Patent Application
20110192225
The present invention relates to the recordings of rotational velocity using a digital angular position transducer, which records the position of a transducer wheel.
In order to record the rotational speed of a shaft, for instance, a shaft of an electric machine, a transducer wheel is connected to the shaft and the rotation is recorded by recording markings on the edge of the transducer wheel. The markings correspond to certain angular positions, so that the angular position transducer signal indicates the points in time at which angular positions exist, for instance, using a clock signal slope. Consequently, the angular position or the angular velocity is not measured directly, but is calculated from the time duration, between two points in time, which corresponds to two different successive angular positions. The current angular velocity is thus burdened by an error which comes about by imprecise positioning of the markings on the transducer wheel. If, for instance, the transducer wheel is not manufactured in a highly precise manner, or if the markings are deformed or soiled, angular position signals come about that are shifted in time, because of these errors, and in the course of the revolution they lead to a fluctuating present angular velocity, although the transducer wheel is actually being rotated at constant velocity.
The angular velocity signal is thus burdened with a noise which acts interferingly on the dynamics, particularly in the case of dynamic regulating processes. For example, in the case of electric machines or internal combustion engines, but particularly in the case of electric machines, that are used for driving a hybrid vehicle or an electric vehicle, the angular velocity has to be regulated in highly dynamic fashion at very short reaction times.
Averaging the angular velocity over a time period or over one or more revolutions would, in particular, remove the high-frequency components from the angular signal, which are required for the precise dynamic control. Consequently, the noise brought about by the transducer wheel imprecisions cannot be reduced by averaging without giving rise to serious disadvantages in the dynamics of the sensor signal.
German document DE 102 00 504 7088 A1 discusess a method for producing a simulated transducer curve when a marking gap occurs in a transducer disk. In this instance, an additional angular position sequence is extrapolated from the measuring angular position signals, in order to close the gap. The document essentially relates to the extrapolation of angular signals, and does not focus on recording angular velocities. The document particularly does not look at errors that are created by the erroneous arrangement of teeth, but relates to the closing of gaps that come about from completely missing markings of the transducer wheel.
German document DE 102 58 846 A1 discusess a device for recording rotational angles, which makes it possible to make a statement about the absolute angular position. Just as in the previously named document, in this document we shall not look in greater detail at an angular velocity signal error due to imprecisions in the transducer signal.
Consequently, in highly dynamic regulation processes, angular recording mechanisms, according to the related art, have the disadvantage that imprecisions in the transducer wheel lead to unnecessary regulating compensation processes. On the one hand, the unnecessary regulating compensation processes are disadvantageous since they are able to lead to critical peak currents, and on the other hand, an increased precision of the transducer wheel is directly linked to clearly higher costs and greater susceptibility to dirt and deformation.
It is therefore an object of the exemplary embodiments and/or exemplary methods of the present invention to provide an angular recording mechanical system which makes possible a better regulating response, even in the case of dynamic processes.
The exemplary embodiments and/or exemplary methods of the present invention make possible a clear reduction in the error that comes about from imprecisions in the transducer wheel, at the same time, the dynamics not being reduced in response to speed changes. Consequently, one may also use more cost-effective angular transducers, having a transducer wheel that is encumbered with certain manufacturing tolerances. At the same time, the exemplary embodiments and/or exemplary methods of the present invention make possible the immediate recording of actual angular velocity changes, that occur because of an acceleration of the shaft, velocity changes being recorded in full measure and indirectly. Thus, the angular velocity is able to be regulated in highly dynamic fashion, without, however, triggering undesired regulating processes that come about owing to imprecisions in the transducer wheel (and not owing to angular velocity changes).
The concept on which the exemplary embodiments and/or exemplary methods of the present invention is based is not to pass on directly the temporally discrete angular position signals, or rather the angular velocities calculated from them. In the case of deviations between two successive recording points in time (which are associated with successive angular positions), the latter are not passed on directly as a new value in the form of a stair-like step change, but, according to the present invention, an angular velocity signal curve is output which rises or drops continuously between two successive angular positions, corresponding to the sign of the angular velocity difference. Consequently, the temporally discretely recorded angular velocity is reproduced, however, not as a sequence of discontinuous curves, but as a continuously rising or falling line.
In one particular specific embodiment, the angular velocity curve does not rise to the completely newly recorded angular velocity value, but only to a portion of that, which (is positive and) less than one. This specific embodiment may be combined with a threshold value, to which angular velocity changes are compared. At a velocity change below the threshold value, the velocity change is not completely passed on but only as a portion, and above the threshold value, the velocity change is passed on directly and completely as a rising or falling slope. Because of this, at low angular velocity changes, like the ones that take place owing to imprecisions in the transducer wheel, what happens is that velocity changes that are not actually taking place, and changes produced only by the transducer wheel, for one thing, are not indicated as step changes, and for another thing, are not indicated completely for the angular velocity regulation. At actual accelerations, at which the angular velocity change is above the threshold value, it is passed on at once and directly to the regulation, so that the measured instantaneous angular velocity is output, and the regulation is able to react in an accustomed manner to the angular velocity changes.
Therefore, in the case of angular recording, a value may be selected for the threshold value which corresponds to the usual fluctuations produced by transducer wheel imprecisions. Since the imprecisions cause an angular error in a direct manner, and do not refer directly to an angular velocity (and its error), the threshold value is provided referred to an angle in a constant manner, that is, it is, for instance, normalized to an angular velocity by division by the current speed. In other words, the threshold value may decrease with increasing rotational speed, since the threshold value is used for cutting out errors in the absolute angle recording, which at high rotational velocities have a greater effect on angular velocities than at low rotational velocities. The normalization may further be carried out by multiplication with the factor normalization rotational velocity/current rotational velocity, the normalization speed being able to be freely selected and being constant. At the same time, the threshold value should take into account the dynamic requirements of the regulation, and should be below a value that corresponds to velocity step changes that require a (quick) reaction of the regulator, that is, velocity step changes whose absolute amount lets one conclude what the actual acceleration is, and which are not only explained by transducer wheel errors or transducer wheel noise. Instead of normalizing the threshold value to the rotational velocity, the recorded velocity change may also be normalized (to a normalized velocity), and a constant threshold value (or threshold values as described further on) may be used.
Instead of deciding, in the light of a threshold value, whether the one or the other of the two abovementioned operating modes is being used, a (continuous) weighting method may also be used, in which the angular velocity change, attenuated per proportional factor and linear curve, is taken into account so much the less at the output of the angular velocity signal, the greater the recorded angular velocity change is, the weighting of the classically immediately direct reproduction of the angular velocity being increased all the more, the greater the angular velocity change. Moreover, two threshold values may be used for this, in an, angular velocity change below a first threshold value, the angular velocity signal that is output, only a proportional angular velocity change having a continuous (rising or falling) curve being used, whereas, above a second threshold value, exclusively the recorded angular velocity change having an influence directly and completely on the angular velocity signal that is output.
The output angular velocity signal is then used for the regulation.
The concept, on which the exemplary embodiments and/or exemplary methods of the present invention are based, is essentially that, at least at low angular velocity changes, the angular velocity change is not directly and completely passed on, but only as a portion, and may have a continuous rising or falling curve, and not in the form of a slope, as occurs in the case of angular signals having temporally discrete, i.e. angular-discrete angle recordings. Temporally discrete angular recording here designates recording mechanisms in which corresponding signals, especially time marks, are recorded only at certain angular positions, the time marks usually being reproduced as slope characteristics between two different levels within a temporally continuous signal, so that, because of the two levels used, this type of recording is also designated as digital angular recording. It is essential, however, that the angular recording does not take place continuously, so that at each (any) point in time an angular position is output, but rather only at individual angular positions. Because of the rotational motion, since the individual points in time are clearly linked to certain angular positions, the discrete angular recording, on which the present invention is based, may be regarded as being a time-discrete and also as an angularly discrete recording.
According to the exemplary embodiments and/or exemplary methods of the present invention, time durations between two of a plurality of angular positions are recorded, the angular velocity being ascertained from the angle covered divided by the associated time duration. According to the present invention, this is carried out at regular intervals, i.e. each time a certain angle sensor position is taken up which agrees with a corresponding signal feature, such as a slope. In order to ascertain angular velocities, a first point in time and a second point in time are recorded at which the particular angle sensor positions are taken up, the angular velocity being yielded by the angle covered divided by the elapsed time. In the same way, a second angular velocity is also recorded, which may be directly after the first angular velocity, so that the second angle sensor position obtained in the recording of the first angular velocity may be used again while ascertaining the second angular velocity. To ascertain the second angular velocity, the reaching of a third angle sensor position is recorded, in this case again the respective points in time being recorded from the time duration coming about thereby and the angular difference between the second and third angular position, the ratio of the angular difference and the time duration is able to be formed.
According to the related art, the second recorded angular velocity would be passed on to the regulation directly after its ascertainment, the regulation initiating regulating measures according to this naturally discontinuous change.
However, according to the exemplary embodiments and/or exemplary methods of the present invention, the angular velocity change is recorded between the second and the first angular velocity, that is, the difference is formed by: second angular velocity minus first angular velocity. The increase in velocity, i.e. the angular velocity change, corresponds to the acceleration. As was noted above, the acceleration is able to occur because of an actual velocity increase (or velocity reduction) of the shaft, but also because of a precision error in the transducer wheel.
For this reason, according to the present invention, the second angular velocity is not output directly, for instance, to a regulation, but the output angular velocity, which corresponds to the third angular position, is output together with an artificially decreased angular velocity change, that is, as the first output angular velocity (angular velocity which was output for the previous interval, or rather, for the end of the previous interval), is added to only a portion of the angular velocity change, ascertained using the first and the second angular velocity (and not the complete angular velocity change), so that the output angular velocity coming about does not correspond to the complete second angular velocity, but only to the previously output angular velocity, inclusive of an attenuated portion of the angular velocity change. Particularly, a proportion of the angular velocity change may be zero at the point in time of the third angular position, so that at the point in time of the third angular position the previously output angular velocity, and not the second angular velocity or the previously output angular velocity is output, inclusive of the full angular velocity change. In other words, the second angular velocity is recorded, to be sure, but it is output as an output angular velocity that begins with the previously output angular velocity (=output angular velocity of the previous interval) and, starting from this, which may take into account, in a linearly increasing manner, the proportion of the angular velocity change, by having the proportion of the angular velocity change increase continuously starting from zero. The proportion of the angular velocity change for a subsequent angular interval may never be used completely, but only at a proportion of <1 for addition to the first angular velocity.
The proportion with reference to the end of the angular interval, or the increase in the proportion in the case of a linear curve according to the angular velocity change may be selected in such a way that, at the end of the angular interval, the angular velocity change is not taken into account fully, so that, towards the end of the angular interval, an angular velocity value is provided that lies between the first and the second angular velocity. The angular interval that begins with the third angular position (and thus represents the beginning of the output of the second angular velocity) ends with the recording interval that ends at the recording of a third angular velocity after the recording of the second, or at a point in time which, based on the first, second and third angular position, as well as the associated time durations, has been extrapolated as the end of the subsequent angular velocity recording interval.
Consequently, according to the exemplary embodiments and/or exemplary methods of the present invention, the angular velocity is ascertained between a first and second angular position, i.e. within a first angular interval, as well as a second angular velocity for the subsequent angular interval between the second and a third angular position. The difference coming about between the two angular velocities, that is, the angular velocity change, is output for the second angular interval, starting from the previously output angular velocity (or, in the case of strongly previously occurring normalized or not normalized angular velocity changes, starting from the previously recorded first angular velocity) having an increasing proportion (starting from zero or a low value) of the angular velocity difference, the proportion rising continuously or what may be linearly, and having a slope, for instance, at which the proportion at the beginning of a subsequent angular interval (following the second angular interval) or at the end of the current angular interval is <1, for example 0.1, 0.2, 0.3, 0.5 or 0.7. Instead of a linear increase, any curves of the proportion for the third angular interval may be selected, for instance, a proportional increase having a constant to be added (which fixes the proportion for the beginning of the angular interval), a stair-like increase having several steps, a curve that comes about from the integration of the amount of the angular velocity difference, or the like, it is ensured, however, that the rising proportion of the angular velocity change within the entire angular interval is <1, and thus the proportional angular velocity change is less than the angular velocity change itself, and then imprecisions in the transducer wheel contribute only in small measure to the determination of the angular velocity.
Alternatively, the proportion may also be <1 for only an angular interval section, the angular interval section beginning with the angular interval, but ending before the angular interval. Instead of a first proportional value and an associated slope, the first proportional value referring to the beginning of the angular interval, a second proportional value may be defined in addition, to which the first proportional value is increased rising in monotonic or strictly monotonic fashion, the second proportional value being reached at the end of the angular interval or at the end of the angular interval section. As was noted before, the first proportional value may be approximately zero, whereas the second proportional value is, for instance, approximately 30% or 40%, greater than the first proportional value and <1 (as is also the first proportional value). The proportional value corresponds to the weighting at which the angular velocity change influences the angular velocity that is output.
The proportion itself may be predefined or is a function of the amount of the angular velocity change, in order to ensure that large angular velocity changes which, from a natural point of view, do not (only) originate from imprecisions of the transducer wheel, have an influence corresponding to the output angular velocity. Furthermore, the method described above, for reducing the influence of the angular velocity change, may also be discontinued, in order to make possible a dynamic reaction on actually proceeding acceleration processes by the regulation for angular velocity changes (normalized to the rotational speed), that are greater than a threshold value. According to that, the absolute value of the velocity change may, for example, be compared to a threshold value, at an angular velocity change less than the threshold value only a proportion of the angular velocity change, having a corresponding curve perhaps, having an influence on the angular velocity that is output, whereas upon exceeding the threshold value, the only proportional influence is cancelled and instead, the full angular velocity change is directly (i.e. without a “soft transition”) included at once (i.e. abruptly) into the output angular velocity. In other words, when the angular velocity change is exceeded, instead of the composed angular velocity as described above (i.e. the first angular velocity plus a proportion of the change), the second angular velocity is output directly, that is, directly after its calculation by dividing the angular interval just covered by the appertaining time duration. The angular signal may alternatively be output as the weighted sum of the actually calculated angular velocity (second angular velocity) and the angular velocity whose dynamics have been attenuated as the output angular velocity, as described above, by transferring only a proportion of the angular velocity change. The weighting may be determined according to the amount of the angular velocity change (normalized to the rotational speed or not normalized), so that the weighting of the second original angular velocity gains by the amount of the angular velocity change, and the weighting of the composed angular velocity, i.e. the angular velocity having the angular velocity change only proportionally taken into account, is reduced by the amount of the angular velocity change. A linear model, in the form of y=c0+x*c1, may be used to calculate the weighting, y being the weighting of the actual, second angular velocity change, x representing the absolute amount of the angular velocity change, and c0 and c1 being constants. A model may be used for the weighting of the angular velocity having attenuated dynamics, according to which the two weightings (y) are constant.
Moreover, in general, to reduce unnecessary regulating measures, the curve of the proportion may be provided to be as “smooth” and continuous as possible, in which a curve is used whose derivative with respect to time for the entire angular interval is less than a predetermined threshold value, and whose differentiation with respect to time may be 0 at the beginning or the end of the angular interval section, for instance, an (approximated) arctangent function or an (approximated) cosine function shifted in the direction of the y axis (raised cosine) for 0 . . . Pi. This enables an especially soft cushioning of angular velocity changes, that originate from imprecisions of the transducer wheel. The curve of the proportion may be constructed using software, hardware or a combination thereof and may be given as a look-up table (proportion compared to angular offset within the angular interval). Besides the parameter of the angular offset within the angular interval and the associated proportion, the look-up table may also include the parameter of the amount of the angular velocity change, in order to adjust the curve to the amount of the angular velocity change. Thus, for instance, in the case of a high amount of the angular velocity change, an entry may be used which corresponds to a rapid increase in the proportion to a high proportional value, and in the case of a low amount of the angular velocity change a curve being selected according to which the proportion rises only weakly with the angular offset, and thus ends at a lower proportion. With that, angular velocity changes that are only marginal, are more greatly suppressed than angular velocity changes which are greater in amount, and which require a stronger effect on the regulation (and on the output angular velocity). Basically, a calculation and the use of a look-up table may be combined with an interpolation algorithm, so that only a small number of values within the look-up table is able to be used for a plurality of input values.
In one particularly simple specific embodiment, the output angular velocity is increased or decreased by a counter according to the angular velocity change. The counter increment corresponds to the (whole-number rounded) angular velocity change, that is, the difference of the counter values that have come about in the time recording in the first angular interval and in the second angular interval. The counter increment may be formed by the difference in the counter values divided by a (fixed) proportional factor, whereby the attenuated slope is specified, and/or divided by a recorded instantaneous rotational speed (or a value proportional to it), whereby a normalization to a normalized rotational speed is reached, so as to prevent that the angular velocity changes at high rotational speeds have a greater effect on the output angular velocity than the angular velocity changes at low rotational speeds. Furthermore, before the calculation, the angular velocity (normalized or not normalized) may be compared with a threshold value, as of which the output angular velocity corresponds to the measured (second) angular velocity, and below which the output angular velocity, as was described above, is corrected continuously upwards or downwards at each measuring interval by an increasing proportion of the angular velocity change.
All the angular intervals may lie one after the other, the first angular interval being between a first and a second angular position, the second angular interval between the second and a third angular position, and a subsequent third angular interval being between a third and a fourth angular sensor position that follows immediately thereafter. According to the present invention, after the output, according to the present invention, of the angular velocity, the assignment to the respective angular intervals shifts, so that basically, from an (N)th interval and the associated time duration, and an (N+1)th interval and the associated time duration, the angular velocity change is able to be calculated, which, according to the present invention, is taken into account only as a proportion and, at the beginning, which may have a proportion of 0 during the output of the angular velocity. In the subsequent angular interval (N+2) the angular velocity change is calculated by subtracting the angular velocity which was calculated for the (N+1)th interval, less the angular velocity which was calculated for the (N+2)th angular interval. According to the exemplary embodiments and/or exemplary methods of the present invention, for the subsequent (N+3)th angular interval, the angular velocity of the (N+2)th interval is not output, but rather the angular velocity which starts from the output of the (N+1)th interval (and the associated angular velocity), and which is changeable according to a rising proportion of the angular velocity change compared to the (N+2)th interval.
According to the exemplary embodiments and/or exemplary methods of the present invention, angular position transducers are used which include a plurality of digital sensors, each digital sensor only being able to output two levels (i.e. level 1: marking is present at the sensor, level 2: marking is not present). These sensors may be shifted by an angle corresponding to 360°/k, k being the number of sensors. In one particular specific embodiment, 3 digital sensors are used, which are respectively offset by 120° with respect to one another, the transducer wheel having teeth that are as wide as the gaps that alternate with the teeth, around the circumference. The binary signal generated by the sensors describes, by the position of the slope, the location at which the gap goes over into a tooth, or vice versa, depending on the slope direction. In order to assign the slope time, a time standard may be used, for instance, a timer or a counter (=time standard), which counts continuously and whose counter value is periodically increased at a constant frequency or at a constant clock pulse by the same amount. The counter may periodically be set back, for instance, each time a certain angular position has been reached (e.g. 0°. If a slope of one of the sensors of the angular position transducer rises or falls, the associated counter value is recorded and stored temporarily. From the difference of the counter values, because of the counter frequency or the counter clock pulse, one is able to calculate directly the associated point in time and following from that, the associated time duration.
Basically, the angular marking may, for instance, be optical or magnetic, in this case, the sensor being an optical or a magnetic sensor. The signal feature that establishes the point in time of the time recording may be a crossing at a certain threshold value, for instance, at a zero crossing.
Besides an application within an angular measuring method or an angular ascertainment method, the damping, according to the present invention, of angular velocity step changes generated by time-discrete angular recording is able to be implemented in a method for regulating the angular velocity of a motor, which may be an electric motor, for instance a direct current machine used as a vehicle drive. According to a first alternative, the regulation process itself may remain unmodified, the input size, however, that is, the measuring step of than actual value of the regulating process, being already modified according to the present invention. Consequently, the otherwise usual regulating mechanism assumes an angular velocity whose curve, according to the present invention, has already been freed of (small) angular velocity step changes by damping. According to a second alternative, the actually recorded angular velocities or the angular sensor signals are fed to the control circuit, the actual/setpoint comparison of the control circuit being modified according to the present invention.
According to this modification, within the scope of the comparison to a setpoint value, in order to record the control error and to correct the control accordingly, the actual value is processed according to the method according to the present invention. Owing to this processing, (small) angular velocity changes are not completely reconstructed but are damped, as was shown. In the latter case, the angular position sensor itself or the supply is able to remain unchanged compared to the related art, whereas the damping according to the present invention is provided within the regulating mechanism. According to the first alternative, however, the supplied angular position transducer signal is modified, so that signals that are already “damped”, that have been freed of (smaller) angular velocity step changes reach the regulating algorithm. The linearization of step changes thus takes place either within the actual/setpoint comparison of the regulation, or already within the scope of the ascertainment of the angular velocity.
Furthermore, the exemplary embodiments and/or exemplary methods of the present invention may be implemented using a recording device that is able to be connected to the angular position transducer, and to record from the latter the actually recorded angular signals. The recording device further includes computing devices as well as a time standard, to carry out the method according to the present invention, that is, to smooth out angular velocity step changes, which come about due to time-discrete angular signals, according to the present invention, and to weight angular step changes with a temporally rising proportion. The recording device also includes an output, which outputs a signal smoothed out according to the present invention, that is equivalent to the angular velocity value. Such a recording device may, for instance, be connected between an angular position transducer according to the related art and a regulating device according to the related art, this permitting a modular manner of implementation, and both angular position transducer and regulating circuit being able to remain unchanged. Thus, the modification according to the present invention takes place in a module that is interconnectable.
According to a first specific embodiment, the module itself is able to generate the output angular velocity modified according to the present invention from individual angular position transducer signals, and for this purpose, the recording device including processing units, using which the angular position transducer signals are able to be converted to angular velocities. According to a second design, the device already includes inputs for recording angular velocity values (calculated ahead of time), so that the device has only to calculate the angular velocity change, and to convert this into corresponding values having an increasing proportion part. Depending on the type of angular position transducer used (i.e. with or without preprocessing) the one or the other device may be interconnected between the angular position transducer and the regulating circuit.
Basically, an actually recorded angular velocity, an angular velocity averaged over time or an initial value, especially during starting of the motor, may be used as the output velocity value that is the basis for a subsequent output velocity value. Furthermore, it may be provided to set the (previous) output velocity value, regularly or periodically, to the instantaneously recorded angular velocity, to prevent drifting off. Moreover, as the (preceding) output velocity value, an averaging over time of a plurality of preceding output velocity values may be used.
In summary, the exemplary embodiments and/or exemplary methods of the present invention relates to a method and a device for recording angular velocity using a digital angular position transducer, for controlling an electric motor, for example. Instead of taking into account time-discrete changes directly in the form of step changes in the output signal, the recorded angular velocity change is taken into account only with an (increasing) proportion in the output. This permits a smoother curve in the case of a not completely precise transducer wheel, whose imprecisions would otherwise lead to unnecessary reactions by the regulation. Large angular velocity changes, on the other hand, are passed on directly, so as to take into account accelerations going along with them in an unaffected manner in the regulation.
Exemplary embodiments of the present invention are shown in the drawings and explained in greater detail in the following description.
a,
At time t0, a first angular velocity w0 is determined, so that in the related art (solid line) the output angular velocity immediately rises to the value w0. At time t1, a second angular velocity w1 is recorded, this also immediately and completely influencing the output angular velocity, according to the related art. Consequently, the solid line represents in each case the currently determined angular velocity, until the latter is taken over by an additional, more current angular velocity. According to the exemplary embodiments and/or exemplary methods of the present invention, if, however, at time t1 a change in the angular velocity from w0 is recorded, the change is not directly and completely passed on, but as a curve that is added to a preceding output angular velocity value, and which in increasing measure has a proportion of the angular velocity difference between the amplitude of w0 and w1. In
At time t0, a beginning initial output angular velocity value is assumed, such as a first (or zeroth), (i.e. measured ahead of time) angular velocity. However, at time t0, a more current, second angular velocity w0 is recorded, whereby the output angular velocity according to the present invention increases as of time t0 according to this change, but only proportionally. In other words, the rise between t0 and t1 reflects the velocity increase as shown by the slope at t0, however, the angular velocity change, as characterized by w0, having only a negligible effect on the output angular velocity, at the beginning of the interval t0-t1. The output angular velocity at the beginning of the interval t0-t1 is rather determined by the output speed which was output at time t0, with increasing t, as of t0, the proportion of the angular difference also increasing linearly, which refers to the angular difference at w0. For the second time interval t1-t2 the output angular velocity, which was output at time t1 is determining in the same way for the beginning of this second time interval (that is, at t1 or shortly after t1), and also in increasing measure, the curve of the output velocity between t1 and t2 being determined by the angular velocity change, which is given by the difference between w1 and w2.
The slope, dropping off at t1, of the actually measured angular velocity is thus corrected over the entire interval t1-t2, in that the angular velocity change at first does not influence the output angular velocity, and then, with increasing time lapse, is added with a linearly increasing proportion to the output angular velocity at t1. It may be seen that at time t2 the proportion of the angular velocity change is clearly less than 1, since the amplitude difference between w1 and w0 was only added in a proportion to the output angular velocity at t1, the proportional factor in
The angular velocity change between t4 and t5 (cf. slope at t5 having the angular velocity change of w5 minus w4) leads to a rise in the output angular velocity from a value at t5 (which corresponds to the output angular velocity at the end of the preceding interval), which rises to a value at t6 because the slope from t4 to t5 is added in an increasing measure to the output angular velocity at the end of interval t4-t5. Time interval t5-t6 thus reflects in increasing measure the angular velocity change given as D1 between w4 and w5.
However, at time t6 an additional angular velocity is recorded, which leads to an angular velocity change D2 (=w6-w5). According to one particular embodiment of the present invention, all the recorded angular velocity changes, which may be before setting up the output angular velocity, are compared, with respect to their amount, to a threshold value, and, as of a certain threshold value, the basis is not a previous output angular velocity and an increasing proportion of an angular velocity change, but rather the output angular velocity is directly (or only slightly delayed) set equal to the second recorded angular velocity.
On the assumption that, between t0 and t6, all fluctuations of the recorded angular velocity are to be attributed to imprecisions of the transducer wheel, it is meaningful that, for these time intervals, the output angular velocity represents the angular velocity change not completely and only proportionally. If, however, at t6 there occurs an angular velocity change which, because of its greater amount (which is greater than the amount of change in previous intervals, and is greater than a threshold value) is to be attributed to a velocity change of the shaft that is actually to be taken into account, then the output angular velocity is set equal to the newly recorded angular velocity, so that a controller starting from the output angular velocity is able to convert this change directly and undamped in control mechanisms. Because of that, for significant angular velocity changes, high dynamics remain ensured in the regulation.
One may see that all the successively recorded angular velocities differ by an amount that is small compared to the amount of D2. A threshold value lying barely below D2, that is, a threshold value that lies between D2 and (w4 minus w3), thus makes possible ending the damping according to the present invention of small angular fluctuations, and enables the reaction of the controller to large angular velocity changes. For time interval t6-t7 the damping according to the present invention is thus suspended, and the output angular velocity corresponds exactly to the difference between the two precedingly measured angular velocities. In comparison to the angular difference between w6 and w5 (and above all in comparison to a corresponding threshold value), the difference between w7 and w6 turns out to be clearly smaller, so that as of time w7, transition may occur again into the “damped” reaction mode, at which the output angular velocity (=w6), that prevailed shortly before w7, is taken as the basis, to which a proportion of the angular velocity change w7 w6, starting at 0 and increasing, is added until a maximum proportion is reached (that is less than 1). The output angular velocity that is to be provided beginning at w7 thus has the triangular shape or ramp shape as is shown by the dashed line between t0 and t6. Based on the reference to the angular velocity, the increase of the ramp before t6 and after t7 is proportional to the angular velocity change recorded in the preceding interval.
a, in a solid line, shows the angular velocity recorded and also output according to the related art, the actually output output angular velocity according to the present invention being shown by a dashed line. One may see that the angular difference at time t1 is added, first at a proportion of 0, and then increasingly up to a maximum proportion at time t2, to the preceding output angular velocity (in this case=first angular velocity).
b shows a curve of the output angular velocity, shown in a dashed line, in reaction to a rise at t1, the proportion of the angular velocity change, already at time t1 (i.e. at the beginning of the interval) not being 0, but rather corresponding to a first proportion greater than 0 and less than 1. However, in addition, the proportion increases with increasing time beginning at t1, linearly, for example, in order to reconstruct the actually recorded angular velocity change more precisely. To be sure, the incomplete damping at time t1, shown in
c shows a nonlinear proportion curve which, the same as in
The curve shown in
d shows a curve in which the proportion at time t1 is 0, however, it does not rise any more as of time t1′ but remains constant. Between time t1 and t1′, the proportion rises continuously, starting from a proportion equal to 0. Beginning at time t1, the proportion remains at a constant level greater than 0 (but less than 1). As was noted before, the output angular velocity shown by a dashed line in
| Number | Date | Country | Kind |
|---|---|---|---|
| 102008041307.0 | Aug 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP09/60336 | 8/10/2009 | WO | 00 | 4/28/2011 |
