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ADAMS/VIEW 2003 TUTORIAL ME 350 WINTER 2005 UNIVERSITY OF MICHIGAN TABLE OF CONTENTS 1. THE POSTPROCESSOR ........................................................................................ 2

1.1. ANIMATION MODE............................................................................................... 3 1.1.1. Making a Movie .............................................................................................. 4 1.1.2. Getting a picture ............................................................................................. 6

1.2. PLOTTING MODE.................................................................................................. 6 1.2.1. Measuring Angles ........................................................................................... 7 1.2.2. Measuring Joint Loads ................................................................................... 8 1.2.3. Calculating Power Consumption.................................................................. 13

2. CREATING LINKS WITH DIFFERENT SHAPES........................................... 15 2.1. MERGING TWO BINARY LINKS ............................................................................ 15 2.2. CREATING CURVED LINKS ................................................................................. 17

3. COPYING LINKS AND POINTS......................................................................... 20

4. SAVING YOUR MECHANISM IN A NEW STARTING POSITION ............. 24

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1. The PostProcessor At the end of the last tutorial we were left with a functional 4-bar mechanism with an attached spring. Instructions were included for saving and reopening your model. After opening your model from the first tutorial, immediately export the file as file name first_tutorial. Therefore, you will now have the file…first_tutorial.cmd, which is the command file for the mechanism you ended with in Part 1 of the tutorial. You will need this version of the mechanism for your homework this week. With this file made, we can continue moving forward. Your mechanism should look like this in the Isometric view:

You should have already learned to run simulations, so go ahead and run the same simulation as before. Let’s begin by looking at the PostProcessor and delving into its many utilities. The easiest way to get into the PostProcessor is by simply pushing F8, but you can also choose Review>Postprocessing as shown in the following screenshot.

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1.1. Animation Mode The first thing we will do is make a movie of our mechanism in action. You can easily make an AVI movie file of your mechanism by loading the animation and exporting the file. To load the animation make sure that Animation is shown in the top left drop-down menu. Then right-click on the main black screen and click Load Animation as shown below:

The same options for controlling the view and such are available by right-clicking on the animation screen again and going to View Control.

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1.1.1. Making a Movie Play the animation by clicking on the forward play arrow next to the big red circle with an R in it. The R stands for record, as it should. Before you record anything to an AVI file though, you should first make sure your record settings are correct. Check these by clicking on the Record tab in the bottom window of the PostProcessor.

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Your AVI file will be saved in the working directory you chose upon opening ADAMS, and with the file name and extension shown in the window. For the setup shown above the file will be called “tutorial.avi.” Go back to the Animation tab now and lets look at some of the options there. If the AVI file you create is very large (e.g.- 10 MB) you can shrink it down by increasing the frame increment as shown below.

This will make the motion more choppy, but will decrease the file size substantially. The other method for shrinking the file is to make sure that you only run your mechanism through its motion once. As you may recall, we set up our analysis to run the simulation through two revolutions of the input link. You can verify this by changing the Loop field from “Forever” to “Once” and hitting Play (the blue right arrow) as seen in the next figure.

Record Tab

Give your AVI movie a unique File Name

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We can easily change this redundancy in the video by changing End from 201 to 101 (half of the current value). The video plays fairly quickly as well, but this can be slowed down with the Speed Control. After adjusting it so that it plays at a reasonable speed, we are now ready to record our file and make sure it worked. Recording the AVI is simply a matter of pushing the R button and then hitting Play. Do this now. When your mechanism is done going through its motion, just hit the R again and you are ready to move on.

1.1.2. Getting a picture The easiest way to get a snap shot of your mechanism is to just hit the PrintScreen button and then Paste the image into Word or Paint. You can stop the mechanism in any position by hitting pause and then using the PrintScreen button. You can also just take a picture of it in the initial position. The choice is yours.

1.2. Plotting Mode Now on to looking at angles, speeds, loads and power. We need to switch from Animation mode to Plotting mode. Do this by clicking on the drop-down box in the top left and selecting Plotting from the list as seen below.

The following warning will be shown, just hit OK since you already saved the movie of your mechanism in action.

The Plotting window looks like this.

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1.2.1. Measuring Angles Lets first look at the angle of the coupler link as it changes throughout the motion. To do this, simply click on Coupler_XFORM from the list in the Result Set at the bottom of the page. Then choose PSI to select the angle of the link relative to its original position. In order to plot the curve you just need to click on the Add Curves button on the bottom right. This is illustrated in the following screenshot.

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If you want to add another curve to the plot as well, you simply click on the curve you are interested in and hit Add Curves again. For example, lets look at the angular velocity of the coupler as well. Just click on WZ from the Component window and then choose Add Curves again. Your plot should now look like the image below.

1.2.2. Measuring Joint Loads Another measure we can look at is the magnitude of the forces at the joints in our mechanism. Let’s look at Joint_2 for example. Click on JOINT_2 in the Result Set window. You will see that three forces and three torques appear. So that we can quickly look at them without having to add curves and clear the plot, we will instead check the box that says Surf. This allows you to see each plot immediately after it is clicked, but

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you can only see one curve at a time. Click the Surf button now and then look through the Force and Torque plots.

If you were designing a bearing for this joint, what you would want to have is the magnitude of the force, not the individual direction components. There are a few ways to get this. One way would be to use the math tools available in ADAMS and calculate the sum of the magnitudes of the forces in the x and y directions. We will do this later on in the tutorial. An easier way is to look in the Objects instead of the Result Sets. This is done by clicking Objects from the drop-down menu box where it says Source (See below).

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Now go to Joint_2 under the Object menu, choose Element_Force from the Characteristic menu, and then Mag for Component. Your plot should look roughly as follows.

Interlude, create a torque source (motor) As our final exercise with the PostProcessor, we will calculate the power required to run this mechanism. First we need to make a few changes to the mechanism. As can be seen on the previous plots, the spring that was added is extremely stiff. The forces that it induces are fairly unreasonable, and even if the spring did not break in two, a motor couldn’t realistically drive the mechanism at the constant speed defined. Therefore, we will first deactivate the spring and motion source and replace it with a torque source. Hit F8 or select File>Close Plot Window to get back to the regular ADAMS/View window. Now right-click on the spring and select (De)Activate towards the bottom of the list as shown.

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Now uncheck both boxes in the window that appears.

Hit OK and then do the same thing for the motion (motor). The large blue arrow representing the motion will still be there, but should be a darker shade now, indicating that it is not Active. Next create a torque source (motor) by selecting the “Applied Force: Torque” from the list with the spring in it. Remember that right-clicking on the tools in the Main Toolbox will give you many more options from within the same category. Following is a screenshot of what you should select.

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In the menu that appears in the Main Toolbox window, check the box by Torque and enter a value of 25, meaning 25 N*mm. Make sure to follow the directions at the bottom of the window. Select the input link as the link to which the torque will be applied. Then choose point input_A as the point at which the torque will be applied.

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Let’s now simulate our mechanism again, only this time change the End time to 1 second instead of 24. This will slow things down a bit and make it easier to look at the results.

1.2.3. Calculating Power Consumption After you have simulated your mechanism, go back to the PostProcessor to make the final measurements. We are looking for the power required to drive this mechanism. We can find this by multiplying the motor torque by the angular velocity at which that input link moves. We will do this by plotting both curves and then multiplying them together. In order to plot all three curves on the same plot we will need to take it out of surf mode and add the individual curves one by one. You should already know how to do this at this point, but in case you don’t remember, just uncheck Surf, the box on the far right. Now we need to add the desired curves to the plot. The curves we desire are found in the Objects Source, so select that and then choose input>CM_Angular_Velocity>Mag and click on Add Curve.

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Follow the same procedure to plot the value of the input torque by selecting SFORCE_2>Element_Torque>Mag and again selecting Add Curves.

As expected, the value is constant at 25 N*mm as indicated on the vertical axis at the right hand side of the plot. In order to manipulate the curves as desired, we need to use the Curve Edit Toolbar. This is available by clicking on the capital sigma icon at the top middle of the window as shown in the next image.

The second row of icons appear. Most of the icons are self-explanatory, so take a look through them, they may come in handy at a later point. The one we are looking for is the third one from the left, showing a multiplication sign. When you multiply these two

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curves (Angular Velocity and Torque) together ADAMS will complain that the units do not match, but since we know what the units are, that is not a problem. Just hit OK and on we go. Your resulting plot should look like this.

This curve represents the power required to drive this mechanism at the specified torque. If we were to select a motor to drive this, we would need a motor capable of providing at least as much power as the maximum of this curve. We can find this value quite easily by looking at a different toolbar called Plot Tracking. Click on this icon as shown below.

Now select the pink curve and the Max field will show that the maximum power required is roughly 40,200 N*mm*deg/s. Converting this value to J/s=W is quite easy, just divide by 1000 to convert mm to m. Then convert to HP by dividing by 745.7 HP/W to get a maximum power requirement of 0.054 hp.

2. Creating Links with Different Shapes

2.1. Merging two binary links In this section, you will learn how to merge binary link geometries to form new links of different shapes. To begin, delete the entire coupler link.

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Create a binary link between points COUPLER_A and COUPLER_B.

Now, create another binary link between points COUPLER_A and ON_COUPLER.

Now, choose the tool that unites two solids. By following the instructions given in the status bar, choose the first link you recently created (between COUPLER_A and COUPLER_B), then choose the second link you recently created (between

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COUPLER_A and ON_COUPLER). After you right click, to accept your two links, you will see that that coupler is now the union between the two links. Even though the two links are united, right click on the first link. Notice the part number of the link. Now, right click on the other link. Notice that the second link has the same part number. Now, let’s change the width and depth of both links to be the same. You will find that you can still change the link geometry of the two individual links even though they are now united. Do this to change the width of the links to 15 mm and the depth to 10 mm.

2.2. Creating Curved Links Now we will change the coupler link geometry one more time. First, delete the entire coupler link you just created. You will receive a message, but continue by choosing Delete All.

Next, choose the Spline tool from the toolbox. When the spline toolbox appears, click on the Closed toggle as shown in the following screenshots.

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Right click on the back working space, and turn the working grid off. By doing this, your cursor will not automatically snap to the grid dots. Now, pick at least 8 points that make a full curve around the three coupler points. Make the curve similar to the shape shown in the figure below. When all your points are made, right click to make the total enclosed shape. We will be using this link as our new coupler link.

By moving one of the square points on the outside curve of the coupler link, you can modify the shape of the coupler. Try to roughly match the shape shown in the figure below.

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Now, choose the Extrusion Tool. When the extrusion tools’ toolbox appears, set all the settings to the settings shown below. Then, select the coupler, and then select the curve on the coupler. This will extrude the part to add depth to the shape.

When done, the coupler should look like this.

Rotate the mechanism to verify that the shape was extruded. From the side view, the coupler link should be exactly between the follower link and the input link.

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Rename the part ‘curved_coupler’ by right-clicking on the link and using Rename as before. Now view the mechanism from the front (just hit Shift-f). Using revolute joints, connect the coupler to the other links by adding joints between the coupler and the input link and the coupler and the follower. The coupler link is not parameterized, so when choosing the locations for the joints, just select the points that are in the position where the joints should be. For example, in this case, it is not important whether you choose INPUT_B or COUPLER_A.

Simulate the mechanism for 12 seconds to verify that it works with the new coupler link.

3. Copying Links and Points For stability purposes, your prototypes may use two mechanisms working in parallel with one another. For this exercise, first delete the spring and its two end points since springs and their parameterized points do not copy well. To begin copying your links and points, zoom out a little in order to have the entire mechanism on the screen. Then, select all the components of the mechanism by clicking in the black space to the top left of the mechanism and dragging diagonally over the mechanism to the bottom right corner of the mechanism. This should have made a box that selects ALL components of the mechanism. If you missed a few, go back and re-select the components. Once all the

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components are selected, hold down the control key and deselect all the joints and gravity and motions. (When you deselect an object, it is no longer bold.) Once this is done, rotate the mechanism to a more isometric view. (The isometric view will help us when we do the copying.) Now choose the move tool.

When the ‘move’ toolbox appears, choose all the options shown below. Now, move your cursor around the mechanism until a vector pointing in the global Z direction appears. The, right click to accept.

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Your mechanism should now have a copy.

From the ‘Right’ view (shift-R), you will see the following.

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We would like to have the two sides of the mechanism be reflections of each other. To do this, use the Point Table and modify the Z locations as shown below.

The side view should now look like this.

Now, make your joints and motions for the new half, but do not make another gravity for the new half.

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4. Saving Your Mechanism in a New Starting Position To practice saving your mechanism in a new starting position, it will be easiest to first delete the copy of the mechanism that we just made. Go to the ‘Edit’ menu at the top of the page and select ‘Delete’. Hold the control key down and choose the following parts that are the copies of the originals. Then select OK.

When you rotate your mechanism, you will see that floating points and arrows are still left behind. Delete each of these individually. Make sure to delete all remaining parts of the mechanism’s copy.

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Now, run a ‘Simulation’ for 12 seconds using 100 steps. Click the reset button when done. We now have the information we need to run an animation. Choose the ‘Animation’ tool. Select the button in the bottom of the animation toolbox.

Using the Animation Controls that appear, use the arrow buttons to click through the frames. Find step 42. We will change our initial starting position to this position. To do this, choose the button shown below. When a pop-up box appears, change the frame to 42 and select OK.

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Your mechanism should now look like this. Notice how the joint icons have rotated.

Also note that ADAMS has made this a new model. You can see this in the upper left hand corner of your ADAMS window.

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Before we save our new model, we need to fix the joints and motion. (There rotated positions will create confusion during analysis.) Delete the motion and joints. The ‘Delete’ option from the ‘Edit’ menu will be helpful.

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Once the original joints and motion have been deleted, create new joints and motion. For the joints between the coupler and the follower and the coupler and the input link, use the markers that are located on the ends of the follower and input link. To find them, place your cursor near the area where the joints used to be. Select the markers that automatically popup. Your mechanism should now look like this:

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Run a 12 second, 100 step simulation again to verify that the model starts from the new location.