The Dynamics Algorithms for Real-Time Simulation (DARTS) computer program solves the equations of motion of tree-topology, flexible, and/or multibody mechanical systems as diverse as molecules, mechanisms, robots, spacecraft, and ground vehicles. It has proven to be particularly useful for real-time simulation of the dynamics of spacecraft. DARTS enables the use of high-fidelity mathematical models of the dynamics of spacecraft, without sacrificing simulation speed. DARTS is based on state-of-the-art algorithms from the spatial-operator-algebra formulation for multibody dynamics. This formulation, which has been reported in a number of previous issues of NASA Tech Briefs, was developed expressly for modeling the dynamic behavior of complex, articulated collections of bodies (principally, multiple-link robot arms) that interact with each other in free space or in contact with other bodies in the environment. Both DARTS and the Dshell software described in the preceding article have been executed on a variety of UNIX and VxWorks platforms.
This program was written by Abhinandan Jain, Guillermo Rodriguez, and Guy K. Man of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Computer Software category, or circle no. 134 on the TSP Order Card in this issue to receive a copy by mail ($5 charge).
NPO-20168
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Program for simulating dynamics of multibody systems
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Overview
The document presents the Dynamics Algorithms for Real-Time Simulation (DARTS) program, developed by Abhinandan Jain, Guillermo Rodriguez, and Guy K. Man at Caltech for NASA's Jet Propulsion Laboratory. DARTS is designed to solve the equations of motion for various mechanical systems, including tree-topology, flexible, and multibody systems, which encompass applications such as molecules, mechanisms, robots, spacecraft, and ground vehicles. The program is particularly noted for its effectiveness in real-time simulations of spacecraft dynamics, allowing for high-fidelity mathematical modeling without sacrificing simulation speed.
DARTS employs advanced algorithms based on the spatial-operator-algebra formulation for multibody dynamics, which has been previously documented in NASA Tech Briefs. This formulation is specifically tailored for modeling the dynamic behavior of complex, articulated systems, such as multiple-link robot arms, that interact in free space or with other bodies. The software has been successfully executed on various UNIX and VxWorks platforms, showcasing its versatility and robustness.
The document also discusses the concept of "ruthless linearization" in flexible body dynamics, highlighting the challenges of premature linearization that can occur when modeling body flexibility. It emphasizes the importance of including geometric stiffening terms to maintain model fidelity, particularly in systems with low spin rates. The authors propose that for such systems, dropping deformation-dependent terms may not significantly impact the accuracy of the model, leading to simpler, less complex linearized models.
Additionally, the paper outlines the development of new spatially recursive dynamics algorithms for flexible multibody systems, utilizing spatial operators. These algorithms facilitate efficient inverse dynamics, mass matrix evaluation, and forward dynamics computations. The focus is primarily on serial chains, but the authors also discuss extensions to more complex topologies. The document highlights the computational efficiency of the articulated-body forward dynamics algorithm compared to traditional composite-body algorithms.
Overall, the contributions of this research enhance the understanding of multibody dynamics, providing a high-level architectural framework for mass matrix structures and their inverses. The findings are positioned within the broader context of recursive dynamics research, offering valuable insights for future applications in flexible multibody systems.
