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1-Visitor
August 17, 2014
Solved

The degree of freedom

anyone can help me

I do not know what wrong

I know this law of degree of freedom

n = 3 (l – 1) – 2 j – h

l=link , j=lower pair , h=high pair

 

8-17-2014 4-26-40 PM.png

8-17-2014 4-28-00 PM.png

n = 3 (l – 1) – 2 j – h

n = 3 (4 – 1) – 2 × 4– 0 = 1 one degree of freedom

but of program I think this happen

n = 3 (4 – 1) – 2 × 4– 1 = 0

8-17-2014 4-39-10 PM.png

n = 3 (4 – 1) – 2 × 4– 0 = 1 degree of freedom

n = 3 (4 – 1) – 2 × 4– 1 = 0 but this result of program

8-17-2014 4-39-42 PM.png

 

this example of 5 link i must have two degree but program give 1 degree

8-17-2014 6-48-07 PM.png


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dschenkenAnswer
2-Explorer
August 18, 2014

Each motor controls a degree of freedom.

8 replies

2-Explorer
August 17, 2014

https://en.wikipedia.org/wiki/Chebychev%E2%80%93Gr%C3%BCbler%E2%80%93Kutzbach_criterion

The formula for the planar condition in the link above, appears different from the one you show.

I agree, the depicted mechanism looks to have 2-degees of freedom. Check to make sure none of the pin joints has an extra constraint.

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jwaller1-VisitorAuthor
1-Visitor
August 18, 2014

I give my formula form book "Theory Of Machine R.S.Khurmi"

degree.png

and this not problem

problem is all my mechanism degree of freedom have less than one

I check pin from all bar and I think no any extra constrain but same result all time

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2-Explorer
August 18, 2014

Have you attached any motors?

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2-Explorer
August 17, 2014

For those who are interested in linkages, this is also worth reading:

https://en.wikipedia.org/wiki/Overconstrained_mechanism

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