Setting up FOC for a small BLDC-motor with hall sensors

[fortunat]

Posted on June 18, 2012 at 13:30

Hi

I am trying to setup the ST FOC library with a small BLDC-motor with hall sensors. I am using the evaluation board STEVAL-IFN003V1. I have configured all parameters of the system with the ST Motor Control Workbench and I am able to communicate with the system trough the panel Monitor of the

Motor Control Workbench.

I have connected the windings and hall sensors according the procedure described in chaptre ''5.2.3. Setting up the system when using hall-effect sensors'' of the User manual UM1052.

When I press the button Start Motor on the MC Workbench then the motor makes a little hitch ( one to two revolution ) and the the system goes into the state Speed feedback fault. This state can be reset by pressing the button Fault Ack. 

I experimented with different values for HALL_PHASE_SHIFT without any success.

Does any body have an idea, why I am always getting this Speed feedback fault ?

Regards

Fortunat

[Gigi]

Posted on June 18, 2012 at 14:51

Ciao Fortunat

My feeling is that there is some noise glitches on the signals coming from the hall sensors.

The Speed feedback in case of Hall sensor can be asserted if the expecetd sequence of edges coming from hall sensor signal is not respected. Noise glitches can generate this kind of behaviour.

So you can act on two points

1) Increase the hall sensor digital filter (You can do this using the motor control workbench Drive Management -> Speed Position Feedback Management -> Main sensor -> Input capture filter duration ).

2) Increase the capacitor filter on the hall sensor input. It should be the C5, C6, C7. The default is 10pF but you can try with bigger values in order to filter the noises.

Ciao

Gigi

[fortunat]

Posted on June 18, 2012 at 18:14

Ciao Gigi

Thank you for your response

I have added some RC filtering at the hall signals. No the motor is running. But the speed controller is regulating in the wrong direction. If I set positive speed +2000 rpm then the motor runs very fast in the negative direction. Speed indicator on workbench shows more than -8000 rpm.

I have to recheck the phasing of the encoder signals.

Regards Fortunat

[fortunat]

Posted on June 19, 2012 at 12:06

Ciao Gigi

I am still not able to have a closed loop regulated speed control of my motor.

If I turn manually my motor in the previously defined (at the connection of the hall sensors) positive direction, then the Variable 0x1E Speed measured is indicated on the ST MC Worbench as a value with positive sign. It seems that the speed measurement works.

The reference value for the speed regulator is +5000 rpm. If I start the motor pressing the button Start Motor then it accelerates very rapidly to more than -20000 rpm. It actually runs in the wrong direction.

I wanted to view the output of the speed regulator Te* reffering to Figure 5 Speed control loop in the UM1052. Which variable in the MC Workbench is this Te* ?

It would be nice, if you could me some advice trouble shooting my problem

By the way how can I set up the Plotting window of the MC Workbench for different variables ?

Regards

Fortunat

[Gigi]

Posted on June 19, 2012 at 12:34

Ciao Fortunat,

it seems that the positive direction of the firmware (take care I don't say positive direction measured from the sensors that seems good but the one provided in output by the inverter) corrisponds to a negative direction of the motor.

What I shoud try in this case is to switch the connection of two motor phases (for instance A with B). In this way I synchronize the positive direction of the firmware with the requested direction of the motor.

Then I redo the synchronization of the hall sensor signals like explained in the manual. It must be updated becuse the two motor phase switch.

The Iq reference (in case of surface mounted motor) is proportional to the Te*.

Up to now the plotting windows variable can't be changed.

Ciao

Gigi

[fortunat]

Posted on June 19, 2012 at 14:52

Ciao Gigi

Thank you !

I have changed two phases from my motors and set up the encoder connections accordingly. Now the speed control loop is working very well.

I make these experiments just to get familar with the MC library. Actually I have to operate a Faulhaber LM 0830 040-01 linear motor with analog hall sensors. For this application I have to change the processing routines for the hall encoder of the MC library. Therefore I need the confidential version of the MC library.

I have requested the confidential version trough our local ST distributor EBV Elektronik here in Switzerland. I hope to get this confidential version soon.

Are there any plans at ST Microelectronics to add support for analog hall encoder ?

Kind regards

Fortunat

[Gigi]

Posted on June 19, 2012 at 15:02

Unfortunately not for the moment. Our ''wish list'' is overflowed ;)

I'm happy that my suggestion has been useful.

Ciao

Gigi