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Permalink Reply by Dr Mike Black on September 9, 2010 at 12:01am

Hi Space,

yes...lol....as an experiment

We have a gimbal camera mounted beneath said airframe, with a ArduIMU mounted at the top of the gimbal itself.

Doing it this way has rendered allot of computations irrelevant, so that when the aircraft rolls or pitches, its relative to the last commanded cam input.

so say you are 45 deg from 0(forward relative to aircraft) the IMU is seeing the heading of the cam (we have a mag nailed to it) it tries to compensate for rotation of teh aircraft(yaw) so that the cam stays pointing at heading last made. this bit is a but screwy to be honest...sometimes it works ok other times it gets all confused..so still working on that..

but we have used only the pitch control to comp for 2 axis movement in teh airframe as the imu always points the directon of the cam so we only need up and down.

We tried gyros....adn the results were ...erm.....poor....you need a DCM or Kalman to produce the constants to keep positioning

3 lessons we have learnt....

1 trying to control a cam with no stab and stay on a target is like rubbin ya tum and patting your head, the result of this is the propensity to upchuck, as your eyes are telling you one thing your arse is telling you summet completely different..

2 trying to fly at 400feet at 50 mph following a target doing 50mph at a range of 500 foot is VERY hard...refer to upchucking....

3 you need a seperate control for your 'opo' so hes not involved in the AP side of things....information overload occurs in very short order..

solutions:

1 stabilize the cam even at 10% comp is great, slow your servos to an to an absolute crawl as its easy to endup with over corrections due to too much movement...again upchucking is likely (have a wild guess how we know this! :))

2 we have had best results with alt at 1000 feet at least a 1000 feet off target, the paralaxing effect is greatly reduced, tracking a moveing object becomes very doable.

3 DONT try to fly AP and CAM at same time, get help.....trying to regain your dignity whilst hurling and trying bring an aircraft in to land adds a whole new dimention to flying, something everyone should do at least once...lol.....its so hard to see through the tears!

if it helps (cheap plug here) we are about to release a cam and board that is serial controlled from a tx, so you can zoom in, invert pic, take stills etc from a standard transmitter using 2 switches or in our case in testing using the a linear stick for zooming.

The cam we are using is the Sony FCB EX series...you can read a news paper from 500 feet..with 30% zoom.

i dont know if this helps

Mike.

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Permalink Reply by space_nut on September 9, 2010 at 12:15am

gr8 2 hear from you Dr. Mike

Sounds like you have had quite the adventure with this design. Look forward to hearing more about your cam-board

Did you reprogram ArduIMU to control servos directly or are you taking the output and feeding them to another controller then to servos?

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