Just as inspiration: we followed a less sophisticated approach to maximize the flight time (ca 35min) of our brushless + 4.2Ah + 600gr payload twinstar. Not the fancy polar from airspeed but: "an onboard realtime current sensor" -> search for cruise throttle that yields minimal Amps.
BTW: If you use the polar to define the optimal speed: does this include the effects of varying motor efficiency with speed? (if your props are too big, maybe a lower speed might yield a better total efficiency & vice versa)
For the climbing we optimize vclimb[m/s]/current[mA] to reach a maximal altitude[m] out of 1 battery[mAh]. This is more difficult to tune as there are 2 parameters.
-Christophe
On Fri, Dec 3, 2010 at 9:26 PM,
<address@hidden> wrote:
more details? no problem
I started with a regular setup of a twinstar. probably like everyone else... termopiles gps nothing special
what is special is that during the time I changed to brushless motors
2 x viper2700 with 2x 25 ESC
and a 5Ah lipo
in this configuration I made 30 min
after a while i started playing with different pressure sensors, we already discussed that
and then I wrote my one vertical control and implemented a bunch of new autopilot modes that enables my twinstar to fly constant airspeed with or without throttle
due to these new modes I was able to gain the polar and to find speeds for best glide and minimum sinkrate
so with a slightly pimped flightplan I made 46 min with 5Ah
so what really disappointed me no matter what I tried I couldn t make the 60 minutes
no I just put a lot of capacity in it ... I know 5Ah is a already a lot but now there are 12Ah in this little airframe and they just fit perfectly
I already figured out the polar and you can clearly see that the speed for best glide is much higher as well as the speed for minimum sinkrate
there is only the time problem for me and the fact that I m a one man show so I have to carry everything on my back to the airfield and be operator and safety pilot at the same time
during the summer there was no need to ask for people to help me because everyone wanted to see it but right now at these low temperatures it is getting really hard to find someone freezing especially when its only for an endurance test and the plane is only doing wide circles.
so thats it
a piece of foam and a lot of battery -- imagine how much more should be possible even with this setup
cheers