GPS and navigation GPS)، GLONASS، GALILEO
Seyed Ali Zahiripour
Volume 17, Issue 1 , March 2024, , Pages 1-9
Abstract
A method for increasing the accuracy of the initial alignment process of inertial navigation systems with a stable platform is presented through state feedback control in flight mode. In the presented method, the state feedback controller is designed by using the stable plate deviation angles and the ...
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A method for increasing the accuracy of the initial alignment process of inertial navigation systems with a stable platform is presented through state feedback control in flight mode. In the presented method, the state feedback controller is designed by using the stable plate deviation angles and the sensor error which is extracted with the help of Kalman filter. To do this, while checking the observability of the system, by adding suitable flight maneuvers and expressing the equations of propagation of navigation error, in the form of a fixed piece system with time, it is possible to estimate the angles and errors of the sensors in the align phase. The groundwork is provided for the design of state feedback. Then, taking into account the stable platform motion equations and using the principle of separation of observer and controller design, a state feedback controller is designed. In the end, the simulation results of the proposed method show an increase in the accuracy of the alignment process and, consequently, an increase in the accuracy of the navigation, compared to the conventional output feedback method.
GPS and navigation GPS)، GLONASS، GALILEO
Tania Mansour Fallah; Behzad Voosoghi; Seyyed Reza Ghaffari-Razin
Volume 17, Issue 1 , March 2024, , Pages 21-36
Abstract
In this paper, the aim is to use the least squares support vector regression (LS-SVR) for spatio-temporal modeling of the ionospheric total electron content (TEC). In order to do this, the observations of 15 GPS stations in the north-west of Iran have been used in the period from 193 to 228 at 2012. ...
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In this paper, the aim is to use the least squares support vector regression (LS-SVR) for spatio-temporal modeling of the ionospheric total electron content (TEC). In order to do this, the observations of 15 GPS stations in the north-west of Iran have been used in the period from 193 to 228 at 2012. Comparing the results of the new model with support vector regression (SVR), artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), Kriging model, GIM and international reference ionosphere 2016 (IRI2016) as well as TEC obtained from GPS. The analyzes performed show that the averaged RMSE of ANN, ANFIS, SVR, LS-SVR, Kriging, GIM and IRI2016 models in two interior control stations are 3.91, 2.73, 1.27, 1.04, 2.70, 3.02 and 6.93 TECU, respectively. Also, the averaged relative error of the models in two interior control stations was calculated as 15.98%, 9.39%, 7.85%, 6.09%, 11.60%, 12.54% and 26.56%, respectively. Analysis of the PPP method shows an improvement of 50 mm in the coordinate components using the LS-SVR model. The results of this paper show that the LS-SVR model can be considered as an alternative to global and empirical models of the ionosphere in the study area.
GPS and navigation GPS)، GLONASS، GALILEO
Mona Zahednamazi; Alireza Toloui
Volume 16, Issue 4 , December 2023, , Pages 57-70
Abstract
One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the ...
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One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the star identification algorithm based on singular value decomposition. To improve the identification results, modifications have been made to the algorithm. Also, analysis and simulation are presented to investigate the effect of field of view dimensions and the number of stars used on the identification results, and the rate of duplicate sets in the database. In addition, identification has been considered a two-step process based on singular values and vectors. The results show the superiority of the improved algorithm in increasing the identification rate and reducing the rate of duplicate sets in the database. The identification rate of the improved algorithm in 〖10〗^°×〖10〗^° and 〖12〗^°×〖12〗^° fields of view dimension is always more the %97. The simulations were performed based on the Hipparcos star catalog for stars brighter than magnitude 6.5 and using MATLAB software.
GPS and navigation GPS)، GLONASS، GALILEO
Reza Ghasrizadeh; Amir Ali Nikkhah
Volume 16, Issue 3 , September 2023, , Pages 37-49
Abstract
This paper presents a solution for detecting and recovery for the spoof error of GPS receiver signals, in order to increase the accuracy of the navigation system integrating inertial systems with GPS signals. integrated inertial navigation and GPS data has many advantages. However, due to the weakness ...
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This paper presents a solution for detecting and recovery for the spoof error of GPS receiver signals, in order to increase the accuracy of the navigation system integrating inertial systems with GPS signals. integrated inertial navigation and GPS data has many advantages. However, due to the weakness of satellite signals against jamming and spoof attacks of providing analytical solutions, they have a special place in improving Kalman filter estimation compared to hardware solutions. In this paper, a new method for loosely coupled of INS/GPS is presented, in which the steady state of Kalman gain parameters is used during deception detection and recovery. With the gain parameters of the Kalman filter tending to constant values, with the aim of correcting and predicting the error of state variables, it can be used to detection GPS spoofed data. It can be detected by spoof in the GPS receiver signal when couple with inertial waves through the amount of Kalman gain fluctuations. In the case of closed loop, the Kalman gain matrix denominators tend to a constant value, and in case of deception, this function is associated with many fluctuations. By using dynamic weighting, the effect of errors caused by these attacks is recovered.
GPS and navigation GPS)، GLONASS، GALILEO
Mohsen Shamirzaei; Mehran Mir Shams
Volume 14, Issue 3 , September 2021, , Pages 75-90
Abstract
The main task of the study is to estimate the position error in an inertial navigation system by integrating it with the visual system. The case study is a spacecraft that must accurately measure its position relative to a predetermined landing point. The spacecraft is assumed to be augmented GNSS navigation. ...
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The main task of the study is to estimate the position error in an inertial navigation system by integrating it with the visual system. The case study is a spacecraft that must accurately measure its position relative to a predetermined landing point. The spacecraft is assumed to be augmented GNSS navigation. Therefore, when satellite signals are dropped out or when landing on a moving marine platform, the data of the vision navigation system replaces the information of the satellite navigation system and improves the accuracy of the spacecraft navigation system. An Extended Kalman filter has been used to integrate inertial and vision navigation system information. In addition, the output data of the vision system, in order to be used in the Kalman filter measurement equations, is first processed by the recursive least square filter. The relevant relations are given and based on the results of software simulation, the efficiency of the proposed method is shown.
GPS and navigation GPS)، GLONASS، GALILEO
MohammadAli Amiri Atashgah; Seyyed Mohammad-Jafar Tabib
Volume 14, Issue 2 , June 2021, , Pages 49-59
Abstract
This research represents localization of an aerial robot using fisheye cameras on walls in a simulation environment. The virtual testbed in this work is a quadrotor that is simulated in MATLAB Simulink. Subsequently, the simulation outputs as flight records are used in a virtual lab, which is developed ...
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This research represents localization of an aerial robot using fisheye cameras on walls in a simulation environment. The virtual testbed in this work is a quadrotor that is simulated in MATLAB Simulink. Subsequently, the simulation outputs as flight records are used in a virtual lab, which is developed in 3DsMAX. Then, the virtual fisheye cameras (here two) are installed in some different points on the walls and the related images from the cameras are received offline. The gathered images will be processed by OpenCV in a C++ environment. For external calibration, each fisheye camera takes an image from a known pattern consist of some lights placed in the virtual lab. We execute Perspective-n-Point method on the images to obtain pierce direction/position of the camera. For more, the aerial robot is localized by computing the nearest point between two lines of sight. In brief, the outcomes exhibit an accuracy of 4cm in the center of the virtual-room room.
GPS and navigation GPS)، GLONASS، GALILEO
Reza Ghasrizadeh; Amirali Nikkhah
Volume 13, Issue 4 , December 2020, , Pages 81-90
Abstract
This paper presents a new approach to eliminating noise and disturbances in the corse alignment process for inertial navigation systemsBecause of extreme fluctuations and quasi-static environments, the corse alignment process often involves a lot of errors and noise. Initially, the coarse alignment process ...
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This paper presents a new approach to eliminating noise and disturbances in the corse alignment process for inertial navigation systemsBecause of extreme fluctuations and quasi-static environments, the corse alignment process often involves a lot of errors and noise. Initially, the coarse alignment process for inertial navigation systems is described exhaustively and then, with the assumption of disturbances and noise, we attempt to nudify to improve and initialize the initialization accuracy. Subsequently, introducing the filtering characteristics of the digital filter for the mutation , Due to the deletion of some of the sensor's main data, identifies the missing parameters and estimates the state variables using the Kalman filter matrix based on the variance of the data error. Identifying the missing parameters of the transformation matrix in the coordinate system using the Kalman filter Matrix is the innovation of this paper, which leads to improved note coarse alignment will be inertial navigation systems.
GPS and navigation GPS)، GLONASS، GALILEO
Mir Reza Ghaffari Razin; Behzad Voosoghi
Volume 13, Issue 3 , September 2020, , Pages 39-50
Abstract
In this paper, WNN with PSO training algorithm is used to modeling and prediction of time-dependent ionosphere total electron content (TEC) variations. 2 different combinations of input observations are evaluated. The number of stations used to train of WNN with PSO algorithm selected 20 and 10. In all ...
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In this paper, WNN with PSO training algorithm is used to modeling and prediction of time-dependent ionosphere total electron content (TEC) variations. 2 different combinations of input observations are evaluated. The number of stations used to train of WNN with PSO algorithm selected 20 and 10. In all testing mode, 3 GPS stations with proper distribution are considered as a testing stations. Statistical indicators relative error, dVTEC and correlation coefficient were used to assess the wavelet neural network model. The results of proposed model compared with GPS-TEC and international reference ionosphere 2012 (IRI-2012) TEC. Average relative error computed in 3 test stations are 5.43% with 20 training station and 9.05% with 10 training station. Also the correlation coefficient calculated in 3 test stations are 0.954 with 20 training station and 0.907 with 10 training station. The results of this study show that the WNN with PSO algorithm is a reliable model to predict the temporal variations in the ionosphere.
GPS and navigation GPS)، GLONASS، GALILEO
Mohammad Hosein Shafiei; meisam jowkar; Behrooz Safarinejad
Volume 13, Issue 3 , September 2020, , Pages 69-77
Abstract
In this paper a new structure for the inertia measurement unit is presented; the proposed structure consists of three rotary discs around the three main axes in the body, and an accelerometer is mounted on each disc. It is shown in this paper that the proposed structure reduces the effect of disturbing ...
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In this paper a new structure for the inertia measurement unit is presented; the proposed structure consists of three rotary discs around the three main axes in the body, and an accelerometer is mounted on each disc. It is shown in this paper that the proposed structure reduces the effect of disturbing accelerometer parameters, such as constant and variable bias, as well as noise depletion. Due to the proposed rotational structure, it is necessary to continuously sample the accelerometers. In order to use the sampled data, calculations should be performed in discrete mode. In this paper, a method for combining this information is presented. By examining the proposed equations, the successful performance of this method is shown in the reduction of the effect of three constant bias parameters and the bias of the accelerometer and the measured noise. As well as the efficiency of the proposed method for measuring the acceleration of the device using Numerical representation is shown.
GPS and navigation GPS)، GLONASS، GALILEO
Mojtaba Behzad Fallahpour; Hamid Dehghani; Ali Jabbar Rashidi; Abbas Sheikhi
Volume 12, Issue 4 , December 2019, , Pages 47-56
Abstract
Reflectors are a very important tools in counteracting the space borne or airborne SAR imaging systems. Because they can be used in the form of decoy and camouflage protection designs due to their high level RCS. The remarkable thing on this mission is that the SAR radar is capable of sending the wave ...
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Reflectors are a very important tools in counteracting the space borne or airborne SAR imaging systems. Because they can be used in the form of decoy and camouflage protection designs due to their high level RCS. The remarkable thing on this mission is that the SAR radar is capable of sending the wave to earth in any direction, with any incident angle and in any frequency band, and capturing sensitive areas. The design of such an all-directional, multi-band reflector, and wide angles reflector is very complicated because the reflex function depends on various parameters such as the dimensions, shape and material of the reflector, the frequency, the incident angle, and the polarization of the radiated wave. Existing refractors generally have a high RCS in a particular direction at a specific frequency and at a narrow viewing angle. In this paper, we will attempt to design a refractor of all directions, multiple bands and wide angles using shape structures.
