Figure 1 shows an arm which has three joints at O, S and E. The axis of the joint O rotates around axis of coordinates. The axes of joints S and E are vertical to the plane OSEW. Let . Answer the following questions.
(1) Show the equation of the forward kinematics of the arm , where is the position vector of W and is the vector of the rotation angles around the joints O, S and E.
(2) Describe the velocity of the point W by the angular velocity of the three joints O, S and E.
(3) Show the equation of the inverse kinematics of the arm .
(4) Assume a force is applied to the point W. Show the joint torque around the three joints O, S and E in order to keep the posture of the arm.