CN106042926B

CN106042926B - Method for safety monitoring of a drive in a motor vehicle

Info

Publication number: CN106042926B
Application number: CN201610205027.3A
Authority: CN
Inventors: D.科瓦克; T.佐勒; G.庞格拉茨
Original assignee: Bayerische Motoren Werke AG; Robert Bosch GmbH
Current assignee: Bayerische Motoren Werke AG; Robert Bosch GmbH
Priority date: 2015-04-02
Filing date: 2016-04-05
Publication date: 2020-12-18
Anticipated expiration: 2036-04-05
Also published as: CN106042926A; DE102015206077B4; DE102015206077A1

Abstract

The invention relates to a method for safety monitoring of a drive in a motor vehicle, wherein a fault signal (F) is generated in the event of a fault, wherein it is determined whether a fault situation exists in which an unintentional slip factor-slip is present on at least one of the drive shafts of the motor vehicle, and at least one fault response parameter (y) of a controller (2) of the motor vehicle is set if an unintentional slip factor is determined on at least one of the drive shafts of the motor vehicle, wherein the at least one fault response parameter (y) changes a response time (T) of the controller (2) for outputting the fault signal (F).

Description

Method for safety monitoring of a drive in a motor vehicle

Technical Field

The present invention relates to a method for safety monitoring of a drive in a motor vehicle, and to a computing unit and a computer program for carrying out the method.

Background

In order to prevent unintentional (positive or negative) accelerations of the motor vehicle, for example due to software or hardware faults in the motor or transmission controller, a torque-based or acceleration-based 3-level monitoring or monitoring can be provided. The 3-level monitoring triggers a malfunction response if the learned motor torque or the learned vehicle acceleration is not plausible and/or a permissible limit value for the learned motor torque or the learned vehicle acceleration is exceeded. The error response may be, for example, a fuel supply shut-off and/or a rotational speed limitation of a drive of the motor vehicle.

In the case of acceleration-based 3-level monitoring, the expected vehicle acceleration or the setpoint vehicle acceleration can be determined, for example, by evaluating the setpoint torque. Furthermore, the actual vehicle acceleration of the motor vehicle is determined, for example, by means of an acceleration sensor. A fault situation is inferred by a comparison of the actual vehicle acceleration with the setpoint vehicle acceleration, for example if the actual vehicle acceleration exceeds the setpoint vehicle acceleration by a certain measure. However, such acceleration-based monitoring does not allow reliable detection in the following manner in the case of a loss of adhesion (haftungsabris) driving situation, as in DE 102001075509 a1, because of small changes in the acceleration value: for example, the actual vehicle acceleration exceeds the target vehicle acceleration by a certain amount. This occurs, for example, in the following cases: the motor vehicle moves with 2/3 with maximum possible constant lateral acceleration on a circular track radius (which may occur in particular in poor weather conditions, for example during snow or rain) on a road with a low coefficient of friction (μ r ~ 0.3) at constant speed and a constant steering wheel angle, and then provides a maximum drive torque, for example due to a torque error or an accelerator pedal failure. This may cause slippage of the drive wheels or drive shafts, which in turn may lead to lane departure consequences due to oversteer or understeer.

There is therefore a need for an improved method for safety monitoring of a drive in a motor vehicle.

Disclosure of Invention

The invention relates to a method for safety monitoring of a drive in a motor vehicle, and to a computing unit and a computer program for carrying out the method.

In a first step, a method for safety monitoring of a drive in a motor vehicle determines whether a fault situation exists in which an unintentional slip rate (Schlupfwett) is present on at least one of the drive axles of the motor vehicle, that is to say whether the wheels of the drive axle significantly rotate too fast or too slow when measuring the actual travel speed.

As soon as a driving force or a braking force is transmitted to the wheels, a small slip ratio not equal to zero occurs. The slip rate depends on the speed and the force transmitted. If the wheel is accelerated or braked so severely that the maximum traction is exceeded, the slip increases until uncontrolled slipping (slipping) or slipping/locking (slipping) of the wheel can occur.

In a further step, at least one fault response parameter of a control unit of the motor vehicle is adjusted if an unintentional slip rate is determined, wherein the at least one fault response parameter changes a response duration of the control unit for outputting a fault signal. The response duration is thus indirectly or directly adjusted depending on the presence of an unintentional slip rate. By adjusting the at least one fault response parameter, the sensitivity of the fault detection is increased in this case in a targeted manner. A fault can thus also be detected if, as is the case, for example, in the case of the cornering situation described at the outset, only a small change in the acceleration value occurs in the case of a loss-of-adhesion driving situation. By detecting whether a slip rate intended or not by the driver of the motor vehicle is present at least one drive shaft, the sensitivity of the error detection is improved, in particular in the case of unintentional slipping or locking of the drive wheels or drive shafts, and the tolerance of the error detection is increased in the case of driving in which the drive wheels or drive shafts are intentionally slipping.

In the event of a fault, the fault response is then advantageously initiated, i.e. the torque is reduced and/or the rotational speed is limited when the slip ratio is positive, and the torque of the drive shaft is switched off (for example by switching off the clutch) when the slip ratio is negative.

In one embodiment, in order to determine whether a fault situation exists, the vehicle longitudinal acceleration is compared with a variable that is dependent on the axle acceleration (achsbeschleunigg), i.e. the longitudinal acceleration resulting from the rotational acceleration of the drive axle and the geometry (wheel size, etc.), and an unintentional slip rate is inferred if the vehicle longitudinal acceleration deviates from the variable, in a practical embodiment preferably by more than a predeterminable threshold value. If the vehicle longitudinal acceleration is smaller than said quantity, this means a positive slip, i.e. the drive shaft is rotating too fast. If the vehicle longitudinal acceleration is greater than the variable, this means a negative slip, i.e. the drive shaft is rotating too slowly. The vehicle longitudinal acceleration can be determined, for example, by measurement techniques, for example, by means of an acceleration sensor, while the axle acceleration can be derived, for example, from the axle speed change. The variable may be, in particular, the axle acceleration itself.

According to another embodiment, the gradient acceleration of the motor vehicle (caused by downhill power) is included in the variable. For this purpose, the vehicle longitudinal acceleration is compared with a difference between the axle acceleration and the maximum gradient acceleration (steigingsbeschlenigg) as a variable, and an unintentional slip rate is inferred if the vehicle longitudinal acceleration deviates from the variable, preferably by more than a predeterminable threshold value in a practical embodiment. The detection of a fault situation is thereby further improved by correcting this in such a way that the maximum gradient acceleration of the motor vehicle is taken as the magnitude. The gradient acceleration can be determined, for example, from a gradient measured by means of a gradient sensor.

In a preferred embodiment, the axle speed, i.e. the rotational speed, of at least one drive axle is evaluated for determining the axle acceleration. The axle acceleration is thus determined in a simple manner in terms of measurement, for example by a digital differentiation of the axle speed. Alternatively or additionally, other physical variables such as torque, force, energy and/or power can also be detected and evaluated directly or indirectly.

According to another embodiment, an unintentional slip rate is inferred if the variable dependent on the longitudinal acceleration of the vehicle is greater than a maximum permissible acceleration limit value or less than a minimum permissible acceleration limit value of the motor vehicle. The maximum permissible acceleration value corresponds to the maximum longitudinal acceleration value that can be provided by the drive device, taking into account the current operating state (predefined essentially by the accelerator pedal position). The minimum permissible acceleration value corresponds to the minimum longitudinal acceleration value that can be expected by the drive, taking into account the current operating state (predefined essentially by the accelerator pedal position). The variable may be, in particular, the longitudinal acceleration of the vehicle itself.

In a further embodiment, the sum of the vehicle longitudinal acceleration and the inertial acceleration of the drive is used as the variable dependent on the vehicle longitudinal acceleration. "inertial acceleration" refers to angular acceleration produced by the moment of inertia and torque of the drive. It describes the internal acceleration of the drive, i.e. in particular the change in the motor speed and the wheel speed. It is determined, for example, by means of a digital differentiation of these rotational speeds. If the torque of the drive cannot be converted into a longitudinal acceleration due to the low coefficient of friction, the proportion of this rotation is increased or reduced considerably in comparison with the longitudinal acceleration. The additional detection and consideration of the inertial acceleration allows for a driver-desired torque which is reflected only in the change in the rotational speed of the drive and not in the change in the actual translational longitudinal acceleration of the vehicle.

In a further embodiment, an evaluation variable for the fault situation is determined and the fault signal is output as a function of the evaluation variable. The output of the fault signal can be accelerated or delayed accordingly depending on the severity of the fault, which is indicated by the evaluation variable. The faster the fault signal is output if the slip ratio deviates more from the reference value (slip ratio = 0), which leads to an improvement in safety.

In a further embodiment, a sum of the vehicle longitudinal acceleration and the inertial acceleration is formed for determining the evaluation variable. This increases the safety in view of the possible total acceleration of the motor vehicle.

In a further embodiment, a maximum permissible acceleration limit value or a minimum permissible acceleration limit value is used for determining the evaluation variable. The acceleration limit value is compared, for example by subtraction, with the sum of the vehicle longitudinal acceleration and the rotational acceleration. A fault situation is thereby inferred only when the maximum permissible acceleration limit value is exceeded or when the minimum permissible acceleration limit value is undershot, which improves the accuracy of the detection of the fault situation.

In a further embodiment, a threshold value for the evaluation variable is determined as a function of the fault response variable, wherein the output of the fault signal takes place when the evaluation variable exceeds the threshold value. In this way, the level of the threshold value for the evaluation variable is reduced in the event of a fault or in the event of a loss of adhesion, which again shortens the response time of the controller up to the time for outputting the fault signal.

In a further embodiment, the factor for the evaluation variable is determined as a function of the fault response parameter. A further improvement in safety results if the error signal is output as a function of the evaluation variable amplified by a factor.

The inventive computing unit, for example a controller, of a motor vehicle is designed, in particular, in terms of program technology, for carrying out the inventive method.

It is also advantageous to implement the method in the form of software, since this results in particularly low costs, especially if the controller is designed for other tasks as well and is therefore already present. Suitable data carriers for supplying the computer program are, in particular, optical disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and other data carriers. The program may also be downloaded via a computer network (internet, intranet, etc.).

Further advantages and embodiments of the invention emerge from the description and the drawing.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or individually without departing from the scope of the invention.

Drawings

The invention is schematically illustrated in the drawings by means of an embodiment and will be described in detail below with reference to the drawings.

Fig. 1 shows a signal diagram of a preferred embodiment of the invention in a schematic representation.

Detailed Description

Fig. 1 shows a schematic representation of a signal diagram of a safety function according to a preferred embodiment, which is implemented in a control unit 2 of a motor vehicle, for example a motor control unit. The safety function describes the positive slip rate, i.e. the situation of the wheel slipping. A negative slip ratio, i.e. a wheel lock, is then produced by appropriate adjustment of the comparator element.

The controller 2 is designed as a computer unit of the motor vehicle for safety monitoring of the drive of the motor vehicle and, in the event of a fault, generates a fault signal F.

If the motor vehicle is moving with a maximum possible constant lateral acceleration 2/3 on a circular track radius on a constant speed and constant steering wheel angle on a roadway with a low coefficient of friction (μ r — 0.3) and then provides the maximum drive torque, for example due to a torque error/accelerator pedal failure, a fault situation may occur, for example: the consequence may be a loss of adhesion, due to which the vehicle leaves its lane. Here, "adhesion loss" refers to the possibility of unintentional slipping of at least one drive shaft of the motor vehicle as a means for unintentional slip rates.

The safety function shown in the control unit 2 has five input connections and one output connection.

The first input connection is provided for an axle acceleration a _ axle of at least one drive axle of the motor vehicle, the second input connection is provided for a gradient acceleration a _ slope of the motor vehicle, the third (doubly) input connection is provided for a measured value of an actual vehicle longitudinal acceleration a _ laengs in a direction of travel of the motor vehicle, the fourth (doubly) input connection is provided for an inertial acceleration a _ rot of a drive of the motor vehicle, and the fifth (doubly) input connection is provided for a maximum permissible acceleration limit value a _ zul _ max of the motor vehicle.

The axle acceleration a _ axle can be determined, for example, by maximizing the averaged rotational acceleration of each axle, which is obtained by means of the differential (diffrenzierung) of the wheel speed, for example, according to the following equation:

V/H: front/rear

R/L: right/left.

The gradient acceleration a _ slope of the motor vehicle can be determined from the gradient angle α measured by means of a gradient sensor, for example according to the following formula:

a_slope=g*sinα

g: acceleration of gravity.

The actual vehicle longitudinal acceleration a _ laengs in the direction of travel can be determined by means of an acceleration sensor.

The inertial acceleration a _ rot of the drive of the motor vehicle can be determined from the differentiation of the drive components for the motor rotational speed and the wheel rotational speed and, if appropriate, the additional rotation.

The maximum permissible acceleration limit a _ zul _ max of the motor vehicle can be determined from the accelerator pedal position and the temporal gradient of said accelerator pedal position. Advantageously, positive and/or negative torque requests are additionally included in the determination by active driver assistance systems (ESP, ASR, ACC, …).

The output connection of the controller 2 is designed to output a fault signal F when a fault situation exists. In the present exemplary embodiment, the fault signal F is a binary signal with a logical HIGH in the fault case and a logical LOW in the non-fault case.

The safety function furthermore has a first subtractor 4, a first comparator 6, an and element 8, a controllable changeover switch 10, a first adder 12, a second comparator 14, a second adder 16, a second subtractor 18, a maximum value determiner 20 and an integrator 22.

The axle acceleration a _ axle and the gradient acceleration a _ slope of the motor vehicle are supplied to the first subtractor 4 as input variables. The first subtractor 4 provides the difference diff _ a _ s as an output variable.

The difference diff _ a _ s, like the vehicle longitudinal acceleration a _ laengs, is supplied as an input variable to the first comparator 6, which provides a logical HIGH signal as an output signal if the difference diff _ a _ s is greater than the vehicle longitudinal acceleration a _ laengs. Otherwise, a logical LOW signal is provided.

The vehicle longitudinal acceleration a _ laengs of the motor vehicle and the rotational acceleration a _ rot of its drive are supplied as input variables to the first adder 12, which provides the sum a _ sum of the vehicle longitudinal acceleration a _ laengs and the inertial acceleration a _ rot as an output variable.

The sum a _ sum is fed as an input variable, like the maximum permissible acceleration limit a _ zul _ max, to the second comparator 14, which provides a logical HIGH signal as an output signal if the sum a _ sum is greater than the maximum permissible acceleration limit a _ zul _ max. Otherwise, a logical LOW signal is provided.

The two logic signals of the first comparator 6 and the second comparator 14 are supplied as input variables to an and element 8, which provides a logical HIGH signal as an output signal if the two logic signals are HIGH. Otherwise, a logical LOW signal is provided.

The logic output signal of the and element 8 is supplied AS a control signal AS to the controllable changeover switch 10. If the logical output signal of the and element 8 is logically HIGH, the value present at the connection 26 is selected for a quick response of the controller 2 for outputting the fault signal F and supplied to the integrator 22. If, on the other hand, the logical output signal of and element 8 is logically LOW, the value present at terminal 24 is selected for a slow response of controller 2 for outputting fault signal F and fed to integrator 22.

The integrator 22 is configured to: the input signal is integrated (aufintegrieren) and the integrated value (integrator value) is output. The integrator value is limited down to the value present at the input MN and up to the value present at the input MX. The integrator 22 has a selectable amplification factor K, by which the input signal of the integrator 22 is amplified. As soon as the integrator value reaches the value present at the input MX, the integrator outputs the fault signal F.

Furthermore, the vehicle longitudinal acceleration a _ lanngs of the motor vehicle and the inertial acceleration a _ rot of its drive are supplied as input variables to the second adder 16, which in turn accordingly supplies the sum a _ sum as an output variable.

The sum a _ sum and the maximum permissible acceleration limit a _ zul _ max are supplied as input variables to the second subtractor 18, which supplies the evaluation variable G as output variable.

The evaluation variable G is supplied as an input variable to the maximum value determiner 20, which suppresses or filters out negative values of the evaluation variable G. A positive output signal is supplied as a positive evaluation variable x to the integrator 22 as an input variable.

In operation, in a first step, the vehicle longitudinal acceleration a _ laengs is measured, for example, with an acceleration sensor. Furthermore, the axle acceleration a _ axle is determined, for example, by detecting the axle speed or axle rotational speed with subsequent differentiation. Furthermore, the gradient acceleration a _ slope, the inertial acceleration a _ rot and the maximum permissible acceleration limit a _ zul _ max are determined or read in.

In a further step, the axle acceleration a _ axle of the motor vehicle and its maximum gradient acceleration a _ slope are supplied to the first subtractor 4. The first subtractor provides the difference diff _ a _ s as output variable, which is fed to the first comparator 6 as the vehicle longitudinal acceleration a _ laengs, which provides a logical HIGH signal as output signal if the difference diff _ a _ s is greater than the vehicle longitudinal acceleration a _ laengs. Whereby a logical HIGH signal is provided if one or more drive axles of the vehicle slip.

In addition, in operation, in a further step, the vehicle longitudinal acceleration a _ lanngs of the motor vehicle and the inertial acceleration a _ rot of its drive are supplied to the first adder 12. The first adder provides the sum a _ sum as an output variable. The sum a _ sum is fed to the second comparator 14 like the maximum permissible acceleration limit a _ zul _ max, which provides a logical HIGH signal as an output signal if the sum a _ sum is greater than the maximum permissible acceleration limit a _ zul _ max. Thereby providing a logical HIGH signal if one or more drive axles of the motor vehicle unintentionally slip.

In addition, in operation, in a further step, the two logic signals are connected to the and element 8, so that a signal is present at the output of the and element 8 only in the event of an unintentional slipping of at least one drive shaft of the motor vehicle. The logic output signal of the and element 8 is supplied AS a control signal AS to the controllable changeover switch 10, so that for a logic output signal of the and element 8 which is logically HIGH, a fault response parameter y is selected for the rapid response of the controller 2 for outputting a fault signal F and supplied to the integrator 22, which fault response parameter y causes a threshold value of the integrator 22 to be reduced in order to trigger the result of the provision of the fault signal F at the output terminal.

In addition, during operation, the sum a _ sum and the maximum permissible acceleration limit a _ zul _ max are supplied to the second subtractor 18, which supplies an evaluation variable G as an output variable, which is supplied to the maximum value determiner 20. The maximum value determiner 20 suppresses or filters out negative values of the evaluation variable G and provides the positive evaluation variable x as an output signal, which is supplied as an input variable to the integrator 22. The evaluation variable x expresses the severity of the fault, i.e. in the example shown the extent to which the unintentional acceleration includes unintentional slipping.

The integrator 22 integrates the positive evaluation quantity x. In the present example, the integrator values are limited down to the value MN =0 and up to the value MX = y. Outputting the fault signal F if the integrator reaches the upper limit. Depending on whether the value present at the tap 26 for fast response or the value present at the tap 24 for slow response is present at MX as an upper limit, the integrator enters saturation more quickly or more slowly and outputs the fault signal F.

In order to vary the response time T, the amplification factor K may alternatively or additionally be varied as a function of the fault response parameter, in particular K being amplified for fast reactions and K being reduced for slow reactions.

In order to vary the response time T, the fault response parameter may alternatively or additionally be predefined as a function of the evaluation variable. The fault response parameters are advantageously predefined in such a way that a higher evaluation variable leads to a shorter response time.

By means of the invention, the sensitivity of the fault detection is improved in the event of an unintentional slipping of the drive wheels or the drive shaft. At the same time, the tolerance of the error detection is increased in driving situations without adhesion loss and in driving situations in which the drive wheels or the drive shafts are intentionally slipping. Furthermore, the method can be used in a similar manner for detecting a locked drive wheel or drive shaft, for example, due to a locked transmission or due to a too high deceleration torque of the electric drive.

Claims

1. Method for safety monitoring of a drive in a motor vehicle, wherein a fault signal (F) is generated in the event of a fault, having the following steps:

determining whether a fault condition exists in which an unintentional slip rate is present on at least one of the drive shafts of the motor vehicle, and

if an unintentional slip rate is determined on at least one of the drive shafts of the motor vehicle, at least one fault response parameter (y) of a control unit (2) of the motor vehicle is set, wherein the at least one fault response parameter (y) changes a response time (T) of the control unit (2) up to the output of a fault signal (F).

2. Method according to claim 1, wherein, in order to determine whether a fault situation exists, the vehicle longitudinal acceleration (a _ laengs) is compared with a variable that depends on the axle acceleration (a _ axle), and an unintentional slip rate is deduced if the vehicle longitudinal acceleration (a _ laengs) deviates from the variable by a magnitude that is greater than a predeterminable threshold value.

3. Method according to claim 2, wherein the axle acceleration (a _ axle) or the difference (diff _ a _ s) between the axle acceleration (a _ axle) and the gradient acceleration (a _ slope) is used as the axle acceleration (a _ axle) -dependent variable.

4. Method according to claim 2, wherein the axle speed of at least one drive axle of the motor vehicle is evaluated for determining the axle acceleration (a _ axle).

5. Method according to claim 2, wherein an unintentional slip rate is deduced if a variable dependent on the longitudinal acceleration (a _ laengs) of the vehicle deviates from a maximum permissible or minimum permissible acceleration limit (a _ zul _ max) of the motor vehicle by more than a predeterminable threshold value.

6. A method according to claim 5, wherein the vehicle longitudinal acceleration (a _ laengs) or a sum of the vehicle longitudinal acceleration (a _ laengs) and the inertial acceleration (a _ rot) is used as the parameter which depends on the vehicle longitudinal acceleration.

7. Method according to claim 1, wherein an evaluation variable (G) for the fault situation is determined, and wherein the fault signal is output as a function of the evaluation variable (G).

8. Method according to claim 7, wherein a sum (a _ sum) of the vehicle longitudinal acceleration (a _ laenges) and the inertial acceleration (a _ rot) is formed for determining the evaluation variable (G).

9. Method according to claim 8, wherein for determining the evaluation variable (G) a maximum or minimum permissible acceleration limit value (a _ zul _ max) of the motor vehicle is used.

10. Method according to claim 7, wherein a threshold value for the evaluation variable (G) is determined as a function of the fault response parameter (y), wherein the output of the fault signal (F) takes place when the evaluation variable (G) reaches the threshold value.

11. The method according to claim 7, wherein the fault response parameter is predefined as a function of the evaluation variable.

12. A computing unit, which is set up to carry out the method according to one of the preceding claims.

13. A machine-readable storage medium having stored thereon a computer program which, when executed on a computing unit, causes the computing unit to carry out the method according to any one of claims 1 to 11.