  This paper proposes a new fraction-order active disturbance rejection
controller based on an improved fraction-order extended state observer (IFESO)
for a class of fraction-order systems. Applying the IFESO, the fraction-order
system can be approximated as an integer-order integrator (1/s). The parameters
that ensure the stability of the IFESO and closed-loop system are provided. The
frequency-domain analysis shows that the IFADRC has a stronger disturbance
estimation performance for the fraction-order system than an integer-order
active disturbance rejection controller (IADRC). The simulation results
demonstrates that the proposed IFADRC behaves better than the IADRC and the
FADRC.
