GPS Problems

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GPS Problems

meghanreim
Hey all,

We flew today in Auto2 and the ground control station showed the airplane flying in a loop 60m ahead of us, while the airplane was going straight over our heads, not attempting to continue the loop. The plane first started to go into the loop, and at about 3/4 of the way around, it experienced the problem. It showed the same problem 3 different times. There was a bit of a crosswind, but the GCS should show the GPS reading from the airplane. We are using the NEO M8 GPS module, so we are not sure why this was happening with such an accurate GPS module. I assume that the position accuracy spiked up for some reason, but during the flight, all I saw was around a 6m position accuracy.

The GPS module is mounted on the top of the airplane, facing up, and at least 6" away from any source of potential interference (motor, ECS, servos, radio). Any ideas why this might have happened?

Thanks,
Meghan


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Re: GPS Problems

Simon Liebold
Hi Megan,

I have a M8N and experience the same issue with my multicopter. Any autonomous flight is essentially impossible.

During CCCamp Felix helped my to understand the issue: Somehow (still not fully understood) the ucenter module fails to apply the Paparazzi U-Blox standard configuration and the module will continue to operate with its default configuration. That is a update rate of just 1/s and a dynamic model (CFG-NAV5-dynModel) of "0 - portable". Especially the latter causes sudden position changes to get filtered out and only slowly to move to a new position. This would work great for a pedestrian, but causes the mentioned problems in our application.

To verify you can activate a debug flag in the XML configuration of the ucenter module. This will cause a debug message to be sent during startup. The message is sent just once, be sure to have the telemetry messages displayed before powering up. There may be more than one debug message. Look for the one with 16 (or so, cannot look it up right now) digits. If it returns a bunch of non-zero digits then it managed to apply the configuration. If it is all zero you have the same issue I see with my module.

I now created the configuration manually using the U-Center application from U-Blox and will try to make it work with the ucenter module in Paparazzi deactivated. My module seems to have problems with its flash memory because it keeps forgetting its configuration when left without power for an extended amount of time further complicating my debugging efforts.

Preferably, the M8* will work with the ucenter module. But so far I wasn't able to find anything obviously wrong in the module code.

If there is anyone with an M8 module that just works nicely with the ucenter module, please let us know.

Simon

Am 14. September 2015 01:28:52 MESZ, schrieb Meghan <[hidden email]>:
Hey all,

We flew today in Auto2 and the ground control station showed the airplane flying in a loop 60m ahead of us, while the airplane was going straight over our heads, not attempting to continue the loop. The plane first started to go into the loop, and at about 3/4 of the way around, it experienced the problem. It showed the same problem 3 different times. There was a bit of a crosswind, but the GCS should show the GPS reading from the airplane. We are using the NEO M8 GPS module, so we are not sure why this was happening with such an accurate GPS module. I assume that the position accuracy spiked up for some reason, but during the flight, all I saw was around a 6m position accuracy.

The GPS module is mounted on the top of the airplane, facing up, and at least 6" away from any source of potential interference (motor, ECS, servos, radio). Any ideas why this might have happened?

Thanks,
Meghan




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Re: GPS Problems

onefastdaddy
Hello,
Maybe I can help here.
The GPS comes from the factory with very generic common settings that are pretty good for an automotive or pedestrian application not autonomous flying robot.
To change these settings usually requires using the u-center utility. The settings required for Paparazzi are found on the Wiki under GPS. Go to the main Wiki (wiki.paparazziuav.org) then there is a search window at the top right. Enter "GPS" there and search. It will take you here: https://wiki.paparazziuav.org/wiki/GPS
Are there any specific questions about this page? The help on it? A setting?
It is safe to use the module: gps_ubx_ucenter in your airframe file even if you do not have issues. You add this to your airframe file: <load name="gps_ubx_ucenter.xml" />. Better if unsure search the existing airframe files for: "gps_ubx_ucenter". You will find at least one. Use that same code in yours.
I do not know how much detail you need but the two posts here imply there is some expectation that from the factory the UBlox GPS module should just work which is unfortunately not the case. When you buy from a vendor however they should pre-configure it for you.
The module mentioned above is thanks to the smart people who develop Paparazzi. It means you do not need to use u-center app and can do it instead inside the GCS.
I just reviewed the GPS page and it appears more than enough detail exists. I can help more once you review it and have more specific questions.
No worries, we can sort this out and you will have new experience to add to your Paparazzi resume.
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Re: GPS Problems

meghanreim
We were using the ucenter module in the code when we experienced the problem. The next time we flew, we specified the dynamics model, and the UAV followed the path specified on the GCS, but the GPS debug messages still showed there was no response for the NAV5 configuration.

We will try loading the configuration onto the GPS using the ucenter program instead to see we can get a successful NAV5 configuration response.

Thanks for the suggestions,
Meghan

On Sep 15, 2015, at 8:56 AM, onefastdaddy <[hidden email]> wrote:

> Hello,
> Maybe I can help here.
> The GPS comes from the factory with very generic common settings that are
> pretty good for an automotive or pedestrian application not autonomous
> flying robot.
> To change these settings usually requires using the u-center utility. The
> settings required for Paparazzi are found on the Wiki under GPS. Go to the
> main Wiki (wiki.paparazziuav.org) then there is a search window at the top
> right. Enter "GPS" there and search. It will take you here:
> https://wiki.paparazziuav.org/wiki/GPS
> Are there any specific questions about this page? The help on it? A setting?
> It is safe to use the module: gps_ubx_ucenter in your airframe file even if
> you do not have issues. You add this to your airframe file: <load
> name="gps_ubx_ucenter.xml" />. Better if unsure search the existing airframe
> files for: "gps_ubx_ucenter". You will find at least one. Use that same code
> in yours.
> I do not know how much detail you need but the two posts here imply there is
> some expectation that from the factory the UBlox GPS module should just work
> which is unfortunately not the case. When you buy from a vendor however they
> should pre-configure it for you.
> The module mentioned above is thanks to the smart people who develop
> Paparazzi. It means you do not need to use u-center app and can do it
> instead inside the GCS.
> I just reviewed the GPS page and it appears more than enough detail exists.
> I can help more once you review it and have more specific questions.
> No worries, we can sort this out and you will have new experience to add to
> your Paparazzi resume.
>
>
>
> --
> View this message in context: http://lists.paparazziuav.org/GPS-Problems-tp17353p17357.html
> Sent from the paparazzi-devel mailing list archive at Nabble.com.
>
> _______________________________________________
> Paparazzi-devel mailing list
> [hidden email]
> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel


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Re: GPS Problems

Simon Liebold
Meghan,

I ended up buying a new GPS module. The other M8N module that I had ordered from eBay was either dead on arrival or I damaged it by powering it with 5V for a while before I realized that it preferred 3.3V.

Also with the new module I was able to upload the AssistNow offline data via the u-center software. Trying to do this with the other module gave me lots of errors before. Maybe it had an issue with its flash memory.

I can highly recommend this new Drotek module. The copter seems like "nailed to the sky".

Simon

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Re: GPS Problems

Simon Liebold
In reply to this post by meghanreim
Resending. The earlier post didn't reach the mailing list. Omitting the
link this time.

Meghan,

I ended up buying a new GPS module (the XL from Drotek). The other M8N
module that I had ordered from eBay was either half-dead on arrival or I
damaged it by powering it with 5V for a while before I realized that it
preferred 3.3V.

Also with the new module I was able to upload the AssistNow offline data
via the u-center software. Trying to do this with the other module gave
me lots of errors before. Maybe it had an issue with its flash memory.

I can highly recommend this new Drotek module. The copter seems like
"pinned to the sky".

Simon



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