Optimising the Transfer Alignment of Weapon INS

2003 ◽  
Vol 56 (2) ◽  
pp. 323-335 ◽  
Author(s):  
Paul D. Groves
Keyword(s):  
Inertial Sensor ◽  
Integrated Navigation ◽  
Velocity Measurements ◽  
Transfer Alignment ◽  
Navigation Solution ◽  
Alignment Technique ◽  
Alignment Process ◽  
Using Data ◽  
Design Options ◽  
Better Than

Transfer alignment is the process of initialising and calibrating a weapon INS using data from the host aircraft's navigation system. To determine which transfer alignment technique performs best, different design options have been assessed, supported by simulation work. The dependence of transfer alignment performance on environmental factors, such as manoeuvres, alignment duration, lever arm and inertial sensor quality has also been studied. ‘Rapid’ alignment, using attitude as well as velocity measurements was found to perform better than ‘conventional’ techniques using only velocity. Innovative developments include the estimation of additional acceleration and gyro states and estimation of force dependent relative orientation, which has enabled robust alignment using wing rock manoeuvres, which do not require the pilot to change trajectory. Transfer alignment has been verified in real-time by flight trials on a Tornado aircraft. In addition, techniques have been developed to prevent transients in the aircraft integrated navigation solution following GPS re-acquisition after an outage of several minutes from disrupting the transfer alignment process.

scholarly journals Implementation of Parallel Cascade Identification at Various Phases for Integrated Navigation System

2021 ◽  
Vol 13 (8) ◽  
pp. 191
Author(s):  
Umar Iqbal ◽  
Ashraf Abosekeen ◽  
Jacques Georgy ◽  
Areejah Umar ◽  
Aboelmagd Noureldin ◽  
...  
Keyword(s):  
Navigation System ◽  
Inertial Sensor ◽  
Integrated System ◽  
Experimental Results ◽  
Integrated Navigation ◽  
Navigation Solution ◽  
Parallel Cascade Identification ◽  
Non Linear ◽  
Tightly Coupled ◽  
Non Linear System

Global navigation satellite systems (GNSS) are widely used for the navigation of land vehicles. However, the positioning accuracy of GNSS, such as the global positioning system (GPS), deteriorates in urban areas due to signal blockage and multipath effects. GNSS can be integrated with a micro-electro-mechanical system (MEMS)–based inertial navigation system (INS), such as a reduced inertial sensor system (RISS) using a Kalman filter (KF) to enhance the performance of the integrated navigation solution in GNSS challenging environments. The linearized KF cannot model the low-cost and small-size sensors due to relatively high noise levels and compound error characteristics. This paper reviews two approaches to employing parallel cascade identification (PCI), a non-linear system identification technique, augmented with KF to enhance the navigational solution. First, PCI models azimuth errors for a loosely coupled 2D RISS integrated system with GNSS to obtain a navigation solution. The experimental results demonstrated that PCI improved the integrated 2D RISS/GNSS performance by modeling linear, non-linear, and other residual azimuth errors. For the second scenario, PCI is utilized for modeling residual pseudorange correlated errors of a KF-based tightly coupled RISS/GNSS navigation solution. Experimental results have shown that PCI enhances the performance of the tightly coupled KF by modeling the non-linear pseudorange errors to provide an enhanced and more reliable solution. For the first algorithm, the results demonstrated that PCI can enhance the performance by 77% as compared to the KF solution during the GNSS outages. For the second algorithm, the performance improvement for the proposed PCI technique during the availability of three satellites was 39% compared to the KF solution.

An Improved and Efficient Algorithm for SINS/GPS/Doppler Integrated Navigation Systems

2012 ◽  
Vol 245 ◽  
pp. 323-329 ◽  
Author(s):  
Muhammad Ushaq ◽  
Jian Cheng Fang
Keyword(s):  
Kalman Filter ◽  
Navigation System ◽  
Inertial Navigation System ◽  
Inertial Sensor ◽  
Inertial Navigation ◽  
Measurement Unit ◽  
Navigation Systems ◽  
Integrated Navigation ◽  
Efficient Manner ◽  
Position Errors

Inertial navigation systems exhibit position errors that tend to grow with time in an unbounded mode. This degradation is due, in part, to errors in the initialization of the inertial measurement unit and inertial sensor imperfections such as accelerometer biases and gyroscope drifts. Mitigation to this growth and bounding the errors is to update the inertial navigation system periodically with external position (and/or velocity, attitude) fixes. The synergistic effect is obtained through external measurements updating the inertial navigation system using Kalman filter algorithm. It is a natural requirement that the inertial data and data from the external aids be combined in an optimal and efficient manner. In this paper an efficient method for integration of Strapdown Inertia Navigation System (SINS), Global Positioning System (GPS) and Doppler radar is presented using a centralized linear Kalman filter by treating vector measurements with uncorrelated errors as scalars. Two main advantages have been obtained with this improved scheme. First is the reduced computation time as the number of arithmetic computation required for processing a vector as successive scalar measurements is significantly less than the corresponding number of operations for vector measurement processing. Second advantage is the improved numerical accuracy as avoiding matrix inversion in the implementation of covariance equations improves the robustness of the covariance computations against round off errors.

scholarly journals Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)

2018 ◽  
Vol 618 ◽  
pp. A116 ◽  
Author(s):  
J. Prieto-Arranz ◽  
E. Palle ◽  
D. Gandolfi ◽  
O. Barragán ◽  
E. W. Guenther ◽  
...  
Keyword(s):  
Planetary System ◽  
Initial Conditions ◽  
Dynamical Evolution ◽  
Space Mission ◽  
Mass Determination ◽  
Velocity Measurements ◽  
Orbital Periods ◽  
The Masses ◽  
Better Than

Context. Multiplanet systems are excellent laboratories to test planet formation models as all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (~30 pc) detected by NASA’s Kepler or K2 space mission. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with high-precision radial-velocity measurements gathered with the FIES, HARPS, and HARPS-N spectrographs we revised the system parameters and derive the masses of the three planets. Results. We find that GJ 9827 b has a mass of Mb = 3.69−0.46+0.48 M⊕ and a radius of Rb = 1.58−0.13+0.14 R⊕, yielding a mean density of ρb = 5.11−1.27+1.74 g cm−3. GJ 9827 c has a mass of Mc = 1.45−0.57+0.58 M⊕, radius of Rc = 1.24−0.11+0.11 R⊕, and a mean density of ρc = 4.13−1.77+2.31 g cm−3. For GJ 9827 d, we derive Md = 1.45−0.57+0.58 M⊕, Rd = 1.24−0.11+0.11 R⊕, and ρd = 1.51−0.53+0.71 g cm−3. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and sub-Neptunes. The planetary bulk compositions are compatible with a scenario where all three planets formed with similar core and atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its primordial atmosphere, owing to the much lower stellarirradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmosphericescape can be studied in detail for all planets, helping us to understand how compact systems form and evolve.

scholarly journals Aerosol optical depth in the European Brewer Network

2017 ◽  
Author(s):  
Javier López-Solano ◽  
Alberto Redondas ◽  
Thomas Carlund ◽  
Juan J. Rodriguez-Franco ◽  
Henri Diémoz ◽  
...  
Keyword(s):  
Real Time ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Temporal Variability ◽  
Input Data ◽  
Spatial And Temporal Variability ◽  
Ultraviolet Range ◽  
Using Data ◽  
Better Than

Abstract. The high spatial and temporal variability of aerosols make networks capable of measuring their properties in near real time of high scientific interest. In this work we present and discuss results of an aerosol optical depth algorithm to be used in the European Brewer Network, which provides data in near real time of more than 30 spectrophotometers located from Tamanrasset (Algeria) to Kangerlussuaq (Greenland). Using data from the Brewer Intercomparison Campaigns in the years 2013 and 2015, and the period in between, plus comparisons with Cimel sunphotometers and UVPFR instruments, we check the precision, stability, and uncertainty of the Brewer AOD in the ultraviolet range from 300 to 320 nm. Our results show a precision better than 0.01, an uncertainty of less than 0.05, and a stability similar to that of the ozone measurements for well-maintained instruments. We also discuss future improvements to our algorithm with respect to the input data, their processing, and the characterization of the Brewer instruments for the measurement of aerosols.

scholarly journals Discrete EKF with pairwise Time Correlated Measurement Noise for Image-Aided Inertial Integrated Navigation

2014 ◽  
Vol II-2 ◽  
pp. 61-66 ◽  
Author(s):  
N. S. Gopaul ◽  
J. G. Wang ◽  
B. Hu
Keyword(s):  
Kalman Filter ◽  
Inertial Navigation ◽  
Measurement Noise ◽  
Integrated Navigation ◽  
Process Noise ◽  
Shaping Filter ◽  
Egomotion Estimation ◽  
Simulation Results ◽  
The One ◽  
Better Than

An image-aided inertial navigation implies that the errors of an inertial navigator are estimated via the Kalman filter using the aiding measurements derived from images. The standard Kalman filter runs under the assumption that the process noise vector and measurement noise vector are white, i.e. independent and normally distributed with zero means. However, this does not hold in the image-aided inertial navigation. In the image-aided inertial integrated navigation, the relative positions from optic-flow egomotion estimation or visual odometry are <i>pairwise</i> correlated in terms of time. It is well-known that the solution of the standard Kalman filter becomes suboptimal if the measurements are colored or time-correlated. Usually, a shaping filter is used to model timecorrelated errors. However, the commonly used shaping filter assume that the measurement noise vector at epoch <i>k</i> is not only correlated with the one from epoch <i>k</i> &ndash; 1 but also with the ones before epoch <i>k</i> &ndash; 1 . The shaping filter presented in this paper uses Cholesky factors under the assumption that the measurement noise vector is pairwise time-correlated i.e. the measurement noise are only correlated with the ones from previous epoch. Simulation results show that the new algorithm performs better than the existing algorithms and is optimal.

Successful application of optical bench in Taiji-1 laser interferometer

2021 ◽  
pp. 2140001
Author(s):  
Wei Sha ◽  
Chao Fang ◽  
Yu Niu ◽  
Keyword(s):  
Performance Test ◽  
Inertial Sensor ◽  
Laser Interferometry ◽  
Linear Expansion Coefficient ◽  
Optical Bench ◽  
Satellite Design ◽  
Modulation Signal ◽  
Alignment Errors ◽  
Optical Paths ◽  
Better Than

As an important part of laser interferometry system, optical bench is one of the core technologies for the detection of spaceborne gravitational waves. As the first step of the space Taiji program, Taiji-1 provides the measurement accuracy of laser interferometry system better than 100 pm/Hz[Formula: see text](@10 mHz–1 Hz). Taiji-1 is required to be able to track the motion of test mass in inertial sensor. According to the requirements, four interfering optical paths were designed. By adopting an integrated satellite design and selecting the optical and mechanical materials with low linear expansion coefficient, the high stability of optical path was achieved. By using the DOE method, the alignment errors (position/attitude) of four optical paths were all reduced to below 50 [Formula: see text]m/100 [Formula: see text]rad. In the performance test, the accuracy of laser interferometry system was better than 100 pm/Hz[Formula: see text](@10 mHz–1 Hz), and the modulation signal of inertial sensor was successfully detected. The results show that all technical indexes of optical bench have met or exceeded the design requirements.

scholarly journals Specialization and Performance: Evidence from NCAA 4 × 400 m Relay Times

Economies ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 96
Author(s):  
Candon Johnson ◽  
Robert Schultz ◽  
Joshua C. Hall
Keyword(s):  
Performance Measure ◽  
Division I ◽  
Division Iii ◽  
Overall Performance ◽  
The Difference ◽  
And Performance ◽  
Using Data ◽  
The Impact ◽  
Better Than

This paper investigates the impact of having open 400 meter (400 m) runners on NCAA relay teams. Using data from 2012–2016 containing the top 100 4 × 400 m in each NCAA Division relay times for each year, it is found that more 400 m specialists lead to an increase in the overall performance of the team, measured by a decrease in relay times. The effect is examined across Division I–III NCAA track teams. The results are consistent across each division. We view this as a test of the role of specialization on performance. Using runners who specialize in 400 m races should increase overall team performance as long as specialization does not lead to an inefficient allocation of team human capital. An additional performance measure is used examining the difference between projected and actual relay times. Divisions I and II are found to perform better than projected with an increase in 400 m runners, but there is no effect found in Division III.

A New Approach Based on the Bee Optimization Algorithm for Ontology Alignment

2019 ◽  
Vol 9 (4) ◽  
pp. 13-22
Author(s):  
Fatima Ardjani ◽  
Djelloul Bouchiha
Keyword(s):  
Similarity Measures ◽  
Optimization Method ◽  
Ontology Alignment ◽  
New Approach ◽  
Alignment System ◽  
Alignment Process ◽  
Joint Consideration ◽  
Bee Colonies ◽  
Web Research ◽  
Better Than

The ontology alignment process aims at generating a set of correspondences between entities of two ontologies. It is an important task, notably in the semantic web research, because it allows the joint consideration of resources defined in different ontologies. In this article, the authors developed an ontology alignment system called ABCMap+. It uses an optimization method based on artificial bee colonies (ABC) to solve the problem of optimizing the aggregation of three similarity measures of different matchers (syntactic, linguistic and structural) to obtain a single similarity measure. To evaluate the ABCMap+ ontology alignment system, authors considered the OAEI 2012 alignment system evaluation campaign. Experiments have been carried out to get the best ABCMap+'s alignment. Then, a comparative study showed that the ABCMap+ system is better than participants in the OAEI 2012 in terms of Recall and Precision.

Virtual vs physical platform: organizational capacity and slack, strategic decision and firm performance

2020 ◽  
Vol 35 (12) ◽  
pp. 1983-1995 ◽  
Author(s):  
Hang Lee ◽  
Yung-Chang Hsiao ◽  
Chung-Jen Chen ◽  
Ruey-Shan Guo
Keyword(s):  
Firm Performance ◽  
Empirical Support ◽  
Organizational Capacity ◽  
Strategic Choice ◽  
Retail Industry ◽  
Content Type ◽  
Using Data ◽  
Virtual Platform ◽  
The Relationship ◽  
Better Than

Purpose This study aims to examine the relationship between organizational capacity, slack resource, platform strategic choice and firm performance. It also tackles the endogenous issues regarding the strategic choice of platform types. Design/methodology/approach This study uses Heckman’s two-stage procedures to examine the relationship between the variables. The sample in this study comes from Compustat annual company and segment files. The sample used in the main analysis consists of 252 individual corporations globally and 3,528 firm-year observations from 2004–2017. Findings The empirical results suggest that: (1) firms are more likely to develop physical platforms than virtual platforms when they possess higher levels of available slack, potential slack, research and development (R&D) capacity and marketing capacity; (2) in general, firms developing physical platforms perform better than firms developing virtual platforms after the endogeneity bias are controlled; and (3) firms that choose to develop physical platforms perform better than if they had chosen to develop virtual platforms. Research limitations/implications This study contributes to the platform research literature by proposing the endogenous role of platform type choice in firm performance in the context of the retail industry. Prior conceptual and theoretical platform studies have seldom focused on the retail industry through a strategic choice perspective. Furthermore, one of the contributions of this study is the derivation of empirical support for the research’s prediction using data from actual firms carried out by global physical and virtual platform companies. This study also presents many opportunities for further explorations on the relationship between firm strategic choice and firm performance in the context of platform retail industry. Practical implications The findings of this study suggest that firms must realize that their performance is not necessarily affected by these platform type choice determinants in terms of potential slack, available slack, R&D capacity and marketing capacity. By contrast, they should pay more attention to developing physical platforms if it is possible. The study findings indicate that although virtual platforms have grown rapidly because of the development of technology, firm performance is at all times superior when firms choose to develop physical platforms. Originality/value Prior platform studies have focused on the topic of network structure, platform architecture, pricing strategy, platform leadership and platform design and governance within the context of video game industry, software industry, hardware industry and telecommunications industry. Seldom of them focus on other industries through a strategic choice perspective. Furthermore, one of the contributions of this study is the derivation of empirical support for the research’s prediction using data from actual firms carried out by global physical and virtual platform companies.

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