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DeveloperPermalink Reply by jasonshort on March 6, 2012 at 4:41pm

Is the ducted fan on the quad? What's the goal of the fan?

APM can use a sonar and hold a tight altitude with a hard surface.

Jason

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Permalink Reply by Paul Brzeski on March 6, 2012 at 4:54pm

Hi Jason, the ducted fan is on the quad, the idea is to get a floating platform that can be moved forwards and backwards using the ducted fan without the platform tilting. to what parameters can the sonar work?

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Permalink Reply by Richard on March 7, 2012 at 1:13pm

A ducted fan seems quite likely to cause the quad to tilt unless it's exactly through the C of G, and might cause some roll regardless (fan reaction), so the chances are you won't get a very stable platform that way.

They also don't spin up or down very fast, so holding a static position would be very difficult.

How about a 2-axis mount for the 'stable platform', as used to stabilise cameras for aerial photography?

I believe the software to stabilise a camera is already available in APM, so you only need the two servos (pitch and roll) driving the platform.

"Sonar" means using an ultrasonic rangefinder to measure the distance between quad and the floor, the range and precision depends on the unit chosen, a 30cm design range should allow a very tight altitude hold.

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Permalink Reply by Ed Kirk on March 7, 2012 at 3:29pm

I am flying with ducted fans, I must be doing something wrong because I have not experienced any of these problems, on the contrary it is the most stable multicopter I have built and flown and response to the transmitter is well beyond my flying abilities.  I can grab it at the center and try to move it around manually and it really holds its position, like there is a magnetic field holding it in place.

Flying time is to short but I am experimenting with larger fan units and working with about 20% to 30% of their rated output, lower rpm motors with higher torque to achieve desired lift at half of rated RPM is giving me reasonable results on my test stand (quieter too), much better then the recommended motor / fan combination. 

EDF's are not very practical for multicopters (at this time) because of their high current draw and short flying time, but they fly better then a prop driven multicopter.  I would like to use the words better flight performance but flying time is way to short for "flight performance".

 

Ed

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Permalink Reply by Paul Brzeski on March 13, 2012 at 11:55am

Can anyone help with keeping the hover height at a constant 12" above a hard floor using sonar or another method? For example moving around a car park and not hitting the floor and keeping a constant ride height

Thanks,

Paul

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