Motor Control and Smart Energy中的主题 Re: KEA128BLDCRD Sensor-less BLDC

KEA128BLDCRD Sensor-less BLDC

CJH — Mon, 15 Aug 2016 13:14:57 GMT

I have the KEA128BLDCRD demo board. No problems getting it up and running with the included motor.

I am trying to drive a custom sensor-less BLDC motor - 3 phase, 10 magnetic poles. I cannot get it to start reliably. Regardless of how I set the various parameters in the Freemaster app, the best I have been able to do is to get it to start one time in 5 or so. If I push-start the motor, it runs fine, but I can't get it through the open-loop start-up process. More often than not, it runs in the opposite direction slowly until a stall error is generated.

(The motor runs fine on a Turnigy PLUSH-80A controller.)

How do I determine the various parameters to get it to start reliably? I have been through the "Sensorless BLDC Control on Kinetis KV" app note (AN5263), the only one I could find with any details on how to tune the system, but the only instructions I find there are in the flow chart:

"Motor starts and smoothly switches to closed loop: False

Sensorless tab:

- Tune Integ thr corr constant

- click update"

I need a little more help than that...

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Tue, 23 Aug 2016 12:26:36 GMT

Hi Carlos,

Ok so let's have a discussion about this issue.

At first, it would be nice to have more information regarding your BLDC motor. Do you have any kind of motor documentation (label)?

Number of poles ii first important information.

We have already first i,portant information

First important information - number of poles we already have. But to better understand your issue, these parameters are also needed :

1) What is nominal speed

2) What is

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Tue, 23 Aug 2016 13:12:40 GMT

Hi Marek,

Unfortunately, it's a custom made motor, so I don't have any documentation or label information. However, it has 10 poles and runs at 8000 rpm.

Your second question got cut off...

Thanks,
Carlos

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Tue, 23 Aug 2016 13:18:17 GMT

Actually, it does have a hand-made label:

9-10/.450/8-22-S.

I'm told these items mean:

9 rotor spokes

10 magnetic poles

8 turns of 22 gauge wire

Star termination

That's pretty much all the information I have about it.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Tue, 23 Aug 2016 14:05:05 GMT

And the 0.450 is the stack height of the stator in inches.

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Tue, 23 Aug 2016 18:16:32 GMT

Sorry for previous response I sent it by mistake. It was just a part of my message to you.

Carlos, could you send me screen shots of your setting in FreeMASTER tool?

1) Paramters tab

2) Control Loop tab

3) Sensorless tab

Thanks!

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Tue, 23 Aug 2016 18:42:07 GMT

Attached are the screen shots. Please keep in mind that the values are fairly arbitrary since I don’t know how to choose the values.

Thanks,

Carlos

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Tue, 23 Aug 2016 18:53:24 GMT

Ok, I think I know where could be a problem. Try to change parameter "pp" in Parameters tab to pp = 5.

This parameter is not number of motor poles but number of pole pairs, means that:

pp = number of poles / 2 = 10 / 2 = 5

Try to change and let me know the result.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Tue, 23 Aug 2016 19:06:07 GMT

That’s a good point. Unfortunately, I tried 5 pole pairs first, and apparently had most recently tried 10 just to see if there’s a change. (I also tried 2 and 4, for no good reason except to see if the behavior changed.)

I’ve just tried it again – changed pp to 5, hit “Update Target”, and find no detectable change in behavior. It still runs OK if I spin-start the motor, but won’t start on its own.

Just so you’re aware of it, I changed the STALLCHECK_MAX_ERRORS macro from 6 to 100 (then re-compiled and re-flashed the CPU) so that it tries to start the motor much longer before giving up and indicating a “stall”. This macro is in KEA128_appconfig.h.

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Tue, 23 Aug 2016 20:05:49 GMT

Have you already tried to increase parameter Time off from 15% to for example 30% in Sensorless Control tab?

Please after this change sent me screen shot of the appconfig.h.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Tue, 23 Aug 2016 20:21:44 GMT

Yes, I have arbitrarily change all the settings, but I really don’t understand what all of them mean or do. I just changed it from 30% to 50%, 75%, 60%, and 45%. I can’t really identify any change in behavior with any of those settings.

After all those changes, I did a “Generate Configuration File” and the resulting BLDC_appconfig.h is attached.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Wed, 24 Aug 2016 15:52:23 GMT

Any progress?

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Wed, 24 Aug 2016 16:08:45 GMT

Hi Carlos,

I was trying to find 10 pole motor here, unfortunately I could not find such a machine. It is difficult to understand what's wrong, since I cannot test your application here.

Try to spin your motor
Have you tried to spin your motor just by applying voltage and changing commutation sectors ?

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Wed, 24 Aug 2016 16:15:11 GMT

I’m not sure what you mean – apply voltage and change commutation sectors. How would I do this?

If your concern is whether the motor runs at all, it runs (and starts) fine with an off-the-shelf Turnigy PLUSH-80A controller.

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Wed, 24 Aug 2016 16:30:58 GMT

No I believe that motor is ok. But try to verify whether you are able to "step" your motor forcing commutation sectors and applying some voltage. It can be also align voltage that is in the range 1 to 2 volts. Just change sectors manually in freemaster application.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Wed, 24 Aug 2016 16:55:23 GMT

Sorry, I just don’t see where in FreeMASTER I can do that. I see where I can change the various parameters on the three tabs you asked for screen captures of, then there’s the “Output File” tab which allows me to generate a new BLDC_appconfig.h file, and the “App Control” tab, but it only has a “Start/Stop” switch and a button to “Clear Faults”. Then there are the various “Scope” screens, but they are just displays, as far as I can tell.

Do you mean through the “Variable Watch” window? I added the variable “ActualCmtSector” to the watch window, and I can change its value, but it doesn’t appear to do anything – I assume because the motor isn’t on. If I turn on the motor via the “App Control” switch, I see the ActualCmtSector values changing, but it stalls before I can actually change it and see anything.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Wed, 24 Aug 2016 17:12:11 GMT

I added several variables to the watch window, including “Start Commutation Counter”. When I reduced that to 2, it seems to be starting more often – occasionally several times in a row. Many of the times it does NOT start, it is running slowly (and noisily) in the wrong direction. (Sounding a bit like a stepper motor.) This has always been the case – where if it fails to start, it most often runs the wrong way.

I don’t know what this means, but it seems like it should be a clue.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Wed, 24 Aug 2016 20:30:12 GMT

Any thoughts or suggestions?

Re: KEA128BLDCRD Sensor-less BLDC

marekmusak — Thu, 25 Aug 2016 07:58:24 GMT

Ok Carlos we will try a simple test. Follow these steps:

1) Replace AppStart(void) function by this one:

/*******************************************************************************
*
* Function: void AppStart(void)
*
* Description: BLDC application START state function
*
*******************************************************************************/
static void AppStart(void)
{
if(driveStatus.B.AfterCMT == 1)
{
timeZC = NextCmtPeriod >> 1;

startCMTcounter--;
if(startCMTcounter > 0)
{
driveStatus.B.AfterCMT = 0;

NextCmtPeriod = MLIB_Mul(NextCmtPeriod,mcat_startCmtAcceler);
}
}

if(startCMTcounter == 0)
{
//AppStartToRun();

duty_cycle = 0;

FTM2_C1V = duty_cycle;
FTM2_C3V = duty_cycle;
FTM2_C5V = duty_cycle;
FTM2_PWMLOAD |= FTM_PWMLOAD_LDOK_MASK;
}
}

2) Replace AppAlignmentToStart(void) function by this one

/*******************************************************************************
*
* Function: void AppAlignmentToStart(void)
*
* Description: BLDC application ALIGN to START state transition function
*
*******************************************************************************/
static void AppAlignmentToStart(void)
{
driveStatus.B.Alignment = 0;
driveStatus.B.EnableCMT = 1;
driveStatus.B.AfterCMT = 0;

NextCmtSector = 0; /* Starting sector */

NextCmtPeriod = mcat_startCmtPer;
startCMTcounter = mcat_startCmtCnt - 1;

/* Prepare PWM settings for initial commutation sector */
FTM2_OUTMASK = ui8FTM2OutmaskVal[rotationDir][NextCmtSector];
FTM2_SWOCTRL = ui16FTM2SwOctrlVal[rotationDir][NextCmtSector];

FTM0_SC &= ~FTM_SC_CLKS_MASK; /* Stop FTM0 counter */
FTM0_CNT = 0x0000; /* Force commutation sector 0 PWM settings */
FTM0_MOD = STARTUP_CMT_PER;
FTM0_SC |= FTM_SC_CLKS(1); /* Start FTM0 counter */

NextCmtSector++;

/* Prepare PWM settings for the next commutation sector */
FTM2_OUTMASK = ui8FTM2OutmaskVal[rotationDir][NextCmtSector];
FTM2_SWOCTRL = ui16FTM2SwOctrlVal[rotationDir][NextCmtSector];

//NextCmtPeriod = MLIB_Mul(NextCmtPeriod,mcat_startCmtAcceler);

NextCmtPeriod = MLIB_Mul(NextCmtPeriod,1);

appState = APP_START;
}

3) Change parameter Cmt Count = 20 in FreeMASTER tool

4) Update Output File, debug your application, and push start button in FreeMASTER

5) Let me know what's going on.

Re: KEA128BLDCRD Sensor-less BLDC

CJH — Thu, 25 Aug 2016 13:06:16 GMT

OK, put that code in, compiled and flashed the CPU. When I hit the start switch, the motor jogs around a bit. I have attached an mp4 file showing two cycles. Note that I have to reset the CPU in order to re-start – once I hit the start switch and let the process go, when it stops, it becomes unresponsive, both to FreeMASTER and to the on-board switches. Reset is the only way to try again.

The clip shows two cycles – for the first one, I started recording and hit the start button immediately. Once it stopped, I hit the reset switch and then start again.

The video does not appear aliased – it faithfully re-creates the behavior of the motor.