Question: Single-axis motions of a flexible robot arm could be modeled by a fourth-order system that accounts for rigid-body motion plus the first bending mode:
x1 and x2 represent the angular position and rate of the arm's rigid-body mode, while x3 and x4 represent the angular position and rate deflections due to bending. x1 and x3 add to produce the net position of the end effector y. The bending mode's natural frequency and damping
Ratio are ωn and ζ. A control torque u is applied at the robot arm's hinge point; b2 and b4 characterize the forcing of the rigid-body and bending modes by this torque. Neglecting gravitational and coupling effects, the coefficients of this model are as follows:
(a) Plot the root loci for individual negative feedback of x1, x2, x3, x4, and y to u.
(b) Plot the open-loop frequency response y(w)/u(w).
(c) Generate the corresponding Nyquist plot.