https://community.nxp.com/t5/Motor-Control-and-Smart-Energy/Sensorless-PMSM-Field-Oriented-Control-V2/m-p/2360424#M1373 <P>I am currently implementing sensorless control for PMSM using field-oriented control in combination with the AMCLIB_PMSMBemfObsrvDQ and the AMCLIB_TrackObsrv for the ARM Cortex M7F. I have a several kW motor with a mechanical speed sensor mounted to the shaft. I am using as a reference the DRM148 Rev.1, 02/2016.</P><P>I would like to achieve a situation where I have sensored closed-loop FOC with an observer running in parallel in the background fed with the right feedback information such that in a steady-state condition the measured (sensor) speed and the estimated observer speed converge. Referring back to Fig. 23, from the DRM148, the estimated observer speed is converging near the open-loop speed during start-up.</P><P>In the AMCLIB_PMSMBemfObsrvDQ I use the sensor speed output (converted to angular electrical rotor speed) as an input to the BEMF observer from standstill (so no open-loop startup). From 0 - 100 RPM the observer is initialized, whereas for speed &gt;100 RPM it uses feedback and the init function is not used anymore. Furthermore, the requested voltages (Udq*) and currents (Idq*) are used for the BEMF observer input(s). I convert the AMCLIB_TrackObsrv output electrical rotor speed to mechanical speed in RPM and visually compare this to the actual rotor/sensor mechanical shaft speed. This all happens in closed-loop manner (sensored). However, the AMCLIB_TrackObsrv output speed still does not converge on a long time frame (e.g. &gt;10 seconds) while keeping the rotor speed constant (e.g. 500 RPM). This is in no-load condition. When applying load to the motor shaft the estimated mechanical speed from the observer decreases rapidly.</P><P>What are possible causes for this difference in RPM between the true sensor mechanical speed and the estimated observer mechanical speed when using sensored closed-loop control?</P> Tue, 05 May 2026 10:39:34 GMT General_motor_control 2026-05-05T10:39:34Z https://community.nxp.com/t5/Motor-Control-and-Smart-Energy/Sensorless-PMSM-Field-Oriented-Control-V2/m-p/2360424#M1373 <P>I am currently implementing sensorless control for PMSM using field-oriented control in combination with the AMCLIB_PMSMBemfObsrvDQ and the AMCLIB_TrackObsrv for the ARM Cortex M7F. I have a several kW motor with a mechanical speed sensor mounted to the shaft. I am using as a reference the DRM148 Rev.1, 02/2016.</P><P>I would like to achieve a situation where I have sensored closed-loop FOC with an observer running in parallel in the background fed with the right feedback information such that in a steady-state condition the measured (sensor) speed and the estimated observer speed converge. Referring back to Fig. 23, from the DRM148, the estimated observer speed is converging near the open-loop speed during start-up.</P><P>In the AMCLIB_PMSMBemfObsrvDQ I use the sensor speed output (converted to angular electrical rotor speed) as an input to the BEMF observer from standstill (so no open-loop startup). From 0 - 100 RPM the observer is initialized, whereas for speed &gt;100 RPM it uses feedback and the init function is not used anymore. Furthermore, the requested voltages (Udq*) and currents (Idq*) are used for the BEMF observer input(s). I convert the AMCLIB_TrackObsrv output electrical rotor speed to mechanical speed in RPM and visually compare this to the actual rotor/sensor mechanical shaft speed. This all happens in closed-loop manner (sensored). However, the AMCLIB_TrackObsrv output speed still does not converge on a long time frame (e.g. &gt;10 seconds) while keeping the rotor speed constant (e.g. 500 RPM). This is in no-load condition. When applying load to the motor shaft the estimated mechanical speed from the observer decreases rapidly.</P><P>What are possible causes for this difference in RPM between the true sensor mechanical speed and the estimated observer mechanical speed when using sensored closed-loop control?</P> Tue, 05 May 2026 10:39:34 GMT https://community.nxp.com/t5/Motor-Control-and-Smart-Energy/Sensorless-PMSM-Field-Oriented-Control-V2/m-p/2360424#M1373 General_motor_control 2026-05-05T10:39:34Z