A while ago I posted about ESC I was making with FOC motor control.
Now it was time to mount it on something. In the video propellers are 7 inch plastic, I decided that it is too dangerous to have three 15 inch CF props spinning in confined space where I have nowhere to run should something go wrong.
Video shows arming the system when propellers are aligned (so they don't scrape on the floor), rotors tilted to 0 deg and then to 90 deg vor vertical takeoff/hover, motors run for a few seconds and are then stopped, realigned, tilted to 0 deg and motors and servos are powered off.
Comments
interesting!
how do you do the rotation to a particular angle? I can see how you would know the angle relative to power-on, but how do you know the power-on angle of the props?
ahh, I see you've already answered, sorry. You have an absolute position sensor. Nice!
Hi Hugues, here's some info on FOC, with comparision to block commutation (method that is used on almost all ESC's): link.
It has benefits, one of which is that you can precisely position the rotor :), and with today's microcontrollers and advanced motor control libraries FOC is easy to implement and if you use methods to reconstruct three phase currents from single shunt it won't cost more than current ESC's.
Hi Marc, commercialized maybe someday in the future, but I don't know if there is a market for over-the-top ESC's with 300A MOSFETs :). Communication right now is RS485 with dynamixel ver.2 protocol. There is CANBUS hardware on the board and uC has enough power and flash to handle CAN communication, so sometime in the future I plan on implementing UAVCAN - I think we would all benefit from hardware that can be on a bus and report status to autopilot for early warning of potential problems.
Hi Nick, yes I use AMS 360 degree absolute positioning sensor for rotor position feedback - I wanted to be able to "park" rotors in precise position for rotor tilting on the ground.
Hi Maxime, I considered dynamixels but the price was too much (~200$ for each, three needed so 600$ - way too high), so I tried chinese clones - this one. But I ran into a problem - one of three servos stopped working and that got me so frustrated that I made my own electronic to replace the one that was inside. If I will ever have the time I will try to also replace clone gears with dynamixel spare parts with magnetic encoder to get better positioning, but for now what I have works and I just don't have the time for additional upgrades.
What are the advantages of FOC motor control versus calssical ESC function, in our drone applications ?
Hello I am very interested in this great idea, since I am myself into developing hobby ones!http://diydrones.com/forum/topics/quad-motor-on-a-mechanical-arm-2-...
Can you disclose the type of servo you are using as well as the feedback system? Read about your latter post where you focused about ESCs and did not enter FOC too much. Did you consider using smart servos like dynamixels? If yes why did you discard it? Is it simply RC servos with external feedback?
I plan to add a second degree of freedom on the horizontal axis, have you ever considered this matter?
Best regards, Maxime
Hi Jure,
Do you use Hall sensors for rotor positioning?
BR
Nick
I had to watch a few times before I got this. Brilliant. So it seems you have achieved your home brew ESCs with FOC control. Are these going to be commercialized? What are you using? CANBUS?