Hall sensors with even just a first order speed estimator will offer better performance. The whole HFI thing is for when you either don’t have any sensors or your sensor connection is unreliable. I am just highly skeptical of Trampa’s claims. While it is impressive it can spin a motor at low and zero speed, I question whether this is either efficient or worth the additional software overhead with high inertia loads.
Just want to reiterate what I found here. My Haggy (maytech) 6374 has a phase resistance of 19.25mOhm.
The VESC 6 mk3 I purchased from TRAMPA reports a phase resistance of 15.88mOhm.
The Flipsky 6.6 ESC reports a phase resistance of 21.7mOhm.
My own power stage reports something between 18-19.8mOhm depending on which samples I average.
This estimate is definitely within margin from what I feel, will to try to do some more tests to pinpoint where the transition occurs, finding a hill, setting the current to be just enough to climb it and progressively lowering the speed
Hall sensors will give trapezoidal control performance. A first order estimator at low speeds will bring it pretty close to FOC, that’s pretty hard to beat with any sensorless algorithm, regardless of which it is. Hall sensors have hysteresis lag that make them impractical for use at higher speeds, but have little effect at low and very low speeds.
I have shown that the inductance measurement taken by the VESC is not accurate (RCL meter, Fluke brand, at school gives more than double the estimate, my power stage gives more than triple the estimate) so I have a difficult time believing it will beat sensors.
This is of course assuming a perfect hall sensor connection, if the connection is unreliable, then hall sensor performance will be questionable.
I feel like an unwilling beta tester here. The vesc bluetooth tool basically forced me to upgrade. My profiles stopped functioning and it was telling me I had a limited connection, so I ran the firmware upgrade. Kicking myself now. Is there an easy way to roll back to 3.64 firmware?
If you took the time to actually examine the changes you’d note that this new algorithm is also now used for the inductance measurements because it’s more consistent than the previous measurement. However the accuracy isn’t even relevant to how the algorithm works because its based on the phase of the signal not the amplitude.
I’m still not sure why you are talking like you understand exactly how this is working when you haven’t taken the time to get informed.
I’d also say that claiming one inductance measurement is right and another is wrong is naive. The inductance is a linear parameter estimated from a non-linear system. Measured correctly at different amplitudes and frequencies will yield quite different values, all of which might be accurate locally.
I just can’t understand the blind bias. I’m not even claiming what we did is amazing but at least take a look at it? It’s actually a really cool method.
The RCL meter tests at 1kHz at low amplitude, my power stage tested at 30kHz at 10A.
Unless there was something that changed, the VESC measures at 7kHz.
With a default switching switching frequency of 25kHz, I find it very difficult to believe the inductance can vary by that much between two close frequencies.
Most magnetic materials/inductors do not exhibit a behavior where it peaks at a low and high frequency, then suddenly drops low at an intermediate frequency. It may peak at an intermediate frequency.
These new saliency measurements show that on many motors the inductance can vary by as much as about 30% depending on rotor position alone. There’s also the nonlinear B-H curve of iron to consider where the permeability varies depending on magnetic field, so it just depends on how you want to measure.
Yeah Vedder had a really good concept around how he wanted to structure the whole algorithm but I think through our conversations we ended up with some really cool new ideas on how to extract and process the signal we wanted.
My measurements took that into account, I rotated the motor slowly with the RCL meter, the lowest inductance it ever reported was still over 50% higher than what the TRAMPA VESC measured on the newest 4.0 firmware. The RCL meter measures with low currents, I measured with high currents, so this was also at significantly different magnetization points of the material.
RCL meter reported line to line as low as 38uH and as high as 60uH throughout one electrical revolution, I calculated line-to-line inductance using two different measurement methods and both gave ~75uH line to line using center-aligned PWM.
Since the motor will be driven with center-aligned PWM at 30khz, it makes sense to measure the inductance using 30khz center-aligned PWM.
And there’s still the erroneous resistance measurement…
The code is open source, contribute some cool new calibration routines to improve them if they aren’t performing to your standards. I’m sure everyone would be stoked.
