LEVERAGING SYNERGETIC INFORMATION RESOURCES FOR ANGULAR MOTION CONTROL OF UNMANNED SPACECRAFT

2021 ◽  
pp. 127-141
Author(s):  
Vladimir S. KOVTUN ◽  
Aleksandr N. PAVLOV ◽  
Boris V. SOKOLOV ◽  
Dmitry A. PAVLOV ◽  
Valentin N. VOROTYAGIN
Keyword(s):  
Motion Control ◽  
Transitive Closure ◽  
Angular Rate ◽  
Center Of Mass ◽  
Control Process ◽  
Measured Data ◽  
Binary Relations ◽  
Spacecraft Control ◽  
Rate Vector ◽  
Unmanned Spacecraft

A key condition for accomplishing a mission of an unmanned spacecraft consists in providing it with resources. Resources can be replenished through synergetic observations of processes in cases where measured data are partially or fully missing or lacking for some of the controlled objects by means of measuring parameters of the processes characterizing the operation of other controlled objects. As an example, the paper discusses provisioning of resources for the process of controlling the motion about the center of mass by means of synergetic observations in cases where no inertial instrument was available for measuring the angular rate vector in the system controlling the motion of the geostationary communications satellite Yamal-200. Specifically, the observation is based on the operation of transitive closure of the binary relation defined on the base set of processes in the onboard systems and ground assets for radio interactions with the onboard systems of the unmanned spacecraft. Key words: unmanned spacecraft, control process, measuring data, binary relations, transitive closure, provision of resources.

Leveraging synergetic information resources for angular motion control of unmanned spacecraft

2021 ◽  
pp. 127-141
Author(s):  
Vladimir S. KOVTUN ◽  
Aleksandr N. PAVLOV ◽  
Boris V. SOKOLOV ◽  
Dmitry A. PAVLOV ◽  
Valentin N. VOROTYAGIN
Keyword(s):  
Motion Control ◽  
Transitive Closure ◽  
Angular Rate ◽  
Center Of Mass ◽  
Control Process ◽  
Measured Data ◽  
Binary Relations ◽  
Spacecraft Control ◽  
Rate Vector ◽  
Unmanned Spacecraft

A key condition for accomplishing a mission of an unmanned spacecraft consists in providing it with resources. Resources can be replenished through synergetic observations of processes in cases where measured data are partially or fully missing or lacking for some of the controlled objects by means of measuring parameters of the processes characterizing the operation of other controlled objects. As an example, the paper discusses provisioning of resources for the process of controlling the motion about the center of mass by means of synergetic observations in cases where no inertial instrument was available for measuring the angular rate vector in the system controlling the motion of the geostationary communications satellite Yamal-200. Specifically, the observation is based on the operation of transitive closure of the binary relation defined on the base set of processes in the onboard systems and ground assets for radio interactions with the onboard systems of the unmanned spacecraft. Key words: unmanned spacecraft, control process, measuring data, binary relations, transitive closure, provision of resources.

scholarly journals Dynamic analysis and motion control of spinning tether system during its Earth to Mars flight

2021 ◽  
Vol 5 (1) ◽  
pp. 27-34
Author(s):  
H. Lu ◽  
C. Wang ◽  
Yu. M. Zabolotnov
Keyword(s):  
Dynamic Analysis ◽  
Motion Control ◽  
Center Of Mass ◽  
Angular Speed ◽  
Artificial Gravity ◽  
Jet Engines ◽  
Interplanetary Trajectory ◽  
Material Points ◽  
Spinning Tether ◽  
Interplanetary Mission

The dynamic analysis and motion control of a spinning tether system for an interplanetary mission to Mars is considered. The space system consists of two spacecraft connected by a tether with thrusts to control its movement. The movements of the tether system in the sphere of action of the Earth, on the interplanetary trajectory and in the sphere of action of Mars are consistently analyzed. In near-Earth orbit, the transfer of the system into rotation with the help of jet engines installed on the end spacecrafts is considered. The spin of the system is used to create artificial gravity during the interplanetary flight. The tether system spins in the plane perpendicular to the plane of the orbital motion of the center of mass of the system. To describe spatial motion of the system, a mathematical model is used, in which the tether is represented as a set of material points with viscoelastic unilateral mechanical connections. When calculating the movement of the system, an approach based on the method of spheres of action is used. Spacecrafts are considered as material points. The level of gravity and spin of tether system is controlled by thrusters. The structure of the controller for controlling the angular speed of rotation of the tether system is proposed. The simulation results are presented to confirm the effectiveness of the proposed control algorithm, which provides a given level of artificial gravity for th e interplanetary mission under consideration.

Efficient Modal Decomposition and Reconstruction of Riser Response due to VIV

2011 ◽  
Author(s):  
S. I. McNeill ◽  
P. Agarwal
Keyword(s):  
Fatigue Damage ◽  
Traveling Wave ◽  
Angular Rate ◽  
Normal Modes ◽  
Structural Response ◽  
Measured Data ◽  
Vibration Monitoring ◽  
Wave Number ◽  
Modal Decomposition ◽  
Basis Vectors

Vortex-Induced-Vibrations (VIV) due to ocean currents can consume a sizable portion of the allotted fatigue life of marine risers. Vibration monitoring and concurrent estimation of fatigue damage due to VIV can significantly enhance the safe and reliable operation of risers. To this end, riser response can be characterized by using sensors (e.g. accelerometers and/or angular rate sensors) to measure the motion of the riser at a few locations. Fatigue damage can be predicted along the entire length of riser from measured data using the method of modal decomposition and reconstruction. In this method the structural response of interest, such as stress and fatigue damage, is expressed by modal superposition, where the modal weights are estimated using measured data and analytical modeshapes. However the accuracy of this method declines as the sensor density (number of sensors per unit riser length) decreases, especially when the riser vibrates in high-order modes and exhibits traveling wave behavior. In this paper, an efficient frequency-domain methodology allowing for accurate reconstruction of the riser response along the entire riser using a limited number of sensors is proposed. We first identify the excited VIV modes (natural frequency and modeshape) using principal vectors of the cross spectral density. Modal decomposition and reconstruction is performed separately for each VIV band surrounding each excited mode. This allows us to use several (as many as the number of sensors) participating modes in each band, and thus improve the accuracy. Since the stress distribution is sensitive to the chosen set of participating modes, we optimize over several candidate sets, selecting the set of modes that result in the lowest prediction error. In order to improve the reconstruction of complex modes, particularly traveling waves, the modeshapes can be augmented with additional basis vectors. The additional basis vectors are obtained by shifting the phase of the normal modes by 90 degrees at every wave number using the Hilbert transform. Though developed in the context of VIV, the method can be used to estimate fatigue damage due to vibrations regardless of the excitation mechanism. The methodology is demonstrated using the NDP (Norwegian Deepwater Program) test data on a 38 meter long slender riser, using data from eight accelerometers. Results show that the proposed algorithm can reconstruct stresses and fatigue damage accurately along the length of the riser in the presence of traveling wave behavior using relatively few sensors.

scholarly journals Mapping and determining the center of mass of a rotating object using a moving observer

2018 ◽  
Vol 37 (1) ◽  
pp. 83-103 ◽  
Author(s):  
Timothy P Setterfield ◽  
David W Miller ◽  
John J Leonard ◽  
Alvar Saenz-Otero
Keyword(s):  
Angular Rate ◽  
Center Of Mass ◽  
Computational Cost ◽  
Target Object ◽  
Factor Graph ◽  
Visual Sensor ◽  
Fixed Frame ◽  
Computational Performance ◽  
Kinematic Factor ◽  
Graph Mapping

For certain applications, such as on-orbit inspection of orbital debris, defunct satellites, and natural objects, it is necessary to obtain a map of a rotating object from a moving observer, as well to estimate the object’s center of mass. This paper addresses these tasks using an observer that measures its own orientation, angular rate, and acceleration, and is equipped with a dense 3D visual sensor, such as a stereo camera or a light detection and ranging (LiDAR) sensor. The observer’s trajectory is estimated independently of the target object’s rotational motion. Pose-graph mapping is performed using visual odometry to estimate the observer’s trajectory in an arbitrary target-fixed frame. In addition to applying pose constraint factors between successive frames, loop closure is performed between temporally non-adjacent frames. A kinematic constraint on the target-fixed frame, resulting from the rigidity of the target object, is exploited to create a novel rotation kinematic factor. This factor connects a trajectory estimation factor graph with the mapping pose graph, and facilitates estimation of the target’s center of mass. Map creation is performed by transforming detected feature points into the target-fixed frame, centered at the estimated center of mass. Analysis of the algorithm’s computational performance reveals that its computational cost is negligible compared with that of the requisite image processing.

On transitive subrelations of binary relations

2011 ◽  
Vol 76 (4) ◽  
pp. 1429-1440 ◽  
Author(s):  
Christopher S. Hardin
Keyword(s):  
Binary Relation ◽  
Transitive Closure ◽  
Infinite Chain ◽  
Binary Relations ◽  
Transitive Relation

AbstractThe transitive closure of a binary relation R can be thought of as the best possible approximation of R “from above” by a transitive relation. We consider the question of approximating a relation from below by transitive relations. Our main result is that every thick relation (a relation whose complement contains no infinite chain) on a countable set has a transitive thick subrelation. This allows for a solution to a problem arising from previous work by the author and Alan Taylor. We also exhibit a thick relation on an uncountable set with no transitive thick subrelation.

Real-Time Riser Fatigue Monitoring Routine: Architecture, Data and Results

2013 ◽  
Author(s):  
Scot McNeill ◽  
Puneet Agarwal ◽  
Dan Kluk ◽  
Kenneth Bhalla ◽  
Tomokazu Saruhashi ◽  
...  
Keyword(s):  
Real Time ◽  
Fatigue Damage ◽  
Water Depth ◽  
Angular Rate ◽  
Measured Data ◽  
Automated System ◽  
Time Data ◽  
Joint Rotation ◽  
Computational Environment ◽  
Fatigue Monitoring

Recently, the Modal Decomposition and Reconstruction (MDR) algorithm was developed to accurately estimate fatigue damage in marine risers based on measured acceleration and angular rates at several locations. The greatest benefit for drilling risers can be derived by incorporating the method in an online, fully automated system. In this way, fatigue damage estimates are available to the crew on the rig in real-time for risk quantification and mitigation. To this end, the MDR routine was implemented for online assessment of fatigue damage along the entire riser from acceleration and angular rate measurements at typically 5–10 elevations. This paper discusses the architecture, highlights some measured data and provides results for modes, stress and fatigue damage rate for the Chikyu drilling vessel during two scientific drilling campaigns. These campaigns occurred at the Shimokita site (1180-meter water depth) and the Nankai trough site (1939-meter water depth). To the authors’ knowledge, real-time fatigue monitoring of the entire riser has not been accomplished previously. Robust incorporation of the MDR algorithm into an online computational environment is detailed, including incorporation of top tension and mud weight data from the rig, detection and removal of data errors, and streamlined flow of the data through the computational modules. Subsequently, it is shown by example how the measured accelerations and angular rates are used to determine excited modes, participating modes, stress distribution and fatigue damage along the entire Chikyu drilling riser in an online setting. The technology highlighted advances riser integrity management two steps forward by first using measured data at 5–10 locations and the MDR algorithm to reconstruct stress and fatigue damage along the entire riser, and secondly integrating this approach into a fully automated, real-time computational environment. As a result, drilling engineers are empowered with a tool that provides real-time data on the integrity of the drilling riser, enabling informed decisions to be made in adverse current or wave conditions. Measured data also serves as a benchmark for analytical model calibration activities, reducing conservatism in stress and fatigue in future deployments. Furthermore, cumulative fatigue damage can be tracked in each riser joint, enabling more effective joint rotation and inspection programs.

scholarly journals Influence of Satellite Motion Control System Parameters on Performance of Space Debris Capturing

Aerospace ◽  
2020 ◽  
Vol 7 (11) ◽  
pp. 160
Author(s):  
Mahdi Akhloumadi ◽  
Danil Ivanov
Keyword(s):  
Control System ◽  
Motion Control ◽  
Control Algorithm ◽  
Space Debris ◽  
Equations Of Motion ◽  
Center Of Mass ◽  
Attitude Motion ◽  
System Parameters ◽  
Thrust Vector ◽  
Rendezvous And Docking

Relative motion control problem for capturing the tumbling space debris object is considered. Onboard thrusters and reaction wheels are used as actuators. The nonlinear coupled relative translational and rotational equations of motion are derived. The SDRE-based control algorithm is applied to the problem. It is taken into account that the thrust vector has misalignment with satellite center of mass, and reaction wheels saturation affects the ability of the satellite to perform the docking maneuver to space debris. The acceptable range of a set of control system parameters for successful rendezvous and docking is studied using numerical simulations taking into account thruster discreteness, actuators constrains, and attitude motion of the tumbling space debris.

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