Make: Robotic Arms

171Chapter 9: Inverse Kinematics for 3D Movement

makes finding the value of our α

2

and



variables

no more difficult than some of our previous

equations in which we used the law of cosines

to determine the angles of a non–right triangle

(Figure

9-9

).

STEP 4: FINDING THE VALUE OF OUR FINAL

α

VARIABLE

Now that we have calculations for both our α

subangles, as well as our



variable, we’re just

about done putting everything together. Our last

step is combining our two α subangles, α

1

and

α

2

. Just as with our previous four-link robot, the

final value of our α variable is dependent on the

position of our end effector (Figure

9-10

).

9-9

9-10