Why the detected motor parameters of ST Motor Profile in two boards are different?

[DF_MC]

Hello Everybody,

Here are the software and boards in this case:

1. MC workbench 6.3.2
2. NUCLEO-F401RE/X-NUCLEO-IHM08M1
3.?B-G431B-ESC1

I have an I-PMSM motor, and I use two boards (one is?NUCLEO-F401RE/X-NUCLEO-IHM08M1, and the other is?B-G431B-ESC1) to run the?ST Motor Profile for detecting the motor parameters. However, the motor parameters in the two test results differ significantly. For example, the result from Board 1 (NUCLEO-F401RE/X-NUCLEO-IHM08M1) is shown in picture 1, and the result from Board 2 (B-G431B-ESC1) is shown in picture 2. We can see that the motor phase resistance is 0.23 ohms, the phase inductance is 0.62 mH, and the back EMF constant is 9.32 in picture 1. And we can see that the motor phase resistance is 0.16 ohms, the phase inductance is 0.43 mH, and the back EMF constant is 10.42 in picture 2.

Which result should I trust? Thanks!

[STuser2]

Just for my understanding each board gives the same value every time? i tried to run profiler for one of my motor but was not successful, So, getting another relatively small motor run the profiler and see if it succeeds.

[GMA · Accepted solution]

Hello @DF_MC,

The goal of the motor profiler is to estimate the characteristics of an unknown motor to enable its use on the MCSDK workbench.
Are you able to spin the motor using the profiler results and the associated boards?
You can also refine the results by editing the motor.json generated file with RLC meter measurement result.
Chapters 3 and 4 in n How To manually configure the motor parameters also present a method to compute some parameters.

[DF_MC]

Hello, yes, each board gives almost the same value every time, and I can spin the motor using both the profiler results and the associated boards. However, when using the motor parameters obtained from the  B-G431B-ESC1 board to run the sensorless example routine, the torque output is weak at low speeds. If you grab the rotor by hand, it will return a "speed feedback error".

[DF_MC]

Hello @GMA , 

Thank you for your guidance. I can spin the motor using both the profiler results and the associated boards. However, when using the motor parameters obtained from the  B-G431B-ESC1 board to run the sensorless example routine, the torque output is weak at low speeds. If I grab the rotor by hand, it will return a "speed feedback error".

[GMA]

Hello @DF_MC,

Does motor profiling result with NUCLEO-F401RE/X-NUCLEO-IHM08M1 provide better results on the B-G431B-ESC1 board?
Descriptions and management of FOC errors are available in the documentation accessible through Workbench tool > About > Documentations > Documentation > User manual tab, FOC Firmware errors link.

[DF_MC]

Hello @GMA ,

Thanks for your reply. In my case, it looks like the motor profiling result with NUCLEO-F401RE/X-NUCLEO-IHM08M1 provides better results on the B-G431B-ESC1 board. 

To clarify, are you suggesting I should manually configure the motor parameters?

If I am unable to obtain precise parameters for my specific motor, could you please confirm a few points?

1. When using Hall effect speed sensors, is the back EMF constant less critical for basic operation?

2. Do the phase resistance and phase inductance primarily serve to provide the recommended starting values for the PI controller gains?

3. If the motor can spin, is the primary next step to manually tune the P and I values of the controller to achieve satisfactory performance?

Thank you for your help.