Flight Simulation - Science topic

Hello sir,

I just came to see this right place I have been flying sim for a long time more than 6+ years starting from fs2002 till Fs2020. I am curious and while reading the answers and Alexandros Kontotasios thanks for connecting with such a question. I am interested like do someone works on the FS2020 simulator for any research purpose. Please share if any.

You can find your answer in this page:

Best regards

Dear Neil,

Could you simulate this problem?. Actually I am trying to simulated same type of problem in which due to rudder 's deflection some additional forces act on aircraft and aircraft with rotate or turn with moving constant speed so direction of aircraft 's velocity change. Here my questions are - How did you combine the effect of 6 DOF on aircraft's moving direction? Did you write 2 UDFs separately for CG Motion & 6 DOF or in one UDF that is 6 DOF UDF you combined the effect of aircraft rotation due to 6 DOF?

Can you please help me in this. If possible, Please share your UDF with me. My all doubts will be clear by your UDF.

Thanks for your help.

Regards,

Bhupendra

Please treat simply as an open turbomachinery rotor and see tutorial for axial machine

You are welcome.

Thanks @Paulin Kantue

The answer is actually quite simple: the task of flying is even three-dimensional, because the pilot can determine speed (= location in the longitudinal direction), turn flight (= position in the lateral direction) and height (= position in the vertical direction). Due to the characteristics of the aircraft and the aerodynamics these 3 directions are coupled with each other (this is not unlike the car, with which a two-dimensional task can be fulfilled - position in the longitudinal direction and position in the transverse direction on the road surface - and where also the movement in longitudinal and transverse directions due to the driving physics are coupled together).

In a certain manner independent of definition of the task is the type of technical realization: with flying by means of a joke or a two-dimensional joystick, at least the task can be met in transverse and high direction by a single control element, whereas speed is separately influenced by control of the engines. From an ergonomic point of view, ideally the dimensionality of the control element should match the dimensionality of the task.

In order to answer your question, it is necessary to distinguish between the dimensionality of the task and the dimensionality of the influence of the respective vehicle, which, due to the technical realization, do not have to coincide with each other.

In terms of other companies, I strongly suggest Ehang, a Chinese company. Here is its website:

Thank you Dear Dr. Morteza Esmatparast

Your information to give me about my equation  was excellent and valuable

Regards

Malik N Hawas

In my opinion, you should first get to know the applied frequency of your plant (the steering dynamics of the aircraft you are to design a control loader for). Then you should tune the passive and active control parameters of your controller such that it synchronizes with your plant (to act at a similar time-constant (rate) of the real aircraft primary control steering handling (or time response)). Therefore, as I see you should first ponder the dynamic characteristics of the real aircraft you are trying to build a control-loading system for. It means, it differs to design control-loader for a passenger or military aircraft which are respectively slow and fast (agile), meaning they operate at different frequencies. Hence, you should keep in mind that the frequency of the controller (both passive and active control) of your simulator control loading system should be in the range of the natural frequency of the real aircraft you are trying to build a control-loading simulator for. The controller and the plant (hardware) should synchronize or harmonize.

Hi,

To my knowledge, TVC is already used in Russian fighter jets like Sukhoi MKIII. If you are aiming to work on the same either experimental (Which I feel will be very expensive) or CFD, proper validation is definitely required. 

You can try using some CFD codes and provide the validation with some good experimental data already available or through any valid journal.

If you are using any commercial CFD codes such as ANSYS Fluent, I will be happy to help you further.

Information on the UH-60 Black Hawk model is available on Howlett, J. J., "UH-60A Black Hawk engineering simulation program. Volume 1: Mathematical model", NASA-CR-166309, 1981. You would have to check if the horizontal stabilizer formulation and charts can be used.

http://www.amazon.com/Aircraft-Dynamics-From-Modeling-Simulation/dp/0470626674 

Aircraft Dynamics: From Modeling to Simulation 1st Edition

by Marcello R. Napolitano (Author)

You can find detailed aero, mass, and prop data for your simulation 

Cross wind consideration is required at the low speed operation such as take off and landing.At the conceptual and preliminary design stage, this effect needs to be considered to check the size of vertical tail

It depends on how big your aircraft is, there are the specified regulations on cross wind for UAV, LSA, VLA, FAR23, FAR 25 etc...Normally in Subpart B 

One idea that is low cost is using Xplane 10's aerodynamic capabilities to evaluate.

Thanks, John, for the remark on pressurized and/or cryogenic testing, since this is the only way to get Mach and Reynolds number similarity for down scaled models - unless you change (theoretically) the flow medium (e.g. a water tunnel gives you easily Reynolds number similarity - but no Mach similarity except for real incompressible flows at M<<0.1).

Nevertheless, if you are limited by the available wind tunnel facility, it is probably more important to match the Mach number similarity and accept that you will measure higher friction forces (drag) than to be expected for the real aircraft. There are some extrapolation methods around (see some AGARD reports on wind tunnel testing) to estimate the drag variation. When it comes to flow separation the situation gest more complicated, although proper transition tripping will help to eliminate low Reynolds number artefacts. Anyhow, these measurements will not give you absolutely accurate values, but e.g. to compare designs it is mostly sufficient.

One remark to the answers above:

@Aziz: your comment may hold for bodies where the drag is mostly related to pressure drag only. For bodies where the drag is dominated by friction forces, your comment that CD doesn't significantly change between Re=1000 or Re = 10 mil. is definitely wrong.

Will your project include flocking, or is it restricted to modeling how wings beat?

I've done this using Mathematica (picture attached). But the DEM only gives a rather sparse array of elevations. These have to be converted into polygons, and then texture added to give an illusion of realism, if you want to simulate lowj-altitude flight. It's quite complex. Most flight simulators use denser elevation arrays, which they have to purchase at quite a high price, and then develop proprietary display methods that they want you to pay for, because they have so much work invested in developing their graphics code.

Is there a reason you can't use open-source simulator code such as FlightGear?

Great discussion already going on... Just a couple of additional thoughts on purely manually controlled flight. In essence, the pilot inputs are dependent on an interaction of three control circuits in accordance with the control and performance concept in instrument flying. Pilot control inputs are made to affect a known pitch, power, and heading change on the control instruments (ADI for pitch and bank input, Engine Instruments for power inputs), which constitutes the first control loop of input, resultant effect, and feedback and in fully manual flight depends greatly on speed and control surface effectiveness, while in automation assisted flight (such as flight control computer, auto-throttle, etc...) will be much simpler (because, for example, the flight control computer will handle stick inputs as desired pitch or bank angle requests rather than actual control surface deflection inputs). The pilot will continue to manipulate controls until the desired control instruments match expectations, and will then continue corrections to hold those inputs.

Then in a second control loop, the effect of the pitch,bank, and power inputs is assessed on VVI, ASI, and HSI to meet desired/planned numerical results for the anticipated flight condition (i.e., the planned ILS glidepath, course, and approach speed). This second loop just establishes that control inputs of the first loop had desired performance results and will feedback into the first loop to make known/distinct corrections if necessary. What this second loop doesn't do yet is correction for the actual ILS, which is part of a third loop that feeds back into the second control loop.

In the third loop, resulting deviations to ILS glidepath and course are assessed, determining the effect of desired/planned vertical speed, heading, and airspeed. Deviations from course or glidepath are translated into required corrections for heading and vertical speed and are fed back into the second loop as new desired/planned numerical values for those. Since that will result in a deviation within the second loop, it will in turn be translated back into the first loop to establish known pitch, power, and bank inputs to meet the newly desired VVI and Hdg values.

When making corrections, the pilot should in general follow a dampened oscillation curve; i.e., teaching manual ILS flying, I would recommend halfing of corrections: For example, if a certain hdg drifted us of course and a hdg change of six degrees corrects us back to course, I would recommend to take half of that correction out and leave three degrees correction in as the newly desired hdg to hold course; if that in turn slowly drifts us to the other side, I would take the three degrees out until back on course and then re-establish half of it (1.5deg) as new on-course hdg. Similar for required VVI updates...Also, when making the required control inputs, the pilot has to be aware of and make known corrections; e.g., for above small value hdg changes, I would recommend a bank angle equal to the hdg change amount, which keep the amount of time that input has to be held roughly the same for all corrections...

This use of a second intermediate control loop is in contrast to automated control inputs such as flight director bars, which cut out the requirements to establish new headings and VVIs and directly translate ILS deviation inputs into bank and pitch steering commands. Therefore, a FD will do dynamic control input corrections while manual flying requires incremental, but discrete inputs that are held for a certain amount of time. The biggest mistake students new to manual instrument flying will make is to try dynamically doing corrections - i.e. chasing the needles...

I hope that perspective from the training side may help as input.

it is a solution of differential equation considering or neglecting damping and stiffness coefficients. your control gives the time response of the displacement at constant or variable force, but if you want force/displacement curve you should eliminate the time by rearranging the equations

See the attached document if it is of some help.

There's also an ESDU data sheet dedicated to Propeller effects, ESDU 85015.  Even though the title says effects on lift and drag, it also includes methods that can be extended to yaw.

number of articles on the sub. question are available. interested person may refer to it to understand the solution thoroughly.don't look for short cuts.

I just want to what Robert has said above. Modeling the plant (Aircraft or anything you want to control) is the corner stone of the controller design process. As much as the model is close to the physical plant eliminating any uncertainties, as much the controller can be made robust  in terms of performance and stability.

This basic understanding has led to many important work to:

1- Produce "High Fidelity Models" that mimic the physical plant. Normally, they are nonlinear and covers the actuators and sensors plus any structural dynamics that will impact the aerodynamic model.

2- The nonlinear model either is used directly to develop the nonlinear controller using design methods such as Sliding Mode Control (SMC) or Backsteping or Nonlinear Dynamic Inversion.

3- Else, the nonlinear model is linearized by using Taylor Expansion or using non-local methods such Linear Parameter Varying (LPV) method and subsequently linear design methods are used to design the controller such H-infinity or mu-Synthesis or other methods.

4- To ensure a more robust control, the propulsion is integrated with the airframe (rigid dynamics) to base the design on an integrated flight and propulsion (IFP)

5- Once the design is over, what you will load into the computer is the controller and not the model as the physical plant will replace the model used during the design. So if the model was comprehensive =  "High Fidelity Model", then the controller will produce the results during flight simulation which are same as during desktop simulation.

I hope the above sequence and last point (#5) helps to clarify the confusion.

I don't know much about the other sims, but X-Plane lets you access simulation data via UDP. Two of my students wrote an interface which we could use to get sim outputs and write sim inputs. The number of accessible states / parameters is fairly comprehensive.

You'll find information about the protocol at http://www.nuclearprojects.com/xplane/xplaneref.html

Cheers,

Marc

Hello Menconi.

Maybe these materials can help you.

Hello,

i don't think that the three elements are the same. Model-in-the-loop is used to simulate the model and to see if the functionality of the model is correct. Rapid Prototyping can be used to execute the code that is generated from the model (e.g. with a code generator) but it also has a generic hardware where the code is executed. So there is a difference to the model-in-the-loop where no hardware is available. Software simulation is i think the execution of the whole software on the target environment. Therefore you will also see some difference results there.

Best regards

Jan

Sorry for this late answer, I just see the question ;-). XFRL5 is interesting to begin. After that, probably one of the most complete open source CFD code is probably OpenFoam (see http://www.openfoam.com/ for the latest version) No so simple if you are at the begining but really powerful. Probably the best is to begin by some exercices like a NACA0012 profile (http://airfoiltools.com/airfoil/naca4digit) in 2D then 3D and to compare with the litterature (lot of elements on internet like http://turbmodels.larc.nasa.gov/naca0012_val.html). When you are more comfortable with the software you can use a CAD model (i.e. done on Catia) to generate our aircraft Outer Master Surface and import it. The most interesting is that you can use the power of a parametric CAD model and see "rapidly" influence on the CFD code (when I say rapidly, it depend of course of your CFD model characterisrics and your computer, these calculations need generally a signifiant amount of CPU ressources).