Simulation and Animation of Mechanical Systems

Abstract

This paper introduces a process for simulating and animating mechanical components in the context of a larger system. Using the NASA HL-20 flight vehicle’s main landing gear as an example, the paper shows how the CAD assembly can be used as a starting point for creating a dynamic model as well as a realistic animation of the mechanical components. The paper also describes how a dynamic model created from the CAD assembly can be integrated into the larger model of the overall flight vehicle and how the animation created from the CAD assembly can be incorporated into a larger flight vehicle animation. The resulting model and animation are used for detailed analysis and visualization of a main landing gear collapse due to a sudden wind gust shortly before landing. Nomenclature I(n) = Unity matrix of n rows and n columns, with diagonal elements equal to one and off-diagonal elements equal to zero. I. Introduction ODELING of mechanical systems and components often starts with CAD tools. These tools are useful for specifying the detailed three-dimensional (3-D) mechanical design of a component. Once the CAD model of a mechanical component is complete, engineers will often need to design a control system for it. With the control design task accomplished, engineers will want to analyze how the mechanical component affects the performance of the overall vehicle and how the mechanical components work together with other vehicle systems. For example, the landing gear group for an aircraft manufacturer may develop a mechanical design of a landing gear; the controls group may develop a controller for that mechanical design; and the systems engineering group may then model how the landing gear operation affects the dynamics of the overall vehicle and how the hydraulic actuator works with the landing gear mechanical design and control system. Often, different software packages are used for each step of this process, making it difficult to move from mechanical 3-D modeling to control design and then from control design to a system level simulation. This paper introduces a streamlined workflow that enables quick and easy transition from mechanical 3-D modeling to control design and then to system level modeling and simulation. This workflow provides a compelling solution to the control design and system modeling tasks. This solution will be based on using the commercial off-the-shelf software tool, Simulink ® , from The MathWorks, Inc. Using the proposed approach, we will translate a CAD file into an environment where control design can be easily achieved. We will also explain how to easily model and simulate multi-domain systems, including mechanical, hydraulic, and electrical components. We will discuss how to include models of mechanical components into models of larger systems. In addition, we will show how models for environmental conditions, such as wind turbulence and changes in atmospheric pressure and temperature with altitude can be easily integrated into the model of the overall vehicle. As we discuss the overall process, we will specifically focus on two areas of this workflow. First, we will show how engineers can create Simulink models of mechanical components using CAD models as a starting point. Second, we will discuss how to create high quality 3-D animations from these models. We will present a process for exporting CAD models into Virtual Reality Modeling Language (VRML) files. VRML enables high quality online 1