WO2001051327A1

WO2001051327A1 - Method for increasing the manoeuvrability and driving stability of a vehicle during cornering

Info

Publication number: WO2001051327A1
Application number: PCT/EP2001/000265
Authority: WO
Inventors: Ivica Batistic; Robert Schmidt; Wolfgang Kling; Andreas Kohl
Original assignee: Continental Teves Ag & Co. Ohg
Priority date: 2000-01-13
Filing date: 2001-01-11
Publication date: 2001-07-19
Also published as: EP1250250A1; JP2003519590A; DE10101197A1

Abstract

The invention relates to a method for increasing the manoeuvrability and driving stability of a motor vehicle during cornering. To this end, the turning behaviour or the wheel slip of the individual wheels is monitored and the distribution of braking force to the outside wheels (in relation to the corner) compared to the distribution of braking force to the inside wheels (in relation to the corner) is varied according to the wheel turning behaviour or the wheel slip of the wheels. When cornering is detected, an overall deceleration of the vehicle corresponding to the driver's wishes is determined and carried out by increasing the braking force (ΔP1) on said outside wheel(s) and reducing or maintaining the braking force (ΔP2) on said inside wheels.

Description

Method for increasing the steerability and / or driving stability of a vehicle when cornering

The invention relates to a method for increasing the steerability and / or driving stability of a motor vehicle equipped with a controlled braking system, in which the turning behavior and / or the wheel slip of the individual vehicle wheels is observed when cornering and in which the distribution of the braking force on the curve detection Varies on the outside of the bend and on the bends on the inside of the bend are varied depending on the wheel turning behavior and / or the wheel slip. A brake system for performing the method is also part of the invention.

Such a method is already known from DE 195 22 632 A1, in which a switch is made from a normal control mode to a cornering control mode in order to improve the steerability of the vehicle and the driving stability when cornering is detected. In this special mode, the average pressure level of the front wheel on the inside of the curve is lowered by a predetermined value and the average pressure level of the front wheel on the outside of the curve is raised by a predetermined value compared to the normal control mode. It is a process for improving the control behavior of an anti-lock control system (ABS) when cornering, which is why the designation ABSplus (improved ABS) or ESBS (Enhanced Stability Brake System) is used. An increase in brake pressure (on the front wheel on the outside of the curve) via the pre-pressure caused by the brake pedal actuation is neither provided nor possible.

BESTÄΓIGUNGSKOPIE Furthermore, it is known from DE 196 48 909 AI to improve the control behavior of an anti-lock brake system that is capable of active braking, if a deceleration of the vehicle is detected during cornering deceleration without brake application and if at the same time a critical on turning in of the vehicle ( wheel slip condition indicating oversteer) is met to initiate a special regulation which effects the introduction of brake pressure into the wheel brake of the front wheel on the outside of the curve. This special regulation, which prevents the vehicle from oversteering, only works when the brake is not applied.

It is an object of the present invention to further develop a method or brake system of the type mentioned at the outset such that when cornering, changing lanes or similar maneuvers, both good steerability and high driving stability as well as a short braking distance or a precise (due to the dimension The driver's wish expressed in a corresponding vehicle deceleration is to be achieved both in emergency braking situations and with "timid" pedal actuation.

It has been shown that this task can be achieved with the method described in claim 1, the special feature of which is that, when cornering detection, an overall deceleration of the vehicle corresponding to the driver's request is determined and that by increasing the braking force on the front wheel and / or rear wheel on the outside the braking force corresponding to the driver's request and lowering of the braking force or keeping the braking force constant on or on the wheels on the inside of the curve brings about the vehicle deceleration corresponding to the pedal force or the driver's request

BESTÄΠGUNGSKOPIE becomes .

According to the invention, in order to compensate for oversteering driving behavior, which can occur, for example, when cornering, when suddenly changing lanes, etc., the braking pressure and thus the braking force on the front wheel on the outside of the curve is increased, on the other hand, it is lowered or kept constant on the front wheel on the inside of the curve. The asymmetrical distribution of the braking forces on the front axle is adapted to the driving condition by the control system.

In conventional systems with improved maneuverability by changing the pressure level on the outside and inside wheel, the braking system is designed - the (increased) brake pressure on the outside wheel cannot or must not exceed the pre-pressure specified by the pedal actuation or the braking force specified by the pedal force. As a result, the overall deceleration of the vehicle is inevitably less than when driving straight ahead or cornering with the same brake pressures on the wheels on the outside of the curve and on the inside of the curve. This is at least irritating for the driver and requires adaptation to the special situation. By contrast, the method according to the invention achieves the total deceleration desired by the driver even when cornering, when there is a sudden lane change, etc.

A pressure build-up on the wheel on the outside of the curve beyond the driver's specification is advantageous as a result of the method according to the invention even in the case of low driver pressure specifications in which the necessary stabilizing torque could not be applied simply by reducing the pressure (on the wheel on the inside of the curve).

BESTÄΠGÜ GSKDPME According to advantageous, alternative exemplary embodiments of the method according to the invention, the increase in the braking force on the wheels on the outside of the curve and the reduction on the wheels on the inside of the curve can be brought about in steps simultaneously or within a predetermined period of time, for example by pressure change pulses or pressure change pulse sequences. On the other hand, it is also possible and in many cases also advantageous to carry out the increase on the wheels on the outside of the curve and the corresponding lowering on the wheels on the inside of the curve at different times, with the braking force being increased, for example, by a predetermined time period in the order of 50 ms to 500 ms offset should be brought about after the brake force reduction on the inside wheel or on the inside wheels.

A brake system which is particularly suitable for carrying out the method according to the invention is a so-called. Brake-by-wire system (BBW), e.g. designed as an electro-hydraulic brake system (EMS) or electromechanical brake system (EMB). In such brake systems, the pedal actuation or the driver's request expressed by the pedal actuation is recorded in principle and transmitted in the form of an electrical signal to the brake force generator. With such systems, there is no difficulty in realizing an increase in braking force on the outside wheel beyond the driver's request.

In the attached subclaims, further advantageous exemplary embodiments of the method according to the invention and of brake systems for carrying out the method are described.

Further advantages, features and possible applications of the Invention emerge from the following description of details and exemplary embodiments with reference to the attached figures.

Show it:

1 schematically simplified a brake system for performing the method according to the invention,

2 schematically simplified components of a brake system according to the invention,

Fig. 3 shows another embodiment of a brake system according to the invention, and

4 in the diagram the course of the brake pressure difference on the inside and outside of the curve front wheel according to an exemplary embodiment of the invention.

The "driver request" expressed by actuation of the brake pedal is, according to the principle of the invention illustrated with reference to FIG. 1, first by a block designated EBV (electronic brake force distribution) in brake force components or pressure components Pi to P ₄ for the individual vehicle wheels 1 to 4 implemented. In a subsequent block or processing stage 2, which is referred to in FIG. 1 as “ESBS pressure distribution” (brake systems of this type are known in specialist circles as “ABSplus” systems or “enhanced stability brake systems”), these are the individual wheels assigned pressure or braking force components P ₁ to P ₄ when cornering detection (KFE) are modified according to the specifications of the method according to the invention, so that pressure or braking force components Pi 'to P ₄ ' are available at the output of stage 2.

BESTÄTlGUNGSKDPff Curve detection can be implemented in very different ways. For example, curve detection by observing the slip course of the individual wheels is known. The result is at least apparently a different slip on the bend-outer wheels compared to the kur ^¬ veninneren vehicle wheels.

An oversteering vehicle is shown symbolically in the lower part of FIG. 1 in order to illustrate that when the method according to the invention is applied, the pressure (or the braking force) Pi calculated in stage 1 on the outer front wheel V _au increases by a certain amount ΔP _X , however, the pressure P ₂ on the curve-inward front wheel V _ιn a Dif ^¬ ferenz pressure .DELTA.P ₂ is lowered. As a result, the brake pressure Pi 'prevailing at the front wheel on the outside of the curve becomes higher than the brake pressure P _λ corresponding to the driver's request. According to the invention, this is of crucial importance.

In Fig. 2, as a further exemplary embodiment of the invention, a brake system is shown schematically, in which the pedal force or the pressure "P _stat • 1 • • 4" expressing the "driver's request", which applies in the static state of the vehicle and when driving straight ahead, is supplied on the one hand a brake of a force splitter 3 (EBV) and on the other hand, a call as "ESBS" ^¬ th stage 4, in which the special conditions to be considered when cornering. The dynamic components "P _dyn (EBV) 1..4" calculated by the electronic brake force distribution EBV 3 and the dynamic components P _dyn (ESBS) 1 .. dependent on cornering are finally calculated in a distribution stage 5 called "pressure arbitration" evaluated the components "P _dyn 1..4" supplied to the individual vehicle wheels.

BESTÄTΪGUNGSKOPIE 3 shows yet another exemplary embodiment of a brake system for carrying out the method according to the invention. The "driver request detection" symbolizes a block 6, the output signal of which is fed to an electronic brake force distribution 7, which takes the static conditions into account. An arithmetic unit 8, which represents an adaptation algorithm for the adaptive portion of the braking force distribution under static conditions, is used for detecting the driving situation (cornering or driving straight ahead, road disturbance, etc.), for processing the speeds Vi to V _{4 of} the individual vehicle wheels and for evaluating these input variables.

The output information or signals of the static brake force distribution 7, namely the individual components "Plstat" to "P4stat", are finally in a block 9, in which the dynamic components "Pldyn" to "P4dyn" of the brake force distribution based on the static components "Plstat "to" P4stat "and the wheel speeds Vi to 4 are calculated, evaluated.

3 shows the brake force distribution concept of a brake-by-wire system, especially an electro-hydraulic brake system (EHD), in which the invention is used.

Finally, FIG. 4 shows a diagram to illustrate a further exemplary embodiment of the invention, which consists in that the pressure difference components to take into account cornering, namely the pressure compensation components ΔPi, -ΔP ₂ (see FIG. 1), offset the wheel brake pressure Pi in time, P ₂ (see Fig. 1) can be added in order to achieve a comfortable state of the necessary To ensure yaw moment to support cornering. The pressure correction begins at time t ₀ . First, in the exemplary embodiment shown, a pressure reduction pulse on the front wheel on the inside of the curve reduces the wheel brake pressure by approximately 5 bar (corresponds to ΔP ₂ in FIG. 1) and only then, after 200 ms at time ti, the wheel brake pressure on the front wheel on the outside of the curve, also by 5 bar

(ΔPi) increased. This is repeated after a pause of approximately 1 s. In practice, these changes in braking force or pressure are implemented by pulse sequences, as in the example according to FIG. 4, or by precisely calculated individual pulses. The duration of the pressure change pulses can e.g. are in the order of 50 ms to a few 100 ms.

In other cases, however, a simultaneous increase in braking force or brake pressure on the respective front wheels by means of individual pulses or pulse sequences was sufficient.

BESTÄΠGUNGSKΓÄ

Claims

claims

1. A method for increasing the steerability and / or the driving stability of a motor vehicle equipped with a controlled braking system, in which the turning behavior and / or the wheel slip of the individual vehicle wheels is observed when cornering and in which, when cornering, the distribution of the braking force to the outside wheels and on the inside wheel is varied depending on the wheel turning behavior and / or the wheel slip, characterized in that when cornering detection a vehicle deceleration corresponding to the driver's request is determined and that by increasing the braking force on the outside front wheel and / or on the outside rear wheel via the braking force corresponding to the driver's request addition and lowering the braking force on the wheel or wheels inside the curve, the vehicle deceleration corresponding to the driver's request is brought about.

2. The method according to claim 1, characterized in that the increase in the braking force on the outside wheels and the lowering on the inside wheels simultaneously or within a predetermined period of time in stages, e.g. are brought about by pressure change pulses or pulse sequences.

3. The method according to claim 1, characterized in that the increase in the braking force on the outside wheels and the lowering on the inside wheels are offset from one another in time, for example by a period of the order of 50 to 500 ms, in particular 200 ms, are brought about.

4. The method according to claim 3, characterized in that the increase in the braking force on the wheels on the outside of the curve is initiated following the reduction in the braking force on the wheels on the inside of the curve or on the corresponding reduction pulse.

5. The method according to one or more of claims 1 to 4, characterized in that a plurality of successive increases in braking force and reductions in braking force at predetermined intervals of e.g. 1 to 2 seconds.

6. Brake system for performing the method according to one or more of claims 1 to 5, characterized in that it is in the form of a "brake-by-wire" system, e.g. an electro-hydraulic brake system (EHB) or an electromechanical brake system (EMB).

7. Brake system according to claim 6, characterized in that it comprises an EBV control (electronic brake force distribution), in which the static distribution of the brake pressures on the front and rear axles of the motor vehicle is determined by characteristic curves

(Fig. 2, Fig. 3).

8. Brake system according to claim 6 or 7, characterized in that for the adaptation of the brake force distribution (EBV), the static characteristics of the brake raft distribution are adapted to the load condition of the vehicle and the condition of the brake system by means of a superimposed algorithm, the adaptation by evaluating the Wheel speed information and internal control states are carried out.

BESTÄΠGUNGSKGPIE

9. Brake system according to one or more of claims 6 to 8, characterized in that additional sensors present in the vehicle, such as the steering angle sensor, lateral acceleration sensor, longitudinal acceleration sensor and yaw rate sensor, are evaluated to improve and safeguard the input information of the brake system.

10. Brake system according to one or more of claims 6 to 9, characterized in that an EBV control stage is present which, from the static specification of the brake pressure and the behavior of the vehicle during cornering, has the optimum distribution of the brake pressure of all wheels in the current driving situation calculated.

11. Brake system according to claim 10, characterized in that the EBV control stage is designed such that the resulting total deceleration of the vehicle also corresponds to the driver's request during the EBV function.

BESTÄTIGUNGSKQPIE