True FOC: definition and examples

New thread cross reference

https://endless-sphere.com/forums/viewtopic.php?t=116387
 
I don’t recall seeing it mentioned on this thread, so I’ll offer it up here. One of the best resources I found when first researching FOC was a master’s thesis written by James Mevey at Kansas State University. You can find it here:

https://krex.k-state.edu/dspace/bitstream/handle/2097/1507/JamesMevey2009.pdf
 
Nice!

Came across this SimpleFOC project from the RC / robotics world, might be educational.

https://hackaday.com/2021/07/07/simplefoc-demystifies-precision-bldc-motor-control

Their definition of FOC:

Using a microprocessor to control the stator winding current in such a way that it always applies torque to the rotor. The processor continuously measures both motor current (think: shunt resistor) and rotor position (think: encoder), and the algorithm includes bits of linear algebra, motor physics, and control theory.

Question: does FOC only apply to BLDC motors??
 
john61ct said:
Nice!

Came across this SimpleFOC project from the RC / robotics world, might be educational.

https://hackaday.com/2021/07/07/simplefoc-demystifies-precision-bldc-motor-control

Their definition of FOC:

Using a microprocessor to control the stator winding current in such a way that it always applies torque to the rotor. The processor continuously measures both motor current (think: shunt resistor) and rotor position (think: encoder), and the algorithm includes bits of linear algebra, motor physics, and control theory.

Question: does FOC only apply to BLDC motors??
Click to expand...
SimpleFOC is very simple, not great performance for our vehicles last time I looked. Great for making cute robots etc.

It is true FOC.

The definition they give is not really useful for understanding FOC in any way. That description could be applied to BLDC six step, trapezoidal, V/F...

FOC applies to any motor with a rotor field and multiple sets of windings. Could be BLDC, PMSM, IPM, SESM, stepper, (whether 2 phase, 5 phase... whatever...) Induction, even reluctance motors.
 
Great, thanks for the clarifications.

mxlemming said:
FOC applies to any motor with a rotor field and multiple sets of windings.
Click to expand...
Could you clarify "multiple sets"?

No motor just uses one single thick wire right?

Also, what does V/F stand for?

 
V/F is an abbreviation for Voltage/Frequency. It's a scaler (as opposed to vector) control method for AC motors, particularly induction motors. Also known as V/Hz. Its goal is to maintain a constant magnetic flux in the motor.
 
john61ct said:
Their definition of FOC:
Click to expand...
Not a great definition. It does not require a processor; you can do it with analog circuitry if you really want to.

I think a better definition involves knowing where both fields are at any given time in the motor, and driving the motor windings to ensure a desired angular relationship between the two fields (stator and rotor.)
Question: does FOC only apply to BLDC motors??
Click to expand...
Not at all. It applies to any motor where you can control the phase angle of at least one set of coils. BLDC, induction, SR, even stepper can be driven via FOC.
 
https://endless-sphere.com/forums/viewtopic.php?p=1715807#p1715807

Thread is mxlemming's "New ground-up ESC
- MESC_FOC_ESC"

with a great new contribution from liminalsunset

https://endless-sphere.com/forums/viewtopic.php?p=1715805#p1715805
 
hi

Is there a foc fw-hardware that accelerates from 0 rpm by providing full torque full power? is there an "FOC" with a hardstarts?
 
Q is way above my paygrade

but my understanding is no, the principle requires motion underway before the algorithm starts working.

Of course another control method could be used until reaching a certain rpm / mph then FOC takes over.

Those more clueful please correct me if that is wrong.
 
There's a few different large-capability VESC design variations here on ES you might look at; I'm sure at least one of them could do it.

Lebowski's brain board has been used for controllers on drag racing cars so I suspect it can do it too. Arlo1 has some threads about that.
 
mehmetoz1980 said:
hi

Is there a foc fw-hardware that accelerates from 0 rpm by providing full torque full power? is there an "FOC" with a hardstarts?
Click to expand...



Yes. It requires having a good map of the motors inductance differences depending on the rotor position magnetic influences and a controller with fast current measurement and processing.

Its not a technology problem or a physics problem, but it is a tuning and setup challenge for a DIY'er to get things refined beyond auto-tune levels for maximum 0rpm torque and response sensorless.
 
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