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Experimental Attitude Determination Using Thermal Data
, M.Sc. Thesis Sharif University of Technology ; Pourtakdoost, Hossein (Supervisor)
Abstract
The problem of attitude determination (AD) has always been a challenging issue for space missions that is of importance either independently or for attitude control purposes. The problem of AD is generally focused from two aspects: measurement mechanisms (sensoring) and determination algorithms. From the former point of view, there exists a variety of measuring systems such as the Sun sensors, magnetometers, gyroscopes, star and horizon sensors that have been separately or collaboratively utilized for AD. Integrative usage of sensors not only can bring about added advantages in terms of accuracy, but also provides for estimates of attitude during special times such as the Sun eclipse. The...
Attitude and Deformation Estimation of Flexible Satellite Using Magnetometer and Sun Sensor
, M.Sc. Thesis Sharif University of Technology ; Asadian, Nima (Supervisor)
Abstract
The estimation of attitude and deformation of a flexible satellite using magnetometer and sun sensor data are studied in this thesis. To this end, the dynamical differential equations of the flexible satellite have been derived using Lagrange’s equation. These equations of motion are then utilized for the purpose of simulation and verification. After introducing the measurements equations, the observability of the satellite with flexible panels has been evaluated. Afterward, the attitude of the satellite body and deformation of the flexible panels have been estimated by EKF (Extended Kalman Filter) as well as UKF (Unscented Kalman Filter). The results show that the estimations using UKF are...
Optimal Design & Fabrication of a Non-Flat Sun Sensor Array With Large Field of View
, Ph.D. Dissertation Sharif University of Technology ; Durali, Mohammad (Supervisor) ; Jalali, Mir Abbas (Supervisor)
Abstract
Modern sensors consist of arrays of detectors specially arranged to enhance precision, capabilities, and field of view (FOV). Sensor arrays can have multiple functionalities such as the simultaneous detection of position and motion. We use a linear sensor model and develop an optimization method to design an array of photodiodes. Our objective function minimizes bias and variance estimations. We introduce a maximum likelihood technique to approximate and determine the bias caused by measurement errors, and verify our theory by statistically complete simulations. We apply our theory to design an optimal sun sensor. The sensor has a predefined conical FOV, and its accuracy is controlled by a...
Simultaneous Navigation and Attitude Determination of a Reentry Head Using Magnetometer, Sun Sensor, Star Tracker, INS and Unscented Kalman Filter
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor)
Abstract
Control and guidance of a vehicle is vital for it to do its mission correctly. Guidance system and decisional algorithms used in it need exact information of instantaneous position, velocity, and attitude of the guided vehicle to determine and issue proper guiding commands.
Estimation algorithms and navigation sensors are two necessary tools for navigation. In the first section of present study, the reentry head equations of motion are derived and a 6-DOF simulation is done for it. In the second section, measurements of sensors will be simulated using results of the first section and existing reference models for sun position vector and earth magnetic field. The third section appertains...
Estimation algorithms and navigation sensors are two necessary tools for navigation. In the first section of present study, the reentry head equations of motion are derived and a 6-DOF simulation is done for it. In the second section, measurements of sensors will be simulated using results of the first section and existing reference models for sun position vector and earth magnetic field. The third section appertains...
Fabrication, characterization, and error mitigation of non-flat sun sensor
, Article Sensors and Actuators, A: Physical ; Volume 261 , 2017 , Pages 243-251 ; 09244247 (ISSN) ; Durali, M ; Rashidian, B ; Jalali, M. A ; Sharif University of Technology
Abstract
We report the design, fabrication and error analysis of a sun sensor array composed of six photodiodes. The sensor estimates the direction of the sun using a linear least squares method. The performance of the sensor is deteriorated by three major sources: fabrication errors, scattered environmental light, and inexact modeling of photodiodes. Using a calibration procedure and modeling the uniform component of the environmental light, we mitigate the first two errors and significantly reduce root mean squared error from 2.63° to 0.83°. For a Field of View (FOV) of 110°, the maximum estimation error also drops from 3.8° to 1.6°. Through exact mathematical modeling of photodiodes, we...
Optimal design and simulation of sensor arrays for solar motion estimation
, Article IEEE Sensors Journal ; Volume 17, Issue 6 , 2017 , Pages 1673-1680 ; 1530437X (ISSN) ; Durali, M ; Jalali, M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Modern sensors consist of arrays of detectors specially arranged to enhance precision, capabilities, and field of view (FOV). Sensor arrays can have multiple functionalities, such as the simultaneous detection of position and motion. We use a linear sensor model and develop an optimization method to design an array of photodiodes. Our objective function minimizes bias and variance estimations. We introduce a maximum likelihood technique to approximate and determine the bias caused by measurement errors, and verify our theory by statistically complete simulations. We apply our theory to design an optimal sun sensor. The sensor has a predefined conical FOV, and its accuracy is controlled by a...
Attitude estimation and control based on modified unscented Kalman filter for gyro-less satellite with faulty sensors
, Article Acta Astronautica ; Volume 191 , 2022 , Pages 134-147 ; 00945765 (ISSN) ; Mehrjardi, M. F ; Hajkarim, M. H ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
A modified unscented Kalman filter is presented to estimate the quaternion parameters as well as the angular velocities of a rigid gyro-less satellite under faulty sensor conditions. The task is carried out using the Sun sensor and magnetometers as attitude sensors with bounded noise and unknown fault(s). Following the presentation of the satellite attitude dynamics and filtering formulations, a new fault detection and isolation algorithm is proposed. The latter is based on a modified unscented Kalman filter structure for improved fault detection, sensor isolation, and attitude control (AC). A Backtracking Search Algorithm (BSA) is also used to design and optimize the PID controller gains,...
Concurrent orbit and attitude estimation using minimum sigma point unscented Kalman filter
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Vol. 228, issue. 6 , 2014 , p. 801-819 ; Pourtakdoust, S. H ; Sharif University of Technology
Abstract
Concurrent orbit and attitude determination (COAD) plays a key role in reducing the cost of navigation and control subsystem for small satellites. This article is devoted to the problem of the COAD of satellites. A measurement package consisting of three axis magnetometer (TAM) and a sun sensor is shown to be sufficient to estimate the attitude and orbit information. To this end, an autonomous gyro-less COAD algorithm is proposed and implemented through the centralized data fusion of the TAM and the sun sensor. The set of nonlinear-coupled roto-translation dynamics of the satellite is used with a modified unscented Kalman filter (MUKF) to estimate the full satellite states. The MUKF is...
On deterministic approaches to attitude determination with magnometer in eclipse
, Article 2010 Chinese Control and Decision Conference, CCDC 2010, 26 May 2010 through 28 May 2010, Xuzhou ; 2010 , Pages 3754-3759 ; 9781424451821 (ISBN) ; Bustan, D ; Sharif University of Technology
2010
Abstract
A gyroless deterministic attitude determination algorithm based on simulation of sun in eclipse is stated in this paper and has been compared to stochastic filters like extended Kalman filter and unscented Kalman filter. Attitude determination with low cost sensors such as magnometer and sun sensor results in usage of recursive algorithms such as Kalman filter which has the probability of divergence, but with deterministic point to point algorithm such as the one introduced in this paper we can be sure to have an attitude determination with a fixed maximum error. Proposed method has been compared with Extended Kalman Filter and Unscented Kalman filter due to its modeling error, robustness...
Attitude and deformation coupled estimation of flexible satellite using low-cost sensors
, Article Advances in Space Research ; Volume 69, Issue 1 , 2022 , Pages 677-689 ; 02731177 (ISSN) ; Assadian, N ; Varatharajoo, R ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Solar panel flexibility plays an important role in the attitude control of satellites. Therefore, traditionally the deformations of flexible solar panels are measured with a series of sensors along the panels itself. This paper presents a novel maiden attempt to simultaneously estimate the attitude and deformation of a flexible satellite using only 2 low-cost attitude sensors namely the sun sensor and magnetometer measurements. The flexible satellite is considered as a central rigid body with two attached flexible panels in order to derive the governing dynamic equations based on the Lagrange's equation. Both Extended Kalman filter (EKF) and Unscented Kalman Filter (UKF) are employed for the...