A permanent magnet synchronous machine (PMSM) includes a stator and rotor powered by an inverter. A device to control the PMSM includes a sensor to sample a measurement θm of the position of the rotor, a control unit to control an operating point of the PMSM according to the position of the rotor and settings, and an estimation unit to determine an estimate {circumflex over (θ)} of the rotor position. The device also includes a malfunction detector to detect a malfunction of the sensor and a switch to connect the control unit to the sensor so that the control unit receives the measured position θm of the rotor while the malfunction detector does not indicate any sensor malfunction, and otherwise to connect the control unit to the estimation unit so that the control unit receives the estimated position {circumflex over (θ)} of the rotor when the malfunction detector indicates a sensor malfunction.