Pixhawk - Marvelmind

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Re: Pixhawk - Marvelmind

Postby admin » Sat Jan 07, 2017 5:44 pm

Hendrik wrote:Hi cagiva851,

With Marvelmind dashboard I mapped NESW directions correctly to my testenvironment.
1 beacon, left down, = 0,0 (ID 56)
1 beacon, right down, E (ID 81)
1 beacon, left top N (ID 27)
1 beacon Right top (ID 51)

Starting set of beacons: 81; 56,51,27
So:

ID27----------------ID51
|
| N
| |
| S
|
ID56----------------ID81

Georeferencing in modem Lat. N0.00000, Lon E0.00000
(So on the map of Mission planner and APM planner the copter is somewhere on the ocean near Africa)

So when the hedgehog is going from ID56 to ID27 it is going 0 degrees North
I returned to original Ardupilot, so lost the BCN_ parameters (which I thought were only usefull with Pozyx. I have Pozyx, I like the UWB approach, but accuracy and missing the NMEA protocol stopped that path)
I have COMPASS_AUTODEC set to 0 and COMPASS_DEC set to a value where the direction to North is conform my testenvironment.
My testenvironment at this moment is a room at home. I have a hexacopter of 1 meter and a octocopter of 1.40 meter, so testing autonomous flight indoor is very tricky.
I ordered an extra set from Marvelmind, hoping that extra beacons will increase accuracy and preventing loss off beacons by having more line-off-sights.

My test involves picking a carton with the copter, so placing the mobile beacon underneath is not possible.

Monday I will start testing.



You have a very heavy stuff for indoor! :-)
Check the advises above. Check through them again. For you, Hendrik, the most important, indeed, would be to set the gain properly. Like you described already, I would do the following:
- Put the copter in the starting position of on the table or somewhere and make the motors working on nearly flying power
- Run the oscilloscope and see the noise versus signal. With very high probability, you would have to reduce the gain manually, if you have manual gain set. If you have automatic gain control (AGC), then you are, probably, at the optimal gain already. However, check it still. AGC is tricky. You shall have the threshold clearly above the noise from motors, but below peaks of your signal
- Play with threshold, gain (manual vs. AGC)
- Check signal/noise to all your stationary beacons
- If you fly too close to stationary beacon, that beacon's measurement may be disturbed. Or not - depends on the settings and the level of disturbance

When you set optimal settings, you shall be just fine.

With more beacons you can create more dense maps. This helps a lot:
- Signal to noise ratio increases
- Update rate increases
Use feature submap to build submaps: viewtopic.php?f=2&t=544&p=783&hilit=submap#p783

Keep us posting. We will be happy to assist and help :-)

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Re: Pixhawk - Marvelmind

Postby cagiva851 » Sat Jan 07, 2017 9:21 pm

Thanks @admin for all that information. I'll play with settings as you suggested.

@Hendrik, we cannot use the belly of the copter either (see video below) so let me know if you experience problems during the landing (RTL) with the mobile beacon installed on the top.

https://youtu.be/t7RmGYau9cM

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Re: Pixhawk - Marvelmind

Postby admin » Sun Jan 08, 2017 6:34 am

cagiva851 wrote:Thanks @admin for all that information. I'll play with settings as you suggested.

@Hendrik, we cannot use the belly of the copter either (see video below) so let me know if you experience problems during the landing (RTL) with the mobile beacon installed on the top.

https://youtu.be/t7RmGYau9cM


Very impressive stuff flying! ;-))

The recommendation to install on the belly came with the assumption, that stationary beacons are installed below the copter. Since you are flying indoor and there is ceiling (not unlimited height of flight), it is still much better to install the mobile beacon on the top of the copter and stationary beacons - high on the walls or on the ceiling. Install the mobile beacon pretty much similar to how regular GPS antenna is usually installed: http://www.winddeal.net/image/072/D12630/D12630-5.jpg

In your lab environment, I recommend to install stationary beacons on the columns or on the walls - a few meters from the copter.

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Re: Pixhawk - Marvelmind

Postby cagiva851 » Sun Jan 08, 2017 8:15 am

@admin, do you know any SMA antenna the same size as the antenna that comes with the beacons, but it bends like these below?

http://store.roboticsbd.com/801-thickbo ... ladesh.jpg

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Re: Pixhawk - Marvelmind

Postby admin » Thu Jan 12, 2017 5:37 am

cagiva851 wrote:@admin, do you know any SMA antenna the same size as the antenna that comes with the beacons, but it bends like these below?

http://store.roboticsbd.com/801-thickbo ... ladesh.jpg



Yes, we have that option. It is not published on the web site, but we have them.
What sizes would you need? They are around 10-11 cm and another one - 16 cm, when bent 90 degrees. When not bent - a couple of cm longer.

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Re: Pixhawk - Marvelmind

Postby cagiva851 » Thu Jan 12, 2017 5:54 am

I just ordered this one today, but I let you know if I need more or a longer one.

https://www.sparkfun.com/products/675ht ... oducts/675

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Re: Pixhawk - Marvelmind

Postby admin » Thu Jan 12, 2017 6:35 am

cagiva851 wrote:I just ordered this one today, but I let you know if I need more or a longer one.

https://www.sparkfun.com/products/675ht ... oducts/675


You may expect that this will work purely ... It doesn't have the 433MHz band:


GSM/850E : 824 to 894MHz
GSM : 880 to 960MHz
DCS : 1710 to 1880MHz
PCS : 1850 to 1990MHz

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Re: Pixhawk - Marvelmind

Postby cagiva851 » Thu Jan 12, 2017 7:34 am


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Re: Pixhawk - Marvelmind

Postby admin » Thu Jan 12, 2017 7:47 am

cagiva851 wrote:Ok, I got the right ones now.

https://www.amazon.com/gp/product/B00KA ... HOEADOGAP0


Yes, these are the right ones :-))
They are short and compact. So, the distance in radio won't be the highest possible.

If you want the maximum distance, the full-size 165mm antennas are significantly better. With shortened ones (50mm) we have tested up to 100m in ideal conditions indoor. With full-size 165mm we have tested up to 400m outdoor in the ideal conditions (line of sight).

The full-size looks like this: https://www.amazon.com/TP-Link-Omni-dir ... 82HA7XSW2A - but for the 433MHz band. This one wouldn't suit

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Re: Pixhawk - Marvelmind

Postby amolad » Wed Jan 18, 2017 1:27 pm

@admin
Would you mind posting the little tweaks we could play around with in the manual? Cause they are all over the forum :D

I too have the pixhawk on a rover and I have the 4 stationary beacon and one hedge system. I am getting a good lock when the system is stationary but once the whole system is switched on, the position starts to flicker around (10-15 cms on the map). And when I upload an auto mission, the rover goes to the target in zig zag way and does not follow a straight path. (But when i take over through remote control, the rover goes straight and i do observe an accuracy of 5-6 cms on the map and face no issues.)

I am not sure if this is an issue with the rover autopilot or the marvelmind system. Is anyone else facing the issue?

BTW the ardurover firmware i'm using is the latest stable build.

EDIT: Wanted to add regarding setting of the compass orientation. Any guide on this? is it better to adapt marvelmind setup to the geodetic system or better for the ardupilot to adapt to the local marvelmind system?


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