1 Hz. The data provide a measure of turbulence on a 250-m horizontal scale over a layer from 12.8- to 14.8-km elevation. Turbulence in this layer of tropical cyclones was largest by 35%–40% in the inner 200 km of radius and decreased monotonically outward to the 1000-km radius. Turbulence in major hurricanes exceeded that in weaker tropical cyclones. Turbulence data points were divided among three regions of the tropical cyclone: cirrus canopy; outside the cirrus canopy; and a transition zone between them. Without exception, turbulence was greater within the canopy and weaker outside the canopy. Nighttime turbulence exceeded daytime turbulence for all radii, especially within the cirrus canopy, implicating radiative forcing as a factor in turbulence generation. A case study of widespread turbulence in Hurricane Ivan (2004) showed that interactions between the hurricane outflow channel and westerlies to the north created a region of absolute vorticity of −6 × 10−5 s−1 in the upper troposphere. Outflow accelerated from the storm center into this inertially unstable region, and visible evidence for turbulence and transverse bands of cirrus appeared radially inward of the inertially unstable region. It is argued that both cloud-radiative forcing and the development of inertial instability within a narrow outflow layer were responsible for the turbulence. In contrast, a second case study (Isabel 2003) displayed strong near-core turbulence in the presence of large positive absolute vorticity and no local inertial instability. Peak turbulence occurred 100 km downwind of the eyewall convection. [ABSTRACT FROM AUTHOR]

Abstract Position and Orientation System (POS) is the key sensor of remote-sensing system. It is a typically Strapdown Inertial Navigation System (SINS) and Global Navigation Satellite System (GNSS) integrated measurement system, which provides high-precision position and attitude parameters. The gravity disturbance vector is one of the main error sources of high-precision SINS. The error propagation of POS is analyzed. It shows that the vertical component of the gravity disturbance vector is introduced into the POS horizontal channel through the vertical deflections, which leads to the error of the attitude measurement of the POS. In this article, a new real-time gravity compensation method is proposed, which includes the gravity disturbance as the error states of POS Kalman filter, and the accurate gravity disturbance model is constructed by a "Block-Time Variation" Markov Model (B-TV-MM) based on high-precision gravity map, whose resolution is enhanced by a new interpolation method based on Gaussian Process Regression (GPR). A flight experiment was conducted to evaluate the efficiency of the proposed method and the results showed that the proposed method performs better compared with other real-time gravity compensation methods. [ABSTRACT FROM AUTHOR]

Abstract The performance of an attitude control system is impacted by the inertia change, especially for small satellites. Although there are various control methods for satellites with inertia uncertainties, very few controllers are designed with consideration of time-varying inertia. In this paper, a linear parameter varying (LPV) model is established for a satellite with time-varying inertia. Moreover, because of their common occurrences, the actuator faults and saturation are considered during the controller design. A gain-scheduled controller is developed to guarantee the steady-state and transient performance of the system by limiting the steady-state variance and regional pole constraints. The simulations indicate that the proposed controller improves the stability performance by adjusting the gain with the inertia variations. [ABSTRACT FROM AUTHOR]

By analyzing the error models of the measured vectors of the gravitational apparent motion, an in-motion filter-QUEST alignment method only with the inertial measurement unit is presented in this paper. The contribution of the proposed method lies in constructing the in-motion model of the measured vectors of the gravitational apparent motion and developing the extracted method to reconstruct the measured vectors. Furthermore, the relationship between the noise characteristic and the moving state of the vehicle is analyzed in detail. Different from the several current techniques, the presented method can be carried out without any other external additional equipment, when the vehicle is in-motion. With the designed real-time wavelet denoising (RWD) method, the high-frequency noises of the measured vectors are filtered. Based on the constructed parameter recognition model of the measured vectors, a robust adaptive Kalman filter is devised to estimate the optimal parameters, which are used to calculate the reconstructed observation vectors. Moreover, the gross outliers, which are contained in the filtered vectors of the RWD, are eliminated effectively. The simulation and the field trial results demonstrate that the presented method is applicable to the in-motion initial alignment, and it can serve as a nice initial alignment method in the follow-on fine alignment process and navigation process. [ABSTRACT FROM AUTHOR]

This study presents the navigation system of an inboard spacecraft (IS) of the Tiangong space station. This system comprises a multiple field-of-view vision system (MFVS) and a micro inertial measurement unit (MIMU). The MFVS utilizes three mutually orthogonal cameras and takes sparse and identical vision beacons as navigation references. A practical model for the MFVS is proposed based on a pseudo-measurement, which refers to the beacon coordinates in the camera frames. On this basis, three sub-algorithms for image processing and measurement equation forming are designed. Accelerated feature extracting and matching, dilution of precision analysis-based vision beacon selection strategy, and MIMU-aided image smearing elimination are analyzed. An extended Kalman filter is utilized to couple the MFVS and MIMU tightly. The 6-degree-of-freedom pose of the system and the vision beacon coordinates are estimated. The proposed algorithm is verified through a navigation experiment. Results inside a simulated cabin area of 1.5 m 3 are obtained. The attitude and position accuracy in each axis reach within 0.04° and 0.41 mm (1 σ ), respectively. The proposed algorithm meets the requirement of the IS navigation and has potential application in other similar conditions. [ABSTRACT FROM AUTHOR]

Currently the matrix vibration of the strapdown inertial navigation system (SINS) for some cruise missile needs to be reduced and conventional algorithms occupy excessive hardware resources. Considering the vibration frequency range from 50 to 400HZ has the biggest impact on the guidance accuracy, we propose a target method for active vibration control in the SINS. Firstly, the requirement analysis is carried out for the target method, and secondly the MATLAB software is used to design the parameters and compare the filtering simulation. Then the hardware design is performed and the filtering algorithm is improved to reduce the power consumption approaching green computing. Finally the effectiveness and cost-efficiency of the target method for active vibration control in the SINS is verified by the experiment. The results show that the target method can separate the main vibration frequency which affects the guidance accuracy with a good linearity effect, efficient hardware utilization and low power consumption approaching green computing. Moreover, the accuracy, the effectiveness and efficiency of the control algorithm have been also significantly improved. [ABSTRACT FROM AUTHOR]

The effects of sand and dust ingestion often limit the useful life of turbine engines operating in austere environments, and efforts are needed to reduce the quantity of particulates entering the engine. Inertial particle separators offer significant weight savings and are more compact, but do not yet provide separation efficiencies as high as that from historical filter and vortex tube separator technologies. To further improve the separation efficiency of integral particle separators, a wind tunnel was designed, constructed, and tested to study the multiphase flow dynamics of an inertial particle separator. The experimental facility includes a rectangular test section ideal for optical access and is capable of reproducing full-scale flow and particle conditions seen in separator systems. A testing methodology is specified that measures mass flow rates and overall sand separation efficiency, as well as surface flow visualization of the separator region. Results indicate that inflow characteristics are important to maintain predominately two-dimensional flow, though interesting end-wall effects are also present. The particle separation efficiency results indicate high performance (over 90% by mass) relative to previous values reported in the literature as well as quantitative dependence on scavenge split. [ABSTRACT FROM AUTHOR]

The flight mechanics, stability, and control of a helicopter undergoing rotor span morphing is examined. A span-morphing variant of the UH-60A Black Hawk helicopter at 18,300 lb gross weight is developed. A model-following dynamic inversion controller is implemented, and radius change is introduced as an additional feed-forward component into the control laws, with the aircraft model being updated with respect to flight condition. The flapping and inflow modes of the rotor exhibit significant movement as span changes, but relatively little movement is observed in the rigid-body modes. Closed-loop poles associated with the low-frequency aircraft modes are observed to be robust to change in rotor span, eliminating the need for model updates during the morphing process. The error compensators in the control laws use proportional-integral- derivative control for roll and pitch attitude and proportional-integral (PI) control for lateral and longitudinal ground speed, but require proportional-double integral compensator control for vertical speed and yaw rate to avoid altitude loss and heading drift observed with only PI control, during span morphing. Detailed simulations results are presented for 40 kt cruise, and velocities of 80 and 120 kt are also considered. From a baseline rotor radius of 26.8 ft, retraction to 22.8 ft, as well as extension to 31.5 ft, is considered, nominally over a 60-s duration. The controller is observed to regulate the aircraft operating state well over the nominal duration and is still effective when duration is reduced to 30 s. [ABSTRACT FROM AUTHOR]

The Indian Regional Navigation Satellite System (IRNSS) has recently (as of May 2016) become operational. The system has been developed with the objective of offering positioning, navigation, and timing (PNT) to users in its two service areas, covering the Indian landmass and the Indian Ocean, respectively. It is the goal of this contribution to provide further insight into the full-constellation L5 pseudorange single-point positioning (SPP) capabilities of the system. A detailed dilution of precision (DOP) analysis of its two service areas, including the identification, in location and time, of poor receiver-satellite geometries is provided. It is hereby demonstrated how the impact of some of these poor receiver-satellite geometries can be mitigated by means of height-constraining. An overview and analysis of the SPP precision is also provided including easy-to-use representative day-averaged values for a grid of locations covering the two service areas. [ABSTRACT FROM AUTHOR]

Reconstruction of dynamical parameters is one of the main challenges faced in the on-orbit servicing missions for defunct spacecraft. And the quaternion plays a major role in parameterizations of the dynamical model. In this paper, the analytical solution of the quaternion differential equations of a tumbling symmetrical object is derived. Given this solution, a constant state filter is proposed for inertial characteristics estimation and attitude prediction of tumbling spacecraft. The key idea of the present filter is to replace dynamic variables by the undetermined constant parameters of the analytical solution. These parameters are estimated during the filtering process and then used to calculate the dynamic variables of the spacecraft. Furthermore, they are also utilized to determine the inertial characteristics and predict the future attitude motions. Compared with traditional EKFs, the constant state filter shows good performance when the measurement sampling interval is large or a priori estimation of the state is unavailable, because the dynamic model and observation model are transformed into approximate linear forms by utilizing the constant state vector. Numerical simulations verify the convergence and precision of the proposed filter. [ABSTRACT FROM AUTHOR]

The error of a MEMS gyroscope is highly dependent on the ambient temperature. Traditionally, it is modeled with polynomials, which cannot achieve sufficient accuracy. In order to solve this problem, a Parameter-Interpolation method is proposed to model and calibrate the deterministic error of a MEMS gyroscope. First, the establishment of a MEMS gyroscope's error model and the calibration methods are discussed. Based on the traditional method, we come up with the Parameter-Interpolation (PI) model. Its parameters vary with temperature and each group of parameters is saved separately. The gyroscope is calibrated through interpolation. Then, we design a multi-position experiment test using a thermal turntable to test the traditional and the Parameter-Interpolation (PI) methods. Finally, we process the data collected in the experiments and compare the results of these two methods. Results show that both methods are valid to improve the accuracy of a MEMS gyroscope but the Parameter-Interpolation (PI) method is more effective. [ABSTRACT FROM AUTHOR]

In-motion alignment of a strapdown inertial navigation system, during slow maneuvers, is studied. Terrestrial velocity is fed back to the navigation system to estimate and compensate for the navigation errors. Observability of the errors is analyzed since the integrated navigation system is not fully observable. Then, the accuracy bounds of the navigation system in different motion scenarios are obtained analytically. Also, in order to minimize the errors of the navigation system, special maneuvers are designed based on the analytical derivations. The analytical results, obtained using the linearized error model, are verified through nonlinear simulation of different maneuvering and non-maneuvering scenarios. It is shown that the proposed analytical method can be used to predict the errors of the navigation system with a high level of accuracy. Copyright © 2017 Institute of Navigation [ABSTRACT FROM AUTHOR]

Purpose: The paper deals with the mathematical description of the gimballed attitude and heading reference systems, which can be applied in design of strategic precision navigation systems. The main goal is to created mathematical description taking into consideration the necessity to use different navigations operating modes of this class of navigation systems. To provide the high accuracy the indirect control is used when the position of the gimballed platform is controlled by signals of gyroscopic devices, which are corrected using accelerometer’s signals. Methods: To solve the given problem the methods of the classical theoretical mechanics, gyro theory, and inertial navigation are used. Results: The full mathematical model of the gimballed attitude and heading reference system is derived including descriptions of different operating modes. The mathematical models of the system Expressions for control and correction moments in the different modes are represented. The simulation results are given. Conclusions: The represented results prove efficiency of the proposed models. Developed mathematical models can be useful for design of navigation systems of the wide class of moving vehicles. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost localization system to guide an Unmanned Aerial Vehicle (UAV) in indoor flights, considering an environment with invariant texture and typical indoor illumination. The first contribution of the paper is the proposal of a system to estimate the position and orientation of the UAV, through a multi-sensor fusion scheme, dealing with data provided by a RGB-D sensor, an inertial measurement unit (IMU), an ultrasonic sensor and optical flow-based velocity estimates. A second contribution of the paper is the proposal of a high-level control system to guide the UAV in path-following tasks, involving two controllers: a kinematic one, responsible for generating reference velocities for the vehicle, and a PD one, responsible for tracking such reference velocities, thus characterizing a cascade controller. Experiments with such a localization and control systems, during which abrupt disturbances are applied, were carried out to check the effectiveness of the developed capture and control systems, whose results validate the proposed framework. [ABSTRACT FROM AUTHOR]

The British Antarctic Survey regularly conducts airborne surveys with Twin Otter aircraft equipped with a variety of instruments. Each instrument captures its specific navigation requirements in a dedicated cockpit display that is unique and incompatible with that of other instruments. This creates unwanted logistical problems and training requirements, and necessitates extra air safety certification. In this paper we describe a new avionics display that is sufficiently flexible to capture the requirements of all of our instruments, as well as all of the preferences of our pilots. This Airborne Survey Navigation Device (ASCEND) dynamically routes aircraft within the constraints of the survey and features flexible and intuitive planning and navigation interfaces. ASCEND has been tested and compared to the instrument specific displays and is preferred, both for its ease of use and also for the effective accuracy of the pilot following a survey line. [ABSTRACT FROM AUTHOR]

To ensure the high accuracy, independence, and reliability of the measurement system in the unmanned aerial vehicle (UAV) landing process, an integration method of inertial navigation system (INS) and the three-beam Lidar is proposed. The three beams of Lidar are, respectively, regarded as an independent sensor to integrate with INS according to the conception of multisensor fusion. Simultaneously, the fault-detection and reconstruction method is adopted to enhance the reliability and fault resistance. First the integration method is described. Then the strapdown inertial navigation system (SINS) error model is introduced and the measurement model of SINS/Lidar integrated navigation is deduced under Lidar reference coordinate. The fault-detection and reconstruction method is introduced. Finally, numerical simulation and vehicle test are carried out to demonstrate the validity and utility of the proposed method. The results indicate that the integration can obtain high precision navigation information and the system can effectively distinguish the faults and accomplish the reconstruction to guarantee the normal navigation when one or two beams of the Lidar malfunction. [ABSTRACT FROM AUTHOR]

This paper studies three schemes of Mars entry navigation: inertial measurement unit (IMU) based dead reckoning (DR), IMU/orbiter based integrated navigation, and IMU/orbiter/Mars surface beacon (MSB) based integrated navigation. We demonstrate through simulations that first scheme, IMU based DR, produces substantially large state estimation errors. Although these errors are reduced by adding two Mars orbiters, the system is only barely observable. However, by adding two MSBs in above configuration, the position and velocity estimation errors are reduced to the scope of 10 m and 0.5 m/s respectively and the navigation system becomes completely observable. Finally, the estimability of states is investigated; it is observed that velocity variables or velocity variables linear combinations can be estimated better than position variables. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve the efficiency and accuracy of soft-landing dynamic calculation of lunar lander, this paper proposed a new soft-landing dynamic model with seven free degrees and the inertia force was also taken into consideration during the landing process. The force condition of lander during soft-landing was investigated; moreover dynamics and kinematics equations were deduced. Besides, the landing process was studied by mathematical model, which is verified by results of scale lander prototype and landing test platform. The result shows that the calculation could match the test results effectively, which verifies accuracy and availability of seven free degrees soft-landing dynamic model. [Copyright &y& Elsevier]

Although accelerometers are extensively used for assessing gait, limited research has evaluated the concurrent validity of these devices on less predictable walking surfaces or the comparability of different methods used for gravitational acceleration compensation. This study evaluated the concurrent validity of trunk accelerations derived from a tri-axial inertial measurement unit while walking on firm, compliant and uneven surfaces and contrasted two methods used to remove gravitational accelerations; i) subtraction of the best linear fit from the data (detrending); and ii) use of orientation information (quaternions) from the inertial measurement unit. Twelve older and twelve younger adults walked at their preferred speed along firm, compliant and uneven walkways. Accelerations were evaluated for the thoracic spine (T12) using a tri-axial inertial measurement unit and an eleven-camera Vicon system. The findings demonstrated excellent agreement between accelerations derived from the inertial measurement unit and motion analysis system, including while walking on uneven surfaces that better approximate a real-world setting (all differences <0.16 m.s−2). Detrending produced slightly better agreement between the inertial measurement unit and Vicon system on firm surfaces (delta range: −0.05 to 0.06 vs. 0.00 to 0.14 m.s−2), whereas the quaternion method performed better when walking on compliant and uneven walkways (delta range: −0.16 to −0.02 vs. −0.07 to 0.07 m.s−2). The technique used to compensate for gravitational accelerations requires consideration in future research, particularly when walking on compliant and uneven surfaces. These findings demonstrate trunk accelerations can be accurately measured using a wireless inertial measurement unit and are appropriate for research that evaluates healthy populations in complex environments. [ABSTRACT FROM AUTHOR]

The problem of reconstructing the trajectory of an aircraft is considered. The reconstruction is based on heights measured in flight and on preliminary information about the underlying elevation field. A trajectory-reconstructing algorithm is described, and numerical results produced by it are presented. [ABSTRACT FROM AUTHOR]

Abstract: The Hypersonic Cruise Vehicles (HCVs) have an extremely high requirement for the navigation system to be high-reliable, high-autonomic and high-accurate. This paper proposed a method to calibrate the deterministic errors of the Inertial Measurement Unit (IMU) of the Inertial Navigation System (INS) dynamically. Including the installation errors and the scale factor errors of the IMU, an augmented error model of the IMU and the navigation parameter error propagation equations of INS are discussed first. Then a method based on the Kalman Filter is designed to calibrate deterministic errors of the IMU during the HCVʼs high dynamic flight process. The proposed method can accurately and dynamically calibrate the deterministic errors of the IMU. The calibration results are used to correct the IMU deterministic errors and the INS parameter errors dynamically. Simulation is made to verify the performance of the calibration method proposed by this paper. The simulation results show that the dynamic calibration method can effectively estimate the installation errors and the scale factor errors of the IMU; the precision of the INS is improved after the compensation of the installation errors and the scale factor errors that obtained by the calibration method. [Copyright &y& Elsevier]

China has developed an airborne gravimetry system based on SINS/DGPS named SGA-WZ, the first system in which a strapdown inertial navigation system (SINS) has been used for airborne gravimetry in China. This gravity measurement system consists of a strap-down inertial navigation system and a differential global positioning system (DGPS). In April 2010, a flight test was carried out in Shandong Province of China to test the accuracy of this system. The test was designed to assess the repeatability and accuracy of the system. Two repeated flights and six grid flights were made. The flying altitude was about 400 m. The average flying speed was about 60 m/s, which corresponds to a spatial resolution of 4.8 km when using 160-s cutoff low-pass filter. This paper describes the data processing of the system. The evaluation of the internal precision is based on repeated flights and differences in crossover points. Gravity results in this test from the repeated flight lines show that the repeatability of the repeat lines is 1.6 mGal with a spatial resolution of 4.8 km, and the internal precision of grid flight data is 3.2 mGal with a spatial resolution of 4.8 km. There are some systematic errors in the gravity results, which can be modeled using trigonometric function. After the systematic errors are compensated, the precision of grid flight data can be better than 1 mGal. [ABSTRACT FROM AUTHOR]

A review of the most significant technical papers related to the navigation of underwater remotely operated vehicles is presented, with special interest in aided inertial navigation. Sensors used for implementation, fusion algorithms and models that describe the navigation systems are presented. From this review, it was concluded that the implementation of an estimator, based on the vehicle kinematic and dynamic models, limits the growth of the estimated error, even in case that the only available information is that provided by an inertial measurement unit. [ABSTRACT FROM AUTHOR]

The traditional strapdown inertial navigation algorithm is to calculate the ground velocity based on integral of specific force transformation, which is solved using first-order approximation and second-order truncation. The influence of approximate integration errors on navigation precision cannot be ignored. In order to eliminate this influence, an improved strapdown inertial navigation algorithm with high precision is presented by using split integration scheme in the inertial reference frame. An analytical solution of the integrated transformed specific force increment is obtained for the thrust velocity defined by integral of specific force in the inertial frame, and a compensation scheme based on modified velocity increment is proposed for sculling error by analyzing its cause, an exact solution of the thrust velocity which can completely offset the dynamic errors, including coning error, rotation error and sculling error, is obtained. Both coning and sculling errors may be computed directly using the traditional optimization algorithms. A complete strapdown inertial navigation algorithm with high precision is developed by extending the thrust velocity update ideas into integration of the gravitational acceleration and position update. The significant advantages of the algorithm in the overall performance are demonstrated by the simulation test results under complex dynamic environment. [ABSTRACT FROM AUTHOR]

Besides offset biases (such as range, the gain of range, azimuth, and elevation biases), for mobile radars, platform attitude biases (such as yaw, pitch, and roll biases) induced by the accumulated errors of the Inertial Measurement Units (IMU) of the Inertial Navigation System (INS) can also influence radar measurements. Both kinds of biases are coupled. Based on the analyses of the coupling influences and the observability of 3-D radars’ error registration model, in the article, an Attitude Bias Conversion Model (ABCM) based on Square Root Unscented Kalman Filter (SRUKF) is proposed. ABCM can estimate 3-D radars’ absolute offset biases under the influences of platform attitude biases. It converts platform attitude biases into radar measurement errors, by which the target East-North-Up (ENU) coordinates can be obtained from radar measurements directly without using the rotation transformation, which was usually used in the transition from platform frame to ENU considering attitude biases. In addition, SRUKF can avoid the inaccurate estimations caused by linearization, and it can weaken the adverse influences of the poor attitude bias estimation results in the application of ABCM. Theoretical derivations and simulation results show that 1) ABCM-SRUKF can improve elevation bias estimate accuracy to about 0·8 degree in the mean square error sense; 2) linearization is not the main reason for poor estimation of attitude biases; and 3) unobservability is the main reason. [ABSTRACT FROM PUBLISHER]

Inertial navigation systems (INS) are widely used for controlling piloted or unmanned aerial vehicles (UAV). Automatic control equipment with INS has error budget making a huge impact on the accuracy of UAV navigation. The paper analyzes INS errors and types of errors. Experiments have been done using small UAV. [ABSTRACT FROM AUTHOR]

The Military Survey Department (MSD) of the United Arab Emirates (UAE) undertook an airborne gravity survey project for the marine area of the country in 2009, especially to strengthen the marine and coastal geoid in the near-shore regions. For the airborne gravity survey, 5 km spacing coast-parallel flight lines were planned and surveyed. These lines were supplemented by cross-lines in order to assess the quality of the airborne gravity surveys. The flight lines were extended 10 km, spacing lines further offshore. A Beech King Air 350 aircraft was used for the surveys, collecting data at a typicalflight speed of 170 knots and a typicalflight elevation of 900-1500 m, depending on weather conditions and topography. Gravity was measured with a ZLS-modzfied LaCoste and Romberg gravimeter (S-99), augmented with a Honeywell strap-down inertial navigation system unit. The estimated accuracy for the airborne gravity data is better than 2.0 mGal ,m.s., as judged from the airborne track crossovers. The new airborne gravimetry data changed the UAE coastal geoid by up to 30 cm in some regions, highlighting the importance of airborne gravity coastal surveys. [ABSTRACT FROM AUTHOR]

The processes of error development in an inertial navigation system are analysed. With this aim, the standard structures of error development were extracted in the inertial system. Error development was defined in the standard structures. Error development in the inertial navigation system is concluded according to the results obtained in the work. [ABSTRACT FROM AUTHOR]

We present a new method to accurately locate persons indoors by fusing inertial navigation system (INS) techniques with active RFID technology. A foot-mounted inertial measuring units (IMUs)-based position estimation method, is aided by the received signal strengths (RSSs) obtained from several active RFID tags placed at known locations in a building. In contrast to other authors that integrate IMUs and RSS with a loose Kalman filter (KF)-based coupling (by using the residuals of inertial- and RSS-calculated positions), we present a tight KF-based INS/RFID integration, using the residuals between the INS-predicted reader-to-tag ranges and the ranges derived from a generic RSS path-loss model. Our approach also includes other drift reduction methods such as zero velocity updates (ZUPTs) at foot stance detections, zero angular-rate updates (ZARUs) when the user is motionless, and heading corrections using magnetometers. A complementary extended Kalman filter (EKF), throughout its 15-element error state vector, compensates the position, velocity and attitude errors of the INS solution, as well as IMU biases. This methodology is valid for any kind of motion (forward, lateral or backward walk, at different speeds), and does not require an offline calibration for the user gait. The integrated INS+RFID methodology eliminates the typical drift of IMU-alone solutions (approximately 1% of the total traveled distance), resulting in typical positioning errors along the walking path (no matter its length) of approximately 1.5 m. [ABSTRACT FROM PUBLISHER]

Shoe mounted Inertial Measurement Units (IMU) are often used for indoor pedestrian navigation systems. The presence of a zero velocity condition during the stance phase enables Zero Velocity Updates (ZUPT) to be applied regularly every time the user takes a step. Most of the velocity and attitude errors can be estimated using ZUPTs. However, good heading estimation for such a system remains a challenge. This is due to the poor observability of heading error for a low cost Micro-Electro-Mechanical (MEMS) IMU, even with the use of ZUPTs in a Kalman filter. In this paper, the same approach is adopted where a MEMS IMU is mounted on a shoe, but with additional constraints applied. The three constraints proposed herein are used to generate measurement updates for a Kalman filter, known as ‘Heading Update’, ‘Zero Integrated Heading Rate Update’ and ‘Height Update’.The first constraint involves restricting heading drift in a typical building where the user is walking. Due to the fact that typical buildings are rectangular in shape, an assumption is made that most walking in this environment is constrained to only follow one of the four main headings of the building. A second constraint is further used to restrict heading drift during a non-walking situation. This is carried out because the first constraint cannot be applied when the user is stationary. Finally, the third constraint is applied to limit the error growth in height. An assumption is made that the height changes in indoor buildings are only caused when the user walks up and down a staircase. Several trials were shown to demonstrate the effectiveness of integrating these constraints for indoor pedestrian navigation. The results show that an average return position error of 4·62 meters is obtained for an average distance of 1557 meters using only a low cost MEMS IMU. [ABSTRACT FROM AUTHOR]

The procedure of determining the initial values of the attitude angles (pitch, roll, and heading) is known as the alignment. Also, it is essential to align an inertial system before the start of navigation. Unless the inertial system is not aligned with the vehicle, the information provided by MEMS (microelectromechanical system) sensors is not useful for navigating the vehicle. At the momentMEMSgyroscopes have poor characteristics and it's necessary to develop specific algorithms in order to obtain the attitude information of the object. Most of the standard algorithms for the attitude estimation are not suitable when using MEMS inertial sensors. The wavelet technique, the Kalman filter, and the quaternion are not new in navigation data processing. But the joint use of those techniques for MEMS sensor data processing can give some new results. In this paper the performance of a developed algorithm for the attitude estimation using MEMS IMU (inertial measurement unit) is tested. The obtained results are compared with the attitude output of another commercial GPS/IMU device by Xsens. The impact of MEMS sensor measurement noises on an alignment process is analysed. Some recommendations for the Kalman filter algorithm tuning to decrease standard deviation of the attitude estimation are given [ABSTRACT FROM AUTHOR]

To achieve the required navigation accuracy in some navigation applications, it is necessary to use a number of inertial sensors to obtain higher-quality acceleration/rotation rate measurements. For such redundant units, an inertial sensor fusion algorithm is required. This algorithm optimally combines all sensor outputs and generates a single inertial measurement that may be processed by any existing navigation software. In this study, a comprehensive framework for the inertial sensor fusion problem is presented for the skew-redundant inertial measurement units. An optimal sensor fusion algorithm is then developed for the skew-redundant units, where all of the inertial sensors are arbitrarily oriented in space without any lever-arm effect. An error model for the algorithm output is also derived, and it is shown that under certain conditions, the number of states for these error models can be greatly reduced. Simulation test results show that when inertial sensors with complimentary characteristics are used, the proposed fusion algorithm can be used to form high-accuracy inertial measurements, which inherit all the best characteristics of the constituent sensors in the skew-redundant units. [ABSTRACT FROM AUTHOR]

Micro-Doppler features have intrinsic relations with the physical properties of objects, which provide great potential for use in the target discrimination. A model and theoretical analysis of micro-Doppler based on inertial parameters for aerospace rigid targets are presented. According to the attitude kinematics in space, mathematical formulas of the micro-Doppler model based on inertial parameters are derived without the limitation of micro-motion types. Moments of inertia and initial rotational angular velocities are used to analyse their impact on micro-motions and micro-Doppler of free rigid targets. After the simulation of radar echoes from objects with various micro-motions, the joint time-frequency analysis is then utilised to demonstrate the time-varying micro-Doppler features and confirm the effectiveness of the model and theoretical analysis. The proposed method highlights the relationship between the model and the attributes of objects and gets rid of the restriction on the specified target shapes, which illustrates more explicit physical meaning and flexibility in the application. [ABSTRACT FROM AUTHOR]

This paper provides an extensive overview of existing vehicle dynamic state estimators that utilise the in-car Inertial Navigation Sensors and Global Positioning System. The different approaches are categorised, the techniques are summarised and the limitations and advantages of each approach are provided. Recommendations for future research are also given. The review is intended to be fairly comprehensive, but with an emphasis on vehicle sideslip estimation. [ABSTRACT FROM AUTHOR]

Currently, the concept of multisensor system integration is implemented in land-vehicle navigation (LVN) applications. The most common LVN multisensor configuration incorporates an integrated Inertial Navigation System/Global Positioning System (INS/GPS) system based on the Kalman filter (KF). For LVN, the demand is directed toward low-cost inertial sensors such as microelectromechanical systems (MEMS). Due to the combined problem of frequent GPS signal loss during navigation in urban centers and the rapid time-growing inertial navigation errors when the INS is operated in stand-alone mode, some methodologies should be applied to improve the LVN accuracy in these cases. One of these approaches is to apply smoothing algorithms such as the Rauch–Tung–Striebel smoother (RTSS), which uses only the output of the forward KF. In this paper, the development of the two-filter smoother (TFS) algorithm and its implementation in LVN applications is introduced. Two different LVN INS/GPS data sets that include tactical-grade and MEMS inertial measuring units are utilized to validate the TFS algorithm and to compare its performance with the RTSS. [ABSTRACT FROM PUBLISHER]

Abstract: Pin-point landing is considered as a key technology for future manned Mars landing and Mars base missions. The traditional inertial navigation system (INS) based guidance, navigation and control (GNC) mode used in the Mars entry, descent and landing (EDL) phase has no ability to achieve the precise and safe Mars landing, so novel EDL GNC methodologies should be investigated to meet this goal. This paper proposes the MCAV/IMU integrated navigation scheme for the powered descent phase of Mars EDL. The Miniature Coherent Altimeter and Velocimeter (MCAV) is adopted to correct the inertial bias and drift and improve the performance of integrated navigation. Altitude and velocity information derived from MCAV and the lander’s state information sensed by inertial measurement unit (IMU) are integrated in extended Kalman filter algorithm. The validity of the proposed navigation scheme is confirmed by computer simulation. [ABSTRACT FROM AUTHOR]

The integration of strapdown inertial navigation system (SINS) with an astronavigation system (ANS) using fuzzy logic to adapt the Kalman filter is investigated in this study. A method is proposed that is based on fuzzy rules to adjust the parameters of a traditional Kalman filter. Simulation results for a spacecraft application demonstrate the validity of the method for improving the navigation system reliability, adaptability and performance. [ABSTRACT FROM AUTHOR]

Abstract: A nonlinear observer (i.e. a “filter”) is proposed for estimating the attitude of a flying rigid body, using measurements from low-cost inertial and magnetic sensors. It has by design a nice geometrical structure appealing from an engineering viewpoint; it is easy to tune, computationally very thrifty, and with guaranteed (at least local) convergence around every trajectory. Moreover it behaves sensibly in the presence of acceleration and magnetic disturbances. Experimental comparisons with a commercial device illustrate its good performance; an implementation on an 8-bit microcontroller with very limited processing power demonstrates its computational simplicity. [Copyright &y& Elsevier]

This paper presents an innovative method for estimating the attitude of airborne electro-optical cameras with respect to the onboard autonomous navigation unit. The procedure is based on the use of attitude measurements under static conditions taken by an inertial unit and carrier-phase differential Global Positioning System to obtain accurate camera position estimates in the aircraft body reference frame, while image analysis allows line-of-sight unit vectors in the camera based reference frame to be computed. The method has been applied to the alignment of the visible and infrared cameras installed onboard the experimental aircraft of the Italian Aerospace Research Center and adopted for in-flight obstacle detection and collision avoidance. Results show an angular uncertainty on the order of 0.1° (rms). [ABSTRACT FROM AUTHOR]

The diffusion of micro electro-mechanical systems (MEMS) technology applied to navigation systems is rapidly increasing, but currently, there is a lack of knowledge about the reliability of this typology of devices, representing a serious limitation to their use in aerospace vehicles and other fields with medium and high requirements. In this paper, a reliability testing procedure for inertial sensors and inertial measurement units (IMU) based on MEMS for applications in vibrating environments is presented. The sensing performances were evaluated in terms of signal accuracy, systematic errors, and accidental errors; the actual working conditions were simulated by means of an accelerated dynamic excitation. A commercial MEMS-based IMU was analyzed to validate the proposed procedure. The main weaknesses of the system have been localized by providing important information about the relationship between the reliability levels of the system and individual components. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) is very important for battlefield awareness. For SAR systems mounted on a UAV, the motion errors can be considerably high due to atmospheric turbulence and aircraft properties, such as its small size, which makes motion compensation (MOCO) in UAV SAR more urgent than other SAR systems. In this paper, based on 3-D motion error analysis, a novel 3-D MOCO method is proposed. The main idea is to extract necessary motion parameters, i.e., forward velocity and displacement in line-of-sight direction, from radar raw data, based on an instantaneous Doppler rate estimate. Experimental results show that the proposed method is suitable for low- or medium-altitude UAV SAR systems equipped with a low-accuracy inertial navigation system. [ABSTRACT FROM AUTHOR]

The accurate location of a vehicle in the road is one of the most important challenges in the automotive field. The need for accurate positioning affects several in-vehicle systems like navigators, lane departure warning systems, collision warning and other related sectors such as digital cartography suppliers. The aim of this paper is to evaluate high precision positioning systems that are able to supply an on-the-centimetre accuracy source to develop on-the-lane positioning systems and to be used in future applications as an information source for autonomous vehicles that circulate at high speeds on public roads. In this paper we have performed some on-road experiments, testing several GPS-based systems: Autonomous GPS; RTK Differential GPS with a proprietary GPS base station; RTK Differential GPS connected to the public GPS base station network of the National Geographic Institute of Spain via vehicle-to-infrastructure GPRS communications; and GPS combination with inertial measurement systems (INS) for position accuracy maintenance in degraded satellite signal reception areas. In these tests we show the validity and the comparison of these positioning systems, allowing us to navigate, in some cases, on public roads at speeds near 120 km/h and up to 100 km from the start position without any significant accuracy reduction. [ABSTRACT FROM AUTHOR]

To represent 3-D space in detail, it is necessary to( acquire 3-D shapes and textures simultaneously and efficiently through the use of precise trajectories of sensors. However, there is no reliable, quick, cheap, and handy method for acquiring accurate high-resolution 3-D data on objects in outdoor and moving environments. In this paper, we propose a combination of charge-coupled device cameras, a small and inexpensive laser scanner, an inexpensive inertial measurement unit, and Global Positioning System for a UAV-borne 3-D mapping system. Direct georeferencing is achieved automatically using all of the sensors without any ground control points. A new method of direct georeferencing by the combination of bundle block adjustment and Kalman filtering is proposed. This allows objects to be rendered richly in shape and detailed texture automatically via a UAV from low altitude. This mapping system has been experimentally used in recovery efforts after natural disasters such as landslides, as well as in applications such as river monitoring. [ABSTRACT FROM AUTHOR]

This correspondence investigates the convergence of a Kalman filter-based expectation-maximization (EM) algorithm for estimating variances. It is shown that if the variance estimates and the error covariances are initialized appropriately, the underlying Riccati equation solution and the sequence of iterations will be monotonically nonincreasing. Further, the process noise variance estimates converge to the actual values when the measurement noise becomes negligibly small. Conversely, when the process noise variance becomes negligible, the measurement noise variance estimates asymptotically approach the true values. An inertial navigation application is discussed in which performance depends on accurately estimating the process variances. [ABSTRACT FROM AUTHOR]