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Original question:

MCF8316A: MCF8316A

MCF8316A: Motor Startup Issue

Dan Hembree
Prodigy 140 points
Part Number: MCF8316A
Other Parts Discussed in Thread: MCT8316A

Tool/software:

I’m trying to tune my motor’s startup, and most of the time the motor’s state goes straight to CLOSED_LOOP_UNALIGNED right after startup. In this state, the motor’s acceleration is very sluggish, and often takes several seconds to switch to CLOSED_LOOP_ALIGNED. I assume CLOSED_LOOP_UNALIGNED is some undesirable fault state as a result of a bad hand-off, but the datasheet doesn’t talk about this state at all or how to prevent it. Motor driver is the MCF8316A and the motor is a 60W 16-pole 24V, 3.8A, .6Nm.

  • 0
    TI__Mastermind 24740 points

    Hi Dan,

    CLOSED_LOOP_UNALIGNED is an algorithm state where the open to closed loop handoff speed has been reached but there is still some theta error. I recommend adjusting THETA_ERROR_RAMP_RATE and  CL_SLOW_ACC to higher values to speed up the transition from CLOSED_LOOP_UNALIGNED to CLOSED_LOOP_ALIGNED. Please take a look at section 7.3.10.4.6 of the MCF8316A datasheet for more information about the handoff period and the registers involved

    If you require further support, could you provide the current register configuration you are using? 

    Regards,

    Joshua

  • 0 in reply to Joshua Horlander Cruz
    Prodigy 140 points

    Joshua,

    Thanks for your reply. I have tried adjusting these as well as many other registers in the MCF8316A without success. I stumbled upon a TI video "Starting up a BLDC motor in 50 ms" which shows a motor quite rapidly starting, presumably in 50ms, using an MCT8316A driver. Am I incorrect in assuming the MCF8316A has the potential to achieve similar start-up time?

  • 0 in reply to Dan Hembree
    TI__Mastermind 24740 points

    Hi Dan, 

    I recommend taking a look at the MCF8316A Tuning Guide, if you have not already, for guidance on the registers to adjust to get the motor spinning, which registers to adjust to address faults, and how to further optimize your motor's performance for you applications purpose.

    The MCT8316A has features not present in the MCF816A, like INTEG_ZC_METHOD, which are designed to help achieve a start up time < 100 ms. So while achieving a start up time similar to the MCT8316A with the MCF8316A is not impossible, it is not likely to be able to achieve as quick of a start up.

    Regards,

    Joshua