Dynamic Simulation Tutorial PDF [PDF]

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Autodesk Inventor Tutorial Dynamic simulations are very powerful tools that allow you to perform rigid body dynamic simulations (i.e. both kinematic and kinetic) of any drawing you have in Autodesk Inventor. This type of simulation is used on assemblies to simulate time varying behavior of a system. You can download the software in Autodesk website --> download --> software for student --> inventor professional. In this tutorial, we are going to understand how to use the main features of the dynamic simulation tool in Inventor. We will learn how to find position, velocity and/or acceleration of a given point in a rigid body; we will also learn how to calculate forces that should be applied to a given part of the assembly to keep it static, and other things. In order to start, you have to assemble the cutting blades using the parts (.ipt files) you will find in the homework folder. You need to assemble them using: “assemble” → “constraints”. However, since the focus of this homework is not to learn how to assemble things, you can just open the assembled engine called “Ensamble_cuchilla.iam”.



Next, in order to start your dynamic simulation, click on the “Environments” tab and select the Dynamic Simulation option on your left. You are now in the Dynamic Simulation environment in which you will be analyzing your rigid body.



On the left side of the screen, you will find the relationships (joints) between the different parts of your assembly. Make sure you don’t have a redundant constraint or a warning sign in any of your joints.



Define Gravity: The first step we will approach is to define gravity in our system. In order to do so, you must right click on “Gravity” which is located in the “External Loads” group node. You will define gravity depending on the coordinate system you’re using. For instance, in the cutting blade assembly, the negative y-coordinate will correspond to the direction of gravity.



Imposing Motion: A very useful feature of Dynamic Simulation is to make something move the way you want it to move; this is called imposed motion. In our case, we want to make our shaft turn according to the following equation of angular velocity 𝜔(𝑡) = 195 𝑅𝑃𝑀 = 1170



𝑑𝑒𝑔 𝑠



∙ 𝑡. In order to do this, we must



follow several steps: 1. Locate and select the joint that corresponds to the movement we want to impose.



2. Right Click and go into properties, then click into the degrees of freedom tab (dof).



3. Select Edit imposed motion. 4. Enable imposed motion and select the velocity driving. Change from Input Grapher to constant value and write down the desired speed.



5. Alternatively, you can make it so that the simulation doesn’t start with the final velocity from the beginning, but instead starts from 0 RPM and then reaches the desired velocity. Change from constant value back into Input Grapher. 6. Click on the graph on the right to access the parameters of the function. Change the start and end points of the line segment to decide at what time the system will reach 195 RPM.



7. Run your simulation using the simulation player.



To exit simulation player, you must click on construction mode



.



Trace Moving Parts: After imposing motion in our rigid body system, we want to know how different parts of our system move. To do this we will use the “Trace” feature on the results section. 1. Click on Trace and select the part you want to keep track of.



2. Check the acceleration, trajectory and velocity boxes for the “Display Trace” and the “Output Trace Value”.



3. Run the simulation player. 4. Open the “Output Grapher” in the results section and find the “Trace” node on the left column. Open the trace you made to view how the velocity, position and acceleration of the trace varies with time. 5. Open each trace and analyze how the vector components for each trajectory, velocity and acceleration vary with time.



Forces and Torques: Another way to make your system move is to set forces or torques on a point in one of the assembly’s parts. For the purpose of this example we will set a torque on the shaft of our cutter, representing a motor. To set this torque you must follow the following steps: 1. Select the “Torque” feature on the “Load” menu. 2. Select the object and the location where the torque will be applied. 3. Select the direction of the torque by clicking a part that points in the same direction of the torque. 4. Give the torque a magnitude or define a function that describes the way the torque will be applied on the shaft. Because we want to simulate a motor, we will use a function with the Input Grapher.



5. The torque of a motor depends on its angular velocity, as can be seen in the next figure showing a torque vs speed curve of a Siemens motor (Imodel 1LE22211AB2):



6. Because torque depends on speed, we have to change the X axis of the Grapher. Click on the Reference button, then select the joint between the base and the pin. Then, select the velocity. Now, the Grapher will show a torque vs angular velocity graph that you can edit.



7. Create a curve that resembles the motor curve of the motor you will use. Remember that, if you use a reduction, the torques in the graph will increase and the velocities will decrease.



8. Run the simulation in simulation player. Note: if you enabled imposed motion, you should disable it first. You can set an imposed motion or a torque on a single shaft, but you sould not do both. 9. Open the “Output Grapher” to see how the motor torque changes with time.



. Every force or torque that you add to your system will appear in the “external loads” node on the left column of the screen. Also, as you checked the box to show the vector representation of velocity and acceleration of a certain point, you can zoom in while running the simulation player to see how these variables change.