As we saw in a previous chapter, the robotic arm we shall consider here consist of two limb sections, the arm and the forearm, connected at a joint, the elbow. The arm is attached at the other end to the body, and the forearm could connected to a hand. The limbs are connected at their endpoints by joints, shoulder and elbow, that are allowed to rotate in a planar motion.
In that chapter we discussed the determination of the X-Y position of the robotic wrist joint given the angle arm makes with the body, the angle that the forearm makes with the arm, and the length of the limb segments.
Here we want to ask the inverse problem. The X-Y position of the robotic wrist joint is given as well as the length of the limb segments and the position of the shoulder joint. Our task is to determine the angle that arm makes with the body and the angle that the forearm makes with the arm.