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02-28-2017 08:09 PM

Greetings!

New user of Amesim here, trying to learn it by recreating examples from textbook problems, and this one has me stumped.

I'm attempting to create an Amesim model of a projectile with an initial velocity, an initial height above the ground, at an initial angle from the horizontal. I am using a 1-port planar mechanical body with a zero velocity source attached. I think that's all I need, but I'm not getting the correct results. There isn't much documentation on something like this, although there is a ball drop tutorial that was somewhat helpful, even though that was a 1-D example. I have played around with the various parameters, both relative and absolute, without success. Any advice is appreciated!

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03-01-2017 03:07 AM

Hi @Skarr11

This is rather simple.

You simply put a body on your planar sketch:

Then you have to parameterize it with an angle and a start x and y velocity:

**single port body**

PLMBOD01-1 : Real parameters with non default values Unit Value initial absolute angular position degree 50 O: initial absolute x velocity m/s 5 O: initial absolute y velocity m/s 5 mass kg 0.1 moment of inertia around Gz axis kgm**2 0.001

Then when you display y displacement against x you should get the following curve:

Kind regards

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03-06-2017 09:59 PM

Hi Domi--

Thank you for responding. However, I'm still not clear on the initialization parameters. For example, if the projectile is initially at some angle with some velocity, that velocity be resolved into its x and y components, which would be the values of the "Initial absolute X/Y velocities"

In my example, my initial velocity is 150 m/sec, and the initial angle is 45 degrees. Therefore, both x and y velocities are 150*cos(45 deg) = 150*sin(45 deg) = 106.1 m/sec. For some reason, when I enter these expressions into the parameters, I get the following:

As you can see, the velocities are not correct. When I enter the resolved velocities directly (106.1 m/sec), I get correct results. What am I missing when entering these expressions?

Thanks!

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03-07-2017 03:09 AM

Hi Skarr11,

maybe the expression is not set correctly. Can you please check the initial velocity experession as the value of the angle in your cos or sin function is not in degree but in radian.

Try something like 150*cos(45*2*pi/360)

In my example it looks fine:

Regards,

A. Bachar

Solution

Solution

Accepted by topic author Skarr11

03-07-2017
06:56 AM

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03-07-2017 06:56 AM

Hi ABachar--

Yes, that did the trick. I thought that since the initial angle had units of degrees, the expression for velocity would also accept degrees.

Thank you!

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