So I was given a course assignment to assign frames and write D-H parameters for this robot using only 5+1 frames (with Frame $\{5\}$ at $P$ and Frame $\{0\}$ at $O$).
And I assigned them like this:
My question is: From Frame $\{1\}$ to Frame $\{2\}$, what are joint distances $a$ and $d$?
The best answer I could get was 0. But obviously it should be zero for one axis and $a_1$ for the other. What's wrong?
I have read a similar question here. But the answer points me to another method which is impossible for me.
Edit: No matter I put $a_1$ in $a$ $$(\alpha,a,d,\theta)=(-90^\circ,a_1,0,\theta_2-90^\circ)$$ or in $d$ $$(\alpha,a,d,\theta)=(-90^\circ,0,a_1,\theta_2-90^\circ)$$ The joint distance $a_1$ does not appear in $z$. What it gave out is $$\left( \begin{array}{cccc} \sin{\theta_2} & \cos{\theta_2} & 0 & a_1 \\ 0 & 0 & 1 & 0 \\ \cos{\theta_2} & -\sin{\theta_2} & 0 & 0 \\ 0 & 0 & 0 & 1 \end{array}\right) \text{ or } \left( \begin{array}{cccc} \sin{\theta_2} & \cos{\theta_2} & 0 & 0 \\ 0 & 0 & 1 & a_1\\ \cos{\theta_2} & -\sin{\theta_2} & 0 & 0 \\ 0 & 0 & 0 & 1 \end{array}\right)$$ Obviously, $a_1$ should appear in $Z$-translation instead!