Low speed control algorithms with sensors

[geneM]

Hi - What is the best algorithm for a very low speed and low current application, <50 RPM and <1 Amp with a high resolution encoder (~4096 counts per revolution) on a 3 phase brushless motor? Do the HSO or ZEST algorithms provide any advantage over the standard FOC algorithm when running with an encoder like this? I'm assuming the FOC algorithm is better than the 6 step algorithm, is that correct? Are there any other tips for this application?

Thanks

[STuser2]

Yes FOC is better than 6 step algorithm. 

[federico.rodighiero87]

low speed control can be difficult in some way but it depends how precise do you need to be on speed control. What is the requirement ?

[geneM]

We're trying to get a 200:1 range of speed control. For example, the maximum speed of the motor may be 4000 RPM in which case the minimum speed will be 20 RPM.  The accuracy can be something like +/-5% although +/-10% may work. Velocity ripple should also be on the order of +/-5%.

Thanks for your interest.  I'll be happy to provide more details.

@GMA - I'm hoping you might be able to address my question of whether the ZeST or HSO algorithms provide any benefit in a low speed application with sensors.

[federico.rodighiero87]

do you have a plot of the low speed issue ?

[geneM]

We're just in the system design stage now.  I'm trying to figure out if we need to start with an eval board that supports ZeST or HSO or both like the ZeST discovery board.

[GMA]

Hello @geneM,

If a motor includes an encoder sensor, it is most effective to use the encoder for motor control.
HSO and STO-PLL algorithms are sensorless algorithms.

As motioned here, The STM32 ZeST algorithm is available for selected users only.

[geneM]

Hello @GMA 

Thanks for the quick response.  Just out of curiosity, how does ST select users for ZeST?  Also out of curiosity, will the ZeST algorithm provide any benefit for low speed control for a motor with an encoder?

Thanks

Gene Massion

[GMA]

Hello @geneM,

Refer to STM32 ZeST and HSO solutions page.