Micro Qudrotor Parts Selection

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Hello.

I wanna build my first micro quadrotors which can be used to design a multi-robot system to carry out a load cooperatively.

Each micro quadrotor should able to have a continuous flight time of 10 or 20 mins; the dimension of each micro quadrotor must be at most 10 by 10 cm.

Now my question are:
1- Is PX4 Pixhawk Lite is suitable as the autopilot? If not could you please suggest another autopilot?

2- What type of motors are more proper for a micro quadrotor? Coreless or Brushless? and Which manufacture?

3- Any suggestion on battery?

Thank you in advance.
 
Do you have experience building any other scale of multirotors? I could be wrong, but your expectations strike me as almost entirely unrealistic. I just don't think you're going to get the flight times you want in a quad of that size. I built this, it's 17cm corner to corner and I get about 8 minutes max. Without the camera and video transmitter, it'd probably get 10, but that's on the lowest end of your range, and the quad is almost 2x as large. I'm (slowly) working on a 15 cm version, and that's about as small as you can get while carrying a "standard" size flight controller like an APM or Pix Mini and a GPS. You'd have to go down to 3 inch props to go smaller, and then you'd never get even 10 minutes of flight time.

You get long flight times with large, slow rotating props. To get something to carry a flight controller and gear capable of autonomous flights, in a 10cm size, you're going to have to use tiny props and have them screaming like a banshee to generate enough lift. Which means you'll probably get 5 to 6 minutes of flight time MAX... if you're lucky.
 
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Do you have experience building any other scale of multirotors? I could be wrong, but your expectations strike me as almost entirely unrealistic. I just don't think you're going to get the flight times you want in a quad of that size. I built this, it's 17cm corner to corner and I get about 8 minutes max. Without the camera and video transmitter, it'd probably get 10, but that's on the lowest end of your range, and the quad is almost 2x as large. I'm (slowly) working on a 15 cm version, and that's about as small as you can get while carrying a "standard" size flight controller like an APM or Pix Mini and a GPS. You'd have to go down to 3 inch props to go smaller, and then you'd never get even 10 minutes of flight time.

You get long flight times with large, slow rotating props. To get something to carry a flight controller and gear capable of autonomous flights, in a 10cm size, you're going to have to use tiny props and have them screaming like a banshee to generate enough lift. Which means you'll probably get 5 to 6 minutes of flight time MAX... if you're lucky.
Thank you so much for the information provided. This is my first experience building a multicopter.

Therefore, let's conclude your response, a 150 mm dimension is the minimum optimal length which can be used to reach a flight time of 10 mins (Indeed, we have to use 3 inch props).

The following link also suggests to use a small ultra weight brushless motor with 3-inch 3-balde propellers on 130-150 mm size frame:
F20 - FPV Series Motor - T-MOTOR

My question is now about choosing APM or Pixhawk Mini. Which of them is suitable for autonomous flight control of a quad copter?
Suppose at the first step, my quadrotor should autonomously take off and hold its position at a per-specified height.
Is there any source code for this task on the web for APM or Pix Mini?
 
The following link also suggests to use a small ultra weight brushless motor with 3-inch 3-balde propellers on 130-150 mm size frame:
F20 - FPV Series Motor - T-MOTOR

T-Motor make really good motors, although the concern I'd have is the high KV (rpm per volt). As I said, larger props spinning slower are more efficient than smaller ones spinning faster. Also, fewer blades are more efficient than more - 3 is more efficient than 4, 2 is more efficient than 3, etc.

You can still get away with 4 inch props on a 150mm quad, but just barely - a standard size flight controller will need to be mounted rotated 45 degrees to clear the props. I'd probably try the lower KV version of those motors with 4 inch 2 and 3 blade props. The higher KV version might be desirable for FPV racing, but you probably don't need maximum performance.

My question is now about choosing APM or Pixhawk Mini. Which of them is suitable for autonomous flight control of a quad copter? Suppose at the first step, my quadrotor should autonomously take off and hold its position at a per-specified height. Is there any source code for this task on the web for APM or Pix Mini?

Any flight controller that runs the APM firmware will be able to do autonomous flight reliably assuming it has a GPS and the GPS is shielded enough from any RF interference from the rest of the quad. Autonomous flying is where APM really shines. You CAN do it with smaller flight controllers like the CC3D Revo Nano or maybe some Naze32s running the iNav firmware, but from what I've read, it's not as easy or reliable as APM.

In either case, just build really light and shed anything not totally necessary. If it's launching from another vehicle, you could have it mounted on the "mother ship" such that you don't need to have landing gear/legs on the quad, just have it lift off from that and land on it's battery. Speaking of the mother ship, if it'll be an aircraft itself, you might need to arm the little quad before the carrier takes off (unless the latest versions of APM include the ability to arm while in motion). If you do need to arm more than a short while before the little quad needs to take off, you might have to work out some way to power it from the carrier vehicle so as to not deplete the little quad's battery while enroute to it's take off location.

Sounds like a cool project.
 
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Thank you for answer.
Here is a list of parts I've selected:

Motors: T-motor F20 3200KV
Props: Gemfan 4x4.5 and/or RotorX 3-blade 30x40
ESC: Emax SIMON 12A
Frame: Shendrones Mitsuko 150
Flight Controller: Mini APM v3.1
Battery: TATTU 1550mAh 3s 45c Lipo or TATTU 1300mAh 3s 75c Lipo

I would be glad to hear any other suggestions or comments you may have.
 
Thank you for answer.
Here is a list of parts I've selected:

Motors: T-motor F20 3200KV
Props: Gemfan 4x4.5 and/or RotorX 3-blade 30x40
ESC: Emax SIMON 12A
Frame: Shendrones Mitsuko 150
Flight Controller: Mini APM v3.1
Battery: TATTU 1550mAh 3s 45c Lipo or TATTU 1300mAh 3s 75c Lipo

I would be glad to hear any other suggestions or comments you may have.

Looks good overall. Few thoughts:

Many people don't like the idea of 4-in-1 ESCs because if one is damaged or fails, you loose all of them, but I have several and have never had a problem. And prices have fallen to the point where it wouldn't hurt too much to have to replace one for a failure in a single ESC. Add up the weights for 4 separate ESCs and compare that to the weight of a 4-in-1, and try to account for the extra wiring and solder that separate ESCs require. At the scale you want to build, literally, every gram counts.

You don't NEED it, but if you can shave off enough weight in other areas, consider a voltage/current sensor. It'll let the flight controller monitor the battery state and initiate an RTL or land failsafe if the battery gets too low. It's saved my bacon more than once. This one is really small and light: AUAV Power Module (ACSP5) 10S-LIPO

Lastly, you absolutely don't need batteries with that much discharge capability. Check the specs - the higher the discharge rate, the heavier the battery. On such a small quad, and one that won't be flown at max performance, you probably don't need over a 20C discharge battery. Check out ReadyMadeRC, when I was looking for batteries for my little 170mm, their orange 1100 mah 35c was as light as I could find for a 1100 pack.
 
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