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DE4414657A1 - Critical safe driving speed determination method for motor vehicle - Google Patents

Critical safe driving speed determination method for motor vehicle

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Publication number
DE4414657A1
DE4414657A1 DE4414657A DE4414657A DE4414657A1 DE 4414657 A1 DE4414657 A1 DE 4414657A1 DE 4414657 A DE4414657 A DE 4414657A DE 4414657 A DE4414657 A DE 4414657A DE 4414657 A1 DE4414657 A1 DE 4414657A1
Authority
DE
Germany
Prior art keywords
speed
wheel
driving speed
max
visibility
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
DE4414657A
Other languages
German (de)
Other versions
DE4414657C2 (en
Inventor
Ulrich Prof Dr Seiffert
Ralf Dr Bergholz
Gunnar Dipl Ing Larsson
Ernst Dipl Ing Lissel
Peter Dipl Ing Andreas
Raimond Dipl Ing Holze
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Volkswagen AG
Original Assignee
Volkswagen AG
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Filing date
Publication date
Application filed by Volkswagen AG filed Critical Volkswagen AG
Priority to DE4414657A priority Critical patent/DE4414657C2/en
Publication of DE4414657A1 publication Critical patent/DE4414657A1/en
Application granted granted Critical
Publication of DE4414657C2 publication Critical patent/DE4414657C2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K31/00—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator
    • B60K31/18—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator including a device to audibly, visibly, or otherwise signal the existence of unusual or unintended speed
    • B60K31/185—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator including a device to audibly, visibly, or otherwise signal the existence of unusual or unintended speed connected to the speedometer display, e.g. by sensors or switches responsive to the position of the indicator needle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K31/00—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K31/00—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator
    • B60K31/0008—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator including means for detecting potential obstacles in vehicle path
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/17—Using electrical or electronic regulation means to control braking
    • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/07—Indicating devices, e.g. for remote indication
    • G01P1/08—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers
    • G01P1/10—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds
    • G01P1/103—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds by comparing the value of the measured signal with one or several reference values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2552/00—Input parameters relating to infrastructure
    • B60W2552/40—Coefficient of friction

Landscapes

  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)

Abstract

The speed determination method makes use of the speed (drn) of one driven and one undriven wheel, and engine (M) torque (km) signals which are used by an ABS control (3) to assess wheel/road friction ( mu max) and hence wheel slip.A sensor (4) continuously monitors the ambient visibility (s) or vehicle separation, which can be subtracted by an extra distance safety factor (s0), and together with a driver reaction constant (tr) enables the computer (5) to derive a critical safe speed (Ve), which is compared with the actual velocity (v). The comparison result is displayed (2) by LED illumination of a hazard warning segment on the speedometer dial.

Description

Die Erfindung betrifft ein Verfahren zur Ermittlung einer kritischen Fahrgeschwindigkeit eines Kraftfahrzeuges während einer gefahrenträchigen Situation, bei dem momentane Sichtweite­ werte erfaßt und zur Berechnung der kritischen Fahrgeschwindigkeit verwendet werden.The invention relates to a method for determining a critical driving speed Motor vehicle during a dangerous situation with the current visibility values recorded and used to calculate the critical driving speed.

Zur Definition eines Gefährdungsgrades, in dem sich ein Fahrzeug aufgrund dichten Verkehrs­ aufkommens und geringer Sichtweite befindet, wird in der DE 42 14 870 A1 vorgeschlagen, über Abstandserfassungseinrichtungen den Weg zum vorausfahrenden Fahrzeug, die Relativ­ geschwindigkeit zwischen den beiden Fahrzeugen bzw. zwischen dem Fahrzeug und einem Hindernis und über ein Infrarot-Sichtweiten-Meßsystem die aktuelle Sichtweite sowie die Augenblicksgeschwindigkeit des Fahrzeugs und den Lenkwinkel zu erfassen. In Abhängigkeit dieser Größen wird in einem ersten Verfahrensschritt ein Maß für einen gefahrlosen Folge­ abstand zu einem Frontfahrzeug bzw. einem Hindernis definiert und damit ein Hinweis für eine ggf. vergrößerbare oder zu verringernde Augenblicksgeschwindigkeit zur Anzeige gebracht. In einem zweiten Verfahrensschritt wird in Abhängigkeit der gemessenen Sichtweite eine noch sicher fahrbare Geschwindigkeit berechnet und dieser Geschwindigkeitswert mit dem Ab­ standsgeschwindigkeitswert verglichen, wobei der geringere bzw. der negativere beider Werte zur Anzeige gebracht wird.To define a degree of danger in which a vehicle is due to heavy traffic and low visibility is proposed in DE 42 14 870 A1, The distance to the vehicle in front via distance detection devices, the relative speed between the two vehicles or between the vehicle and one Obstacle and an infrared visibility measuring system the current visibility and the Detect the instantaneous speed of the vehicle and the steering angle. Dependent on in a first process step, these quantities become a measure of a safe consequence distance to a front vehicle or an obstacle defined and thus an indication for a If necessary, the instantaneous speed, which can be increased or decreased, is displayed. In a second method step becomes a function of the measured visibility safely drivable speed calculated and this speed value with the Ab Steady speed value compared, the lower or the more negative of both values is displayed.

Neben einer eingeschränkten Sichtweite, beispielsweise bei Nebel, starkem Regen oder Schneefall hat jedoch auch der Zustand der Fahrbahn bzw. die Kraftschlußbedingungen zwischen der Fahrbahn und den Reifen der Räder einen wesentlichen Einfluß auf die Fahr­ sicherheit eines Kraftfahrzeuges. Insbesondere aus der Sicht einer wachsenden Verkehrs­ dichte ist es wichtig, neben der Sichtweite auch den aktuellen Fahrbahnzustand und damit ein Maß für den Bremsweg bei der Berechnung der kritischen Fahrgeschwindigkeit zu berücksichtigen.In addition to limited visibility, for example in fog, heavy rain or However, snowfall also has the condition of the roadway or the adhesion conditions between the road and the tires of the wheels have a significant impact on driving safety of a motor vehicle. Especially from the perspective of growing traffic It is important not only the visibility, but also the current state of the road and thus a density Measure of the braking distance when calculating the critical driving speed consider.

Die Aufgabe der Erfindung besteht deshalb darin, ein Verfahren zur Beurteilung einer ge­ fahrenträchigen Fahrsituation eines Kraftfahrzeuges zu schaffen, bei dem neben der mo­ mentanen Sichtweite auch der Fahrbahnzustand berücksichtigt wird.The object of the invention is therefore to provide a method for assessing a ge create driving-prone driving situation of a motor vehicle, in which in addition to the mo mental visibility, the road condition is also taken into account.

Die Aufgabe wird durch die Merkmale des Patentanspruchs gelöst. Vorteilhafte Weiterbil­ dungen und Ausgestaltungen der Erfindung sind in den Unteransprüchen angegeben.The object is achieved by the features of the patent claim. Advantageous training Applications and refinements of the invention are specified in the subclaims.

Gemäß der Erfindung werden in Abhängigkeit des momentanen Fahrbahnzustandes Werte für einen vorherrschenden Reibwert zwischen der Fahrbahn und mindestens einem Rad ermittelt und in einem weiteren Verfahrensschritt mindestens in Abhängigkeit der momentanen Sicht­ weite und der Werte für den vorherrschenden Reibwert die kritische Fahrgeschwindigkeit er­ mittelt.According to the invention, values for determines a prevailing coefficient of friction between the road surface and at least one wheel and in a further method step at least depending on the current view wide and the values for the prevailing coefficient of friction the critical driving speed averages.

Nach einer vorteilhaften Weiterbildung der Erfindung wird die kritische Fahrgeschwindigkeit im wesentlichen nach der BeziehungAccording to an advantageous development of the invention, the critical driving speed in essential after the relationship

ermittelt, wobei µmax der vorherrschende Reibwert zwischen der Fahrbahn und mindestens einem Rad, g die Erdbeschleunigung, tr ein Wert für die Reaktionszeit des Fahrzeugführers und s der momentane Sichtweitenwert ist. Der momentan vorherrschende Reibwert zwischen Fahrbahn und Rad des Kraftfahrzeuges, der ein Maß für den Glättezustand der Fahrbahn ist, wird dabei vorteilhafterweise in Abhängigkeit der Raddrehzahl mindestens eines Rades ermittelt. Dazu wird aus der Raddrehzahl in einer Auswerteschaltung der Radschlupf berechnet und unter Berücksichtigung eines Motorlastsignals auf den ungünstigstenfalls zur Verfügung stehenden Reibwert geschlossen.determined, where µ max is the prevailing coefficient of friction between the road surface and at least one wheel, g is the acceleration due to gravity, t r is a value for the reaction time of the vehicle driver and s is the instantaneous visibility value. The currently prevailing coefficient of friction between the road surface and the wheel of the motor vehicle, which is a measure of the smoothness of the road surface, is advantageously determined as a function of the wheel speed of at least one wheel. For this purpose, the wheel slip is calculated from the wheel speed in an evaluation circuit and, taking into account an engine load signal, a conclusion is drawn as to the worst case available friction coefficient.

Nach einer vorteilhaften Weiterbildung wird zur Ermittlung des vorherrschenden Reibwertes die Raddrehzahl mindestens eines angetriebenen und mindestens eines getriebenen Rades erfaßt und von den ermittelten Raddrehzahlen ein Mittelwert gebildet.According to an advantageous development, the prevailing coefficient of friction is determined the wheel speed of at least one driven and at least one driven wheel detected and averaged from the wheel speeds determined.

Zur Berücksichtigung einer hohen Verkehrsdichte wird gemäß einer vorteilhaften Weiterbil­ dung vorgeschlagen, daß in die Berechnung der kritischen Fahrgeschwindigkeit neben der Sichtweite und dem Fahrbahnzustand auch der Abstand zum vorausfahrenden Fahrzeug und/oder die Fahrgeschwindigkeit dieses Fahrzeuges eingeht. Statt der Fahrgeschwindigkeit des vorausfahrenden Fahrzeuges kann auch die Relativgeschwindigkeit zwischen beiden Fahrzeugen verwendet werden. In einer Ausgestaltung dieser Weiterbildung wird die gemes­ sene Sichtweite und der momentane Abstand zum vorausfahrenden Fahrzeug miteinander verglichen und die Berechnung der kritischen Fahrgeschwindigkeit erfolgt mit dem kleineren dieser Werte.To take into account a high traffic density, according to an advantageous development tion suggested that in the calculation of the critical driving speed in addition to the Visibility and the condition of the road, as well as the distance to the vehicle in front and / or the driving speed of this vehicle is received. Instead of driving speed of the vehicle in front can also be the relative speed between the two Vehicles are used. In one embodiment of this training, the measured  Visibility and the current distance to the vehicle in front with each other compared and the calculation of the critical driving speed is made with the smaller one of these values.

Die kritische, die Gefahrenträchigkeit der Fahrsituation wiedergebende Geschwindigkeit kann dabei auf unterschiedliche Weise zur Anzeige gebracht werden. Nach einer ersten Weiterbil­ dung der Erfindung wird die kritische Fahrgeschwindigkeit mittels einer Skala, vorzugsweise am Tachometer angezeigt, die bei abnehmender Sichtweite bzw. abnehmenden Abstand und/oder geringer werdenden Reibwerten von hohen zu niedrigen Geschwindigkeiten an­ wächst.The critical speed that reflects the danger of the driving situation being dangerous are displayed in different ways. After a first follow-up tion of the invention, the critical driving speed using a scale, preferably displayed on the tachometer, with decreasing visibility or decreasing distance and / or decreasing friction values from high to low speeds grows.

Eine andere Möglichkeit zur Warnanzeige besteht darin, bei Überschreitung der kritischen Fahrgeschwindigkeit eine Anzeige zu aktivieren. Diese Variante hat den Vorteil, daß der Fahrzeugführer nicht durch eine Daueranzeige belästigt wird, sondern nur im akuten Gefahrenfall, d. h. bei Überschreitung der kritischen Fahrgeschwindigkeit gewarnt wird.Another way of warning display is when the critical is exceeded Driving speed to activate a display. This variant has the advantage that the Driver is not bothered by a permanent display, but only in the acute Emergency, d. H. is warned if the critical driving speed is exceeded.

Der Vorteil der Erfindung besteht darin, daß der Fahrzeugführer ein genaues Maß für die Ge­ fährlichkeit seiner derzeitig gefahrenen Geschwindigkeit erhält und so durch evtl. Zurück­ nahme der Geschwindigkeit die Fahrsicherheit erhöhen kann.The advantage of the invention is that the driver has an accurate measure of the Ge dangerousness of his current speed and thus possibly back increase in speed can increase driving safety.

Nachfolgend wird das erfindungsgemäße Verfahren anhand eines Ausführungsbeispiels näher dargestellt. Die zugehörigen Zeichnungen zeigen:The method according to the invention is explained in more detail below using an exemplary embodiment shown. The associated drawings show:

Fig. 1 einen Ablaufplan des erfindungsgemäßen Verfahrens, Fig. 1 is a flowchart of the method according to the invention,

Fig. 2 eine Darstellung einer ersten Möglichkeit der Anzeige und Fig. 2 shows a first possibility of the display and

Fig. 3 eine Darstellung einer zweiten Möglichkeit der Anzeige der kritischen Fahrgeschwindigkeit. Fig. 3 shows a second way of displaying the critical speed.

Wie in Fig. 1 gezeigt, werden von den bereits für das ABS-System vorgesehenen Raddreh­ zahlsensoren 1 die Raddrehzahlen drn erfaßt und in einer Rechenschaltung 3 aus den Rad­ drehzahlen drn sowohl der überwachten angetriebenen Räder als auch zumindest eines der nicht angetriebenen Räder der Radschlupf λm nach der Beziehung:As shown in Fig. 1, from the wheel speed sensors 1 already provided for the ABS system, the wheel speeds d rn are detected and in a computing circuit 3 from the wheel speeds d rn both of the monitored driven wheels and at least one of the non-driven wheels Wheel slip λ m according to the relationship:

ermittelt. In der Beziehung bedeuten sA die während der definierten Zeitdauer bzw. Weg­ strecke vom Radsensor 1 des überwachten angetriebenen Rades erzeugte Signalimpuls­ summe, sN die vom Radsensor 1b des nicht angetriebenen, d. h. frei rollenden Rades erzeugte Signalsumme und k ein Kalibrierfaktor, der unter anderem Änderungen z. B. an den Reifenprofilen an nur einem der Teil der Räder oder die Änderungen der Reifentemperatur berücksichtigt. In der Rechenschaltung 3 wird weiterhin unter Einbeziehung eines Motorlast­ signals km auf den ungünstigstenfalls zur Verfügung stehenden Reibwert µmax zwischen Fahrbahn und Rad geschlossen und so ein Maß für die vorherrschenden Fahrbahnverhält­ nisse erhalten. Ein weiterer Sensor 4, beispielsweise ein Infrarot-Sensor, erfaßt die momen­ tane Sichtweite des Fahrzeugführers und im Rechner 5 wird aus diesen Größen unter Einbeziehung eines Erfahrungswertes für die Reaktionszeit tr des Fahrzeugführers eine bei den vorliegenden Straßenverhältnissen zu empfehlende Geschwindigkeit ve ermittelt, bei der ein Auffahren auf ein Hindernis oder auf ein vorausfahrendes Fahrzeug bei eingeschränkter Sichtweite und evtl. verlängertem Bremsweg vermieden werden kann. Als zusätzlicher Sicher­ heitsfaktor kann es sinnvoll sein, nicht die aktuelle Sichtweite s, sondern eine um einen Sicherheitsweg s0 verminderte Sichtweite s in die Berechnung einfließen zu lassen.determined. In the relationship, s A means the signal pulse sum generated by the wheel sensor 1 of the monitored driven wheel during the defined period of time or distance, s N the signal sum generated by the wheel sensor 1 b of the non-driven, ie freely rolling wheel, and k a calibration factor which is below other changes e.g. B. the tire treads on only one of the part of the wheels or the changes in the tire temperature are taken into account. In the arithmetic circuit 3 , a motor load signal k m is also used to infer the worst-case available coefficient of friction μ max between the road surface and the wheel, thus obtaining a measure of the prevailing road surface conditions. Another sensor 4 , for example an infrared sensor, detects the current range of vision of the vehicle driver and in computer 5 a recommended speed v e is determined from these variables, including an empirical value for the reaction time t r of the vehicle driver, in the present road conditions a collision with an obstacle or a vehicle in front with restricted visibility and possibly an extended braking distance can be avoided. As an additional safety factor, it can make sense not to include the current visibility range s, but a visibility range s reduced by a safety path s0.

Neben der Sichtweite s kann es, insbesondere bei hohem Verkehrsaufkommen, von Vorteil sein den Abstand sf zu einem vorausfahrenden Fahrzeug bei der Geschwindigkeitsberech­ nung zu berücksichtigen. In diesem Fall wird die aktuelle Sichtweite s laufend mit den Ausgangssignalen sf eines hier nicht dargestellten Abstandssensors verglichen, wobei der kleinere der Entfernungswerte s, sf für die Berechnung der kritischen bzw. zu empfehlenden Geschwindigkeit ve verwendet wird.In addition to the visibility range s, it may be advantageous to take the distance s f from a vehicle in front into account when calculating the speed, especially in the case of high traffic. In this case, the current visibility range s is continuously compared with the output signals s f of a distance sensor, not shown here, the smaller of the distance values s, s f being used for the calculation of the critical or recommended speed v e .

Die kritische Geschwindigkeit ve wird beispielsweise durch eine zusätzliche Anzeige 2 auf dem Tachometer des Fahrzeuges für den Fahrzeugführer sichtbar gemacht, der ein Maß für die Gefährlichkeit der derzeit gefahrenen Geschwindigkeit erhält und somit seine Geschwindigkeit den Witterungsbedingungen bzw. dem Verkehrsaufkommen anpassen kann.The critical speed v e is made visible to the driver, for example, by an additional display 2 on the speedometer of the vehicle, which receives a measure of the dangerousness of the speed currently being driven and can thus adapt its speed to the weather conditions or the traffic volume.

Gemäß der Fig. 2 und 3 kann die kritische Geschwindigkeit ve durch zwei unterschiedliche Möglichkeiten zur Anzeige gebracht werden. In Fig. 2 werden ausgehend von der kritischen Geschwindigkeit ve die höheren Geschwindigkeiten über ein Farbband 6 gekennzeichnet. Dies kann beispielsweise durch die Aktivierung von im Tachometer angeordneten Leucht­ dioden realisiert werden. Diese Variante hat jedoch den Nachteil, daß der Fahrzeugführer auch beim Fahren im unkritischen Geschwindigkeitsbereich einer Daueranzeige ausgesetzt ist. According to FIGS. 2 and 3, the critical speed v e can be displayed in two different ways. In Fig. 2, starting from the critical speed v e, the higher speeds are identified by an ink ribbon 6 . This can be achieved, for example, by activating light-emitting diodes arranged in the speedometer. However, this variant has the disadvantage that the vehicle driver is exposed to a continuous display even when driving in the non-critical speed range.

Eine andere Möglichkeit zur Warnanzeige ist in Fig. 3 gezeigt. Hier wird nur bei Überschrei­ tung der kritischen Geschwindigkeit ve ein Leuchtsegment bzw. -balken 8 aktiviert und somit nur im akuten Gefahrenfall gewarnt.Another possibility for warning display is shown in Fig. 3. A light segment or bar 8 is activated here only when the critical speed v e is exceeded and is therefore only warned in the event of an acute danger.

BezugszeichenlisteReference list

µmax = Reibwert
s = Sichtweite
ve = kritische Fahrgeschwindigkeit
g = Konstante
tr = Reaktionszeit
sf = Abstand
drn = Raddrehzahl
km = Motorlastsignal
vf = Fahrgeschwindigkeit
λm = Radschlupf
SA, SN = Signal der Radsensoren
k = Kalibrierfaktor
1 = Raddrehzahlsensor
2 = Anzeige
3 = Rechenschaltung
4 = Sensor
5 = Rechner
6 = Farbband
7 = Tachometer
8 = Leuchtbalkenµ max = coefficient of friction
s = visibility
v e = critical driving speed
g = constant
t r = response time
s f = distance
d rn = wheel speed
k m = engine load signal
v f = driving speed
λ m = wheel slip
S A , S N = signal from the wheel sensors
k = calibration factor
1 = wheel speed sensor
2 = display
3 = arithmetic circuit
4 = sensor
5 = calculator
6 = ribbon
7 = speedometer
8 = light bar

Claims (9)

1. Verfahren zur Ermittlung einer kritischen Fahrgeschwindigkeit eines Kraftfahrzeuges während einer gefahrenträchigen Situation, bei dem momentane Sichtweitenwerte erfaßt werden, dadurch gekennzeichnet, daß in Abhängigkeit des momentanen fahrbaren Zu­ standes Werte für einen vorherrschenden Reibwert (µmax) zwischen der Fahrbahn und mindestens einem Rad ermittelt werden und in einem weiteren Verfahrensschritt min­ destens in Abhängigkeit der momentanen Sichtweite (s) und der Werte für den vorherr­ schenden Reibwert (µmax) die kritische Fahrgeschwindigkeit (ve) ermittelt und zur Anzeige (2) gebracht wird.1. A method for determining a critical driving speed of a motor vehicle during a gefahrenträchigen situation, are detected in the instantaneous visual range values, characterized in that the current mobile determined as a function to the prior values for a prevailing friction coefficient (μ max) between the road surface and at least one wheel are determined and in a further method step at least as a function of the current visibility (s) and the values for the prevailing coefficient of friction (µ max ), the critical driving speed (v e ) is determined and displayed ( 2 ). 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die zulässige Fahrgeschwin­ digkeit (ve) im wesentlichen der Beziehung: gehorcht, wobei µmax der vorherrschende Reibwert zwischen der Fahrbahn und minde­ stens einem Rad, (g) eine Konstante, (tr) ein Wert für die Reaktionszeit des Fahrzeug­ führers und (s) der momentane Sichtweitenwert ist.2. The method according to claim 1, characterized in that the permissible Fahrgeschwin speed (v e ) essentially the relationship: obeys, where µ max is the prevailing coefficient of friction between the road and at least one wheel, (g) a constant, (t r ) a value for the driver's reaction time and (s) the current visibility value. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der momentan vorherr­ schende Reibwert (µmax) in Abhängigkeit der Raddrehzahl (drn) mindestens eines Rades (1) und eines Motorlastsignals (km) ermittelt wird.3. The method according to claim 1 or 2, characterized in that the currently prevailing friction coefficient (µ max ) is determined as a function of the wheel speed (d rn ) of at least one wheel ( 1 ) and an engine load signal (k m ). 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß zur Ermittlung des vorherr­ schenden Reibwertes (µmax) die Raddrehzahl (drn) mindestes eines angetriebenen und mindestens eines nicht angetriebenen Rades erfaßt wird und von den ermittelten Raddrehzahlen (drn) ein Mittelwert gebildet wird. 4. The method according to claim 3, characterized in that for determining the prevailing coefficient of friction (µ max ) the wheel speed (d rn ) at least one driven and at least one non-driven wheel is detected and an average value is formed from the determined wheel speeds (d rn ) becomes. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die kritische Fahrgeschwindigkeit (ve) außerdem in Abhängigkeit des Abstandes (sf) und/oder der Fahrgeschwindigkeit (vf) eines vorausfahrenden Fahrzeuges berechnet wird.5. The method according to any one of claims 1 to 4, characterized in that the critical driving speed (v e ) is also calculated as a function of the distance (s f ) and / or the driving speed (v f ) of a preceding vehicle. 6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß die Sichtweite (s) und der Ab­ stand (sf) des vorausfahrenden Fahrzeuges miteinander verglichen werden und die Be­ rechnung der kritischen Fahrgeschwindigkeit (ve) mit dem kleineren Wert erfolgt.6. The method according to claim 5, characterized in that the visibility (s) and the Ab stand (s f ) of the preceding vehicle are compared with each other and the calculation of the critical driving speed (v e ) is carried out with the smaller value. 7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß bei der Ermittlung der kritischen Fahrgeschwindigkeit (ve) eine um einen Sicherheitsweg (s0) verminderte Sichtweite (s-s0) verwendet wird.7. The method according to any one of claims 1 to 6, characterized in that in the determination of the critical driving speed (v e ) by a safety path (s0) reduced visibility (s-s0) is used. 8. Verfahren nach einem der Ansprüche 1 bis 7; dadurch gekennzeichnet, daß die kritische Fahrgeschwindigkeit (ve) mittels einer Skala (2) angezeigt wird, die bei abnehmender Sichtweite (s) bzw. abnehmenden Abstand (sf) des vorausfahrenden Fahrzeuges und/oder kleiner werdenden Reibwerten (µmax) von hohen zu niedrigen Geschwindig­ keiten anwächst.8. The method according to any one of claims 1 to 7; characterized in that the critical driving speed (v e ) is displayed by means of a scale ( 2 ) which, with decreasing visibility (s) or decreasing distance (s f ) of the vehicle in front and / or decreasing friction values (µ max ) of high increases at low speeds. 9. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß bei Über­ schreitung der kritischen Fahrgeschwindigkeit (ve) eine Anzeige (2) aktiviert wird.9. The method according to any one of claims 1 to 7, characterized in that when the critical vehicle speed (v e ) is exceeded, a display ( 2 ) is activated.
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DE19842432B4 (en) * 1997-09-18 2004-11-11 Toyota Jidosha K.K., Toyota Method and device for predicting the minimum stopping distance required to brake a moving vehicle
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DE102013000310A1 (en) 2013-01-10 2013-08-08 Daimler Ag Method for determining set speed of longitudinal control system for assisting driver of motor car, involves determining security setting speed in response to environment variable
US10889297B2 (en) 2017-10-13 2021-01-12 International Business Machines Corporation Determining a safe driving speed for a vehicle
DE102018206426A1 (en) * 2018-04-25 2019-10-31 Bayerische Motoren Werke Aktiengesellschaft Speed indicator for a driving system for automated driving and display method

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