Could I use ALT-HOLD for under 10m lift offs i.e. place the copter on the ground and push the throttle stick up.
If not what mode can I use to assist in such lift-off.
I see in many video of ArduCopter people do clean vertical lift-offs indoors. When I try to do that I drift to one direction or another. The propellers are balanced ok, the frame is balanced.
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As the others said : if you make sure your copter is properly "levelled", meaning the accelerometers are properly calibrated AND your frame is true and straight AND your props are balanced AND your center of gravity is nicely in the middle, then it should liftoff straight without a problem.
Indoors, I can lift my hexa off the ground and let it fly for half a minute without touching anything else but throttle. Oh, you must lift it higher then 0.5m though (groundeffect), and the walls (or other objects) must be further away then 5m, else the returning air from the wall will blow the copter away.
HI Dara, you cannot. Since Alt-hold will try to keep the last stable altitude before the switch was flipped. So, if it was flipped before take off, it'll want to stay on the ground. (Assuming it works at all) As well, althold does not keep position, just altitude.
Drifting always occurs, since there's no accurate way of the copter knowing what position it is in exactly. Loiter will attempt to keep position with GPS, but even GPS is not accurate enough for that level of position keeping. Although, recently an Optical Sensor has been introduced that looks under the quad to try and keep it in position. Though it too has limits.
The best way to avoid drifting is a steady hand, practice and of course a well balanced copter with balanced props.
Most lift off you see indoors are on stabilize or simple mode. No assisted take-offs.
Have you run the auto-trim calibration?
Im not sure what would happen if you: spin up the motors up to 10-15% while the copter is on the ground. Then switch to ALT Hold, then give full throttle to increase the set alt variable. I dont think this is a good idea, as the rate of climb is very low, so if something goes wrong, you're not in full control.
Im still a noob so iv got my pitch and roll sensitivity set to 60% so its half as sensitive. The first time i flew my arducopter, the first time i flew any rc was inside and it worked fine.
If you worried about drift, then do the auto-trim calibration. Fly the quad as steady as possible while in auto-trim and above ground effect.
G:)