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Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation



 
 
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  #1  
Old October 2nd 19, 07:16 PM posted to rec.aviation.soaring
G Moore
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Posts: 9
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

Wanted: Experienced Flight Dynamicist to Facilitate Development of Winching Pitch Axis-Only Glider Model

I am a pilot, instructor, and retired Electrical Engineer building a next generation active tension-controlled winch for improved safety, height attained, and pilot experience (among other innovations). All the development work is being done open source by myself and a few collaborators and all related technical documents are publicly available. I have no plans to make a business out of this work, i.e. building and selling winches or plans (but an enterprising entrepreneur would be welcome to do so). The investigation outlined below would be an opportunity for someone with the appropriate skills to make a significant contribution to the understanding of winch launch dynamics to our sport’s benefit.

A key aspect in closing a tension servo loop is the behavior of a coupled mass-spring-mass system formed by the winch equivalent mass (mostly due to the drum’s angular inertia), the cable’s elasticity, and the glider mass. This system’s dynamics are well understood during the ground roll and early rotation launch phases but how the glider aerodynamics affects this system following the rotation and into the climb phase is not. Some conceptual theories have been formulated but without a relevant pitch axis model they cannot be evaluated. To that effect, I am looking for help in developing a simple pitch axis-only glider model valid during winching. Conceptually, the thrust force in an airplane’s pitch model would be replaced by the cable tension force acting on a hook displaced from the CG whose pull angle varies throughout the launch. I am an experienced control systems engineer but I and my current collaborators’ limited aerodynamics knowledge is restricting our ability to develop a simple but representative model that encapsulates the fundamental behaviors exhibited by a glider during a winch launch. For full launch simulations, A simple non-linear (lift/drag proportional to airspeed squared but AoA solidly in the linear regime) model where the cable pull angle varies as the launch proceeds is desired. For the tension control systems analysis, linearized models for different launch portions (primarily cable pull angles) are needed. This model would encompass both the phugoid and short period modes. We have studied and basically understand Etkins on these subjects but struggle to decide what is important to include in such a model and what can be ignored while still capturing the essential behaviors. We simply lack the knowledge and experience a skilled aerodynamicist could bring to the investigation.

We would appreciate any assistance a member of this forum might provide. A contributor would likely find this a very fun and intellectually challenging project. Development of an appropriate model requires a strong familiarity with Laplace domain modeling of aerodynamic systems using pole-zero transfer functions. Experience in simulating such systems would be a plus but I have implemented full launch simulations using simpler models using Matlab and Simulink and incorporating a more sophisticated model in these simulations should be straightforward. Several options have been identified for how AoA/airspeed would be controlled, i.e., the pilot stick inputs, but further details are beyond this short introduction’s scope. If you should know of such a person who does not commonly participate in this forum that might be appropriate for this project, I would greatly appreciate your forwarding this solicitation to them.

If you think you might be interested, I would be happy to share the prior work and speculations on this subject (and in general on tension-controlled winching). If after reviewing this material, you decide this is not something you would like to become involved with there would be no obligation; we would be happy you took a look. But maybe you could point us at someone else that might be interested. The level of involvement is totally open. At a minimum, direction as to what to include/not include in an already outlined preliminary model and help in determining some representative values for some of the key parameters, e.g. glider rotational inertias about the pitch axis, would be extremely useful. But what would be ideal would be someone to discuss the problem and issues with and then they take the lead on determining what an appropriate model should be, how it should be parameterized, and evaluating is it providing the essential behaviors important to the larger winch mass/cable spring/glider system dynamics.

Should you be interested and a university educator, this could be a good project a Masters level Aeronautical Engineering student. The results would be publishable—again this is an open source project with everything in the public domain. This could be expanded to a prospective thesis topic.. How such an undertaking would be structured is open to discussion.

If you’d like to learn more, send me a note and we can figure out how to go from there. We would probably start with my sharing of some earlier reports, simulations, and logged data from actual launches for your review.

Thank you,

George Moore, CFIG, Ph.D.
gsmoore501 AT gmail DOT com
  #2  
Old October 5th 19, 02:19 AM posted to rec.aviation.soaring
G Moore
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Posts: 9
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

On Wednesday, October 2, 2019 at 11:16:16 AM UTC-7, G Moore wrote:
Wanted: Experienced Flight Dynamicist to Facilitate Development of Winching Pitch Axis-Only Glider Model

I am a pilot, instructor, and retired Electrical Engineer building a next generation active tension-controlled winch for improved safety, height attained, and pilot experience (among other innovations). All the development work is being done open source by myself and a few collaborators and all related technical documents are publicly available. I have no plans to make a business out of this work, i.e. building and selling winches or plans (but an enterprising entrepreneur would be welcome to do so). The investigation outlined below would be an opportunity for someone with the appropriate skills to make a significant contribution to the understanding of winch launch dynamics to our sport’s benefit.

A key aspect in closing a tension servo loop is the behavior of a coupled mass-spring-mass system formed by the winch equivalent mass (mostly due to the drum’s angular inertia), the cable’s elasticity, and the glider mass. This system’s dynamics are well understood during the ground roll and early rotation launch phases but how the glider aerodynamics affects this system following the rotation and into the climb phase is not. Some conceptual theories have been formulated but without a relevant pitch axis model they cannot be evaluated. To that effect, I am looking for help in developing a simple pitch axis-only glider model valid during winching. Conceptually, the thrust force in an airplane’s pitch model would be replaced by the cable tension force acting on a hook displaced from the CG whose pull angle varies throughout the launch. I am an experienced control systems engineer but I and my current collaborators’ limited aerodynamics knowledge is restricting our ability to develop a simple but representative model that encapsulates the fundamental behaviors exhibited by a glider during a winch launch. For full launch simulations, A simple non-linear (lift/drag proportional to airspeed squared but AoA solidly in the linear regime) model where the cable pull angle varies as the launch proceeds is desired. For the tension control systems analysis, linearized models for different launch portions (primarily cable pull angles) are needed. This model would encompass both the phugoid and short period modes. We have studied and basically understand Etkins on these subjects but struggle to decide what is important to include in such a model and what can be ignored while still capturing the essential behaviors. We simply lack the knowledge and experience a skilled aerodynamicist could bring to the investigation.

We would appreciate any assistance a member of this forum might provide. A contributor would likely find this a very fun and intellectually challenging project. Development of an appropriate model requires a strong familiarity with Laplace domain modeling of aerodynamic systems using pole-zero transfer functions. Experience in simulating such systems would be a plus but I have implemented full launch simulations using simpler models using Matlab and Simulink and incorporating a more sophisticated model in these simulations should be straightforward. Several options have been identified for how AoA/airspeed would be controlled, i.e., the pilot stick inputs, but further details are beyond this short introduction’s scope. If you should know of such a person who does not commonly participate in this forum that might be appropriate for this project, I would greatly appreciate your forwarding this solicitation to them.

If you think you might be interested, I would be happy to share the prior work and speculations on this subject (and in general on tension-controlled winching). If after reviewing this material, you decide this is not something you would like to become involved with there would be no obligation; we would be happy you took a look. But maybe you could point us at someone else that might be interested. The level of involvement is totally open. At a minimum, direction as to what to include/not include in an already outlined preliminary model and help in determining some representative values for some of the key parameters, e.g. glider rotational inertias about the pitch axis, would be extremely useful. But what would be ideal would be someone to discuss the problem and issues with and then they take the lead on determining what an appropriate model should be, how it should be parameterized, and evaluating is it providing the essential behaviors important to the larger winch mass/cable spring/glider system dynamics.

Should you be interested and a university educator, this could be a good project a Masters level Aeronautical Engineering student. The results would be publishable—again this is an open source project with everything in the public domain. This could be expanded to a prospective thesis topic. How such an undertaking would be structured is open to discussion.

If you’d like to learn more, send me a note and we can figure out how to go from there. We would probably start with my sharing of some earlier reports, simulations, and logged data from actual launches for your review.

Thank you,

George Moore, CFIG, Ph.D.
gsmoore501 AT gmail DOT com


Still looking. I would ask members of the forum to review the project and think about other club members or acquaintances that might have the necessary skills and might be interested in helping with this problem.

-George
  #3  
Old October 5th 19, 02:19 PM posted to rec.aviation.soaring
SF
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Posts: 214
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

You might have better luck searching fo someone that is looking for a doctoral thesis subject at one of the aeronautical schools.
  #4  
Old October 5th 19, 03:53 PM posted to rec.aviation.soaring
[email protected]
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Posts: 317
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

George, I will show/send your posting to some of the Embry Riddle kids we have flying at our winch only club here in Prescott AZ. Not sure if any, about 5 currently, are Aerodynamicists, but they may be interested.

Cliff Hilty CFIG Prescott Area Soaring

CH ASW27
  #5  
Old October 5th 19, 04:23 PM posted to rec.aviation.soaring
G Moore
external usenet poster
 
Posts: 9
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

On Saturday, October 5, 2019 at 7:53:50 AM UTC-7, wrote:
George, I will show/send your posting to some of the Embry Riddle kids we have flying at our winch only club here in Prescott AZ. Not sure if any, about 5 currently, are Aerodynamicists, but they may be interested.

Cliff Hilty CFIG Prescott Area Soaring

CH ASW27


Cliff,

Thank you very much. Even if they don't have the needed skills or interest, they may know other students that do/are or may run it by a facility member.
  #6  
Old October 5th 19, 04:24 PM posted to rec.aviation.soaring
G Moore
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Posts: 9
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

On Saturday, October 5, 2019 at 6:19:32 AM UTC-7, SF wrote:
You might have better luck searching fo someone that is looking for a doctoral thesis subject at one of the aeronautical schools.


SF,

Yes, I am hoping some forum members may know professors in some of the aeronautical schools with an interest in soaring that they might forward this solicitation on to. As noted in the original posting, this could be expanded to a Master level thesis topic. Not sure if it rises to the level of a PhD thesis.
  #7  
Old October 5th 19, 06:09 PM posted to rec.aviation.soaring
[email protected]
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Posts: 2
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

Wanted: Expereienced speel chekr. Univercity levl cumunikashuns skils is sho'nuff perfured. If'n intristid, call BR-549...
  #8  
Old October 5th 19, 09:23 PM posted to rec.aviation.soaring
Patrick Grady
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Posts: 5
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

I know how to measure a glider's pitch moment of inertia. In our hangar, we use a hanging cradle to lift a glider for more floor space. This means that we essentially have a pendulum with a glider at the bottom.

You could measure the period of oscillation with a glider and without. The extra mass of the glider wouldn't change the period of oscillation, but the moment of inertia would. I've used this technique to measure rotational inertia of bicycle wheels, and I think it's possible to get within about 5% accuracy.

https://en.wikipedia.org/wiki/Moment...pound_pendulum
  #9  
Old October 6th 19, 01:43 AM posted to rec.aviation.soaring
G Moore
external usenet poster
 
Posts: 9
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

On Saturday, October 5, 2019 at 1:23:56 PM UTC-7, Patrick Grady wrote:
I know how to measure a glider's pitch moment of inertia. In our hangar, we use a hanging cradle to lift a glider for more floor space. This means that we essentially have a pendulum with a glider at the bottom.

You could measure the period of oscillation with a glider and without. The extra mass of the glider wouldn't change the period of oscillation, but the moment of inertia would. I've used this technique to measure rotational inertia of bicycle wheels, and I think it's possible to get within about 5% accuracy.

https://en.wikipedia.org/wiki/Moment...pound_pendulum


Patrick,

Interesting. I had not thought about a pendulum's bob's moment of angular inertia affecting itsperiod. I would assume the glider would have to be rigidly mounted to the pendulum arm for this effect to be exhibited and that might be problematic with your sling.

The key thing I am looking for is the pitch-axis model. Most importantly, as simple a model as possible. I want to understand the fundamentals of what the aerodynamics do the the larger mass-spring-mass model. I often paraphrase a quote that was attributed to Einstein, "Every model should be as simple as possible, but no simpler." Only after that model has been established do I need to parameterize it. I suspect X-Plane, which I have never worked with, would have the parameters for some gliders but I believe the models it uses are more sophisticated than what I am looking for. That is where I would hope an experienced aerodynamicist would be able to determine a proper model for the investigation and then help parameterize it; possibly extracting the needed parameters from simulators like X-Plane.

George
  #10  
Old October 6th 19, 02:05 PM posted to rec.aviation.soaring
[email protected]
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Posts: 281
Default Wanted: Expereienced Flight Aerodynamicists for Winch Launch Investigation

It might be worth reading a bit on X-plane. It works starting with a model of the plane's shape and calculates the aerodynamic forces on the fly. There are tools for making models of new planes and a fair library of existing ones.

It is made to talk to other programs in a motion simulator environment. It has an external interface to get out the state vectors and probably put in the controls.

Does anybody know if it has a way to put in the tow rope forces?
 




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