APm 2.5 W/ T-copter

The frame isn't the important part as it's just the method of binding the motors together. Having two motor booms in the case of a T versus three in the case of a Y does not matter.

What does matter is the spacing of the two leading motors versus the spacing to the tail motor. The system initially expects a equal distance between each motor. Change that to an uneven Y or T and the system can accept that change by tuning the PIDs for pitch and then tuning separate PIDs for roll. The downside is that you will now need to avoid flight modes (super simple) that orient the craft for you (someone else more familiar with the code might want to weigh in on that).

Norizal is correct, the APM only has to be mounted on the center axis, not the center point if the point chosen is stiff relative to the motors (the center axis rotates the same). But Bob is also correct in that the flight control parameters expect to see the accelerometers located close to the center of the triangle. The further out the APM is from the center, the larger the pitch accelerations (roll accelerations remain the same), hence the more disconnected the pitch and roll PIDs. So your PIDs for pitch might be quite different from standard setup.

P.S. If going for a custom motor layout (not evenly spaced), find the control-center of your ship. Draw a line between each motor. Bisect those lines. At the point of bisect, draw perpendicular lines. There will be a place where all three of those perpendicular bisecting lines intersect. My gut says to keep that point within the perimeter of the three motors and place the APM at that point. Happy flying.

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Al Creigh June 12, 2013 at 10:50am

This is all great information I am curious tho if I do wish to use the guided autopilot and other flight modes like stabilization will this be effected? I would like the option of using these flight modes.
MR60

Forrest Frantz June 12, 2013 at 7:28am

The frame isn't the important part as it's just the method of binding the motors together. Having two motor booms in the case of a T versus three in the case of a Y does not matter.

What does matter is the spacing of the two leading motors versus the spacing to the tail motor. The system initially expects a equal distance between each motor. Change that to an uneven Y or T and the system can accept that change by tuning the PIDs for pitch and then tuning separate PIDs for roll. The downside is that you will now need to avoid flight modes (super simple) that orient the craft for you (someone else more familiar with the code might want to weigh in on that).

Norizal is correct, the APM only has to be mounted on the center axis, not the center point if the point chosen is stiff relative to the motors (the center axis rotates the same). But Bob is also correct in that the flight control parameters expect to see the accelerometers located close to the center of the triangle. The further out the APM is from the center, the larger the pitch accelerations (roll accelerations remain the same), hence the more disconnected the pitch and roll PIDs. So your PIDs for pitch might be quite different from standard setup.

P.S. If going for a custom motor layout (not evenly spaced), find the control-center of your ship. Draw a line between each motor. Bisect those lines. At the point of bisect, draw perpendicular lines. There will be a place where all three of those perpendicular bisecting lines intersect. My gut says to keep that point within the perimeter of the three motors and place the APM at that point. Happy flying.
novrizal herdananto June 12, 2013 at 4:58am

Should be the same with tricopter.. As long as the apm is mounted on the center axis..
Developer

Randy June 12, 2013 at 4:56am

T-copter = tri copter? If 'yes' then 'yes'.

This reply was deleted.

ArduCopter User Group

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