Which fixed-wing autopilot outputs accurate attitude and airspeed data


#1

Hi, I’m new to this forum so excuse me if this is off-topic.
I would like to incorporate wind speed and direction information into XCSoar (the open-source navigation application for glider pilots). I’m looking for a system that includes an airspeed sensor (probably a differential type MS4525DO) an accurate Karman filtered heading output, and GPS. Gliders spend long periods circling to gain height so gyro drift is important. I understand that I will have to modify the code to output the data in NMEA format, so open source is necessary.
I’ve done some work using the Firetail system but have run into magnetometer and gyro drift problems.


#2

OK, maybe that was too general a question.
It appears that Raspberry Pi is a much easier platform to develop on as it’s powerful and runs linux natively. Arduplane appears to be a candidate autopilot and the Navio2 board could provide the sensors including airspeed and GPS. However, reading diydrones forum posts it seems not straightforward to output a subset of vehicle data from Mavlink. This makes me think I must be missing something because many users would be doing this. There are posts suggesting that the simplest way of getting sensor data is using roscopter. Is anybody using this as a means of accessing accurate vehicle attitude? I want to output actual vehicle attitude data via an NMEA message.


#3

Have you considered the pixhawk system? It’s fully open source and runs the ardupilot firmware. I know the fixed wing software actually has a wind estimator included to ensure the uav tracks the correct patch over the ground so you might want to look into that. Also any of the arducopter systems are able to record datalogs, and you can record both the raw sensor data and also the calculated airspeed.

There are two options for differential airspeed sensors, an analogue one, and a more precise but expensive digital one.

Ardupilot has a fairly well written kalman filter and doesn’t have any major gyro/compass drift issues as they are constantly compensated for but I don’t know the exact stats. Some ardupilot powered UAVs can fly several hours with no issues.


#4

Total newbie trying to learn some code and build my own EFIS display. A bit overwhelmed trying to get a good start. Figured a Pi3 creating my own GUI. Would like to use the telemetry output of the PX4 for all the different parameters. Is there somewhere I can find the output type and code so I can use the different parameters for my GUI, or do I need to buy separate sensors and input via I2C?


#5

If you want the sensor data you can access it all via MAVlink serial protocol via one of the UART ports (Or USB) on the PX4

Full details on MAVlink can be found here - http://qgroundcontrol.org/mavlink/start

And then depending if you use arducopter or ardupilot firmware on the PX4 the full command list will help you get the parameters you need.