Recently, I was asked to shoot some stills and footage of a sportfishing yacht for a client. We went out on a beautiful morning with no wind and an almost perfectly calm ocean. If you wanted optimal conditions, its wasn't going to get much better than that morning.
I connected the battery to my custom built quadcopter running APM 2.6. It would not arm. We were sitting about 4 miles off shore, not moving, gently rocking on an ocean about as calm as I've seen it. I was trying to launch from the middle of the lowest platform of the boat, at the stern. I had good GPS. Everything else checked out. It would not arm.
As soon as I got back to dry land, I tried it again. It armed without hesitation. Apparently Arducopter needs to be on solid ground to initialize. So what next?
In doing my research, I found this thread:
Chris Anderson says, "Starting with 3.3, calibration on a moving surface will be easier. As far as the gimbal goes, it depends on the make. The 3DR Solo gimbal will calibrate on a boat, but not all will"
I have two points here. First, the gimbal is not an issue for me. Simple BGC lets you turn off the startup accelerometer calibration. It still works fine if you don't let it calibrate every time. Second, I'm using APM 2.6 so I'll have to upgrade to Pixhawk if I want to use Arducopter 3.3.
Arm on Shore first
Next, I found this thread:
The first person to comment boots his quad on shore, then takes it powered up, in his kayak. I see where that could work but that only gives me the use of one battery.
Bring a Laptop?
Considering the idea of calibrating on shore, what if I brought my laptop on the boat with me? I could power up on shore then launch from the boat and fly the first battery. After I return to the boat, I could connect APM to the laptop with USB, then disconnect and swap the flight battery for a fresh one. Would this work? I will do some experiments and post the results on this thread.
Dynamic RTL is a Separate Issue
I've already posted the desire for Dynamic RTL, where the copter returns to YOU instead of the original launch location. Obviously this is desirable for any mission launched from a boat. It seems like a much easier feature to add. The Tower app already knows your GPS location in order to do "follow me" mode. The DJI Inspire already has this feature. My thread is here:
I will post more information as I find it. Hopefully this thread will be a resource for those wanting this feature.
Paul and I spent a day-ish on the problem earlier this week and Copter-3.4 (not AC3.3 which is about to be released) will include "boat mode". To take-off from a boat, the user will need to set the INS_GYR_CAL parameter to "0" (normally it's "1") which will disable the gyro calibrations. There's a new pre-arm check that the EKF's attitude is ok. It might take 30 seconds or so for that check to clear if the vehicle is being moved a lot but still, it should work.
So, not in Copter-3.3 but definitely in Copter-3.4 and once we start beta testing that version you'll be able to give it a try.
For older flight controllers that won't take 3.3 or 3.4, what do you think about arming on land and then keeping the FC powered with a USB battery? Any issues?
I guess that would work. Just need to worry about a couple of things:
"Every PX4 firmware's startup is in “boat mode”. We never do boot time gyro calibration because of concerns of unreliability of the method."
Just another option to supply Power to pixhawk, without using the main onboard MultiRotor LiPo batt,
which may be another suitable solution for pre-launch calib etc, then taking it, power-on, to boat etc.
I use a std In-Car (Cigarette-lighter-socket) to usb charger/supply dongle.
Connect the Dongle to a std 12V/7AH (gel-type) batt, instead of the Car-Cig-lighter-port.
One can power the Pixhawk with this for an hour or two, via the usb cable connected to dongle usb port.
Once ready to fly, connect main Lipo, disconnect usb cable from Pixhawk.
Use a std off-the-shelf-batt charger to charge 12V batt.
I just did a few successful tests, launching from my "boat simulator"...
This video presents the following solution:
1. Connect a flight battery on land, arm (power up) the motors for a few seconds, then disarm.
NOTE: At first I tried simply connecting the battery on solid ground, then moving the quad to the "boat simulator" and it DID NOT WORK. I had to arm the motors for a few seconds while on solid ground, then disarm, then it worked from the simulator
2. Leave the battery connected and go out in the boat.
3. The drone should now arm and launch from the boat.
4. Once you've flown your first battery, you'll need to connect the flight controller to a laptop with a USB cable.
NOTE: I have NOT CHECKED other USB power sources like portable cell phone chargers, etc. I'm afraid they COULD DAMAGE the flight controller!! Can anyone with engineering knowledge of the boards verify if portable USB batteries would be safe to connect to APM or Pixhawk??
5. With the USB connected, disconnect the original flight battery and connect a fresh battery. In the video, you'll hear it play a different sequence of startup tones. Does anyone know what this means?
6. Disconnect the USB cable. You should be able to arm and launch from the boat again.
7. Repeat for additional flights.
I HAVE NOT VERIFIED if my temporary solution will work with IRIS or SOLO drones but they should all work the same right? Hopefully some of you will test my method and post the results here.
Usb batteries, as long as they are not cheap and bad designed, they work ok without damaging the Pixhawk or APM.
Or they will destroy your cellphone, i think :)
Any 12 Volts to USB (Which is 5 Volts) normally will work.
So a 3S Lipo battery when fully charged is (4.2 x 3) = 12.6 volts.
If you don't know how to implement a such "gadget" then Google "12 volts to usb" to find many dealers of such little dc dc converter. :-)
My house (and new launch facility) in Sydney Australia. I am about to scratch build a 1m X 1m, dynamic self levelling launch pad for the upper deck using existing "beefed up" gimbal hardware. (I hope)
Anyone see what problems I might run into. I would appreciate any comments..