Hi,
My quad is running on Pixhawk and I use a FlySky TH9X radio (typical DIY Quad kit from 3D Robotics). The firmware is ArduCopter v3.1.5.
This morning, my quad started flying away (it might have been because of the wind but it just didn't seem to listen to my commands). I put it in 'Loiter' mode instantly but it was a second or so after I lost line of sight. Is there a failsafe built in which orders the quad to land if it loses R/C signal? This will help me figure out the search radius
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I am not quite sure about my idea, but it seems to be related with extend kalman filter in certain vabration condition. DJI declars that their flight controller use kalman filter, and there are many crash and fly-away cases which are not explainable. And this case here is the second case I know about fly-away issue of Pixhawk since Kalman filter has been introdueced to Arducopter. They are so similar with DJI cases.
I strongly doubt that, under certain vabration condition, kalman filtertion can disconvergent to something erratic.
I am not a expert of kalman filter, so look forward the answer here.
One nice thing about using arducopter with telemetry is that a "tlog" will be produced which, even in cases where the vehicle is lost, help us figure out what happened (and it also provides the last known location of the vehicle). This helps cut down on unexplained disasters.
Saurabh, I guess you don't have a tlog?
In Arducopter 3.1.5 we use a 3rd order complementary filter which is similar, but much simpler, than an EKF. AC3.2 has both running parallel but once we are sure the EKF is more reliable we will likely switch over to it (i.e. in AC3.3).
In theory an EKF can be more reliable than a complementary filter because it provides a "variance matrix" which can be used by the autopilot to make a judgement about how well the vehicle knows it's position and attitude and even indicate which sensor has gone wrong. The complementary filter on the other-hand only provides 3 "acceleration corrections".
Great information, thank you, please excuse if this is a bit off topic, is it possible to send the mavlink data over the telemetry of a RC TX/RX and then populate the Mission Planner via com port that way?
The more I go out the less I want to carry with me, as of now the mavlink can be on a tablet through the 3dr radio, would like to be able to pick it up over the 2.4 RC TX/RX for range and to drop some other if completed redundant less capable parts.
Hi, Randy,
Thanks for the nice technical details. I will surely look into source code of pixhawk in the furture.
Hi,
Thanks for the input everyone. First things first, my quadrotor was reported to be found by a good samaritan who saw my ad in the newspaper this morning. It flew about 2 km away but landed safely in someone's garden. Other than a chipped propeller the vehicle looks OK. I still haven't put it on yet but am hopeful that it will be fine (I'm a little scared that there might have been a brown-out because the 4S battery went all the way down to 3.5 volts).
I don't have a tlog unfortunately but I can guess what went wrong. I was flying this just outside my house and for a split second the wind pushed it to a point where my roof got in the way of the LOS between the R/C and ground station and the quadrotor. That split second was enough to allow it to drift away over a crowded area which prevented my R/C from establishing LOS with it. The rest is history :P
I think the suggestion to set up a virtual wall makes a lot of sense in case the transmitter goes off while the vehicle is on the ground and hasn't even taken off.
Doesn't the pixhawk not have a ppm encoder? If he is using the standard th9x pwm receiver, then throttle failsafe isn't possible. Isn't this correct?
One way of enabling throttle failsafe is to change the th9x pwm receiver & transmitter modules for Frsky PPM modules (£50+)
Another way is to use a PPM encoder between the pixhawk & th9x pwm receiver. More on this module here: LINK
Anyway, yeah. not having throttle failsafe is scary as hell once the reality of the issue is inside your head.
The Pixhawk doesn't have a ppm encoder but arducopter will trigger a radio/throttle failsafe is the throttle is pulled low or the signal simply stops arriving.
The software just checks the range of the signal for the throttle signal, if it fall out of range and the failsafe is enabled to check this it will then run the action such as RTL as selected
Hi Saurabh,
You can enable auto failsafe action in your MissionPlanner to either land the craft, come back to base or continue with the mission if it looses signal. However if you didn't have this turned on the only info you may have from your quad would be your telemetry log if you had telemetry running at the time and it didn't lose that signal as well.
Another option for the future would be to set a radius around you that you don't want your craft to leave and it will come back "home" if it hits the virtual wall. I prefer this option to prevent flyaways because you have to be very careful when setting Fail Safe for lost R/C signal not to accidentally turn off the remote while battery is still plugged in. What will happen is your quad will shoot up and try to go back to "home" position. That's why it's best to turn this on only when you're out in the open and ready to fly.
Check in your mission planner if you had any Fail Safes turned on and good luck finding your craft.
Had similar moment but I allways would flip to manual stabilize and fly it back... Noticed that if you get interference on the FC or compass you can see really weird results... I would suggest also downloading a WiFi scanner for your cell phone and see what is near you when you take off...
If you get you quad behind a active AP (Access point) and you TX on the other side, if the AP resets the connection it can blank your RC control, possibly...
Check you calibration, and what FC are you using as really their could be allot of possible issues
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