Littérature scientifique sur le sujet « Sloshing compensation »

Quantifying free-form surfaces using differential confocal microscopy can be challenging, as it requires balancing accuracy and efficiency. When the axial scanning mechanism involves sloshing and the measured surface has a finite slope, traditional linear fitting can introduce significant errors. This study introduces a compensation strategy based on Pearson’s correlation coefficient to effectively reduce measurement errors. Additionally, a fast-matching algorithm based on peak clustering was proposed to meet real-time requirements for non-contact probes. To validate the effectiveness of the compensation strategy and matching algorithm, detailed simulations and physical experiments were conducted. The results showed that for a numerical aperture of 0.4 and a depth of slope < 12°, the measurement error was <10 nm, improving the speed of the traditional algorithm system by 83.37%. Furthermore, repeatability and anti-disturbance experiments demonstrated that the proposed compensation strategy is simple, efficient, and robust. Overall, the proposed method has significant potential for application in the realization of high-speed measurements of free-form surfaces.

Structure of geometrical nonlinearities in mathematical model of liquid sloshing in tanks of non-cylindrical shape is under consideration. In contrast to the case of cylindrical reservoir, some new types of nonlinearities occur in mathematical statement of the problem. They are connected with four main reasons. First, they are determined by new normal modes, which correspond to non-cylindrical shape of the tank and take into account some nonlinear properties of the problem (for example, they follow tank walls above level of a free surface). Second, determination of the potential energy of the liquid includes tanks geometry in close vicinity of cross-section of undisturbed free surface of the liquid and tank walls. Third type of manifestation of geometrical nonlinearities is connected with compensation of elevation of liquid level due to non-cylindrical type of tank shape for providing law of mass conservation. The fourth type of nonlinearities is connected with simultaneous manifestation of physical and geometrical nonlinearities. Investigation showed that mostly manifestation of nonlinear properties of liquid sloshing, connected with geometrical nature, is predetermined by inclination and curvature of tank walls in close vicinity of contact of undisturbed liquid with tank walls. We illustrated some general properties of geometrical nonlinearities by the example of three cases of tanks, namely, cylindrical, conic, and paraboloidal tank, which is selected such that its walls have the same inclination near free surface of the liquid as conic tank, but in this case curvature is manifested supplementary.

This paper aims to reach high-quality attitude control and large-amplitude slosh suppression when a typical liquid-filled spacecraft executes three-axial large-angle maneuvers, by applying a wave-based attitude controller (WBAC). First, the sloshing dynamics is modeled by using a spherical pendulum, whose motion is expressed by splitting its coordinates. Thus, the large-amplitude lateral sloshing and the rotary sloshing as well as the over-all rigid motion of a liquid with respect to the tank in spacecraft can be approximately described. Second, the dynamics equations of system in terms of hybrid coordinate for the liquid-filled spacecraft are derived via the Lagrangian formulation. Third, an improved WBAC for three-axial large-angle maneuvers of in-orbit liquid-filled spacecraft is designed by adding a derivative control law and a gravity-gradient-torque compensation law to a wave-based control law. Simulations of three-axial large-angle maneuver demonstrate good performance of the WBAC in shortening completion time of attitude maneuvering, suppressing the jitter in the angular velocity of spacecraft, and accelerating the large-amplitude slosh suppression, simultaneously. The results indicate the potential applications of the proposed WBAC in the large-angle attitude maneuvering of liquid-filled spacecraft when there exists large-amplitude liquid slosh.

Abstract The continuous, moored observation revealed significant variability in the strength of the Atlantic Meridional Overturning Circulation (AMOC). Cause of such AMOC variability is an extensively studied subject. This study focuses on the short-term variability, which ranges up to seasonal and interannual timescales. A mechanism is proposed from the perspective of ocean water redistribution by layers. By offering explanations for four phenomena of AMOC variability in the subtropical and tropical oceans (seasonality, meridional coherence, layered-transport compensation as observed at 26.5°N, and the 2009/2010 downturn occurred at 26.5°N), this mechanism suggests that the short-term AMOC variabilities in the entire subtropical and tropical regions are governed by a basin-wide adiabatic water redistribution process or the so-called sloshing dynamics rather than diapycnal processes.

Sloshing of liquid in a tank is critical in several areas, including launch vehicles carrying liquid fuel, satellites, industrial packaging of liquids, systems handling molten metal, and so on. Hence modeling, characterization, and control of nonlinear slosh phenomena are important in these applications. To study slosh dynamics, develop useful identification schemes, and design and verify slosh control algorithms, a new 2DOF actuation slosh rig is reported in this paper considering the fact that most of the times these tanks are subjected to linear as well as pitching excitation/control inputs. The paper discusses mechatronic design and several advantages that the new design offers. A slosh phenomenon of beating observed when both lateral and pitching excitations are provided is simulated using a model based on pendulum approximation to slosh and is further verified in experiments. The results confirm that the effects of both excitations together can be detrimental against separate excitations of the same amplitude. Moreover, slosh compensation in open loop is demonstrated by giving excitation in pitching and developing a compensatory input in the lateral direction. Furthermore, active slosh control strategy is developed and its effectiveness is demonstrated with control in translation and disturbance in pitching. Thus the proposed rig is an ideal tool for the study, identification, and control development of slosh in the presence of two excitations/inputs.

Dans un scénario de satellites géostationnaires hautement autonomes, dotés de capacités d'auto-assemblage et d'auto-maintenance, les perturbations des bras manipulateurs couplées à la dynamique de ballotement du carburant représentent un risque significatif de dégradation des performances du système de contrôle d'attitude et d'orbite du satellite. Bien que des solutions passives existent pour amortir le ballotement du carburant et compenser les perturbations des bras manipulateurs, il manque une solution de contrôle actif unique capable de compenser ces perturbations tout en évitant de manière optimale la saturation des actionneurs. Cette lacune suscite un grand intérêt dans l'industrie spatiale en raison de ses implications potentielles dans la réduction du poids, des coûts et de la complexité de la fabrication.Cette étude explore l'intégration de techniques de contrôle robuste basées sur la synthèse $H_{infty}$ et de techniques de contrôle adaptatif par modèle de référence avec des schémas de reference governor. L'objectif est de proposer une solution de contrôle unique garantissant un contrôle précis de l'attitude du satellite en présence de perturbations non modélisées et de contraintes des actionneurs. Les avancées théoriques de cette recherche s'étendent également à des scénarios tels que la gestion des défaillances de propulseur dans les quadricoptères sous contraintes d'état et d'entrée, ainsi qu'à l'optimisation de la conception des modes de guidage pour des missions satellitaires telles que la mission Microcarb du CNES
In a scenario of highly autonomous geostationary satellites, with self-assembly and self-maintenance capabilities, manipulator arms perturbations coupled with fuel slosh dynamics represents a significant risk of performance degradation for the satellite attitude and orbit control system. While passive fuel slosh damping solutions and manipulator arm disturbances compensators exist by their own, a unique active control solution capable of rejecting the perturbations while optimally preventing the actuators saturation is lacking and of great interest in the space industry for weight, cost and complexity of manufacturing reduction. This study explores the integration of $H_{infty}$-based robust control and model reference adaptive control techniques with reference governor schemes. The objective is to propose a unique control solution to guarantee precise satellite attitude control in the presence of unmodeled perturbations and actuator constraints. The theoretical advancements from this research also extend to scenarios such as handling propeller failures in quadrotors under state and input constraints and optimizing the design of the guidance modes for satellite missions like the CNES Microcarb mission

The Copernicus Imaging Microwave Radiometer (CIMR) is a European Earth Observation mission consisting of 2 satellites (with an option of the extension to the third one). It will provide high resolution global monitoring of the Earth surface emissions across various frequency bands, in particular floating sea ice parameters. The 3-axis stabilized spacecraft(s) will operate in a sun synchronous orbit with 817 km altitude. The instrument features a deployable mesh reflector with the diameter of 8 meters and its feed cluster, which rotates at 8 rpm to produce a 1900km wide ground swath. The CIMR mission is currently in the C/D development phase and is being developed by a European space consortium with Thales-Alenia-Space Rome as a prime contractor. The unique configuration consisting of the 3-axis stabilized platform and a spinning instrument poses various technical challenges for the AOCS design. The design drivers have been identified as follows: •Provision of onboard angular momentum management to accommodate for large rotating instrument. •Sophisticated spacecraft dynamic phenomena caused by a)flexibility of the deployable rotating antenna b)static and dynamic unbalance of the rotating instrument c)fuel sloshing •Capability to perform collision avoidance maneuvers throughout nominal operation and controlled reentry at the end of mission lifetime •Managing the onboard Fault Detection, Isolation and Recovery (FDIR) with the objective of maximizing the scientific operation. This paper gives an overview of the CIMR AOCS design, in particular •Description of the avionics hardware setup •Basic AOCS modes and transitions •FDIR concept description Besides the general overview few critical design solutions developed for CIMR will be presented in more detail: •Static and dynamic unbalance on-board estimation using gyro rate measurements and compensation through active balancing system •Preliminary design of onboard control laws that meet the performance requirements and guarantee the overall systems stability and robustness in presence of undesired coupling caused by internal disturbances, flexible dynamics, and time-varying uncertainties. •Controlled reentry manoeuvre through multiple apogee thruster firings in presence of critical drag at perigee passages.