  This paper presents a mathematic dynamic model of a quadrotor unmanned aerial
vehicle (QUAV) by using the symbolic regression approach and then proposes a
hierarchical control scheme for trajectory tracking. The symbolic regression
approach is capable of constructing analytical quadrotor dynamic equations only
through the collected data, which relieves the burden of first principle
modeling. To facilitate position tracking control of a QUAV, the design of
controller can be decomposed into two parts: a proportional-integral controller
for the position subsystem is first designed to obtain the desired horizontal
position and the backstepping method for the attitude subsystem is developed to
ensure that the Euler angles and the altitude can fast converge to the
reference values. The effectiveness is verified through experiments on a
benchmark multicopter simulator.
