DE10026102A1 - Detecting when motor vehicle is travelling up or down hill involves comparing deviation time for which detected normal driving error exists continuously with minimum time - Google Patents

Abstract

The method involves determining a vehicle reference speed (Vref) with wheel revolution rate sensors (2), determining vehicle acceleration by differentiation (4), comparing the derived acceleration (aref) with a detected longitudinal acceleration (aL), checking whether a normal driving error exists by monitoring the acceleration error against a threshold greater than null, determining a deviation time for which the detected normal driving error exists continuously, checking the time against a minimum time (TM) and detecting uphill or downhill travel if the time exceeds the minimum time. An Independent claim is also included for an arrangement for implementing the method.

Description

The invention relates to a method according to the preamble of Claim 1, and a device according to the preamble of An saying 10.

Modern motor vehicles are equipped with a wide variety of electric African systems for controlling and regulating driving behavior least equipped. Examples are braking force control systems (ABS), driving stability programs (ESP) and traction slip control systems (ASR, BTCS or TCS). The control program me that are present in the electronics of these systems evaluate a variety of sensors depending on the version the motor vehicle are installed from. These are e.g. B. wheel speed, longitudinal acceleration, lateral acceleration and Engine torque sensors. With traction control is ensured by the electronics that when strong Acceleration of the vehicle that accelerate the vehicle do not spin the wheels. On the one hand, this can be done from Ab brake the spinning wheel happen and / or by Throttling of the drive power (engine torque reduction).

DE-A 38 09 101 describes a method and a circuit arrangement for controlling an ASR system with brake and engine intervention. In this method, the wheel brake is used for traction control and / or intervenes in the control of the drive motor. For this purpose, the traction control system accesses, among other things, conventional components of the anti-lock device (ABS) which is present anyway. Communication with the required vehicle components (for example, engine) can take place via a vehicle data bus (CAN) known per se. In order to carry out the method, sensors for determining the wheel turning behavior are evaluated by circuits for signal processing and actuating signals for the generation of electromagnetic hydraulic valves which enable control of the braking force are generated. The electronics of the system require the so-called vehicle reference speed V _ref to calculate the required manipulated variable. This size is usually determined from the wheel speeds of the individual wheels. If special driving situations occur, it can happen that one or more wheels no longer reflect the current vehicle speed because one of the wheels is spinning. In this case, it is common that the spinning wheel is not used to form the vehicle reference speed V _ref .

The control algorithms of ABS use the vehicle speed V _ref as an essential input variable. If the vehicle reference speed deviates from the actual vehicle speed V _t , this can lead to an unjustified response of ABS, which results in a brake pressure reduction for a certain time. Due to the associated dangers, a deviation from V _ref and the actual speed V _t should, if at all, therefore only exist for as short a period as possible.

In the aforementioned electronic systems for Controlling vehicle behavior becomes the influence of a Uphill or downhill, which is particularly true for all-wheel drive vehicles is important, insufficient or not at all considered. For example, in the event of a traction slip control detected a spinning of the drive wheels, see above  the vehicle reference would become faster when driving uphill speed due to a misinterpretation of the longitudinal acceleration position sensor are too high. As a result, the An traction control not sufficient, to the play through engine torque reduction on the drive slip responds. On the other hand, the ABS control would be when driving downhill too sensitive.

The invention therefore has the aim of equipping conventional electronic systems for controlling vehicle behavior with an improved method for detecting the presence of an uphill or downhill run, so that the vehicle reference speed V _ref leads to V _t faster, so that electronic systems work more reliably to control driving stability, etc., which use the vehicle reference speed as an input variable.

According to the invention, this object is achieved by a method ren according to claim 1.

According to the invention, the presence of an uphill or downhill descent can be recognized by means of vehicle data which are already present in the vehicle, such as data on the longitudinal acceleration, the engine torque or the wheel speed. For this purpose, a vehicle reference speed V _{ref is first} determined from the wheel sensor signals in a manner known per se. For example, the wheel speed of the slowest rotating wheel can be used for this purpose. A vehicle acceleration a _{ref is} calculated or generated from this vehicle reference speed by differentiation, which can be done numerically, for example. This vehicle acceleration is then according to the invention in relation to a vehicle acceleration from other sensors. If it appears necessary, a plausibility assessment of the vehicle acceleration determined from the wheel speeds can be carried out. If there is a plausibility that the existing vehicle reference speed does not correspond to the actual vehicle speed, it can be extrapolated based on the determined vehicle acceleration (for example, either directly from the derived vehicle reference speed or from the acceleration determined by sensors). For this purpose, for example, a vehicle acceleration is estimated as accurately as possible in accordance with the method described in P 98938709.7 (P9071) and unpublished patent application P 19939979.4 (P9584). However, this extrapolation can only be carried out incorrectly if it is not simultaneously recognized when going up or down a hill.

P 98938709.7 (P9071) already suggests that Driving on an uphill or downhill slope when correcting or extrapolation of the vehicle reference speed consider. This is done according to the known method by only recognizing that the wheels are overturning, if the angular velocities and / or Winkelbe accelerations of the wheels by certain minimum amounts differentiate, or in other words, if the ge mentioned values not within a certain range of values lie. Here, the factual experience is used that the wheels do not spin symmetrically, but instead rather uncoordinated, so that there are clear differences in values to step.

However, according to the present invention occur in today's  All-wheel drive vehicles, in particular those vehicles that use egg ner essentially rigid all-wheel clutch (for example Haldex coupling) are also equipped to the same extent spinning wheels, so that the known method at these vehicles stopped working.

In the case of a motor vehicle with all-wheel drive, the vehicle reference speed determined from the wheel speed signals may not correspond to the actual vehicle speed over a longer period of time, since all the wheels that can be used spin on a slippery surface. In the case of spinning wheels, the vehicle acceleration depends largely on the coefficient of friction µ of the individual wheels. The coefficient of friction µ can be, for example, according to the formula

calculate, where ω is the angular acceleration, J is the moment of inertia of a single wheel, M _{mot is} the engine torque, F _{N is} the normal force of the vehicle and r _{R is} the wheel radius.

The relationship between engine torque, moment of inertia Wheels and power transmission are particularly easy using a table of values for a specific vehicle type establish. As described in P 19939979.4 (P9584), ent holds this table each associated with an engine torque acceleration values and possibly a column with which the entered gearbox level of the vehicle can, so that the possible acceleration of the vehicle inferred and the vehicle reference speed can be extrapolated.  

As already mentioned, when driving uphill or downhill, the extrapolation of the vehicle speed cannot be carried out precisely enough. In order to arrive at a reliably determined (secured) reference speed, an axis or a wheel of the vehicle is preferably decoupled from the drive and the running behavior of the decoupled axis or the wheel is checked according to the invention, especially if an extrapolation has already been carried out over a longer period of time . If the speed of the decoupled wheel or wheels decelerates to such an extent that it is lower than the vehicle reference speed V _ref , the determined vehicle reference speed is too high. In this case, the vehicle reference speed must be corrected to lower values. This can, for example, be carried out continuously or preferably in discreet steps by adding a correction value K.

According to the invention, the derived vehicle acceleration _ref from the speed V Fahrzeugreferenzgeschwin a _ref is the value of a longitudinal acceleration sensor a _L compared. This comparison can be used to determine whether the vehicle has a normal driving deviation or not. There is a normal driving deviation if the amount of a _L - a _{ref is} greater than a fixed threshold value SL, where SL <than 0. A normal driving deviation occurs, for example, when the vehicle is driving uphill or downhill for a long time. However, shorter accelerations of the wheels can also lead to a deviation from normal driving, which is, however, only important in the case of an uphill or downhill ride that is present over a longer period of time. Therefore, according to the invention, a deviation time t is measured within which the normal travel deviation must have taken place. In order to identify whether there is an uphill or downhill run, the value of the deviation time t is checked and detected when going uphill or downhill when the time t has exceeded a minimum value.

Preferably, a deviation time t ₁ for uphill and a deviation time t ₂ for downhill is determined. Here, t ₁ indicates the duration in which the logical equation a _ref - SL <a _{L is} fulfilled. The time t ₂ indicates how long the logical equation a _ref + SL <a _{L has been} fulfilled. In this way, it is particularly easy to distinguish between going uphill and downhill.

According to the invention, it is an uphill or downhill run knows, this can preferably be a correction of the An result in driving power, especially an engine ment change or disclosure of a corresponding Control signal through the electronic system to the An drive unit.

The method according to the invention can be carried out in all-wheel drive vehicles such as vehicles with only one driven axle. In the case of a vehicle without non-driven axles (four-wheel drive vehicle), the vehicle reference speed V _ref is preferably extrapolated with the aid of the degree of uphill or downhill travel, taking into account the degree of uphill or downhill travel, taking into account a possible uphill or downhill ride, the extrapolation of V _ref in the direction of V _t .

In order to check (safeguard) the vehicle reference speed V _ref , a driven axle is preferably decoupled from the drive and the actual vehicle speed is deduced from the behavior of this non-driven axle. If the non-driven axle slows down to below V _ref after _uncoupling , the vehicle reference speed is generally too high. However, if the speed of the wheels on the uncoupled axle does not change, then the vehicle reference speed will generally be too low, which suggests a downhill run.

If the vehicle _{reference speed} V _{ref is} corrected, this can preferably be accomplished by iteratively adding a correction value K to V _ref . The correction value K can be either positive or negative depending on the direction from which V _{ref has} to be approximated to the actual vehicle speed. As already mentioned above, the value of K is corrected in a suitable manner depending on whether there is an uphill or downhill slope. K is preferably from about 0.1 g to about 0.3 g.

The threshold value SL, which corresponds to an acceleration, is preferably between approximately 0.02 g and 0.2 g, in particular in particular between approximately 0.04 g and 0.12 g, the falling acceleration being g = 9.81 ms ^-2 . A value of 0.08 g, for example, corresponds to a slope of 8%. The counter contained in the device is consequently incremented by the value 1 whenever there is a normal driving deviation with a probability for driving uphill which is recognized by the electronics, the increase by 1, for example, corresponding to a time of 7 ms. If there is a normal driving deviation with downhill driving detected by the electronics, the counter for downhill driving detection is incremented by the value 1. If the two above-mentioned conditions for driving uphill or downhill are no longer met at a measurement time, the counter is preferably decremented again by the value 1 or particularly preferably set to the value 0. A negative value for the counter is excluded.

If the normal deviation, which is a kind of true indicates the likelihood of going uphill or downhill has confirmed a high counter value, this informa tion as a change of state, for example using a di gital output to the environment. For this, for example, the counter or counters on the Exceeding a certain threshold, e.g. B. 200 (corresponds to one with a unit of 7 ms per counting unit Time of 1400 ms). Will this threshold value is exceeded, then the previously described dimension took initiated.

According to a preferred embodiment of the invention, in an all-wheel drive vehicle to secure the vehicle reference speed in an all-wheel drive vehicle, at least one of the wheels or an axle is decoupled from the drive train. This can be useful in the following situations:

• 1. The vehicle reference speed determined or extrapolated with reference to all wheel signals lies above the actual vehicle speed V _t .
• 2. The vehicle reference speed is below the actual vehicle speed V _t .

To identify this situation, it is often necessary to query one or more of the following conditions:

• - Activation of the traction control system (this criterion indicates that traction slip has been detected).
• - The vehicle reference speed has already been set via ei modified or extrapolated over a longer period of time (This criterion provides an indication of whether the Vehicle reference speed increasingly implausible becomes).
• - The actual vehicle acceleration is less than a certain threshold.
• - The wheel slip is greater than another threshold (The wheel slip can be determined, for example, by comparing the individual wheel speed values with the vehicle reference worth to be recognized).
• - The traction control of the engine has been effective for one for a certain period of time without delay, wuh a low road surface friction coefficient was recognized at the same time or is in a continuous state the torque reduction.

Preferably, several or all of the above criteria are queried unlinked. An increase in the vehicle reference speed for adaptation is only possible within certain limits by extrapolation. Several or all of the following conditions can be checked to identify the situation in which it is necessary to disconnect some wheels from the drive in an all-wheel drive, these preferably having to be fulfilled for a minimum period (e.g. 300 ms or more):

• - The signal from the longitudinal acceleration sensor is around a be correct minimum dimension larger than that from the wheel signals determined vehicle reference acceleration. In this case there is an uphill / downhill run.
• - The motor torque must be greater than the value ZERO.
• - The wheel accelerations and / or the wheel speeds all wheels must show stable wheel behavior (Wheel accelerations less than threshold).
• - The wheel speeds of the wheels must be above the Vehicle reference speed.

The wheels are preferably uncoupled for a period of less than 2000 ms, especially for a period of about 300 to 1000 ms. The duration of the disconnection the drive train wheel or wheels can preferably be 300 up to 1000 ms. Preferably, procedurally before be seen that disconnect during a particular Period is not done too often. This leaves an indif Avoid remote vehicle behavior.

The degree of deviation from V _ref to V _t is preferably determined by determining an approximation time t _K which is required to increase the value of V _ref by repeated correction by the correction value K in the direction of the actual value for the vehicle speed V _t aproximize. The method according to the invention can particularly preferably be expanded in that, with the aid of the established time t _K , it is established whether there has been an uphill or downhill run. Uphill or downhill descent occurs in particular when the time t _K has exceeded a certain threshold value. This threshold value is preferably in a range from approximately 40 to 100 ms.

According to the invention, the term "aproximize" means that Approaching a value understood to another value where when the value to be achieved is not exactly met got to.

The assumed vehicle acceleration, which is used to influence the vehicle reference speed, is preferably changed according to the time t _K in such a way that the higher the determined time t _K , the amount of the correction value K is increased.

The invention also relates to a device for performing tion of the inventive method described above rens according to claim 10.

A counter for uphill (t ₁ ) and downhill (t ₂ ) is preferably provided.

The implementation of the above methods can be preferably in a suitably programmed computer-aided Control.

The invention has the advantage that with the ß procedures in particular for vehicles with a Re control system for controlling the longitudinal dynamics and / or transverse dynamics of the vehicle (e.g. BTCS or TCS, as well as ESP) can be recognized whether the vehicle  drives uphill or downhill. Driving on a slope results in a change in the axle load distribution that occurs with an An traction control adversely affect engine control flows. By means of the method according to the invention, the information mation uphill or downhill detection for ver improved engine torque reduction can be used. The hee ability of acceleration drops, as in drive slip rules can occur when driving uphill, becomes strong decreased.

Further preferred embodiments result from the following figure description.

It shows

Fig. 1 is a schematic representation of a game Ausführungsbei according to the invention.

In Fig. 1, a motor vehicle 1 is shown, which moves with the vehicle speed (actual speed) V _t . The wheel speeds of the wheels 3 are measured by sensors 2 and fed to an electronic processing unit 10 . In the processing unit 10 there is a known generation of a vehicle reference speed V _ref . The Fahrzeugreferenzge speed is to other systems such. B. forwarded to the Sy stem R (ABS, ASR, ESP). The vehicle reference speed can be corrected or extrapolated on the basis of engine torque data of an engine M and transmission data of a transmission G. In step 4, the vehicle acceleration a _ref with processing unit 5 is formed from the vehicle reference speed from the vehicle reference speed. In unit 6 , a comparison is made between a _L and a _ref . The deviation times t, t ₁ , t ₂ are stored in counters in the unit 7 . If a time threshold value T _{M is} exceeded, this leads to the information "uphill or downhill" being forwarded to the unit for determining the vehicle reference speed V _ref . The unit 10 preferably contains a further unit 9 for the separate detection of uphill or downhill travel.

The processing unit 10 can access an all-wheel clutch 11 via a line. If necessary, this allows an axis of the driven wheels to be uncoupled from the motor M. Furthermore, a processing unit 8 is provided that measures the time t _K that is required to approximate the value of V _ref to the actual vehicle speed.

Claims (11)

1. A method for detecting an uphill or downhill descent of a motor vehicle ( 1 ) which is moving at the speed V _t , with the steps:

• - Determination of a vehicle reference speed V _ref by means of wheel speed sensors ( 2 ), V _ref possibly being corrected in particular in the case of exclusively spinning wheels ( 3 ) by extrapolation of acceleration data, engine torque data and / or information about the gear stage inserted,
• - Determination of a vehicle _acceleration a _ref from V _ref by differentiation ( 4 ),
• - Comparison of a _ref with a sensor-determined vehicle longitudinal acceleration a _L ( 5 ),

characterized in that

• a) it is checked whether there is a normal driving deviation by monitoring whether the amount of the difference a _L - a _{ref is} greater than a threshold value SL, where SL is greater than zero ( 6 ),
• b) a deviation time t is determined within which the determined normal travel deviation is present continuously ( 7 ),
• c) the deviation time t is monitored for exceeding a minimum time value T _M , where T _{M is} greater than zero, and
• d) is concluded on uphill or downhill travel if t is greater than T _M.

2. The method according to claim 1, characterized in that a deviation time t ₁ for driving uphill and a deviation time t ₂ for driving downhill is determined, where t ₁ indicates the duration in which the equation a _ref - SL <a _{L is} satisfied and t ₂ the duration in which a _ref + SL <a _{L is} fulfilled. 3. The method according to claim 1 or 2, characterized in that in an all-wheel drive vehicle in the event of spinning the wheels, taking into account any uphill or downhill ride, the vehicle reference speed V _{ref is} extrapolated with the aid of the degree of uphill or downhill ride , the extrapolation of V _{ref being made} in the direction of V _t . 4. The method according to claim 3, characterized in that to control V _ref a driven axle or a wheel is decoupled from the drive and is concluded from the behavior of the non-driven axle or wheels on the actual vehicle speed. 5. The method according to claim 1 to 4, characterized in that the correction of V _ref is carried out by iteratively adding a positive or negative correction value K to V _ref , the correction being carried out in the opposite direction to the deviation determined. 6. The method according to claim 5, characterized in that the extrapolation of the vehicle reference speed V _{ref is} taken into account whether driving uphill or downhill is present, the detection of whether going uphill or downhill is present with the method according to at least one of claims 1 to 5 is carried out. 7. The method according to at least one of claims 4 to 6, characterized in that the decoupling for a duration of less than 2000 ms.   8. The method according to at least one of claims 5 to 7, characterized in that the degree of deviation from V _ref to V _t is determined by determining an approximation time t _K ( 8 ) that is required, the value of V _ref by repeated correction to approximate the correction value K in the direction of the actual value for the vehicle speed V _t . 9. The method according to at least one of claims 5 to 8, characterized in that the assumed vehicle acceleration, which is used to influence the vehicle speed limit, is changed in accordance with the time t _K in such a way that the higher the certain time t _K is, the amount of the correction value K he is increased. 10. Apparatus for performing the method according to claims 1 to 9, characterized in that the measurement of the times t, t ₁ , t ₂ and t _{K is carried out} by a digital logic with a counter ( 7 , 9 ), where a digit of the logic speaks ent of a fixed unit of time. 11. The device according to claim 10, characterized in that a counter ( 7 , 9 ) for uphill and Ber gabfahrt is provided.