Identification of Permanent Magnet Synchronous Motor Parameters

For high performance motor controls applications such as electric vehicles, accurate motor parameter knowledge is required. Motor parameters like d-axis inductance, q-axis inductance, resistance and permanent magnet flux linkage are difficult to obtain and measure directly. These four parameters can be reduced to three parameters resistance, d-axis and q axis flux linkage. In this paper, a new scheme is proposed to approximate d-axis and q-axis flux linkage using measured torque, dq-axis measured current, and dq-axis voltage commands to the inverter. d-axis and q-axis flux linkages are estimated over a range of d-axis and q-axis currents that fully map the desired motor operation region. In the approach defined here, the parameter identification problem is converted to an optimization problem. dq-axis flux linkages are estimated using an optimization method that relies on the calculation of dq-axis voltages and torque estimates based on motor equations that correspond to the operation of interior permanent magnet (IPM) machines. Calculating and subsequently comparing these outputs to experimental results confirms that the expected torque errors from the optimized flux maps are minimal. The results obtained shows that parameters can be accurately estimated and used to estimate torque with good accuracy.