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# attack angle variation

## attack angle variation

(OP)
Dear Friends,

I have been trying to plot the attack angle variation of a wiper blade over a curved windshield surface with different wiper pivot shaft orientations via Catia V5.

What i try to do is basicly written below;

i rotate the plane which represents the wiper blade starting from the park position, rotation axis is the pivot shaft of wiper linkage over the curved windshield. I intersect the mid point of the plane with windshield and take the normal of the windshield surface from that point then i measure the angle between the surface normal and the plane that represents the wiper blade, and record the value.

I have to do it on diffeent wipe angle positions such as 10°, 20°, 30°,40°...80° until the uppermost point of wiper blade. If i get a good plot then i stop but if i can not satisfy required plot then i do all the things again with a different rotation axis (different pivot shaft orientation.)

I wonder if is it possible to automate above procedure in order to save time on Adams view.

Thank you.

### RE: attack angle variation

I don't quite understand what you are asking. I think the answer is yes, it should be easy to generate a curve of marker orientation vs wiper angle in A/View. However, the way that ADAMS reports angles is not intuitive. You may find it easier to report x y z triads for three points on a plane and deriving angles in your own way.

To put your mind at rest simulating the mechanism in ADAMS is easy. The tricky bit is reporting angles in a way that make sense.

Sorry, that is a lousy answer. You could try the ADAMS user forum, see the FAQ.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

### RE: attack angle variation

(OP)
Thank You Greg,

Yes that is what i need, a curve of markers on the windshield while wiper blade is rotating with respect to wiper pivot shaft axis on curved windscreen surface. These markers must be the contact points between the curved windshield and the "middle point of the wiper blade" from park position to the end of stroke.

However, i have to measure the angles between the "windshield surface normals on each marker" and "blade normal" then plot with respect to wipe angle. I have to repeat this procedure for different pivot shaft axes until i get an acceptable attack angle variation from park to end of stroke. I am not sure if there is an operator which tells me the surface normals of a curved surface for different points on it.

Regards.

### RE: attack angle variation

Ah the windscreen is curved of course.

That could be rather tricky, depending on how you model the wiper blade and the windscreen, and the contact between them. Either way it is outside of my experience, I'd contact MSC support, and have a good look at the ADAMS forums and knowledge base.

Orienting the markers that define the screen so that Y is normal to the screen at that point is easy enough, just use XP and ZP to point at neighbouring markers.

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

### RE: attack angle variation

If you are using 3D contact you get the surface normal vector reported as a result for each contact track. So if you model your blade with several small spheres and let them contact your windshield you have well defined contact points/tracks and can use the surface normal in post processing to calculate your angles. I would probably export this to Matlab and do the calculations there, but it is doable to use a computed measure as well.

Jesper Slattengren
www.prattmiller.com

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