Abstract:
An electric motor, having a stator ( 465 ), a rotor ( 470 ), and an apparatus for evaluating a signal provided for controlling said motor ( 110 ), comprises a receiving unit ( 430, 440 ) for receiving a control signal (PWM_mod), which is a pulse width modulated signal (PWM) onto which a data signal (DIR, DATA) is modulated. An evaluation unit ( 440 ) is provided for evaluating the modulated control signal (PWM_mod). The unit is configured to extract, from the modulated control signal (PWM_mod), data provided for operation of the motor ( 110 ). The control apparatus includes a signal generator ( 450 ) configured to generate, on the basis of the extracted or ascertained data provided for operation of the motor ( 110 ), at least one control signal for the motor ( 110 ), such as a commanded direction of rotation. Piggybacking other control data onto the PWM power level signal reduces hardware investment, by permitting omission of a signal lead which would otherwise be required in the motor structure.

Description:
CROSS-REFERENCE 
     This application is a §371 of PCT/EP2009/09267, filed 24 Dec. 2009 and published 29 Jul. 2010 as WO 2010-083877-A1, and further claims priority from German application 10 2009 006 433.8, filed 24 Jan. 2009, the entire content of which is incorporated by reference. 
     FIELD OF THE INVENTION 
     The invention relates to an electric motor and to an apparatus for generating a signal for controlling an electric motor. 
     BACKGROUND 
     It is known from EP 1 413 045 B1 and corresponding U.S. Pat. No. 7,068,191, KUNER &amp; SCHONDELMAIER, to control electric motors using pulse width modulation (PWM). The control pulses are, in this context, applied to the motor in the form of a PWM signal having a constant clock frequency (period length T=constant). The duration t of the current pulses or associated pulse off-times (T−t) is variable; the rotation speed of the motor is specified by the pulse duty factor t/T of the PWM signal. A change in the pulse duty factor t/T correspondingly produces a change in the rotation speed. 
     Whereas rotation speed control of the electric motor can be performed using a suitable PWM signal, data that must likewise be transferred to the motor while it is in operation, for example a desired rotation direction, must (according to the prior art) be transferred to the motor via an additional lead. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to make available a novel electric motor and a novel apparatus for generating a signal for controlling the same. 
     This object is achieved by an apparatus for generating a PWM signal with additional control data modulated thereon, for controlling an electric motor, by a corresponding method including steps of generating the PWM signal and modulating the additional data thereon, and by an electric motor structure including a control circuit which receives the specially modulated control signal, extracts therefrom at least one control command, and generates a corresponding driving signal for the motor. 
     In this context, a data signal is modulated onto a PWM signal so that an additional lead for transferring the data signal is not necessary. 
    
    
     
       BRIEF FIGURE DESCRIPTION 
       Further details and advantageous refinements of the invention are evident from the exemplifying embodiments that are described below and depicted in the drawings, in which: 
         FIG. 1  is a block diagram of an arrangement having a control apparatus  120  and an electrical load  110 , 
         FIG. 2  is a block diagram of an embodiment of control apparatus  120  of  FIG. 1 , 
         FIG. 3  is a block diagram of an embodiment of signal generator  126  of  FIG. 2 , 
         FIG. 4  is a block diagram of an embodiment of electrical load  110  of  FIG. 1 , 
         FIG. 5  is a block diagram of an arrangement having a control apparatus  120  and multiple electrical loads, namely two motors  530  and  540  and two heating elements  550  and  560 , 
         FIG. 6  is a flow chart showing a method for generating a control signal, according to an embodiment, 
         FIG. 7  is a diagram showing a sequence of a PWM signal for power control, according to an embodiment, 
         FIG. 8  is a diagram showing a first control sequence generated on the basis of the PWM signal of  FIG. 7 , 
         FIG. 9  is a diagram showing a second control sequence generated on the basis of the sequence of the PWM signal of  FIG. 7 , 
         FIG. 10  is a diagram showing a first control signal generated on the basis of the control sequence of  FIG. 8 , 
         FIG. 11  is a diagram showing a second control signal generated on the basis of the control sequence of  FIG. 8 , 
         FIG. 12  is a diagram showing a third control signal generated on the basis of the control sequence of  FIG. 8 , 
         FIG. 13  is a flow chart showing a method for evaluating such a control signal, 
         FIG. 14  is a diagram showing a control sequence which serves, in the context of the arrangement according to  FIG. 5 , to address the desired motor of the two motors  530  (M 1 ) or  540  (M 2 ), to transmit to it a rotation direction signal DIR, and to control the power level (or rotation speed) of that motor by means of a simultaneously transmitted pulse duty factor PWM; 
         FIG. 15  is a diagram showing a control sequence for the arrangement according to  FIG. 5 , in which after a start signal, firstly motor M 1  is addressed and receives a PWM signal, and then the clockwise rotation direction signal (R) is transferred to motor  1  together with the PWM signal; this is again followed by the start signal, and after that an analog signal sequence for motor M 2 , 
         FIG. 16  is a flow chart showing the sequence upon generation of the control signal of  FIG. 14   b , and 
         FIG. 17  is a flow chart showing the sequence upon readout of data from the modulated PWM signal of  FIG. 14   b.    
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an arrangement  100  having an electrical load or consumer CONS  110  and a control apparatus  120 . It contains a modulator  122 , to whose one input  124  a PWM signal is applied during operation, as depicted as an example in  FIG. 7 . Modulator  122  further has an input  126  to which data can be applied, e.g. a signal for the desired rotation direction of a motor, and if applicable further inputs, e.g. an input  128  for addressing a device, e.g. a motor M 1  or M 2  as depicted in  FIG. 5 . 
     The PWM signal (of input  124 ) can be modulated with the data at input  126  or at input  128 , as depicted in  FIGS. 8 and 9 , so that, for example, at output  130  of modulator  122  a modulated PWM signal PWM_mod is obtained with which it is possible to control the rotation direction and power level of motor M 1  of  FIG. 5  via a single lead, or alternatively the addressing of a motor M 1  or M 2  in  FIG. 5 , in order to transfer data to it. 
     According to an embodiment, the control signal PWM_mod specifies an electrical power level, to be delivered to load  110  from a voltage source Ub, and contains data that are necessary for the operation of load  110 , as will be described below with reference to  FIGS. 8 and 9 . These data describe, for example, an operating parameter of load  110  that specifies an operating mode of that load. For example, the load is operated in a first operating mode when the data of signal PWM_mod specify a first operating parameter, and in a second operating mode, when those data specify a second operating parameter. 
     To illustrate the invention, a description is given below of preferred exemplifying embodiments, in which load  110  is an electric motor that can be operated clockwise or counterclockwise. Operating data or operating parameters correspondingly determine an associated rotation direction; for example, a first operating parameter means “clockwise” and a second operating parameter means “counterclockwise.” Electric motor  110  can serve to drive a pump that is operable both forward and backward, the power level being individually modifiable, in both rotation directions, by the signal PWM_mod. 
       FIG. 2  shows, by way of example, an implementation of control apparatus  120  having a signal generator  126  for generating a modulated control signal PWM_mod. Generator  126  has a transmitting unit  127 . The generator has applied to it, on the one hand, a signal PWM from a control unit  125  and, on the other hand, a rotation direction signal DIR from a device  124  via a lead  129 , which signal specifies (in  FIG. 1 ) the rotation direction of a motor  110  that can constitute load  110 . 
     Device  124  is connected here to a rotation direction specifier  123 , e.g. a switch contact that generates a signal DIR* when actuated. Upon reception of a signal DIR*, device  124  generates a corresponding rotation direction signal DIR that is applied to modulator  126 . 
     Signal PWM can derive from any source. Here control unit  125  is connected to a device  122  to which a temperature signal T_Sens is delivered from a temperature sensor  121 . Sensor  121  can be arranged, for example, on an object to be cooled, in order to sense its temperature. Device  122  derives, from T_sens, a temperature signal, and sends a corresponding signal T to control unit  125 . 
     The latter is implemented, for example, using a microcontroller that generates the pulse-width-modulated signal PWM in a program-controlled manner. This signal has a pulse duty factor that is dependent on temperature signal T and regulates an electrical power level to be applied to load  110  ( FIG. 1 ). Correspondingly, a high electrical power level can be delivered to load  110  when the present temperature T is high, and a low power level at a low temperature, in order, for example in the case of a motor  110 , to influence the rotation speed correspondingly. Motor  110  can also be shut off when the present temperature T falls below a predetermined threshold value. A suitable method for generating the signal PWM is known from EP 1 413 045 B1, to whose entire content reference is made, in order to avoid lengthiness. 
     In an embodiment, signal generator  126  is configured to generate the modulated control signal PWM_mod to drive load  110 . For this, signal generator  126  modulates the data signal DIR onto the signal PWM in such a way that the pulse duty factor of the signal PWM can be extracted from the modulated control signal PWM_mod. The modulated control signal PWM_mod thus specifies, by its pulse duty factor, the electrical power level to be applied to load  110 , while other data necessary for the operation of load  110  are modulated onto that signal. Transmitting unit  127  then transfers the modulated control signal PWM_mod via a control lead  130  to load  110 , as shown in  FIG. 1 . 
       FIG. 3  shows, by way of example, an implementation of signal generator  126  of  FIG. 2  that is equipped with transmitting unit  127  and to which the pulse width modulated signal PWM and data signal DIR are applied. Signal generator  126  has a signal lead  310  for a voltage Ub, and a ground lead  320 . Lead  310  is connected to a voltage regulator  330  that is connected on its output side to a control element  340 , e.g. a microcontroller, connected to ground lead  320 . Voltage regulator  330  is configured to supply control element  340  with a substantially constant operating voltage. Control element  340  is connected, on its output side, to a driver  350  for transmitting unit  127 , and serves to process the pulse width modulated signal PWM and data signal DIR. 
     Transmitting unit  127  has two resistors  362 ,  372  that are connected, on the one hand, to driver  350  and, on the other hand, to a respective associated semiconductor switch  360 ,  370 . Semiconductor switch  360  is a PNP transistor whose base is connected to resistor  362 . Its emitter is connected to lead  310 , and its collector to transfer lead  130 . Semiconductor switch  370  is an NPN transistor whose base is connected to resistor  372 . Its emitter is connected to ground lead  320 , and its collector to transfer lead  130 . 
     When signal generator  126  is in operation, control element  340  specifies the pulse duty factor of the pulse width modulated signal PWM, and the data or operating parameters that are specified by the data signal DIR. Control element  340  then drives semiconductor switches  360 ,  370  via driver  350  and resistors  362 ,  372  so that they generate, from the supply voltage Ub, a control voltage Ub(t) that constitutes the control signal PWM_mod that is transferred to motor  110  on lead  130 . As already mentioned above, this control signal PWM_mod has the pulse duty factor of the pulse width modulated signal PWM, and carries the data of data signal DIR. 
     An example of a method of generating the control signal PWM_mod is described below, with reference to  FIG. 6 , in order to illustrate the manner of operation of control element  340  and of driver  350 . 
       FIG. 4  shows an exemplifying embodiment of the electric motor  110  of  FIG. 1 , which motor represents an example of an electrical load and comprises a supply lead  480  as well as a ground lead  420 . The control signal PWM_mod, which is present at lead  480  as voltage Ub(t), is applied to electric motor  110  via lead  130  of  FIG. 3 . This voltage is delivered via lead  480  to an energy buffer  430 , and to an evaluation unit  440  connected to ground lead  420 , which unit is likewise connected on the input side of energy buffer  430 . Energy buffer  430  and evaluation unit  440  thus constitute a receiving unit for receiving the control signal PWM_mod from lead  130 . 
     Evaluation unit  440  is connected, on the output side, to a signal generator  450  that is, in turn, connected on the output side to motor components  460  of motor  110 . These components encompass, for example, a stator  465  having at least one stator winding and an associated power stage transistor. Stator  465 , whose at least one stator winding is connected to lead  480  and to ground lead  420 , has a rotor  470  associated with it. 
     When electric motor  110  is in operation, the signal that is specified by the pulse duty factor of the control signal PWM_mod and is to be applied to the motor is delivered by the voltage Ub(t), conveyed on lead  480 , to the at least one stator winding of stator  465 , while evaluation unit  440  evaluates the control signal PWM_mod in order to ascertain the data provided for operation of the motor, and the corresponding operating parameter, on the basis of the control signal PWM_mod. As a function of the operating parameter that is determined, signal generator  450  is driven, in turn, in order to generate a drive signal for the associated power stage transistors of stator  465 , and in order to operate the motor in an operating mode corresponding to the ascertained operating parameter. For example, the drive signal can be configured to commutate corresponding power stage transistors of stator  465  in such a way that the motor is operated clockwise when the operating parameter specifies clockwise running. 
     An example of a method of evaluating the control signal PWM_mod is described below, with reference to  FIG. 13 , in order to illustrate the manner of operation of evaluation unit  440  and signal generator  450 . 
       FIG. 5  shows an arrangement  500  in which the control voltage Ub(t) of  FIG. 3 , generated by control apparatus  120 , which voltage constitutes the control signal PWM_mod of  FIG. 1 , is delivered via a transfer lead  510  to a plurality of exemplifying electrical loads  530 ,  540 ,  550 ,  560  connected to a ground lead or bus  520 . These can be configured in a manner similar to electric motor  110  of  FIG. 4 , in order to perform an evaluation of the control signal PWM_mod and to be operated as a function of an operating parameter determined in that context. For example, load  530  can be implemented by electric motor  110  of  FIG. 4 , whereas load  540  is rotatable in only one rotation direction and can thus be implemented without the components described in  FIG. 4  for evaluating the signal PWM_mod. As an alternative to this, both loads  530 ,  540  can be implemented like electric motor  110  of  FIG. 4 , while loads  550 ,  560  represent, by way of example, heating elements that can be implemented without the components described in  FIG. 4  for evaluating the signal PWM_mod. 
       FIG. 6  shows an exemplifying method  600  for generating the control signal PWM_mod of  FIGS. 1 to 4 , which method is executed, for example, by signal generator  126  of  FIG. 3 . It begins in step S 610  with the reception or reading in of the pulse width modulated signal PWM of  FIG. 2 . 
       FIG. 7  shows an exemplifying diagram  700  of a pulse width modulated signal PWM that is formed from the supply voltage Ub of  FIG. 3  and has successive signal elements; for simplification, only three signal elements  710 ,  720 ,  730  (Block  1 , Block  2 , Block  3 ) are shown in  FIG. 7 . According to an embodiment, these constitute a signal sequence  750  (SEQ PWM). Signal elements  710 ,  720 ,  730  have a respective pulse off-time  712 ,  722 ,  732  having a predetermined constant off-time duration T L1 , and subsequent thereto a respective pulse  714 ,  724 ,  734  having a predetermined constant pulse duration T L2 . The off-time duration T L1  and pulse duration T L2  are each specified as a function of the power level to be applied to electric motor  110 ; the pulse duty factor T L2 /(T L1 +T L2 ) calculated from the off-time duration T L1  and pulse duration T L2  determines the power level to be applied, i.e. the higher the power level to be set, the greater the pulse duty factor. 
     Referring again to  FIG. 6 , in step S 620  the off-time duration T L1  of signal elements  710 ,  720 ,  730  of  FIG. 7  is measured. Their pulse duration T L2  is then measured in step S 630 . Then, in steps S 640  to S 660 , the data signal DIR of  FIG. 2  is modulated onto the signal PWM; according to an embodiment, at least the off-time duration T L1  and pulse duration T L2  of at least two successive signal elements of the signal PWM are modified, while maintaining its pulse duty factor, as a function of the data of the data signal DIR. A description will be given below, by way of example, of a process of modulating on a data signal DIR which comprises data that specify, as an operating parameter, a clockwise direction (DIR=R) for electric motor  110  of  FIGS. 1 and 4 . 
     In step S 640 , a first signal element of the control signal PWM_mod is generated; this has, for example, an off-time duration T M1  and a pulse duration T M2  that correspond to the off-time duration and pulse duration of signal element  710  of  FIG. 7 , i.e. T M1 =T L1  and T M2 =T L2 . In step S 650 , a second signal element, subsequent to the first signal element, is generated. This has an off-time duration T M3  that corresponds to the off-time duration T L1  of signal element  720  of  FIG. 7  lengthened by an amount equal to a predetermined duration T D  i.e. T M3 =T L1 +T D . 
     Its pulse duration T M4  corresponds to pulse duration T L2  of signal element  720  of  FIG. 7  shortened by an amount equal to the duration T D , i.e. T M4 =T L2 −T D . 
     In step  660 , a third signal element subsequent to the second signal element is generated. This has an off-time duration T M5  that corresponds to the off-time duration T L1  of signal element  730  of  FIG. 7  shortened by an amount equal to the duration T D , i.e. T M5 =T L1 −T D . Its pulse duration T M6  corresponds to pulse duration T L2  of signal element of  FIG. 7  lengthened by an amount equal to duration T D , i.e. T M6 =T L2 +T D . A modulated control signal PWM_mod generated in this manner is shown by way of example in  FIG. 9 . 
     The method  600  then ends at step S 670  with transfer of the control signal PWM_mod to electric motor  110 , as described above with reference to  FIGS. 3 and 4 . 
     As already mentioned, the control signal PWM_mod generated in accordance with the method  600  of  FIG. 6  controls clockwise running of electric motor  110  of  FIGS. 1 and 4 . In order to generate a control signal PWM_mod for counterclockwise running of motor  110 , the second signal element generated in step S 650  can be configured with an off-time duration T M3  that corresponds to the off-time duration T L1  of signal element  720  of  FIG. 7 , shortened by an amount equal to a predetermined duration T D , i.e. T M3 =T L1 −T D , while its pulse duration T M4  corresponds to pulse duration T L2  of signal element  720  of  FIG. 7 , lengthened by the duration T D , i.e. T M4 =T L2 +T D . 
     In addition, the third signal element generated in step S 660  can have an off-time duration T M5  that corresponds to the off-time duration T L1  of signal element  730  of  FIG. 7 , lengthened by an amount equal to duration T D , i.e. T M5 =T L1 +T D , while its pulse duration T M6  corresponds to pulse duration T L2  of signal element  730  of  FIG. 7 , shortened by the duration T D , i.e. T M6 =T L2 −T D . 
     A control signal PWM_mod generated in this manner is shown in  FIG. 8 . 
     Be it noted, however, that the use of method  600  to generate the second and third signal elements for modulated control signals PWM_mod that are suitable for controlling clockwise or counterclockwise running of electric motor  110  of  FIGS. 1 and 4  is described only by way of example. 
     A description is given below, with reference to  FIGS. 14 to 17 , of how separate driving of different devices, for example motors M 1  and M 2  of  FIG. 5 , is possible. 
       FIG. 8  shows a diagram  800  of an exemplifying signal sequence  850  (SEQ L) of a control signal PWM_mod that, in accordance with an embodiment, specifies the “counterclockwise” operating parameter for motor  110  of  FIGS. 1 and 4  and was generated on the basis of the pulse width modulated signal PWM of  FIG. 7 . Signal sequence  850  correspondingly has three successive signal elements  810 ,  820 ,  830  having pulse off-times  812 ,  822 ,  832  and pulses  814 ,  824 , and  834  respectively subsequent thereto. 
     First signal element  810 , which serves as a reference signal element, has pulse off-time  812  having an off-time duration T M1  and pulse  814  having a pulse duration T M2 , which correspond to the off-time duration and pulse duration of signal element  710  of  FIG. 7 , i.e. T M1 =T L1  and T M2 =T L2 . 
     Second signal element  820  has pulse off-time  822  having an off-time duration T M3  and pulse  824  having a pulse duration T M4 , where T M3 =T L1 −T D  and T M4 =T L2 +T D . 
     Third signal element  830  has pulse off-time  832  having an off-time duration T M5  and pulse  834  having a pulse duration T M6 , where T M5 =T L1 +T D  and T M6 =T L2 −T D . 
     The pulse duty factor of signal sequence  850  corresponds to the pulse duty factor of signal sequence  750  of  FIG. 7 , i.e. T L2/ (T L1 +T L2 )=T M2 +T M4 +T M6 )/(T M1 +T M2 +T M3 +T M4 +T M5 +T M6 ). 
     To this extent, as described above, the electrical signal applied by the control signal PWM_mod to motor  110  corresponds to the one that was applied to motor  110  by the pulse width modulated signal PWM of  FIG. 7 . 
       FIG. 9  shows a diagram  900  of an exemplifying signal sequence  950  (SEQ R) of a control signal PWM_mod that, in accordance with an embodiment, specifies the “clockwise” operating parameter for motor  110  of  FIGS. 1 and 4  and was generated on the basis of the pulse width modulated signal PWM of  FIG. 7 . Signal sequence  950  has three successive signal elements  910 ,  920 ,  930  having pulse off-times  912 ,  922 ,  932  and pulses  914 ,  924 , and  934  respectively subsequent thereto. 
     First signal element  910 , which once again serves as a reference signal element, has pulse off-time  912  having an off-time duration T M1  and pulse  914  having a pulse duration T M2 , which correspond to the off-time duration and pulse duration of signal element  710  of  FIG. 7 , i.e. T M1 =T L1  and T M2 =T L2 . Second signal element  920  has pulse off-time  922  having an off-time duration T M3  and pulse  924  having a pulse duration T M4 , where T M3 =T L1 +T D  and T M4 =T L2 −T D . 
     Third signal element  930  has pulse off-time  932  having an off-time duration T M5  and pulse  934  having a pulse duration T M6 , where T M5 =T L1 −T D  and 
     T M6 =T L2 +T D . 
     The pulse duty factor of signal sequence  950  corresponds to the pulse duty factor of signal sequence  850  of  FIG. 8  and signal sequence  750  of  FIG. 7 . 
       FIG. 10  shows a diagram  1000  of a first embodiment of a control signal PWM_mod that specifies the “counterclockwise” operating parameter for motor  110  of  FIGS. 1 and 4  and was generated on the basis of the pulse width modulated signal PWM of  FIG. 7 . It has a plurality of successive signal sequences; to simplify the depiction, only three signal sequences  1010 ,  1020 ,  1030  are illustrated. These all correspond to the counterclockwise sequence  850  of  FIG. 8  or to a signal sequence defining the desired operating parameter, which sequence is generated continuously upon generation of the control signal PWM_mod. 
       FIG. 11  shows a diagram  1100  of a second embodiment of a counterclockwise control signal PWM_mod having three exemplifying signal sequences  1110 ,  1120 ,  1130 ; sequence  1110  corresponds to the counterclockwise sequence  850  of  FIG. 8 , and sequences  1120 ,  1130  correspond to PWM sequence  750  of  FIG. 7 . According to the second embodiment, the counterclockwise sequence  850  of  FIG. 8 , or a signal sequence defining the desired operating parameter, is correspondingly generated only once, when driving of motor  110  of  FIGS. 1 and 4  begins. 
       FIG. 12  shows a diagram  1200  of a third embodiment of a counterclockwise control signal PWM_mod having three exemplifying signal sequences  1210 ,  1220 ,  1230 ; sequences  1210  and  1230  correspond to the counterclockwise sequence  850  of  FIG. 8 , and sequence  1220  corresponds to PWM sequence  750  of  FIG. 7 . Sequence  1230  is offset, by way of example, from sequence  1210  by a predetermined duration  1240  (T p ). According to the third embodiment, the counterclockwise sequence  850  of  FIG. 8 , or a signal sequence defining the desired operating parameter, is correspondingly generated repeatedly after each expiration of the predetermined duration  1240  (T p ). 
       FIG. 13  shows, by way of example, a method  1300  of evaluating the control signal PWM_mod of  FIGS. 8 to 12  that is executed by evaluation unit  440  of  FIG. 4 . This method begins in step S 1310  with reception or reading in of the control signal PWM_mod. Method  1300  for evaluating the pulse durations of the signal elements of control signal PWM_mod of  FIG. 8  is described below. Be it noted that the method can be applied analogously to their off-time durations. 
     In step S 1320 , pulse duration T M2  of first signal element  810  is measured. Pulse duration T M4  of second signal element  820  is then measured in step S 1330 , and in step S 1340  pulse duration T M6  of third signal element  830  is measured. 
     Step S 1352  tests whether pulse duration T M2  is greater than pulse duration T M4  and less than pulse duration T M6 . As described above with reference to  FIG. 9 , this is the case if the control signal PWM_mod contains signal sequence  950  of  FIG. 9  and thus specifies the “clockwise” operating parameter (DIR=R) for motor  110  of  FIGS. 1 and 4 , which is ascertained in step S 1360 . In this case, method  1300  ends at step S 1370 , in which evaluation unit  440  of  FIG. 4  drives signal generator  450  of  FIG. 4  so that the latter, in turn, generates a driving signal for the associated power stage transistors of stator  465  of  FIG. 4 , in order to operate motor  110  clockwise. 
     In the present exemplifying embodiment of control signal PWM_mod of  FIG. 8 , however, the result in step S 1352  is “No,” and proceeding from step S 1352 , a test is made in step S 1354  as to whether pulse duration T M2  is less than pulse duration T M4  and greater than pulse duration T M6 . If that is the case here, the “counterclockwise” operating parameter (DIR=L) for motor  110  of  FIGS. 1 and 4  is determined in step S 1380 . Method  1300  then ends at step S 1390 , in which evaluation unit  440  of  FIG. 4  drives signal generator  450  of  FIG. 4  so that the latter, in turn, generates a control signal for the associated power stage transistors of stator  465  of  FIG. 4 , in order to operate motor  110  counterclockwise. Otherwise, the method can return, for example, to step S 1320 , in order to be repeated in a looped manner until ascertainment of a suitable operating parameter is possible. 
       FIG. 14  shows a signal sequence which serves to modulate onto the PWM signal, at input  124  of  FIG. 1 , firstly a start signal  200 , then an address signal ADR  202  (e.g. for one of motors  530 ,  540  of  FIG. 5 ), and then a rotation direction signal DIR  204  for said motors. According to  FIG. 14   b , eight signal blocks B 1  to B 8  corresponding to these specifications are generated for this purpose, as described later on with reference to  FIG. 16 . 
       FIG. 15  shows a signal sequence  210  which serves to set the rotation direction of motor  530  ( FIG. 5 ) to clockwise (DIR 1 =R) and the rotation direction of motor  540  to counterclockwise (DIR 2 =L). A start signal  212 , which is modulated onto PWM signal  124  ( FIG. 1 ), is followed by an address signal ADR 1   214  for motor  530  and then, in part  216 , by a rotation direction signal DIR 1 =R, i.e. clockwise. 
     This is then followed by a new start signal  218  which can be identical to start signals  200  and  212 , and then at  220  by an address signal ADR 2  for motor  540  and then, at  222 , by the rotation direction signal DIR 2 =L, i.e. counterclockwise, for that motor. The PWM signal at input  124  is continuously measured. The value that is transferred can be buffered in the relevant motor. 
       FIG. 16  schematically shows generation of the signal sequence according to  FIG. 14   b . This contains eight signal blocks B 1  to B 8  that have been calculated in accordance with the instantaneous pulse duty factor PWM and the data at inputs  126 ,  128 . This is done with reference to the values T L1  and T L2  of  FIG. 7  that are measured at input  124  (cf. steps S 230 , S 232  in  FIG. 16 ). Each block Bn has a pulse off-time and a pulse which follows that off-time. Block B 1  is then outputted in S 234  (OUT Block  1 ). In this context:
 
 T   M1   =T   L1   −T   D   (1)
 
 T   M2   =T   L2   +T   D   (2).
 
T D  has the same meaning as in  FIG. 6 , to which the reader is referred.
 
     An analogous calculation is made in S 236 : 
     for block B 2 
 
 T   M3   =T   L1   −T   D   (3)
 
 T   M4   =T   L2   +T   D   (4).
 
These two values are outputted as block B 2 .
 
     Analogously for block B 3  (cf. step S 238 ):
 
 T   M5   =T   L1   −T   D   (5)
 
 T   M6   =T   L2   +T   D   (6).
 
These two values are outputted as block B 3  (OUT Block B 3 ).
 
     In the subsequent steps S 240 , S 242 , S 244 , S 246 , and S 248 , blocks B 4  to B 8  are analogously calculated and are outputted as modulated PWM signals. The flow chart of  FIG. 16  ends with step S 250 . 
     Evaluation of the signal of  FIG. 14   b , for example in a motor or in another device to be controlled, is shown in  FIG. 17 . 
     After starting at S 256 , in the context of the signal sequence of  FIG. 14   b , the time T M2  is measured in step S 258 , and the time T M4  is measured in step S 260 , i.e. MEAS T M2  and MEAS T M4 . 
     Step S 262  tests whether these times are identical in magnitude. If No, that means a start signal  200  cannot be present, and the program returns to S 258 . If the response in S 262  is Yes, then pulse duration T M6  is measured in S 264 , and pulse duration T M5  in S 266 . 
     S 268  then checks whether T M6 =T M5 , and whether T M4  is greater than T M6 , i.e. whether a start signal is present. If No, the program goes back to S 258 . If the response is Yes, a start signal  200  is present and the program proceeds to step S 270 , where pulse durations T M10  and T M12  are measured. The criterion here is that for an address signal  202 , duration T M10  must be greater than duration T M12 . This is therefore checked in S 272 , and if the response is No (i.e. an address is not present), the program goes back to S 258 . 
     If the response in S 272  is Yes, pulse durations T M14  and T M16  are measured, and if T M14  is greater than T M16 , which is tested in S 274 , the program goes to S 276 , where the instruction DIR=R (i.e. clockwise) is decoded. If the response in S 274  is No, the program goes to S 278 , where the instruction DIR=L (i.e. counterclockwise) is decoded. 
     The power level of the motor being addressed is specified by the pulse duty factor PWM, which in accordance with  FIG. 7  is evaluated from the ratio T L2 /(T L1 +T L2 ), i.e. the power level of the motor, or its rotation speed, rises as the pulse duty factor increases. 
     Be it noted that the various parameters are preferably selected so that the ratio of important pulse lengths undergoes no change as a result of modulation with regard to operation of the motor. This is particularly evident in terms of start signal  200  depicted in  FIG. 14   b . Here the two longer blocks B 1  and B 2  are of identical length, and the two shorter blocks B 3  and B 4  are likewise of identical length, and these properties undergo no change as a result of modulation, so that the start signal can be easily and reliably sensed even after modulation. The same applies analogously to address signal  202  and rotation direction signal  204 . 
     It is thereby possible to transfer the signal sequences either via separate signal leads or also by correspondingly driving the operating voltage that is delivered, for example in  FIG. 5 , to the two motors M 1 , M 2  or heating elements  550 ,  560 . 
     The invention therefore relates, inter alia, to an apparatus in which an arrangement for generating an address signal is provided, which arrangement can be activated in order to address a device in conjunction with the transfer of a modulated control signal to that device. The signal generating apparatus is preferably configured to transfer, prior to transfer of an address signal, a start signal START. The latter preferably contains a sequence of pulses that have the same pulse duration at least in pairs, and it preferably comprises a number of signal elements (e.g. B 1 , B 2 , B 3 , B 4 ) that is greater than 2, for example 4. 
     Many variants and modifications are, of course, possible within the scope of the present invention.