Hi Jorge,
airspeed is useful for stability (if you work respecting to the stability axes with AoA and AoS angles instead of body frame/navigation frame). If you have characterized your plane in a wind tunnel, and you know
the optimum AoA and Airspeed for ration Lift/Drag (you know CL, CD and so on), or for preventing stall, etc, then is useful the airspeed (remember that you flying respecting the air axes, and not the ground axes).
As far as I know, paparazzi (so far), does not cover this kind of stuff (yet!). The main issue is to obtain a reliable, cheap and small sensors for AoA, AoS angles.
Héctor
On Thu, Jul 12, 2012 at 9:30 AM, Reto Büttner
<address@hidden> wrote:
Hi Jorge
I do not recommend an airspeed sensor. To my experience it is not worth the effort, cost and complexity.
I experienced problems integrating the eagletree airspeed sensor on my eHawk. Connecting it to paparazzi via i2c and integrating it in the software worked fine as described on the wiki. But the sensor measurement was to inaccurate. I didn't find out why (pitot tube or pressure sensor). I didn't get better flight results than using standard paparazzi GPS control. Therefore I am not using the airspeed sensor anymore. I get perfect flight results in precision and reliabiliy without an airspeed sensor.
The chance of saving an UAV thanks to an airspeed sensor when GPS fails is minimal. Your IMU will start to drift whithout GPS calibration and attitude control will fail. You could use IR sensors instead of an IMU as they work perfectly without GPS. Or you could use a sophisticated IMU that doesn't require GPS calibration. Still the airspeed sensor is no real added value. First you can control speed fine using throttle and pitch angle without having an airspeed sensor. Second even if you can control attitude and speed, you are likely to lose your UAV without GPS as you will not find home.
For reliability you better consider FPV as fall back. That works no matter which part of the autopilot fails.
Even better go for simplicity. To my experience simplicity is the most effective way to reliabilty. Adding more systems and redundancy you introduce more failure modes and interactions. It requires great effort to really enhance reliabilty by adding more systems. It is more effective to invest that effort in robust design (e.g. preventing interference), testing, maintenance, operation procedures and training.
Happy landings,
Reto2012/7/12 Jorge Pantoja
<address@hidden>
Hi Christophe,
Thank you for your answer. So, should I connect the pitot to have it in case of GPS failure? Is there an additional programing that needs to be done?
Regards,
Jorge
On Wed, Jul 11, 2012 at 1:43 PM, Christophe De Wagter
<address@hidden> wrote:
Paparazzi CHIMU code uses GPS to get the speed. This is in theory more accurate than airspeed. You would only want to feedback airspeed when the GPS is failing
-Christophe
On Wed, Jul 11, 2012 at 6:35 PM, Jorge Pantoja
<address@hidden> wrote:
Hi everyone,
I am using a Yapa2 + CHIMU + Ublox GPS LEA 5H + 900 MHz Xbees. All the hardware is integrated properly, but I have a question: Would you recommend integrating the Eagle Tree Airspeed sensor as well?
According to the CHIMU manual we need an extra airspeed sensor to correct the measurements given to the autopilot.
Best Regards,
--
Jorge Pantoja
Program Manager/Liaison
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
--
Jorge Pantoja
Program Manager/Liaison
_______________________________________________
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
--
_______________________________________________
Paparazzi-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/paparazzi-devel