Method for estimating the electromagnetic torque of a synchronous electric machine

A method for estimating an electromagnetic torque of a permanent-magnet three-phase synchronous electric machine for an electric or hybrid motor vehicle, the method comprising:

• measuring currents and voltages on phases of a stator of the machine in a fixed three-phase reference system tied to the stator;
• determining the currents and voltages in a fixed two-phase reference system tied to the stator as a function of the current and voltage measurements in the three-phase reference system;
• calculating a first estimate of a flux of the machine by calculating an integral of an electromotive force, the electromotive force being calculated based on the voltages and currents expressed in the fixed two-phase reference system tied to the stator;
• estimating the electromagnetic torque based on the flux estimated by the first estimate;
• determining the currents and voltages in a rotating two-phase reference system tied to a rotor as a function of the currents and voltages expressed in the fixed two-phase reference system and a position of the rotor with respect to the stator;
• calculating, in parallel, a second estimate of the flux of the machine using the currents expressed in the rotating two-phase reference system tied to the rotor, said second flux estimate being corrected by introducing variables characterizing magnetic uncertainties of the machine, said variables being determined by an observer based on the stator currents and voltages expressed in the rotating two-phase reference system tied to the rotor;
• comparing the torque estimated based on the flux estimated by the first estimate and a setpoint torque;
• and
• resetting initial conditions of the flux in line with the first estimate based on the flux estimated by the second estimate when a difference between the torque estimated based on the flux estimated by the first estimate and the setpoint torque exceeds a predefined threshold, wherein
• the method further comprises compensating for an offset of the calculated electromotive force before it is used in said first flux estimate.

A device for estimating an electromagnetic torque of a permanent-magnet three-phase synchronous electric machine for an electric or hybrid motor vehicle, said device being configured to receive currents and voltages measured on phases of a stator of the machine in a fixed three-phase reference system tied to the stator, transformed into a fixed two-phase reference system tied to the stator, said device comprising:

• a first flux estimator configured to estimate the flux of the machine in the fixed two-phase reference system tied to the stator, comprising two electromotive force integrators for estimating the respective components of the flux along the two direct and quadrature axes of the fixed two-phase reference system tied to the stator, said electromotive force being calculated based on the currents and voltages applied to each axis of the fixed two-phase reference system tied to the stator,
• a torque estimator configured to estimate the torque of the machine based on said respective components of the flux estimated in the two axes of the fixed two-phase reference system tied to the stator,
• a second flux estimator configured to receive the currents and voltages expressed in the fixed two-phase reference system, transformed into a rotating two-phase reference system tied to a rotor as a function of a position of the rotor with respect to the stator, said second flux estimator being configured to estimate the flux using the currents expressed in the rotating two-phase reference system tied to the rotor, said second estimator comprising an observer based on the stator currents and voltages expressed in the rotating two-phase reference system tied to the rotor, configured to determine variables characterizing magnetic uncertainties of the machine, said variables being used to correct the flux estimate of said second estimator, and
• a detector configured to compare the torque estimated by the torque estimator based on said respective components of the flux estimated in the two axes of the fixed two-phase reference system tied to the stator with a setpoint torque and to generate a signal configured to command resetting of initial conditions of the flux of the two integrators of said first flux estimator, when a difference between the estimated torque and the setpoint torque is greater than a predefined threshold, said initial conditions being reset based on the flux estimate supplied by the second flux estimator, wherein
• the signal is configured to deactivate the calculation of said second flux estimate by the second flux estimator when the difference between the estimated torque and the setpoint torque is less than or equal to said threshold.