Abstract:
The invention relates to a computer-controlled electronically commutated motor (ECM) and to an improved method for processing data therein. The computer&#39;s program executes the steps of: a) defining, in recurrent steps, the rotor position region in which a current pulse is to flow through the at least one winding phase, and the duration (TCurr) of that current pulse; b) sensing, in recurrent steps, the rotation-speed-dependent time period (TPP) required by the rotor to pass through a predetermined rotation angle range; c) monitoring the ratio between that rotation-speed-dependent time period (TPP) and the duration (Tcurr) of the current pulses; and d) as a function of the magnitude of that ratio, choosing a time to perform, in the computer, at least one predetermined calculation, either during (Flag_Fct_Within=1) the duration (TCurr) of a current pulse or in a time span outside (Flag_Fct_Within=0) a current pulse. As a result of this judicious time allocation, even an inexpensive computer can perform both commutation control and other calculation tasks without time conflicts.

Description:
This application is a section 371 of PCT/EP02/13772, filed 5 Dec. 2002 and published 26 Jun. 2003 as WO 03-052920-A1, claiming priority from German application DE 101 61 688.0, filed 15 Dec. 2001. This application incorporates by reference commonly assigned U.S. Ser. No. 10/433,139, BERROTH et al., filed 29 May 2003 as the U.S. phase of PCT/EP01/15184. 

   FIELD OF THE INVENTION 
   The invention relates to a method for processing data for an electronically commutated motor, and it relates to an electronically commutated motor for carrying out such a method. 
   BACKGROUND 
   An electronically commutated motor usually has an output stage which is controlled by a driver IC (Integrated Circuit) or a computer and must be switched on and off again as exactly as possible by that driver IC or computer so that a constant rotation speed and quiet motor operation are obtained. 
   This is difficult to achieve in practice, since a computer such as a microprocessor or microcontroller that controls the output stage must also perform other time-critical tasks, e.g. processing a frequency signal or a PWM (Pulse Width Modulation) signal and/or controlling the motor rotation speed. These signals must also be processed very accurately in order for the motor to run quietly. 
   There are a number of possibilities for this. For example, the output stages can be controlled very accurately using interrupt operations; the sensing of other signals becomes more inaccurate as a result, however, because accurate sensing of other signals is blocked during an interrupt for controlling the output stage. On the other hand, those other signals could be sensed via interrupt, and the output stages could instead be controlled using a method referred to as “polling”. In such a situation, if the program is currently sensing a signal, simultaneous monitoring of the output stages is not possible. The result of this is that the current in the relevant output stage is switched on or off too late, thereby causing the motor to run unevenly. 
   Both of the aforesaid possible solutions are therefore unsatisfactory. 
   A more powerful computer, capable of handling multiple time-critical functions via corresponding interrupts, could also be used. A computer of this kind would then, however, need to have a high clock frequency in order to execute the interrupt routines as quickly as possible, since even with this kind of computer these routines cannot be executed in parallel fashion. This approach would moreover be too expensive for most applications. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to make available a method for processing data for an electronically commutated motor, and an electronically commutated motor for carrying out such a method. 
   According to the invention, this object is achieved by monitoring a ratio between a rotation-speed-dependent time period (TPP) and a current pulse duration (Tcurr) and, as a function of that ratio, selecting either a time interval during a current pulse or a time span outside a current pulse as the time to perform certain calculation operations. A better distribution of the available system time is thereby obtained with simple and inexpensive means, so that time-critical functions can be performed without disruption. Since the time-critical rotational position regions of the rotor in which interrupt operations occur, as well as the placement of the energization blocks, are known in advance, with the method according to the present invention other calculation operations can be shifted into those rotor rotation regions in which no other time-critical signals need to be processed, so that even long calculation operations can be performed with no negative influence on how the motor runs. It is thereby possible, using even a simple microcontroller, to operate an electronically commutated motor reliably and to ensure that the motor runs quietly. 
   Another way of achieving the stated object is to control operations of the motor with a microcontroller whose program performs the steps discussed above. Using a single simple microcontroller, such a motor can implement numerous functions, e.g. calculating a target value from a delivered signal; measuring a true value for rotation speed; controlling rotation speed; generating an alarm signal in the event of extreme rotation speed deviations; and exact commutation, which results in quiet motor operation. 
   Further details and advantageous embodiments of the invention are evident from the exemplary embodiment described below and depicted in the drawings, which is in no way to be understood as a limitation of the invention. 

   
     BRIEF FIGURE DESCRIPTION 
       FIG. 1  is a highly schematic overview circuit diagram of an electronically commutated motor and of a computer  43  provided for controlling its commutation and rotation speed; 
       FIG. 2  is an overview flow chart depicting in schematic form the main program with the operations that occur in an electronically commutated motor of this kind during rotation of the rotor; 
       FIG. 3  is an overview depiction to explain the invention; 
       FIG. 4  is a depiction similar to  FIG. 3  showing the conditions in the motor at a high motor current that occurs, for example, at high rotation speeds; 
       FIG. 5  is a depiction similar to  FIGS. 3 and 4  showing the conditions in the motor at a low motor current that occurs at low rotation speeds; 
       FIG. 6  shows a Pos_Fct routine, indicating how certain calculation operations are allocated to certain parts of a program sequence according to a predetermined criterion; 
       FIG. 7  shows a routine indicating the operations that occur in the context of a Hall interrupt; 
       FIG. 8  shows a routine indicating which operations occur when a certain routine needs to be performed when a current is flowing in one of the phases of the motor winding; 
       FIG. 9  schematically depicts an example of a sequence for the situation in which the current pulses are short and certain calculation operations are performed in the time prior to a current pulse; and 
       FIG. 10  schematically depicts an example of a sequence for the situation in which the current pulses are long and certain calculation operations are performed during the duration of a current pulse. 
   

   DETAILED DESCRIPTION 
   In the description hereinafter, identical or identically functioning parts or functions are referred to using the same reference characters, and usually described only once, e.g. current pulses  132 ,  132   a ,  132   b ,  132   c , and  132   d.    
     FIG. 1  shows an electric motor  49  having a permanent-magnet rotor  50  which in this example is depicted as a four-pole rotor, i.e. has two North poles and two South poles, all of which have a length of 90° mech.=180° el. It is said in such a case, using the terminology of electrical machine design, that the pole pitch (PP) of one pole is 180° el.; and a Hall IC  60  located opposite rotor  50  generates, as the latter rotates, a square-wave HALL signal that is depicted in FIG.  3 A. 
   With a HALL signal of this kind it is easy, as depicted in  FIG. 3A , to measure the distance PP between two adjacent edges  142 ,  142 ; and the time TPP required therefore corresponds to the time required by rotor  50 , at its instantaneous rotation speed, for one quarter of a revolution. 
   EXAMPLE 
   Time TPP is assumed to be 1 ms=0.001 s. Rotor  50  then requires 4×0.001=0.004 second for one complete revolution, and its rotation speed is
 
1/0.004=250 revolutions per second.
 
   Since there are 60 seconds in a minute, rotor  50  is rotating at a speed of
 
(1/0.004)×60=15,000 rpm  (1)
 
   Since the time for one complete revolution (or indeed for part of a revolution) for an electric motor  49  having a Hall IC  60  can be measured easily and with very good accuracy, it is preferable, especially in the context of rotation speed controllers for electric motors, to work with time TPP or with a multiple N thereof (N=1, 2, 3, . . .), since this variable can be used directly after it is measured and is also required for controlling commutation of the motor. This time therefore represents, in the context of an electric motor, a more convenient indicator of rotation speed than any of the other variables such as rpm or revolutions per second; and if necessary, TPP can easily be converted into rpm by taking the reciprocal of the time T360° mech required for one revolution through 360° mech. and multiplying by 60, thus:
 
 n (rpm)=60/ T 360° mech  (2).
 
The time T used here must be in seconds.
 
   As  FIG. 1  shows, electric motor  49  used as an example has two stator windings  33 ,  35 . Winding  33  is connected between positive and ground  41  in series with a MOSFET  37 , and winding  35  in series with a MOSFET  39 . The two MOSFETs  37 ,  39  represent the output stages of motor  49 . The total current through motor  49  is labeled i, and is depicted schematically in FIG.  3 B. 
   Output stages  37 ,  39  are controlled by a computer  43 , usually a microcontroller (μC), to which HALL signals from Hall IC  60  are conveyed. μC  43  contains, in the form of program modules that are indicated only schematically, a commutation control system  47  “COMM,” a rotation speed controller  48  “n_CTL,” a calculation member  51  “SW_CALCII” for calculating a rotation speed target value TSoll for controller  48 , an alarm control system  54  for generating an ALARM signal for situations in which the rotation speed of motor  49  becomes too high or too low, a ROM  55  for storing a program, and an alarm delay counter  56  “AVZ” that coacts with alarm control system  54  which has an output  57  for the ALARM signal. The effect of AVZ  56  is that an alarm is triggered not directly, but only after an alarm condition has continuously existed, for example, for one minute. 
   Module  51  for target value calculation has conveyed to it from outside, e.g. from an external generator or sensor  58 , a corresponding signal that is converted in SW_CALC  51  into a rotation speed target value nsoll or TSoll. This is done preferably by means of a table that can be stored in ROM  55 . 
   This calculation of a target value requires many calculation steps and consequently a great deal of time, and is therefore preferably divided into several shorter parts. What is important is that these calculations must not interfere with the commutation of motor  49 , so that it runs quietly. Even the shorter parts of the target value calculation, however, can last so long that they impair exact commutation of motor  49 . The same applies to the calculation routines of rotation speed controller  48  and alarm module  54 . 
   Motor  49  that is depicted is, of course, only one very simple example of an arbitrary electronically commutated motor; it serves merely to facilitate understanding of the invention, and in no way limits it. 
     FIG. 2  shows the basic structure of the program sequence in μC  43  as rotor  50  rotates. This program works together with a Hall interrupt routine that is described in FIG.  7 . Each edge  142  ( FIG. 3 ) of the HALL signal causes an interrupt in which various program steps are executed and the values of two flags are determined, namely
 Flag_FctsEnable 
and
 Flag_Do_Fcts. 
   The overall program Main PRG of  FIG. 2  is labeled S 84 . After activation it goes to step S 86 , where a power-on initialization PowerOn_Init takes place and watchdog WD of computer  43  is reset. The program then goes to S 88 , where a reinitialization of the most important values takes place at each pass. S 89  then follows, in which the commutation state of motor  49  is continuously checked to determine whether one of output stages  37 ,  39  needs to be switched on or off. This constant checking is also referred to as “polling.” 
   The next step S 90  contains a routine CALC_Within, which is depicted in FIG.  8  and makes certain settings after the current in one of phases  33 ,  35  has been switched on. 
   The program then goes to S 92 , where it determines the value of flags Flag_FctsEnable and Flag_Do_Fcts. If that value is “1,” the program goes to S 94 , where these two flags are set to “0” so that at the next pass in step S 92 , the response is “0” and the program enters a short loop S 93 , which checks in recurrent steps, e.g. every 100 μs, whether one of output stages  37 ,  39  needs to be switched on or off. 
   S 94  is followed by a step S 98  in which the counter status of a Hall counter Hall_CNT is checked. If that status is even, the program goes into a left branch S 99 ; if it is odd, it goes into a right branch S 126 . 
   In left branch S 99  the program goes to S 100 , in which the target value determination SW_CALC is performed. 
   If the response in S 98  is NO, the program goes via right branch S 126  to S 108  Do_Actual_Speed where the actual value determination is performed, i.e. a value characterizing the instantaneous rotation speed of rotor  50  is measured or calculated. Following S 108  in S 116  is a controller, e.g. rotation speed controller n_CTL depicted at  48  in  FIG. 1 , or a current controller; and following that in S 118  is a function Pos_Fct which determines the rotor rotation region at which the calculation steps in the lower part of  FIG. 2  are to be performed at the next pass. This routine is depicted in FIG.  6 . The program then loops back to S 88 . 
   As rotor  50  rotates through 360° mech., the program thus runs through step S 98  four times, Hall_CNT successively assuming e.g. the values 1, 2, 3, 4, as depicted in  FIG. 1  for the HALL signal. As a result, either the target value for the rotation speed is calculated in S 100 , or the present rotation speed is sensed in S 108  and then processed in controller n_CTL, and a calculation is then performed in S 118  to define the rotor rotation point at which a predetermined routine is to be performed. S 118  can also be followed by a routine for generating the ALARM signal. 
     FIG. 3  explains the problems underlying the invention using a simple diagram.  FIG. 3A  depicts Hall signal HALL for the four-pole rotor  50 ,  FIG. 3B  shows the total current i at moderate load for motor  49  that is depicted, and  FIG. 3C  shows critical times in the life of μC  43  that controls and regulates motor  49 . 
   As  FIGS. 3A and 3B  show, it is desirable to control the current in motor  49  in such a way that its current blocks  132 ,  134 ,  136 ,  138 ,  140  extend approximately symmetrically with respect to the HALL signal, since this then results in good motor efficiency. This is called “center commutation,” i.e. the current flows at the point most favorable for the motor. As rotation speed increases, current blocks  132  through  140  are preferably shifted slightly to the left; this is referred to as “commutation advance.” This is symbolically depicted only for current block  134 , as a shifted current block  134 ′. 
   To ensure that the electronic system of motor  49  always “knows” the rotational position of rotor  50 , edges  142  of signal HALL must be sensed very accurately, i.e. by way of interrupt operations that are labeled “a” in FIG.  3 C. This is the purpose of the Hall interrupt routines of  FIG. 7 , which ascertain very exactly the time of an edge  142 . Based on the elapsed times between edges  142 , the electronics can then very accurately measure or calculate the time TPP needed by rotor  50  to pass through one pole pitch PP. 
   Another critical aspect in  FIG. 3  is the time span b in which current i is switched on in one of the two winding phases  33 ,  35 , and also the time span c in which that current i is switched off again. The corresponding points in time are calculated in advance by the electronics, and current i must be switched on as exactly as possible at the calculated time b, and switched off as exactly as possible at the calculated time c. If the current is switched on later than time b, too little energy is then delivered to motor  49  and its rotation speed falls. If the current is switched off too late at time c, too much energy is delivered to motor  49  and its rotation speed rises. The rotation of rotor  50  thus becomes inhomogeneous, causing vibration and noise. 
   Time spans b and c should therefore, to the greatest extent possible, be kept unencumbered by other calculation operations, in order to allow clean and exact commutation so that motor  49  runs quietly. 
     FIG. 4  is a depiction similar to  FIG. 3  but with long energization blocks  132   a ,  134   a ,  136   a ,  138   a , and  140   a  that are required at high rotation speeds. The consequence of these long energization blocks is that points c, a, and b are pushed close to one another, so that only very short calculations could be performed between them. With the present invention, therefore, in this case longer-duration calculations are performed between a point b and the subsequent point c, i.e. during the period in which a current block is flowing in the motor. 
     FIG. 5  shows the opposite situation, in which energization blocks  132   b ,  134   b ,  136   b ,  138   b , and  140   b  become very short because the motor is running at low speed and consequently requires little energy. The result of this is that points b and c are pushed close together. Only a very short calculation could therefore take place between these points, whereas in the time between Hall interrupt a and the subsequent switching-on b of a current block, there is sufficient time to perform even longer-duration calculations, since in the case of  FIG. 5  the rotation speed is low and time TPP is therefore quite long. 
     FIGS. 3 through 5  show that a time interval which can be used uninterruptedly for a very long time occurs only with long energization blocks (FIG.  4 ). The narrower the energization blocks, the more that time is subdivided into smaller regions. The time intervals are distributed most uniformly when the energization blocks have a length TCurr corresponding to one-third of TPP, as depicted in FIG.  3 . As the energization blocks become even smaller, as depicted in  FIG. 5 , the time interval between points b and c becomes increasingly short, but the time intervals before point b and after point c thus become correspondingly longer. 
   The invention therefore proceeds from the concept of performing necessary calculation procedures within the energization blocks when the blocks are long, and before (or after) the beginning of the energization blocks when the blocks are short, in order to improve the smoothness of motor  49 . 
   This means that the situation
 
 TCurr=TPP/ 3  (3)
 
is the point at which the calculation of certain operations should be relocated from one rotor rotation region to another rotor rotation region. This relocation can be accomplished, if applicable, using a switching. hysteresis, and is described in detail below with reference to flow charts.
 
   In  FIG. 2 , step S 108  is followed by step S 116  with rotation speed controller n_CTL which, each time the actual value is sensed again (in S 108 ), supplies a new value (e.g. 1256 μs) for the duration TCurr of an energization block. This (variable) value is depicted by way of example in FIG.  3 B. The most recent rotation speed target value TPP, which is depicted in  FIG. 3A , is known on the basis of the actual value determination in S 108 . 
   Controller routine S 116  in  FIG. 2  is therefore followed in S 118  by the Pos_Fct routine (FIG.  6 ), which serves to define the positions of certain-calculation routines in the program sequence so as not to disturb the commutation of motor  49 . 
   S 150  of  FIG. 6  checks whether energization time TCurr (defined by controller n_CTL in S 116 ) is longer than one-third of the rotation speed actual value TPP. If the situation as shown in  FIG. 4  exists, the response is YES; in other words, longer calculation operations can be performed during the time span TCurr of an energization block. A Flag_Fct_Within is therefore set to 1 in S 152 . 
   If, on the other hand, the situation as shown in  FIG. 5  exists, the response in S 150  is then NO, and that same flag is therefore set to  0  in S 154 . The routine then goes to S 156  Return. 
   The value of Flag_Fct_within thus defines where and when certain calculation operations are performed. 
   Once this matter has been clarified, it is necessary to watch for the arrival of the moment at which those calculation operations can begin at the point defined in FIG.  6 . The following conditions are used for this purpose: 
   CONDITION 1 
   If the calculation is to be accomplished outside an energization block  132 ,  134 , etc., it can be started directly after execution of the Hall interrupt. These are points  133 ,  133 ′,  133 ″,  133 ′″ in FIG.  5 . 
   CONDITION 2 
   If the calculation is to be accomplished within an energization block  132 ,  134 , etc., it cannot begin until 
   a) the Hall interrupt (routine “all” in  FIG. 3 ) 
   AND 
   b) the energization start operation (routine “b”, in FIG.  3 ), are complete. These are points  131 ,  131 ′,  131 ″,  131 ′″ in FIG.  4 . 
   These two conditions are defined by the flags
 
Flag_FctsEnable
 
and
 
Flag_Do_Fcts.
 
   Every time an edge  142  of the HALL signal occurs—which is also referred to as a “Hall change” because the Hall signal then changes either from 0 to 1 or from 1 to 0—this causes a Hall interrupt S 160  that is depicted in FIG.  7 . 
   In S 162  a variety of steps are performed, e.g. steps necessary for commutation; once they are complete,
 
 Flag   —   FctsEnable= 1
 
is set in S 164  because Condition 1 (as explained above) has been met.
 
   If the calculations can now be started, Flag_Fct_Within has a value 0 (cf. S 154  in FIG.  6 ), and the response in S 166  is therefore “0” and Flag_Do_Fcts is set in S 168  to “1.” The routine then goes to S 170  Return. The calculation operations can thus begin at points  133 ,  133 ′, etc. of FIG.  5 . 
   Both flags are thus set, and in the main program ( FIG. 2 ) the response in S 92  is “1,” so that one of the functions in the lower part of  FIG. 2  is executed. The particular function executed depends on the state of Hall counter Hall_CNT, which is polled in S 98 . 
   If, however, Flag_Fct_Within has a value of “1” in S 166  of  FIG. 7 , then
 
 Flag   —   Do   —   Fcts= 0
 
is set in S 172 ; i.e. the response in S 92  of  FIG. 2  is “0”; the program then enters loop S 93  and repeats it at intervals of approx. 100 μs, checking whether or not the current block in the relevant phase  33  or  35  of the motor winding presently needs to be switched on. (Other calculation routines should not be performed during this monitoring operation, since otherwise the switching-on time could in some circumstances be considerably delayed.)
 
     FIG. 8  shows the corresponding CALC_Within routine S 90  for the case in which Flag_Fct_Within has a value of 1. This routine S 90  is also shown schematically in FIG.  2 . 
   Step S 178  inquires whether the current in the relevant phase is presently switched on. If NO, the routine goes directly to S 180  Return, and monitoring to determine whether the current should be switched on is continued. 
   If the response in S 178  is YES, S 182  then checks whether both flags 
   Flag_FctsEnable (S 164  in  FIG. 7 ) AND 
   Flag_Fct_Within (S 152  in  FIG. 6 ) have a value of 1. 
   If NO, the program goes to S 180  Return. If YES, it goes to S 184 , where
 
 Flag   —   Do Fcts= 1
 
is set, i.e. both conditions are now met in S 92 , and the calculation steps that are to be performed at that time in  FIG. 2  below S 92  can be performed; as already described, in S 94  both flags of query S 92  are reset to 0, so that at the next pass through S 92 , the program once again enters the short loop S 93  in order to monitor, at closely spaced time intervals (e.g. every 100 μs), shutoff of the current in phase  33  or  35  that is presently carrying current.
 
   In this case, therefore, the calculations below S 92  ( FIG. 2 ) cannot be performed until after points  131 ,  131 ′,  131 ″, etc. of  FIG. 4 , since it is only there that the conditions
 
 Flag   —   FctsEnable= 1
 
AND
 
 Flag   —   Do   —   Fcts= 1
 
are met. In  FIG. 4  these calculations are accomplished after points  131 ,  131 ′, etc., i.e. during the period in which a current is flowing through phase  33  or  35 .
 
   In  FIGS. 9 and 10  described below, the letters a, b, and c have the same significance as in FIG.  3 . 
     FIG. 9  shows the conditions at a rotation speed of 1500 rpm. Here rotor  50  requires 40 ms for one revolution, i.e. it requires 10 ms=10,000 μs for each quarter-revolution or one pole pitch PP. 
   Assuming that controller n_CTL defines a control output TCurr of 1.35 ms (since little energy is required here), there remains before each current pulse  132   c ,  134   c  a period of approximately 4 ms in which calculations can be performed, for example the calculations in S 100  of  FIG. 2  before pulse  132   c , and the calculations in S 108 , S 116 , and S 118  before pulse  134   c , as indicated in FIG.  9 B. These calculations then take place after a Hall interrupt “a” and before a current pulse  132   c ,  134   c  is switched on (“b”). 
     FIG. 10  shows the conditions at 4500 rpm, on the same time scale as FIG.  9 . In this case one complete revolution of rotor  50  lasts 13.33 ms, and a quarter-revolution consequently lasts 3.33 ms. 
   Assuming a control output TCurr (from controller n_CTL) of 3 ms=3000 μs, what remains available for calculation operations is, for example, 2900 μs. The calculation operations in S 100  of  FIG. 2  can thus be performed during current pulse  132   d , and the operations in steps S 108 , S 116 , and S 118  during current pulse  134   d , as depicted in FIG.  10 B. These calculations thus take place after a current pulse  132   d ,  134   d  is switched on (“b”), and before it is switched off (“c”). 
   The operations in the lower part of  FIG. 2  may in some cases need to be distributed over several subroutines. If the SW_CALC routine is long, for example, it could be divided into two routines SW_CALC 1  and SW_CALC 2  which are each shorter than 2 ms, so that the various calculations do not interfere with one another. In this case, for example, SW_CALC 1  would then be performed during current pulse  132   d , SW_CALC 2  during current pulse  134   d , and steps S 108 , S 116 , and S 118  during the next current pulse  136   d . Many variants, adapted to the nature, length, and priority of the calculations to be performed, are thus possible. Since the target value calculation in particular often requires a great deal of calculation time, this function needs to be called more frequently than, for example, function  5108 , which is based on a simple time measurement. 
   A preferred type of commutation by means of polling is described in detail in DE 200 22 114.0 U1=PCT/EP01/15184 =WO 02-054567-A2 published 11 Jul. 2002=U.S. Ser. No. 10/433,139 filed May 29, 2003, which is therefore incorporated by reference in order to avoid excessive length. Commutation can be accomplished in a variety of ways known to those skilled in the art, commutation in accordance with DE 200 22 114.0 U1 and U.S. Ser. No. 10/433,139 being preferred. 
   Many variants and modifications are of course possible in the context of the present invention. A number of possibilities for further embodiments and refinements of the inventive concept can result from consideration of additional variables, for example the nature, duration, and priority of the calculations that need to be performed at a particular moment.