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Electric Car Brushless Drive

Evan Schillling
Other Parts Discussed in Thread: DRV8312, DRV8301, DRV8302, DRV8332, DRV8313, MOTORWARE, CONTROLSUITE

Hello,

I'm a student at the Milwaukee School of Engineering working on an electric car project to compete in the Shell Ecomarathon. This is my teams first attempt at a fully electric vehicle, and the competition requires us to design and build our own motor controller.

Initially I've been looking at a brushless motor controller such as the DRV8312. Would we be able to purchase a DRV8312, attach it to a power stage composed of appropriately-rated transistors, and hook this up to a ~1hp motor to control it? How complicated would this process be? We have the capability to lay out a custom pcb design in Eagle and get it printed.

Any other information, tutorials, or resources that anyone could recommend on this subject would be very helpful!

Thanks in advance,

Evan

  • 0
    TI__Mastermind 21320 points

    Hi Evan,

    Sounds like quite the project. The DRV8312 is actually an integrated driver and already has the power FETs located internally.

    Sound sounds like you are looking for a Pre-Driver (DRV8301 or DRV8302). Are you planning on using a dedicated controller for the Motor Driver?

    What kind of motor are you trying to drive? What are the operating conditions (phase voltage, peak phase current)? 

    Once we narrow down what you are trying to do, we can try to point you in the right direction for resources.

  • 0 in reply to Nicholas Oborny
    Prodigy 90 points

    Hi Nicholas,

    I am a freshman at the Milwaukee School of Engineering working on this project with Evan.  I am just going to throw in my 2 cents on this.  Since we only need about 1hp, I suggested using a 1/8th scale hobby grade BLDC motor, such as this one: http://www.hobbypartz.com/96m801-4074-2000kv.html

    Now, as per the rules in the competition, we can't use a prebuilt motor controller, so that is why we are going through the trouble to build one from scratch.

    As for the Phase Voltage and Peak Phase current, I am not sure, Evan might be able to better answer that.

    Also, I would assume that we would indeed be using a dedicated motor controller for the Motor Driver. 

    Assuming we use a DRV830x as the starting point to base our whole controller/driver around, what would it take to build a fully functional Sensorless BLDC controller that would be able to run the motor I referred to earlier?

    Thank you for your assistance,

    Austin

  • 0 in reply to Austin Bartz
    TI__Mastermind 21320 points

    Evan and Austin,

    You can see in the motor description where it will tell you some of the motor characteristics. There are ratings for internal resistance, max voltage, and various other specs.

    You will need to determine the max current/voltage your application is going to require/utilize. This is going to determine whether you can use an integrated driver (DRV8312/DRV8332/DRV8313) or pre-driver (DRV8301/DRV8302). This can be determined through someone with prior knowledge, testing, or calculations.

    Integrated drivers have internal FETs and generally support lower power motors. Pre-drivers utilize external power FETs and generally support up to the ratings of the external FETs. The DRV8312 can support 3.5 continuous phase current in ideal conditions. But the DRV8301 EVM (DRV8301-HC-C2-KIT) can supports currents up to ~40A continuous.

    For a sensorless control board your main components are going to be a controller (C2000 is used by our EVMs), a control algorithm for commutation, a motor driver, power FETs, and a power supply.

    Sometimes high speed, high performance RC motors (as such) have issues with sensorless control schemes. Generally FOC algorithms perform better. You can look at InstaSPIN-FOC.

    For the DRV8301 it has an EVM (complete solution pre-built for evaluating our parts) DRV8301-HC-C2-KIT. You can find information on this board in controlSUITE, see link on left side, and also TI MotorWare.

    In addition, sometime early November we will be releasing a BoosterPack for the C2000 LaunchPad based upon the DRV8301 and utilized TI InstaSPIN-FOC. This will be in a lower price range than the DRV8301-HC-C2-KIT.

    I would visit these pages and start researching as this project is not a simple task. Let me know if you have any other questions.

    http://www.ti.com/lsds/ti/apps/motor/brushless_dc/overview.page

    http://www.ti.com/ww/en/mcu/instaspin/index.shtml?DCMP=c2x-instaspin&HQS=instaspin

    http://www.ti.com/tool/motorware?DCMP=c2x-instaspin&HQS=c2x-isfoc-pr-sw

    http://www.ti.com/tool/instaspin-bldc

  • 0 in reply to Nicholas Oborny
    TI__Guru** 119640 points

    Milwaukee team,

    My recommendation for a sensorless 3-ph BLDC/PMSM based car is:

    tell us voltage and current of the motor you are looking to use. probably low voltage and high current. If you are using 12V car batteries for 1hp you will ned 62A continuous.  I would look at your power source and try to get more voltage.  Using a 48V system with <20A continuous motors will be easier on you.  The lower the current, the eaiser to control the current and create hardware robust enough for the instantaneous current you will require.  Also note that for a vehicle you will want torque. You can get this through more poles in the motor construction and/or the gearing that you use.

    I also highly recommend using a TMS320F2806xF or TMS320F2702xF device to implement InstaSPIN-FOC in sensorless torque control mode (the motor controller should just control torque, the driver should control speed by regulating the torque command to the motor).  www.ti.com/instaspin-foc

    I also HIGHLY recommend that you use a single motor to create the torque and a transmission to get synchronous power to the wheels (rear or front depending on your design).  Trying to do direct drive of each wheel and synchronizing the torque control is a MAJOR system challenge that you should avoid.