paparazzi-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Paparazzi-devel] AoA sensor


From: Hector Garcia de Marina
Subject: Re: [Paparazzi-devel] AoA sensor
Date: Thu, 9 Jun 2011 07:25:59 +0200

Hi Bruzzle,

I had the same issues about pressure sensors. I solved it applying an IIR filter (Butterworth 3 order) always to the raw values from ADC, never to the post-processed data.

My problem with sensors started in Mentor because the motor vibrations (around 6000rpm ~ 133Hz), so 
I have to sample at 266Hz minimum to avoid aliasing. With this, my signals from pressure sensors are really cleaned and the delay is about 0.01 seconds.

Thanks about your bachelor thesis, I will send you a link this afternoon (now I am at work) where download my MSc. Thesis (it is heavy due to the images, about 70MB). If somebody more is interested, I can post the link here in the mail list.

I will give a try to the AoA sensor based on pressure sensors (I think MPX7002 can do the work). Now I am learning about the STM32 micro, yesterday I had my first evaluation board from Olimex!, I built a gcc 4.6.0 compiler and flashed the board with a blinking led example with OpenOCD. So, it will take me time to get in used with the micro, rewriting firmware, assemble Lisa with Overo, assemble the new IMU... I hope in 3 months to be flying, at least with only telemetry.

Cheers
Héctor


On Thu, Jun 9, 2011 at 2:04 AM, Leandro Chelini <address@hidden> wrote:
@ Felix
The AoA Module needs changes in the estimator and there is a pitch switch in the pitch loop of stabilization.
Maybe it needs a short description for the usage in the airframe.

If you create a branch only for this, witch I have write access to, I can upload the code and modifications.
I think this is a part for the dev branch.

There are other useful modules that should be published. Like a Flight Benchmark (error square sum) to optimizing the parameters.
 But it needs time. In a few weeks I will have more time to publish and describe the publishable code.

@ Hector
This sensor was the last thing we does to optimize the autonom landing and the bungee start. So it isn't aerodynamic optimized.
With this AoA Thing on, the Mentor flies really crappy. But it does it's work.
The "Flag" can also be built smaller.
I advise to take a sensor with bearing balls! (I took the M6-type because I thought it has a metric thread)
I have bad experiences with pressure sensors. We have AMSYS pressure sensors to measure the airspeed and we had to filter it hard to make the data usable. In the case of the airspeed it isn't really bad if the data comes 0.25 seconds delayed, but for a AoA sensor....
Maybe we took the wrong filter (PT1)
I can send you my Bachelor thesis, but it's in German. ?!?
The theses includes generally documentations about our autonomous start and  land algorithm. (sonar etc.)


Bruzzlee

Am 08.06.11 17:22, schrieb Hector Garcia de Marina:
Thank you very much Leandro.

Actually I am employing a Mentor Multiplex, and I found the same hall effect sensor, but I am worried about
the size of your sensor and how it affects to the airfoil.

I have though in 2 dynamic pressure sensors attached plus/minus 15º, with 0º at the mean airfoil reference. Hoping that the pressure difference is proportional to AoA (small angles approximation, minor than plus/minus20º AoA actually).

What do you think, have you tested this kind of idea before? It seems mechanically simpler, but I do not know about what performance I will obtain.

By the way, have you any documentation about your experiences with Mentor? I can upload my master thesis applied to it as well. Right now, I am sectioning the airfoil, and horizontal and vertical tails, for applying them a CFD. Do you have experience with this in Mentor?

Thanks in advance.

pd: you can check out this video with my navigation algorithm running in a Mentor, it only shows attitude estimation http://www.youtube.com/watch?v=TRR4Jzz3ZjE&feature=related). My HW is pretty similar to paparazzi classic, but employing atmel at91sam7s256 instead LPC (DMA is a must for me), and I added a SD card as well. Now I have changed to Lisa/L to start with navigation algorithms based on camera vision, but it needs some modifications for fitting my requirements.

Cheers.


On Wed, Jun 8, 2011 at 4:16 PM, Leandro Chelini <address@hidden> wrote:
We've built a AoA Sensor and attached it to a Mentor.
Sensor: US DIGITAL MA3-A10-236-N
It seems like it works. We've only tested it with airy conditions.
The AOA_adc Module you can find at
https://github.com/Bruzzlee/paparazzi/tree/master/sw/airborne/modules/sensors

We've written a documentation, witch includes this theme. But it's in German.
The documentation will being published in the next two weeks.

In your case we use the AoA-Data to control the Pitch-Loop of the Inner-Loop

All modifications and more you can find in:
address@hidden:Bruzzlee/paparazzi.git

Bruzzlee

Am 07.06.11 15:22, schrieb Hector Garcia de Marina:
Hello guys,

I was looking to upgrade my UAV instrumentation and I was thinking to add an Angle Of Attack sensor.

I've found this schematic http://www.charlesriverrc.org/articles/asfwpp/lelke_launch.htm , and it looks interesting but really
I don't know its performance, calibration, etc

Anyone of you are using a "home-made" AoA sensor? , on the other hand, are there cheap ones and light enough for an UAV such as TwinStarII or Mentor?

Thanks in advance,
Cheers

--
Héctor


_______________________________________________ Paparazzi-devel mailing list address@hidden https://lists.nongnu.org/mailman/listinfo/paparazzi-devel

_______________________________________________
Paparazzi-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/paparazzi-devel




--
Héctor


_______________________________________________ Paparazzi-devel mailing list address@hidden https://lists.nongnu.org/mailman/listinfo/paparazzi-devel

_______________________________________________
Paparazzi-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/paparazzi-devel




--
Héctor



reply via email to

[Prev in Thread] Current Thread [Next in Thread]