Had again a really nice saturday flying with my Hashcopter. Took first images from the copter with my 800 gram camera. Pictures didn't turn up to be anything spectacular but copter flew nicely at high altitude and was very controllable. I'm still waiting for parts to arrive for my camera stand and FPV equipment. For that reason camera stand was just taped to nice position and images shot by feeling.
I actually had some difficulties with cheap ESCs not arming the motors properly. This was due to it being -25 degrees Celsius temperatures and electronics just needed some warming up occasionally. Actually so did the pilot. Eventually one of the ESCs broke down and flying was over for the day.
Because ESCs did some tricks on me I accientally ended up testing what happens when one of the motors shuts down. I was landing the copter still hovering at around 20-30 meter height when one of the motors just stopped. It was nice to realise everything was still controllable and I was able to land to copter nicely to a snowy field. It could have been flown with just 7 motors despite the heavy camera hanging under the copter.
All saturdays pictures with better resolution:
http://www.markusjahn.net/gallery2/main.php?g2_itemId=47419
Previous two parts of the story:
http://www.diydrones.com/profiles/blogs/weight-testing-of-8-motor
http://www.diydrones.com/profiles/blogs/arducopter-quad-with-eight
Comments
Hi Markus, i've same configuration but with 710kv motors and 13x6.5 props... can you share here your pid (in acro and stabilizer mode)? Thanks a lot!
Mark
Looks like starting from firmware 2.3beta, octo-quad is supported. This is quad configuration with with coaxial mounted lower motors. I'm thinking of converting to this to get more lifting power. I learned from someone on youtube who did this that efficiency only drops by 30% with this configuration. (i.e. 2x1kg thrust motors give 1.7 kg thrust).
The coaxial configuration saves the weight of the extra arms, and makes an octo easier to build, I think.
One question I have for you, is in the configuration page for octo, you attach two motors to ch10/ch11. Where is that located on the APM board. since it only has 8 outputs for motors?
Oh i see.
I think it would be cool to add 1K resistors on the signal wire for each ESC, just before the Y points.
That might help in case one of the ESC's die and decide to output some high voltage on the signal line.
EVEN if the ESC apply GND on the signal line, it will immediately tie its pair ESC signal wire to GND too, resulting in no signal being received, and there you have a pair not working. now try to land.... :)
so could it be described that way ?
ESCs are connected as pairs with servo Y-connectors so no resistors just signals tied together. I use only one ESCs BEC to power the APM+IMU and other ESCs + and - wires are cut away.
Markus, that's great !!
very impressive idea and the best of all - that it works well just like a quad !
The landing with only 7 motors is just amazing security feature.
One question please:
how did you connect the ESC's?
did you tied together each ESC pair signal wire ?
which means 2 ESC signal wires goes to each APM output ?
did you use resistors or just tied them together ?
Just upgraded to ArdupiratesNG r.589. Will be testing with AH+PH in the following days. Did shoot some video just for test. It didn't have too bad shaking.
I have a feeling things are again going forward during next week or so...
Janne is actually using an Oktokopter. He crashed it quite badly last weekend and broke 7 propellers and bent his frame. Lots of fixing and balancing for him to do to get back to same standard.
Great job Markus, do you think you will be able to get altitude and position hold working as well as Janne's
quad. What quad and camera was he using, it was incredibly stable. Look forward to more video from your
rig especially with all that snow.
I'm using Arducopter RC2 with no changes to it except the basic settings.
I calibrated full throttle positions for ESCs separately with receiver. No other balancing done. Basic Quad stabilization takes care of small differences between motors.
Rotor-to-rotor distance is actually not at all precise on my frame. When building it I considered this to be a quad with double motors on each end and didn't bother to calculate the distances. So each pair of props is closer to each other(55mm) than the "corner" ones(75mm). Also the distance between propellers is quite big because of the large frame.
I really like the fact that my frame is a bit oversized from what is necessary. This is due to fact that it can go to higher altitude. Limiting factor on altitude is how long its orientation can be seen and bigger frame just helps on that.
Here is couple of nicer aerial photos taken this week:
I have not let the copter stay out to cool down. Actually if I do that my ESCs don't want to initialize. They just start beeping like no radio signal. That could be caused by APM but I believe it's just the speed controllers.
I've noticed no other problems caused by coldness. I haven't been able to see any gyro drifting happening during flights.
At first I did some jumps upside down and weird yawing but that was due to starting the flights in stable mode. If you keep your copter in stable mode some time it is alway going to some direction when trying to fly. Way I avoid this is to keep Copter in acro mode start the motors and give them some power to almost lift off the ground. Then switch to stable mode and take off the ground.
What kind of issues do you have?
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