Automated parameter identification of fractional horse power permanent magnet synchronous motors

This paper introduces an offline parameter identification procedure for fractional horse power permanent magnet synchronous motors for model based controller design or as an end of line test of the motor. Especially for estimating the stator resistance and the inductances in the dq-frame a new approach is presented. In order to avoid an increase of measurement noise using numerical derivatives of measured signals, this approach uses the solved voltage differential equations in the dq-frame at rotor standstill. The obtained solution of this first order system is nonlinear with respect to the parameters and leads to a nonlinear optimisation problem when minimizing the quadratic error between the system equations and the measured current responses. In this paper the Levenberg-Marquardt (LM) algorithm is used for solving the optimisation problem and for estimating stator resistance and inductances. Afterwards the flux constant is estimated by calculating the induced voltage at constant speed. The rotor inertia is calculated by a torque excitation of the motor and the resulting speed response. Calculating the complex Fourier coefficient of the transfer function at the excited frequency, the rotor inertia is estimated from this value, presuming a rigid single degree of freedom system. The whole measurement procedure is developed and simulated in Simulink Stateflow and implemented to a 32-bit microcontroller at a test bench. The results of the simulation and at the test bench are presented in this paper.