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Help choosing InstaSPIN-FOC or InstaSPIN-BLDC for aircraft propulsion prototype

Vlad Blanshey
Intellectual 690 points
Other Parts Discussed in Thread: DRV8301-69M-KIT, INSTASPIN-BLDC, MOTORWARE, CCSTUDIO, INSTASPINUNIVERSALGUI, DRV8301, UCC27524, TMDSHVMTRINSPIN, TMS320F28069M, UCC27322, TMS320F28069F

Hello, I need help choosing the best evaluation kit for our electric propulsion aircraft prototype. It is not clear from reading the pages of the instaSPIN technologies if insta FOC can give any advantages compared to insta-BLDC for given specifications.

Currently we are considering to test 3 motors for the prototype. Range of parameters about similar for all of them:

  • All motors are brushless sensorless BLDC type, 2 are out-runners, 1 in-runner,
  • number of poles :  from 18 to 24
  • kV from 40 rpm/v (direct drive) to 115 rpm/v (with reduction gear)
  • max 20KW each
  • rotational speed up to 9,000RPM , this is mechanical rotational speed, electronic (waveform) speed 81,000 to 108,000 respectively according to poles
  • From 0 to 500RPM no load, from 500RPM to 9000RPM load gradually increases proportionally to the RPM of the propeller (rotational speed)
  • max estimated torque on the shaft about 40Nm
  • Working voltage 60v (for now although in the long run we want to use 85v battery).
  • Maximum burst amperage for this range of power would be up to 250A or 300Amps (based on experience with other controllers)
  • Continuous working amperage 150Amps
  • In terms of the efficient usage of in-flight battery we need the most efficient waveforms (in efficient advance with rotor's position) to get most mechanical power from least battery current
  • Proper directional motor' startup is important to match the propeller.

------------------

We are considering to start with either DRV8301-HC-C2-KIT  to try instaSPIN-BLDC method  or  DRV8301-69M-KIT to try instaSPIN-FOC solution on all motors and in the end we will add power module to replace kit's simple MOSFET's pairs as well as add SPI communication with our in-flight monitoring micro-controller. 

Which method/evaluation kit to choose? Is there more appropriate kit for this? Are they all equally good for this application? We'd prefer not to do any re-programming of the motor control but to use this part of TI solution as is. We'd only add communication with our in-flight controller. If both methods are the same we'd go with InstaBLDC method as it is easy to use .

Thanks in advance for any advice

Vlad

  • 0
    TI__Guru** 118000 points

    InstaSPIN-FOC will probably work better for the high speeds required and it will be easier to get running under dynamic loads.

    To reach these high speeds and to produce this much current though these motors will be designed like the hobby motors many are playing with...these have their own set of challenges as the short circuit current is so ridiculously high that during the switching events you don't get a nice smooth current decay where you can take a sample in the middle and consider it the average...what I'm trying to say is that low-side shunt current sampling is difficult, which makes current reconstruction and current control difficult.

    I have found InstaSPIN-BLDC to be more challenging to get started on these types of motors as the current is essentially unregulated to start and it is very easy to trip the inverter.

    your current rating is much higher than any of our kits support, so you will have to design your own hardware to do full load testing. DRV8301-69M-KIT is the closest solution. I would be very careful using the full 60V on this kit as any overvoltage situation will damage it...I like to keep the bus to 52V max.  You only get 40A peak current with the settings used in InstaSPIN-FOC.

  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Thank you very much Chris for valuable info. From the start we'd be able to test our motors with DRV8301-69M-KIT kit as is under no load spin and also with low load up to 1000rpm (under 40amps) , but later ... regarding InstaSPIN-FOC limitations...
    even after increasing the amps limits, seems I will not be able to use provided end user interface (and may be even core FOC code...) because of the amps limit to 40A ? Same probably will happen when we customize circuits to increase volts to 85v - we won't be able to use provided software as it will limit to 60v - is it so? Then we'd have to change FOC code and it's front-end GUI interface? ... Please let me know what options does TI provide to go around these limits , yet to be able to use available instaSPIN-FOC software (including GUI interface) ...
    Thanks
    Vlad
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    you must change the software variables for your HW of course. This requires updates to the HAL.c/.h, and user.h at a minimum and is discussed in the documentation.

    The INSTASPINUNIVERSALGUI instruments any MotorWare project, even if you make updates. And you can customize yourself using GUI Composer inside CCStudio.
  • 0 in reply to Vlad Blanshey
    Intellectual 690 points
    I want to re-instate my questions in more intelligent way - after using the evaluation kits please provide pointers to the TI's solutions to go beyond mentioned limitations: FOC code and front end GUI interface with higher limits of amps and volts (and rotational speed to at least 100,000+ hz) and also hardware solutions to again go beyond the same limitations : voltage DC-DC converters, parallel power MOSFETS, etc ...
    Vlad
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    the software solution can work at higher power levels, but you obviously need to tell the software about your hardware. It has to know the scaling of the system.

    100,000 Hz is not a valid speed. I assume you mean 100 KRPM. This can be achievable depending on how many poles are in the motor. There are limitations due to control law theory needing to run at least max_freq / 8 which effects MIPS usage. We've run to just over 4 KHz electrical with InstaSPIN-FOC on F28069M devices.

    TI does not have a recommended HW solution for your power level. We do have some 100V gate drivers, you would have to make your own inverter out of appropriately rated FETs (non TI).
  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Current motor speed should be up to 9000 mechanical RPM with 24 poles motor. In the future I may try available motors up to 46 poles. Will controller be a bottleneck for such speed?
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    1800 Hz ( 9 KRPM with 24 poles) is achievable. You need to run your current and estimator frequencies at 15 KHz +

    doubling this to 3600 Hz is really pushing the boundaries of a 90 MHz F28069M device as you would need to run the controllers at 30 KHz which uses up most of the available CPU cycles, leaving very little for the rest of your system code.
  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Thank you Chris. You saved me weeks or even months of experimenting to find all these what I learned from you.
    This seems to be the last question how to proceed after evaluation ... increase of power volts up to 100v and more current :
    Is it a good start to build high power controller to evaluate High Voltage Motor Kit www.ti.com/.../tmdshvmtrinspin ???
    It is not based on DRV8301 but it is already up to 100v and UCC27524 MOSFET drivers allow driving double MOSFETS...(possible limit up to 300A with 2 half bridge 150A MOSFETS per phase...). MCU code in that kit probably different for UCC27524 MOSFET drivers from 8301...
    For InstaSPIN-FOC evaluation though I'll still use DRV8301-69M-KIT as you suggest...
    Vlad
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    tmdshvmtrinspin only supports up to 10A continuous and uses a power module. It's not a good reference for your design.
    it may be useful to spin up some of your motors unloaded...but depends on the start-up current required from your motor.
  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Not for evaluation but only use that kit' schematics for development of our custom high power controller - using same mating of InstaSPIN™ TMS320F28069M MCU with high voltage UCC27524 MOSFET drivers , using the same instaSPIN-FOC software of that kit driving UCC27524 chips but only add our parallel high power MOSFETS driving up to 300A to motor coils... all those input voltage convertions from that kit obviously not needed...
    Is this good approach to build a high power controller?
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points

    as far as pin routing, sure. but the physical layout will be significantly different for a high power inverter. and typically you would use in phase current measurements (using magnetic hall effect sensors, usually from LEM).

    have you ever designed a high powered inverter?

  • 0 in reply to ChrisClearman
    Intellectual 690 points
    I never did any analog design - my experience is heavy in all aspects of developing embedded digital... I will use help from analog engineer, but I need to understand what to choose as a basis for our development to do design for safety (meant literally - this will be a propulsion of the manned aircraft, and I myself will be the test pilot! My life will depend on this controller's behavior :) .
    I know that layout surely change because all power MOSFETS must be mounted on the separate large heatsink with forced air flow... only "back end" power drives- the MOSFETS circuits to be changed I think... all back sensing needed by FOC process is there - even overcurrrent, overtemperature undervoltage protection seems already to be there ...
    Why would I need hall sensors if tmdshvmtrinspin does not use such? Or does it? FOC measurement of current probably done by InstaSPIN-FOC software process combining lower shunt's runtime voltage samples with predictive algorithm ... As I understand this is the instaSPIN process and this sampling of shunt's voltage/current is probaly the same in all the kits made for InstaSPIN... why would I need to change that?
    So in terms of choosing the closest circuit diagram to what we need - tmdshvmtrinspin circuitry is closer, is it? Using UCC27524 or similar mated with FOC MCU is what we need rather than DRV8301? The same must be true regarding embedded FOC/Motion code...
    Sincerely
    Vlad
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    "Why would I need hall sensors if tmdshvmtrinspin does not use such? Or does it? FOC measurement of current probably done by InstaSPIN-FOC software process combining lower shunt's runtime voltage samples with predictive algorithm ... As I understand this is the instaSPIN process and this sampling of shunt's voltage/current is probaly the same in all the kits made for InstaSPIN... why would I need to change that? "

    Have you looked for shunt resistors that can handle 300A burst currents? What sort of losses will you get through those? What sort of heat dissipation? Longevity?

    Typically somewhere over ~30A it starts making more sense to look at phase current measurements.
  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Oops. Is there any example by TI for high power drive with InstaSPIN? Any example of using something like UCC27322 MOSFET driver from TI which handles 9Amps to mosfet gates and also phase current measurement?
    If TI meant InstaSPIN technology for high power motors too (industrial motors go up to 1000A), there has to be example of how to...
  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    we are not allowed to resell hardware at these power levels unfortunately.

    I know there are several companies who have done projects at these power levels and may have hardware to sell. Ex:
    www.d3engineering.com/powerandmotion.html
  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Thank you very much Chris. You gave me direction to work.
    Sincerely
    Vlad
  • 0 in reply to ChrisClearman
    Intellectual 690 points

    Chris, I ordered the DRV8301-69M-KIT to learn and test InstaSPIN as per your advice, but while learning through TI site, I realized that this kit has InstaSPIN-Motion software installed in ROM, not InstaSPIN-FOC.... (69M stands for Motion). I first thought both will be there... I'd like to try both and, in fact I intended to try FOC first...

    Please let me know:  As a specific version of InstaSPIN software comes loaded in and runs in ROM , how can I run FOC with this kit as it comes?
     Also how different do you expect those two methods to be for running my application? (motor up to 9000rpm, 24 poles, 1800Hz, up to 300amps, 85v for geared down 3:1 propeller drive)

    Sincerely

    Vladimir

  • 0 in reply to Vlad Blanshey
    TI__Guru** 118000 points
    InstaSPIN-MOTION is InstaSPIN-FOC with additional features.
    In MotorWare you will use the projects 01 through 10 in the InstaSPIN_foc folders (sensorless torque or velocity)
    Then you can try the InstaSPIN_motion projects if you like (sensorless velocity, sensored velocity, sensored position)
  • 0 in reply to ChrisClearman
    Intellectual 690 points
    Thank you, I'm sorry but my confusion derived from the TMS320F28069M description which spells out only "Motion" while another chip "TMS320F28069F" mentions only FOC - whence the confusion
    Propulsion application needs only control of torque with velocity, I guess position of the rotor is irrelevant for such applications... assuming the InstaSPIN-FOC is good to start motor from any rotor position... then I am good with just those 10 InstaSPIN projects
    Thanks again