Hopefully we won't run into that. The round tube we felt would be =20 very rigid (compared to some of the other implementations we've seen), =20 and we at one point had PID crudely working on one axis and could see =20 it correct somewhat decently. We've also engineered the motor mounts =20 to be "slideable" so we can change moments and somewhat alter the =20 dynamics of the copter. That thrust test was an earlier one. With proper wiring, diff props, =20 and better code later, we got 10-lbs, 7-oz of thrust. Yes, we're =20 using a scale to measure thrust. And the 5lb weight is with 2 @ 5000 =20 mAH LiPo batteries. so we should get quite a bit of flight time. We're close now, so will find out soon what issues we run into. Also pushing out of the PIC-tag subject area here, but guessing that =20 "PIC" earlier in this sentence and a second time in this same sentence =20 will keep me legal. Cheers, -Neil. Quoting Sean Breheny : > Hi Neil, > > It looks like you guys are doing a pretty good job! Nice thrust test > video. Were you using a scale to measure the thrust? > > Well, perhaps you will be lucky (or we were going about things wrong), > but we found that you can't really tell how good your mechanical > design is until you try to control it automatically. Once you get all > the electronics/sensors, etc. on-board, the weight tends to be more > than you had expected. More importantly, the structure we first tried > tended to have vibrations in it which were in the same frequency range > as expected vehicle dynamics, so we couldn't just filter them out. We > had to go back and re-design the structure with tiny steel cables to > tension it like a WWI biplane and make the structure stiff enough that > the vibrations were negligible. The effect of the vibrations was to > make the sensors move relative to the props and violate the simple > rigid-body assumptions of our control model. > > Sean > > > On Fri, Feb 11, 2011 at 12:01 AM, PICdude wrote: >> Quoting Sean Breheny : >> >>> ... In my experience, as far as basic hovering and >>> level flight go, the quadrotor is very challenging from a hardware >>> perspective (i.e., making something light enough yet powerful enough >>> to fly, making the structure stiff enough, etc.) but if you have done >>> a solid job of the hardware, the control problem itself is fairly >>> straightforward. >> >> We saw this as the easy part. =A0We're currently getting (for our >> quad-copter project) 10.5 lbs of thrust with ~5lbs weight, so that's a >> pretty significant payload. =A0The PID code has had us head-scratching >> for a bit. >> >> http://www.veisystems.com/nose/quarc.html >> >> Cheers, >> -Neil. >> >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .