User manual MAPLESOFT MAPLESIM 4

[. . . ] MapleSim User's Guide Copyright © Maplesoft, a division of Waterloo Maple Inc. 2008-2010 MapleSim User's Guide Copyright Maplesoft, MapleSim, and Maple are all trademarks of Waterloo Maple Inc. © Maplesoft, a division of Waterloo Maple Inc. No part of this book may be reproduced, stored in a retrieval system, or transcribed, in any form or by any means -- electronic, mechanical, photocopying, recording, or otherwise. [. . . ] Save your changes in the . mw file and the . msim file to which you added the custom component. 4 Simulating and Visualizing a Model In this chapter: · How MapleSim Simulates a Model (page 63) · Simulating a Model (page 66) · Simulation Progress Messages (page 71) · Managing Simulation Results (page 71) · Customizing Plot Windows (page 72) · Visualizing a Multibody Model (page 78) · Best Practices: Simulating and Visualizing a Model (page 96) 4. 1 How MapleSim Simulates a Model Modelica Description The equations for many components in the MapleSim library are described using the Modelica physical modeling language. On the other hand, the equations for multibody components are generated by a special-purpose engine, which uses advanced mathematical techniques to ensure that the equations are as concise and efficient as possible. These equations are converted to Modelica. For more information about Modelica, visit http://www. modelica. org. Model Description Each component in your model contains a system of equations that describes its behavior; these systems of equations can consist of purely algebraic equations or differential equations. Also, a component may define any number of events, which can change the component behavior during a simulation by enabling or disabling part of the equations in the system or changing state values. Connections between two or more components generate additional equations that describe how these components interact. System Equations All of these equations are then collected in one large system and parameter values are also substituted in. Now, the MapleSim simulation engine has a potentially large system of hybrid differential algebraic equations. This means that the system has differential equations with algebraic constraints, as well as discrete events. 63 64 · 4 Simulating and Visualizing a Model Simplified Equations A process called index reduction is applied to reduce the algebraic constraints as much as possible. Other symbolic simplification techniques also reduce the number of equations and variables. Note that algebraic constraints may still be present in the equations after this step. No information is lost during the simplification process and the full accuracy is preserved. At this point, initial values for all of the variables remaining in the system of equations must be computed. This is a non-trivial step because typically only a small number of the initial conditions is fixed in the system model. The remainder of the initial conditions must be computed in such a way that the entire equation set is consistent. You can set initial values for some of the variables by specifying parameter values for certain components in the Inspector tab on the right side of the MapleSim window. If the specified initial conditions are not consistent, an error will be detected during the simulation. Initialization When all of these preprocessing steps are complete, the numeric solving process can begin. A sophisticated differential algebraic equation (DAE) solver based on the Rosenbrock integrator (for stiff systems), the ck45 integrator (for semi-stiff systems), and rkf45 integrator (for non-stiff systems) is used to numerically integrate the system of equations. Algebraic constraints are constantly monitored to avoid constraint drift, which would otherwise affect the solution accuracy. The rosenbrock (stiff) solver is a good choice for typical systems. In some cases, the non-stiff solvers will offer better performance; they are a good option for models where all quantities vary at approximately the same rate. Numeric Integration and Event Handling During numeric solving (or "integration"), inequality conditions that are part of the model are monitored and an event is triggered when one or more of these conditions change. Whenever such an event is encountered, the numeric solver is stopped and the simulation engine computes a new configuration of the system of equations based on the event conditions. This step also involves recomputing initial conditions for the new system configuration. [. . . ] When the simulation is complete, the following graphs are displayed. 9. Save the file as SliderCrank. msim. 128 · 6 MapleSim Tutorials 7 Reference: MapleSim Keyboard Shortcuts Opening, Closing, and Saving a Model Task Create a new model Open an existing model Close the active document Save a model as an . msim file Windows and Linux Macintosh Ctrl + N Command + N Ctrl + O Ctrl + F4 Ctrl + S Command + O Command + W Command + S Building a Model in the Block Diagram View Task Windows and Linux Macintosh Command + R Rotate the selected modeling component 90 degrees Ctrl + R clockwise Rotate the selected modeling component 90 degrees Ctrl + L counter-clockwise Flip the selected modeling component vertically Flip the selected modeling component horizontally Ctrl + F Ctrl + H Command + L Command + F Command + K Command + G Command + D Group the selected modeling Ctrl + G components into a subsystem Display or hide probes in the Ctrl + D model workspace Browsing a Model in the Block Diagram View Task Windows and Linux Macintosh Command + M Command + numeric keypad plus key Command + numeric keypad minus key View the selected modeling component or subsystem in Ctrl + M detail Zoom into the model work- Ctrl + numeric space keypad plus key Zoom out from the model workspace Ctrl + numeric keypad minus key 129 130 · 7 Reference: MapleSim Keyboard Shortcuts Browsing a Model in the 3-D View Task Windows and Linux Macintosh Move the camera around a Ctrl + left mouse but- Command + mouse 3-D model in the perspective ton click and drag click and drag view Shift + left mouse button click and drag Zoom into or out from the 3- Alt + left mouse butD workspace ton click and drag, or mouse wheel Panning a 3-D model Shift + mouse click and drag Alt + mouse click and drag, or mouse wheel Glossary Term Description Formatting option that allows you to enter mathematical 2-D math notation text, such as superscripts, subscripts, and Greek characters. The area of the MapleSim window in which you can build 3-D workspace and edit a 3-D model. Shapes that you can display in a 3-D model to create a realistic representation of a system model. [. . . ]