Advice for integrating an offboard INS?
« on: May 18, 2016, 08:10:14 pm »
Hi,

I am new to this project and wanted to ask if anyone might have some advice or thoughts on an effort I am exploring.  I am looking into integrating an Inertial Sense uINS-2, https://inertialsense.com/products/, with the CC3D by streaming the INS state estimate data from the uINS to the CC3D via UART.  (Basically this will allow the use of temperature calibrated sensors and their state estimator with the existing  flight controller.)

I wondered if anyone might have advice on specific files in the repo I should be focused on for insertion points and where to start parsing the incoming data stream and then distributing the INS data.

Thanks to anyone who can point me in a useful direction!

-Mark

f5soh

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Re: Advice for integrating an offboard INS?
« Reply #1 on: May 18, 2016, 08:16:30 pm »
Hi,

Why add a a 260$ board to a 20$ CC3D board where a Revo already support all sensors you have with this INS module ?

https://librepilot.atlassian.net/wiki/display/LPDOC/INS13+-+GPS+Navigation

Brian

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Re: Advice for integrating an offboard INS?
« Reply #2 on: May 18, 2016, 08:27:26 pm »
Actually, it's just under $1000 for the uINS-2!  It does look like a very interesting piece of hardware, but the price seems outrageous.  I can't imagine why you would need it unless it has some sort certification that's required for a specific application, in which case I wouldn't pair it with a CC3D.  For anything "hobby-grade", stick with the Revo or something similar.

hwh

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Re: Advice for integrating an offboard INS?
« Reply #3 on: May 18, 2016, 08:29:59 pm »
In addition to what f5soh and Brian said above, what features in the cc3d firmware are you going to take out to make room for your new code?  The cc3d has no room for added features, that's why it doesn't support gps navigation using standard gps units.

Re: Advice for integrating an offboard INS?
« Reply #4 on: May 18, 2016, 11:21:10 pm »
Thanks Everyone for responding so quickly!

Like I mentioned, I'm new to this project as well as the project that is working to integrate the uINS, so please forgive the mistake I made in stating that we are using a CC3D when we are actually using the Revolution. (That was my mistake, and I certainly understand the important differentiation given hwh's reply!).

We have another offboard computer with a uINS2, and the offboard computer is communicating with the Revolution, so because the uINS is already in place, and because it has two serial ports, we would like to be able to utilize the (offboard) uINS-2 data via the STM32F's UART port.  This could give the ability to use the uINS data/state estimate in addition to or in lieu of the existing Revolution sensor data/state estimate.  (Presumably, the uINS-2 data/estimates will be slightly higher fidelity than the Revolution sensors, which is the premise behind why it would make sense to utilize in the flight controller as well.)

As far as the price of the uINS, you are correct that it is higher than the usual hardware, but given the performance specs (bias drift rates) it's actually quite reasonable.  Mostly for this project, it makes a good deal of sense because it is already part of the overall hardware package and we'd like to maximize the capability of everything in the system.

I'm still trying to understand the LibrePilot code architecture to see where the right place to begin by parsing messages from the uINS to allow those data values to be delivered to the controller.  Any advice on where/what to look at/for? 

Thanks so much everyone!

-mark


hwh

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Re: Advice for integrating an offboard INS?
« Reply #5 on: May 18, 2016, 11:36:13 pm »
probably flight/modules/GPS/ and flight/modules/Sensors/

What accelerometer, gyro, gps, and barometer chips are on these expensive boards?  I couldn't find any pictures close enough to identify what sensors they're using.


Re: Advice for integrating an offboard INS?
« Reply #6 on: May 18, 2016, 11:59:40 pm »
Thanks hwh,

I'm not sure what the sensor part numbers are, but you might be able to contact Inertial Sense about it directly.  Here is a datasheet for the uINS-2: https://inertialsense.com/download/uins-2-datasheet/?wpdmdl=204.  I think the biggest value of this unit is that it is temperature calibrated on a rate table, so the gyro and accel temp biases are minimized.  If after the unit is talking to the Revo, we might get a chance to report back if we see a performance difference from the compensation carried out on the uINS over the Revo's sensors.  I'll let you know if we make it that far!

I'll get to work in the flight/modules/GPS/ and .../Sensors/.  I've started looking through sensors.c already, and working my way from there. 

Thanks a ton for the insights!

-mark
« Last Edit: May 19, 2016, 12:55:21 am by mcsauder »