Understanding of Parameters in sto-pll

[Rahuld]

Hi ST,

I am trying to understand sensor less speed measurement using STO-PLL observer I did not get any idea for the parameters F1, F2, gain1 and gain2 parameters from user manual (STM32 motor control SDK user manual) and software code too. could you help me to understand how these parameters are computed by workbench by using motor parameters. this will help me lot.

Thanks,

Rahul D.

[Rahuld]

Please anyone can comment on this.

Thanks

Rahul 

[Gael A]

Hello Rahuld,

F1 and F2 gains are scaling factors to make sure all computations stay between the int32 boundaries we gave them. Their value simply influence the granularity of the computations. As a matter of fact, they should be as low as possible while still high enough to allow the maximum values of current / voltage / BEMF to be computed. To reduce the computations' MIPS usage, they are always set to a power of 2.

They are used to compute Gain1 and Gain2 that are specified in the Speed & position feedback sensorless algorithms section of the User Manual.

[Rahuld]

Hi @Gael A ,

Thanks for the reply.

I have set RS = 4.1ohm, LS = 0.01H and Back-emf constant is 5.6 workbench generates

F1 = 16384 and F2 = 64 

Next if I just change RS to 2500ohm workbench generates

F1 = 2048 and F2 = 16

I don't understand any formula for them.

And For Gain1 and Gain2 also I need to change formula of k1 and k2 which was given in user manual. Sometimes addition gives correct result, and sometime subtraction gives correct result. don't understand when to subtract and when to add. 

Thanks,

Rahul