Robot Environment for Combat 
Vehicle Driving Simulation
Doc. dr. Roman Kamnik, univ.
dipl. inž., University of Ljubljana,
Faculty of Electrical Engineering,
Slovenia;
dr. Miha Ambrož, univ. dipl. inž.,
University of Ljubljana, Faculty
of Mechanical Engineering, Slo-
venia;
Peter îepon, univ. dipl. inž., Uni-
versity of Ljubljana, Faculty of
Electrical Engineering, Slovenia
dr. Jernej Kuželiïki, univ. dipl.
inž., Iskra Avtoelektrika d.d.,
Šempeter pri Novi Gorici, Slovenia
prof. dr. Ivan Prebil, univ. dipl.
inž., University of Ljubljana, Fa-
culty of Mechanical Engineering,
Slovenia;
prof. dr. Marko Munih, univ. dipl.
inž., University of Ljubljana,
Faculty of Electrical Engineering,
Slovenia
Roman KAMNIK, Miha AMBROŽ, Peter ČEPON, Jernej KUŽELIČKI, 
Ivan PREBIL, Marko MUNIH
Abstract: This paper presents a driving simulator of a combat vehicle aimed for driver-vehicle interaction study and
design of full scale driving simulator. The simulator consists of a real-time combat vehicle dynamics simulation
module, a graphical presentation module, a robotic seat motion system, and a force feedback steering system. The
simulation module simulates dynamic motion and interaction with environment of a combat vehicle in real-time.
The graphical presentation module generates driving scenes that are displayed on a screen by a back projection.
The robotic system generates seat motion cues by the help of a three degree-of-freedom hydraulically driven
mechanism. The force feedback steering system is an interface between the driver and the simulator. In the paper
the configuration of the driving simulator and the results of experimental evaluation are presented.
Keywords: Driving simulator, combat vehicle dynamics, robotic seat, force-feedback,
ronment. The driving simulator is a
tool that gives a driver impression
of maneuvering an actual vehicle
by predicting vehicle motion cau-
sed by his input and feeding back
corresponding visual, motion, audio
and proprioceptive cues. Driving
simulators originate from the aircraft
industry, however, automotive in-
dustry currently deeply relies on their
exploitation. Most sophisticated are
the driving simulators from Daimler,
Ford, Honda, Renault and Toyota au-
tomotive companies. Simulators are
being used for training in normal and
critical driving conditions, analysis
of the driver responses, and evalua-
tion of user performances in different
conditions [1]. Important role have
the driving simulators in military
applications since they create a vir-
tual proving ground for engineering
evaluation of combat vehicles and
driver performances.
This paper presents a prototype dri-
ving simulator for six-wheel combat
vehicle. The driving simulator was
developed in the framework of feasi-
bility study that investigated the po-
ssibilities of subsystems integration.
 1 Introduction
Driving simulators are being used
effectively for vehicle system deve-
lopment and human factor study by
reproducing actual driving condi-
tions in a safe and controlled envi-
In the first part of the paper the con-
figuration of the developed simulator
is described, while in the second part,
the results of experimental evaluation
are presented.
 2 Confi guration of driving 
simulation environment
The configuration of robot environ-
ment for combat vehicle driving
simulation is presented in Figure 1.
The simulation environment incor-
porates four main modules. In simu-
lated driving, the driver maneuvers
the vehicle in computer model via
active steering wheel. Vehicle mo-
tion dynamics and interaction with
environment is calculated on-line in
real-time. Based on calculated va-
lues the computer graphics presents
the vehicle in 3D environment what
provides visual feedback, while the
two robot systems provide sensatio-
nal (haptic) feedback to the driver.
The haptic feedback to the driver is
presented by the hydraulic robotic
seat that provides vertical driver seat
motion and the steering wheel system
that generates the wheel aligning
torque on the steering wheel. Each
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particular simulation environment
module is described in details in the
following chapters.
2.1 Simulation model of com-
bat vehicle
The simulation model of combat
vehicle incorporates the model of
vehicle dynamics, the model of
vehicle powertrain and propulsion
system, the model of braking system,
the model of steering mechanism
and the model of vehicle - terrain
interaction.
The model of vehicle dynamics is
multibody-based and modelled using
the Open Dynamics Engine. The
vehicle is represented as a multibo-
dy system consisting of bodywork
and four to eight wheels. The setup
of a six-wheel vehicle is shown in
Figure 2. The wheels, together with
suspension elements, are connected
to the bodywork with double-hinge
joints. The unsprung mass consists of
wheel mass and suspension elements
mass [2, 4]. Spring and damping cha-
racteristics of each wheel suspension
are modelled by assigning the joint
characteristics. Since the wheels are
modelled as rigid bodies, the tyre
spring and damping characteristics
are computed separately and mecha-
nically combined with suspension
characteristics.
The powertrain is modelled as the
system of a generic wheeled vehicle
that in general consists of the engi-
ne, clutch, main gearbox, reduction
gearbox, differential gear(s), and
hub gears. Each power transmis-
sion element transfers torque and
shaft angular velocity according to
its transfer function.
The braking system of the vehicle is
modelled as a source of tangential
force on the braked wheels, the
amplitude of which depends on the
position of the brake pedal as user
input. Braking force can be indivi-
dually applied to each of the wheels.
The simulator provides a basic model
of braking force reduction on the rear
axle depending on the normal force
on the rear axle. A simple model of
slip-detection based anti-lock brake
system is also implemented.
The steering system of the vehicle is
modelled as a transfer function that
transfers the steering wheel rotation
angle as user input to rotation angle
of the individual steered wheel. The
model provides means of modelling
of kinematic steering mechanism
and its steering angle difference to
fulfil the Ackerman condition. All
the steering mechanism geometrical
characteristics found on real vehi-
cles (camber angle, castor angle,
toe-in angles etc. are also modelled
[2, 4, 3]). Transfer functions for stee-
ring can be assigned for each axle
of the vehicle separately. In this way,
it is possible to model vehicles with
unconventional steering systems
(e.g. rear wheel steered fork lifts or
vehicles with four wheel steering as
shown in Figure 4).
Terrain is modelled as a triangle mesh
and used in collision algorithm to
Figure 1. Confi guration concept of robot environment for driving simulation
Figure 2. Vehicle multibody model 
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excitate the vehicle dynamics model.
The ODE collision detection system
is used to determine the contacts
between vehicle parts and the terrain
geometry. The shape of the terrain
triangle mesh is arbitrary and without
restrictions for triangle dimensions.
This way, the memory required for
storing triangle data and the number
of vertices used in collision detection
can be effectively reduced in the
”flatter” areas of the terrain, whilst
the more agitated areas can be repre-
sented by a larger number of triangles
providing more accurate simulation.
The point data to generate the terrain
mesh can be obtained from various
sources. These include field measu-
rements and GIS data for existing real
terrains, or different 3D modelling
techniques for artificial terrains. The
forces that occur on the tyre-driving
surface contact depend on many
factors, of which the most significant
are the longitudinal wheel slip and
lateral wheel slip angle. These two
quantities are computed for each
wheel in every simulation step. The
forces are modelled separately for the
longitudinal and the lateral direction
of the wheel [6]. The model also
includes calculation of the aligning
torque on the steered wheels that
Figure 3. i3Drive application scheme
Figure 4. i3Drive main window
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is included into the simulation as
steering wheel centering, i.e. steering
torque feedback.
2.2 Software application for 
interactive vehicle simulation
The simulation models are incorpora-
ted into a software application named
i3Drive that includes components for
display in virtual 3D environment,
modules for polling control devices,
a graphical user interface to control
the application behaviour and com-
ponents for simulation results export.
The advantage of the configuration
is that the user has access to all the
relevant simulation parameters regar-
ding the vehicle, the terrain and the
simulation intrinsics, which makes it
possible to realistically simulate real
vehicles on real terrains. Together
with the possibility of real-time in-
teractive driver input processing this
makes the application useful for vehi-
cle operator training. The structure
of the application is schematically
shown in Figure 3.
The largest part of the application
main window (presented in Fig. 4) is
occupied by the display area where
the vizualisation in virtual 3D envi-
ronment takes place. The user can
control the simulation and display pa-
rameters with menu commands and
toolbars and monitor the simulation
status in the status area. Special care
has been taken to provide easy access
to common tasks such as switching
viewpoints and changing navigation
and simulation parameters.
Simulated vehicle dynamics is pre-
sented in interactive virtual 3D en-
vironment. The user is represented
by the virtual person, or avatar, that
can be controlled independently of
the simulated vehicle. This enables
the user to observe the virtual 3D
environment, and thus the driving
simulation, from different perspec-
tives and different points of view.
The avatar can be attached to the
simulated vehicle to provide the
”driver’s view” or custom views of
parts on the vehicle. To achieve a
better view of the simulated vehicle
when driving on larger driving surfa-
ces, any fixed or moving viewpoint
can be set to automatically follow
the simulated vehicle by rotating the
virtual camera.
From programming point of view the
display system is independent from
the simulation engine and the ma-
thematical model. This is achieved
by running the simulation engine and
the virtual 3D environment display
in separate operating system threa-
ds assuring only synchronization
between the two timers. This way it is
possible to achieve shorter simulation
Figure 5. Control scheme for robotic seat
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intervals to improve simulation accu-
racy and stability while keeping the
display update interval long enough
to ensure display in real time. On
a 2600 MHz Pentium 4 computer
with ATI Radeon 9600 graphics card
at 1024×768 screen resolution the
current version of i3Drive can achie-
ve the shortest simulation interval
of 9 ms at a display frame rate of 25
frames per second when simulating a
four-wheel vehicle on a driving surfa-
ce consisting of 9800 triangles.
The inputs to the vehicle model (stee-
ring wheel angle, gas pedal position,
brake pedal position, selected gear
ratio, clutch state etc.) are delivered
by a control device. The hardware
control devices can range from stan-
dard commercial game controllers
(joysticks and steering wheel/pedal
combinations) to custom made con-
trollers and detailed vehicle cockpit
mock-ups. The software for driving
external actuators are built into the
control device and the simulation
data are used to provide motion and
force feedback to the user.
2.3 Robot system for seat 
motion simulation
Active driver seat is in the simulation
environment realized by the use of a
robot device developed for training
of standing-up [5]. The standing-up
robot device is a hydraulically driven
3 DOF mechanism, which in a way
of supporting the subject resembles
half of a seesaw. The driver is sup-
posed to seat on a standard bike seat
mounted at the robot end-effector.
The robot configuration enables an
arbitrary seat motion restricted to a
subject’s sagittal plane. Positioning
of the end-effector is accomplished
by movement of the two robot seg-
ments. The first segment is rotating
around its axis in a robot base, while
the second translational segment
is moving longitudinally along the
first one. Both segments are driven
by linear hydraulic actuators. At the
robot end-effector the orientational
mechanism is mounted assuring ho-
rizontal seat orientation in any robot
position. Constant seat orientation
is maintained by a passive hydraulic
bilateral mechanism.
The standing-up robot mechanism
is driven by an electrohydraulic ser-
vosystem presented in Figure 5.T h e
system is powered by a hydraulic
pump providing the pressure of 50
bars and the hydraulic current of
1 l/s. The pump performances allow
the maximal speed of the robot
end-effector up to 2 m/s. Two Moog
D641-3 servovalves with incorpora-
ted electronics are used to control
the pressure difference applied to
the linear hydraulic cylinders driving
both links. The robot device opera-
tes in the position control mode of
operation. In this mode, the con-
trol objective is to guide the robot
end-effector along the desired path
specified via TCP/IP connection in
terms of velocity and/or acceleration
at each point.
Control system of the robotic device is
implemented in two levels (see upper
part of Fig. 5). At the lower level, the
hydraulic servosystem is controlled
by a target computer built upon a
1 GHz PC Pentium III platform. On
the platform, the xPC Target real
time operating system is running at
a constant sampling rate of 1 KHz.
Two PCI interface boards are used in
this controller to interface the exter-
nal hardware. The PCI-DDA08 board
(Measurement Computing, Inc., Mid-
dleboro, USA) acquires the analog
force and pressure signals, and reads
the joint positions via digital inputs.
The joint positions are assessed by
the help of rotational incremental
encoders interfaced via HCTL 2016
integrated circuits (Motorola, Inc.,
Anaheim, USA). Another Measuring
Computing board type D/A PCI-
DAS1002 is employed to drive the
hydraulic servovalves applying the
output voltage in a range of ±10 V.
At the higher level, an additional
computer is used as a host platform
for robot system programming, super-
vision, data logging and control. The
environment is based on Mathwork-
Figure 6. Force feedback steering
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sMatlab software with Simulink, Sta-
teflow and xPC Target toolboxes. The
configuration allows the development
of control algorithms in graphical
mode by building and connecting
functional blocks what provides user
friendly graphical software develop-
ment environment, optimal tuning of
parameters, and easy acquisition and
logging of signals.
2.4 Force Feedback Steering
For the implementation of force feed-
back steering an Iskra AML 7103
induction motor is directly coupled to
the steering wheel (see Figure 6). This
direct drive configuration can pro-
duce up to 38 Nm of zero backlash
torque. Consequently, high resolution
torque generation enables a realistic
driving sensation. The AC motor has
an incremental sensor bearing in-
corporated with resolution of 192
pulses per revolution. The sensor is
used for acquisition of steering wheel
angle. The AC motor is controlled by
Iskra AES1134 controller that is rated
at 24 V and has a maximal output
current capability of 400 A.I nt h e
controller, a DSP processor performs
indirect field oriented torque control
at 10 KHz.
Fast CAN interface is implemented
for communication between motor
controller and superior xPC Target
controller. The application uses ma-
ster-slave principle of communication
where the target computer behaves as
a master device and the AC motor
behaves as a slave device on the bus.
CAN messages, that can be up to 8
bytes of data long, are transferred
with maximum speed of 1 Mbit/s al-
lowing that the xPC Target operating
system to be running at a sampling
rate of 1 KHz. Via the CAN bus the
reference torque value is transferred
to the AC motor controller, while the
value of steering wheel angle is tran-
sferred in opposite direction.
 3 Experimental evaluation
In the experimental evaluation of
the robot environment for combat
vehicle driving simulation the expe-
rimental setup presented in Figure 7
was tested. The driving scenario in-
corporated the maneuvering of com-
bat vehicle over an off-road terrain.
The driver maneuvered the vehicle by
the steering wheel system, while the
vehicle motion dynamics and its in-
teraction with the environment were
calculated on-line by the i3Drive sof-
tware. Haptic information about the
vehicle vertical motion and wheels
aligning torque were delivered to the
driver by the help of robot seat and
force feedback steering system. A
back projection screen was used for
providing visual feedback about the
vehicle environment in 3D space.
In Figure 8 a vertical position of the
vehicle chassis is presented as an
input to the driver seat subsystem.
From the input, the vertical seat
Figure 7. Experimental evaluation of robot environment for combat vehicle 
driving simulation
Figure 8. Driver seat vertical motion
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position was calculated (see dash-
dotted line) and delivered to the robot
controller. As shown by the graph, the
robot controller provided accurate
tracking of the reference signal.
Figure 9 presents the steering input to
the vehicle model that was acquired
by the steering wheel angle sensor
during simulated driving. The wheel
interaction with the terrain during
cornering was calculated as a wheel
aligning torque. The aligning torque
(presented in graph by a solid line)
was delivered to the steering wheel
torque controller as the torque refe-
rence.
 4 Conclusions
This paper describes the design and
evaluation of the robot environment
intended for driving simulation of
combat vehicle. The simulation en-
vironment is based on the detailed
simulation model of combat vehicle
dynamics, the graphics display, the
robot seat and the force feedback
steering system.
Driving simulation in military appli-
cations provides a safe virtual envi-
ronment in which driving behavior
experiments can be conducted that
are impossible to undertake in real
environments because of potential
risks to subjects or vehicles. Driving
simulation is also important for vir-
tual prototyping of new vehicle de-
signs that, for example, arises from
changes in vehicle configuration and
driver training in such situations.
The developed simulator serves as
a prototype testbed for the study of
simulation capabilities and the pos-
sibilities of software and hardware
modules integration. Based on the
presented results, a high-fidelity
combat vehicle simulator is planned
to be developed.
References
[1] Ambrož, M., S. Krašna, and I.
Prebil. 2004, 3D Road Traffic
Situation Simulation System.
Advances in Engineering Soft-
ware, Vol. 36, pp. 77-86.
[2] Blundell, M. and D. Harty. 2004.
The Multibody Systems Ap-
proach to Vehicle Dynamics, El-
sevier Butterworth-Heinemann,
Oxford, UK.
[3] Genta, G. 1999. Motor Vehicle 
Dynamics, Modelling and Si-
mulation, World Scientific Pub-
lishing, Singapore, 1999.
[4] Gillespie, T. D. 1992. Fundamen-
tals of Vehicle Dynamics, SAE
Inc., Warrendale, PA, USA.
[5] Kamnik, R. and T. Bajd. 2004.
Standing-Up Robot: An Assistive
Rehabilitative Device for Tra-
ining and Assessment, J. med.
eng. technol., Vol. 28, No. 2,
pp. 74-80.
[6] Pacejka, H. B. 2002. Tire and 
Vehicle Dynamics, SAE Inc.,
Warrendale, PA, USA.
Figure 9. Force feedback steering
Robotsko okolje za simulacijo vožnje bojnega vozila
Razširjeni povzetek
Simulator vožnje je sistem za simulacijo upravljanja realnega vozila v varnem in kontroliranem okolju. Namen
simulatorja je, da vozniku ustvari obïutek upravljanja z realnim vozilom v realnih voznih razmerah. To je izvedeno
s pomoïjo doloïitve gibanja vozila na osnovi upravljalnih komand ter posredovanjem ustreznih vizualnih, slušnih
in taktilnih zaznav vozniku. Simulatorji igrajo pomembno vlogo pri razvoju vozil in študiju akcij voznika. Upo-
rabni so za vadbo vožnje v normalnih in kritiïnih razmerah, analizo odzivov voznika ali evalvacijo uporabniških
lastnosti v razliïnih razmerah. Posebno vlogo imajo simulatorji vožnje bojnih vozil, saj omogoïajo preverjanje
vozila in voznika na navideznem preizkusnem bojnem poligonu.
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V prispevku je predstavljen prototipni simulator vožnje šestkolesnega bojnega vozila, ki je bil razvit v okviru
izvedljivostne študije, katere namen je bil preveriti možnosti integracije posameznih podsklopov simulatorja.
Razviti simulator vožnje bojnega vozila je sestavljen iz simulacijskega modula z dinamiïnim modelom vozila,
grafiïnega modula, robotskega sedeža in haptiïnega volana. Konfiguracija simulatorja vožnje bojnega vozila je
predstavljena na sliki 1. Na simulacijskem modulu v realnem ïasu poteka izraïun gibanja bojnega vozila na osnovi
podrobnega dinamiïnega modela vozila in njegove interakcije z okoljem. Model vozila je naïrtan kot togo telo
karoserije, na katerega je preko vzmetenja vpetih šest koles (slika 2). V modelu vozila so implementirani pogonski
in zavorni momenti, preverjanje zdrsa in prepreïevanje blokade koles. Interakcija vozila s terenom je doloïena s
pomoïjo modela terena, ki ga sestavlja mreža trikotnikov, ter modela in detekcije kolizije med kolesi in terenom.
Simulacijski modul je zasnovan v obliki programske aplikacije i3Drive. Na sliki 3 je prikazana konfiguracija pro-
gramske aplikacije, na sliki 4 pa grafiïni prikaz vozila in okolja v trirazsežnem prostoru, ki je uporabljen za prikaz
na projekcijsko platno. Robotski hidravliïni mehanizem s tremi prostostnimi stopnjami gibanja, predstavljen na
sliki 5, zagotavlja gibanje sedeža, ki je identiïno gibanju sedeža v vozilu med vožnjo. S slike je razvidno, da vse
robotske segmente poganjajo hidravliïni valji, vodeni preko elektrohidravliïnih servoventilov. Regulacija aktivnih
sklepov je izvedena z robotskim krmilnikom, ki je zgrajen na osnovi operacijskega sistema, namenjenega delo-
vanju v realnem ïasu xPC Target. Volan, ki predstavlja vmesnik za upravljanje z modelom vozila, je voden glede
na izravnalni moment upravljalnih koles. Na ta naïin je vozniku posredovana haptiïna informacija o momentih
na volanu, ki delujejo pri upravljanju realnega vozila. Volan je direktno gnan s pomoïjo indukcijskega motorja,
vodenega z direktno regulacijo momenta preko vektorske regulacije magnetnega polja. Konfiguracija sistema
haptiïnega volana je predstavljena na sliki 6. Simulator vozila, robotski krmilnik in krmilnik motorja medsebojno
komunicirajo preko povezave Ethernet z izmenjavo paketov UDP.
Simulator vožnje bojnega vozila je bil preizkušen v laboratorijskem okolju pri vožnji po brezpotju. Testni voznik
je upravljal s simulatorjem preko volana, pri ïemer mu je bila vizualna informacija posredovana na projekcijskem
platnu, taktilna pa preko haptiïnega volana in robotskega sedeža (slika 7). Slika 8 predstavlja gibanje karoserije
in rezultirajoïe gibanje sedeža pri eksperimentu. Slika 9 predstavlja kot vrtenja volana in rezultirajoïi izravnalni
moment.
Predstavljeni simulator vožnje bojnega vozila je zasnovan kot prototipni sistem za preverjanje karakteristik si-
mulacijskega modela in možnosti integracije posameznih modulov strojne in programske opreme za delovanje
v realnem ïasu. Na osnovi predstavljenih rezultatov in opažanj testnega voznika pri eksperimentu je možno
zakljuïiti, da je razvita programska oprema ustrezna in da je realizacija simulatorja bojnega vozila s kompleksnejšo
strojno opremo izvedljiva.
KljuÏne besede: simulator vožnje, dinamika bojnega vozila, robotski sedež, haptiïna informacija,
Acknowledgments
The authors acknowledge the Republic of Slovenia Ministry of Defense and Ministry of Education, Science and
Sport grants ”System for Analysis of Exploitation Capabilities of Army Vehicles” (M2-0126), ”Motion Analysis and
Synthesis in Human and Machine” (P2-0228 C), and ”Modelling in Technics and Medicine” (P2-0109 C).
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