multiwii offset board position - not centrally mounted

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scanman
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multiwii offset board position - not centrally mounted

Post by scanman »

if I use a multiwii mounted on a qaud copter in an offset position (i.e. to the left side) or mounted on one of the arms do i have to change any settings in the code?

xoxota
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Re: multiwii offset board position - not centrally mounted

Post by xoxota »

I'm no expert, but at a guess, I'd say your Yaw calibration would probably be way off. I think it's best if you place the board as close to the CofG as possible, (whether that's at the center of the airframe or not is not really relevant).

For example, if you'r flying a Quad in "plus" mode, and you have the board way out on the right-hand arm, yawing left will generate a "forward" signal on the ACC, and yawing right will generate a "backward" signal on the ACC.

Rolling left would generate an "up" signal on the ACC, whereas rolling right would generate a "down" signal. You would need to rewrite the signal processing code to ignore these (in your case) irrelevant inputs. And the strength of these signals would vary according to the distance of your board from the CofG.

Supporting variable geometries like this is an interesting and tricky problem. For the most part, the MultiWii code gets around it by assuming that your board placement is at or near the CofG

*disclaimer: I'm making a lot of assumptions here, so someone please correct me if I'm wrong.

EDIT: You could maybe move the CofG closer to the board by moving the battery under the board (ie: the more "heavy stuff" nearer to the board). But that wouldn't solve the problem completely.

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jevermeister
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Re: multiwii offset board position - not centrally mounted

Post by jevermeister »

doesn't matter for the gyros. the angular velocity stays the same.

scanman
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Re: multiwii offset board position - not centrally mounted

Post by scanman »

thanks for the advice i guess the only way know for sure is to test it! I know some of the other boards like open pilot have somewhere where you can put in an offset, i guess i was hoping multiwii had a setting somewhere i could put in : "5cm to the left".
Its for an ecilop type frame where there is a big central area containing the free-swinging camera and battery counterweight, so the 60% of the COG will be independant of the quad frame.

I will get the frame, build it, and report back! Lets hope the strength of the irrelevant signals is not too strong!

nicog
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Re: multiwii offset board position - not centrally mounted

Post by nicog »

scanman, I have one naze32 on an ecilop. I put it center front (I made the holder).
Any issue concerning the gyro mode flight, perfect behaviour. I do flight very little in level mode, and no problem at all. So go and use it uncentered.

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