Have you considered the option of using two different APM for the two flight modes (hover and fixed wing)? is it possible to use two different APM on a single platform?
Excellent Stephen, It seems to work very well indeed and from what I could see transitioned very well to horizontal and vertical flight.
Really good job.
I do wish you luck with the APM though I know that with Arducopter alone they are almost out of code space so you are going to need to use a shoe horn.
Although your design incorporates 2 servos I do not believe they permit "controlling" the propellers in directions that would be conducive to solving this problem.
Actually, using the differential pair on the front solves the torque issue pretty well. The front pair of motors can be approximated as a single rotor/disc, its area the sum of the two smaller areas roughly, and its torque contribution is determined by the offset angle between the two thrust vectors/lines. Thus, in this view, the vehicle is approximated as a bicopter with all torques canceled. The front pair is itself torque-neutral, so long as both motors are given about the same setpoint, which is true at steady-state hover, and use counter-rotating props (The left motor is CW, the right is CCW). The video I posted a day or two ago shows the system working correctly: https://vimeo.com/60922178
I'm itching to get around to merging the ArduCopter and ArduPlane code bases: I'm using MultiWii 2.1 for the time being as it is easier to code, but of course, not autonomous. I have a APM 1.x that I've been using in my wing which I'll swap into the Orange Hawk when I am ready to attempt the crossover. Probably later this spring or summer.
One other significant problem is that while ArduCopter would happily drive it as a tricopter and ArduPlane would probably drive it as an airplane, each batch of firmware nearly completely uses up the entire APM memory, so you would not be able to use it for both.
However, in a month or 2 the PX4 offers a solution to this problem, plenty of memory to run both.
I have been messing around with some designs for a 4 rotor version with a 5th puller prop.
I understand your front propellers rotate forward, and in forward flight it seems like it would probably work.
But Tricopters require a servo to mobve the one propeller that does not rotate in the same direction as the others in order to allow it's adjustable offset to prevent prop torque induced spinning of the entire airframe.
Although your design incorporates 2 servos I do not believe they permit "controlling" the propellers in directions that would be conducive to solving this problem.
Normally it would be done by rolling the back propeller from side to side on your design.
This can probably be made to work, but I do think you might need to consider servo driven offset of your back propeller then you could also use existing Arducopter tricopter APM code to operate in multicopter mode.
You might want to look at tricopter design a bit more thoroughly, it is a hybrid unlike the propeller symmetrical Quadcopter.
In any case I would very much like to see you get it to work, it is a very tidy design.
Comments
Hey stephen,
Have you considered the option of using two different APM for the two flight modes (hover and fixed wing)? is it possible to use two different APM on a single platform?
Excellent Stephen, It seems to work very well indeed and from what I could see transitioned very well to horizontal and vertical flight.
Really good job.
I do wish you luck with the APM though I know that with Arducopter alone they are almost out of code space so you are going to need to use a shoe horn.
Actually, using the differential pair on the front solves the torque issue pretty well. The front pair of motors can be approximated as a single rotor/disc, its area the sum of the two smaller areas roughly, and its torque contribution is determined by the offset angle between the two thrust vectors/lines. Thus, in this view, the vehicle is approximated as a bicopter with all torques canceled. The front pair is itself torque-neutral, so long as both motors are given about the same setpoint, which is true at steady-state hover, and use counter-rotating props (The left motor is CW, the right is CCW). The video I posted a day or two ago shows the system working correctly: https://vimeo.com/60922178
I'm itching to get around to merging the ArduCopter and ArduPlane code bases: I'm using MultiWii 2.1 for the time being as it is easier to code, but of course, not autonomous. I have a APM 1.x that I've been using in my wing which I'll swap into the Orange Hawk when I am ready to attempt the crossover. Probably later this spring or summer.
-Steve
One other significant problem is that while ArduCopter would happily drive it as a tricopter and ArduPlane would probably drive it as an airplane, each batch of firmware nearly completely uses up the entire APM memory, so you would not be able to use it for both.
However, in a month or 2 the PX4 offers a solution to this problem, plenty of memory to run both.
Great Concept,
I have been messing around with some designs for a 4 rotor version with a 5th puller prop.
I understand your front propellers rotate forward, and in forward flight it seems like it would probably work.
But Tricopters require a servo to mobve the one propeller that does not rotate in the same direction as the others in order to allow it's adjustable offset to prevent prop torque induced spinning of the entire airframe.
Although your design incorporates 2 servos I do not believe they permit "controlling" the propellers in directions that would be conducive to solving this problem.
Normally it would be done by rolling the back propeller from side to side on your design.
This can probably be made to work, but I do think you might need to consider servo driven offset of your back propeller then you could also use existing Arducopter tricopter APM code to operate in multicopter mode.
You might want to look at tricopter design a bit more thoroughly, it is a hybrid unlike the propeller symmetrical Quadcopter.
In any case I would very much like to see you get it to work, it is a very tidy design.