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138              Chapter 2  Mathematical  Models of  Systems

           E2.13  Consider the feedback  system in Figure E2.13. Com-
                                                                               -  =  0 6 *
               pute the transfer  functions  Y(s)/T d(s)  and  Y(s)/N(s).
           E2.14  Find the transfer  function                                   V 2  =  lV\.
                               Yj(s)                        The variables involved are as follows:
                               R 2(s)
                                                               r(t)  = desired platform  position
               for  the multivariate system in Figure E2.14.
                                                               p{t)  =  actual platform  position
           E2.15  Obtain  the  differential  equations  for  the circuit  in
               Figure E2.15 in terms of ^  and i 2.            V\{l)  =  amplifier  input voltage
                                                               v 2(t)  =  amplifier  output  voltage
           E2.16  The  position  control  system  for  a  spacecraft  plat-
               form  is governed  by the following equations:   0(/)  =  motor  shaft  position
                        2
                       d p   dp
                            2
                       —f  + -p  + 4p =  B                  Sketch  a  signal-flow  diagram  or  a  block  diagram  of
                       dt 2   dt                            the  system, identifying  the  component  parts  and  de-
                                  Vi=r-   p                 termine the system transfer  function  P(s)/R(s).


                                                       W







                                                                                     Ms)


                       FIGURE E2.13  Feedback system with measurement noise, A/(s), and plant
                       disturbances, T d(s).





                                                                          Hl(5)

                                              +  r~\             +x~
                      «.(*)    Gfr)             v        G 2(s)           Gjlis)    "•  W
                                               +                 + 1  k

                                       G 7(s)   G%(s)    G 9{s)
                                                          i  k

                      R 2(s)   G 4{s)  -iF—  G 5{s)                       G b{s)    •  Ki(.V)
                                         k

                                               H 2(s)


                      FIGURE E2.14  Multivariate system.
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