Estimate stator inductance (Lq) of permanent magnet synchronous motor (PMSM)
Motor Control Blockset / Parameter Estimation / PMSM Parameter Estimation
The Lq Estimator block computes the q-axis stator inductance of a PMSM using the phase currents, stator resistance, and the test configuration elements.
At first, the block locks the rotor along the d-axis by injecting a constant voltage (Vd), which is configurable using the parameter Vdq bias voltage (PU) of the PMSM Parameter Estimation Configurator block. This ensures that the rotor remains stationary (aligned with d-axis) during frequency injection. To estimate q-axis stator inductance, the block injects a high-frequency voltage signal along the q-axis and then performs the frequency sweep process by gradually reducing the injected signal frequency using the step size defined by Step for frequency sweep (Hz) parameter. During frequency sweep, the block monitors the magnitude of the motor phase current. When the current magnitude becomes appropriately high or when the injected signal frequency reaches the minimum value (Minimum frequency (Hz) parameter), the block starts the estimation process by injecting a signal with rising frequency having a step size of Frequency step size for estimation (Hz) with number of steps defined by the Number of frequencies for estimation parameter. For details about these parameters, see PMSM Parameter Estimation Configurator.
This image shows the frequency sweep and the incremental steps of rising frequency.
The Lq estimation process uses the measured frequency sweep time duration as well as the step size of the changing frequency to estimate the q-axis stator inductance, Lq.
Iabc — Three-phase current response
The three-phase current response of the motor measured by the current sensors.
Providing phase-c current input is optional. The block functionality is not impacted if you do not provide the phase-c current input.
Rs — Estimated stator resistance
Estimated stator resistance of the PMSM. You can either connect this input port to
Rs output of the PMSM Rs Estimator block or
provide the resistance value manually using a Constant block.
StartStop — Control signal for Lq estimation
Signal that either starts or stops Lq estimation:
1(rising edge of a pulse) — This signal initiates the Lq estimation.
0(falling edge of a pulse) — This signal immediately stops the Lq estimation process. If you interrupt the estimation process abruptly before completion, the block does not compute or output the Lq value.
Config — Bus signal input
This table summarizes the expected configuration elements in the bus signal input.
Elements for motor and inverter hardware
Number of pole pairs
Rated speed of motor
Rated current of motor
Maximum measurable inverter current
Current sense gain
Voltage sense gain
Parameter estimation sample time
Elements for estimating motor inductances (Ld and Lq)
Step for frequency sweep
Frequency step size for estimation
Number of frequencies for estimation
Elements for estimating back EMF constant (Ke), motor inertia (J), and friction constant (B)
Back EMF estimation time
Back EMF estimation speed
Specify current controller gains (off/on)
Iq Reference current for FOC
Lower speed limit for inertia estimation
You can connect this input port to the
Config output port of
the PMSM Parameter Estimation Configurator block.
Vabc — a, b, and c-axis stator
reference voltage components
Stator reference voltage components along the a, b, and c axes of the abc reference frame.
Lq — Estimated q-axis stator inductance
Estimated q-axis stator inductance (in Henry).
Log — Debug signals
Debug signals that the block provides for examination. The bus includes these debug signals.
Frequency of signal injected most recently
|Did not complete Lq estimation|
|Lq estimation completed successfully|
Phase difference between the injected voltage and current response
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