DE102019128513A1 - Method for preventing a vehicle from tipping over - Google Patents

Abstract

The invention relates to a method for preventing a vehicle (1) from tipping over about its longitudinal axis (2), in which an electronic brake system (3) evaluates a current transverse acceleration (4) and, after a first limit value of the transverse acceleration (4) is exceeded, test braking is executed by the electronic brake system (3), and in which an inside wheel (5) of an axle (6) that locks or tends to lock during the test braking triggers deceleration braking of at least one outside wheel (7). According to the invention, if after the first limit value has been exceeded and during the test braking of the electronic brake system (3), additional braking is carried out with a current brake pressure, which results in the wheel (5) on the inside of the curve locking or a tendency to lock, initially using a second lateral acceleration limit value (4) of the current brake pressure and instead of the first limit value ts is used as the basis for an assessment of the risk of tipping over.

Description

The invention relates to a method for preventing a vehicle from tipping over about its longitudinal axis, in which a transverse acceleration is evaluated by an electronic brake system and a test braking is carried out by the braking system after a first limit value of the transverse acceleration is exceeded, and in which a blocking or blocking during the test braking inclining wheel on the inside of the curve of an axle triggers deceleration braking of at least one wheel on the outside of the curve. The invention also relates to a method for determining a height of the center of gravity of a vehicle, a brake control device for carrying out this method and an electronic brake system with such a brake control device.

Methods for determining and avoiding a risk of a vehicle tipping over about its longitudinal axis are disclosed in, inter alia DE 196 02 879 C1 and EP 1 142 768 B1 . Reference is expressly made to the entire disclosure of these two documents to illustrate and explain the invention.

Modern road vehicles are equipped with an electronic braking system. The electronic brake system contains at least one anti-lock control. Stabilizing regulations to prevent the vehicle from breaking away when cornering or when accelerating are also widespread.

Two-lane vehicles with a higher center of gravity, especially commercial vehicles, can tip over in corners that are driven too fast. This can also be prevented by appropriate control systems. The transverse acceleration of the vehicle is measured continuously for this purpose. If a limit value is exceeded, it is assumed that there is a risk of tipping over. In addition, the electronic brake system then carries out test braking with low brake pressure. If the wheel on the inside of the curve then blocks or almost blocks, this means that the dynamic wheel load acting on the wheel on the inside of the curve is only very low and countermeasures are required. Deceleration braking is then preferably initiated by the braking system in order to reduce the speed of the vehicle. If the wheel on the inside of the curve does not lock during the test braking and also shows no tendency to lock, countermeasures can be omitted. A tendency to lock is assumed in particular if the wheel on the inside of the curve has a brake slip of more than 20%. Further test braking operations are carried out at short intervals, at least as long as the transverse acceleration remains above the first limit value.

During the test braking by the brake system, an additional braking request can occur, namely additional braking, for example by the driver as driver braking or by a stability control system of a towing vehicle, provided that the vehicle under consideration is a trailer vehicle. This additional braking is usually carried out with a higher brake pressure than the test braking. The higher brake pressure of the additional braking is then effective on the brake cylinders. However, the brake system continues to assume that test braking is being carried out and waits for the corresponding result. Due to the higher brake pressure of the additional braking, the wheel on the inside of the curve locks up earlier than during the test braking, so that the braking system has the impression that countermeasures need to be taken. This can lead to unnecessary and uncomfortable deceleration brakes triggered by the braking system. This is associated with increased tire wear, brake wear and fuel consumption.

The object of the present invention is to improve the behavior of the known method for preventing a vehicle from tipping over about its longitudinal axis. In particular, unnecessary deceleration braking should be avoided.

To achieve the object, the method according to the invention has the features of claim 1. In particular, it is provided that if, after the first limit value has been exceeded and during the test braking of the brake system, additional braking is carried out with a current brake pressure, which results in locking or a tendency to lock the wheel on the inside of the curve, first a second limit value of the transverse acceleration using the current one Brake pressure is calculated and, instead of the first limit value, an assessment of a risk of tipping over is used as a basis.

$$M_{\text{innen}}=\sqrt{\frac{{\left(\frac{F_{\text{z}\text{,Brems}\text{,innen}}}{g}\right)}^2}{{\mathrm{\mu }}^2-\frac{{\ddot{y}}_{ist}^2}{g^2}}}$$

$$a_{\text{q}\text{,crit}}=\frac{{\ddot{y}}_{\text{crit}}}{g}=\frac{{\ddot{y}}_{\text{ist}}\left(M_{\text{Rad}}-M_{\text{Rest}}\right)}{g\left(M_{\text{Rad}}-M_{\text{innen}}\right)}$$

mit den folgenden Variablen und Konstanten:

aq,crit

auf die Erdbeschleunigung g normierte Querbeschleunigung ÿ_crit

Fz,Brems

berechnete Vertikalkraft eines Rads auf Basis der Bremsberechnung und des aktuellen Bremsdrucks bei Geradeausfahrt

Fz,Brems,innen

berechnete Vertikalkraft des kurveninneren Rads auf Basis der Bremsberechnung und des aktuellen Bremsdrucks bei Geradeausfahrt

Fz,voll

Achsvertikalkraft beladen

Fz,leer

Achsvertikalkraft leer

g

Erdbeschleunigung

Minnen

aktuelle dynamische Radlast kurveninneres Rad

MRad

mittlere Radlast, halbe Achslast

MRest

kritische Restradlast, vom Systemhersteller vorgegeben als Parameter

pist

Bremsdruck aktuell

pleer

Bremsdruck, bei dem Räder des leeren Fahrzeugs blockieren

pvoll

Bremsdruck, bei dem Räder des vollen Fahrzeugs blockieren

ÿcrit

kritische Querbeschleunigung, bei der Verzögerungsbremsung gestartet werden soll

ÿist

aktuelle Querbeschleunigung

z

auf die Erdbeschleunigung g normierte Abbremsung

µ

Reibwert (angenommen mit 0,7 für trockene Straße)

The second limit value of the transverse acceleration ÿ _crit and the second limit value of the transverse acceleration a _{q, crit} normalized to the acceleration due to gravity g can be calculated as follows: $${\mathrm{F.}}_{\text{z}\text{, Brake}}=\frac{1}{2}z\left(\left({\mathrm{F.}}_{\text{z}\text{,full}}-{\mathrm{F.}}_{\text{z}\text{,empty}}\right)\frac{p_{\text{is}}}{p_{\text{full}}-p_{\text{empty}}}+\frac{p_{\text{full}}{\mathrm{F.}}_{\text{z}\text{,empty}}-p_{\text{empty}}{\mathrm{F.}}_{\text{z}\text{,full}}}{p_{\text{full}}-p_{\text{empty}}}\right)$$

$${\mathrm{M.}}_{\text{Inside}}=\sqrt{\frac{{\left(\frac{{\mathrm{F.}}_{\text{z}\text{, Brake}\text{,Inside}}}{G}\right)}^2}{{\mathrm{\mu }}^2-\frac{{\ddot{y}}_{ist}^2}{{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="DE102019128513A1\_0009.png,DE102019128513A1\_0012.png"\; state="\{\{state\}\}">G</figure-callout>}}^2}}}$$

$$a_{\text{q}\text{, crit}}=\frac{{\ddot{y}}_{\text{crit}}}{G}=\frac{{\ddot{y}}_{\text{is}}\left({\mathrm{M.}}_{\text{wheel}}-{\mathrm{M.}}_{\text{rest}}\right)}{G\left({\mathrm{M.}}_{\text{wheel}}-{\mathrm{M.}}_{\text{Inside}}\right)}$$

with the following variables and constants:

aq, crit

_Lateral acceleration ÿ crit normalized to the acceleration due to gravity g

Fz, brake

Calculated vertical force of a wheel based on the brake calculation and the current brake pressure when driving straight ahead

Fz, brake, inside

Calculated vertical force of the wheel on the inside of the curve based on the brake calculation and the current brake pressure when driving straight ahead

Fz, full

Axial vertical force loaded

Fz, empty

Axial vertical force empty

G

Acceleration due to gravity

Love

Current dynamic wheel load on the inside wheel

MRad

medium wheel load, half axle load

MRest

critical residual wheel load, specified as a parameter by the system manufacturer

pist

Brake pressure currently

pleer

Brake pressure at which the wheels of the empty vehicle lock

pful

Brake pressure at which the wheels of the full vehicle lock

ÿcrit

critical lateral acceleration at which deceleration braking should be started

is

current lateral acceleration

z

Deceleration normalized to the acceleration due to gravity g

µ

Coefficient of friction (assumed 0.7 for dry roads)

As indicated in formula (3), the current lateral acceleration ÿ _ist , 4th , the acceleration due to gravity g, a mean wheel load M _wheel , a critical residual _{wheel load M rest} and a current dynamic wheel load M _{inside the wheel on the inside of} the curve are required. The system manufacturer specifies the critical residual wheel load as a parameter. The mean wheel load corresponds to half the axle load and is available, for example, from sensor data during a previous straight-ahead journey. The dynamic wheel load of the wheel on the inside of the curve is calculated, see formula (2). A calculated vertical force F _{z, brake, inside} the wheel on the inside of the curve based on a brake calculation and the current brake pressure are also required for this p _is and a coefficient of friction µ for the friction between the tire and the road. The coefficient of friction can be assumed to be 0.7, for example. The vertical force of the wheel on the inside of the curve results from a calculation according to formula (1). The calculation includes a deceleration z normalized to the acceleration due to gravity, an axial vertical force of the loaded vehicle, an axial vertical force of the empty vehicle, the current brake pressure, the brake pressure at which the wheels of the empty vehicle lock, and the brake pressure at which the wheels of the full one Block vehicle, one. The stated values result either from a brake calculation or from preliminary tests. A value between 0.5 and 0.6 is preferably assumed for z.

The calculated second limit value of the transverse acceleration is compared with the continuously determined current value of the transverse acceleration. The second limit value can already contain safety discounts. For example, when calculating the second limit value, a factor that is smaller than 1 or a negative summand or subtrahend can be included as a safety margin.

According to a further concept of the invention, it can be provided that deceleration braking is only carried out if the current transverse acceleration is greater than the second limit value of the transverse acceleration. The deceleration braking is preferably only carried out by the brake system when the second limit value of the transverse acceleration is currently exceeded and the current test braking results in at least a tendency to lock the wheel on the inside of the curve.

According to a further concept of the invention, it can be provided that the current lateral acceleration and / or a current axle load and / or wheel load are also used for calculating the second limit value of the transverse acceleration. The current lateral acceleration is available to the electronic brake system anyway. The current axle load can be queried using sensors that are typically present anyway. If the vehicle is equipped with air suspension, pressure sensors in air suspension bellows can supply data from which the axle load can be determined. The same applies to wheel loads.

1. a) Abbremsung, aus Bremsberechnung,
2. b) Achsvertikalkraft vollbeladen, aus Bremsberechnung,
3. c) Achsvertikalkraft leer, aus Bremsberechnung,
4. d) Bremsdruck zum Blockieren, leer, aus Bremsberechnung,
5. e) Bremsdruck zum Blockieren, voll, aus Bremsberechnung,
6. f) aktuelle Radlast des kurveninneren Rads,
7. g) berechnete Vertikalkraft des kurveninneren Rads,
8. h) statische Achslast, insbesondere aus Sensordaten,
9. i) kritische Restradlast, vorgegeben.

According to a further concept of the invention, it can be provided that one or more of the following parameters are additionally used for calculating the second limit value of the transverse acceleration:

1. a) deceleration, from brake calculation,
2. b) Axial vertical force fully loaded, from brake calculation,
3. c) Axial vertical force empty, from brake calculation,
4. d) brake pressure for locking, empty, from brake calculation,
5. e) brake pressure for locking, full, from brake calculation,
6. f) current wheel load of the inside wheel,
7. g) calculated vertical force of the inside wheel,
8. h) static axle load, in particular from sensor data,
9. i) critical residual wheel load, specified.

The current wheel load of the wheel on the inside of the curve (parameter f) can result in particular from calculation or from sensor data. A brake calculation is typically carried out by the manufacturer when the brake system is adapted to the vehicle.

According to a further concept of the invention it can be provided that a center of gravity height is calculated from a calculated current wheel load of the wheel on the inside of the curve and a static axle load and is used to adapt the first or second limit value of the lateral acceleration. By including the height of the center of gravity, the limit value of the transverse acceleration can be determined even more precisely.

mit den folgenden Variablen und Konstanten:

g

Erdbeschleunigung

HSP

Schwerpunkthöhe

MAchse

Achslast

MRad

mittlere Radlast, halbe Achslast

MRest

kritische Restradlast, vom Systemhersteller vorgegeben als Parameter

s

Spurweite

ÿist

aktuelle Querbeschleunigung

The height of the center of gravity H _SP can be calculated as follows: $$H_{\text{SP}}=\frac{s\left({\mathrm{M.}}_{\text{wheel}}-{\mathrm{M.}}_{\text{rest}}\right)}{{\mathrm{M.}}_{\text{Aches}}\frac{{\ddot{y}}_{\text{is}}}{G}}$$

with the following variables and constants:

G

Acceleration due to gravity

HSP

Center of gravity

Axis

Axle load

MRad

medium wheel load, half axle load

MRest

critical residual wheel load, specified as a parameter by the system manufacturer

s

Gauge

is

current lateral acceleration

The invention also relates to a method for determining the height of the center of gravity of a vehicle with an electronic braking system. Starting from a two-lane vehicle with an unknown height of the center of gravity, which can vary due to different loads, various parameters and physical quantities are used to calculate a current height of the center of gravity, see claim 6 Axle load provided. Other parameters can be included in the calculation. The height of the center of gravity can be used for other calculations and actions of the braking system.

The invention also relates to a brake control device according to claim 7 with software for carrying out the method for preventing the vehicle from tipping over and / or the method for determining a height of the center of gravity. The individual process steps are mapped in the software of the control unit.

Finally, the invention is also directed to an electronic brake system according to claim 8. The electronic brake system has said control device.

• 1 eine schematische Darstellung eines Fahrzeugs während einer Kurvenfahrt in einer Draufsicht,
• 2 eine schematische Darstellung eines Querschnitts durch das Fahrzeug nach 1,
• 3 eine schematische Darstellung eines Querschnitts durch das Fahrzeug entsprechend 2, wobei das Fahrzeug einer Gefahr eines Umkippens unterliegt,
• 4 einen Graphen eines zeitlichen Verlaufs von Bremsdruck, Querbeschleunigung, Drehzahl des kurveninneren Rads und Drehzahl des kurvenäußeren Rads im Zeitverlauf, mit Testbremsung und Verzögerungsbremsung (Stand der Technik),
• 5 einen Graphen eines zeitlichen Verlaufs entsprechend 5, jedoch mit Testbremsung, Zusatzbremsung und Verzögerungsbremsung, ohne Verwendung eines zweiten Grenzwerts für die Querbeschleunigung (Stand der Technik),
• 6 einen Graphen eines zeitlichen Verlaufs entsprechend 5, mit Testbremsung, Zusatzbremsung und Verzögerungsbremsung, jedoch mit Berechnung und Verwendung eines zweiten Grenzwerts der Querbeschleunigung,
• 7 ein Ablaufdiagramm eines Verfahrens zur Vermeidung eines Umkippens eines Fahrzeugs,
• 8 ein Ablaufdiagramm eines Verfahrens zur Bestimmung einer Schwerpunkthöhe eines Fahrzeugs.

Further features of the invention can also be found in the description and in the claims. Advantageous embodiments of the invention are explained in more detail below with reference to drawings. Show it:

• 1 a schematic representation of a vehicle while cornering in a top view,
• 2 a schematic representation of a cross section through the vehicle according to 1 ,
• 3 a schematic representation of a cross section through the vehicle accordingly 2 , whereby the vehicle is subject to a risk of tipping over,
• 4th a graph of a time curve of brake pressure, lateral acceleration, speed of the wheel on the inside of the curve and speed of the wheel on the outside of the curve over time, with test braking and deceleration braking (state of the art),
• 5 a graph of a time course accordingly 5 , but with test braking, additional braking and deceleration braking, without using a second limit value for the lateral acceleration (state of the art),
• 6th a graph of a time course accordingly 5 , with test braking, additional braking and deceleration braking, but with calculation and use of a second limit value for the lateral acceleration,
• 7th a flowchart of a method for preventing a vehicle from tipping over,
• 8th a flowchart of a method for determining a height of the center of gravity of a vehicle.

1 shows a schematic representation of a vehicle 1 while driving through a curve 13th . The vehicle 1 is shown here generically: For the vehicle 1 it can be a motor vehicle and possibly a tractor for a trailer vehicle as well as a trailer vehicle. The vehicle 1 has two axes here 6th on, with two wheels on each axle 14th are attached. While driving through the curve 13th instructs the vehicle 1 on each of the two axes 6th an inside wheel 5 and an outside wheel 7th on. The commercial vehicle 1 has a longitudinal axis 2 on.

While driving through the curve 13th learns the vehicle 1 a lateral acceleration 4th in terms of the curve 13th outward. This causes the vehicle to tilt 1 to do this, while driving through the curve 13th in terms of the curve 13th around its longitudinal axis 2 to tilt outwards so that the inside wheel 5 from a wheel contact plane 16 , in the 1 runs parallel to the plane of the drawing, can solve. In the worst case, the vehicle can 1 around the longitudinal axis 2 tip over.

The vehicle 1 has an electronic braking system 3 on. The electronic braking system 3 can be a subsystem 15th have, especially if it is the vehicle 1 a trailer vehicle acts. The electronic braking system 3 has a brake control unit 11 on, which in turn is software 17th having.

In 2 is a cross-section through the vehicle according to FIG 1 shown. The inside of the curve 13th is on the left in the illustration, the outside of the curve 13th right. The lateral acceleration 4th consequently also acts to the right. The vehicle 1 is therefore also subject to a risk of tipping over to the right (or downwards to the left in 1 ) like this in 3 is indicated. The wheel on the inside of the curve comes loose 5 from the wheel contact plane 16 . Even before the inside wheel 5 from the wheel contact plane 16 loosens, a wheel load is reduced 9 of the inside wheel 5 because there is a mass of the vehicle 1 due to the lateral acceleration 4th continue on the outside wheel 7th shifted and the inside wheel 5 relieved. Thus, there is a reduced wheel load 9 of the inside wheel 5 an indication that there is a risk of the vehicle tipping over 1 consists. That the wheel load 9 of the inside wheel 5 is reduced, can also be recognized by the fact that the inside wheel 5 blocked when braking or at least shows a tendency to block.

While on the wheels 5 , 7th , 14th one wheel load each 9 acts, acts on the axis 6th an axle load 8th . From the wheel load 9 , the axle load 8th and a gauge 19th can be a center of gravity 10 a focus 18th of the vehicle 1 above the wheel contact level 16 be calculated. The height of the center of gravity 10 depends on how much the vehicle is loaded 1 .

For the following graph in the 4th , 5 and 6th it is assumed, for example, that the vehicle 1 a trailer vehicle with an electronic braking system 3 is attached to a towing tractor with a driver. The tractor and the trailer are equipped with anti-lock control. At least the trailer vehicle has a subsystem 15th to avoid tipping over about its longitudinal axis. This is done by the electronic braking system 3 the current lateral _acceleration Y, 4th recorded and evaluated, possibly calculated. In the subsystem 15th is a first limit value for the lateral acceleration 4th saved. As soon as this first limit value is exceeded, the electronic brake system takes over 3 of the trailer vehicle perform test braking with low brake pressure at short intervals. If there is a tendency for the wheel on the inside of the curve to lock 5 occurs, there is a risk of tipping over about the longitudinal axis 2 went out. The electronic braking system 3 then automatically decelerates so that at least the wheel on the outside of the curve 7th is braked. This braking process ends only when the lateral acceleration _is Y, 4th has fallen below a value that is regarded as uncritical.

The known method described in the preceding paragraph is in the 4th The graph shown, in which a course of the speeds n _outside and n _inside of the outside and inside wheel, a current brake pressure p _is and a current transverse acceleration ÿ _is in arbitrary units over time t is applied. At the time t = 0 starts driving through the curve 13th and the value _is Y for the transverse acceleration, 4th begins to rise. At the time t _TB is the first limit value for the lateral acceleration ÿ _is , 4th reached and the test braking begins. The current brake pressure p _is increases slightly. The ride through the curve 13th gets faster or tighter. The lateral acceleration ÿ _ist increases accordingly, 4th until the inside wheel 5 significant slippage and / or a tendency to lock occurs. In the figures are the speeds n _inside of an inside wheel 5 and n _outside of a wheel on the outside of the bend 7th specified. The braking system 3 recognizes the tendency to block and triggers deceleration, see point in time t _VB . The current brake pressure p _is rises steeply and the speed n _outside of the outside wheel 7th is reduced. A method according to the invention 12th is not yet involved in this process.

5 refers to the same process as this one in 4th is shown. In addition, there is only one at the time t = 0 beginning additional braking available during the test braking, for example due to driver braking. A higher brake pressure at the point in time can be seen t _TB . At this point in time, the additional braking is applied in full and due to the lateral acceleration that has now been achieved 4th a test braking is initiated. This is in 5 not visible, as the brake pressure of the additional braking dominates. Nevertheless, the regulation to avoid tipping over applies. That is, the regulation is due to the increased lateral acceleration 4th switched on and the brake pressure of the additional braking leads to a locking wheel on the inside of the curve 5 . The electronic braking system 3 recognizes this, assumes there is a risk of tipping over and initiates deceleration braking, see point in time t _VB . The current brake pressure p _is increases sharply and the speed n _outside of the outside wheel 7th gradually decreases. Once the two wheels 5 , 7th , 14th (outside and inside of the bend) are again slip-free or almost slip-free, the brake pressure goes p _is clearly back again. In this course too, regulation is in accordance with the method according to the invention 12th not yet planned. It can be seen that the point in time t _VB the deceleration braking close to the point in time t _TB the beginning of the regulation follows.

In 6th is a process like in 5 shown, but with the inclusion of the method according to the invention 12th . At the time t = 0 the driver starts the additional braking, the current brake pressure p _is rises. At the same time, the vehicle begins to drive through the curve 13th , The lateral acceleration _is Y, 4th rises. At the time t _TB reaches the current lateral acceleration ÿ _is , 4th the first limit. The regulation according to the method according to the invention 12th is active.

Because of the high lateral acceleration 4th and the relatively high additional braking starts with the wheel on the inside of the curve 5 to block the speed n _inside drops sharply. However, there is still no risk of tipping over because the wheel on the inside of the curve 5 not because of the high lateral acceleration 4th blocked in connection with a test braking, but due to the high brake pressure of the additional braking. The electronic braking system 3 detects that additional braking is taking place during the regulation to detect a risk of tipping and calculates a second, higher limit value for the transverse acceleration 4th .

The current lateral acceleration ÿ _is 4th increases slowly over time, for example as a result of increasing speed or a radius of the curve that decreases as the curve progresses 13th . At the time t _VB exceeds the current lateral acceleration ÿ _ist , 4th also the second, higher limit value of the lateral acceleration 4th , deceleration braking by increasing the brake pressure is initiated. The speed n _outside of the outside wheel 7th then decreases, the speeds n _inside of the inside wheel 5 and n _outside of the outer wheel 7th approach each other and the actual lateral acceleration _is Y, 4th decreases again. Finally, the electronic braking system picks up 3 also back the brake pressure.

The particular advantage of the method according to the invention 12th according to 6th compared to the procedure according to 5 lies in that the electronic braking system 3 deceleration only at higher lateral acceleration 4th executes. This significantly improves driving comfort. Tire wear, brake wear and fuel consumption are lower.

For carrying out the method according to the invention 12th is the calculation of the second limit value of the lateral acceleration 4th of importance at which the deceleration braking is to be carried out. For the calculation, reference is made to the formulas (1) to (3) given in the introduction to the description, which are also reproduced on the last page of this description. The meanings of the abbreviations used are also given. The aim in this exemplary embodiment is to determine a _{q, crit , namely the critical transverse acceleration ÿ crit} , 4 normalized to the acceleration due to gravity g, which should correspond to the second limit value.

Using the determined current dynamic wheel load of the wheel on the inside of the curve, the height of the vehicle's center of gravity can also be calculated, see formula (4) given in the introduction to the description, which is also given on the last page of this description. The calculation also includes a track width, the mean wheel load, the axle load, the current lateral acceleration and the acceleration due to gravity.

A schematic flow diagram of the process 12th to prevent the vehicle from tipping over 1 around its longitudinal axis 2 is in 7th shown. In one step 20th drives the vehicle 1 in a curve 13th , being in the vehicle 1 an electronic braking system 3 is active. In one step 21 is made by the electronic braking system 3 the lateral acceleration 4th supervised. step 21 is carried out until in one step 22nd exceeding a first limit value of the transverse acceleration 4th is detected.

In one step 23 triggers the electronic braking system 3 due to the detected exceeding of the first limit value of the transverse acceleration 4th a test braking 24 out. In one step 25th is made by the electronic braking system 3 Blocking or tendency to block the inside wheel 5 supervised. step 25th is carried out until the wheel on the inside of the bend either locks or tends to lock 5 is detected or until the test braking 24 is finished. In one step 26th is during the test braking 24 additional braking is carried out. The current brake pressure of the additional braking is so high that it could cause the wheel on the inside of the bend to lock or to lock 5 has the consequence.

In one step 27 calculates the electronic braking system 3 a second limit value of the lateral acceleration 4th using the current brake pressure. It is possible that the current lateral acceleration 4th , a current axle load 8th and / or the wheel load 9 be included in the calculation. It is also possible that a deceleration, an axle vertical force (fully loaded), an axle vertical force (empty), a brake pressure for locking (empty), a brake pressure for locking (fully loaded), a current wheel load 9 of inside wheel 5 , a calculated vertical force of the inside wheel 5 , a static axle load 8th and / or a critical residual wheel load can be included in the calculation.

In an optional step 28 can be based on a current wheel load 9 of the inside wheel 5 and a static axle load 8th the height of the center of gravity 10 of the vehicle 1 calculated and for an adaptation of the first or the second limit value of the transverse acceleration 4th be used. An in 8th schematically represented process 32 to determine the height of the center of gravity 10 come into use.

In one step 29 assesses the electronic braking system 3 whether there is a risk of tipping over. If there is a risk of tipping over, the electronic braking system operates 3 in one step 30th a deceleration braking. The deceleration braking can be applied to at least one wheel on the outside of the curve 7th be effective, with the outside wheel 7th on the same axis 6th can be attached like the inside wheel 5 . The electronic braking system 3 in the step 28 also check the current lateral acceleration 4th is greater than the second limit value of the lateral acceleration 4th and only then initiate deceleration braking if this test is positive. If there is no risk of tipping over, it is done in one step 31 driving through the curve 13th continued without deceleration.

The steps 20th to 31 can while driving through the curve 13th repeated over and over again.

A schematic flow diagram of the process 32 to determine the height of the center of gravity 10 , for example by means of the brake control unit 10 and for example with the software 17th can be done is in 8th shown. This is done in one step 33 the static axle load 8th for the axis 6th at which the wheel on the inside of the curve 5 is arranged, determined. For example, data from on the axis 6th arranged sensors are queried. It is possible that provided the vehicle 1 has an air suspension, in air suspension bellows of the axis 6th Pressure sensors are arranged, from the data of which the axle load can be determined. In one step 34 becomes the dynamic wheel load 9 of the inside wheel 5 determined. For example, data from on the inside wheel 5 arranged sensors are queried. It is possible, as explained for the example of the air suspension, that the static axle load is determined 8th and determining the dynamic wheel load 9 originally used sensors on the vehicle for a different purpose 1 are arranged and act primarily as a component of another system or another process flow. The steps 33 and 34 can take place in any order and at the same time. In one step 35 becomes the center of gravity height 10 using the static axle load 8th and the dynamic wheel load 9 certainly.

$$M_{\text{innen}}=\surd \left({\left(F_{\text{z}\text{,Brems}\text{,innen}}\text{/}g\right)}^2\text{/}\left({\mu }^2-\left({\ddot{y}}_{\text{ist}}{}^2\text{/}{g}^2\right)\right)\right)$$

$$a_{\text{q}\text{,crit}}={\ddot{y}}_{\text{crit}}\text{/}g=\left(M_{\text{Rad}}-M_{\text{Rest}}\right)\cdot {\ddot{y}}_{\text{ist}}\text{/}\left(\left(M_{\text{Rad}}-M_{\text{innen}}\right)\cdot g\right)$$

$$H_{\text{SP}}=\left(M_{\text{Rad}}-M_{\text{innen}}\right)\cdot s\text{/}\left(M_{\text{Achse}}\cdot {\ddot{y}}_{\text{ist}}\text{/}g\right)$$

mit

aq,crit

auf die Erdbeschleunigung g normierte Querbeschleunigung ÿ_crit

Fz,Brems

berechnete Vertikalkraft eines Rads auf Basis der Bremsberechnung und des aktuellen Bremsdrucks bei Geradeausfahrt

Fz,Brems,innen

berechnete Vertikalkraft des kurveninneren Rads auf Basis der Bremsberechnung und des aktuellen Bremsdrucks bei Geradeausfahrt

Fz,voll

Achsvertikalkraft beladen

Fz,leer

Achsvertikalkraft leer

g

Erdbeschleunigung

HSP

Schwerpunkthöhe

MAchse

Achslast

Minnen

aktuelle dynamische Radlast kurveninneres Rad

MRad

mittlere Radlast, halbe Achslast

MRest

kritische Restradlast, vom Systemhersteller vorgegeben als Parameter

pist

Bremsdruck aktuell

pleer

Bremsdruck, bei dem Räder des leeren Fahrzeugs blockieren

pvoll

Bremsdruck, bei dem Räder des vollen Fahrzeugs blockieren

s

Spurweite

ÿcrit

kritische Querbeschleunigung, bei der Verzögerungsbremsung gestartet werden soll

ÿist

aktuelle Querbeschleunigung

z

auf die Erdbeschleunigung g normierte Abbremsung

µ

Reibwert (angenommen mit 0,7 für trockene Straße)

Formulas $$\begin{array}{l}{\mathrm{F.}}_{\text{z}\text{, Brake}}=\\ 1\text{/}2\cdot z\cdot \left(\left({\mathrm{F.}}_{\text{z}\text{,full}}-{\mathrm{F.}}_{\text{z}\text{,empty}}\right)\cdot p_{\text{is}}\text{/}\left(p_{\text{full}}-p_{\text{empty}}\right)+\left(p_{\text{full}}\cdot {\mathrm{F.}}_{\text{z}\text{,empty}}-p_{\text{empty}}\cdot {\mathrm{F.}}_{\text{z}\text{,full}}\right)\text{/}\left(p_{\text{full}}-p_{\text{empty}}\right)\right)\end{array}$$

$${\mathrm{M.}}_{\text{Inside}}=\surd \left({\left({\mathrm{F.}}_{\text{z}\text{, Brake}\text{,Inside}}\text{/}G\right)}^2\text{/}\left({\mu }^2-\left({\ddot{y}}_{\text{is}}{}^2\text{/}{G}^2\right)\right)\right)$$

$$a_{\text{q}\text{, crit}}={\ddot{y}}_{\text{crit}}\text{/}G=\left({\mathrm{M.}}_{\text{wheel}}-{\mathrm{M.}}_{\text{rest}}\right)\cdot {\ddot{y}}_{\text{is}}\text{/}\left(\left({\mathrm{M.}}_{\text{wheel}}-{\mathrm{M.}}_{\text{Inside}}\right)\cdot G\right)$$

$$H_{\text{SP}}=\left({\mathrm{M.}}_{\text{wheel}}-{\mathrm{M.}}_{\text{Inside}}\right)\cdot s\text{/}\left({\mathrm{M.}}_{\text{axis}}\cdot {\ddot{y}}_{\text{is}}\text{/}G\right)$$

With

aq, crit

_Lateral acceleration ÿ crit normalized to the acceleration due to gravity g

Fz, brake

Calculated vertical force of a wheel based on the brake calculation and the current brake pressure when driving straight ahead

Fz, brake, inside

Calculated vertical force of the wheel on the inside of the curve based on the brake calculation and the current brake pressure when driving straight ahead

Fz, full

Axial vertical force loaded

Fz, empty

Axial vertical force empty

G

Acceleration due to gravity

HSP

Center of gravity

Axis

Axle load

Love

Current dynamic wheel load on the inside wheel

MRad

medium wheel load, half axle load

MRest

critical residual wheel load, specified as a parameter by the system manufacturer

pist

Brake pressure currently

pleer

Brake pressure at which the wheels of the empty vehicle lock

pful

Brake pressure at which the wheels of the full vehicle lock

s

Gauge

ÿcrit

critical lateral acceleration at which deceleration braking should be started

is

current lateral acceleration

z

Deceleration normalized to the acceleration due to gravity g

µ

Coefficient of friction (assumed 0.7 for dry roads)

List of reference symbols

1

vehicle

2

Longitudinal axis

3

electronic braking system

4th

Lateral acceleration

5

inside wheel

6th

axis

7th

outside wheel

8th

Axle load

9

Wheel load

10

Center of gravity

11

Brake control unit

12th

Procedure

13th

Curve

14th

wheel

15th

Subsystem

16

Wheel contact plane

17th

software

18th

main emphasis

19th

Gauge

20th

step

21

step

22nd

step

23

step

24

Test braking

25th

step

26th

step

27

step

28

step

29

step

30th

step

31

step

32

Procedure

33

step

34

step

35

step

outside

Speed of the outside wheel

ninnen

Speed of the wheel on the inside of the curve

pist

current brake pressure

t

time

tTB

Start of test braking

tVB

Start of deceleration braking

is

current lateral acceleration

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 19602879 C1 [0002]
• EP 1142768 B1 [0002]

Claims (8)

Method (12) for preventing a vehicle (1) from tipping over about its longitudinal axis (2), in which an electronic brake system (3) evaluates a current transverse acceleration (4) and, after a first limit value of the transverse acceleration (4) is exceeded, a test braking from electronic braking system (3) is carried out, and in which an inside wheel (5) of an axle (6) that locks or tends to lock during the test braking triggers deceleration braking of at least one outside wheel (7), characterized in that if, after exceeding of the first limit value and, during the test braking of the electronic brake system (3), additional braking is carried out with a current brake pressure, which results in locking or a tendency to lock the wheel (5) on the inside of the curve, first a second limit value of the transverse acceleration (4) using the current Brake pressure calculated and instead of the first limit value an assessment of a G The risk of tipping over is taken as a basis. Method (12) according to Claim 1 , characterized in that deceleration braking is only carried out if the current transverse acceleration (4) is greater than the second limit value of the transverse acceleration (4). Method (12) according to Claim 1 or 2 , characterized in that the current lateral acceleration (4) and / or a current axle load (8) and / or wheel load (9) are also used to calculate the second limit value of the transverse acceleration (4). Method (12) according to one of the Claims 1 to 3 , characterized in that one or more of the following parameters are additionally used for the calculation of the second limit value of the transverse acceleration (4): a) deceleration, from braking calculation, b) axle vertical force fully loaded, from braking calculation, c) axle vertical force empty, from braking calculation, d ) Brake pressure to lock, empty, from the brake calculation, e) Brake pressure to lock, full, from the brake calculation, f) Current wheel load (9) of the wheel on the inside of the curve (5), g) Calculated vertical force of the wheel on the inside of the curve (5), h) Static axle load (8), i) critical residual wheel load, specified. Method (12) according to one of the Claims 1 to 4th , characterized in that a center of gravity (10) is calculated from a calculated current wheel load (9) of the wheel (5) on the inside of the curve and a static axle load (8) and is used to adapt the first or second limit value of the transverse acceleration (4). Method (32) for determining a center of gravity height (10) of a vehicle (1) with an electronic brake system (3), characterized by a calculation of the center of gravity height (10) using a dynamic wheel load (9) of a wheel (5) on the inside of the curve and a static one Axle load (8). Brake control device (11) with software (17) for carrying out the method (12) according to one of the Claims 1 to 5 and / or the method (32) according to Claim 6 . Electronic brake system (3) with a brake control unit (11) Claim 7 .

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