DE102005060022A1 - Method for determining an overload range of an electric brake - Google Patents

Abstract

The invention relates to a method for determining an overload range (103) of an electric brake that is driven by an electric motor, in particular a parking brake, the overload range (103) being determined on the basis of a current consumption (120) of the electric motor. An overload range of an electric brake can be determined quickly, easily and reliably by means of the invention.

Description

The The invention relates to a method for determining an overload range an electric brake, a corresponding arithmetic unit, a corresponding computer program and a corresponding computer program product.

was standing of the technique

Especially In motor vehicles, more and more electric brakes, in particular Parking brakes, for use in which the brake is no longer manual by the driver but electrically or electromechanically by an electric motor delivered or found and resolved. Such brake systems offer increased Comfort and safety when parking and holding.

The electric parking brake (EPB, also electromechanical parking brake EMF) is from the vehicle interior by means of a switch or Operated buttons. Depending on the embodiment The electric parking brake can be used in different situations Driver a useful Be help or to additional Contribute safety. The electric parking brake can vary depending on Situation manually or automatically activated.

The Determining the brake is usually done by means of an electric motor, the one with the brake directly or over cables can be connected. To determine the brake, the rope with a predetermined force tensioned or the brake with a predetermined Force applied. In certain circumstances, it may be necessary the brake with increased Determine braking force, for example, while holding or parking on one downhill Street. To overload to delay, Electric parking brakes are typically equipped with a slip clutch. By The design principle of the slip clutch slip when reaching the predetermined / adjustable overload Components through or past each other, causing damage to the Brake is avoided. In this situation, the braking force must not further increased otherwise there is damage motor, cable or other mechanical components is expected.

at Atlas Copco electric tools becomes a friction clutch area acoustically recognized. Therefore Microphones are arranged in the tool, which provided for receiving the slip clutch noise are. If the slip clutch noise is detected, the power supply interrupted to the electric motor. For electric parking brakes, such a method is not suitable because it is error prone and unresponsive is.

It Therefore, the problem arises, a method for determining an overload range specify an electric brake, with an overload condition fast and reliable can be detected to damage the brake system as possible to avoid.

According to the invention a method for determining an overload range of an electrical Brake with the features of claim 1 and a corresponding Arithmetic unit, a computer program and a computer program product proposed. Advantageous embodiments are the subject of under claims and the description below.

Advantages of invention

at the method according to the invention becomes an overload area an electric brake, in particular a parking brake based a current consumption of the electric motor which drives the brake or actuated, certainly. The current consumption is special in an electric motor easy to detect, since no elaborate measuring devices are needed. Based on the current consumption is a conclusion on the load condition possible.

preferably, the overload range is based on a time course, i. a temporal change, the current consumption of the electric motor determined. To avoid one damage the brake is this conventionally with an overload protection, For example, a slip clutch equipped. Is located the brake in the overload range, performs the overload protection to a characteristic course of the current intake, as it was preferred example of a slip clutch in the following description will be explained in detail. The method is not limited to this embodiment, but can always be used if the overload range is due to a change over time makes the current consumption of the electric motor noticeable. By means of solution according to the invention can therefore an overload condition especially easy, reliable and above all be determined in real time. This can also be beneficial to dispense with the measured values of an existing force sensor, in an overload area often provides incorrect values, and therefore not regular statutory Provisions met. On the other hand can with the solution described statutory safety requirements are met.

It is expedient if, in the method according to the invention, a first period of time after starting, ie starting, of the electric motor is not used to determine the overload range. When starting an electric motor, there is an increased power consumption, which does not related to the overload range. Therefore, the method can be performed more easily by this configuration. However, it is also advantageous to take this area into account with a correspondingly adapted choice of the parameters.

at A preferred embodiment of the invention is the overload range based on at least one parameter of at least one extreme point, i. a local maximum or minimum over time Current consumption of the electric motor determined. The time course The current consumption can be particularly easy on the basis of occurring Extreme points are characterized.

• a) Art des Extrempunkts, wobei insbesondere zwischen Maximum und Minimum unterscheiden wird;
• b) Gültigkeit des Extrempunkts, wobei insbesondere zwischen einem gültigen und einem ungültigen oder zurückgezogenen Extrempunkt, wie weiter unten ausführlich beschrieben, unterschieden wird;
• c) Betrag der Differenz der Stromaufnahme zweier aufeinander folgender Extrempunkte;
• d) Anzahl der Extrempunkte innerhalb eines vorbestimmten Zeitraums.

It is particularly expedient if, in the method according to the invention, the at least one parameter is selected from the group:

• a) type of extreme point, whereby in particular will distinguish between maximum and minimum;
• b) validity of the extreme point, distinguishing in particular between a valid and an invalid or retracted extreme point, as described in detail below;
• c) amount of the difference between the current consumption of two consecutive extremes;
• d) number of extreme points within a predetermined period.

through this carefully chosen Parameter leaves the power consumption can be characterized particularly reliably.

According to the preferred Embodiment of Invention is the overload range based on the number of valid ones Extreme points within a predetermined period in time History of the current consumption of the electric motor determines, with a valid Extreme point by the predetermined threshold value of the current difference Are defined. In this advantageous embodiment, by means of only three parameters characterize the power consumption quickly and reliably become. The limit values for the Parameters can be used be determined once before the start of the procedure. They are for example to get from a measurement.

A Computing unit according to the invention comprises calculating means for the steps of a method according to the invention perform. It can be designed in particular as a control unit in a motor vehicle be.

One embodiment the computing unit according to the invention has means for receiving measured values which receive a current of the electric motor, and means for determining the overload range on the basis of the measured values.

A further advantageous embodiment of the computing unit according to the invention has means for determining extreme points over time Readings on.

It is advantageous if a method according to the invention and / or a Computing unit according to the invention be used in a motor vehicle.

One Computer computer according to the invention or microprocessor program contains Program code means for carrying out the method according to the invention, when the program on a computer, a microprocessor or a corresponding arithmetic unit, in particular the arithmetic unit according to the invention, accomplished becomes.

One Computer computer according to the invention or microprocessor program product includes program code means, stored on a machine or computer readable medium are to a method according to the invention to perform, if the program product on a computer, a microprocessor or on a corresponding arithmetic unit, in particular of the arithmetic unit according to the invention, accomplished becomes. Suitable media In particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, etc. Also a Download a program via Computer networks (Internet, Intranet, etc.) is possible.

Further Advantages and embodiments of the invention will become apparent from the Description and attached drawing.

It it is understood that the above and the following yet to be explained features not only in the specified combination, but also in other combinations or alone, without to leave the scope of the present invention.

The Invention is based on an embodiment schematically shown in the drawing and is below under Referring to the drawings described in detail.

figure description

1 shows a functional graph of a schematic time course of the current consumption;

2a shows a flow chart for distinguishing extreme points in a time course of power consumption;

2 B shows a flowchart for determining an overload range based on para meters concerning the extreme points;

3 shows a further functional graph of a schematic time course of the current consumption, wherein extreme points are distinguished; and

4 shows a measuring graph in which a time course of the current consumption, the number of extreme points, the number of valid extreme points and the overload range is shown.

In 1 is a functional graph total with 100 denotes a schematic time course of the current consumption 120 represents. In the function graph 100 is the current consumption I on an axis 121 against time t on an axis 122 applied.

The time course 120 can be divided into three areas. In one area 101 shows the current consumption an increasing course up to a first maximum 110 and then a descending course to a first minimum 111 , It is the starting area of the motor in which the power consumption first rises sharply before reaching normal operating levels. In order to avoid a mischaracterization of the current profile, it is expedient to use this first region 101 not to be considered in the characterization.

In a second area 102 the current curve again shows an increasing behavior up to a next maximum 112 , This area 102 corresponds to the normal operating range of the parking brake. The stronger the parking brake is applied, the higher the current consumption of the electric motor.

In a last area 103 follow a variety of maxima and minima, eg 113 . 114 , each other. This course of current consumption is caused by an active slip clutch and can be detected quickly and reliably by the embodiment of the method according to the invention described below.

In 2a a flow chart is shown in which it is shown how extreme points can be determined in a preferred manner.

The process begins in one process step 200 each with a new reading. In one step 201 the first or the next measured value is selected. In one process step 202 determines if the selected reading is an extreme point. For this purpose, all methods known in the prior art, for example differential calculus, can be used. It has proven to be particularly simple and reliable to compare the current difference from the current to the previous measuring point with the current difference from the preceding to the preceding measuring point. Current differences with a value of zero are preferably ignored. If these two current differences have different signs, the previous measuring point is an extreme point. In this case, the process becomes one step 203 otherwise, the process returns to the step 201 back. From the sign of the current difference, the nature of the extreme point can be determined. The detection of an extreme point is carried out by always recording the "last direction", ie the sign of the difference between the current and the previous measuring point. A difference of zero is ignored. When changing the sign of the "last direction", it is then clear that the previous measuring point was an extreme point. The nature of the extreme point can be taken from the (opposite) sign.

Subsequently, the method checks whether it is a valid extreme point, ie whether the current difference to the previous extreme point exceeds a threshold value ΔI and whether the type of the current extreme point differs from the type of the preceding extreme point. This is done in one step 203 calculates the current difference of the current to the previous extreme point.

Then the process moves with one step 204 in which the amount of the calculated current difference is compared with the predetermined threshold value ΔI. If the amount is greater than the predetermined threshold value, it will start with a step 205 otherwise proceeded with one step 206 ,

In the process step 206 it is checked if the previous extreme point is a valid extreme point. If the current extreme point is the first detected extreme point, this check is considered successful. If the previous extreme point is not a valid extreme point, it becomes a procedural step 201 returned. If, on the other hand, the last extreme point is a valid extreme point, it becomes a procedural step 207 branched.

In the step 207 becomes an associated entry of the last extreme point in an extreme point table 220 away. Subsequently, the method with the method step 201 continued.

In the extreme point table 220 For example, the extreme points are stored with their associated parameters current, time and type. She points For example, three columns 221 . 222 . 223 which sequentially record the named parameters line by line such that the parameters of the current extreme point are arranged in a readable manner in the table.

In the process step 205 It is determined whether the type (maximum, minimum) of the current extreme point differs from the type of the previous valid extreme point. If it does not differ, the process becomes the process step 201 continued. On the other hand, if the types of the two extreme points are different from each other, it will be in one step 208 branched. If it is the first detected extreme point, its current value is used as a current difference and also in the step 208 branched.

In the process step 208 become the parameters of the current extreme point in the table 220 entered. In a subsequent process step 209 the determination of the overload range is carried out as shown by 2 B is explained in more detail.

If no overload is detected, go back to step 201 branched.

In 2 B is the determination of an overload range based on the fine structure of the process step 209 out 2a explained in more detail.

In one process step 210 the number of valid valid points previously encountered is compared with a predetermined threshold nD. If the predetermined number of valid extreme points has not yet been reached, becomes a method step 201 out 2a returned.

If, however, the predetermined threshold value is reached, is in a process step 211 determines the time span within which the extreme points occurred.

In one process step 212 the time period is compared with a predetermined threshold value. If the time is greater than the predetermined threshold, no overload is determined and the method with the step 201 out 2A continued.

On the other hand, if the time interval is smaller than the predetermined threshold value, then in one step 213 determines or signals that the brake is in an overload range.

In 3 is another functional graph 300 in which a temporal course of the current consumption 303 on an axis I that with 302 is designated, against time t on an axis 301 is applied.

The time course 303 consists of a number of measuring points 304 . 305 . 306 etc. together, each having a current and a time value. As is usual, the measuring points are connected by a continuous line, which is the time course 303 the current consumption represents.

In the time course 303 is a first minimum with 304 designated. The area to the left of the minimum 304 represents the starting region of the engine, which is disregarded according to the preferred embodiment. It makes sense to do this by starting the initial range from zero over a first maximum (not shown) to the first minimum 304 not to be considered.

In carrying out the embodiment of the method according to the invention, based on the 2a and 2 B is described, after the first minimum 304 was determined, everyone on the measuring point 304 following measuring point 305 examined.

If the procedure reaches the measuring point 308 , it marks a measuring point 307 as maximum, since the current difference between the measuring points 308 and 307 has a different sign than the current difference between the measuring points 307 and 306 ,

Subsequently, the amount of current difference between the extreme points 307 and 304 determined and compared with the predetermined threshold .DELTA.I. Since the current difference in the selected example is greater than the predetermined threshold .DELTA.I, the extreme point 307 characterized as a valid maximum.

Subsequently, the other measuring points are characterized in sequence, until finally the measuring point 309 is recognized as an extreme point. Because the current difference of the measuring points 309 and 307 is also greater than the predetermined threshold .DELTA.I, the measuring point 309 initially also characterized as a valid minimum.

Subsequently, the process is continued until a measuring point 310 is recognized as maximum. Because the current difference between the extreme points 310 and 309 does not reach the predetermined threshold .DELTA.I in the example chosen, becomes the extreme point 310 not characterized as a valid extreme point. In the episode gem. step 207 out 2a also the previous extreme point 309 withdrawn, ie characterized as invalid, and from the table of valid extreme points 220 away. Furthermore, it is noted that the last extreme point was invalid.

In the further implementation of the method, the measuring point is next 311 recognized as minimum. Because the current difference between the extreme points 311 and 307 ( 309 and 310 are invalid) greater than the predetermined threshold ΔI, becomes the extreme point 311 recognized as a valid minimum. This procedure is carried out for all other measuring points.

at The previously described steps will always follow the Detecting a valid extreme point verifies that the brake already in an overload range located.

To will be first the number of valid extreme points compared with a predetermined threshold. Is the number greater than the predetermined threshold, then the period is determined in which these extreme points have occurred, and again with one predetermined threshold value compared. Is the duration smaller? as the predetermined threshold, an overload area is detected and the electric motor stopped.

through the described preferred embodiment of the invention can an overload range of one electric brake can be determined quickly, easily and safely.

In 4 is a measurement graph 400 shown in which a temporal course of the current consumption 410 , the number of extreme points 420 , the number of valid extreme points 430 and the determination of the overload range 440 is shown. The time course is in each case against the time t on an axis 401 applied. The time t starts at a time t = 0. At this time, the engine is started to feed the brake, which is indicated by a dashed line 402 is shown.

The time course of the current consumption 410 is on an axis for a current I, which with 411 is the time course of the number of extreme points 420 on an axis for a count n, which with 421 is designated, the time course of the number of valid extreme points 430 on an axis for a count n *, which with 431 is designated, and the time course of the determination of the overload range 440 on an axis for the overload range for the values 0 and 1, with the 441 is called, aufgetra gene. On the axis 441 the value 1 corresponds to a recognized overload range.

After starting the engine at the time t = 0, the time course of the current consumption goes through 410 turn first the start-up area 101 of the motor. The starting area is through three extreme points 412 . 413 and 414 marked the meter reading 420 until one time 422 increase to a value of 3.

Up to a next maximum 415 runs the suit area 102 of the electric motor. Will be the maximum 415 detected, the count increases 420 the detected extreme points at a time 423 to the value 4, the meter reading 430 the valid recognized extremes at a time 432 to a value 1. As can be seen in the illustration, the first detected extreme points are up to the time 423 not been registered as valid extremes since the startup area 101 of the engine is disregarded in the preferred embodiment.

In the time course of the current consumption 410 follow to the maximum 415 more extreme points 416 . 417 . 418 . 419 etc., which are characterized according to the described preferred embodiment of the method according to the invention as follows:
The extreme point 416 is recognized as a valid minimum, which is the count of detected extreme points 420 at a time 424 and the count of the valid detected extreme points 430 at a time 433 each increased by one count.

Subsequently, the extreme point 417 detected as a valid extreme point, which in turn the count of the detected extreme points 420 at a time 425 and the count of the valid detected extreme points 430 at a time 434 each increased by one count.

The following minimum 418 is due to the low current difference to the maximum 417 not recognized as a valid extreme point, which is why the count of the detected extreme points 420 is not increased at this time. According to the described embodiment, the count of the recognized valid extreme points 430 at a time 435 again reduced by one count. It is therefore a retracted extreme point.

The following extreme point 419 is again recognized as a valid extreme point, which, as already described in detail, the two counts again increased. At a time by a dashed line 403 is shown, the predetermined threshold value nD, which was selected to be 5 in this example, is reached for the predetermined period of time, resulting in detection of an overload range. Therefore, the time course of the determination of the overload range 440 at this time 403 set to the value 1.

Claims (11)

Method for determining an overload range ( 103 ) of an electric brake, the ei An electric motor is driven, in particular parking brake, characterized in that the overload range ( 103 ) is determined based on a current consumption of the electric motor. Method according to Claim 1, characterized in that the overload range ( 103 ) based on a time course of the current consumption ( 120 ; 303 ; 410 ) of the electric motor is determined. Method according to claim 2, characterized in that a first period ( 101 ) after a start of the electric motor not to determine the overload range ( 103 ) is used. Method according to one of claims 2 or 3, characterized in that the overload range ( 103 ) based on at least one parameter of at least one extreme point ( 110 - 114 ; 304 . 307 . 309 . 310 . 311 ; 412 - 419 ) in the time course of the current consumption ( 120 . 303 . 410 ) of the electric motor is determined. Method according to claim 4, characterized in that that the at least one parameter is selected from the group: kind of the extreme point, validity of the extreme point, amount of the difference of the current consumption of two consecutive extreme points, number of extreme points within a predetermined period. Method according to claim 4 or 5, characterized in that the overload range ( 103 ) based on the number of valid extreme points ( 304 . 307 . 311 ; 414 . 415 . 416 . 419 ) within a predetermined period in the time course of the current consumption ( 303 ) of the electric motor is determined. Arithmetic unit for determining an overload range ( 103 ) of an electric brake, which is driven by an electric motor, in particular control unit, ECU or embedded system, with calculation means to perform all the steps of a method according to one of the preceding claims 1 to 6. Computing unit according to Claim 7, having means for receiving measured values relating to a current consumption of the electric motor and means for determining the overload range ( 103 ) based on the measured values. Arithmetic unit according to Claim 7 or 8, having means for determining extreme points ( 110 - 114 ; 304 . 307 . 309 . 310 . 311 ; 412 - 419 ) over time ( 120 ; 303 ; 410 ) of the measured values. Computer or microprocessor program with program code means, to all steps of a method according to one of claims 1 to 6 to perform if the program is on a computer, a microprocessor or a corresponding arithmetic unit, in particular according to claim 7, executed becomes. Computer or microprocessor program product with Program code means based on a machine or computer readable disk are saved to all steps of a procedure according to one of claims 1 to 6, if the program product is on a computer, a microprocessor or on a corresponding arithmetic unit, in particular according to claim 7, executed becomes.