Robotic Manipulator 3-RRP v2

I recently asked a question about a 3-RRP manipulator but the only answer didn't work for my robot.

I would describe the manipulator as an arm that rotates around the shoulder over the x-y axis, the elbow that rotates around the x-y axis also and the forearm - hand that moves FORWARD and BACKWARDS. (check attached image for a more described explanation).

The solution I calculated cannot be correct as the "hand" moves up and down and not forward and backward.

I tried setting other values to the DH-parameters but I still think this is not the correct answer.

My professor said that we are not allowed to use a structural parameter to rotates the axes and that the use of 3 rows on the DH-parameters is the correct solution.

I've been trying to get this for almost 1 week now and seems impossible to me.

On the image you can see some of my attempts to solve this problem.

A detailed answer with the reason for the values of the DH-parameters would be awesome.

1 Answer

I'm unable to comment due to reps shortage, so, I'm adding it as an answer. This might answer your question.

In your new attempt, the transformation of axes from origin-1 (i.e. $$x_1, y_1, z_1$$) to origin-2 ($$x_2, y_2, z_2$$) is incorrect as $$x_2 \not\perp z_1$$ and $$x_2 \not\cap z_1$$, violating DH convention.

PS: It would be better if you could update your previous question itself with the new attempt you made so that everything is in one place.