EP1817487B1 - Method and device for triggering an actuator - Google Patents

Description

State of the art

The invention is based on a method and a device for driving an actuator according to the preamble of the independent claims.

From the DE4303560A1 a method and a device for controlling an adjusting device is known in which in the region of a mechanical stop of the adjusting device, a limitation of the current flowing through the electric motor current, which actuates the adjusting takes place.

From the EP0992662A2 a throttle device for an internal combustion engine is known. A minimum opening degree of the throttle valve is set to a value larger than an amount that results in the overshoot of the throttle valve when the opening degree of the throttle valve is changed from a maximum opening degree to the minimum opening degree.

From the US2003 / 084873A1 For example, an electronic throttle control device is known. A microcomputer calculates a deviation between a target opening degree and an actual opening degree. Depending on this, an engine control amount and a control gain are calculated. The control gain is chosen to be smaller with increasing control deviation. The control gain is limited by the previous control gain if the control gain is greater than the previous control gain. The restriction on the control gain is canceled when the calculated current opening degree change is reduced from a predetermined value.

For electrically controlled actuators in a motor vehicle, such as a throttle, a charge movement flap, an exhaust gas recirculation valve, a bypass valve for a compressor, etc., is often used to control a digital control in an engine control unit. In order to avoid damage to the corresponding actuator, it must be prevented that a mechanical stop of the corresponding actuator is approached too fast. To ensure this, an offset is often introduced to the stop so that the actuator can be driven quickly up to this offset. However, this offset causes an increased leakage mass flow. An alternative solution uses a setpoint change limitation, for example, using a filter. In this case, a change in the setpoint value for the position of the actuator is limited to a predetermined desired value according to the setpoint change limit. The setpoint change is limited to such a low value that it can be ensured that the stop is not approached too quickly by the actuator. If this setpoint change limit is active over the entire range of predefinable setpoint values for the position of the actuator, this leads to the fact that the control of the position of the actuator to the corresponding predetermined setpoint is unnecessarily slow. An improved solution is to turn on this slow setpoint limit only when the preset setpoint between the stop and a predetermined threshold associated with the stop.

Object of the invention

The method and the device according to the invention the task is based on optimizing the control of an actuator.

Advantages of the invention

The inventive method and the inventive apparatus for driving an actuator with the features of the independent claims have the advantage over that to achieve the first setpoint by the setpoint initially a second setpoint is specified, that a change in the setpoint for the position of the actuator the second setpoint value is limited according to a second setpoint change limit, and that if the change in the setpoint value to the first setpoint limit with the first setpoint change limit is greater than the change of the setpoint value to the second setpoint limit with the second setpoint change limit, the first setpoint value is predetermined for the setpoint value is and the change of the setpoint for the position of the actuator is limited to the first set value according to the first setpoint change limit. In this way, a two-stage setpoint change limitation can be carried out especially for a first set value in the vicinity of a stop of the actuator. In this case, the setpoint value is first moved with the second setpoint change limitation in the direction of the second predetermined setpoint value and then with the first setpoint change limitation in the direction of the first predetermined setpoint value. In this case, the approach of the setpoint in the direction of the second predetermined setpoint value with a larger setpoint change and thus faster can be allowed, as the subsequent approach of the setpoint in the direction of the first predetermined setpoint. The second setpoint change limit is then lower or lower than the first setpoint change limit. Thus, even in the event that the first predetermined threshold is in the vicinity of the stop, the setpoint could be changed comparatively quickly towards the first predetermined desired value within a certain range limited by the second predetermined setpoint value. The comparatively slow setpoint change limitation is then only required on the last stretch of the setpoint to the first predetermined setpoint. Thus, the control for adjusting the actuator is not unnecessarily slowed down.

The measures listed in the dependent claims advantageous refinements and improvements of the main claim method are possible.

It is particularly advantageous if the first and the second setpoint change limitation are only performed when the first setpoint lies between a stop of the actuator and a predetermined threshold value associated with the stop. In this way, with a suitable choice of the threshold, a first predetermined setpoint, which is not close to the attack, that is not between the stop and the stop associated with the predetermined threshold value, approach with the highest possible speed of the actuator, without damaging the actuator by the attack would be feared. If, on the other hand, the first desired value lies between the stop and the predetermined threshold value associated with the stop, it is further ensured that the first desired value is approached as quickly as possible and then slowly enough due to the two-step setpoint change limitation in order to prevent the actuator from being damaged by a stop prevent.

It is particularly easy to select the second predetermined setpoint equal to the predetermined threshold.

The two-stage setpoint limit limitation is particularly advantageous for preventing damage to the actuator by the stop when, as described, the second setpoint change limit is selected to be weaker than the first setpoint change limit.

A simple realization for the setpoint change limiting results when the setpoint for the first setpoint change limiting is filtered with a first time constant and when the setpoint for the second setpoint change limiting is filtered with a second time constant.

In this case, advantageously, the first time constant greater than the second time constant can be selected to achieve that the second setpoint change limit is weaker than the first setpoint change limit.

It is advantageous if one of the two Solländerungsbegenzungen is performed by means of a ramp function and the other of the two Solländerungsbegenzungen by filtering. This is particularly beneficial in systems where an asymptotic Approaching the stop position is too slow. Another advantage is that with this method, the speed at which the target value of the actuator may approach the stop, can be specified directly.

It is furthermore particularly advantageous if the second desired value is selected further apart from a stop of the actuator than the first desired value. In this way, the described advantage can be realized, according to which the desired value can first be guided as fast as possible towards the second setpoint by the two-stage setpoint change limit, in order then to guide the setpoint as slowly as possible to the first predetermined setpoint, which is closer to the setpoint Damage to the actuator by the stop to avoid.

drawing

An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description. Show it FIG. 1 a roughly schematic section of an internal combustion engine, FIG. 2 a functional diagram for explaining the method and apparatus of the invention and FIG. 3 a diagram with different setpoint curves for the position of an actuator over time.

Description of the embodiment

In FIG. 1 110 indicates a section of an internal combustion engine that drives, for example, a vehicle. The internal combustion engine can be designed, for example, as a gasoline engine or as a diesel engine. About an intake passage 40 of the engine fresh air is supplied. In the intake passage 40, an actuator 1 is arranged. The actuator 1 is formed for example as a throttle valve. Depending on the position of the throttle valve 1, a different air mass flow in the intake passage 40 is set. A lower stop of the throttle valve 1 in the intake passage 40 is in FIG. 1 designated by the reference numeral 45. Furthermore, in FIG. 1 a first setpoint value 5 for the position of the throttle flap 1 and a second setpoint value 10 for the position of the throttle flap 1 are shown by dashed lines, wherein the first setpoint value 5 is closer to the lower stop 45 than the second setpoint value 10. The throttle flap 1 is known in the art Way controlled by a drive signal AS by a controller 50, for example, to implement a driver's request. The drive signal AS may be, for example, a pulse-width-modulated signal, wherein different positions of the actuator 1 in the intake passage 40 result for different duty cycles of the pulse-width-modulated drive signal AS.

In FIG. 3 Now the position of the throttle valve 1 is plotted against the time t in seconds. The position of the throttle valve 1 is given in percent of the opening degree. The value 0% corresponds to the state of the fully closed throttle valve 1, that is, the throttle valve 1 is located directly on the lower stop 45. The value 100% for the position of the throttle valve 1 corresponds to the fully open throttle 1. With "target 1" is a first setpoint for the position of the throttle valve 1 in FIG. 3 shown. This first desired value Soll1 for the position of the throttle valve 1 is initially at the value 100% for the fully open throttle 1. Approximately at the time of one second, the first target value 1 jumps from 100% down to about 1.01 seconds to reach the value 0%. There remains the first setpoint Soll 1 to at least 1.35 seconds. Thus, the first target value Soll 1 corresponds approximately to the lower stop 45 from the time 1.01 seconds FIG. 1 does not directly correspond to the first setpoint indicated there 5 the lower stop 45, but is given close to the fence. In general, it should be assumed that the first set point 5 indicates a position of the throttle flap 1 in the vicinity of the lower stop 45, wherein as in FIG. 3 the special case may occur that the first setpoint 5, in FIG. 3 denoted by 1, after the in FIG. 3 shown jump directly to the lower stop 45 and thus the fully closed throttle valve 1 corresponds. In this case, all those first setpoint values 5 are designated as being close to the stop, which are located closer to the lower stop 45 after the jump than a predefined threshold value SW. The predetermined threshold SW can be suitably applied, for example, on a test bench. In this case, the predetermined threshold value SW can be applied, for example, in such a way that all the first setpoint values 5 are so close to the lower limit stop 45 below the predetermined threshold value SW that they may not be preset abruptly but with a sufficient setpoint change limitation in order to damage the throttle flap 1 to safely avoid the bottom stop 45. In the present example FIG. 3 For example, the predetermined threshold SW becomes a value between 9 and 10 Percentage of the position of the throttle valve 1 applied. Since the first target value Soll 1 after the jump is below the predetermined threshold SW, it must not be as in FIG. 3 represented jump-shaped but only with the consideration of a first setpoint change limit be specified. Such a setpoint change limitation is achieved, for example, with the aid of low-pass filtering. Thus, the change of the setpoint value for the position of the throttle valve 1 from the value 100% to the value 0% is limited by low-pass filtering with a predetermined time constant. The reference numeral 115 shows a first course of the setpoint value for the position of the throttle flap 1, which is achieved by low-pass filtering the profile of the first setpoint value 1 with a second time constant of 35 ms. Although this leads to a comparatively rapid adjustment of the setpoint value of the throttle valve 1 to the first predetermined setpoint value 1, but is in particular from falling below the predetermined threshold SW until reaching the first predetermined threshold value 1 too fast to the throttle valve 1 safe from damage by the lower stop 45 to preserve. By the reference numeral 120, a second possible course of the setpoint is shown, which is formed by low-pass filtering the course of the first predetermined setpoint value 1 with a first time constant of 70 ms. Although the setpoint curve formed thereby is in particular below the predetermined threshold SW until reaching the first predetermined setpoint value 1 sufficiently slow to safely avoid damaging the throttle valve 1 when hitting the lower stop 45, but starting from the position 100% to to reach the predetermined threshold SW too slow.

According to the invention, it is now provided to find a compromise between two different desired value curves, which, on the one hand, approaches the target value of the first predetermined desired value 1 as quickly as possible, starting from the fully opened throttle valve 1 until reaching the predetermined threshold value SW. At the latest then, when the predetermined threshold SW is exceeded by the setpoint curve, the first predetermined target value 1 should then be reached so slowly from the setpoint that damage to the throttle valve 1 is reliably avoided by the lower stop 45. It is therefore important, for example, to find a compromise between the first setpoint course 115 and the second setpoint course 120, wherein the first setpoint course 115 above the predetermined threshold SW and the second setpoint course 120 at the latest below the predetermined threshold SW of interest is. For this purpose, the invention provides a two-stage setpoint change limitation. In a first stage, a second predetermined target value 2 is selected as the target value to be set for the position of the throttle valve 1 after the setpoint jump, which may, for example, correspond to the predefined threshold value SW or greater than this. Since the predetermined threshold SW, for example, can be applied to a test stand so suitable that only for jumps of the first predetermined setpoint value 1 below the predetermined threshold SW a corresponding setpoint change limit for a damage-free adjustment of the position of the throttle valve 1 to the first predetermined setpoint desired 1 sure is set, it is particularly advantageous to select the second predetermined target value 2 equal to the predetermined threshold SW. In general, the selection of the second predetermined setpoint Soll2, the in FIG. 1 is also characterized by the reference numeral 10, that this is further spaced from the lower stop 45 of the actuator 1 is selected as the first predetermined target value Soll1.

This is in FIG. 3 exemplified. Until the second predetermined setpoint value 2 is reached, a comparatively fast setpoint course can be selected. At the latest when falling below the predetermined threshold SW by the setpoint curve can then be switched to a sufficiently slow setpoint course. Such an ideal setpoint course is identified by reference numeral 130. It is assumed that in a first stage of the setpoint adjustment of the setpoint jump takes place at the time of one second only up to the second predetermined setpoint setpoint 2, in the present example up to the predetermined threshold value SW. This jump to the predetermined second target value Soll 2 is then low-pass filtered with the second time constant of 35 ms in this example, so that the second target value set 2 as fast as possible according to an in FIG. 3 is approximated with the reference numeral 125 marked third setpoint course. As soon as the amount of change in the setpoint value of, for example, the second setpoint curve 120 calculated in parallel with the first time constant 70 ms becomes greater than the amount of change in the third setpoint course 125, the setpoint profile is continued by low-pass filtering of the first predetermined setpoint value 1 with the first time constant 70 ms , In this way, the ideal setpoint course 130 results, which initially approaches the second predetermined setpoint value 2 as quickly as possible and then reaches the first setpoint setpoint 1 sufficiently slowly enough, to safely protect the throttle valve 1 from damage by the lower stop 45.

Dieser Quotient ist in Figur 2 mit Q1 bezeichnet. Er wird einem ersten Eingang eines ersten Vergleichsgliedes 75 zugeführt, dessen zweitem Eingang der Wert Null zugeführt wird. Ist der erste Quotient Q1 kleiner als null, so wird der Ausgang des ersten Vergleichsgliedes 75 gesetzt, andernfalls wird er zurückgesetzt. Der Ausgang des ersten Vergleichsgliedes 75 ist auf ein Inversionsglied 85 geführt, dessen Ausgang gesetzt ist, wenn dessen Eingang zurück gesetzt ist und dessen Ausgang zurück gesetzt ist, wenn dessen Eingang gesetzt ist. Der Ausgang des Inversionsgliedes 85 ist einem ersten Eingang eines Oder-Gliedes 90 zugeführt. Der Ausgang des ersten Vergleichsgliedes 75 ist außerdem eines ersten Eingang eines Und-Gliedes 80 zugeführt. Der erste Quotient Q1 als Ausgang des ersten Divisionsgliedes 65 ist außerdem einem ersten Eingang eines zweiten Vergleichsgliedes 35 zugeführt. Zweite Vorgabemittel 25 geben den zweiten Sollwert Soll2 in diesem Beispiel als vorgegebenen Schwellwert SW vor. Die zweiten Vorgabemittel 25 können beispielsweise durch einen der Steuerung 50 zugeordneten Speicher gebildet sein, in dem der für den vorgegebenen Schwellwert SW beispielsweise am Prüfstand applizierte Wert abgelegt ist. In einem zweiten Subtraktionsglied 60 wird für jeden Abtastzeitpunkt der für diesen Abtastzeitpunkt vorliegende gefilterte Sollwert Sollfil vom für diesen Abtastzeitpunkt vorliegenden vorgegebenen zweiten Sollwert Soll2 abgezogen, so dass sich am Ausgang des zweiten Subtraktionsgliedes 60 die Differenz Soll2-Sollfil bildet. Der Ausgang des zweiten Subtraktionsgliedes 60 wird in einem zweiten Divisionsglied 70 durch eine zweite Zeitkonstante Z2 dividiert, die in diesem Beispiel den Wert 35 ms wie zuvor beschrieben einnehmen kann und die ebenfalls in einem der Steuerung 50 zugeordneten Speicher abgelegt sein kann. Somit ergibt sich am Ausgang des zweiten Divisionsghedes 70 ein zweiter Quotient $\mathrm{Q}2=\frac{\mathit{Soll}2-\mathit{Sollfil}}{Z2}\mathrm{.}$

In FIG. 2 a functional diagram is shown, which explains the inventive method and the device according to the invention in more detail. The functional diagram is denoted by the reference numeral 15 in FIG FIG. 2 and can be implemented as a device according to the invention software and / or hardware in the controller 50. The sequence of the method according to the invention will be clarified on the basis of the functional diagram 15. First presetting means 20 indicate, in a manner known to the person skilled in the art, the first setpoint value 1 or the time profile of the first setpoint value 1, for example according to FIG FIG. 3 and, for example, depending on a driver's request. Furthermore, a low-pass filter 30 is provided, which emits a filtered nominal value Sollfil at regular sampling instants. At each sampling time, the filtered desired value Sollfil present at this sampling time is subtracted from the first predetermined desired value Soll 1 present at this sampling instant in a first subtraction element 55. The formed difference Soll1 - Sollfil at the output of the first subtraction element 55 is divided in a subsequent first division member 65 by a first predetermined time constant Z1, which may be stored permanently in a memory 50 associated memory. For example, as described above, the value of 70 ms can be selected for the first predetermined time constant Z1. The output of the first division element 65 thus corresponds to the quotient $\frac{\mathit{Should}1-\mathit{Sollfil}}{Z1}\mathrm{,}$

This quotient is in FIG. 2 labeled Q1. It is supplied to a first input of a first comparison element 75, whose second input is supplied with the value zero. If the first quotient Q1 is less than zero, the output of the first comparison element 75 is set, otherwise it is reset. The output of the first comparator 75 is fed to an inverse 85 whose output is set when its input is reset and its output is reset when its input is set. The output of the inversion member 85 is supplied to a first input of an OR gate 90. The output of the first comparison element 75 is also supplied to a first input of an AND gate 80. The first quotient Q1 as the output of the first division element 65 is also fed to a first input of a second comparison element 35. Second presetting means 25 predetermine the second desired value Soll2 in this example as a predetermined threshold value SW. The second Default means 25 may be formed, for example, by a memory 50 associated memory in which the value applied to the predetermined threshold SW, for example, applied to the test bench value. In a second subtraction element 60, the filtered desired value Sollfil present for this sampling instant is subtracted from the predetermined second nominal value Soll2 present for this sampling instant for each sampling instant, so that the difference Soll2-Sollfil forms at the output of the second subtraction element 60. The output of the second subtraction element 60 is divided in a second division element 70 by a second time constant Z2, which in this example can assume the value 35 ms as described above and which can also be stored in a memory associated with the controller 50. This results in a second quotient at the output of the second division ghetto 70 $\mathrm{Q}2=\frac{\mathit{Should}2-\mathit{Sollfil}}{Z2}\mathrm{,}$

The second quotient Q2 is supplied to a second input of the second comparison element 35. The output of the second comparator 35 is set when Q1 <Q2. The output of the second comparator 35 is supplied to a second input of the AND gate 80. The output of the AND gate 80 is set only when its two inputs are set, otherwise it is reset. The output of the AND gate 80 is on the one hand to a second input of the OR gate 90 and on the other hand fed as a control signal to a first controlled switch 100. The output of the OR gate 90 is set when one of its two inputs is set, and otherwise reset. The output of the OR gate 90 is guided as a control signal to a second controlled switch 105. The first desired value Soll 1 is supplied on the one hand to a first input of a maximum selector element 95 and on the other hand to a first input of the second controlled switch 105. The second desired value Soll2 is supplied to a second input of the Maoimalauswahlgliedes 95. The maximum selector element 95 selects the maximum of its two inputs, that is to say the maximum from the first preset desired value Soll 1 and the second predetermined nominal value Soll 2, and outputs this maximum to a second input of the controlled switch 105. The second controlled switch 105 connects the output of the maximum selector 95 to an input of the low pass 30 when the output of the OR gate 90 is reset. Otherwise, the second controlled switch 105 connects the input of the low-pass filter 30 with the first default means 20 and thus with the first predetermined desired value Soll1. The output of the first controlled switch 100 predefines the time constant for the low pass 30. In this case, the first controlled switch 100 connects the memory with the first predetermined Time constant Z1 with the input for the time constant of the low-pass filter 30 when the output of the AND gate 80 is set, otherwise the first controlled switch connects the memory with the second predetermined time constant Z2 with the time constant input of the low pass 30th

The low-pass filter 30 then filters the output of the second controlled switch 105 with the respectively set time constant in order to form the filtered nominal value Sollfil. By the first comparison member 75 ensures that the two-stage setpoint change limit is only performed when the first setpoint desired 1 is smaller than the filtered setpoint Sollfil, and thus the filtered setpoint Sollfil a time-decreasing course and thus toward the lower stop 45th having. Otherwise, only the first setpoint Soll1 is filtered by the low-pass filter 30 with the second predetermined time constant Z2. With the first comparison element 75 is thus checked whether the throttle valve 1 moves in the closing direction, ie in the direction of the lower stop 45, that is, the filtered target value Sollfil changed in the direction of the lower stop 45. With the second comparison element 35 it is checked which of the two setpoint change limits allows the largest step in the direction of the lower stop 45. In this case, the setpoint change determination is always selected which allows the larger step in the direction of the lower limit stop 45 and configures the low-pass filter 30 accordingly in the manner described. If the low-pass filter 30 with the first setpoint setpoint 1 as the input value and the slower first time constant Z1 makes a larger step toward the bottomstop 45 than the low-pass filter 30 with the second setpoint setpoint Soll2 as the input value and the faster first filter time constant Z2, then the former Configuration with the first predetermined setpoint Soll 1 and the first filter time constant Z1 selected, otherwise the filter configuration with the second predetermined setpoint Soll2 is greater than the first predetermined setpoint Soll1, and the second predetermined time constant Z2.

As long as the first predetermined setpoint Soll1 is greater than the predetermined threshold SW, it is filtered with the faster second time constant Z2, so that the setpoint approaches the first predetermined setpoint Soll1 as quickly as possible. If the first predetermined setpoint value 1 then falls below the predetermined threshold value SW, the method according to the invention takes effect according to FIG FIG. 2 , so that's the second one predetermined setpoint Sol12 with the faster second time constant Z2 is approached by the low-pass filter 30 until the filtered setpoint curve is slowed down so much that the filtering with the slower first time constant Z1 and the first predetermined setpoint Soll11 is faster than the input value. Then, as described, the switching between the two different input values and the two different time constants takes place, and the first predetermined desired value Soll1 is then approached with the slower first filter time constant Z1.

In this way, a setpoint change limit can be smoothly switched over from a high-speed tracking to a slower tracking-near tracking of the setpoint to the corresponding predetermined setpoint if the first predetermined setpoint Soll1 is below the predetermined threshold SW. As long as the first predetermined setpoint Soll1 is in the range above the predetermined threshold SW or if it moves in the direction of the range above the predetermined threshold SW, slight overshoot or undershoot in the setpoint are allowed because they reach a faster reaching the first predetermined setpoint value 1 lead.

The function diagram according to FIG. 2 finally represents a controller for tracking the setpoint value for the position of the throttle valve 1 to the first predetermined desired value Soll1. The by the function diagram FIG. 2 In comparison with systems which only work with the first filter time constant Z1, as soon as the first predetermined desired value Soll1 is below the predetermined threshold value SW, the controller realized has the advantage that the controller according to the functional diagram FIG. 2 can be designed with a higher loop gain.

The third setpoint course 125 shows the fastest possible approach of the setpoint value to the predetermined threshold value SW at which occurring undershoots in the setpoint course can still be controlled. The ideal setpoint course 130 uses this fast third setpoint course 125 until it decelerates too much. Subsequently, the ideal setpoint course 130 continues slowly in the direction of the first preset setpoint Soll1. If the first setpoint course 115 had been used until reaching the predetermined threshold value SW and then switched directly to the second time course 120 with the slower time constant, then the rate of change of the setpoint value in the range of the predefined threshold value SW would have been too high.

With the aid of the method according to the invention and the device according to the invention, it is thus possible to select such a fast second filter time constant Z 2 for the low-pass filter 30 that in the region of the setpoint value above the predetermined threshold value SW the controller according to the functional diagram of FIG FIG. 2 speed optimized. Nevertheless, the mechanical lower stop 45 is then approached so slowly after switching to the first filter time constant Z1 that the throttle valve 1 is not damaged. The throttle valve 1 can thus be completely closed in order to minimize the leakage air.

An alternative realization results when first the setpoint for the second setpoint change limiting with a fast d. H. as small a second time constant is filtered and then the first setpoint change limit for the setpoint is implemented as a ramp function. This is particularly advantageous in systems where asymptotic approach to the stop position is too slow. Another advantage is that with this method, the speed at which the target value of the actuator may approach the stop, can be specified directly. Conversely, the second setpoint change limitation for the setpoint value can first be implemented as a ramp function, and the setpoint value can then be filtered for the first setpoint change limitation with the first time constant.

The embodiment has been described above with reference to an actuator 1 designed as a throttle valve. The invention can be applied in a corresponding manner to any electrically controlled actuators, for example, to a charge movement flap, an exhaust gas recirculation valve, a bypass valve for a compressor, etc. Furthermore, the application of the actuator 1 to an internal combustion engine or a motor vehicle is not limited, but can be provided for any applications in which a mass flow can be influenced by changing the position of an actuator.

In the foregoing, low pass filtering with different filter time constants was used to differentially limit the change of the setpoint. However, the invention is not limited to the use of filtering for the setpoint change limiting. A setpoint change limit can also be calculated by calculating a gradient the temporal setpoint course and its comparison with a predetermined limit occur. If the preset limit value is less than the specified limit value, no setpoint change limitation takes place, otherwise the setpoint change is limited to the specified limit value. Different setpoint change limitation can then be realized by different limit values in a corresponding manner. Other methods known to those skilled in the setpoint limit limiting can be used to implement the invention in a corresponding manner.

Two different preset limit values can be used to realize two different setpoint change limits, one weaker than the other. A weaker setpoint change limitation results from the larger preset limit value for the setpoint change limitation. In this case, a larger setpoint change amount is possible. The limitation of the setpoint change is thus lower.

According to the invention, it may be provided that the first and the second setpoint change limitation, in the example described above, the low-pass filtering with the first and the second predetermined filter time constant is performed only if the first predetermined setpoint Soll 1 between the lower stop 45 of the actuator 1 and the predetermined limit SW associated with the lower stop 45 is located. In this case, the first predetermined target value 1 can also be the lower stop 45 as in FIG. 3 represented correspond. If the first predetermined desired value Soll 1 is above the predetermined threshold value SW, it is also possible to dispense with a setpoint change limitation or filtering. The same applies if the first predetermined desired value Soll1 corresponds to the predetermined threshold value SW. In this case, however, as in FIG. 3 shown the low-pass filtering with a single filter time constant according to the third setpoint curve 125 are performed. In the example below FIG. 3 In this case, the second filter time constant Z2 = 35 ms has been selected.

In the example described above, the lower stop 45 of the control member 1 was considered. In a correspondingly mirrored manner, the described method according to the invention and the described device according to the invention can also be applied to the upper stop of the actuator 1, in which case the output of the first comparison element 75 is set when Q1 is greater than zero and the output of the first comparator 75 is otherwise reset. Furthermore, in this case, the output of the second comparator 35 is set when Q1> Q2 and otherwise the output of the second comparator 35 is reset. From the maximum selector 95 in FIG FIG. 2 becomes a minimum selector in this case. Incidentally, the functional diagram can be after FIG. 2 also use for this case of the upper stop. In this case, the predetermined threshold SW for the upper stop, for example, between 90 and 91 percent of the position of the actuator 1 according FIG. 3 and the upper stop corresponds to the position 100 percent of the actuator 1. Again, the second predetermined setpoint Soll2 can be selected equal to the predetermined threshold.

Claims (9)

1. Method for triggering an actuator (1) having a setpoint value profile for setting the actuator (1) to a first setpoint value (5),
   wherein the setpoint value profile for setting the actuator (1) to the first setpoint value (5) is limited in accordance with a first setpoint value change limitation,
   characterized
   in that, in order to obtain the first setpoint value (5) by means of the setpoint value profile, a second setpoint value (10) is firstly predefined,
   in that the setpoint value profile for setting the actuator (1) is limited to the second setpoint value (10) in accordance with a second setpoint value change limitation, and
   in that, when the change in the setpoint value profile with respect to the first setpoint value (5) with the first setpoint value change limitation would be larger in absolute terms than the change in the setpoint value profile with respect to the second setpoint value (10) with the second setpoint value change limitation, the first setpoint value (5) is predefined for the setpoint value profile, and the setpoint value profile for setting the actuator (1) is limited to the first setpoint value (5) in accordance with the first setpoint value change limitation.
2. Method according to Claim 1, characterized in that the first and second setpoint value change limitations are carried out only when the first setpoint value (5) is between a stop (45) of the actuator (1) and a predefined threshold value assigned to the stop (45).
3. Method according to Claim 2, characterized in that the second predefined setpoint value (10) is selected to be equal to the predefined threshold value.
4. Method according to one of the preceding claims, characterized in that the second setpoint value change limitation is selected to be weaker than the first setpoint value change limitation.
5. Method according to one of the preceding claims, characterized in that the change in the setpoint value profile for the first setpoint value change limitation is filtered with a first time constant, and in that the change in the setpoint value profile for the second setpoint value change limitation is filtered with a second time constant.
6. Method according to Claim 5, characterized in that the first time constant is selected to be larger than the second time constant.
7. Method according to one of Claims 1 to 4, characterized in that one of the two setpoint value change limitations is carried out by means of a ramp function, and the other of the two setpoint value change limitations is carried out by means of filtering.
8. Method according to one of the preceding claims, characterized in that the second setpoint value (10) is selected to be at a further distance from a stop (45) of the actuator (1) than the first setpoint value (5).
9. Device (15) for triggering an actuator (1) having a setpoint value profile for setting the actuator (1),
   wherein first predefining means (20) are provided for predefining a first setpoint value (5) for the setpoint value profile for setting the actuator (1),
   wherein first limiting means (30) are provided for limiting a change in the setpoint value profile for setting the actuator (1) to the first setpoint value (5) in accordance with a first setpoint value change limitation,
   characterized
   in that second predefining means (25) are provided which, in order to obtain the first setpoint value (5) by means of the setpoint value profile, firstly predefine a second setpoint value (10),
   in that second limiting means (30) are provided for limiting a change in the setpoint value profile for setting the actuator (1) to the second setpoint value (10) in accordance with a second setpoint value change limitation,
   in that checking means (35) are provided which check whether the change in the setpoint value profile with respect to the first setpoint value (5) with the first setpoint value change limitation would be larger in absolute terms than the change in the setpoint value profile with respect to the second setpoint value (10) with the second setpoint value change limitation, and in that in this case the first predefining means (20) predefine the first setpoint value (5) for the setpoint value profile, and the first limiting means (30) limit the change in the setpoint value profile for setting the actuator (1) to the first setpoint value (5) in accordance with the first setpoint value change limitation.

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