Aerospace and Electronic Systems Magazine July 2018 - 16

A Survey on Quadrotors

Figure 1.

UAV classification [39].

DraganFlyer and XPro. Different cross-configurations are adopted
by other types, as seen in the Convertawings model A, the Piasecki
PA-39, or the Curtiss-Wright VZ-7AP, in which there is no rotor at
the front or the rear but instead two rotors on the right side and two
on the left as presented in [21]. In contrast to the plus configuration,
the cross-style provides higher momentum for the same desired
motion, increasing maneuverability as each move requires all four
blades to vary their rotation speed [55]. However, the attitude control is basically analogous in both configurations as shown in [56].

QUADROTOR MODELS
Quadrotors described in literature have four rotors in a cross configuration. Motors are linked mechanically to the structure and
each propeller is connected to the motor through reduction gears.

Table 1.

Comparison Between Rotary Wings, Fixed Wings, and
Flapping Wings
Rotary
Wing

Fixed
Wing

Flapping
Wing

Maneuver

High

Low

Medium

Cost

Medium

Low

High

Construction
and repairing

Medium

Low

High

Civilian
application

High

Low

High

Military
application

Medium

Energy
consumption

High

Low

Medium

Flight safety

Medium

High

Low

Range

Medium

High

Low

All propellers' axes of rotation are fixed and parallel; they have
fixed-pitch blades and their air flows point down to ensure lifting
upwards. Within these assumptions the structure is quite rigid.

NONLINEAR MODEL
Classical methods used to model the system are Newton-Euler
formulation or Lagrange equation in order to get differential equations. Some researchers went deeply into this representation, while
others used the principal forces and moments and neglected the
smaller ones.
The nonlinear model of quadrotor dynamics has similar development in many works. Researchers consider the forces produced by the four motors, the gravity, the gyroscopic effects, and
drag forces and moments. Obviously, these forces and moments
are enough to give a realistic model for the quadrotor. Several papers for the modeling of aircrafts based on the Euler-Lagrange and
Newton-Euler formalisms are presented in [29], [57 ̶ 61].
In [62], [63], the basic concepts of helicopter aerodynamics are
presented. In [43] an analysis of the Starmac model quantifies several aerodynamic effects relative to the free stream of the vehicle.
These include the total thrust that varies with power input, the free
stream velocity, and the angle of attack, as well as blade flapping
resulting from different inflow velocities experienced by advancing and retreating blades.
References [26] and [40] quantify blade flapping and total
thrust in hub forces and rolling moments for their respective models, the X4 flyer and the OS4, but the importance of the angle of
attack is not mentioned.
Despite the effects of the roll and hub forces and moments,
some researchers do not include hub and roll forces for their controlling models. Reference [40] uses the same model recognized
by others, reaching for a controlled indoor movement for the OS4.
The researchers in [64] demonstrate the importance of the blade
flapping and translational thrust effects while controlling the Starmac in aggressive maneuvers. These researchers added a mathematical representation of external disturbances. An interesting
model that takes into consideration aerodynamic effects in vertical

IEEE A&E SYSTEMS MAGAZINE

JULY 2018

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine July 2018