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Control Systems ———  139


                       y = lsim (num, den, r, t)                                                    ...(3.66)
                       y = lsim (A, B, C, D, u, t)                                                  ...(3.67)
                   The MATLAB commands in Eqs. (3.64) to (3.67) will generate the response to input time function r or u


                    3.21 RESPONSE TO INITIAL CONDITION IN STATE SPACE

                   Consider the system defined in state space by
                       x    = Ax + Bu, x (0) = x 0                                                  ...(3.68)
                       y = Cx + Du                                                                  ...(3.69)
                   The MATLAB command
                   initial (A, B, C, D, [initial condition], t)                                     ...(3.70)
                   may be used to provide the response to the initial condition.


                    3.22 EXAMPLE PROBLEMS AND SOLUTIONS

                   Example E3.1: Reduce the system shown in Fig. E3.1 to a single transfer function, T(s) = C(s)/R(s) using
                   MATLAB. The transfer functions are given as
                                    1
                            G (s) =   (s +  7)
                             1
                                       1
                            G (s) =   (s + 6s +  5)
                             2
                                    2
                                    1
                            G (s) =   (s +  8)
                             3
                                  1
                            G (s) =   s
                             4
                                    7
                            G (s) =   (s +  3)
                             5
                                       1
                            G (s) =   (s + 7s +  5)
                             6
                                    2
                                    5
                            G (s) =   (s +  5)
                             7
                                    1
                            G (s) =   (s +  9)
                             8

















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