METHOD TO CONTROL AN ELECTRIC MOTOR WITH ADJUSTMENT OF THE VALUE OF THE EQUIVALENT IMPEDANCE

摘要

A method to control an electric motor including the steps of: determining a target torque; calculating a target current by dividing the target torque by a torque constant; determining an equivalent impedance by means of a predetermined map; calculating the voltage drop by multiplying the target current by the equivalent impedance; calculating a counter-electromotive force by multiplying an actual rotation speed by a speed constant; determining a control voltage to be applied to the power supply terminals of the electric motor by adding the voltage drop to the counter-electromotive force; determining an offset parameter; and correcting the equivalent impedance provided by the predetermined map by applying the offset parameter.

主权项

1. A method to control an electric motor, the control method comprising the steps of:
determining a target torque; calculating a target current by dividing the target torque by a torque constant; determining an equivalent impedance by means of a predetermined map; calculating the voltage drop by multiplying the target current by the equivalent impedance; calculating a counter-electromotive force by multiplying an actual rotation speed by a speed constant; and determining a control voltage to be applied to the power supply terminals of the electric motor by adding the voltage drop to the counter-electromotive force; wherein the auxiliary electric motor is of BLDC type and has a torque curve, namely the characteristic that correlates the torque to the rotation speed, having an initial section wherein the torque is constant as the rotation speed increases and an end section wherein the torque decreases as the rotation speed increases; the two sections of the torque curve of the auxiliary electric motor are connected to each other in an elbow where a change in slope is performed; the control method further comprising the steps of: determining an offset parameter when the electric motor is in the neighbourhood of a predetermined operating point; and correcting the equivalent impedance provided by the predetermined map by applying the offset parameter; wherein the operating point in which the offset parameter is determined is arranged at the elbow of the torque curve of the electric motor.