WO2002062640A1

WO2002062640A1 - Method and device for travel direction detection

Info

Publication number: WO2002062640A1
Application number: PCT/EP2002/000218
Authority: WO
Inventors: Joachim Borneis; Ulrich Baiter
Original assignee: Continental Teves Ag & Co. Ohg; FÜHRER, Jochen
Priority date: 2001-01-11
Filing date: 2002-01-11
Publication date: 2002-08-15
Also published as: EP1351844A1; DE10290366B4; DE10290366D2

Abstract

The invention relates to a method and to a device for detecting the travel direction of a vehicle during starting up or starting to roll and/or during the down-hill travel of a vehicle, especially with HDC (hill descent control) that keeps the vehicle speed constant or limits it during hill descent by influencing the service brake. The invention is further characterized in that the direction of travel is detected on the basis of internal and/or external vehicle parameters, such as engine speed, engine torque, accelerator pedal position, selected gear, gear-shift state, rotational behavior of the wheels, lateral acceleration, road pitch, by correlating at least two parameters. The parameters to be correlated are chosen in accordance with a status detection of the vehicle parameters and/or when the vehicle parameters satisfy certain conditions with respect to their variation in time.

Description

Method and device for direction detection

The invention relates to a method and a device for detecting the direction of travel of a vehicle, in particular when used in an HDC control (HDC = Hill Descent Control), which keeps or limits the vehicle speed when driving uphill by influencing the service brake.

When starting a vehicle on a hill, the engine operating conditions change, among other things, in such a way that the engine changes from idling behavior (unloaded run) to normal operation (loaded run) by the engine driving the vehicle, so that the engine output power is largely and particularly defined to drive the Vehicle is used. When the vehicle is driving downhill, the speed depends on the position of the accelerator pedal, the gear engaged, the engine drag torque and the gradient (slope of the road). On steep descents, the engine drag torque is often not sufficient to allow a controlled descent. There are therefore already known devices by means of which the vehicle can be kept on a downhill gradient by automatically actuating the brakes at a constant speed desired by the driver. Such vehicles are usually equipped with an anti-lock braking system (ABS) and a traction control system (ASR). The already existing assemblies such as electronics, wheel speed sensors, Longitudinal acceleration sensors, solenoid control valves, motor-pump units etc. are also used to carry out the above-mentioned speed control. The known assemblies relieve the driver on downhill gradients of having to constantly press the brake pedal. A constant speed is maintained even with different road inclinations.

From WO 96/11826 AI it is known to equip a vehicle with a so-called mountain descent control (also referred to as HDC = Hill Descent Control). This type of control can be switched on by the driver using a switch. The above Regulation is able to keep the vehicle on a steep downhill gradient at a constant, low speed by means of active, driver-independently controlled braking without the driver having to apply the brakes. This system is especially designed for off-road vehicles that drive on a downhill slope, where the engine drag torque is no longer sufficient to decelerate the vehicle, even in the lowest gear.

Knowing the direction of travel is particularly important for control systems such as the HDC in off-road use. For example, the target speed can be specified depending on the direction of travel (slower backwards) or the ABS function can be designed depending on the direction (select low). It is particularly important to receive valid direction information as soon as possible after starting the vehicle. Early directional information is required, especially when rolling with high acceleration (rolling back on a steep slope), since braking intervention by the HDC must take place very soon (at 2-3km / h) if you want to avoid overshooting the speed. On the other hand, it is a rather smooth start (flat slope) not critical if the

Direction information is available late or shows the wrong direction for a limited time.

So far, only the gear recognized by a switch has been used to determine the direction of travel. However, this method is not sufficient in some driving situations (unintentional rolling back on a slope, intentional rolling backwards with the clutch depressed) and leads to incorrect results.

The invention is based on the object of specifying a method and a device of the type mentioned at the outset by means of which a direction of travel detection, in particular on a mountain, can be detected in all driving situations.

This object is achieved with the features of the independent claims. Dependent claims are directed on preferred embodiments of the invention.

According to the invention, the detection of the direction of travel is determined as a function of internal and / or external vehicle variables, such as the engine speed, the engine torque, the accelerator pedal position, the gear engaged, the clutch state, the turning behavior of the wheels, the longitudinal acceleration, the road inclination, by correlating at least two vehicle variables , the selection of the variables to be correlated taking place in accordance with a status determination of the vehicle sizes and / or if the vehicle sizes meet certain conditions with regard to their time profiles.

The status determination of the vehicle sizes aims at speed-determined conditions of the vehicle, such as vehicle standing, vehicle is driven, vehicle is in a load-free run (free rolling) or in one Uphill-braking operation (HDC mode of operation) and / or on the continuation of these conditions for a certain period of time, such as a short standstill of the vehicle, a long standstill of the vehicle.

A further increase in the reliability of the determination of the direction of travel can be achieved by selecting a strategy for recognizing the direction of travel of the vehicle from at least two different strategies depending on the status of the vehicle sizes, which represents the priority of the direction of travel detection determined from the correlated conditions.

The status can be an identification of the respective strategy, a defined sequence of the strategy to be carried out or a prioritization of the respective strategy that is dependent on variable criteria, preferably on the length of time and / or the vehicle state variables.

According to the invention, five different procedures are provided in the direction detection strategies used.

In a first strategy, the detection of the direction of travel by fulfilling the conditions:

Accelerator pedal position (FPed)> threshold (FPedS) ■

Motor torque (MMotor)> Threshold (MMotorS)

Clutch closed

Gear is engaged, determined. If these conditions are met, there is a forward drive when a forward gear (VGang) is engaged and a reverse drive when a reverse gear (RGang) is engaged. As is known, the gear engaged is determined via a switch which is actuated when the gear is engaged. The clutch can also be closed via a Switch signal sensed or model-based, via the

Ratio of engine speed to turning behavior of the wheels (the

Wheel speed), which with regard to the inserted

Gear is assessed, determined. As beneficial

It is possible to carry out a plausibility check of the engaged state by comparing

Engine torque, longitudinal acceleration signal (a) and

To carry out wheel speeds or accelerations.

If the driving resistance does not match the engine torque, there is a disengaged state.

The driving resistance can simply include the downhill drive or additionally a speed-dependent one

Proportion (e.g. determined in experiments):

Driving resistance = vehicle mass * | a | or

Driving resistance = vehicle mass * \ a \ + resistance depending on

wheel speeds

The direction of travel detection is carried out according to a second or further strategy if at least one of the

conditions

FPed> FPedS, MMotor> MMotorS, clutch closed, gear is engaged the first strategy is not fulfilled.

In the second strategy, it is determined as an input condition whether the vehicle stands for a certain minimum time (for example 500 ms). The standstill is recognized by carrying out a first comparison of a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value (FzgS) for the quantity describing the speed of the vehicle. A second comparison is carried out, a difference, which is formed from a filtered aFilt and an unfiltered longitudinal acceleration signal (α), being compared with a characteristic threshold value aSl for a longitudinal acceleration signal. At the first A comparison is determined whether the vehicle speed is below a minimum value. In the second comparison, it is determined whether the longitudinal acceleration signal lies in a defined band, ie is essentially stationary, that is, low-pass filtered and unfiltered signals differ from one another by no more than a threshold value (eg 0.015 g) for a certain time (eg 500 ms). Based on these two comparisons, preferably if the condition VFzg≤ VFzgS is fulfilled and the condition

≤ a S was previously fulfilled over a predefined time, the vehicle is started up or rolled on using a third comparison. Depending on the (low pass) filtered longitudinal acceleration signal (aFilt) and the difference between the (low pass) filtered longitudinal acceleration signal {aFilt) and the unfiltered longitudinal acceleration signal (a) and the comparison of this difference between the longitudinal acceleration signals [aFilt, a) with a characteristic threshold value { as 2). On forward driving (forward driving direction) is recognized when the filtered longitudinal acceleration signal is negative and at least aS2 smaller than the unfiltered longitudinal acceleration signal, and on backward driving (reverse driving direction) when the filtered longitudinal acceleration signal is positive and at least aS2 larger than the unfiltered longitudinal acceleration signal.

If, within a defined time, the wheels turn (the wheel signals) also indicate that the vehicle is starting or coasting, by exceeding a speed threshold VFzgS of the vehicle speed VFzgS, the start detection is confirmed, otherwise the vehicle will move forward when the vehicle is in forward gear Forward driving direction) and with reverse gear engaged (reverse gear) on reverse driving (reverse driving direction), since there is no better knowledge. The vehicle speed is from the Derived rotational behavior of the wheels.

If the condition VFgz <VFgzS is fulfilled, however, the

Condition | αE / 7t -α | <öSl not fulfilled for a predetermined minimum time, the direction of travel detection of the vehicle is carried out according to a third strategy. The direction of travel is determined depending on the last lane gradient saved before standstill (condition VFgz <VFgzS not yet fulfilled). This road gradient is calculated before standstill based on the following direction-dependent relationship:

when reversing sin = ** """ ^{+ θrad} g

otherwise sm a = ^asensor ~ ^aRad determined. G

In the third strategy, forward travel is recognized if the value of the relationship is negative and reverse travel if the

Value of the relationship is positive.

According to a fourth strategy for recognizing the direction of travel, a vehicle acceleration becomes from a quantity describing the wheel speeds

with v = wheel speed, ω = angular velocity, r = wheel radius. This vehicle acceleration is characterized by a characteristic threshold value a _(wheel) S for the

Wheel speeds of the vehicle determined vehicle acceleration compared in terms of amount and determined the direction of travel from an unfiltered longitudinal acceleration signal a according to the comparison. When the vehicle is in a downhill driving state at which the vehicle speed is high Influencing the service brake is kept constant or limited (HDC operation) and the model-based brake pressure is> a corresponding threshold value, it is recognized when driving backwards if there is a positive longitudinal acceleration signal for a predetermined minimum time, and when driving for a predetermined minimum time when forward driving is detected negative longitudinal acceleration signal is present.

It is advantageous that, according to a fifth strategy, the direction of travel is maintained, which was determined according to one of the previous strategies in the last cycle, if none of the previous strategies for detecting the direction of travel is carried out in the current cycle.

According to the invention, a generic device for detecting the direction of travel of a vehicle is designed in such a way that the device recognizes means for detecting the direction of travel as a function of internal and / or external vehicle variables, such as the accelerator pedal position, the engine speed, the engine torque, the gear engaged, the clutch state, and the rotational behavior of the vehicle Wheels, the longitudinal acceleration, the road inclination, and also evaluation means for correlating at least two variables and for selecting the variables to be correlated according to a status determination of the vehicle sizes and / or if the vehicle sizes meet certain conditions with regard to their time profiles.

Advantageous developments of the invention are specified in the subclaims.

An embodiment of the invention is shown in the drawing and is described in more detail below. s show

Fig. 1 schematically shows a vehicle in plan view

Fig. 2 shows a diagram of the detection of the direction of travel

Fig. 3 shows a flow diagram of the first strategy for

Direction recognition

Fig. 4 shows a flow chart of the second strategy for

Direction recognition

Fig. 5 shows a flow chart of the third strategy for

Direction recognition

Fig. 6 is a flowchart of the fourth strategy

Fig. 7 shows a flow chart of the state transitions between the

Strategies (status determination)

Fig. 1 shows schematically a vehicle in plan view in which the invention can be applied. 101 to 104 are the wheels of the vehicle (front left, front right, rear right and rear left), 105, 106 the axles of the vehicle, 111 to 114 each assigned wheel sensors, 121 to 124 each wheel brakes, purple to 114a are signal lines that enter the signals of the wheel sensors 111 to 114 of a controller 130 in the broadest sense. The controller 130 receives input signals from a longitudinal acceleration sensor 115, a clutch switch 116, a gear switch 117 and from the engine control unit 110 and from an accelerator pedal sensor, not shown, if this signal is not generated in the engine control unit based on a model. It generates output signals 131 with which the brakes 121 to 124 can be addressed, for example. In addition, the drive torque can also be adjustable by influencing the motor.

The direction of travel detection 130 according to FIG. 1 uses the input signals, which are usually in an ABS (Anti-lock braking system) / 4BTCS (4-wheel brake intervention drive slip control system) / HDC vehicle are available:

• Wheel speeds

• longitudinal acceleration signals

• Engine information (speed, torque, accelerator pedal position)

• Gear switch information

• Clutch switch information

Depending on the situation, these are evaluated according to certain rules in such a way that the correct direction of travel is determined with the greatest possible probability. By means of an HDC control, a cruise control function (automatic speed setting) is implemented using the determined direction of travel. The determined direction of travel can, however, also be used for other purposes.

It is provided that the direction of travel is permanently recorded and saved depending on the situation. For this purpose, five procedures are provided for the selection of the five direction of travel detection strategies that are used, which determine the direction of travel of the vehicle in a model as a function of internal and / or external vehicle sizes.

FIG. 3 schematically shows the first strategy, which, with a corresponding status determination 710 (FIG. 7), provides for determining the direction of travel via the gear stage. The vehicle travels in the direction corresponding to gear level 310 or 320. If the V gear is determined via the gear switch information, the forward drive 315 or the reverse gear 325 is determined.

FIG. 4 schematically shows the second strategy, which provides 720 (FIG. 7) for a corresponding status determination Decide forward travel 415 if the relationship a-aS2> aFilt and 0> aFilt (block 410) and reverse travel if the relationship a + aS2 <aFilt and 0 <aFilt (block 420), with a = longitudinal acceleration signal of the longitudinal acceleration sensor 115, aFilt = (low pass) filtered longitudinal acceleration signal. In block 440, it is determined whether the approach detection, determined according to strategy two by evaluating the longitudinal acceleration signals a, aFilt of the vehicle, is confirmed by the vehicle speed obtained from the wheel signals 111-114. For this purpose, a waiting time expires in block 430. In block 440, the vehicle speed VFzg is then compared with a corresponding threshold value VFzgS. If VFzg> VFzgS, the determined direction of travel is confirmed. If the VFgz is below the threshold VFzgS, the direction of travel is determined and confirmed using an auxiliary variable. In 450 and 460 it is queried whether the forward gear V gear or reverse gear R gear is engaged. If the V-gear is engaged, the forward drive is confirmed, if the R-gear is engaged, the reverse drive is confirmed.

FIG. 5 schematically shows the third strategy, which, with a corresponding status determination 730 (FIG. 7), provides direction of travel detection, which is based on the permanent determination of the road gradient while the vehicle is traveling. Block 510 determines whether or not there is a reverse drive.

The road gradient is calculated and saved outside the first or second strategy (i.e. while driving) according to the following relationship:

when reversing sin a = ^{ÜSensor + ÜRad} ga „—a„ _^ else, sιnα = ^a Sensor ^a Rad g

After the third strategy, a query is made in block 540 as to whether there is a stored positive slope signal. This is because if reverse travel is determined (block 550), if there is no positive incline signal, the stored negative incline signal is queried in block 560 and, if present, forward travel (block 570) is determined.

FIG. 6 schematically shows the fourth strategy, which, with a corresponding status determination 740 (FIG. 7), provides direction of travel detection, which determines in block 610 via the turning behavior of the wheels 111-114 whether the vehicle acceleration determined from the wheel speeds according to dv dω a _wheel = -r ^od ea _Rad = - * r dt dt with v = wheel speed, ω = angular velocity, r = wheel radius, is small. For this, a _wheel with a characteristic

Threshold a _wheel S compared in terms of amount. If according to the diamond

615 the relationship

<a _wheel S ist, the direction of travel is determined based on the comparison from the unfiltered longitudinal acceleration signal a. If a positive longitudinal acceleration signal is present in block 620 for a specified minimum time, then 625 is recognized when reversing, and a negative signal is present for a defined minimum time

Longitudinal acceleration signal 630, 635 is detected on forward travel.

The case that the motor works against the brake, and thus e.g. in a vehicle with an automatic transmission, the target speed drops below idle speed, can be excluded by minimum thresholds with longitudinal acceleration and / or model brake pressure.

With a corresponding status determination 750 (FIG. 7), a fifth strategy is provided, according to which the direction of travel is maintained, which was determined according to one of the previous strategies in the last cycle, if none of the strategies for direction detection in the current cycle.

Figure 7 shows schematically the priorities for status transitions. One of the strategies for detecting the direction of travel of the vehicle is determined depending on the status of the vehicle sizes, which represents the priority of the direction of travel detection determined from the correlated conditions. The status is determined cyclically (loop-by-loop), with one status change per loop.

The state transitions are described below: The state transition from the third or the second strategy follows the first strategy if the conditions (according to block 731 or 721)

Accelerator Pedal (FPed)> Threshold (FPedS)

Motor torque (MMotor)> Threshold (MMotorS)

Clutch closed (Kg)

Gear is engaged (V gear, R gear) are fulfilled.

The state transition from the third or second strategy to the fifth strategy takes place if at least one of the conditions for the transition to the first strategy is not met and a comparison result (according to block 732 or 722) from a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value (VFzgS) for the quantity describing the speed of the vehicle represents a vehicle speed lying above or above the value of the threshold value.

The state transition from the third strategy to the second strategy takes place if at least one of the conditions for the transition to the first strategy and the condition for the transition into the fifth strategy is not fulfilled and a comparison result (according to block 733 or 723) from a comparison carried out as a function of a filtered (aFilt) and an unfiltered longitudinal acceleration signal (α) shows a longitudinal acceleration signal lying in a defined band for a certain time. To make the comparison, a difference between the filtered {aFilt) and the unfiltered

Longitudinal acceleration signal (a) is formed and the amount is compared with a characteristic threshold value (aS \). The comparison determines whether the conditions

| aFilt -a \ ≤ aS \ are fulfilled.

The state transition from the first strategy to the fifth

Strategy takes place if at least one of the conditions (according to

Block 711)

Accelerator pedal (FPed) <threshold value (FPedS) engine torque (MMotor) <threshold value (MMotorS) clutch open is fulfilled.

The state transition from the fourth strategy to the third strategy takes place when the vehicle is not in a downhill driving state in which the vehicle speed is kept constant or limited by influencing the service brake (HDC operation) or a comparison result of a model-based brake pressure with a corresponding threshold value represents a brake pressure below the threshold value (according to block 741) and a comparison result (according to block 742) of a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value (VFzgS) for the Describing the speed of the vehicle represents a vehicle speed below the threshold.

The state transition from the fourth strategy to the first strategy takes place when the vehicle is not in a downhill driving state in which the vehicle speed is kept constant or limited by influencing the service brake (HDC operation) or a comparison result of a model-based brake pressure with a corresponding brake value represents a brake pressure below the threshold value and a comparison result (according to block 742) of a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value (VFzgS) of the quantity describing the speed of the vehicle a vehicle speed lying on or above the threshold value and the conditions (according to block 743)

Accelerator Pedal (FPed)> Threshold (FPedS)

Motor torque (MMotor)> Threshold (MMotorS)

Clutch closed (Kg)

Gear is engaged (V gear, R gear) are fulfilled.

The state transition from the fifth strategy to the first strategy takes place if the conditions (according to block 751)

Accelerator Pedal (FPed)> Threshold (FPedS)

Motor torque (MMotor)> Threshold (MMotorS)

Clutch closed (Kg)

Gear is engaged (V gear, R gear) are fulfilled.

The transition from the fifth strategy to the fourth strategy takes place if at least one of the conditions for the transition to the first strategy is not met and if there are the vehicle is in a downhill driving state in which the vehicle speed is kept constant or limited by influencing the service brake (HDC operation) and a comparison result of a model-based brake pressure with a corresponding threshold value represents a brake pressure above the threshold value (block 752).

The state transition from the fifth strategy to the third strategy takes place if at least one of the conditions for the transition to the first and fourth strategies is not met and a comparison result from a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value (VFzgS) for the quantity describing the speed of the vehicle represents a vehicle speed below the threshold value (block 753).

FIG. 2 schematically shows an inventive device for recognizing the direction of travel according to the five strategies 1 to 5.

200 is a priority circuit for prioritizing one of the strategies for detecting the direction of travel of the vehicle, 240 to 244 are an evaluation means for correlating the input signals. 210-217 are input lines for receiving input signals from the sensors 115-117 and the control device 110. 200 receives the information via 210 that the clutch is closed, via 211 the engine speed Nmotor, via 212 the signals from a timer, via 213 the engine torque MMotor, over 214 the gear information, over 215 the wheel speeds, over 216 the accelerator pedal position and over 217 that

Longitudinal acceleration signal. Evaluation means 240 receives the gear information over 250, evaluation means 241 over 251 the longitudinal acceleration signal and over 252 the wheel speeds, evaluation means 242 over 254 the wheel speeds and over 253 the Longitudinal acceleration signal, evaluation means 243 over 255 the wheel speeds and over 256 the longitudinal acceleration signal.

Claims

claims

1. A method for detecting the direction of travel of a vehicle, in particular for use with an HDC control (HDC = Hill Descent Control), which keeps or limits the vehicle speed when driving uphill by influencing the service brake, characterized in that the detection of the direction of travel is dependent internal and / or external vehicle variables, such as engine speed, engine torque, accelerator pedal position, gear engaged, clutch condition, turning behavior of the wheels, longitudinal acceleration, road inclination, is determined by correlating at least two variables and that the selection of those to be correlated Vehicle sizes take place in accordance with a status determination of the vehicle sizes and / or if the vehicle sizes meet certain conditions with regard to their time profiles.

2. The method according to claim 1, characterized in that a strategy for detecting the direction of travel of the vehicle is selected from at least two different strategies as a function of the status of the vehicle sizes, which represents the priority of the direction of travel detection determined from the correlated conditions.

3. The method according to claim 1 or 2, characterized in that five strategies are provided, the priority of which is determined cyclically (loop-wise).

4. The method according to any one of claims 1 to 3, characterized in that the state transition from the third or the second strategy after the first strategy is done if the conditions

Accelerator Pedal (FPed)> Threshold (FPedS)

Motor torque (MMotor)> Threshold (MMotorS)

Clutch closed (Kg)

Gear is engaged (V gear, R gear) are fulfilled.

5. The method according to any one of claims 1 to 4, characterized in that the state transition from the third or second strategy takes place according to the fifth strategy if the conditions for the transition to the first strategy are not met and a comparison result from a the speed of the vehicle describing variable (VFzg) and a characteristic threshold value (VFzgS) for the variable describing the speed of the vehicle represents a vehicle speed lying above or above the value of the threshold value.

6. The method according to any one of claims 1 to 5, characterized in that the state transition from the third strategy to the second strategy takes place if the conditions for the transition to the first strategy and fifth strategy are not met and a comparison result from a depending on a filtered (aFilt) and an unfiltered longitudinal acceleration signal (a) compares a longitudinal acceleration signal lying in a defined band for a certain time.

7. The method according to claim 6, characterized in that to carry out the comparison, a difference between the filtered (aFilt) and the unfiltered Longitudinal acceleration signal (a) is formed and compared with a characteristic threshold (aSΪ).

8. The method according to claim 6 or 7, characterized in that it is determined in the comparison whether the conditions

| aFilt - a | <-ϊSl are fulfilled.

9. The method according to any one of claims 1 to 6, characterized in that the state transition from the first strategy to the fifth strategy takes place if at least one of the conditions

Accelerator pedal (FPed) ≤ threshold (FPedS) engine torque (MMotor) <threshold (MMotorS) clutch open is met.

10. The method according to any one of claims 1 to 6 and 9, characterized in that the state transition from the fourth strategy to the third strategy takes place when the vehicle is not in a downhill driving state in which the vehicle speed is constant by influencing the service brake is held or limited (HDC operation) or a comparison result of a model-based brake pressure with a corresponding threshold value represents a brake pressure below the threshold value and a comparison result of a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value

(VFzgS) for the variable describing the speed of the vehicle represents a vehicle speed below the threshold value.

11. The method according to any one of claims 1 to 6 and 9 or 10, characterized in that the state transition from the The fourth strategy follows the first strategy if the vehicle is not in a downhill driving state in which the vehicle speed is kept constant or limited by influencing the service brake (HDC operation) or on

Comparison result of a model-based brake pressure with a corresponding threshold value represents a brake pressure below the threshold value and a comparison result of a quantity describing the speed of the vehicle (VFzg) and a characteristic threshold value (VFzgS) for the quantity describing the speed of the vehicle represents a vehicle speed that is above the threshold value and the conditions accelerator pedal (FPed)> threshold (FPedS) engine torque (MMotor)> threshold (MMotorS) clutch closed (Kg) gear is engaged (V gear, R gear) are fulfilled.

12. The method according to any one of claims 1 to 6 and 9 to 11, characterized in that the state transition from the fifth strategy to the first strategy takes place when the conditions

Accelerator Pedal (FPed)> Threshold (FPedS)

Motor torque (MMotor)> Threshold (MMotorS)

Clutch closed (Kg)

Gear is engaged (V gear, R gear) are fulfilled.

13. The method according to any one of claims 1 to 6 and 9 to 12, characterized in that the state transition from the fifth strategy to the fourth strategy takes place if the conditions for the transition to the first strategy are not met if the vehicle is in a downhill driving state in which the vehicle speed is kept constant or limited by influencing the service brake (HDC operation) and a comparison result of a model-based brake pressure with a corresponding threshold value reflects a brake pressure above the threshold value.

14. The method according to any one of claims 1 to 6 and 9 to 13, characterized in that the state transition from the fifth strategy to the third strategy takes place when the conditions for the transition to the first and fourth strategies are not met and a comparison result from one the variable describing the speed of the vehicle (VFzg) and a characteristic threshold value (VFzgS) for the variable describing the speed of the vehicle represent a vehicle speed below the threshold value.

15. The method according to any one of claims 1 to 14, characterized in that in a first strategy the direction of travel is detected in such a way that on forward driving is recognized when a forward gear (VGang) is engaged and on reverse driving when a reverse gear (RGang) is inserted.

16. The method according to any one of claims 1 to 15, characterized in that in the second strategy on forward travel is detected if the filtered longitudinal acceleration signal aFilt is negative and at least one threshold value aS 2 smaller than the filtered longitudinal acceleration signal a, and on reverse travel is detected if the filtered longitudinal acceleration signal is positive and by at least aS 2 is greater than the unfiltered longitudinal acceleration signal.

17. The method according to claim 16, characterized in that in order to check the plausibility of the direction of travel detection in the second strategy, it is determined whether a characteristic threshold value (VFzgS) for the speed of the vehicle is within a predetermined time of a quantity describing the speed of the vehicle descriptive size is reached or exceeded.

18. The method according to claim 17, characterized in that in a comparison result in which the vehicle speed is greater than the threshold value, the direction of travel is confirmed from the second strategy.

19. The method according to claim 18, characterized in that, in the case of a comparison result in which the vehicle speed is lower than the threshold value, it is determined whether a gear is engaged, detection being made for forward travel when the forward gear is engaged and reverse travel when the reverse gear is engaged.

20. The method according to any one of claims 1 to 16, characterized in that the direction of travel detection of the vehicle is carried out according to a third strategy, wherein depending on the road gradient on forward driving if the value of the relationship is negative and on reverse driving if the value of the Relationship is positive.

21. The method according to claim 20, characterized in that the road gradient outside the first or second strategy (i.e. while driving) is calculated and stored according to the following relationship:

when driving backward sin a = ^{g & mar +} """g otherwise when ^driving forward sin a = ^{α & mor ÜRad} g

22. The method according to any one of claims 1 to 17, characterized in that in a fourth strategy from a variable describing the wheel speeds, a vehicle acceleration according to dv dω a _wheel = - or a _wheel = - * r dt dt with v = wheel speed, ω = Angular velocity, r =

Radius, it is determined that the vehicle acceleration is compared in terms of amount with a characteristic threshold value a ^ S for the vehicle acceleration determined from the wheel speeds of the vehicle, and that the direction of travel is determined based on the comparison from an unfiltered longitudinal acceleration signal a, with a positive over a period of time Longitudinal acceleration signal represents a reverse drive and a negative longitudinal acceleration signal present over a period of time represents a forward drive.

23. The method according to any one of claims 1 to 17 and 22, characterized in that after a fifth strategy, the direction of travel is maintained, which was determined according to one of the previous strategies in the last cycle if none of the strategies for

Direction detection is carried out in the current cycle.

4.Device for detecting the direction of travel of a vehicle, in particular when used in an HDC control (HDC = Hill Descent Control), which keeps or limits the vehicle speed when driving uphill by influencing the service brake, characterized by detection means for detecting the direction of travel as a function of Internal and / or external vehicle variables, such as engine speed, engine torque, accelerator pedal position, gear engaged, clutch condition, turning behavior of the wheels, longitudinal acceleration, road inclination, evaluation means for correlating at least two variables and for selecting the variables to be correlated according to requirements a status determination of the vehicle sizes and / or if the vehicle sizes meet certain conditions with regard to their time profiles, takes place.

25. The device according to claim 24, characterized in that a priority circuit is provided which, depending on the status of the vehicle sizes, selects a strategy for detecting the direction of travel of the vehicle from at least two different strategies.