Qiang Tian

An Efficient Hybrid Method for Multibody Dynamics Simulation Based on Absolute Nodal Coordinate Formulation

This paper presents an efficient hybrid method for dynamic analysis of a flexible multibody system. This hybrid method is the combination of a penalty and augmented Lagrangian formulation with the mass-orthogonal projections method based on the absolute nodal coordinate formulation (ANCF). The characteristic of the ANCF that the mass matrix is constant and both Coriolis and centrifugal terms vanish in the equations of motion make the proposed method computationally efficient. Within the proposed method, no additional unknowns, such as the Lagrange multipliers in the Newmark method, are introduced, and the number of equations does not depend on the number of constraint conditions. Furthermore, conventional integration stabilization methods, such as Baumgartes method. are unnecessary. Therefore, the proposed method is particularly suitable for systems with redundant constraints, singular configurations, or topology changes. Comparing results from different methods in terms of efficiency and accuracy has shown that the proposed hybrid method is efficient and has good convergence characteristics for both stiff and flexible multibody systems.

Dynamics of a Deployable Mesh Reflector of Satellite Antenna: Form-Finding and Modal Analysis

Mesh reflectors with large apertures have been used in many communication satellites. The performance of antenna reflectors crucially depends on the faceting error of the reflective surface, which is approximated by using meshes. The force density method (FDM) has been widely used for the form-finding analysis of mesh reflectors. However, after performing form-finding of some meshes, the effective reflective area will decrease. In addition, the form-finding of the auxiliary mesh has received little attention, and it cannot be achieved by using the FDM. Thus, in this study, an effective form-finding methodology that combines the iterative FDM and the minimum norm method (MNM) is proposed. To consider the flexibility of the reflector ring truss, a static analysis of the ring truss under the tension force actions is also performed in the form-finding processes. The reflector flexible parts are described by the absolute nodal coordinate formulation (ANCF). Finally, the form-finding analysis of the reflector with the standard configuration, the central hub configuration, and the circular configuration is performed to validate the proposed methodology. The influence of the mesh tension force on the reflector natural frequencies is also studied. After performing the form-finding analysis, the initial configuration of the reflector with tensioned meshes for the deployment dynamics study can be determined. Based on this paper, the deployment dynamics of a complex AstroMesh reflector will be studied in a successive paper “Dynamics of a Deployable Mesh Reflector of Satellite Antenna: Parallel Computation and Deployment Simulation.”

Three-Dimensional Topology Optimization of a Flexible Multibody System via Moving Morphable Components

In this work, a novel three-dimensional (3D) topology optimization methodology for a flexible MBS undergoing both large overall motion and large deformation is proposed. Firstly, the flexible MBS of concern is accurately modeled via the 3D solid brick element of the absolute nodal coordinate formulation (ANCF), which utilizes positions of nodes and slopes as sets of generalized nodal coordinates. Secondly, to deal with the dynamic characteristics in the optimization process, the equivalent static load method is employed to transform the dynamic topology optimization problem into a static one. Last but not least, in order to reduce the computation time, the newly-developed moving morphable components (MMC) based topology optimization method is reevaluated to optimize the 3D flexible MBS. The MMC based framework incorporates more geometrical and mechanical information into the topology optimization directly and can optimize large-scale flexible MBS with high efficiency. Two numerical examples are presented to validate the accuracy of the solid element of ANCF and the effectiveness of the proposed optimization methodology, respectively.

Dynamics of Space Deployable Structures

The space industry is eager to have the advanced technology of large space structures composed of trusses, cables and meshes. These space structures will deploy on orbit for different space missions. The important scientific basis of the technology is the nonlinear dynamic modeling, analysis and control of those space structures during their deployment and service. In this study, many space deployable structures (such as satellites antenna and spinning solar sail) are described by using the absolute nodal coordinate formulation (ANCF), and the huge set of equations of motion are solve by high efficient parallel generalized-alpha method. Some numerical results are also validated by experiment results.Copyright