A robot uses feedback to control the orientation of each joint axis. The load effect varies due to varying load objects and the extended position of the arm. The system will be deflected by the load carried in the gripper. Thus, the system may be represented by Figure P4.7, where the load torque is Td(s) = D/s. Assume R(s) = 0 at the index position.
(a) What is the effect of Td(s) on Y(s)?
(b) Determine the sensitivity of the closed loop to k2.
(c) What is the steady-state error when R(s) = l/s and Td(s) = 0?
Figure P4.7
Robot control system.

Load disturbance TKs) Controller Ri) Desired + Actual Joint stTs ) angle