A Low Cost Flight Simulator Using Virtual Reality
Tools
Ilkay Yavrucuk ∗
Middle East Technical University,Ankara,06531,Turkey
Er Kubali †
Aerotim Dynamics LLC.,Ankara,06531,Turkey
Onur Tarimci ‡
Middle East Technical University,Ankara,06531,Turkey
Deniz Yilmaz §
Middle East Technical University,Ankara,06531,Turkey
A simulator is build using Head-Mount-Displays and Data Gloves with trackers to test
the viability of virtual reality tools in flight simulation.The simulator us FlightGear as its
simulation environment.Running veral clone simulations on different computers allowed
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stereo imaging on the HMD and instructor station applications.Data Gloves with trackers
enabled interaction with the virtual cockpit.A Uh-1h helicopter flight dynamics model
is developed,compared with flight test data and ud in the simulator.This experience
has shown that a simulator with minimal hardware,but more intensive software and using
virtual reality tools can be a potential simulator configuration in future,being more realistic
and lower in cost than existing ones.
I.Introduction
厨师帽简笔画
The idea of Virtual Reality (VR)has been the corner stone of simulation dating back to 1965when Ivan Sutherland laid the vision that the visual interface should not be thought of a screen,but rather a window to a virtual world,that looks real,sounds real and reacts in real time.1Several decades later,v
ehicle simulation still relies on big,bulky and expensive environments to enable a believable virtual world:Vision is provided through expensive cameras,almost real life cockpit avionics and pilot controls are mounted on cockpit-like structures and the whole structure is moved by heavy-mostly hydraulic driven-motion platforms.Yet,many short comings are prent.For instance,a 3-D imagery or a 360deg view is ldom available,even in high-end vehicle simulators.As the fidelity of the simulators are reduced,so is the cost and size and its feel to reality.Clearly,a new approach of hardware and software could benefit flight simulators in the n that it would reduce cost and hardware size.Virtual reality tools prent a promising alternative to traditional simulator hardware.廉洁自律情况评价
In Ref.2VR is defined as a virtual reality experience as any in which the ur is effectively immerd in a responsive virtual world.Four crucial technology barriers are mentioned:The visual (and aural and haptic)displays,graphic rendering,tracking system,databa construction of the real world -all of which become increasingly achievable at lower costs.Additionally,synthesized sound,synthesized forces and haptic nsations,devices such as data gloves to interact with the virtual world,and interaction techniques that substitute for the real interactions possible in the physical world are mentioned as supporting technologies.∗Faculty member,Department of Aerospace Engineering.
†Software
Engineer
‡Graduate Student,Department of Aerospace Engineering.
透骨草功效§Currently,Graduate Student at Delft University of Technology,Netherlands.1of 9
AIAA Modeling and Simulation Technologies Conference 10 - 13 August 2009, Chicago, Illinois AIAA 2009-5832
Hardware and software technology has emerged to enable VR in a more compact and affordable form. Pulled by the LCD-device market Head-Mount-Displays(HMDs),for instance,became more affordable with higher resolution,improved color saturation,brightness and ergonomic displays.Similarly,trackers on HMDs and other haptic devices became more accurate.System latency(the latency between ur motion and its reprentation in the virtual environment)has been a major obstacle on most virtual reality systems.A latency of greater than50ms is known to be perceptible inflight simulators.Moreover,the computer graphics generation during the head motion of an HMD is a demanding visual workload,where angular velocities of 50deg/s for a typical head motion are probable.In Refs.3,4flight simulators using some aspects of virtual reality are prented.As time went by,the cost of the tools did reduce and became more available.
The Simulation Control and Avionics Lab(SCALAB)of the Department of Aerospace Engineering of the Middle East Technical University engaged in the development of a low costflight simulator using off-the-shelf virtual reality tools.In particular,an off-the-shelf Head-Up-Display,data-gloves with motion trackers, and joysticks are integrated with realistic physics badflight dynamics models,through the open source simulation environment FlightGear.5Stereo imagery is enabled to obtain a3-D feel.The simulator targets the u of minimal hardware,but still prerves the esntial elements of aflight simulator.It is t-up to remble a Uh-1h utility helicopter with realisticflight dynamics.Theflight dynamics is developed and compared withflight test data.Hence,the resulting simulator is portable,low cost,but software intensive. The critical balance between low cost,less hardware and realistic simulation feel is achieved by using off-the-shelf virtual reality tools along with state of the art simulation software tools.This paper prents a description of the simulator and the experience gained when using virtual reality tools in aflight simulator.
II.SCALAB Virtual Reality Simulator
The simulator consists of a Cybermind hi-Res SVGA Head-Mount-Display Unit with InertiaCube Preci-sion Tracker,65DT data Gloves,7Polhemus Patriot Motion Trackers,8Saitek pilot control stick and pedal t9and three standard desktop PCs(Fig.1).All PCs run on Windows operating systems a
nd Pentium CPUs with relatively high end graphic cards(NVIDIA9600or better).All computers are inter-connected through TCP/IP connections.The data gloves have motion and angular tracking and are connected to the PCs via a tracker receiver ud tofind the glove positions relative to a reference position.The HMD has two individual LCD screens,one for each eye.A motion tracker on the HMD calculates the angular position of the display unit and feeds it back to the computers.The pilot controls are relatively simple joystick controls,with a center joystick reprenting lateral and longitudinal cyclic controls,a side joystick controller for collective control and pedals for the tail rotor control.One of the sliders on the side joystick is assigned to the throttle control.One of the computers(Computer1)receives data from pilot inputs,while data from the HMD and data glove receiver are received by Computer2.Information is propagated between the computers through the TCP/IP connections.Computer1generates the visual image for one of the LCDs on the HMD. Computer2generates the image for the other LCD of the HMD,whereas Computer3is connected to an external LCD to be ud by an instructor.(Fig.2)
设备维修管理A.Visuals
The simulator features synthetic visuals of the environment as en from a pilot’s cockpit view.The pilot has a360deg view of the cockpit interior and the outside through the HMD Unit,including pilot co
ntrols, cockpit instruments,main rotor rotation etc.The visual environment is integrated through the FlightGear open source simulation software(Figure3).The aircraft visual models complete with avionic displays,pilot controls,rotors,etc.are custom added.The visuals also feature models of human hands to provide a synthetic view of the pilot hands’position.The synthetic hands are moved in the simulation,bad on the movement of the data gloves.This allows the ur to touch and move controls both in the real world and in the synthetic environment.Moreover,the pilot can reach to the instrumentation panel and interact with the synthetic world by pressing buttons on the cockpit panel.The visualization of the real world outside the cockpit is ud as is available in FlightGear.Computer2is synchronized with Computer1and is t up to also run a dummy FlightGear information to move the aircraft model is received from Computer1through the TCP/IP connection.The aircraft’s angular and linear positions are calculated through theflight dynamics model in Computer1.Therefore Computer2acts as a clone of Computer1and is a client to the rver computer.
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Figure1.SCALAB Virtual Reality Simulator
FlightGear allows the ur to situate a camera to any desired position in the simulation.The camera
positions of Computer1and2are t slightly different from each other to create a stereo image on the HMD.The images generated in each computer are projected onto the LCD screens of the HMD.The camera positions are t a few inches apart with a few degrees angle allowing the ur to focus into the cockpit instruments.This allows the ur to perceive depth in the objects in the simulation.The tracker on the HMD is fed as a signal to Computer2and the camera positions of both Computer1and2are updated in the simulation display projected to the HMD.Hence,the ur can view a360deg view by rotating the HMD. The TCP/IP connection allows a distributed simulation environment with multi-urs and more computers for other displaying purpos.In this ca,a third computer(Computer3)is t-up rving as an instructor station,allowing an instructor to guide the ur.Usually the view on the instructor station would be the view of the helicopter through a chasing camera.It is possible to extent this by connecting more computers through TCP/IP connections,each providing different views of the simulation.A common request would be the view of the cockpit panel.
八月十六B.Pilot Controls and Data Glove Tracking
The data gloves on each hand are ud to allow the ur to interact with the cockpit.The data gloves’positions relative to a reference position and their angular positions are calculated in real time and provided to Computer2.The positions of the pilot controls are calibrated to match with tho in th
e visual environment. Therefore the ur can e the synthetic image of his/her hands and reach to touch the controls(Figure4). The visual controls remble one of a real helicopter,whereas the actual pilot hardware are simple joysticks. The movement of the controls along with the synthetic hands are also displayed.The relative movement of the controls and the synthetic hands match with the actual physical movement of the joysticks.A calibrated fixed simulator asmbly is ud to adjust and t the relative movement of the different objects.The pilot can also reach to the cockpit panel,press a button or touch objects in the virtual environment(Figure5).
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Figure2.Block diagram for the SCALAB Virtual Reality Simulator
教育孩子的心得
C.Flight Dynamics Math Model
A nonlinear helicopterflight dynamics model of the Uh-1h is generated and compared withflight test data. The model is generated by improving on thefidelity of the minimum complexity helicopter model.10A major improvement of the updated model is that it includes the Peters-He inflow distribution model with a blade element approach for the main rotor force-moment calculations.
The following additional modifications are done on the minimum complexity model to improve the model fidelity:The Uh-1h has a shaft-mounted stabilizer bar on the main rotor mechanism.A stabilizer bar is a mechanical augmentation device which increas the damping of the system,hence,affecting the stability and control characteristics of the helicopter.A stabilizer bar model is added into the simulation.The tail rotor model calculations consist of iterations for thrust and induced velocity.A robust iterative method is added for convergence even at high yaw rates.12Moreover,in the updated tail rotor iterative calculations the blockage effect of the vertical tail is also included.Both vertical tail and horizontal tail are modeled with incread accuracy.The mechanical linkage between pilot control and the incidence angle of the horizontal tail is modeled ac
cording to data given in Ref.11.Moreover,lift and drag calculations are bad on2-D wind tunnel tests of airfoils.13The calculations include the effect of Reynolds number and covers the whole angle of attack spectrum from-180to+180,thus including the effect of reverflow on the
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Figure3.FlightGear integrated virtual environment
Figure4.Synthetic Pilot Controls Figure5.Cockpit Synthetic Instrumentation aerodynamic surfaces.The updated model also includes aerodynamic derivatives of the Uh-1h fulage.11 For the treatment of ground effect,an approximate formula bad on Cheeman and Bennetts analysis is ud14and an additionalfit is done to reach a better agreement withflight test data available in literature.15 Although not available in the real helicopter a simple rate feedback Flight Control and Augmentation System is added to eaflight when desired,but can be switched ON and OFF.
1.Trim
In Refs.16and17,trim values of main and tail rotor pitch,longitudinal and lateral swash plate angles are given for the Uh-1h helicopter for various forwardflight velocities.The trim values for both the minimum complexity and the updated model are found and compared against theflight test data.In the following figures the abridgment’Min.Comp.Mod.’and’Upd.Mod.’refer to minimum complexity model and updated model,respectively,where the updated model refers to the higherfidelityflight dynamics model as described above.
Figure6shows the trim values of the collective control.Both the minimum complexity and the updated model have similar trim values of root pitch angles of main rotor blades.
典狱司歌词Figure7shows the trim values of the tail rotor control input.Here,although both models have clo root pitch angles of tail rotor blades for increasing velocities,there is a slight difference between the simulation model results and test data.Especially,at high velocities the simulation models require higher pedal input
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Figure6.Root pitch angle of main rotor blades in trim vs forward velocity Figure7.Root pitch angle of tail rotor blades in trim vs forward velocity
Figure8.Longitudinal swash plate angle in trim vs forward velocity Figure9.Lateral swash plate angle in trim vs forward velocity
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American Institute of Aeronautics and Astronautics
