Hi Guys,
So I have been working for a couple (few) months an this design it was a long held beleif of mine that ducted propellers would only have a detrimental effect on flight efficency. After discussing the dynamics
of a ducted fan and its effects on efficency I became aware of the potential for such a design. One of the largest hurdles was to create a duct design that would be light, durable and hold up to the forces applied during flight. We wanted to have a minimal prop/duct clearance but avoid any contact.
A carbon fiber design was the only logical solution. For all four props we were able to maintain the same or less weight. Also each duct was designed to hold two motors each. The clearance is <= 1mm.
We just had our maiden a couple days ago and I would say initial results were not bad. There is a lot of work to get the efficiency gains hoped for.
I am experiencing some problems that don't indicate a clear solution for me so I thought I would reach out for some insight from others.
On takeoff the aircraft seems to be fighting with itself. There are no clear indications of high or low PIDs such as jittering or sluggishness. What I notice is a constant yaw correction from the controller. At some points during the flight I will be attempting to correct or maintain a heading and the aircraft is steadily rotating regardless of my input. It also seems to have a noticable problem with altitude control.
I suspect there is some vibrations that could be aggravating the problems. I have looked at the accx, accy, accz values and noticed they did not look normal either. I noticed previous vibration readings in log files fell more in line with peaks and valleys. Here and more pronounced in previous tests the accx and accy are seperated quite a bit.
I will get some video tomorrow and post it to give a better idea of what i am attempting to correct. I have attached a test flight log that might contain more info. Currently param is default and works well on a non ducted quad with the same core components and weight. I am also getting a lot of errors like alt disparity, acc error. The horizon view also seems to keep getting out of level after many acc calibrations that seem to fix the issue temporarily.
Replies
I don't think it is as clear as that. The motors and direction are correct. I have built more of these than I can count and have never seen these types of behavior. Currently i am getting ACCEL Inconsistent pre arm warning. The compass is spinning wildly and my horizon is at about 40 deg ( while sitting flat and still) I ran the motors up yesterday to look for significant EMI and found practically none. I continue to recalibrate ACC but it doesn't last long.
New pixhawk and gps/compass?
Its all brand new. I suspect from some other posts it could be related to the PM. I have to use a HK power module for the 6S
I find your work very exciting, I haven't seen anyone else take the time, effort and expense to develop outside the box. It appears that you must have a CNC router to make the quality parts, I used mine to make a power distribution ring, it cuts copper just fine. The options are endless. I combine parts from my 3D printer and CNC router, no limit to what can be made. I use carbon fiber to back up the 3D printed parts because they loose their strength and shape.
I tried Pixhawk once and got similar results, I shelved it and went to a proven controller. Very difficult to develop hardware with electronics that don't cooperate.
Ed
A constant yaw could very likely be caused by one or more motors being rotated sideways. It won't take much to introduce a yaw due to this... it will be consistent in direction of yaw and the amount of yaw will be proportional to thrust. Make sure all of your motors are parallel to each other.
Every effort was made to try to install the motors vertically in each motor housing. I will pay close attention to this possibility during test flights tomorrow. Thanks for your response.
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