Solution 6.8.2.1 T c (s)= K(s + ) (s +  ;j! d )(s +  + j! d ) :  = ! n =0:85=4 ! d = ! n q 1; 2 =50:6=3: We rst nd  to set the desired steady state error to a ramp, namely zero. Wehave e ss = 1 ;j! d + 1  + j! d ; 1  = 2  2 + ! 2 d ; 1  : For zero steady state error to a ramp wehave 2  2 + ! 2 d ; 1  =0;; or  =  2 + ! 2 d 2 For zero steady state error to a step input wemust have T c (0) = 1;; or K(s + ) (s +  ;j! d )(s +  + j! d ) s=0 =1;; or K  2 + ! 2 d =1;; yielding K =  2 + ! 2 d  substituting our value for  obtained earlier wehave K =  2 + ! 2 d  2 + ! 2 d 2 =2: 1 Then, for this problem  = 3 2 +4 2 24 =3:125 K = 2 =24=8 The MATLAB program omegan = 5 zeta = 0.8 sigma = omegan * zeta omegad = omegan * sqrt(1 - zeta^2) delta = (sigma^2 + omegad^2)/(2*sigma) K=2*sigma tc = zpk([-delta],[-sigma+j*omegad -sigma-j*omegad],K) step(tc) print -deps sr6821.eps t =0:0.01:1;; u=t lsim(tc,u,t) print -deps rr6821.eps generates the step and ramp responses shown in Figure 1 and 2 respectively. 2 Time (sec.) A mp li tu d e Step Response 0 0.5 1 1.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Figure 1: Step response of closed loop system Time (sec.) A mp li tu d e Linear Simulation Results 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Figure 2: Ramp response of closed loop system 3