Method and control unit for determining a future rotational speed

Abstract

A method for determining a future rotational speed of a rotating drive shaft of an internal combustion engine is described, in particular while the internal combustion engine coasts after being turned off, the future rotational speed being calculated from a course of measured rotational speeds. To predict a future rotational speed of the drive shaft of the internal combustion engine as accurately as possible, instantaneous rotational speeds measured at different rotational positions of drive shaft are evaluated.

Claims

1. A method of predicting a future rotational speed of a rotating drive shaft of an internal combustion engine, for use in engaging the internal combustion engine with a starting device, the method comprising: measuring, using a measuring device of a control unit, a course of rotational speeds of the drive shaft, the measured course having an oscillation; evaluating, using an evaluation device of the control unit, the rotational speeds at different rotational positions of the drive shaft over only a substantially single period of the oscillation to determine a linear portion, equal to a slope determined from the rotational speeds, and an oscillating portion, determined using an oscillating characteristics curve and a selected amplitude characteristics curve, the selected amplitude characteristics curve being a function of rotational speed and selected from a plurality of different amplitude characteristics curves based on comparing a maximum amplitude of the oscillation to the plurality of different amplitude characteristics curves; predicting, using the evaluation device of the control unit, the future rotational speed as a function of the linear portion and the oscillating portion; and engaging the internal combustion engine with the starting device as a function of the predicted future rotational speed.

2. The method of claim 1, wherein the slope is determined as a regression line from the measured rotational speeds over the single period of the oscillation using an averaging method, and the future rotational speed is derived from the linear portion having the slope, having a base point for the linear portion which is a point of the regression line corresponding to a point in time of a most recently measured rotational speed which is considered when determining the future rotational speed.

3. The method of claim 1, wherein the slope is derived from the rotational speeds which were measured within a certain phase range of the oscillation, within a phase range having a positive or a negative amplitude of the oscillation, or within a phase range having a positive and, adjoining on each side, a negative amplitude, or having a negative and, adjoining on each side, a positive amplitude.

4. The method of claim 1, wherein the slope is evaluated from the measured rotational speeds between two extreme amplitudes distributed over the single period of the oscillation.

5. The method of claim 1, further comprising disregarding older rotational speeds when evaluating the rotational speeds, so that the oldest considered rotational speed is older by only the single period than a most recent considered rotational speed, and the most recent considered rotational speed is more recent than a one period duration of the oscillation of the course.

6. The method of claim 1, wherein an oscillation characteristic derived from the oscillation characteristics curve is scaled using the selected amplitude characteristics curve.

7. The method of claim 1, wherein a normalized rotational speed amplitude of the oscillating portion is determined using the oscillating characteristics curve, which is stored as a first reference table providing the normalized rotational speed amplitude as a function of the rotational position of the drive shaft.

8. The method of claim 7, wherein a scaled amplitude of the oscillating portion is determined using the selected amplitude characteristics curve, which is stored as a second reference table providing a rotational speed amplitude scaling as a function of the measured course of rotational speeds.

9. The method of claim 1, wherein the linear slope is determined as a regression line from the measured rotational speeds over the single period of the oscillation.

10. The method of claim 1, wherein the evaluating includes weighting the rotational speeds according to a density function, wherein measured rotational speeds having a low density over time are given a higher weighting than measured rotational speeds having a high density over time.

11. The method of claim 1, wherein the substantially single period extends from a rotational position of the drive shaft at which the measured course of rotational speeds has a first minimum to a rotational position of the drive shaft at which the measured course of rotational speeds has a second minimum.

12. The method of claim 1, wherein the substantially single period extends from a rotational position of the drive shaft at which the measured course of rotational speeds has a first maximum to a rotational position of the drive shaft at which the measured course of rotational speeds has a second maximum.

13. The method of claim 1, wherein the comparing determines differences between the maximum amplitude of the oscillation and the plurality of different amplitude characteristics curves, and the selected amplitude characteristics curve is selected based on the determined differences.

14. The method of claim 13, wherein the selected amplitude characteristics curve has the lowest difference from the maximum amplitude of the oscillation among the plurality of the different amplitude characteristics curves.

15. The method of claim 1, wherein the selected amplitude characteristics curve accounts for engine performance parameters.

16. The method of claim 1, wherein the oscillating characteristics curve and the selected amplitude characteristics curve are represented by reference tables stored in a memory.

17. A control unit for a start-stop system of a motor vehicle, comprising: a measuring device to measure a course of rotational speeds of a drive shaft of an internal combustion engine, the measured course having an oscillation; an evaluation device to: evaluate the rotational speeds at different rotational positions of the drive shaft over only a substantially single period of the oscillation to determine a linear portion, equal to a slope determined from the rotational speeds, and an oscillating portion, determined using an oscillating characteristics curve and a selected amplitude characteristics curve, the selected amplitude characteristics curve being a function of rotational speed and selected from a plurality of different amplitude characteristics curves based on comparing a maximum amplitude of the oscillation to the plurality of different amplitude characteristics curves; predict the future rotational speed as a function of the linear portion and the oscillating portion; and engage the internal combustion engine with a starting device as a function of the predicted future rotational speed.

18. The control unit of claim 17, wherein: a normalized rotational speed amplitude of the oscillating portion is determined using the oscillating characteristics curve, which is stored as a first reference table providing the normalized rotational speed amplitude as a function of the rotational position of the drive shaft, and a scaled amplitude of the oscillating portion is determined using the amplitude characteristics curve, which is stored as a second reference table providing a rotational speed amplitude scaling as a function of the measured course of rotational speeds.

19. A non-transitory machine-readable storage medium having program instructions, which when executed by a processor perform a method, the method comprising; measuring, using a measuring device of a control unit, a course of rotational speeds of a drive shaft of an internal combustion engine, the measured course having an oscillation; evaluating, using an evaluation device of the control unit, the rotational speeds at different rotational positions of the drive shaft over only a substantially single period of the oscillation to determine a linear portion, equal to a slope determined from the rotational speeds, and an oscillating portion, determined using an oscillating characteristics curve and a selected amplitude characteristics curve, the selected amplitude characteristics curve being a function of rotational speed and selected from a plurality of different amplitude characteristics curves based on comparing a maximum amplitude of the oscillation to the plurality of different amplitude characteristics curves; predicting, using the evaluation device of the control unit, the future rotational speed as a function of the linear portion and the oscillating portion; and engaging the internal combustion engine with a starting device as a function of the predicted future rotational speed.

20. The non-transitory storage medium of claim 19, wherein: a normalized rotational speed amplitude of the oscillating portion is determined using the oscillating characteristics curve, which is stored as a first reference table providing the normalized rotational speed amplitude as a function of the rotational position of the drive shaft, and a scaled amplitude of the oscillating portion is determined using the amplitude characteristics curve, which is stored as a second reference table providing a rotational speed amplitude scaling as a function of the measured course of rotational speeds.

21. A method for determining a future rotational speed of a rotating drive shaft of an internal combustion engine, while the internal combustion engine coasts after being turned off, the method comprising: measuring, using a rotational speed sensor, a course of rotational speeds of the drive shaft, the measured course having an oscillation; evaluating, using an evaluation device of a control unit, the rotational speeds at different rotational positions of the drive shaft over only a phase range of the oscillation, the phase range having substantially equal portions above and below a center line of the measured course, to determine a linear portion, equal to a slope determined from the rotational speeds, and an oscillating portion, determined using an oscillating characteristics curve and a selected amplitude characteristics curve, the selected amplitude characteristics curve being a function of rotational speed and selected from a plurality of different amplitude characteristics curves based on comparing a maximum amplitude of the oscillation to the plurality of different amplitude characteristics curves; predicting, using the evaluation device of the control unit, the future rotational speed as a function of the linear portion and the oscillating portion; and engaging the internal combustion engine with a starting device as a function of the predicted future rotational speed.

22. The method of claim 21, wherein: a normalized rotational speed amplitude of the oscillating portion is determined using the oscillating characteristics curve, which is stored as a first reference table providing the normalized rotational speed amplitude as a function of the rotational position of the drive shaft, and a scaled amplitude of the oscillating portion is determined using the selected amplitude characteristics curve, which is stored as a second reference table providing a rotational speed amplitude scaling as a function of the measured course of rotational speeds.

23. The method of claim 21, wherein the oscillating characteristics curve and the selected amplitude characteristics curve are represented by reference tables stored in a memory.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a circuit diagram including a control unit for a start-stop system.

(2) FIG. 2 shows a flow chart of a method for operating the control unit.

(3) FIGS. 3 and 4 show a time-rotational speed diagram of a coasting internal combustion engine.

(4) FIG. 5 shows a standard amplitude characteristics curve diagram.

(5) FIG. 6 shows a standardized oscillation characteristics curve.

(6) FIG. 7 shows a time-rotational speed diagram of a coasting internal combustion engine and the determination of a future rotational speed.

DETAILED DESCRIPTION

(7) FIG. 1 shows a circuit diagram including a control unit 1 for a start-stop system of a motor vehicle and including an internal combustion engine 2 having six cylinders 3. The start-stop system turns off internal combustion engine 2 when the motor vehicle stops temporarily, e.g., at a red traffic light, by interrupting a fuel supply, and it restarts internal combustion engine 2 to continue driving. For this purpose, the start-stop system includes a starting device for internal combustion engine 2 having a starter motor 4, which is coupled to internal combustion engine 2 for starting in that a starter pinion 5 is meshed with a ring gear 8 of internal combustion engine 2 via a lever 7 with the aid of a starter relay 6, ring gear 8 being situated on a drive shaft 9 of internal combustion engine 2.

(8) Control unit 1 also includes a measuring device 10 for measuring instantaneous rotational speeds n.sub.s, n.sub.p of drive shaft 9 having a rotational speed sensor 11 which detects instantaneous rotational speeds n.sub.s, n.sub.p with the aid of a gear wheel 12 situated on drive shaft 9 at different rotational positions of drive shaft 9, namely at a tooth position .sub.z of gear wheel 12 in each case. In an alternative control unit 1, instantaneous rotational speeds n.sub.s, n.sub.p and rotational positions are transmitted and receivable by an external measuring device.

(9) Moreover, control unit 1 includes a microcomputer 13 as an evaluation device and a memory 14 having a computer program product for executing the subsequently described method steps, in particular for determining a future rotational speed n, namely for a later point in time t.sub.0, from a course n.sub.v of measured rotational speeds n.sub.s, n.sub.p.

(10) Control unit 1 is supplied with electrical power by a battery 15. Starter motor 4 and starter relay 6 are activated by control unit 1 with the aid of driver circuits (not illustrated in greater detail) and are supplied with electrical power by battery 15.

(11) FIG. 2 shows a flow chart of a method for operating control unit 1 according to FIG. 1.

(12) In a step S1, internal combustion engine 2 is turned off by control unit 1, by interrupting the fuel supply, due to a start-stop operation strategy when the motor vehicle stops. Subsequently, previously operated internal combustion engine 2 coasts after being turned off, namely at a coasting n.sub.A which represents an actual rotation of drive shaft 9 during coasting and which is shown in FIGS. 3, 4, and 7.

(13) According to one specific start-stop operation strategy, starter pinion 5 is to be meshed with ring gear 8, which rotates on drive shaft 9, at a later point in time t.sub.0, namely already during coasting n.sub.A, i.e., before a standstill of internal combustion engine 2, in order to enable an immediate restart of internal combustion engine 2 for continued driving of the motor vehicle. For this purpose, starter pinion 5 must rotate essentially synchronously, i.e., at synchronous peripheral speeds, in relation to ring gear 8 at point in time t.sub.0, in order to mesh with low wear. Accordingly, as explained in the following, a future rotational speed n.sub.0 for future point in time t.sub.0 is to be determined. In this way, it is eventually possible as a function of the prognosis of future rotational speed n.sub.0 to appropriately activate starter motor 4, having starter pinion 5, as well as starter relay 6 to mesh in time before point in time t.sub.0 in order to mesh at point in time t.sub.0, which may be synchronously.

(14) In a step S2, coasting n.sub.A is reproduced as course n.sub.v, as shown in FIG. 4, in that using rotational speed sensor 11 instantaneous rotational speeds n.sub.s, n.sub.p are measured and calculated by control unit 1 with the aid of measuring device 10 at different rotational positions of drive shaft 9. In this case, rotational speeds n.sub.s, n.sub.p paired with the time information and the rotational position information are available as data. All available data for each coasting n.sub.A may be detected and processed in microcomputer 10.

(15) Course n.sub.v is adjusted into the future to derive future rotational speed n.sub.0 at later point in time t.sub.0 from course n.sub.v of previously measured rotational speeds n.sub.s, n.sub.p. For this purpose, in a step S3, a regression line n.sub.M having a slope m of course n.sub.v is determined with the aid of a linear regression over selected rotational speeds n.sub.s, n.sub.p, as explained in FIG. 3.

(16) Coasting n.sub.A is determined by the friction and the load torques of internal combustion engine 2 which cause over time t an increasingly flatter, i.e., more curved, shape of course n.sub.v, as well as by compression and decompression cycles of cylinders 3 which result in an oscillation of course n.sub.v. It is possible to accurately describe a center line L, namely the oscillation-adjusted shape of course n.sub.v, at least sectionally due to the curvature, with the aid of regression line n.sub.M having slope m. However, the oscillation must additionally also be taken into consideration when adjusting course n.sub.v, as explained in the following starting from a step S4.

(17) In an alternative method, the oscillation is neglected, if it is only small, so that future rotational speed n.sub.0 is determinable with less calculating effort. For this purpose, future rotational speed n.sub.0 may be determined not only after a period duration P of the oscillation has elapsed, but it is rather particularly to determine future rotational speed n.sub.0 already after two measured or all available rotational speeds n.sub.s, n.sub.p, every additionally measured rotational speed allowing a more accurate prognosis.

(18) In step S4, the oscillation of course n.sub.v is determined based on maximum amplitudes E.sub.1, E.sub.2 which are illustrated in FIG. 4.

(19) In a step S5, an oscillating portion is derived from a standardized oscillation characteristics curve ETF illustrated in FIG. 6 and from a standard amplitude characteristics curve n.sub.SA shown in FIG. 5. Standardized oscillation characteristics curve ETF is scaled with the aid of standard amplitude characteristics curve n.sub.SA as a function of the rotational speed, namely using a simple calculation specification corresponding to a particular amplitude correction stage. In this way, instantaneous influences which have an effect on an amplitude of the oscillation, such as an intake manifold pressure, are considered during scaling.

(20) The appropriate amplitude correction stage is determined by a comparison; the amplitude correction stage results from a smallest deviation between maximum amplitudes E.sub.1, E.sub.2 measured previously and from the values calculated with the aid of the corresponding simple calculation specifications from standard amplitude characteristics curve G.sub.SA. An amplitude correction stage thus corresponds to an established calculation specification which, in particular, is configured as an approximate calculation using a multiplication and an additive term. An appropriate amplitude correction stage may be determined in each case over and over again depending on corresponding rotational speed n, thus improving the accuracy of the oscillating portion.

(21) In a step S6, as shown in FIG. 7, course n.sub.v is adjusted into the future for the determination of future rotational speed n.sub.0, namely using a linear portion n.sub.A1 which is superimposed by the oscillating portion.

(22) Steps S2 through S6 may be repeated in order to obtain a more accurate prognosis of future rotational speed n.sub.0 at point in time t.sub.0 in each case, namely by reducing the prognosis duration until point in time t.sub.0 on the one hand, so that the accuracy of the prognosis is increased, and by providing a plurality of prognoses on the other hand, so that in one method for smoothing a triple-slip mean value of the most recently determined prognoses of future rotational speed n.sub.0 is calculated, in order to further increase the accuracy of future rotational speed n.sub.0. In an alternative method, a plurality of slopes m, as will be explained later, is accordingly determined to derive future rotational speed n.sub.0 from slopes m with the aid of averaging, in particular with the aid of a triple-slip mean value. Alternatively, only the last complete period before a previously established mesh point in time is evaluated.

(23) FIG. 3 shows a time-rotational speed diagram having course n.sub.v of measured rotational speeds n.sub.s, n.sub.p, rotational speed n being plotted against a time axis t in the illustration. For the sake of clarity, only the two rotational speeds n.sub.s and n.sub.p and a most recent rotational speed n.sub.F, namely measured last by measuring device 10 at point in time t.sub.F, are named as examples. Moreover, course n.sub.v has the oscillation which is essentially caused by a movement of cylinder 3, as previously described. Furthermore, center line L of course n.sub.v is illustrated as a dashed line.

(24) Regression line n.sub.M was calculated via an averaging method, namely using a linear regression, via measured rotational speeds from n.sub.p through n.sub.s. Slope m of regression line n.sub.M represents a slope of center line L in the illustrated section of course n.sub.v, in particular during a period duration P, with high accuracy.

(25) Mean regression line n.sub.M may be represented as a linear equation using formula n=m*t+c, namely including slope m, time t, and a constant c.

(26) If individual measured rotational speeds n.sub.i are continuously numbered by variable i, the following results for a pth data set using the least squares method:

(27) $m_p=\frac{\left(\underset{i=1}{\overset{p}{.Math.}}{t}_i*n_i\right)-p*{\stackrel{\_}{t}}_p*\stackrel{\_}{n_p}}{\left(\underset{i=1}{\overset{P}{.Math.}}{t}_i^2\right)-p*{\left(\stackrel{\_}{t_p}\right)}^2},c_p={\stackrel{\_}{n}}_p-m*{\stackrel{\_}{t}}_p$
where:

(28) ${\stackrel{\_}{t}}_p=\frac{\left(p-1\right)*{\stackrel{\_}{t}}_{p-1}+t_p}{p},{\stackrel{\_}{n}}_p=\frac{\left(p-1\right)*{\stackrel{\_}{n}}_{p-1}+n_p}{p}$

(29) In this case, rotational speed n of regression line n.sub.M results at point in time t.sub.p of the pth data set from formula n=m.sub.p*t.sub.p+c.sub.p.

(30) Since rotational speeds n.sub.s, n.sub.p do not scatter accidentally around center line L, but are to a certain degree in a functional, sinus-like relation with regard to the oscillation, only selected rotational speeds are considered for the linear regression, namely rotational speeds from n.sub.p through n.sub.s which span such a segment of course n.sub.v which essentially corresponds to exactly one period duration P of the oscillation. As shown in FIG. 3, the segment is, for example, selected in such a way that it starts at a minimum of the oscillation and extends until the next minimum. Here, measured rotational speed n.sub.p is the first, i.e., the oldest, measured rotational speed, and rotational speed n.sub.s is the latest, i.e., the most recent, measured rotational speed which is considered for the linear regression, a few rotational speeds being measured beyond n.sub.s, in this example until n.sub.F, to identify the period. This selection of rotational speeds n.sub.p through n.sub.s to be considered allows the slope to be accurately determined by a linear regression despite the oscillation and, in particular, a compensation of the sinus-like oscillation requiring a lot of calculating effort to be avoided.

(31) In an alternative method, the linear regression is carried out from a maximum until the subsequent maximum. Moreover, not only in FIG. 3, the minima and the maxima of the oscillation are interchangeable as alternative methods with regard to the features described previously and in the following.

(32) Furthermore, a base point S on regression line n.sub.M at a point in time t.sub.s of most recent considered rotational speed n.sub.s is determined, which, as explained in FIG. 7, is used as base point S to adjust course n.sub.v into the future. Here, most recent considered rotational speed n.sub.s is older than most recently measured rotational speed n.sub.F by less than one period duration P. Thus, an instantaneous piece of information regarding actual coasting n.sub.A of internal combustion engine 2 is available with the aid of regression line n.sub.M in order to determine future rotational speed n.sub.0 as accurately as possible.

(33) Thus, oldest rotational speed n.sub.p, which is considered for the determination of future rotational speed n.sub.0, is spaced apart chronologically from most recent rotational speed n.sub.s, which is considered for the determination of future rotational speed n.sub.0, by maximally one period duration P of the oscillation of course n.sub.v. In this way, center line L may be described very accurately by regression line n.sub.M section by section, namely for the time interval of period duration P, namely in particular in the case of a curved course of center line L. Thus, older measured rotational speeds, which were detected before rotational speed n.sub.p, are disregarded and are no longer detected by the linear regression. In this way, an instantaneous slope and also an instantaneous base point S are always available for an accurate determination of future rotational speed n.sub.0.

(34) In one method, interlacing of the linear regression calculation is used, multiple consecutive regressions, as previously described, being carried out which start alternatingly, for example, at consecutive minima and maxima of the oscillation. In this way, it is possible to determine a regression line n.sub.M, i.e., slope m and base point S, in a greater chronological density, i.e., approximately every half period duration P.

(35) In another method, it is averaged in each case via most recently determined slope m of regression line n.sub.M with the aid of a method of the slipping mean value, in particular using a triple-slip mean value, in order to determine future rotational speed n.sub.0 more accurately by smoothing slopes m each calculated by regression.

(36) In another method, for measured rotational speeds n.sub.s, n.sub.p of course n.sub.v, which are not equidistant over time, the individual measured values are weighted with regard to a suitable density function to increase the accuracy of the averaging for regression line n.sub.M. The values may be balanced out section by section, one section in the positive range of the oscillation with regard to center line L being, for example, surrounded by sections in the negative range, in such a way that measured values having a lower density, i.e., greater time intervals, are provided with a higher weighting factor.

(37) In one method, the oscillation's influence on the accuracy of the prognosis is reduced in that selected ranges of the course are determined based on an oscillation characteristics curve ETF, which is shown in FIG. 6, and only measured rotational speeds n.sub.s, n.sub.p from these ranges are used for the regression calculation. In this way, the accuracy when determining regression line n.sub.M may be increased, for example, by neglecting rotational speeds n.sub.s, n.sub.p which deviate more strongly from the center line.

(38) In an alternative method, all available measured rotational speeds n.sub.s, n.sub.p are, in the case of a small oscillation, included in the linear regression calculation. In this way, the accuracy may be increased due to a larger amount of data.

(39) FIG. 4 shows a time-rotational speed diagram having an enlarged section of FIG. 3. FIG. 4 shows actual coasting n.sub.A as well as its detection by course n.sub.v of measured rotational speeds n.sub.s, n.sub.p. Moreover, FIG. 4 shows how extreme amplitudes E.sub.1, E.sub.2 of the oscillation of course n.sub.v around center line L are determined. Extreme amplitudes E.sub.1, E.sub.2 each have the greatest deviation of course n.sub.v from center line L, namely upward in the case of a maximum E.sub.1 of the oscillation and also downward in the case of a minimum E.sub.2 of the oscillation.

(40) FIG. 5 shows a standard amplitude characteristics curve diagram having a standard amplitude characteristics curve n.sub.SA which represents a dependency of extreme amplitudes E.sub.1, E.sub.2 as a rotational speed correction n from rotational speed n. Standard amplitude characteristics curve n.sub.SA, i.e., its course, is specific to the engine type for particular internal combustion engine 2. It is stored in memory 14 as a reference table, so that it may be taken into consideration when determining future rotational speed n.sub.0 with little calculating effort using microcomputer 13. In this way, a complex calculation may be avoided.

(41) Furthermore, above and below standard amplitude characteristics curve n.sub.SA, different curves K.sub.1 through K.sub.6 are shown for illustrating purposes, the curves being calculated from standard amplitude characteristics curve n.sub.SA using defined calculation specifications according to different amplitude correction stages. The appropriate amplitude correction stage is determined, as previously described, by a comparison, namely for a smallest deviation between measured actual extreme amplitudes E.sub.1, E.sub.2 shown in FIG. 4 and corresponding values of shown curves K.sub.1 through K.sub.6 for corresponding rotational speed n.

(42) In one method, a learning algorithm analyzesaccording to an established scheme, e.g., an established time period, mileage and/or number of start-stop cycles, in particular as a function of the surrounding and/or operating conditions, as well as according to any combinations of these criteriathe correction measures used in the past and derives therefrom a new calculation specification for a new amplitude correction stage. In another method, the learning algorithm also calculates a new adjusted standard amplitude characteristics curve n.sub.SA for further use.

(43) FIG. 6 shows a standardized oscillation characteristics curve ETF, as an energy transformation characteristics curve which is characteristic for internal combustion engine 2 and which indicates a rotational speed amplitude, standardized to a value of one, as a function of a rotational position of drive shaft 9. Oscillation characteristics curve ETF describes the shape of the oscillation of course n.sub.v, namely only qualitatively since it is standardized to a value of one. For this purpose, it conformably indicates what portion of a maximum potential energy is currently converted into kinetic energy at drive shaft 9; this means that oscillation characteristics curve ETF characterizes the energy conversion from potential energy into kinetic energy and vice versa, which takes place cyclically. Minima .sub.2 of oscillation characteristics curve ETF typically are at the ignition TDC positions of the engine. There, the energy stored in the compression is at its maximum and thus does not contribute to the kinetic energy. Maxima .sub.1 of oscillation characteristics curve ETF, however, show rotational positions at which the kinetic energy is at its maximum.

(44) FIG. 7 shows the determination of future rotational speed n.sub.0 at later point in time t.sub.0, the determination being carried out by microcomputer 13. Course n.sub.v of measured rotational speeds n.sub.s, n.sub.p is adjusted into the future, i.e., along time axis t beyond base point S as predicted future rotational speed course n.sub.z, namely by superimposing a linear portion n.sub.A1 and the oscillating portion. In order to show the accuracy when determining future rotational speed n.sub.0, actual course n.sub.v of measured rotational speeds n.sub.s, n.sub.p is also additionally illustrated beyond base point S. This means that actual coasting n.sub.A was measured beyond point in time t.sub.0 as a test, even though these rotational speeds cannot be used to determine predicted future rotational speed n.sub.0. It is thus possible to directly compare predicted future rotational speed course n.sub.z and actual course n.sub.v.

(45) Future rotational speed n.sub.0 at point in time t.sub.0 is determined in that linear portion n.sub.A1, which has slope m of previously determined regression line n.sub.M and at which base point S is set, i.e., regression line n.sub.M is virtually adjusted into the future.

(46) To determine future rotational speed n.sub.0 more accurately, as mentioned previously, the oscillation of course n.sub.v is taken into consideration by the oscillating portion. For this purpose, oscillation characteristics curve ETF is scaled with the aid of standard amplitude characteristics curve n.sub.SA, taking into consideration the established simple calculation specification corresponding to the particular amplitude correction stage. All figures show only schematic and not true-to-scale representations. Moreover, reference is made, in particular, to the drawings as essential to the exemplary embodiments and/or exemplary methods of the present invention.