## bbillingsley3 3 years ago For HW#14, problem 3, it says that we are not concerning ourselves with orientation. Does this affect our end effector configuration, or is it still: ge(a) = g1(a)g2(a)g3(a)g4 ?

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1. Chipper10

It's still that. You just take the position only, don't worry about the orientation.

2. bbillingsley3

So, we need Jbody(a) in order to calculate the psuedo inverse. Do we do the same procedure from last HW to find Jbody(a)?

3. Chipper10

You don't need Jbody this time, just J. The question doesn't as you to use the body velocity or anything to that effect.

4. bbillingsley3

How do we find xi from the (x(t), y(t)) given?

5. Chipper10

What is xi?

6. bbillingsley3

I thought we would calculate alphadot = (psuedo invese) * (xi)

7. Chipper10

Yes but what do you think is xi?

8. bbillingsley3

I would imagine it is some sort of velocity. Would we take the derivative of the (x(t),y(t))?

9. Chipper10

Yes

10. bbillingsley3

I have a 3x1 vector for my psuedo inverse. How do I multiply that by xi = (.5sin(t), .49cos(t) )?

11. Chipper10

You pseudoinverse should not be 3x1. What formula are you using?

12. bbillingsley3

Jsharp = Jbody^T * (Jbody*Jbody^T)^-1 I used the Jbody that we solved for in the last homework and just plugged in our new alpha values

13. Chipper10

I told you above that you only need J. The manipulator in this homework is different from the one last week and therefore has a different J. Since we are only considering the position and not the orientation, the jacobian should be 2x3. When you apply the formula above you should get (2x3)*(3x3) = 2x3

14. Chipper10

I have to go

15. bbillingsley3

I don't understand how I calculate a 2x3 Jacobian from the information given. Also, I don't know how xi = ( .5sin(t) , .49cos(t) ) can give me a 3x3 matrix.

16. bbillingsley3

I have figured out the 2x3 Jacobian. Would my 3x3 xi be : [.49cos(t), -.5sin(t), 0; .5sin(t), .49cos(t), 0; 0, 0 , 1] ?

17. Chipper10

Your xi would be a 2x1. You may be using the wrong form or the pseudo-inverse. You want your J# to be a 3x2.

18. Jaynator495

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