Abstract:
The invention relates to an electronically commutated electric motor comprising a stator and an especially permanent-magnetic rotor. The electric motor also comprises a control unit which is effectively connected to the stator and is designed to generate control signals for commutating the stator in such a way that the stator can generate a rotating magnetic field in order to rotate the rotor. The electric motor further comprises at least one rotor position sensor which is designed to detect a position, especially an angular position, of the rotor and generate a rotor position signal representing the position of the rotor. The control unit is designed to generate the control signals in accordance with the rotor position signal. According to the invention, the control unit is designed to sample and quantize the rotor position signal and generate a digital rotor position signal. The digital rotor position signal forms a time-related data stream which corresponds to the sampled and quantized rotor position signal. The control unit includes an interpolator which is designed to generate at least one intermediate value in the digital rotor position signal, said intermediate value lying between two successive rotor position values.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to an electronically commutated electric motor. The electronically commutated electric motor comprises a stator and a rotor. In certain embodiments the rotor is a permanent-magnetic rotor. The electric motor also comprises a control unit which is effectively connected to the stator and is designed to generate control signals for commutating the stator in such a way that said stator can generate a rotating magnetic field in order to rotate the rotor. The electric motor further comprises at least one rotor position sensor which is designed to detect a position, especially an angular position, of the rotor and generate a rotor position signal representing the position of said rotor. The control unit is designed to generate the control signals in accordance with the rotor position signal. 
         [0002]    An electric motor is known from the German patent publication DE 103 32 381 A1, in which a rotor position of a rotor is detected without sensors and a current profile of winding currents for rotationally moving the rotor over a rotor revolution runs continuously without abrupt jumps and does not have any current gaps during the detection of the rotor position without sensors. 
         [0003]    The problem with rapidly rotating, electronically commutated electric motors is that during an operation of the electric motor, the detection of the rotor position has to be performed with a high detection frequency if during a revolution of the rotor, a frequent change in a commutation pattern is to result. To meet this end, the control unit of the electric motor must then have a correspondingly high computing capacity. 
       SUMMARY OF THE INVENTION 
       [0004]    According to the invention, the control unit of the electronically commutated electric motor of the kind mentioned at the beginning of the application is designed to sample and quantize the rotor position signal and generate a digital rotor position signal. The digital rotor position signal forms a time-related data stream which corresponds to the sampled and quantized rotor position signal, wherein the control unit includes an interpolator which is designed to generate at least one intermediate value in the digital rotor position signal, said intermediate value lying between two successive rotor position values. By use of an interpolator, a sampling frequency of an analog-digital converter which samples and quantizes the analog rotor position signal can be advantageously smaller than without the interpolator. A computing power of the control unit, which, for example, is formed by an FPGA or an ASIC, can thereby be advantageously smaller than without an interpolator. 
         [0005]    The control unit is further preferably designed to generate the digital rotor position signal as a digital prediction-rotor position signal, wherein the digital prediction-rotor position signal, in particular the time-related data stream, comprises at least one or a plurality of future rotor position values which extend temporally beyond the rotor position values. The interpolator is preferably designed to generate the intermediate value between two future rotor position values. As a result of the prediction-rotor position signal formed in this way, the rotor position can advantageously be available for a current rotor position or for future rotor positions for commutating the electric motor. The rotor position predicted in this way can advantageously further be available for commutating the electric motor before the rotor position sensor, in particular an angle sensor, after converting a, e.g., analog rotor position signal to a digital rotor position signal, can make the rotor position signal, which was altered in this way, available for further signal processing. 
         [0006]    The rotor position sensor is preferably an angle sensor. The angle sensor is, for example, a giant magneto-resistive sensor (GMR sensor) or an anisotropic magneto-resistive sensor (AMR sensor). In another embodiment, the electric motor comprises, for example, a plurality of Hall sensors, which in each case are designed to generate an especially analog rotor position signal. The angle sensor, in particular the GMR sensor or the AMR sensor, is preferably designed to generate a temporally continuous, preferably representing an absolute rotor position in a temporally continuous manner, especially analog rotor position signal. An angular resolution of the angle sensor is then determined by means of a sampling rate of an analog-digital converter which converts the analog rotor position signal from analog to digital. 
         [0007]    In a preferred embodiment, the control unit is designed to correct the digital prediction-rotor position signal in accordance with further rotor positions detected by means of the rotor position sensor particularly according to the FIFO principle (FIFO=First In, First Out). For that purpose, the prediction-rotor position signal can, for example, be formed by a predefined number of rotor position values, wherein said rotor position values are updated according to the FIFO principle with each new rotor position value which is detected by the angle sensor—and furthermore preferably additionally converted by an analog-digital converter. The commutating of the electric motor can thereby also take place with non-stationary movement patterns. For example, the control unit can impinge a large number of commutation patterns, which are different from one another, on the stator during a revolution of the rotor. 
         [0008]    In a preferred embodiment, the control unit is designed to generate the digital prediction-rotor position signal using an approximation function in accordance with the rotor position signal as the output function to be approximated. The rotor position signal generated by means of the rotor position sensor can thereby be advantageously estimated for future rotor positions. 
         [0009]    The approximation function is preferably a polynomial, in particular at least of the second degree or exactly of the second or third degree. Further advantageous exemplary embodiments for an approximation function are a spline function or an exponential function. 
         [0010]    In an advantageous embodiment of the invention, the control unit comprises a timer and is designed to generate the prediction-rotor position signal in accordance with a time signal generated by the timer, wherein the clock frequency of said timer is greater than a repetition rate of successive rotor position values of the digital rotor position signal in order to commutate the stator in accordance with the prediction-rotor position signal. Said stator can thereby be advantageously commutated in accordance with interpolation values of said prediction-rotor position signal. 
         [0011]    To meet this end, the control unit can preferably be designed to ascertain the commutation time point at a preferably future rotor position value of the prediction-rotor position signal and is preferably further designed to commutate the stator at a future rotor position value. 
         [0012]    The invention also relates to a method for operating an electronically commutated electric motor, in particular the electric motor previously described. In the method, a rotor position is detected using a rotor position sensor and a rotor position signal is generated corresponding to the rotor position. Using the method, the rotor position signal is further preferably sampled and quantized, and an especially digital prediction-rotor position signal forming a time-related data stream is generated. The prediction-rotor position signal represents the sampled and quantized rotor position signal and comprises at least one or a plurality of future rotor position values which extend temporally beyond the rotor position signal. 
         [0013]    In a preferred embodiment of the method, the digital prediction-rotor position signal is corrected in accordance with further rotor positions detected using the rotor position sensor. 
         [0014]    In an advantageous embodiment variant of the method, the digital prediction-rotor position signal is generated by forming an approximation function as the output function in accordance with the rotor position signal. The output function is thereby the function to be approximated, which can thereby form nodes for generating the approximation function. In so doing, the prediction-rotor position signal can also be extrapolated beyond a region formed by the nodes—for example formed using the rotor position signal or generated from the same. The approximation function is preferably a polynomial function of the second or third degree. 
         [0015]    In a preferred embodiment of the method, a commutating of the stator takes place in accordance with the prediction-rotor position signal after a time interval has elapsed, wherein the lapse of time corresponds to a commutation time point. The commutation preferably takes place using at least one, preferably predefined, commutation pattern. In so doing, the commutation advantageously takes place already prior to a presence of a rotor position value that is generated using the rotor position sensor. 
         [0016]    In the method, the rotor position value is ascertained in accordance with the approximation function, for example in accordance with the polynomial, the spline function or another suitable approximation function. The multiplications necessary to meet this end can advantageously take place by means of a correspondingly rapid computing unit. 
         [0017]    The control unit can, for example, be a microprocessor, a microcontroller or a FPGA (FPGA=Field Programmable Gate Array) or an ASIC (ASIC=Application Specific Integrated Circuit). The control unit is controlled, for example, by a control program, which is stored on a data carrier and together with the data carrier form a computer program product. 
         [0018]    The invention also relates to a control unit in accordance with the aforementioned kind for an electric motor of the aforementioned kind The control unit then does not comprise a rotor and a stator and is designed to be connected to a stator of an electric motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention is described below with the aid of figures and further exemplary embodiments. Further advantageous embodiment variants result from the features previously described and from the features specified in the description of the figures as well as from the features specified in the dependent claims. 
           [0020]      FIG. 1  shows an exemplary embodiment for an electronically commutated electric motor including the control unit according to the invention; 
           [0021]      FIG. 2  shows a method for operating the electric motor depicted in  FIG. 1 ; 
           [0022]      FIG. 3  shows a diagram, which clarifies the principle of operation of the electric motor depicted in  FIG. 1  as well as the method depicted in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 1  shows an exemplary embodiment for an electronically commutated electric motor  1 . The electric motor  1  comprises a stator  10  having three stator coils, namely a stator coil  12 , a stator coil  14  and a stator coil  16 . The stator  10  also comprises an angle sensor, which can, for example, generate an analog rotor position signal. The angle sensor  18  is designed to detect a rotor position of a rotor  11  of the electric motor  1 . Said angle sensor  18  is connected to a control unit  30  by means of a connection  50 . The control unit  30  comprises an analog-digital converter  27 , which is connected on the input side to the connection  50  and thus to the angle sensor  18 . An angular resolution of the angle sensor is in the case of the analog rotor position signal, in particular the analog rotor position signal which is formed in a temporally continuous manner, determined by a sampling rate of the analog-digital converter. The analog-digital converter  27  is connected on the output side to a polynomial generator  29  via a connecting cable  54 . 
         [0024]    The analog-digital converter  27  is designed to sample the rotor position signal which is received on the input side via the connection  50  and to generate a temporal sequence of sample values, which in each case represent an amplitude value of the rotor position signal. The analog-digital converter  27  is connected on the output side to a polynomial generator  29  via a connecting cable  54 . The polynomial generator  29  is designed to generate an approximation function in accordance with sample values received via the connecting cable  54 —representing the rotor position of the rotor  11 , said approximation function representing at least approximately a curved line represented in places by the sample values. 
         [0025]    The polynomial generator is preferably designed to generate the approximation function using the method of least squares. 
         [0026]    The approximation function is preferably a polynomial, in particular a polynomial of the second or third degree. It is also conceivable—in particular in accordance with a required computing time of the polynomial generator—to use a polynomial higher than the third degree. 
         [0027]    The polynomial generator  29  is designed to determine polynomial coefficients of the previously ascertained approximation function, in particular of the polynomial, and will output said polynomial coefficients on the output side thereof via a connecting cable  56  to a coefficient storage  32 . For this purpose, the polynomial generator  29  has, for example a FIR filter for each polynomial coefficient. In this exemplary embodiment, there are three FIR filters  36 ,  38  and  39  which are depicted by way of example. The coefficient storage  32  is designed to keep polynomial coefficients generated by the polynomial generator  29  in store. Said coefficient storage  32  is connected on the output side to a predictor  34  via a connecting cable  58 . The predictor  34  is designed to read out the coefficients stored in said coefficient storage  32  via the connecting cable  58  and to generate a temporally successive data stream representing rotor position values and to output said data stream on the output side thereof to a control unit  42  via the connecting cable  60 . Said data stream thereby comprises temporally successive, future rotor position values—depicted as dots in this exemplary embodiment—which represent in each case a future rotor position that has not yet been detected by the angle sensor  18 —in particular having a higher angular resolution than the rotor position signal generated by the analog-digital converter. In this exemplary embodiment, said data stream forms the prediction-rotor position signal mentioned above. 
         [0028]    The approximation function, in particular the polynomial, can, for example, be formed as follows: 
         [0000]    
       
         
           
             
               
                 
                   y 
                   
                     e 
                     , 
                     n 
                   
                 
                  
                 
                   ( 
                   
                     Δ 
                      
                     
                         
                     
                      
                     n 
                   
                   ) 
                 
               
               = 
               
                 
                   
                     y 
                     e 
                   
                    
                   
                     ( 
                     
                       
                         ( 
                         
                           n 
                           + 
                           
                             Δ 
                              
                             
                                 
                             
                              
                             n 
                           
                         
                         ) 
                       
                       · 
                       
                         T 
                         a 
                       
                     
                     ) 
                   
                 
                 ≈ 
                 
                   
                     ∑ 
                     
                       i 
                       = 
                       0 
                     
                     g 
                   
                    
                   
                     
                       
                         a 
                         i 
                       
                       · 
                       Δ 
                     
                      
                     
                         
                     
                      
                     
                       n 
                       i 
                     
                   
                 
               
             
             , 
           
         
       
     
         [0029]    having 
         [0030]    y e,n ( )n)=predictor polynomial as the approximation function; 
         [0031]    n=sample value, whole number or number &lt;1; 
         [0032]    T a =sampling period; 
         [0033]    g=degree of the polynomial; 
         [0034]    a=polynomial coefficient 
         [0035]    The control unit  42  is connected to a timer  40  and is designed to commutate the stator  10  at least in accordance with the prediction-rotor position signal received via the connecting cable  60 . 
         [0036]    The control unit  42  is connected on the output side to a power output stage  25  of the electric motor  1  via a connection  53 . Said control unit  42  is designed to activate the power output stage  25  in order to generate a magnetic rotating field using the stator coils  12 ,  14  and  16 . For that reason, said power output stage  25  is connected on the output side via a connection  52  to the stator  10  and there to the stator coils  12 ,  14  and  16 . Said control unit  42  is designed to exactly determine the commutation time points for commutating the stator  10  in accordance with the in particular high-resolution time signal which is received by the timer  40 . Said control unit  42  is connected on the input side to a storage  62  via a bidirectional connection  61 . Current application patterns, which differ from one another and from which one current application pattern  62  is described by way of example, are stored in the storage  62 . Said control unit  42  can, for example, select one current application pattern from those kept in storage in accordance with the prediction-rotor position signal and supply the stator  10  with current in accordance with the current application pattern in order to generate the rotating field. 
         [0037]    The polynomial generator  29  can advantageously have a FIR (FIR=Finite Impulse Response) for each polynomial coefficient of the polynomial coefficients kept in store in the coefficient storage  32 . 
         [0038]    The control unit  42  is also connected on the input side thereof to the analog-digital converter  27  via the connecting cable  54  and can receive the digitized rotor position signal from said analog-digital converter. 
         [0039]    The control unit  42  is designed to activate proportionately the power output stage  35  in order to commutate the stator coils in accordance with the rotor position values calculated by the predictor  34 . A temporal repetition rate of the rotor position values of the rotor position signal generated by the predictor is thereby greater than the repetition rate of the digital rotor position signal generated by the analog-digital converter. 
         [0040]      FIG. 2  shows and exemplary embodiment for a method for commutating an electronically commutated electric motor. In the method, a rotor position of a rotor of the electronically commutated electric motor is detected in Step  70  in particular by means of an angle sensor and a rotor position signal is generated, which at least represents a rotor position of the rotor. In Step  72 , the rotor position signal is digitized by means of an analog-digital converter and a digitized rotor position signal is generated. In Step  74 , a polynomial, which at least closely approximates the digitized rotor position values, is generated in accordance with the digitized rotor position signal. In step  76 , polynomial coefficients are temporarily stored, which represent the previously formed polynomial. In Step  78 , a polynomial is formed in accordance with the previously generated polynomial coefficients by means of a predictor and a data stream is generated. Said data stream comprises rotor position values in a time range, in which the rotor position values detected by the angle sensor lie and in addition thereto comprises future rotor position values, which have not yet been detected by the angle sensor and/or are not yet represented by the signal generated by the analog-digital converter  24 . In this exemplary embodiment, said data stream further comprises rotor position values generated by interpolating so that a temporal clock frequency of the successive rotor position values of said data stream is greater than a sampling rate during analog-digital convertsion. In Step  80 , a commutation pattern is selected in accordance with said data stream and in Step  82 , current is applied to the stator according to the commutation pattern. 
         [0041]      FIG. 3  shows a diagram  90 . The diagram  90  comprises a time axis  91  and an amplitude axis  92 . 
         [0042]    The diagram  90  shows a curve  95 , which connects sample values  101 ,  102 ,  104 ,  106 ,  108 ,  110  and  112  to one another. The curve  95  corresponds to a polynomial, which, for example, has been generated by the polynomial generator  29  depicted in  FIG. 1  and which represents a rotor position profile. The polynomial is a polynomial of the third degree in this exemplary embodiment. 
         [0043]    Rotor position values  101 ,  103 ,  105 ,  107 ,  109 ,  111  and  113  are also depicted. 
         [0044]    The rotor position value  101  has been detected by the angle sensor, thus, for example, by the angle sensor depicted in  FIG. 1 . 
         [0045]    A time interval  96  and a time interval  98  are also depicted. The time interval  96  represents a sampling period of an analog-digital converter, for example, the analog-digital converter  27  depicted in  FIG. 1 . 
         [0046]    The rotor position values  100 ,  102 ,  104 ,  106 ,  108 ,  110  and  112  are in each case spaced at preceding and at succeeding rotor position values by means of the time interval  96 . 
         [0047]    The rotor position value  101  follows the rotor position value  100  after the time interval  98 . The rotor position value  103  follows the rotor position value  102  after the time interval  98 . Said time interval  98  thereby represents a computing time, which the analog-digital converter requires in order to execute the digitization of the rotor position signals sent by the angle sensor. 
         [0048]    The rotor position signals detected by the angle sensor are available in digitized form to the control unit—for example the control unit  30  in FIG.  1 —for further signal processing and for controlling the commutation time points later—in this example delayed by the time interval  98 —than said rotor position signals were detected by the angle sensor. The commutation time points  115  and  117  are depicted. The commutation time point  115  is spaced from the rotor position value  102  by the time interval  99 . The time interval  99  is shorter than the time interval  98  so that the commutation time point  115  occurs after the digital rotor position value  103  has been made available—said commutation time point corresponding to the rotor position of the rotor position value  102 . Intermediate values  118 ,  119  and  120  are also shown, which have been generated by the interpolator and in each case represent a rotor position. 
         [0049]    By generating the predictor polynomial and predicting the future rotor position values, which have not yet been detected by the angle sensor, a sampling frequency for detecting a rotor position of the rotor can be lower than without the prediction using the predictor polynomial. The low sampling frequency of the sampling of the rotor position signal is further advantageously compensated or improved by means of interpolation. 
         [0050]    If, for example the rotor position values  100 ,  102 ,  104  and  106  have been detected by the angle sensor, the rotor position value  108 , the rotor position value  110  and the rotor position value  112  as well as the intermediate values  118 ,  119 ,  120  can have been generated using the predictor polynomial. 
         [0051]    In a further development of the method for commutating the electric motor, the control unit, for example the control unit  42  in  FIG. 1 , can compare the rotor position values  108 ,  110  and  112  generated using the predictor with the rotor position values  109 ,  111  or respectively  113  detected by the angle sensor and use the results to form a further polynomial profile of the predictor polynomial. 
         [0052]      FIG. 4  shows an exemplary embodiment for a predictor  120 , which, for example, can be a component of the electric motor  1  in place of the predictor  34  shown in  FIG. 1 . The predictor  120  comprises an input  124  and an output  129 . The input  124  is connected to the timer  40  already depicted in  FIG. 1 . Said input  124  is connected to a multiplier  126  and a multiplier  128  via a connecting cable  121 . The multiplier  126  is also connected on the input side to an adder  123 . The adder  123  is connected on the input side to a connection  131  and to an input  132  via said connection  131 . The adder  123  can receive a polynomial coefficient via the input  132 , in this exemplary embodiment a polynomial coefficient a 2  of a polynomial of the second degree. 
         [0053]    The multiplier  146  is connected on the output side to an adder  125 . The adder  125  is connected on the input side to the multiplier  126  and also on the input side to the connection  131  that is of multi-channel design. Said adder  125  can receive a polynomial coefficient via the multi-channeled connection  131  and thus from the input  132 , in this exemplary embodiment a polynomial coefficient a 1  of the polynomial of the second degree. Said adder  125  is connected on the output side to the multiplier  128 . The multiplier  128  is connected on the output side to the adder  127 . The adder  147  is connected on the input side to the multiplier  128  and also on the input side to the input  132  via the connection  131  and can receive via said connection  131  a polynomial coefficient, in this exemplary embodiment a polynomial coefficient a 0  of the polynomial of the second degree. The adder  127  is connected on the output side to the output  129 . During an operation of the timer  41 , the predictor  120  can, for example, receive an especially ramp-shaped clock pulse signal  43  via the input  124 , the clock frequency of which is a multiple of a sampling frequency used by the analog-digital converter  27  during the analog-digital conversion. The clock pulse signal is, for example, designed ramp-shaped and has a predefined number of ramp steps. With each clock pulse period, in particular ramp step, of the clock pulse signal  43  received at the input  124 , the multiplier  126  multiplies an output signal received by the adder  123  with the clock pulse signal and outputs on the output side a multiplication result to the adder  125 . The adder  121  adds the multiplication result received from the multiplier  126  with the polynomial coefficient a 1  received from the input  132  and outputs on the output side a corresponding addition result to the multiplier  128 . The multiplier  128  multiplies the addition result received from the adder  125  with the clock signal, which the multiplier  126  also received from the input  124 . The multiplier  128  generates a corresponding multiplication result and outputs said result on the output side to an adder  127 . The adder  127  adds the multiplication result generated by the multiplier  128  to a polynomial coefficient a 0 , which the adder  127  received from the input  132  via the connection  131 . The adder  127  can then output the addition result to the output  129 —as a prediction-rotor position signal. The adder  123  can on the input side—depicted as dots—in the case of a polynomial higher than the second degree be connected to at least one further multiplier. The input  132  is, for example, connected to the connecting cable  58  depicted in  FIG. 1  and thus to the coefficient storage  32 . 
         [0054]      FIG. 5  shows an exemplary embodiment for a predictor  130 . The predictor  130  can, for example, replace the predictor  34  in  FIG. 1 . Said predictor  130  does not have—in contrast to the predictor  120  in FIG.  4 —a multiplier and can thus be provided in a manner allowing easy implementation—for example using an ASIC. 
         [0055]    The predictor  130  has an input  135  and an output  165  and is connected to a timer  134 . 
         [0056]    The predictor  130  comprises a plurality of integrators, which particularly together form a cascade. The integrators comprise in each case an adder and a storage. An adder  132  is depicted which is connected on the output side to a storage  133  via a connecting cable  152 . The storage  133  is connected on the output side to a further adder  136  via a connecting cable  154 . Said storage  133  is also connected on the output side to the adder  132  via a feedback connecting cable  154 . The storage  133  is also connected on the output side to the adder  132  via a feedback connecting cable  150 . The adder  132  forms together with the storage  133  an integrator. 
         [0057]    The storage  133  is connected on the output side to the adder  136  via a connecting cable  154 . The adder  136  is connected on the output side to a storage  137  via a connecting cable  156 . The storage  137  is connected in feedback relation on the output side to the adder  136  via a connecting cable  158 . The storage  147  is also connected on the output side to an adder  138  via a connecting cable  160 . Said adder  138  is connected on the output side to the output  165  via a connecting cable  162 . 
         [0058]    The adder  138 , the adder  136  and the adder  132  are also in each case connected on the input side to an input  135  and can receive a polynomial coefficient via said input  135 . The predictor  130  can be connected, for example, to the coefficient storage  32  depicted in  FIG. 1  via the input  135  and receive the polynomial coefficients from said coefficient storage  32 . 
         [0059]    The polynomial coefficients can be generated, for example, from the polynomial generator  29  as follows, in particular in accordance with the sampling rate of the analog-digital converter  27  in  FIG. 1 : 
         [0000]    
       
         
           
             
               b 
               0 
             
             = 
             
               a 
               0 
             
           
         
       
       
         
           
             
               b 
               1 
             
             = 
             
               
                 
                   a 
                   1 
                 
                 L 
               
               + 
               
                 
                   a 
                   2 
                 
                 
                   L 
                   2 
                 
               
             
           
         
       
       
         
           
             
               b 
               2 
             
             = 
             
               
                 a 
                 2 
               
               
                 2 
                 · 
                 
                   L 
                   2 
                 
               
             
           
         
       
     
         [0060]    having 
         [0061]    b 0 , b 1 , b 2  as clock pulse dependent polynomial coefficients 
         [0062]    L=multiple of the sampling frequency T a  of the analog-digital converter  27  in  FIG. 1   
         [0063]    The computing unit formed using the predictor  130  can be implemented by means of a microprocessor, a microcontroller or an FPGA (FPGA=Field Programmable Gate Array) or an ASIC (ASIC=Application Specific Integrated Circuit). The connection between the input  134  and the adder  132  is partially depicted with dots. This means that the predictor  130  can comprise further integrators, which are connected to the adder  132 , for calculating a polynomial of a higher degree. The predictor  130  is also connected on the input side to the timer  134 . The timer  134  is, for example, designed to produce a time signal which has an especially L-fold higher clock rate than a sampling rate used by the analog-digital converter  27 . 
         [0064]    The integrators of the predictor  130  are in each case connected to the timer  134  and perform in each case an arithmetic operation with the clock pulse specified by the timer  134 . The polynomial coefficients b 0 , b 1  and b 2  are made available from the input  135  with the clock pulse of the sampling frequency. The time  134  is, for example, designed to generate the clock pulse for clocking the integrators according to the following specification: 
         [0000]    
       
         
           
             
               f 
               Takt 
             
             = 
             
               L 
               · 
               
                 1 
                 
                   T 
                   a 
                 
               
             
           
         
       
     
         [0065]    having 
         [0066]    f Takt =clock frequency of the clock pulse for clocking the integrators, 
         [0067]    T a =sampling period, for example of the analog-digital converter  27  in  FIG. 1   
         [0068]    L=factor, advantageously as a power of a number L=2 n    
         [0069]    The factor L is advantageously selected as a power of the base of 2. The division operations for generating the polynomial coefficients b 0 , b 1  and b 2 , additionally preferred b n  can thus advantageously be generated using addition operations. The predictor  130  can thus output at output  165  the polynomial generated using the polynomial coefficients received at the input  135 —as a prediction-rotor position signal. The output  165  can, for example, be connected to the connecting cable  60  depicted in  FIG. 1  so that the predictor  130  is connected on the output side to the control unit  42 . The control unit  42  can, for example, in accordance with the polynomial received from the predictor  130 —as the prediction-rotor position signal—select a current application pattern  62  from the storage  65  and apply current to the stator  10  of the electric motor  1  using the power output stage  25  in accordance with the current application pattern.