Relation between thrust command and resulting lift force

classic Classic list List threaded Threaded
7 messages Options
Reply | Threaded
Open this post in threaded view
|

Relation between thrust command and resulting lift force

Sven
I am trying to get a relation between the thrust commands (0...4095) and the resulting lift force. Does anyone know of this relation for the pelican or hummingbird?

If not, maybe there is a relation between:
1) the trust command and the resulting input voltage for the motors (depending on the current battery voltage)
2) between motor input voltage and the resulting revolutions per minute?

Thanks,
Sven
Reply | Threaded
Open this post in threaded view
|

Re: Relation between thrust command and resulting lift force

Stefan.Eichhorn
Hi Sven,

the maximum thrust depends on
- type of propeller,
- condition of propeller (new/used) and
- battery level.

The commando equals a certain rpm of the motors. There is a rpm controller at each brushless motor controller!

At the AscTec Hummingbird: 0-100% (0 ... 4095) equals ca. 10grams – 380grams thrust per propeller
At the AscTec Pelican: 0-100% (0 ... 4095) equals ca. 25grams – 800grams thrust per propeller

Please keep in mind that this graph is not linear! However I hope it is a good ball park figure which enables you to control your UAV properly.

If you need more / more precise information please measure the thrust/rpm relation at your own UAV as this heavily depends on your individual set up.


Stefan Eichhorn
Reply | Threaded
Open this post in threaded view
|

Re: Relation between thrust command and resulting lift force

Sven
Hi Stefan,

thanks for the reply. There are some details which are not completely clear to me. You said:

“The commando equals a certain rpm of the motors. There is a rpm controller at each brushless motor controller!“

This means, that the LL Controller is controlling the rpm of each motor? Then why do I need a thrust value for staying in hover depending on the battery level? (lower battery voltage needs a higher thrust value for remaining in hover) In my opinion the thrust force is proportional to rpm^2. So the thrust value should not depend on the battery level if the controller controls the rpm. Did I misunderstood something?

How would you proceed, measuring the thrust / rpm relation? Is there some hidden data structure (or one I accidentally missed) which gives me the current rpm values of the motor controllers?

Thanks,
Sven
Reply | Threaded
Open this post in threaded view
|

Re: Relation between thrust command and resulting lift force

mujtaba.pak


"Sven [via asctec-users]" <[hidden email]> wrote:

>
>
>Hi Stefan,
>
>thanks for the reply. There are some details which are not completely clear
>to me. You said:
>
>“The commando equals a certain rpm of the motors. There is a rpm controller
>at each brushless motor controller!“
>
>This means, that the LL Controller is controlling the rpm of each motor?
>Then why do I need a thrust value for staying in hover depending on the
>battery level? (lower battery voltage needs a higher thrust value for
>remaining in hover) In my opinion the thrust force is proportional to rpm^2.
>So the thrust value should not depend on the battery level if the controller
>controls the rpm. Did I misunderstood something?
>
>How would you proceed, measuring the thrust / rpm relation? Is there some
>hidden data structure (or one I accidentally missed) which gives me the
>current rpm values of the motor controllers?
>
>Thanks,
>Sven
>
>_______________________________________________
>If you reply to this email, your message will be added to the discussion below:
>http://asctec-users.986163.n3.nabble.com/Relation-between-thrust-command-and-resulting-lift-force-tp2898353p2908431.html
>To start a new topic under asctec-users, email [hidden email]
>To unsubscribe from asctec-users, visit
Reply | Threaded
Open this post in threaded view
|

Re: Relation between thrust command and resulting lift force

Steven Bellens
In reply to this post by Sven
2011/5/6 Sven [via asctec-users]
<[hidden email]>:

> Hi Stefan,
>
> thanks for the reply. There are some details which are not completely clear
> to me. You said:
>
> “The commando equals a certain rpm of the motors. There is a rpm controller
> at each brushless motor controller!“
>
> This means, that the LL Controller is controlling the rpm of each motor?
> Then why do I need a thrust value for staying in hover depending on the
> battery level? (lower battery voltage needs a higher thrust value for
> remaining in hover) In my opinion the thrust force is proportional to rpm^2.
> So the thrust value should not depend on the battery level if the controller
> controls the rpm. Did I misunderstood something?

You should probably check with your own uav, but I checked it here and
didn't notice any dependency of the thrust force on the battery level
- as expected.

regards,

Steven

>
> How would you proceed, measuring the thrust / rpm relation? Is there some
> hidden data structure (or one I accidentally missed) which gives me the
> current rpm values of the motor controllers?
>
> Thanks,
> Sven
>
> ________________________________
> If you reply to this email, your message will be added to the discussion
> below:
> http://asctec-users.986163.n3.nabble.com/Relation-between-thrust-command-and-resulting-lift-force-tp2898353p2908431.html
> To start a new topic under asctec-users, email
> [hidden email]
> To unsubscribe from asctec-users, click here.
Reply | Threaded
Open this post in threaded view
|

Re: Relation between thrust command and resulting lift force

Nguyen Phuong
In reply to this post by Stefan.Eichhorn
Do you know those relation in Firefly? Could you please provide me that information?

Thanks
Reply | Threaded
Open this post in threaded view
|

Re: Relation between thrust command and resulting lift force

userhummingbird
In reply to this post by Sven
I found for the Hummingbird this thesis. There is an experiment trying to get this relation.  "Real-time Control Architecture for a Multi UAV Test Bed", by Patricio Cruz (2012). Page 37-40. Easy to find in google.
Regards