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Take Home Exam

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F11Wendy

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Unread post Fri Nov 04, 2011 6:00 pm

Take Home Exam

How is a file containing the simulation results (dPend.res) generated? Does it just need to include q, q_dot, and q_ddot at each time point?
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Dan Negrut

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Unread post Sat Nov 05, 2011 11:17 am

Re: Take Home Exam

yes, each line should contain a number of 9*Nbodies. The first nine entries should be the position, velocity, acceleration of body 1; the next nine numbers should be the position, velocity, acceleration of body 2; etc.
this is not really important right now, but down the road it might become if you want to use that visualization tool that Hammad lectured about a while ago...
Dan
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F11Christopher

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Unread post Mon Nov 07, 2011 2:57 pm

Re: Take Home Exam

In order to obtain the velocity and acceleration for point Q directly from our simEngine2D, do we need to move to LRF on Body 2 so that it is located at point Q?
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Dan Negrut

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Unread post Mon Nov 07, 2011 6:09 pm

Re: Take Home Exam

F11Christopher wrote:In order to obtain the velocity and acceleration for point Q directly from our simEngine2D, do we need to move to LRF on Body 2 so that it is located at point Q?


In principle, you would compute the position, velocity, and acceleration of point Q using the information on slide 4 and 7 of 09/27 lecture:
http://sbel.wisc.edu/Courses/ME451/2011/Documents/Lectures/lecture0927.pdf

However, to make things simpler, keep the LRF where it is, and simply plot the position, velocity, and acceleration of the LRF. This will simplify the take-home exam.

One more thing: when you write the results in the dPend.res file, you should have 19 columns:
- the first column is the value of time t
- the next nine columns contain info regarding body 1: 3 pos, 3 vel, 3 accelerations
- the last nine columns contain info regarding body 2: 3 pos, 3 vel, 3 accelerations
Note that the file should have as many rows as output steps you have in the acf file.

I hope this helps. Post any followup questions here.
Dan
P.S. I'm going to email the rest of the class and ask them to modify the text of the take-home exam so that people report the pos, vel, and acc of the LRF instead of point Q.
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F11Brian

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Unread post Mon Nov 07, 2011 7:00 pm

Re: Take Home Exam

Do you want a position plot, or just plots of velocity and acceleration?
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Dan Negrut

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Unread post Mon Nov 07, 2011 10:49 pm

Re: Take Home Exam

Velocity and acceleration.
Dan
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F11Carrie

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Unread post Fri Nov 11, 2011 4:48 pm

Re: Take Home Exam

I'm having a weird problem with my code. If I use "clear all" before running simEngine2D, I get an error the first time the code gets to a line defining a symbolic variable. If I run my code again without clearing after this happens, it's fine. Any ideas?
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F11Brian

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Unread post Sun Nov 13, 2011 2:49 pm

Re: Take Home Exam

I don't think you can use "clear" in a function. When you do, it clears the the function's input, which for our case is the name 'dPend'. You may just have to enter clear manually into the control panel before you run your SimEngine2D.
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F11Carrie

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Unread post Mon Nov 14, 2011 10:45 am

Re: Take Home Exam

I'm not using "clear" in the function. This is happening when I clear manually or upon first running simEngine2D after starting Matlab.
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Dan Negrut

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Unread post Wed Nov 16, 2011 5:13 pm

Re: Take Home Exam

F11Carrie wrote:I'm having a weird problem with my code. If I use "clear all" before running simEngine2D, I get an error the first time the code gets to a line defining a symbolic variable. If I run my code again without clearing after this happens, it's fine. Any ideas?

No idea why that's the case.
in general, if you don't clear all you might see problems, not the other way around.
might also be an internal bug with the symbolic toolkit.
What i'd try is to to some useless symbolic computations to "seed" symbolic engine...
Just a wild suggestion...
Dan

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