The transfer functions of speed control for a magnetic tape-drive system an shown in Fig. 4.42. The speed sensor is fast enough that its dynamics can he neglected and the diagram shows the equivalent unity feedback system. Problems 229 (a) Assuming the reference is zero, what is the steady-state error due to a step disturbance torque of 1 N-m? What must the amplifier gain K be in order to make the steady-state error ess