DE102013114721A1 - Method for operating an actuator - Google Patents

Abstract

The invention describes a method for operating an actuator in which the adjustment path is limited by two end stops (Ez, Eo), the positions of the end stops (Ez, Eo) being initially determined and stored by a calibration and the positions of the end stops ( Ez, Eo) are dynamically corrected during operation if the position of the limit stops changes during operation. According to the invention, after a correction of the position of a first end stop (Ez, Eo), a further correction of the position of the first end stop (Ez, Eo) takes place only after the second end stop (Ez, Eo) has been approached at least once.

Description

The invention describes a method for operating an actuator, which can move a position object between two end stops in a desired or predetermined position.

Such actuators can be found for example in an automobile, such as for adjusting fan or radiator flaps or headlights. In addition, there are numerous other applications for such actuators.

The positions of the end stops can be predetermined or initially determined when the power supply is created. If the adjustment path and thus the position of the end stops are initially determined, the actuator is moved into the first end stop and this position is stored. Then the second end stop is approached and also this position stored. Thereafter, all intermediate positions can be calculated as a function of these end stop positions. With a fan flap, therefore, 50% open is exactly in the middle of the two end stop positions, as long as the flap position changes linearly depending on the adjustment path.

At the same time, the actuator can be braked at the end stop position even before a block detection is reached, in order to prevent damage to the actuator and / or the object on the spot. In the event that the positions of the end stops are initially determined, this can for example be done once at the first start-up of the actuator or after each restart of the actuator. However, any other configurations may be provided. If the positions of the limit stops are specified, this can be done, for example, once during the first start-up of the actuator or the values are read in again after each restart. The actuator can for this purpose have a data connection, or a programming input, so that the position values can be read. In other embodiments, it may be provided that the initial end positions are stored permanently, for example in a memory module of the engine electronics.

In an automobile and in many other applications, an actuator is subject to fluctuating environmental conditions and is often turned on and off. Due to fluctuating environmental conditions, it may happen that the positions of the end stops change during operation. This can be caused for example by mechanical deformation of the object due to temperature differences or other effects. Such a change in the end stop positions may be manifested in the manner in which an end stop is detected either earlier, ie before the expected position and within a tolerance range or too late, ie after the expected position and within the tolerance range. To ensure safe and correct operation, the position of the limit stop must be corrected. This reduces the impact of changing limit stops. For this purpose, the limit stops are permanently monitored. This means that if the actuator blocks at a position that deviates from the stored position of the end stop and is within the permitted tolerance range, then this current position is saved as a new end stop.

An actuator is often equipped with a synchronous motor or stepper motor as the drive motor. However, if the end stop is reached after a very short travel, the stepper motor may lose step. That is, the motor actually performs fewer steps than the controller has specified. Depending on the design, a stepper motor, for example, requires a certain minimum number of steps to detect a blockage at the end stop. In such a case, the detected position in the controller would not be the exact position of the end stop. If many such short travel paths occur in succession, the error of the end stop position can accumulate. Therefore, the erroneous end stop propagates in the calculation of an adjustment path of an intermediate position.

The object of the invention is therefore to provide a method of the aforementioned type in which the problems described do not occur.

This object is achieved by the method with the features mentioned in the main claim. Further features of the invention can be found in the subclaims and the description.

The trick of the invention is that after a correction of the position of a first end stop, a further correction of the position of the first end stop only takes place after at least once the second end stop has been approached. This ensures that the entire, current adjustment path is known. Preferably, a correction of the second end stop will also take place only after previously the first end stop was approached. In particular, it can be provided that the end stops each not only approached, but your position is also verified.

If the same end stop is repeatedly approached, then the position of the end stop will not be the same as in the prior art newly determined and corrected. Thus, it does not matter if steps have been lost in the meantime. The position of the end stop remains. At the same time, the own position managed by the actuator is adjusted to the position of the detected end stop, for example by scaling the displacement by means of an appropriate factor. Only when the second end stop has been approached after a correction of the position of a first end stop, can the position of the first end stop be corrected again. Depending on the application, it can happen that one or both positions are corrected only once or never.

This simple trick prevents the accumulation of position errors caused, for example, by lost steps of a stepper motor. This ensures that the positions of the end stops can be corrected during operation, if necessary due to external influences. At the same time, a correct calculation of intermediate positions is also possible because no errors are summed up.

The end stops are detected by a blockage detection, which can be realized for example by monitoring the motor current. However, it may well happen that the actuator also locks in a position that does not correspond to an end stop. Thus, in such a case, the position of an end stop is not set arbitrarily, a correction of a position in an advantageous embodiment of the invention only takes place when the new position is within a predetermined tolerance.

This means that an end stop has a nominal position. The tolerance indicates how far a corrected position may deviate from this nominal position so that it is still valid as an end stop.

If a blocking is detected that is outside of these tolerance limits, the position of the end stop will not be changed. In such a case then there is a blocking, for example, due to a defect. Based on the corrected position of the end stop, new tolerance limits can be determined. The tolerance limits may be subject to previously defined limits which restrict the tracking of the end stop positions to a permissible range.

The invention can be used in principle in all types of electric motors, especially in electronically commutated DC motors such as brushless DC motors. Likewise, the method according to the invention can also be used in stepper motors or in electric motors which have different operating modes, for example by going through a start-up phase in synchronous operation and having an operating phase with sensorless commutation. Furthermore, such an electric motor can interact with one or more gear stages. The control electronics for the end stop monitoring can be provided either by the engine electronics or by other electronics, for example by an external control unit.

The invention is explained in more detail below with reference to the accompanying drawings.

It shows:

1 FIG. 2 is a schematic view of an actuator with a nominal adjustment angle and the minimum and maximum adjustment angles. FIG.

2 : a schematic view of an actuator at the nominal setting angle with the tolerance limits of the two end stops,

3 : the schematic view of the 2 with a corrected end stop of the open position,

4 : the schematic view of the 3 additionally with a corrected end stop of the closed position,

5 : a schematic view of an actuator with the tolerance limits at the minimum setting angle,

6 : A schematic view of an actuator with the tolerance limits at the maximum adjustment angle and

7 : A schematic representation of a fan flap assembly with an actuator according to the invention.

The 7 schematically shows a fan assembly 1 with an air duct 2 and a fan door assembly 3 , The air route 2 For example, it may be a ventilation pipe or ventilation shaft, at the free end of which a fan 4 can be arranged.

The fan flap assembly 3 is at one end of the air duct 2 arranged so that it can completely close the opening. For this purpose, the fan flap assembly 3 in the example three fan flaps 5 on. The fan flap assembly 3 also has an actuator 6 for moving the fan flaps 5 on. The actuator 6 has an electric motor, a transmission and an actuating mechanism, which with the fan flaps 5 so connected that a rotation of the electric motor to a rotation of the fan doors 5 leads.

In addition to this application example many other applications are conceivable, such as radiator flaps in an automobile, which is why the invention is in no way limited to the described embodiment.

The 7a shows the fan flap assembly 3 in the closed position, in which the fan doors 5 are completely closed. This means that there is no air through the Luftleitstrecke 2 ,

The 7b shows the fan flaps 5 in a middle position. And the 7c shows the open position in which the fan doors 5 are fully open, allowing air to pass unhindered through the air duct 2 arrives.

In this example, the nominal angle of the fan flaps is 90 °, as this angle achieves the greatest possible opening.

Whether the actuator performs a rotational movement or a linear movement between the two end stops is irrelevant to the invention. Likewise, it is irrelevant whether the adjustment path, or the adjustment angle, scales linearly or differently with the rotation of the drive motor.

The 1 schematically shows an angle view of an actuating arrangement, for example, the fan assembly of 7 , The nominal closed position Z is here at 0 ° and the nominal open position O at 90 °. This results in a nominal setting angle Wn of 90 ° - 0 ° = 90 °.

The positions of the limit stops are usually calibrated when the power is turned on. For this purpose, for example, the to position Z is approached first. In this case, the position of the limit stop Ez is detected and stored via a blocking recognition. Thereafter, the open position O is approached and also detected here via a blocking detection, the position of the open-end stop Eo and stored. From the difference of the two end stop angle results in the adjustment angle W of the actuator assembly.

Depending on the application, it may be possible or advantageous if the setting angle W can deviate from the nominal setting angle Wn by a certain amount. This means that the calibration can be carried out between a minimum adjustment angle Wmin and a maximum adjustment angle Wmax. In the example, the angle variance is achieved by changing the open position O between a maximum open position Omax and a minimum open position Omin. However, it is also possible to vary the on position or both positions.

The minimum adjustment angle Wmin between the closed position Z and the open position O is here 70 ° and the maximum possible adjustment angle Wmax is 140 °. These limits are predetermined, for example, by the control or the mechanical design of the actuator or the object. The values given are given by way of example only and serve only to illustrate the invention and are in no way limiting. The minimum and maximum adjustment angles can also be chosen differently.

The positions of the center positions are also calculated from the setting angle and the end stop positions. For example, the middle position 50% open is always exactly in the middle between the two end stops. In general, however, other dependencies are possible. In particular, in the case of non-linear adjustment paths, the center position may deviate from the geometric center between the two end stops.

The calibration of the end stops and thus of the setting angle always takes place only once. However, due to thermal or other influences, it may well happen during operation that the positions of the end stops change. For example, a mechanical stop may shift in heat or the drive mechanism behaves differently. This also shifts the positions of the middle positions. It may also be necessary due to the play of gears of the actuator, which may be dependent on temperature, inter alia, that the end stops must be recalibrated to always ensure a proper start of the stops.

For this reason, it is possible according to the invention that the positions of the end stops are also corrected during operation. For this purpose, the position of the end stops is permanently monitored via a blockage detection. To ensure that the end stops do not assume nonsensical positions, corrections of the end stop positions during operation are only possible within a tolerance range. In 2 is a position of the actuator assembly of 1 shown with the tolerance range at the nominal adjustment angle Wn. The tolerance limit here is ± 12% of the calibrated adjustment angle, which corresponds to about 11 ° at 90 °. The tolerance limit can be changed as required, depending on the application. It is also possible to define asymmetrical tolerance limits or fixed values independent of the adjustment angle. In the example, the position of the limit stop Ez can therefore be in the tolerance range T between -11 ° and 11 °. Here -11 ° is an absolute lower, outer Block limit Bua over which the actuator must not be moved out. The 11 ° is a lower, inner block limit Bui, above which a block detection leads to an error. Since there must not be an end stop above the bui, a blockage here can only point to an error, such as a mechanical obstruction of the object.

If a blockage detection occurs within this range during operation, ie between Bua = -11 ° and Bui = 11 °, the end stop position can be corrected to the new value. According to the invention, however, the correction takes place only if the open end stop has been approached at least once between an already completed correction of this end stop position and the current blocking recognition.

In practice, this means, for example, when the to-position is approached that then a center position and then again closed to the position. Then, the second time approaching the closed position, no end stop correction can take place.

In a sequence such as, to position, center position, open position, closed position, the end stop could be corrected the second time start.

Similarly, a correction is made in the open position when the new end stop is between the upper, inner block limit Boi of 79 ° and the upper, outer block limit Boa of 101 °. Whereby also here the actuator must not be moved beyond the outer block limit. The actuator detects the end stop in the event of a blockage within the tolerance range between the block limits Boi and Boa. If the entire travel until it reaches the outer block limit Boa, and consequently no blockage has occurred, the actuator assumes an error. After detecting an error, various error or replacement functions can be performed. It may be provided that the Endanschlagspositionen be deleted, so that the actuator must be reinitialized. Additionally or alternatively, the start of a safety or maintenance position can be performed. For example, a flap can be adjusted back by a predetermined angle. As a result, a safety function for maintenance work or the start of a parking position can be implemented. The outer block limits are therefore preferably monitored by the controller, or by an engine electronics, and only approached if no end stop position has been detected. Blocking before reaching the inner block limit Boi will also result in an error. As in the case of the closed position, a correction can only be made according to the invention if the to position has been approached at least once between two approaches to the open position. In particular, it may be provided that the closed position is not only approached but also verified.

At the in 3 shown position in the open position O the open end stop Eo was recognized only at 95 °. This position is within the tolerance range, which is why this position is stored as the new end stop position O with respect to the old end stop positions Oa. The limit stop Ez remains at 0 °. The setting angle W thereby increases by 5 ° to 95 ° - 0 ° = 95 ° in comparison to the nominal setting angle Wn.

The tolerance limit changes to 12% of 95 °, which corresponds to about 12 °.

This means that a new end stop position between Boi = 83 ° and Boa = 107 ° may be.

According to the invention, however, no renewed correction of the open position takes place as long as the closed position has not been approached at least once.

In 4 was now detected in the closed position Z of the limit stop Ez already at 5 °, which is why here now the end stop position has been corrected to this 5 °. As a result, the setting angle W changes to 95 ° - 5 ° = 90 °, whereby the tolerance limit changes again to 12% of 90 °, ie to 11 °. The limit stops Ez can now be between Bua = -6 ° and Bui = 16 ° and the open end stops Eo between Boi = 84 ° and Boa = 106 °.

Because the tolerance range is always calculated from the tolerance limit and the current setting angle, the end stop position can in principle assume any desired values. Here, however, form the in 1 shown absolute minimum Wmin and maximum adjustment angle Wmax a limit. The 5 therefore shows the limiting case with minimal adjustment angle Wmin. The tolerance limits are here at 12% of 70 °, ie about 8 °. The closed end stop Ez can therefore lie in the example shown between Bua = -8 ° and Bui = 8 °, the open end stop between Boi = 62 ° and Boa = 78 °.

The 6 shows the other extreme case with maximum adjustment angle. The tolerance limit here is 12% of 140 °, ie about 17 °. The closed end stop can therefore be in the example shown between Bua = -17 ° and Bui = 17 °, the open end stop between Boi = 123 ° and Boa = 157 °.

In an alternative embodiment of the invention, the tolerance limits are not changed. This means that the end stop positions must always be within the same tolerance range. In practice, the tolerance range would then be calculated once from the nominal setting angle and not from the current setting angle. In the example of 3 this would mean that despite the correction of the open position to 95 °, the tolerance range is still between 89 ° and 101 °. As a result, a gradual drift of the end stop can be prevented.

LIST OF REFERENCE NUMBERS

1

 fan arrangement

2

 Luftleitstrecke

3

 Fan flap assembly

4

 Fan

5

 louvers

6

 actuator

W

 setting angle

Wn

 nominal setting angle

Wmin

 minimum adjustment angle

Wmax

 maximum adjustment angle

Z

 To position

ez

 To-end stop

O

 Open position (current, corrected)

Oa

 old open position

eo

 Open-end stop

Bua

 lower, outer block limit

Bui

 lower, inner block limit

Boi

 upper, inner block limit

boa

 Upper, outer block limit

T

 tolerance

Claims (12)

Method for operating an actuator, in which the adjustment path is limited by two end stops (Ez, Eo), wherein the positions of the end stops (Ez, Eo) are dynamically corrected during operation, if the position of the end stops changes during operation, characterized in that, after a correction of the position of a first end stop (Ez, Eo), a further correction of the position of the first end stop (Ez, Eo) takes place only after the second end stop (Ez, Eo) has been approached at least once. A method according to claim 1, characterized in that each time an end stop, the position of the respective end stop is verified and / or changed if necessary. A method according to claim 1 or 2, characterized in that the positions of the end stops (Ez, Eo) are initially determined by a calibration and stored. A method according to claim 1 or 2, characterized in that the initial position of the end stops (Ez, Eo) is fixed. Method according to one of claims 1 to 4, characterized in that a correction of the position of an end stop only takes place when the new position is within a predetermined tolerance range (T). A method according to claim 5, characterized in that the tolerance range (T) is determined as a function of the nominal setting angle (Wn) and a predetermined tolerance limit. A method according to claim 5, characterized in that the tolerance range (T) in each case depending on the current setting angle (W) and a predetermined tolerance limit is redetermined. A method according to claim 5, characterized in that the tolerance range (T) is fixed. Method according to one of claims 5 to 8, characterized in that the tolerance range (T) is in the range between 4% and 20% of the maximum adjustment angle. Method according to one of the preceding claims, characterized in that a correction of the second end stop (Ez, Eo) takes place only after previously the first end stop (Ez, Eo) was approached. Method according to one of the preceding claims, characterized in that the actuator comprises an electronically commutated electric motor. A method according to claim 11, characterized in that the reaching of the first end stop (Ez, Eo) and / or the second end stop (Ez, Eo) is detected by means of a monitoring of the motor current.

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