ME 321 Homework


Hwk 2 #2

Hello, I am turning my homework in a class late so I can really have time to digest and analyse all of the problems. Right now, Im having issues clarifying whether my velocity equation is correct.

My loop closure equation:
r a/0 + r b/a = r o/a Where o is the point connecting the point a and point b
like in problem 1 of hwk 1.

This yields:

(A)i2 +(L3)i3=(B)i

Derivative of this:

(Adot)i2 -(A*lamdadot)j2 + (L3*thetadot)j3 = (Bdot)i

My questions specifically is if L3 should have an i3 component when taking its derivative. Note: i found Adot when looking just at velocity components in the j direction. This yielded (Adot)i2 = (bdot)i which I then dotted with i2 to get Adot = Bdot*cos(lamba) since i2 = cos(lamba)i + sin(lamba)j

Thanks,

Andrew
United States
Hi Andrew,

In this problem the lambda direction is fixed in the ground, so that its derivative is zero. In your above equation this would correspond to
lambdadot = 0

To your question, since l3 is constant there will be no component in the i3 direction. Also, when you go to solve, you should dot the whole equation with whatever direction. In this problem, if you want to get rid of the j3 direction, then dot everything with i3.