DE102015212948A1 - Drive torque compensation in μ-split situations - Google Patents

Abstract

A method for improving the acceleration behavior of a vehicle is described. The vehicle has a vehicle dynamics control function configured to apply a braking torque to a driven wheel of the vehicle to reduce slippage of the driven wheel. The method includes determining an index that a first driven wheel of the vehicle is on a first lane side that allows less frictional engagement with the first driven wheel than a second lane side with a second driven wheel of the vehicle. In addition, the method includes determining, based on the index, whether a μ-split situation exists. The method further includes determining a requested desired drive torque, and determining a brake torque that is caused by the vehicle dynamics control function on the first driven wheel. Furthermore, if it has been determined that there is a μ-split situation, the method comprises driving a drive motor of the vehicle such that the drive motor provides a brake compensation torque in addition to the desired drive torque, wherein the brake compensation torque depends on the determined brake torque ,

Description

The invention relates to a method and a corresponding device for controlling the drive torque of a vehicle, in particular in μ-split situations.

By traction, braking or stability control systems, such. As the traction control (ASR), the Automatic Stability Control (ASC), the Dynamic Stability Control (DSC), the Electronic Stability Program (ESP or ESC), etc., receives the driver of a vehicle in addition to the stability gain in driving u. a. also on the traction side assistance during starting and / or when accelerating the vehicle. This applies in particular when the vehicle is on a smooth road surface or on a roadway with non-uniform or vehicle-side different coefficient of friction distribution (that is to say in a so-called μ-split situation). In such driving situations, the o. G. Vehicle dynamics control systems for traction increase a targeted brake intervention on one or more wheel brakes of the vehicle to reduce slippage of the respective wheels.

The o. G. Interventions to stabilize a vehicle on lanes with low and / or inhomogeneous coefficient of friction can lead to uncomfortable and / or unfamiliar situations for the driver in the control of the vehicle, especially when starting and / or when accelerating the vehicle.

DE 10 2006 026 626 A1 and DE 10 2006 021 652 A1 describe systems in which in a starting situation on an inclined μ-split lane a parking brake function is smoothly transferred to a traction control function, in particular to prevent a rollback of a vehicle and to cause traction for starting the vehicle. In the DE 10 2006 026 626 A1 and DE 10 2006 021 652 A1 However, systems described may cause a vehicle behavior that deviates from the expectation of a driver (in particular with respect to the acceleration behavior of the vehicle).

The present document addresses the technical problem of improving the comfort and predictability of vehicle behavior when starting and / or accelerating a vehicle.

The object is solved by the independent claims. Advantageous embodiments are u. a. in the dependent claims.

According to one aspect, a method is described for improving the acceleration behavior of a vehicle, in particular a two-lane road vehicle. In this case, the vehicle has a vehicle dynamics control function, which is set up to effect a braking torque on a driven wheel of the vehicle in order to reduce slippage of the driven wheel. The vehicle dynamics control function may in particular be an electronic stability program and / or a traction control, d. H. a traction control function.

The method includes determining an index that a first driven wheel of the vehicle is on a first lane side that allows less frictional engagement with the first driven wheel than a second lane side with a second driven wheel of the vehicle. In this case, the first and the second driven wheel may be located on a common driven axle (eg on a rear axle or on a front axle) of the vehicle. The method may include determining speed sensor data of speed sensors of the first driven wheel and the second driven wheel to determine the index. The wheels may rotate in response to a requested desired drive torque (see below). The indicia can then be determined on the basis of the speed sensor data. For example, the indicia may be determined based on the difference in rotational speeds and / or based on a ratio of rotational speeds of the first driven wheel and the second driven wheel.

The method further comprises determining, based on the index, whether a μ-split situation exists. For example, it may be determined that there is a μ-split situation when the ratio of the speeds of the first driven wheel and the second driven wheel is greater or less than a predefined ratio threshold, respectively.

The method also includes determining a requested desired drive torque. The desired drive torque may be requested by a driver of the vehicle. In this case, determining a setpoint drive torque may comprise determining a deflection of an accelerator pedal of the vehicle. The desired drive torque typically depends on the deflection of the accelerator pedal of the vehicle. Alternatively or additionally, the desired drive torque can be requested from a driver assistance function (eg from Automatic Cruise Control, ACC).

Furthermore, the method comprises determining a braking torque, which by the Driving dynamics control function is effected on the first driven wheel. In particular, the vehicle dynamics control function may be configured to effect a braking torque on the first driven wheel (which is on the first lower friction coefficient side roadway) to effectively provide a locking moment similar to a transverse lock on a driven axle of the vehicle cause, on which the first and the second driven wheel are arranged. Thus, a drive torque of a drive motor of the vehicle may be caused to be at least partially transmitted to the second driven wheel (which is on the second higher friction coefficient road side), so that the vehicle is accelerated.

In addition, the method comprises controlling the drive motor of the vehicle such that the drive motor provides a brake compensation torque in addition to the desired drive torque, wherein the brake compensation torque depends on the determined brake torque. In this case, the provision of the additional brake compensation torque also takes place with a constant requested desired drive torque (eg with a constant deflection of the accelerator pedal). An amount of the brake compensation torque may be equal to or less than an amount of the detected brake torque. In other words, the drive motor may be made to additionally and automatically increase the drive torque generated by the drive motor to at least partially compensate for the brake torque applied to the lower friction wheel. The drive motor can (possibly only then) as o. G. be driven, if it was determined that a μ-split situation exists.

In the presence of a μ-split situation, an additional brake compensation torque can thus be provided by the drive motor in an automatic manner. The additional brake compensation torque compensates at least partially for a braking torque caused by the vehicle dynamics control function. Thus, it can be achieved that a drive torque available for the traction or acceleration of the vehicle largely coincides with the desired drive torque expected by the driver. As a result, the behavior of the vehicle can be made to largely meet the driver's expectations, so that the expected traction performance of the vehicle and the comfort to the driver (particularly when starting on a μ-split lane) are improved.

The additional brake compensation torque can be generated in particular with unchanged deflection of the accelerator pedal of the vehicle. As stated above, an actual displacement of the accelerator pedal may indicate that the driver is requesting the desired drive torque. If there is a μ-split situation and the vehicle dynamics control function is activated, this would be the case (eg when using the systems DE 10 2006 026 626 A1 and DE 10 2006 021 652 A1 ) lead to the fact that the traction of the vehicle is only effected by a reduced drive torque, wherein the reduced drive torque of the difference of the desired drive torque and, caused by the vehicle dynamics control function, braking torque (or locking torque) corresponds. The vehicle behavior would thus deviate from the expectation of a driver.

As described above, the drive motor can therefore be made to generate the brake compensation torque in addition to the desired drive torque and with unchanged displacement of the accelerator pedal, so that the traction of the vehicle by the effective sum of target drive torque, braking torque of the vehicle dynamics control function and brake compensation torque is effected. In particular, can be achieved with appropriate dimensioning of the brake compensation torque that the traction of the vehicle is effectively effected by the desired drive torque. It can thus be achieved that the actual traction of the vehicle (possibly nearly) corresponds to the traction the vehicle would have with the current displacement of the accelerator pedal on a roadway with homogeneous coefficients of friction. The vehicle behavior thus corresponds to the expectations of the driver.

In a concrete example, the desired drive torque is determined at a certain time via the deflection of the accelerator pedal. If necessary, the drive motor can then be activated to effect the desired drive torque. Furthermore, it is then determined which braking torque is caused by the driving dynamics control function in response to the target driving torque or would be effected to reduce slippage of the first driven wheel. If necessary, this can be determined on the basis of the one or more characteristic curves. The braking torque caused by the vehicle dynamics control function is typically dependent on the requested desired drive torque. Furthermore, the braking torque caused by the driving dynamics control function typically depends on the coefficients of friction of the road surface (ie on the properties of the μ-split situation). Then, the drive motor is driven, in addition to the requested desired drive torque (and with unchanged deflection of the accelerator pedal) to generate the brake compensation torque to compensate for the braking torque caused by the vehicle dynamics control function at least partially. This activation is preferably carried out as soon as possible after the above-mentioned specific time at which the requested desired drive torque was determined (eg 100 ms, 10 ms or less after the specified time).

The height of the brake compensation torque can optionally be determined as a function of one or more predefined characteristic curves. In this case, a characteristic curve can indicate which braking torques are effected at different drive torques and / or with different properties of the μ-split situation by the vehicle dynamics control function.

The generation of a brake compensation torque may depend on a driving speed of the vehicle. In particular, the brake compensation torque may be effected only when the vehicle's vehicle speed is less than or equal to a predefined vehicle speed threshold (eg, 20 km / h). For higher driving speeds, generation of the brake compensation torque can be prevented. In this case, if necessary, in a transitional region as a function of the driving speed, the height of the generated brake compensation torque can be reduced to zero (in order to provide a smooth transition). By a vehicle speed-dependent generation of the brake compensation torque, the vehicle behavior can be modified dedicated for starting situations. On the other hand, a behavior of the vehicle which is typically known to the driver can be maintained at higher driving speeds.

The method may further include determining a driving resistance of the vehicle. The determination of a driving resistance can in particular include the determination of inclination sensor data of a tilt sensor and / or a longitudinal acceleration sensor of the vehicle. The driving resistance can then be determined on the basis of the inclination sensor data. It can thus be determined in particular that the vehicle is on a longitudinally inclined roadway, and therefore there is a relatively high driving resistance. When accelerating and especially when starting a vehicle on an inclined μ-split roadway, there are particularly strong deviations between the (set by the driver) target drive torque and the actual available drive torque. These deviations can be perceived as uncomfortable by a driver of the vehicle, since the vehicle behavior does not correspond to the expected behavior, eg. As the behavior at a level roadway, corresponds.

The drive motor of the vehicle can therefore be controlled such that the drive motor in addition to the desired drive torque (and in addition to the brake compensation torque) provides a resistance compensation torque, wherein the resistance compensation torque depends on the determined driving resistance. In particular, an amount of the resistance compensation torque may be equal to or less than an amount of the running resistance. Thus, by the drive motor (in particular in the presence of a μ-split situation) the driving resistance (eg due to the inclination of the road) can be at least partially compensated, so that the vehicle behaves according to the expectation of a driver of the vehicle.

The method may further include determining if the driving resistance is greater than or equal to a predefined road resistance threshold. The drive motor may be driven (possibly only) to provide the resistance compensation torque when the drive resistance is greater than or equal to a predefined travel resistance threshold.

In another aspect, a control unit for controlling a drive motor of a vehicle is described. The vehicle includes a vehicle dynamics control function configured to apply a braking torque to a driven wheel of the vehicle to reduce slippage of the driven wheel. The control unit is configured to determine an indication that a first driven wheel of the vehicle is located on a first lane side, which allows a lower adhesion to the first driven wheel, as a second lane side with a second driven wheel of vehicle. In this case, the first driven wheel and the second driven wheel are typically located on a common driven axle (eg, a rear axle or a front axle) of the vehicle. The control unit is further set up to determine on the basis of the index whether a μ-split situation exists.

In addition, the control unit is configured to determine a requested target drive torque, as well as to determine a brake torque, which is caused by the vehicle dynamics control function on the first driven wheel. Furthermore, the control unit is set up, when it has been determined that there is a μ-split situation, to control the drive motor of the vehicle such that the drive motor provides a brake compensation torque in addition to the desired drive torque, the brake compensation torque depending on the determined brake torque ,

According to a further aspect, a road motor vehicle (in particular a two-lane road motor vehicle, for example a passenger car or a lorry) is described which comprises the control unit described in this document.

In another aspect, a software (SW) program is described. The SW program may be set up to run on a processor (eg, on a control unit of a vehicle) and thereby execute the method described in this document.

In another aspect, a storage medium is described. The storage medium may include a SW program that is set up to run on a processor and thereby perform the method described in this document.

It should be understood that the methods, devices and systems described herein may be used alone as well as in combination with other methods, devices and systems described in this document. Furthermore, any aspects of the methods, apparatus, and systems described herein may be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

Furthermore, the invention will be described in more detail with reference to exemplary embodiments. Show

1 an exemplary vehicle in a μ-split situation;

2 an effective drive torque for a vehicle in a μ-split situation; and

3 a flowchart of an exemplary method for compensation of a braking torque.

As stated earlier, the present document is concerned with enhancing comfort and providing traceable vehicle behavior in situations where low and / or inhomogeneous road surface friction values exist. In this context shows 1 a block diagram of exemplary components of a vehicle 100 ,

The vehicle 100 includes a front axle 110 with a first (left) wheel 111 and a second (right) wheel 112 and a rear axle 120 with a first (left) wheel 121 and a second (right) wheel 122 , The vehicle 100 further comprises a drive motor 104 (For example, an internal combustion engine and / or an electric machine), through which a torque is generated, which typically has an axle differential 123 on the respective wheels 121 . 122 the rear axle 120 can be transferred. The axle differential 123 allows a speed compensation between the wheels 121 . 122 the rear axle 120 , This applies analogously to a front-wheel drive vehicle and / or a four-wheel drive vehicle 100 ,

The vehicle 100 further includes one or more brakes 125 . 126 for the respective wheels 121 . 122 the rear axle 120 , The brake 125 . 126 may each comprise one or more friction brakes and / or operated as generators electrical machines.

Furthermore, the vehicle includes 100 a variety of sensors 105 that are set up to provide sensor data. The sensor data, for example, a speed of a wheel 121 . 122 and / or an inclination of the vehicle 100 Show.

In addition, the vehicle includes 100 a control unit 101 (eg as part of an engine control unit). The control unit 101 is arranged to provide a vehicle dynamics control function to the stability and / or traction of the vehicle 100 to improve in certain driving situations. As part of the driving dynamics control function can intervene on the wheel brakes 125 . 126 done to a slip of a wheel 121 . 122 to reduce and / or to a certain distribution of the torque of the drive motor 104 on the first and second wheel 121 . 122 the rear axle 120 to effect.

In particular, an asymmetric application of a braking torque to the wheels 121 . 122 on the drive axle 120 a locking effect can be accomplished, which in turn distributes the torque to the wheels 121 . 122 is effected. This is the faster turning first wheel 121 braked and according to the applied braking torque is drive torque on the opposite side (ie on the second wheel 122 ) and can be used there for vehicle traction.

In a traction-controlled starting or accelerating the vehicle 100 , ie when starting or accelerating the vehicle 100 using a vehicle dynamics control function, it can occur, in particular on a μ-split roadway, in situations where a driver of the vehicle 100 must set a relatively high accelerator pedal preset to the desired acceleration of the vehicle 100 to effect. This effect is particularly strong in the presence of a relatively high road resistance (such as when driving on a sloping (ie, rising) road). This can lead to uncertainty and thus to reduced comfort for the driver of the vehicle 100 to lead. In particular, in such situations the Acceleration pedal default usually be chosen much higher than the driver is usually used in a similar situation (especially in the absence of a μ-split lane).

This in 1 illustrated vehicle 100 is on a roadway 130 , The roadway 130 has a first lane side 131 with a first coefficient of friction and a second roadway side 132 with a second coefficient of friction with respect to the respective wheels 111 . 121 respectively. 112 . 122 on. The first wheels 111 . 121 are on the first lane side 131 and the second wheels 112 . 122 are on the second lane side 132 , The first coefficient of friction and the second coefficient of friction (ie, the respective coefficients of friction) may be substantially different. For example, the coefficients of friction may differ by 1, 2 or more orders of magnitude. Such an inhomogeneous coefficient of friction situation is referred to as μ-split situation.

Acceleration in a μ-split situation typically causes the driven wheel 121 (In the following example, the first rear wheel 121 ) on the road side 131 with the lower first coefficient of friction a high slip to the road 130 (ie that the first wheel 121 by turns). As a result, there is no or only a reduced traction of the vehicle 100 because the total torque of the drive motor 104 is used to the first rear wheel 121 drive. A vehicle dynamics control function is typically set up, the first wheel brake 125 to induce a braking torque on the first wheel 121 to effect that by a drive motor 104 generated torque can be used at least partially, the second wheel 122 (on the second lane side 132 with the relatively high second coefficient of friction), and thus the vehicle 100 to accelerate.

That of the drive motor 104 However, generated drive torque is not completely for the acceleration of the vehicle 100 available, like out 2 is apparent. 2 shows that of the drive motor 104 generated moment 202 as a function of deflection 201 of the accelerator pedal (see drive torque curve 211 ). Furthermore shows 2 exemplary the course 212 the braking torque 202 that has one or more wheels 121 of the vehicle 100 to stabilize the vehicle 100 is generated (see braking torque curve 212 ). In total, this results in the difference as an effective drive torque (see effective drive torque curve 213 ), which is used for the acceleration of the vehicle 100 is available. The effective drive torque is thus below the drive torque, which is the driver of the vehicle 100 over the deflection 201 of the accelerator pedal has specified. This leads to a reduced comfort for the driver.

In other words, the vehicle 100 requires an additional drive torque to overcome (compensation) of the individual wheels 121 applied braking torque, the generation of a locking torque on the / the drive axles 120 is produced. As a result fit, especially in driving situations with a relatively high driving resistance, the driver specification (in particular the deflection 201 the accelerator pedal), the resulting expectation of the driver with respect to the resulting traction of the vehicle 100 and the actually devoted trakion of the vehicle 100 not together.

The control unit 101 of the vehicle 100 may be configured to avoid such deviations, the reduction of the drive torque given by the driver 211 by the braking torque caused by the vehicle dynamics control function 212 at least partially compensate. In particular (depending on the currently set braking torque or locking torque 212 ) on the drive wheels 121 . 122 a compensation of the drive torque are made in such a way that the driver specified desired torque 211 according to his accelerator pedal specification 201 automatically increased by a variable amount. By means of this drive torque increase, a compensation of the means of the wheel brakes 125 applied braking torque 212 be made. This torque increase can be made within the driving dynamics control function.

Furthermore, upon detection of a hanging situation (eg based on the sensor data of a tilt sensor 105 ) roadway inclination dependent compensation of the slope output torque can be made. In other words, based on sensor data, a running resistance (eg a degree of inclination) can be determined. Furthermore, the drive torque increase can be made as a function of the determined driving resistance.

3 shows a flowchart of an exemplary method 300 for improving the acceleration behavior (in particular the starting behavior) of a vehicle 100 , The vehicle 100 has a vehicle dynamics control function that is set, a braking torque 212 on a driven wheel 121 of the vehicle 100 to cause a slippage of the driven wheel 121 to reduce. The procedure 300 includes determining 301 an index indicating that there is a first driven wheel 121 of the vehicle 100 on a first lane side 131 is the one lower Traction with the first driven wheel 121 allows, as a second lane side 132 with a second driven wheel 122 of the vehicle 100 , This can be z. B. based on the wheel speeds of the first and second driven wheel 121 . 122 be determined. It can then be determined based on the index (step 302 ), if there is a μ-split situation. For example, it may be determined that there is a μ-split situation when a ratio or a difference of the wheel speeds of the first and second driven wheels 121 . 122 exceeds or falls below a predefined threshold.

The procedure 300 further includes determining 303 one, by a driver of the vehicle 100 and / or by a driver assistance function of the vehicle 100 requested, desired drive torque 211 , as well as determining 304 a braking torque 212 by the driving dynamics control function on the first driven wheel 121 is effected. Furthermore, the method includes 300 the driving 305 a drive motor 104 of the vehicle 100 such that the drive motor 104 in addition to the desired drive torque 211 provides a brake compensation torque, wherein the brake compensation torque of the determined braking torque 212 depends. The provision of the brake compensation torque takes place (if necessary only) if it has been determined that there is a μ-split situation.

It should be noted that the order of the above-mentioned process steps may vary. In particular, in a first step, the desired drive torque 211 determined (eg in response to the deflection 201 an accelerator pedal). Thereupon the presence of a μ-split situation can be determined (eg based on the fact that the first wheel 121 (compared to the second wheel 122 ) has a relatively high slip). Alternatively or additionally, z. B. by using sensors 105 (eg by optical scanning of the road 130 ) a μ-split situation are detected, even before a target drive torque 211 is determined.

The measures described in this document give a driver when starting and / or accelerating on lanes with different adhesion conditions (friction coefficient conditions) between tire and roadway a comparable and better predictable for the driver vehicle behavior. This is especially true for longitudinally inclined roads.

The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended to illustrate only the principle of the proposed methods, apparatus and systems.

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 102006026626 A1 [0004, 0004, 0014]
• DE 102006021652 A1 [0004, 0004, 0014]

Claims (10)

Procedure ( 300 ) for improving the acceleration behavior of a vehicle ( 100 ), where the vehicle ( 100 ) has a driving dynamics control function which is set up, a braking torque ( 212 ) on a driven wheel ( 121 ) of the vehicle ( 100 ) to cause slippage of the driven wheel ( 121 ), the process ( 300 ), - determining ( 301 ) of an index indicating that a first driven wheel ( 121 ) of the vehicle ( 100 ) on a first lane side ( 131 ), which has a lower adhesion to the first driven wheel ( 121 ), as a second lane side ( 132 ) with a second driven wheel ( 122 ) of the vehicle ( 100 ); - Determine ( 302 ), based on the index, whether a μ-split situation exists; - Determine ( 303 ) of a requested by a driver of the vehicle target drive torque ( 211 ); - Determine ( 304 ) of a braking torque ( 212 ), which by the vehicle dynamics control function on the first driven wheel ( 121 ) is effected; and - if it has been determined that a μ-split situation exists, triggering ( 305 ) of a drive motor ( 104 ) of the vehicle ( 100 ) such that the drive motor ( 104 ) in addition to the desired drive torque ( 211 ) provides a brake compensation torque, wherein the brake compensation torque of the determined braking torque ( 212 ) depends. Procedure ( 300 ) according to claim 1, wherein an amount of the brake compensation torque equal to or smaller than an amount of the determined braking torque ( 212 ). Procedure ( 300 ) according to any one of the preceding claims, wherein the determining ( 302 ) of a desired drive torque ( 211 ), determining a deflection ( 201 ) of an accelerator pedal. Procedure ( 300 ) according to one of the preceding claims, further comprising, - determining a driving resistance of the vehicle ( 100 ); and - driving the drive motor ( 104 ) such that the drive motor ( 104 ) in addition to the desired drive torque ( 211 ) provides a resistance compensation torque, wherein the resistance compensation torque depends on the determined travel resistance. Procedure ( 300 ) according to claim 4, wherein determining a driving resistance comprises, - determining tilt sensor data of a tilt sensor and / or a longitudinal acceleration sensor ( 105 ) of the vehicle ( 100 ); and determining the road resistance on the basis of the tilt sensor data. Procedure ( 300 ) according to one of claims 4 to 5, wherein an amount of the resistance compensation torque is equal to or less than an amount of the running resistance. Procedure ( 300 ) according to one of the preceding claims, wherein - the method ( 300 ), determining a driving speed of the vehicle ( 100 ); and - the brake compensation torque is provided as a function of the driving speed. Procedure ( 300 ) according to one of the preceding claims, wherein the vehicle dynamics control function comprises an electronic stability program and / or a traction control system. Procedure ( 300 ) according to one of the preceding claims, wherein - the method ( 300 ), determining speed sensor data from speed sensors ( 105 ) of the first driven wheel ( 121 ) and the second driven wheel ( 122 ); and - the indicia is determined based on the speed sensor data. Control unit ( 101 ) for controlling a drive motor ( 104 ) of a vehicle ( 100 ); the vehicle ( 100 ) has a driving dynamics control function which is set up, a braking torque ( 212 ) on a driven wheel ( 121 ) of the vehicle ( 100 ) to cause slippage of the driven wheel ( 121 ), the control unit ( 101 ) is set up to detect an indication that a first driven wheel ( 121 ) of the vehicle ( 100 ) on a first lane side ( 131 ), which has a lower adhesion to the first driven wheel ( 121 ), as a second lane side ( 132 ) with a second driven wheel ( 122 ) of the vehicle ( 100 ); - to determine on the basis of the index whether a μ-split situation exists; A desired drive torque requested by a driver of the vehicle ( 211 ) to determine; A braking torque ( 212 ) determined by the vehicle dynamics control function on the first driven wheel ( 121 ) is effected; and - if it has been determined that there is a μ-split situation, the drive motor ( 104 ) of the vehicle ( 100 ) in such a way that the drive motor ( 104 ) in addition to the desired drive torque ( 211 ) provides a brake compensation torque, wherein the brake compensation torque of the determined braking torque ( 212 ) depends.

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