Make: Robotic Arms

169Chapter 9: Inverse Kinematics for 3D Movement

Taking advantage of the Pythagorean theorem is a great way to determine

the various angles of a right triangle. Thankfully, the values of x, y, and d

create a perfect right triangle, making d—in this case, the hypotenuse— easy

to calculate:

Now that we know the value of d, we know the lengths of all three sides of

our right triangle. Once that is taken care of, we can move on to finding the

value of our first angular variable: the rotation of the base of our robotic arm,

Ө. If we remember our use of tan and arctan, we can find Ө by using arctan

with y and x (Figure

9-5

).

STEP 2: FINDING THE VALUE ...