Journal of Software Engineering and Applications, 2013, 6, 43-47
http://dx.doi.org/10.4236/jsea.2013.62007 Published Online February 2013 (http://www.scirp.org/journal/jsea)
43
Aerodynamic Model Analysis and Flight Simulation
Research of UAV Based on Simulink
Chao Yun, Xiao-Min Li
Department of UAV Engineering, Ordnance Engineering College, Shijiazhuang, China.
Received November 24th, 2012; revised December 25th, 2012; accepted January 3rd, 2013
ABSTRACT
Mathematical simulation method can be adopted to check flight characteristic of UAV, also can be adopted to simulate
hardware experiments of unmanned aerial vehicle (UAV), then related flight experiments can be performed. The simu-
lation method can reduce the flight periods, cost and risk. UAV flight model research play an important role in simula-
tion and modeling in initialize periods of the UAV producing. The study of the paper focuses on the aerodynamic force
modeling work of UAV based on Simulink. The designed model not only can afford mathematics simulation experi-
ment but also will do benefits to the research of flight control, navigation guidance of UAV.
Keywords: Mathematical Simulation; Unmanned Aerial Vehicle (UAV); Aerodynamic Force; Simulink
1. Introduction
The UAV is getting more and more important with its
increasing demand in war, now each country pays more
attention to researching work of UAV, includes the early
researching project, medium-term hardware simulation,
performance validation, and simulation training. All above
mentioned need the simulation research.
UAV plays more and more important role in modern
war, which is a new form of the modern war. The re-
searching work of kinematics characteristic is the basic
work of the UAV system. The research work includes the
simulation of flight track, guideline about and related
techniques and tactics, the validation work through the
simulation operation. Through high fidelity training for
the UAV operator, UAV system will play more and more
important role in its application field and heighten its
fighting efficiency.
2. Simulation Technology of System
Simulation technology is based on conform principle,
information technology and the technique of its applica-
tion fields, it is a new all-around technology which is
adopting computer and other physical equipments, and
make use of related model to do the experiments [1].
System simulation is an experimental method to acquire
information through using the system model or assumed
system. The basic actions of system simulation are mod-
eling, simulation modeling and simulation experiments
and experimental analysis. It not only can offer us ad-
vanced methods to do the research working of analysis,
decision-making, designing and training, but also in-
crease the cognitive ability for the extension inherent rule.
It will promote the progress of the subject form qualita-
tive analysis to ration. Now System simulation technol-
ogy is widely used in the following research areas [2].
2.1. Application of System Analysis and Design
The system simulation technology could do the argu-
mentation and feasibility analysis for the unfounded sys-
tem, and do the basic work for system design. In the
course of the system designing it can do help in building
the model, and optimization designing work; when the
system is built, we could look for optimal control law for
the system through analysis results of the system.
2.2. Application of Theory Research
The theory research of the system mainly depends on
theoretic deducing in the past. Simulation technology can
offer us the useful tool in the theory research, the tool not
only can verify the validity of theory, but also can dis-
cover the system conflicts between theory and reality.
2.3. Application of Professional Training and
Education
It is an important characteristic of the system simulation
adopted in training and education. Now, simulation train-
ing systems have been adopted in many complicated
equipments (e.g., chemical equipment electricity station,
electricity netting) and carrying systems (e.g., airplane,

Aerodynamic Model Analysis and Flight Simulation Research of UAV Based on Simulink
44
motorcar and shipping). They can afford important assis-
tance in heightening efficiency, saving cost and safety
training.
3. Aerodynamic Characteristic Analysis
The flight simulation system designed in paper adopts
modularize method. The primary module includes tele-
control and remote sensing modules, aerodynamic model,
power equipment modules (includes engine model and
propeller model), task equipment module and scene mod-
ule. The aerodynamic module id discussed in the paper.
In above modules, tasks of telecontrol and the remote
sensing module involves decoding the telecontrol com-
mand and code information of remote sensing according
to frame format. Decode the control instructions and ex-
port them to the equipment about power device (rudder
equipment), code the aircraft pose information and in-
formation of task equipment and fill the remote sensing
into the frame.
Aerodynamic module calculates the propeller’s thrust
and torque according to deflexion of the rudder, and then
the calculation results are put into flight dynamic equa-
tion module shown as Figure 1. The flight dynamic mod-
ule is to calculate kinematics equations, the results of the
position and pose will be sent to telecontrol and remote
sensing module. Stabilization module is to strengthen the
stability of the system. Through contrasting the setting
date and module calculation data, then the system can
give the order to rudder to avoid errors.
The core of the flight simulation system is a flight dy-
namic model. The flight simulation dynamic model is
consisted of two parts, one part is computing UAV dy-
namic characteristic, which can gain the aerodynamic
force and moment; the other part is to obtain kinematics
parameters of UAV through calculating 6 parameters
equation [3].
In this module (UAV dynamic simulation model mod-
ule), It should consider all forces and moments includes
gravity, aerodynamic force, engine thrust and various
moments, etc. In the reference frame of airplane, motion
acceleration and angle acceleration should be calculated,
Aerodynamic force
module
Engine module
Propeller module
Fl ight
dynamic
equation
module
Power modu le
Telecontrol and remote sensing module
(telecontrol part)
Telecontrol and remote sensing module
(remote sensing part)
Figure 1. Aerodynamic module of UAV.
we also can add wind disturb and turbulence into in air-
craft reference frame, which are adopted to compute the
parameters of flight track. The angle rate in an aircraft
reference frame can be resolved and transformed into the
ground reference frame, then attack angle and sideslip
angle and their transformation ratio can be calculated,
which would offer to aerodynamic module. The angle
could be decompounded in ground reference frame and 3
Euler angles can be gained by integral, the computing
results could offer attitude parameters to system. UAV 6
degrees of freedom (DOF) calculation flowchart is sh-
own as Figure 2. In the paper, we adopt modularization
method, aerodynamic module is one of the modules in
the simulation system, when the structure of the airplane
is changed, we can rebuild the aerodynamic force module,
others module is unchanged.
3.1. Aerodynamic Characteristic of UAV
In the paper, study on a certain UAV which belongs to
middle or miniature type. Its mass is less than 400 kilo-
grams, the wingspan is about 7 m, the wing area is 4 m2,
flight height is less than 5000 m, and the precise of the
simulation system is according to different purpose. The
complexity of mathematics model is different because
the different simulation purpose. The flight height and
speed is not higher in the project. So according to struc-
ture parameters and experimental purpose, using airplane
dynamic simulation model in training simulator, we can
make the assumption as below:
1) The airplane is rigid body, so we can neglect the
elasticity effect on the body.
2) Mass and CG (center of mass) is constant.
3) Earth is inertia coordinate and assumed geography
coordinate is inertial coordinate;
4) Neglect curvature of the earth.
5) Gravity is constant, as the UAV is flying altitude is
not higher.
6) Assumed the OX axis and axis is in the
symmetry plane of coordinate, therefore .
OY
0
XZ yz
II
Integration of
mo ment
Position kinematics
module
Composition of forceGravity
coefficient Aerodynamic
force thrust
Center of mass
kinematics module
Angle
acceleration
Angle
rate
Motion
acceleration
Motion
rate
Attitude of
the UAV
Location of
the UAV
X
Y
Z
Pitch angle(θ)
Roll angle(φ)
Yaw angle(ψ)
Figure 2. Calculation process of the kinematics equation
with 6 parameters.

Aerodynamic Model Analysis and Flight Simulation Research of UAV Based on Simulink 45
3.2. Characteristic Analysis of UAV
3.2.1. Dynamic Equation
The forces of UAV in the air include gravity, aerody-
namic force and thrust force by the engine. It is shown
that established vector equation in the reference of air-
craft is the simple and convenient Aircraft coordinate is a
dynamic coordinate, it have displacement moment and
rotating moment, the moment equation in aircraft coor-
dinate is expressed as follows.
d
d
VV V
tt


 (1)
d
d
V
t represents absolute derivative of vector V in ground
coordinate. V
t


represents relative derivative of vector V
in aircraft coordinates.
Its matrix expression is as follows:
0
0
xyzzy
tt
yzxxza g
zxyyx
VVV X
VVVCYC
VVV Z





 

 
 

 

 

 
 g
(2)
t
a
C represents transfer matrix from velocity coordi-
nate to aircraft coordinate.
t
g
C represents matrix from ground coordinate to air-
craft coordinate.
,,
X
YZ are aerodynamic forces of drag, lift and side
force in rate reference frame.
The UAV can receive the moment in the air mostly in-
cludes aerodynamic moment, control moment, crossed
moment, damp, etc.
It is shown that aircraft rotary equation, which sur-
round the center of mass is most simply and convenient
for analysis. It is assumed that aircraft coordinate is dy-
namic coordinate, its rotating angular rate is

, it can
be calculated through (3).
d
d
HH
H
tt


 (3)
Its matrix expression is shown as (4),

1

s
tcd j
p
qIMMMM
r







(4)
In Equation (4),
I
is rotating inertia moment, Mst Mc
Md Mj are aerodynamic moment, control moment, damp
moment and crossed moment. Projection of Mc, Md, Mj in
aircraft coordinate together with Mst are consisted of
multiple moment.
3.2.2. Kinem a ti cs Equ ation
The kinematics equation for the centroid of UAV is
shown as (5),
x
X
g
Ya
Z
y
z
v V
VCv
Vv

 


 

 
(5)
g
a
C represents transfer matrix from rate coordinate to
ground coordinates
Rotating equation of UAV moved around centroid, an-
gular rate of rotating of UAV is established which is rela-
tive to ground coordinate [4].


tan sincos
dd
ddcos sin
dd sincos cos
xbyb zb
yb zb
yb zb
t
t
t

 














 

(6)
,,
x
bybzb

 represent component of the flight angu-
lar rate in aircraft coordinate, respectively, the angular
rate is determined by attitude angle’s rate ddt,

dd,t

ddt

, ddt

is along
g
z axis, ddt

is
along axis and
yddt

is along
x
axis.
Through related analysis we can simply the 6 degrees
of freedom mathematics model for UAV, in order to keep
the precise result we should keep the airspeed and
attack angle
V

of UAV in linear region, which will
keep facticity and reliability of the simulation.
3.3. Dynamic Modeling Based on Simulink
Simulink is a powerful toolbox for dynamic modeling. It
has many advantages such as strong computing ability,
the simpleness of the program, abundant repeating model,
which can transform code in real time with high effi-
ciency. It has an abundant toolbox about engineering,
includes aerospace tool which is adopted in aircraft mod-
eling and simulation. Simulink adopts module design
method, which is very convenient and intuitionist to con-
struct a dynamic model, Aerosim is a whole 6 degree of
freedom modeling toolbox which is developed from the
Unmanned Dynamics company in the Simulink envi-
ronment [5-7]. Using these modules we can construct the
simulation system, choose specific module which we
need and then combine these modules according to dy-
namic data flow. Many modules cannot be used directly,
for example, atmosphere model module, and physical ge-
ography model module and so on. UAV system inside
structure is shown as Figure 3.
4. Simulation Analysis
Simulink and Aerosim toolbox offer several integrated
airplane models, through configuring and setting air-
craft’s parameters, users can specify a certain type struc-
ture aircraft according to template aircraft configuration
cripts, e.g., modify the parameter in Config_template.m s

Aerodynamic Model Analysis and Flight Simulation Research of UAV Based on Simulink
46
S ol ve equat io ns of mo ti on
Inputs Outputs
A erodynam i c Model
E arth M odel
S um forc es a nd m oments
Atmosphere Model
Propul sion M o del
AConGnd
15
RE a rth
14 AGL
13
MSL
12
ECEF
11
Mass
10
E ngCoeff
9
PropCoeff
8
AeroCoeff
7
Euler
6
A ng Acc
5
Mach
4
VelW
3
S ensors
2
S tates
1
Total Mom ent
Faero
Maero
Fprop
Mprop
CGpos
Mcg
Total Acceleration
Faero
Fprop
Mass
Acc
GA Propul si on Sys tem
Control
OutofFuel
p
T
rho
WindAxes Vel
RST
Fprop
Mprop
Omega
FuelFlow
EngCoeff
PropCoeff
E quat ions of Mot i on
Accel
Moment
Inertia
Rearth
Gravity
AConGnd
RST
VelB
Rates
Quaternions
Posi tion
Groundspeed
DCM
Euler
Ang Acc
Earth
Position
DCM
MSL
AGL
AConGnd
Rearth
Requiv
Gravity
MagField
ECEF
mu
Atmosphere
MSL
AGL
Winds
VelB
VelW
DCM
pstatic
OAT
rho
a
WindVel
WindRates
A ir cra ft Ine rti a
FuelFlow
RST
Fuel
Mass
CGpos
Inertia
OutofFuel
A erodynamics
VelB
Wi n dB
Rates
Wi n dR at e s
AeroCon
rho
a
Faero
Maero
AeroCoeff
VelW
Mach
pdyn
RS T
3
Winds
2
Controls
1
Figure 3. Module structure of the UAV system.
(includes aircraft dynamic, propulsion, wing span, iner-
tial parameters, etc.). Running through this script at the
Matlab command prompt, a new aircraft parameter file of
the form filename.mat will be created [7-10]. If we cho-
ose this file with. mat extension and fill it into the UAV
parameters setting dialog box, we will accomplish pa-
rameters configuration.
4.1. Simulation Example One
We make the assumption that the initial height of the
UAV is 1000 m, initial speed is [50 0 0], rudder offset is
0 and the aircraft in ideal conditions (i.e., it flies under no
wind condition), add stabilization control loop Propor-
tional-Integral-Differential (PID) control loop, we can
see from simulation results that the airspeed is steady at
48 m/s with the setting value, in other word, it flies
steady with 48 m/s. pitch angle (theta) is steady at 17˚
with setting value just shown as Figure 4.
4.2. Simulation Example Two
We make the assumption that flight initial conditions of
example 2 are nearly the same as example 1 and only add
wind vector [5 −5 0], i.e., add the lateral direction wind
in the simulation. As known that UAV could encounter
much complicated weather conditions in its flying, and
the variation of air current will affect flight attitudes of
UAV. So the research under wind environment has its
practical meaning. In the simulation results in the Figure
5, it can be found that each flight parameter is instability.
The oscillate frequency of each parameter is accelerated,
in control loop (PID control loop) the output will be sta-
ble at the setting value, but it will oscillate around the
setting value, the condition is as same as the real envi-
ronment.

Aerodynamic Model Analysis and Flight Simulation Research of UAV Based on Simulink 47
Figure 4. Output results of airspeed and angle of pitch.
Figure 5. Output results of airspeed and angle of pitch.
5. Conclusion
In the paper we introduce the development tend and ap-
plication fields of the simulation technology. We do the
research work of aeronautic simulation of UAV flight
control based on characteristic and study on 6 degrees of
freedom aerodynamic model. Modeling and simulation
according to the certain type based on Simulink/Aerosim
toolbox are performed; simulation is done under ideal
condition and wind environment. We also present simu-
lation curve of airspeed and pitch angle. The related re-
sults show that the condition with wind is closer to actual
condition, so our research work can offer the foundation
for establishing UAV training simulator.
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