Multibody dynamic simulation of the next generation space telescope using finite elements and fuzzy sets (original) (raw)
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Application of fuzzy sets to transient analysis of space structures
Finite Elements in Analysis and Design, 1998
An application of fuzzy sets, in conjunction with finite elements, to the transient analysis of a precision-deployable space structure is presented. The structural members are modeled by using beam finite elements, and the structure's latch joint is modeled by using a spring-damper-Coulomb friction element. Two types of transient response simulations are performed: slow transient load-deflection response and transient impulse response. The first simulation is used to evaluate the stiffness and buckling loads at the structure's tip. The second simulation is used to evaluate the structure's natural frequencies, mode shapes and the precision of the final shape. For each simulation the possibility distributions of various response quantities are obtained. Fuzzy sets are used to represent three beam properties, namely: damping coefficient, bending stiffness, and axial stiffness; as well as two joint parameters: Coulomb friction force and damping coefficient. Fuzzy set techniques provide an insight into the range of possible responses associated with the combined selected variations in the system parameters.
The Proceedings of the Asian Conference on Multibody Dynamics, 2010
Lightweight deployable structures are required in many space missions. The development and the test of prototypes in space is prohibitively expensive and ground testing is a poor representation of the real behavior of this type of structure in space. In addition, shocks that can influence the dimensioning of the mechanisms usually occur during the deployment, in particular when the system is released or locked. For those reasons, the numerical analysis of deployable space structures is becoming absolutely necessary and a software tool supporting this activity has thus a clear interest in space industry. The goal of the DESCAS (DEployment Simulation of Complex Antenna Structure) ESA project was to improve the capabilities of the SAMCEF Mecano commercial software in order to demonstrate its ability to provide accurate solutions for those mathematically stiff problems. The main results of this project will be presented in the proposed paper, which will be organized as follows: First a brief description of the software will highlight the capability of this implicit non-linear finite element solver to model efficiently flexible deployable systems. Secondly, a comparison study of time integrators will be presented emphasizing their capability to catch end-of-deployment shocks. Finally, requirements on the mathematical models will be defined for the target applications. Two industrial benchmarks proposed by ESA have been treated during the project and will be detailed in the paper, demonstrating the capabilities of the Software. The first one is a Large Deployable Reflector Antenna developed by Thales Alenia Space and the Russian-Georgian subcontractor NPO-EGS. The software selected for deployment analysis was Samcef Mecano. Due to severe convergence problems, this numerical model built initially in the late nineties could never be completely simulated before this project. Latest simulations could be completed showing all transient effects associated to locking and stiffening systems. More over, we could demonstrate the robustness of the model and its weak sensitivity to all numerical parameters. This model is able to represent on-ground test, in-orbit deployment, and to investigate several alternatives for the actuation used to drive the system.
Infotech@Aerospace 2011, 2011
The use of computer models to predict the dynamic behavior of the Space Vehicles is used to understand the natural frequencies, dynamic system responses of complex rigid-flexible multibody system such as the International Space Station (ISS). One of the major problems in assembling the ISS is simulating dynamics and control analysis in orbit. This problem is a challenge that confronts the ISS program and thus computer modeling and simulation becomes a crucial tool for the success of space missions since the Station is being built in Space instead of a lab on earth where dynamic tests could be run. Each new mission of the Space Shuttle is designed to build the ISS and each new mission presents new challenges because the structure changes and thus the model has to change. In this paper, the authors present a model of the ISS assembled after the Space Shuttle STS-133 mission. The objective is that this model can be used to understand the modes of vibration and to design a control system capable of controlling ISS attitude. Once the computer model was assembled in a way that resembles the actual ISS assembly, model data were compared with NASA's data. This paper proposes an alternative method for producing a new generation of three dimensional simplified computer models while still preserving significant dynamics information. In order to achieve this, the authors used components created in three dimensions via solid modeling and then transformed them into time dependent dynamic finite element models. The idea here is to have a model consisting of rigid-flexible multi-body systems, as this is what ISS is. Such process and results are presented here step by step using a technique that mixes solid modeling and dynamic finite element modeling. Software packages such as SOLIDWORKS, MSC VISUAL NASTRAN4D, MATLAB and SIMULINK were incorporated in the process. The computer model results can provide aerospace engineers with new alternative methods to perform dynamic analysis to study forces, deflections, vibrations, and position of spacecraft. The alternative method can provide aerospace engineers with new simplified methods to quickly get a handle of the forces, deflections, modes of vibration and prediction of dynamic loads during space maneuvers and ultimately crucial information to be used in guidance and control.
Linear Dynamic Modeling of Spacecraft With Various Flexible Appendages
2008
We present here a method and some tools developed to build linear models of multi-body systems for space applications (typically satellites). The multi-body system is composed of a main body (hub) fitted with rigid and flexible appendages (solar panels, antennas, propellant tanks, ...etc). Each appendage can be connected to the hub by a cantilever joint or a pivot joint. More generally, our method can be applied to any open mechanical chain. In our approach, the rigid six degrees of freedom (d.o.f) (three translational and three rotational) are treated all together. That is very convenient to build linear models of complex multi-body systems. Then, the dynamics model used to design AOCS, i.e. the model between forces and torques (applied on the hub) and angular and linear position and velocity of the hub, can be derived very easily. This model can be interpreted using block diagram representation.
THE DYNAMICS OF SYSTEMS OF RIGID AND ELASTIC BODIES AS APPLIED TO SPACECRAFT
The basic results of the scientific research conducted at the S. P. Timoshenko Institute of Mechanics of the National Academy of Sciences of Ukraine (NASU) in a creative cooperation with the M. K. Yangel' SDO " Yuzhnoe " and the Institute of Technical Mechanics of NASU and the National Space Agency of Ukraine (NSAU) are generalized and systematized. The research addressed mathematical models and the dynamics of objects of space-rocket engineering such as controlled systems of rigid and elastic bodies, systems of rigid bodies of variable configuration, and systems of bodies with unilateral connections. The following information is detailed here: methods for creating spatial program motions of elastic space structures about the center of mass, methods and algorithms for mathematical simulation of the dynamics of reconfigurable spacecraft, unconventional concepts of simulating the state of weightlessness of a reconfiguring spacecraft under earth conditions on a special stand using suspension cables, different aspects of the dynamics of space cable systems, and other problems resolved within the framework of the subjects indicated. The current state of the theory of systems of rigid and deformable bodies [132, 152] is mainly determined by advances in the area of transformable space structures and robotics. Methods for constructing mathematical models of systems of solids with the topology of a tree and a closed multilink structure with up to six degrees of freedom under holonomic and nonholonomic constraints were developed in sufficient detail. The dynamics of systems of rigid and elastic bodies was extensively studied both in robotics, where individual links of the system should be considered with allowance for their deformability, and in space engineering, where spacecraft contain some elements whose deformation cannot be neglected too in solving practical problems. Modern spacecraft are, as a rule, complex structures consisting of many elements. Previously compactly packaged, such a system, once placed in an orbit, changes significantly its own configuration, which is determined by the functionality of the spacecraft. For example, solar arrays are deployed in a developed spatial structure in order to utilize maximally the radiation energy of the Sun. The bar of the gravitational stabilizer and rod antennas change from rolled ribbons into long-length elastic rods with an open cross section. Trusses replacing the bars and created from structures with a closed cross section can also carry a gravitational stabilizer, devices, etc. Large spatial antenna structures are also characteristic of the modern spacecraft. A special place in space engineering is occupied by cable systems, which can be created in the orbit from isolated bodies connected with each other and spaced several kilometers apart. Despite the great advances in the dynamics of systems of bodies, the processes described may not always be investigated within the framework of the classical dynamics of systems of rigid and even elastic bodies. The gravitational-stabilizer bar, which is a component of a reconfigurable spacecraft and is formed in the orbit from a prestressed ribbon, and the synthesized truss do not fit in the classical mathematical models of the dynamics of systems of bodies even with allowance for structural flexibility. The selection of a design model is determined in each specific case by the kinematic configuration of the system, the mechanical properties of its parts, the type of drives, and the desired accuracy of the calculations.
2000
We present here a method and some tools developed to build linear models of multi-body systems for space applications (typically satellites). The multi-body system is composed of a main body (hub) fitted with rigid and flexible appendages (solar panels, antennas, propellant tanks, ...etc) and on-board angular momentums (flywheels, control moment gyros). Each appendage can be connected to the hub by a cantilever joint or a pivot joint. More generally, our method can be applied to any open mechanical chain. In our approach, the rigid six degrees of freedom (d.o.f) (three translational and three rotational) are treated all together. That is very convenient to build linear models of complex multi-body systems. Then, the dynamics model used to design AOCS, i.e. the model between forces and torques (applied on the hub) and angular and linear position and velocity of the hub, can be derived very easily. This model can be interpreted using block diagram representation.
Importance of structural damping in the dynamic analysis of compliant deployable structures
Acta Astronautica, 2015
Compliant mechanisms such as tape springs are often used on satellites to deploy appendices, e.g. solar panels, antennas, telescopes and solar sails. Their main advantage comes from the fact that their motion results from the elastic deformation of structural components and the absence of actuators or external energy sources. The mechanical behaviour of a tape spring is intrinsically complex and nonlinear involving buckling, hysteresis and self-locking phenomena. In the majority of the previous works, dynamic simulations were performed without any physical representation of the structural damping. These simulations could be successfully achieved because of the presence of numerical damping in the transient solver. However, in this case, the dynamic response turns out to be quite sensitive to the amount of numerical dissipation, so that the predictive capabilities of the model are questionable. In this work based on numerical case studies, we show that the dynamic simulation of a tape spring can be made less sensitive to numerical parameters when the structural dissipation is taken into account.
Linear Dynamic Modeling of Satellites with Various Flexible Appendages
A method and some tools developed to build linear models of multi-body systems for space applications (typically satellites) are presented. The multi-body system is composed of a main body (hub) fitted with rigid and flexible appendages (solar panels, antennas, propellant tanks, ...etc). Each appendage can be connected to the hub by a cantilever joint or a pivot joint. More generally, our method can be applied to any open mechanical chain. In our approach, the rigid six degrees of freedom (d.o.f) (three translational and three rotational) can be treated all together, and that is very convenient to build linear models of complex multi-body systems. Each added pivot joint, adds a new degree of freedom to the six rigid d.o.fs of the system. The satellite equations of motion which relate the forces and torques applied on the main satellite hub to the angular and linear position and velocity of the hub are found. A Matlab toolbox is developed to calculate this dynamic model, hence making...
Uncertainty impact on micro-vibration control of an orbiting large adaptive space structure
EasyChair Preprints, 2018
Large deployable structures are required for the advancement of modern space activities. A wide variety of EO (Earth Observation) spacecrafts is actually using and will profit by large antenna systems supported by truss-like structures with low mass and stiffness. In this perspective, the control design strategy calls for a system with distributed active control of the flexible appendage, ensuring acceptable deformations. A net of smart actuators can be embedded in the supporting frame elements to make the structure adaptive itself and to limit undesired elastic vibrations. In the present paper, the supporting structure of a very large mesh reflector is described. A methodology based on a classical Lagrangian approach combined with a FEM formulation has been adopted to assemble the system and validated by comparing it with commercial codes. An optimization procedure has been carried out to evaluate the damping efficacy of the actuators. After having assessed the best authority of th...