Need to design and build 250W BLDC inverters for drones - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: February 28, 2024, 03:09:36 pm
content: Hi,We wish to build drones capable of carrying up to say 5kG. Therefore we need four 3 phase BLDC inverters capableof 250W each.We must build the inverters ourselves, and not import them in from outside Europe/UK/USA/Australia.There are very few companys in EU/UK/USA/Australia that build drone inverters, so we need to do this ourselves.Please offer us any help you can?The inverter bit looks simple....just a bridge of four suitably heatsunk MOSFETs. [EDIT...Six as kindly pointed out below...ENDofEDIT]Do you know of inverter control chips for this, or chipsets?What battery voltage would be best would you think? (we believe 48V is best, with matched series/parallel cells and "stop_when_any_is_full_or_empty"charging regime.)they will have 4 propellers, so we need four 250W inverters.So thats 6 Amps from each battery.Do you think a microcotnroller would be best to provide the Inverter MOSFETs gate drivesignals?So we need it to receive the four rotor position sensors, and then push out the drive signals, and have the four speed inputs from the Autopilot.Please help with this?

author: dmills
author_rank: Super Contributor
timestamp: February 28, 2024, 04:39:06 pm
content: 6 mosfets per motor surely? They are three phase machines.Usual approach is gong to be a micro running the whole thing, possibly one of the various dual core offerings so you can have the small core doing the really hard realtime motor control stuff and the bigger one handling flight dynamics and related functions. Have a poke around the ST STM stuff IIRC they do some micros that have the numerous timers that are useful for producing gate drive signals for such things and I think there is example code for field oriented control out there in an app note, including code for sensorless operation which seems sane in this case (You don't likely need very low speed control, so why bother with the sensors?), some of the micros have ADCs and comparators useful for the motor drive stuff on chip.Likely you can find a modest integrated three phase bridge and gate driver as a packaged part, maybe with integrated low side current sense, which will save significant area if you can find a suitable part, I would be eyeballing Infineon's offerings, maybe also TI.There are standalone motor controller chips, but you are going to have a micro anyway, might as well save on 4 chips and just do it in software.48V is good, but it is going to be a question of what fets best suit your purposes, also what works for battery form factor, these is sometimes something to be said for designing to use standard power tool batteries!Don't forget you need to keep the hash out of the radio & gps subsytems as well as anything like analogue video links, so EMC is a first class consideration in design, as annoyingly is weight which directly comes of your cargo capacity and duration.On that subject, bigger props are almost by definition better then smaller ones (As long as the tips stay subsonic!) simply because momentum is mv, but energy is mv^2, more air slower is less energy cost then less air faster.It is a nice little toy project, and can grow to arbitrarily complex as it grows sensors, failsafes and extra telemetry, should be fun.There is plenty of open source work in this space, and I am sure you will find both BLDC drive and full up drone hardware and software on github, none of this is magic.

author: Bud
author_rank: Super Contributor
timestamp: February 28, 2024, 05:08:09 pm
content: In your other post you said "we Can" build the entire drone. In this post you saying "we Wish" to build a drone. I feel this is one of the "I am building a gizmo X but have no idea where to start" type of post.

author: langwadt
author_rank: Super Contributor
timestamp: February 28, 2024, 05:17:11 pm
content: Quote from: Bud on February 28, 2024, 05:08:09 pmas usual ... and probably made up as an excuse to complain about Chinese electronics

author: jonpaul
author_rank: Super Contributor
timestamp: February 28, 2024, 05:44:07 pm
content: FTTS: usual clickbait postdrone motor inverters are easily found at RC plane or drone partsV in 12/24/48Vfrom China or Japanj

author: Andy Chee
author_rank: Super Contributor
timestamp: February 28, 2024, 06:29:11 pm
content: Quote from: Faringdon on February 28, 2024, 03:09:36 pmTry this:https://github.com/bluerobotics/BlueESC

author: Faringdon
author_rank: Super Contributor
timestamp: February 28, 2024, 06:46:53 pm
content: Thanks, this gives it for a Arduino based drone...https://www.hackster.io/akarsh98/diy-arduino-based-quadcopter-drone-948153It seems that we can make our own three phase inverters and just connect up to them from the ESC...the ESC seems to justtake in the rotor position, and the speed demand from the flight controller, and then pushes out the correct PWMs to the inverter's FETs.We will of course be making our own Three phase inverters.

author: Siwastaja
author_rank: Super Contributor
timestamp: February 28, 2024, 06:47:15 pm
content: Internets is full of example projects and open source implementations of small drone BLDC ESCs.You want to use a small & cheap microcontroller which still offers 3-phase PWM generation with pulse-by-pulse current limiting in hardware. For example Advanced Control Timer present in, AFAIK, every STM32 microcontroller including the smallest and cheapest F030.Sensorless commutation requires a few extra passives and some extra effort in code compared to hall-sensored FOC, but still, web's full of examples. You only need to dedicate some of your time to learning.

author: Siwastaja
author_rank: Super Contributor
timestamp: February 28, 2024, 06:48:26 pm
content: Quote from: Faringdon on February 28, 2024, 06:46:53 pmYou realize this is just a tutorial to use an existing product, nothing is designed here.

author: Faringdon
author_rank: Super Contributor
timestamp: February 28, 2024, 08:27:13 pm
content: Thanks...Thanks, this video ("build a drone with Arduino") appears to be whats wanted.......the idea is to build it like this...but replace the so-called "ESC" with our own 3 phase inverter.Part 6 shows the inverter.

author: tszaboo
author_rank: Super Contributor
timestamp: February 28, 2024, 08:29:44 pm
content: And? Do you want us to design it again for you?

author: Faringdon
author_rank: Super Contributor
timestamp: February 28, 2024, 08:40:16 pm
content: Thanks...it looks like pretty much all the design is done in the vids of post just above your own.We just need to replace the Inverter with our own....should be easy...then from that point, we can learn how to do the programming aspect of controlling the BLDC inverter from thepitch and yaw and speed demand values that the flight controller kicks out to us. (ie ultimately we will make our own flight controller)We also need to be able to scale up to drones of a higher power level......presumably thats easy, as the flight controller always first gets connected to the motor and "calibrates" to its characteristics....so it looks like the flight controller will adapt to a drone of any power level.The code for the flight controller all appears to be dished out to us from the arduino web site. (or the video shown).So , quite literally, all software is written in the Arduino video, and all that needs to be done, is shovel in our own motors and inverters...the Flight controller will give us the gate drive signals for the inverter FETs...and we simply need to manipulate them to drive the actual FETs via suitable gate drivers.Would you agree?

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 28, 2024, 11:43:25 pm
content: TI makes microcontrollers design for motor control. They have dual core units also.

author: Faringdon
author_rank: Super Contributor
timestamp: February 29, 2024, 09:23:27 am
content: QuoteThanks, but our funding says we must make it ourselves, as the manufacturing industry of UK/EU/USA/Japan/Aus needs to get bigger...(for obvious reasons with the current ongoings)

author: langwadt
author_rank: Super Contributor
timestamp: February 29, 2024, 11:03:01 am
content: Quote from: Faringdon on February 29, 2024, 09:23:27 amsince you had to ask and failed something as simple as use google to find any of the numerous opensource BLDC and flight controllers, you should probably return your funding and tell them that something that "complicated" is far beyond your capabilities

author: Andy Chee
author_rank: Super Contributor
timestamp: February 29, 2024, 11:29:53 am
content: Quote from: Faringdon on February 29, 2024, 09:23:27 amUnless you can make your motor controllers cheap, the average consumer won't be interested, and you'll never recoup your development costs.Despite this forum being predominantly an engineering discussion forum, one can get target fixated on singular details and ignore the bigger picture, which in large companies can be delegated to the marketing & finance departments, but as a solo outfit you will have to take on these jobs yourself in addition to engineering design & manufacturing.

author: gnif
author_rank: Unknown
timestamp: March 01, 2024, 09:01:19 am
content: Thread locked.See:https://www.eevblog.com/forum/work-wanted/wish-to-setup-a-workshop-building-drones/msg5365376/