AMCLIB_ACIMRotFluxObsrv input parameters

[General_motor_control]

We have a three-phase induction machine (IM), of which we want to know the following motor parameters:

Rs:            stator resistance [Ohm]

Ls:             stator inductance [Henry]

Lm:           magnetizing inductance [Henry]

Rr:             rotor resistance [Ohm]

Lr:              rotor inductance [Henry]

For sensorless control of the IM, we use the AMCLIB_ACIMRotFluxObsrv and AMCLIB_ACIMSpeedMRAS. Rs and Ls are measured and verified - thus certain. However, executing the no-load and blocked-rotor test results in Lm >> Lr, Ls (magnetizing inductance greater than the product of stator- and rotor-inductance), which seems legit comparing to other papers and/or results found online. However, fltKrLsTotLeakGain from the AMCLIB_ACIMRotFluxObsrv ends up to be a negative gain in this way as the formula is:

((Lr * Ls) - Lm^2) / Lm

This seems to be faulty? Because a negative gain will not work out. What could be a possible cause? We use an MKV58 on a custom PCB. So no specif MBDT. 

[pavelrech · Accepted solution]

Hello,

I investigated the AMCLIB_ACIMRotFluxObsrv function calculations with negative fltKrLsTotLeakGain parameter. The AMCLIB_ACIMRotFluxObsrv will work as expected with negative fltKrLsTotLeakGain, it can change the sPsiRotSAlBe alpha and beta components. Even the documentation claims the fltKrLsTotLeakGain parameter shall be non-negative value from code perspective this parameter can be negative without function degradation (AMCLIB_ACIMRotFluxObsrv was tested with positive fltKrLsTotLeakGain only to cover most common ACIMs). Function AMCLIB_ACIMSpeedMRAS does not use the fltKrLsTotLeakGain.

[General_motor_control]

Hello @pavelrech ,

As a follow-up question, for the AMCLIB_ACIMRotFluxObsrv_FLT the sCtrl.PGain and sCtrl.IGain as well as for the AMCLIB_ACIMSpeedMRAS_T_FLT the sCtrl.fltPGain and sCtrl.IGain are given some arbitrary relatively large value without any description in terms of where these gains are based on. Is this arbritrary trial-and-error / manual tuning or can these be properly set?

Kind Regards,

[pavelrech]

Hello,

both functions (AMCLIB_ACIMRotFluxObsrv_FLT  and AMCLIB_ACIMSpeedMRAS_T_FLT ) have own P and I gains of the PI controllers that purpose is to make minimal the input errors. The P and I gains must be set by user before the function usage.

In case of AMCLIB_ACIMRotFluxObsrv_FLT function there are two controllers compensating the Alpha and Beta flux components between stator and rotor model estimations. The alpha and beta controllers share the P and I gains.

In case of AMCLIB_ACIMSpeedMRAS_T_FLT function there is only one PI controller for raw mechanical speed.

We do not have any motor control tuning tool for ACIM, so it is necessary to tune the application manually or by the trial-and-error. For more information about ACIM tuning here are the documentation should help you.