Method for determining and/or controlling a position of an electric motor

Abstract

The invention relates to a method for determining and/or controlling a position of an electric motor, in particular in a clutch actuation system of a motor vehicle, wherein the position of a rotor of the electric motor is picked up by a sensor system situated on a stator of the electric motor outside an axis of rotation of the electric motor, and the position signal picked up by the sensor system is analyzed by an analysis unit. In a method in which the rotor position is detected with a high level of certainty, the position signal is transmitted to the analysis unit depending on a transmission distance between the sensor system and the analysis unit by means of an SPI protocol signal for short transmission distances, and/or by means of a PWM signal for longer transmission distances.

What is claimed is: 
     
       1. A method of determining and controlling a position of an electric motor in a clutch actuation system of a motor vehicle, comprising:
 arranging a stator of the electric motor outside an axis of rotation of the electric motor; 
 detecting the position of a rotor of the electric motor by a sensor system; 
 transferring a position signal from the sensor system to an analysis unit; and, analyzing the position signal from the sensor system by the analysis unit, 
 wherein when the transmission distance between the sensor system and the analysis unit is a first transmission distance, the position signal is transmitted by a serial peripheral interface protocol signal, or when the transmission distance between the sensor system and the analysis unit is a second transmission distance, the position signal is transmitted by a pulse width modulation signal; and 
 utilizing the sensor system to commutate the electric motor based upon the position signal, wherein the commutation occurs in response to utilizing serial peripheral interface protocol signal or the pulse width modulation signal, wherein the pulse width modulation signal includes information about an absolute position of a pole pair of the rotor of the electric motor and the serial peripheral interface protocol signal includes information regarding the absolute position of the rotor. 
 
     
     
       2. The method of  claim 1 , wherein the absolute position of the pole pair of the rotor of the electric motor is transmitted by the sensor system via the serial peripheral interface protocol signal or the pulse width modulation signal to the analysis unit when the electric motor is started, whereupon the electric motor is then supplied with current via a commutation derived by the analysis unit from an incremental position of the rotor of the electric motor. 
     
     
       3. The method of  claim 2 , wherein a pulse to no-pulse ratio of the pulse width modulation signal is analyzed to transmit the absolute position of a pole pair of the rotor of the electric motor. 
     
     
       4. The method of  claim 2 , wherein a comparison is carried out between an incremental position of the rotor calculated by the analysis unit and the absolute position of the pole pair. 
     
     
       5. The method of  claim 4 , wherein the comparison is carried out cyclically. 
     
     
       6. The method of  claim 1 , wherein a small-diameter magnetic transmitter ring fastened to the rotor of the electric motor which has only one pole pair is used to determine the position of the rotor. 
     
     
       7. The method of  claim 6 , wherein the magnetic transmitter ring having a larger diameter and a plurality of pole pairs, fastened to the rotor of the electric motor, is used to determine the position of the rotor, wherein the number of pole pairs of the magnetic transmitter ring is equal to the number of pole pairs of the rotor. 
     
     
       8. A clutch actuation system, comprising:
 an electric motor having a rotor and a stator, the stator arranged outside an axis of rotation; 
 a sensor system configured to detect a position of the rotor of the electric motor; and 
 an analysis unit configured to analyze a position signal from the sensor system, wherein the sensor system is configured to transmit the position signal to the analysis unit via a peripheral interface protocol in response to a transmission distance between the sensor system and the analysis unit being a first transmission distance, and to transmit the position signal via a pulse width modulation signal in response to the transmission distance between the sensor system and the analysis unit being a second transmission distance. 
 
     
     
       9. The clutch actuation system of  claim 8 , wherein the analysis unit is configured to commutate the electric motor based upon the position signal in response to utilizing serial peripheral interface protocol signal that includes information regarding the absolute position of the rotor, or in response to utilizing the pulse width modulation signal that includes information about an absolute position of a pole pair of the rotor. 
     
     
       10. The clutch actuation system of  claim 8 , wherein an absolute position of a pole pair of the rotor is transmitted by the sensor system via the serial peripheral interface protocol signal or the pulse width modulation signal to the analysis unit when the electric motor is started, whereupon the analysis unit is configured to supply current to the electric motor based on an incremental position of the rotor. 
     
     
       11. The clutch actuation system of  claim 10 , wherein the analysis unit is configured to analyze a pulse to no-pulse ratio of the pulse width modulation signal to transmit the absolute position of the pole pair of the rotor. 
     
     
       12. The clutch actuation system of  claim 10 , wherein the analysis unit is configured to carry out a comparison between the incremental position of the rotor and the absolute position of the pole pair. 
     
     
       13. The clutch actuation system of  claim 12 , wherein the comparison is carried out cyclically. 
     
     
       14. The clutch actuation system of  claim 8 , further comprising a small-diameter magnetic transmitter ring fastened to the rotor including one pole pair, wherein the small-diameter magnetic transmitter ring is configured to determine the position of the rotor. 
     
     
       15. The clutch actuation system of  claim 14 , further comprising a larger-diameter magnetic transmitter ring having a plurality of pole pairs, wherein the larger-diameter magnetic transmitter ring is fastened to the rotor of the electric motor and is configured to determine the position of the rotor, wherein a number of pole pairs of the magnetic transmitter ring is equal to a number of pole pairs of the rotor.