Abstract
The method is described in the article and an algorithm for the synthesis of the optimal control law for the reorientation of the nanosatellite using the procedure of analytical construction ...of optimal regulators is proposed. The algorithm provides a search of control for reorienting the nanosatellite along a phase trajectory close to the nominal one, subject to restrictions on the magnitude of the control torque. The nominal trajectory is divided into local sections, on each of which the required control is calculated.
Abstract
Nanosatellites have serious limitations on the onboard energy. Therefore, it is necessary to find a method of constructing a nominal reorientation trajectory that will optimally use the ...resources available onboard. In this paper the process of constructing of a nominal reorientation trajectory in the plane of nanosatellite orbit is considered. The problem of constructing a nominal reorientation trajectory was solved using the inverse dynamic problem method and Pontryagin maximum principle. A comparison of the results obtained using these two methods was made. As a result, it was noted that the solution obtained by the inverse dynamic problem method is close to the solution obtained using the Pontryagin maximum principle. This allows us to speak about the optimality of the inverse dynamics problem method.
The paper describes the measuring aids (magnetometers and light sensors) and attitude determination algorithms of SamSat-ION nanosatellite. The Kalman filter based on magnetometer measurements only ...is used as a basic algorithm, and the auxiliary QUEST algorithm provides a priori estimation of the quaternion input to the Kalman filter. The two-step algorithm simulation has been performed, and its efficiency has been verified.
The paper proposes an approach of the nanosatellite attitude determination problem solution using elements of artificial intelligence technology. This approach consists in the reconfiguration of the ...algorithms of the nanosatellite attitude determination problem solution based on the knowledge database that can be enriched to ensure the robustness of the feedback loop (the nanosatellite attitude determination using different combinations of different types of measurement information by various algorithms). This research results are presented in relation to the nanosatellite of the SamSat family: values of measurement significance coefficients are chosen; then generalized algorithm significance coefficients are calculated for various combinations of operable measuring means using chosen coefficients.
By the nanosatellite angular motion control in this research is meant terminal control based on inverse dynamics problem solution using the Bellman's optimality principle. The impact of the error of ...the nanosatellite design and dynamic performances, which are torques of inertia, attitude angles and angular rates, on the quality of angular motion control processes (i.e. on the accuracy of its reorientation), is investigated. The results of numerical simulation are given through the example of the nanosatellite of the SamSat family.
The paper summarizes the results of the research on angular motion dynamics carried out by the team of the authors and some problems of attitude control of nanosatellites (NS). The features of ...CubeSat NS passive motion dynamics are described. Conditions for the possible emergence of resonance modes are studied and discussed. Recommendations are given allowing the requirements for mass-inertia characteristics and initial conditions of NS motion to be formulated at the design stage, aimed at the NS stable motion with regard to the required equilibrium position for a wide range of orbital altitudes. Algorithms for reorientation and stabilization of NS motion are proposed based on the solution of the inverse problem of dynamics and selection of optimal nominal attitude control programs. The results of this work are implemented in practice and may be useful to the developers of small spacecraft.
The problem of reconstructing a spacecraft’s (SC’s) attitude motion using measurements of a current from solar panels with the use of the differential evolution algorithm is considered; in this case ...the model of measurements takes into account the Earth-reflected light flux. The possibility of using the differential evolution algorithm and the model of measurements in the problem of the attitude motion reconstruction is substantiated by the example of the Aist SC. The application of this algorithm considerably simplifies the traditional technique for reconstructing the attitude motion.
The paper shows the possibility of using navigation user equipment in the task of determining the dynamics of spacecraft rotational motion. An approach is proposed that makes it possible to estimate ...the parameters of the rotational motion of a spacecraft by analyzing the geometric visibility of navigational spacecraft of global navigation satellite systems. The proposed approach consists in approximation of the accumulated information on the position of the spacecraft longitudinal axis using the angular motion model and the measurement model. The approximation is made on the basis of minimizing the sum of squared deviations between the calculated coordinates of the vector of the longitudinal axis and their simulated values. The minimization procedure is based on the algorithm of differential evolution. The proposed approach allows us to estimate the angular velocity of the nanosatellite with an accuracy of at least 0.3 deg/s and orientation angles with an accuracy of at least 15 degrees.
The nanosatellite reorientation maneuver is one of the important elements of achieving the mission goal if it is required to ensure the transfer of the nanosatellite axes from the initial to the ...final attitude. This maneuver is used in the process of directing the sensitive axes of the onboard equipment of a nanosatellite according to a predetermined program. One of the features of the angular motion of a nanosatellite is that the control torque value is close to external one. The paper studies nanosatellite optimal reorientation maneuver trajectory, considering external torques under control torque constrains. We based the optimization procedure on the differential evolution algorithm. We studied the most effective structure of the control program. It was presented by a set of functional series: power, trigonometric, even and odd Fourier series and Schlömilch series. The paper proposes the localization approach for initialization of the differential evolution algorithm. Furthermore, the algorithm for finding the desired open-loop control program is suggested. We compared the most efficient structure of the control program with the results obtained by the inverse dynamics method and examined stability of the obtained solution. In addition, it is shown that the proposed approach can be extended to a larger spacecraft. We verify our approach by the comparison with the approach based on the use of the Pontryagin maximum principle.
Algorithms for determining the attitude and angular rate damping of the SamSat-218D nanosatellite developed at Samara State Aerospace University are described in the paper. The date of the ...prospective launching of the satellite into the Earth orbit from Vostochniy spaceport is April, 2016. A triaxial magnetometer and luminance sensors are used as sources of information in the orientation system. Three magnetic coils serve as actuators providing the angular rate damping onboard the nanosatellite. A known method of vector coordination with the original criterion of preliminary measurement rejection is used as the orientation determination algorithm since the vector coordination method is very sensitive to measurement errors. The traditional B-dot algorithm is used as the damping algorithm. The influence of the initial angular rates on the magnetic moment coefficient in the B-dot control algorithm is studied. Since the continuous mode of operation of magnetic coils on board the nanosatellite is unpractical due to the necessity of measuring variations in the Earth magnetic field intensity vector the damping process is analyzed in the discrete mode of operation at different values of angular rates of nanosatelite separation. The comparison of the algorithm processing speed in the continuous and discrete operating modes at various initial angular rates of separation is given.
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