DE102016206095A1 - Method and device for determining whether a fault condition exists in a motor vehicle or not - Google Patents

Abstract

A method for determining whether an error is present in the operation of an internal combustion engine (10) of a motor vehicle (1) in which a change in a desired value of an operating variable of the motor vehicle (1) is determined as a function of a determined change in a driver request, wherein depending on a deviation is determined depending on the change in the setpoint and the change of a determined actual value of the operating variable, it is decided whether the error is present.

Description

The invention relates to a method for determining whether or not there is a fault condition in a motor vehicle. The invention further relates to a device, in particular a control device, which is set up to carry out this method.

State of the art

From the DE 44 38 714 A1 a method for controlling the driving power of a vehicle is known, wherein a microcomputer is provided for performing control functions and monitoring functions. Microcomputers are defined at least two independent levels, wherein a first level performs the control function and a second level, the monitoring function.

Disclosure of the invention

The invention relates to a method having the features of independent claim 1. Advantageous developments are the subject of the dependent claims.

In a first aspect, the invention relates to a method for determining whether an error, in particular an unwanted acceleration, is present when operating an internal combustion engine of a motor vehicle. In the method, a change of a setpoint value of an operating variable, in particular a torque, a power or an acceleration, of the motor vehicle is determined depending on a determined change of a driver, depending on a deviation that depends on the change of the setpoint and the change of a determined Actual value of the operating size is determined, it is decided whether the error is present.

For example, the deviation can be determined as the difference between the change in the setpoint and the change in the actual value. If an absolute value of the deviation is then greater than a predefinable threshold value, then it is decided that the error is present. Alternatively or additionally, it may be decided that the error is present if the difference is negative, i. if the change of the setpoint value is smaller than the change of the actual value.

If it has been decided that the error is present, appropriate countermeasures can be taken to bring the motor vehicle in a safe state. For example, a maximum torque that can be generated by the internal combustion engine can be limited.

This method can be used in a second level of the control of the internal combustion engine, in which such as from DE 44 38 714 A1 the first level is the control functions and the second level is the monitoring function. This has the advantage that the number of interfaces between the planes is reduced and thereby the coupling between the planes is minimized, which increases the reliability.

It is provided here that the internal combustion engine is controlled depending on the desired value of the operating variable, in such a way that adjusts the actual value of the operating variable to the desired value in error-free case, as for example from the first level of DE 44 38 714 A1 is known.

In another aspect, it can be provided that the change in the desired value of the operating variable is determined by means of a relationship which describes the change in the desired value of the operating variable as a function of the determined change in the driver's request. This relationship can e.g. stored in a controller, for example as a map or as a mathematical function or as a combination of the two. Such a method is particularly easy to apply, i. Its parameters are particularly easy to adapt to the properties of the motor vehicle, because in this context, such factors that have only a slowly changing influence on the setpoint of the operating size, do not have to be considered. This is possible because these influences would cancel out in determining the change in the setpoint of the operating quantity.

In a further aspect, it can be provided that the change in the setpoint value of the operating variable is determined as a difference between two setpoint values of the operating variable determined at successive times. The desired value of the operating variable can be determined in each case depending on a determined value of the driver's request. In this case, too, it is possible to dispense with the determination of the setpoint values to take account of influencing variables which have only a slowly changing influence on the setpoint value of the operating variable.

In particular, the desired value of the operating variable can be determined independently of an operating state of an air conditioning compressor and / or a generator.

In a further aspect it can be provided that the change of the setpoint value and the change of the actual value are determined over a first predeterminable period of time. This means that changing the setpoint and changing the actual value describes the change between the start and the end of the first predefinable time period. Here can be provided in particular that, when it was decided depending on the deviation that the error is present, a second change of the setpoint and a second change of the actual value over a second predetermined period, which is longer than a first predeterminable period, is determined, in which case a second deviation is determined as a function of the second change of the setpoint value and the second change of the actual value, and a decision is made depending on the second deviation as to whether the error exists. This allows a simple Fehlerentrprellung be achieved.

In a further aspect it can be provided that partial deviations between the change of the setpoint value and the change of the actual value are respectively determined during successive periods and the deviation is determined as a function of the partial deviations. For example, the deviation is determined as the sum of the partial deviations. For example, successive periods immediately follow one another, i. End point of a previous period and starting point of a subsequent period coincide respectively.

In a further aspect, it may be provided that the deviation is determined during a third time period and wherein a second deviation is determined as a function of a change in the desired value and a change in a determined actual value of the operating variable during a fourth time period, and depending on a comparison first deviation with the second deviation is decided on whether the error is present.

In a further development of this aspect it can be provided that the third period comprises a first cycle of the internal combustion engine and the fourth period comprises a second cycle of the internal combustion engine, the start and end times of the third and fourth periods are in an angle synchronous grid of a crankshaft of the motor vehicle , That the deviation between the change in the desired value and the change in the actual value can be compared over a plurality of angle-synchronous time segments, for example over different working cycles or over different periods corresponding to several working cycles. Such a method is particularly easy to adapt to the respective motor vehicle.

In a further aspect, it can be provided that when an electrical consumer of a vehicle electrical system is switched on or off, the method is deactivated. This means that setpoint values and / or actual values which are determined during a period in which a switch-on time or a switch-off time of the electrical load is determined are not used for the comparison. This makes the process particularly reliable. During these periods, for example, an alternative monitoring method can be used.

In a further aspect it can be provided that a delay element, in particular a PT1 filter, is used in the determination of the desired value. In particular, the determination of the desired value and / or the determination of the change in the desired value can be filtered by a delay element. In this way, it can be taken into account in a particularly simple way that a delay in time can occur between an actuation of an accelerator pedal and a corresponding change in the actual value.

In further aspects, the invention relates to a computer program configured to perform all the steps of one of the methods according to one of the aforementioned aspects, a machine-readable storage medium on which the computer program is stored, and a controller configured to perform all the steps of one of the methods of one to carry out the aforementioned aspects.

The figures show examples of particularly advantageous embodiments of the invention. Show it:

1 a motor vehicle in which the invention can be used;

2 a structure diagram of signal flows according to an embodiment of the invention;

3 a structure diagram of signal flows according to another embodiment of the invention;

4 an illustration of a core idea of an aspect of the invention;

5 a time course of a generator torque;

6 temporal courses of different torques;

7 Flowchart of possible embodiments for determining the change of the setpoint of the operating variable;

8th a flowchart for the procedure of the method for determining the error.

Description of the embodiments

1 shows a motor vehicle 1 that of an internal combustion engine 10 is driven. The Internal combustion engine 10 is via an operative connection, for example a belt drive 50 , with a generator 40 coupled. An engine control unit 98 is via a communication connection 70 , For example, a CAN bus, with the internal combustion engine 10 and the generator 40 connected. The engine control unit 98 can the internal combustion engine 10 and the generator 40 drive and receive signals from them. The engine control unit 98 For example, with a machine-readable storage medium 99 be equipped on the computer programs that are in the engine control unit 98 can expire, are stored. The engine control unit 98 can also have an air conditioning compressor 60 control and receive signals from this. An accelerator pedal 20 may be provided in a conventional manner by a driver of the motor vehicle 1 to be actuated. An accelerator pedal sensor 30 is set up, a position of the accelerator pedal 20 (So its degree of actuation) to capture and to the engine control unit 98 to convey.

2 shows a structure diagram of signal flows, as for example in the engine control unit 98 can expire. Via an input interface 96 receives the engine control unit 98 Sizes that represent the current operating state of the internal combustion engine 10 , the generator 40 , the accelerator pedal 20 and the air conditioning compressor 60 characterize. From the accelerator pedal sensor 30 transmitted signal is extracted in a conventional manner, the driver request APP and to a function block 100 transmitted. The function block 100 determined from the driver's request APP and possibly from other variables, a desired torque Ms, that of the internal combustion engine 10 should be generated. This signal is sent to a difference detection block 102 and an output interface 95 transfer. The output interface 95 transmits the target torque Ms to another block 104 in the engine control unit 98 , the driving variables yi for the internal combustion engine 10 determine, for example, an opening degree of a throttle valve, an injection amount, an injection timing and / or an injection angle. These quantities are then sent to the internal combustion engine 10 transfer.

The block 104 is set to select the drive quantities yi so that one of the internal combustion engine 10 generated actual torque corresponds to the target torque. This method is known from the prior art, for example from the first level, ie the functional level 12 , of the DE 44 38 714 A1 is known. This illustration is intended to be considered as an embodiment as incorporated by reference.

The difference determination block 102 determines from the target torque Ms a change in the target torque .DELTA.Ms, which characterizes the change of the target torque Ms with respect to an earlier point in time. The input interface 96 receives, for example, from the internal combustion engine 10 , from generator 40 , from the air conditioning compressor 60 and the accelerator pedal sensor 30 , State variables xi, which denote the respective state of these components. The state variables xi are sent to an actual value determination block 103 transmitted. The actual value determination block 103 determined depending on the state variables xi currently from the internal combustion engine 10 generated actual torque (or an estimated value for this generated actual torque). The actual value determination block 103 further determines an actual torque change .DELTA.M.sub.i indicative of a change of the detected actual torque from an earlier time. The actual torque change ΔMi is sent to a change evaluation block 101 transmitted. The change determination block 101 determined from setpoint torque change ΔMs and actual torque change ΔMi, whether a malfunction during operation of the internal combustion engine 10 is present. If this is the case, an emergency signal xn becomes a function determination block 100 transmitted, then countermeasures for transferring the internal combustion engine 10 into a safe operation can initiate.

3 shows a structure diagram of signal flows according to another embodiment. Opposite the in 2 illustrated embodiment, the way in which the target torque change .DELTA.Ms is determined, different. Only the parts that are opposite are described 2 are changed. The driver request APP is from the input interface not only to the function block 100 , but also to a driver request difference determination block 105 transmitted. The driver's request difference determination block 105 determines a change ΔAPP of the driver's request APP from an earlier point in time, and transmits it to the difference determination block 102b , The difference determination block 102b determined from the difference of the driver's request ΔAPP the change of the setpoint torque ΔMs. The thus determined change of the target torque ΔMs is transmitted to the differential determination block 102b to the change assessment block 101 ,

4 illustrates a core idea of the invention. 4a) illustrates the basic principle of torque monitoring, as known from the prior art, for example DE 44 38 714 A1 is known. 4b) illustrates a thought as it underlies an aspect of the invention. In 4a) and 4b) is in each case the torque M of the internal combustion engine 10 applied to the driver's request APP. This schematic representation is valid for both the actual torque and the target torque. For a given speed N of the internal combustion engine follows the course of the torque M as a function of Driver request APP of a characteristic curve. In the present illustration, a first speed n1 of the internal combustion engine 10 accepted. In the monitoring method according to the prior art, the associated torque M1 is determined from the present first driver request APP1. On the basis of the thus determined setpoint torque, in which the determined actual torque is determined, whether an error in the control of the internal combustion engine 10 is present.

In contrast, it is proposed according to a first aspect of the invention not to use an actual value of the driver's request APP to determine the desired torque, but a change ΔAPP the driver's request. From the change .DELTA.APP of the driver's request, a change .DELTA.Ms of the target torque is then determined, and based on the thus determined change in the desired torque .DELTA.Ms with a change in the actual torque is closed, whether an error in the control of the internal combustion engine 10 is present.

5 and 6 illustrate the advantages of this first aspect of the invention. 5 shows a time course of the generator 40 Applied generator torque Mg. The in 5 shown period is exemplified several seconds, about 25 seconds. A generator torque fluctuation width ΔMg_Max during this time period only takes a small amount, for example <1Nm. As in 6 illustrated, the generator torque Mg thus changes much slower than that of the internal combustion engine 10 generated torque, and thus can be considered as almost constant over time.

6 shows the time course of different torques M of components of the motor vehicle 1 , An air compressor torque MK of the air conditioning compressor 60 , the generator torque Mg, the target torque Ms of the internal combustion engine 10 , and the driver's request APP. You can see that the torque requirements of the generator 40 and the air conditioning compressor 60 remain almost constant over time and need not be taken into account in the monitoring. You also look 6 in that the changes to the driver's request APP correspond, in a very good approximation, directly to the changes in the setpoint torque Ms. The friction losses of the internal combustion engine 10 are so small that they can be neglected. Ie. in the 6 As illustrated, all friction losses and all torque requirements of the accessories are so small that their changes can be neglected. In this case, the maximum decoupling between the monitoring level and the functional level is achieved. If accessory torque or torque requests do not have the characteristic that their changes are so small that they can be neglected, their permissible changes must be taken into account in the monitoring function. However, this does not eliminate the extensive decoupling between the monitoring level and the functional level.

7 shows two flowcharts of methods, as they can be used to determine the difference of the desired torque .DELTA.Ms. 7a) illustrates a method as described in the in 2 illustrated embodiment may be used. In step 1000 the driver request APP is read in, and in the next step 1010 the target torque Ms associated with this driver request APP is determined, for example by means of a characteristic map. The steps 1000 and 1010 can in the function block 100 be executed. In the next steps 1020 for example, in the difference determination block 102 is performed, the target torque difference ΔMs is determined. A subscript i denotes discrete points in time at which the setpoint torque Ms is determined in each case. This is indicated by the notation Ms_i. The desired torque changes ΔMs can then be determined, for example, by the formula ΔMs_i = Ms_i-Ms_ (i-1).

7b) shows a method such as in the in 3 illustrated embodiment may be used. In step 2000 the driver request APP is detected, and in step 2010 From this, the driver's request change ΔAPP determined. This takes place, for example, by means of the formula ΔAPP_i = APP_i - APP_ (i-1). The steps 2000 and 2010 For example, in the driver's request difference determination block 105 executed. In step 2020 the desired torque change ΔMs is determined from the driver request change ΔAPP, for example by means of a characteristic map. This determination can be made in the difference determination block 102b be performed. With step 1020 or step 2020 ends in each case the method for determining the desired torque change .DELTA.Ms.

8th shows a method for determining whether in the control of the internal combustion engine 10 there is a mistake or not. In step 3000 the state variables XI are read in, and in step 3010 from the state variables XI for the respective discrete time step i, the actual torque Mi_i determined. In the next step 3020 For example, the change of the actual torque ΔMi at the discrete time i is determined according to the formula ΔMi_i-ΔMi_ (i-1). Parallel will be in step 3030 the change in the target torque .DELTA.Ms_i discrete time i is determined, and in the following step 3040 optionally delayed, for example by means of a PT1 filter. This filtering in step 3040 can take into account the fact that when operating the accelerator pedal 20 the actual torque Mi starts with a time delay tau. In step 3050 it is now determined whether an error exists. For this purpose, several alternative methods are conceivable.

According to a first method it can be provided that it is checked whether the difference of the setpoint torque ΔMs_i coincides with the difference of the actual torque ΔMi_i. Ie. It can be checked whether the difference ΔMs_i - ΔMi_i is below a permissible threshold. The threshold may be selected depending on how large the time interval of the times i and i - 1, based on the change of the desired torque .DELTA.Ms_i and the actual torque .DELTA.Mi_i was determined. It is conceivable here, for example, to determine the differences in a 10 ms or 50 ms grid, but it can also be determined in a longer interval, for example of 2000 ms. It can also be provided that these differences are formed stepwise at different time intervals, for example first over a period of 20 ms, then 50 ms, then 100 ms, then 200 ms, etc. If the torque change within a first time interval, for example 20 ms, is outside the allowable threshold, the torque change is also checked within the next period, for example 50 Ms and so on. If at a critical time interval, for example 2000 Ms, this difference exceeds the allowable threshold, then this method ensures that this difference is also in all previous time intervals exceeds the permissible threshold. In this case, it is decided that there is an error.

In a further embodiment, the changes in the target torques Ms_i and the actual torque Mi_i can be summed up in each case over a predetermined period of time to thus dependent on the difference Σ _i Ms _i - is decided Σ _i Mi _i on whether a fault is present. If this difference is greater than a threshold, it is decided that there is an error.

In another embodiment, it may be provided to form the deviation between change of the setpoint torque ΔMs_i and the change of the actual torque ΔMi_i for each discrete point in time, to sum up these changes and then to decide on errors, if this sum Σ _i (ΔMs _i - ΔMi _i ) is greater than a threshold value.

In a further embodiment, it can be provided that a respective average change in the desired torque ΔMs and the actual torque ΔMi is determined, that then an average deviation between these variables with the formula 1 / nΣn / i = 1ΔMs _i -1 / nΣn / i = 1ΔMi _i is determined, and an error is decided if this difference is greater than a threshold value.

In all of these embodiments, it is possible that the allowable threshold values are selected differently in the positive and negative directions, respectively. In particular, it is possible that a deviation in the positive direction may assume very large values (ie that the actual torque Mi may be smaller than the setpoint torque Ms), and / or that the permissible threshold value in the negative direction is selected to be significantly smaller than the allowable threshold in the positive direction, d. H. that the error is quickly decided when the actual torque Mi is greater than the target torque Ms. This is because in the case of a negative deviation, there is an unwanted acceleration, which can lead to a dangerous situation.

The time intervals considered in each case can be calculated in the segment-synchronous grid, that is to say in synchronism with revolutions of a crankshaft of the internal combustion engine 10 , Then the time intervals are dependent on the speed of the internal combustion engine 10 varies in length and if an error is detected, step follows 3060 in which a warning message to the driver of the motor vehicle 1 can be output and / or the control of the internal combustion engine 10 can be modified so that the internal combustion engine 10 operated in a secure operation. Was in step 3050 when it is recognized that there is no error, the process ends in step 3070 ,

The described embodiments are not limited to the operating variable "torque". Instead of a torque of the internal combustion engine can be used equivalently a power of the internal combustion engine, or an acceleration of the motor vehicle 1 , If the monitoring is carried out on the basis of the operating parameter "acceleration", the external influences causing a slow increase of the acceleration can be eliminated. This can z. B. interference, caused by the air resistance and / or rolling resistance. Also, the disturbances caused by the slope of the road can be eliminated by forming the differences in a sufficiently short time interval, for example 10 ms.

It is understood by those skilled in the art that the method described in the control unit 98 can be performed, or in other components. The method may be implemented in software, or in hardware or in a hardware and software mixing room.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4438714 A1 [0002, 0007, 0008, 0030, 0033]

Claims (14)

Method for determining whether during operation of an internal combustion engine ( 10 ) of a motor vehicle ( 1 ) there is an error in which, depending on a determined change of a driver's request, a change in a desired value of an operating variable of the motor vehicle ( 1 ) is determined, wherein depending on the desired value of the operating variable, the internal combustion engine ( 10 ) is determined, depending on a deviation which is determined as a function of the change in the desired value and the change of a determined actual value of the operating variable, it is decided whether the error is present. The method of claim 1, wherein the change of the desired value of the operating variable is determined by means of a relationship that describes the change of the desired value of the operating variable depending on the determined change of the driver's request. The method of claim 1, wherein the change of the setpoint value of the operating variable is determined as a difference of two determined at successive times setpoint values of the operating variable. Method according to claim 3, wherein the nominal value of the operating variable is independent of an operating state of an air conditioning compressor ( 60 ) and / or a generator ( 40 ) is determined. Method according to one of the preceding claims, wherein the change of the desired value and the change of the actual value over a first predetermined period of time is determined. The method of claim 5, wherein, when it was decided depending on the deviation, that the error is present, a second change of the setpoint and a second change of the actual value over a second predetermined period, which is longer than a first predetermined period, is determined , in which case a second deviation is determined as a function of the second change of the setpoint value and the second change of the actual value and, depending on the second deviation, a decision is made as to whether the error exists. The method of claim 1, wherein partial deviations between the change of the setpoint and the change of the actual value are respectively determined during successive time intervals and the deviation is determined depending on the partial deviations. The method of claim 1, wherein the deviation is determined during a third time interval and wherein a second deviation is determined depending on a change of the setpoint and a change of a determined actual value of the operating variable during a fourth interval of intents, and wherein depending on a comparison of a first deviation with the second deviation is decided on whether the error is present. The method of claim 8, wherein the fourth period is a first cycle of the internal combustion engine ( 10 ) and the fifth period a second cycle of the internal combustion engine ( 10 ), wherein start and end times of the fourth and the fifth period in an angle-synchronous grid of a crankshaft of the motor vehicle ( 1 ) lie. Method according to one of the preceding claims, wherein when an electrical consumer ( 60 ) of a vehicle electrical system is switched on or off, the method is deactivated. Method according to one of the preceding claims, wherein in determining the desired value, a delay element, in particular a PT1 filter, is used. Computer program adapted to carry out all the steps of one of the methods according to one of Claims 1 to 11. Machine-readable storage medium ( 99 ) on which the computer program according to claim 12 is stored. Control unit ( 98 ) arranged to carry out all steps of one of the methods according to one of claims 1 to 11.

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