  To handle the control difficulties caused by high-order dynamics, a control
structure based on fractional order [proportional integral] (PI) controller and
fractional order Smith-like predictor for a class of high order systems in the
type of K/(Ts+1)n is proposed in this paper. The analysis of the tracking and
disturbance rejection is illustrated based on the terminal value theorem and
shows that the proposed control structure can ensure that the closed-loop
system converges to the set point without static error and the closed-loop
system recovers to its original state when the input disturbance occurs. Then,
simulations about the influence on the control performance and control signal
with different are carried out based on multi-objective genetic algorithm
(MO-GA). The results show that the control performance can be improved and the
energy of the control signal can be reduced simultaneously when the order is
chosen no more than one. This can verify that the fractional order Smith-like
predictor with has an advantage over that of the integral order Smith-like
predictor.
