EP1483143A1 - Method for determining a maximum coefficient of friction - Google Patents
Method for determining a maximum coefficient of frictionInfo
- Publication number
- EP1483143A1 EP1483143A1 EP03743341A EP03743341A EP1483143A1 EP 1483143 A1 EP1483143 A1 EP 1483143A1 EP 03743341 A EP03743341 A EP 03743341A EP 03743341 A EP03743341 A EP 03743341A EP 1483143 A1 EP1483143 A1 EP 1483143A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- longitudinal
- forces
- slip
- friction
- vehicle
- 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.)
- Withdrawn
Links
- 238000000034 method Methods 0.000 title claims abstract description 24
- 230000001133 acceleration Effects 0.000 claims description 31
- 230000006870 function Effects 0.000 claims description 11
- 230000005484 gravity Effects 0.000 claims description 4
- 238000011156 evaluation Methods 0.000 claims description 2
- 238000013459 approach Methods 0.000 abstract description 2
- 230000004913 activation Effects 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000005070 sampling Methods 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000013178 mathematical model Methods 0.000 description 2
- 238000000418 atomic force spectrum Methods 0.000 description 1
- 238000003339 best practice Methods 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
Classifications
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- 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
- B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
- B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
- B60W40/06—Road conditions
- B60W40/068—Road friction coefficient
-
- 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
- B60T8/1725—Using tyre sensors, e.g. Sidewall Torsion sensors [SWT]
-
- 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
- B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
- B60T2210/10—Detection or estimation of road conditions
- B60T2210/12—Friction
-
- 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
- B60T2240/00—Monitoring, detecting wheel/tire behaviour; counteracting thereof
- B60T2240/03—Tire sensors
-
- 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
- B60W2510/00—Input parameters relating to a particular sub-units
- B60W2510/20—Steering systems
- B60W2510/205—Steering 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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/10—Longitudinal 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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/10—Longitudinal speed
- B60W2520/105—Longitudinal acceleration
-
- 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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/12—Lateral speed
- B60W2520/125—Lateral acceleration
-
- 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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/14—Yaw
-
- 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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/26—Wheel slip
-
- 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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/28—Wheel 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
- B60W2530/00—Input parameters relating to vehicle conditions or values, not covered by groups B60W2510/00 or B60W2520/00
- B60W2530/20—Tyre data
Definitions
- the invention relates to a method for determining a maximum coefficient of friction between the tire and road surface of a vehicle from force information that occurs when the tire and road surface come into contact.
- the invention has for its object to determine the current maximum coefficient of friction regardless of the entry into a control system.
- this object is achieved in that a generic method is carried out in such a way that values which represent the use of traction in the longitudinal and / or transverse direction, on the basis of measured and / or estimated variables, which are the current ones acting on the individual wheels and tires Longitudinal forces, lateral forces and the riot forces are reproduced, including the measured or calculated current state variables, which represent the slip angle and / or the slip angle speed and / or the longitudinal slip and / or the slow slip speed, are permanently determined, and the determined values are compared with threshold values and one Evaluation to determine the maximum Coefficient of friction including other auxiliary variables, such as longitudinal force, lateral force, contact force, longitudinal acceleration, lateral acceleration, vehicle mass and / or substitute variables are supplied if the comparison results fall below the threshold values.
- Other auxiliary variables and / or substitute variables such as yaw rate, yaw acceleration, steering angle speed, wheel rotation speed and acceleration, are included in the method.
- the method for determining the current maximum coefficient of friction is advantageous regardless of the entry into the control.
- a coefficient of friction estimated in this way can advantageously be used for the detection of the driving dynamic limit range.
- the method is characterized by the following steps: determining gradients of the adhesion utilization between the tire and the road in the longitudinal direction as a function of the slip or the slip speed,
- a substitute value ⁇ 0 is used as the coefficient of friction.
- the gradients are determined from the longitudinal and / or lateral forces standardized by the contact forces of at least one wheel or at least one vehicle axis and the slip angle or the slip angle speed or the slip or the slip speed of at least one wheel.
- the gradients are advantageously determined from the longitudinal force normalized with the contact forces of at least one vehicle axle according to the relationship
- the contact forces of an axle result from the sum of the contact forces of the wheels of an axle.
- the model-based determination of the riot forces from driving and vehicle condition variables has the advantage that sensors for the detection of the riot forces can be omitted.
- a microcontroller program product is advantageously provided, which can be loaded directly into the memory of a vehicle dynamics control, such as ESP, ACT, ABS (anti-lock braking system) control and the like, and comprises software code sections with which the steps according to one of claims 1 to 11 are carried out, if the product runs on a microcontroller.
- the microcontroller program product is stored on a microcontroller suitable medium.
- a microcontroller is a highly integrated component that integrates a microprocessor, program memory, data memory, input and output interfaces and peripheral functions (e.g. counters, bus controllers, etc.) on a chip.
- Fig. 1 is a schematic representation of the tire forces in a wheel-fixed coordinate system
- Fig. 5 is a force-utilization riot force curve
- 1 shows the tire forces in the wheel-fixed coordinate systems of a vehicle as an example.
- the forces of the individual wheels which occur on the tires as a result of the tire roadway contact can be longitudinal or circumferential forces, lateral forces and / or wheel contact forces.
- 1 shows longitudinal wheel forces F x and lateral forces Fy in the wheel-fixed coordinate systems of a vehicle. The forces are designated with indices. It applies
- V front axle of the vehicle
- the cutting forces of the individual wheels arising from the tire-road contact are used for the method.
- suitable sensors such as sidewall torsion sensors, force measuring rims, surface sensors, application force / pressure determination from control signals of the brake actuator via a mathematical model or application force / pressure measurement of the brake actuator, (circumferential forces), travel sensors or pressure sensors for air springs or with a wheel load model can be generated from lateral and longitudinal acceleration information (contact forces) or derived indirectly from driving state variables using a mathematical model.
- These forces can be longitudinal wheel forces, lateral forces and / or wheel contact forces.
- longitudinal or lateral accelerations, wheel rotational speeds and accelerations, as well as engine torque and rotational speeds can be used as a substitute for the forces.
- the signal information can be used either directly or as further processed information, eg filtered with different time constants.
- FIG. 2 shows typical courses of the longitudinal force F x of a tire as a function of the longitudinal slip ⁇ (FIG. 2a) and the lateral force F y as a function of the slip angle a (FIG. 2b).
- the method for determining the current maximum coefficient of friction makes use of the fact that the slope of these characteristic curves decreases with increasing utilization of the adhesion, ie with increasing longitudinal slip ⁇ or slip angle a. This also applies to combined loads in the longitudinal and transverse directions, for example braking in a curve. Only the maxima are shifted to higher slip or slip angle values. If one of the slopes C x or C y falls below defined thresholds, it is assumed that the maximum coefficient of friction between the tire and the road has been reached. This consideration can be carried out for each individual wheel of a vehicle or on an axle basis.
- the axially Consideration will preferably be performed in transverse dynamic maneuvers. Differences in the coefficient of friction on the right and left play a subordinate role in transverse dynamic maneuvers.
- the method which is shown in its basic structure in FIGS. 3 and 4, consists of three parts which build on one another:
- Tire characteristics from the measured or calculated tire forces F x , F y , F z of at least one wheel or axially in approximation to F x from the measured or calculated engine torque, the engine speed, the
- the coefficient of friction is used as the coefficient of friction /, i or axially as / 4na ⁇ , vA / HA>
- the existing frictional utilization can either be direct from the tire forces (Kammscher Kreis) or indirectly from substitute variables such as longitudinal and lateral acceleration, engine torque, engine speed, brake pressure and wheel rotation speed and acceleration.
- the coefficient of friction 4 ia x , v AH A is determined axially, a wheel-specific distribution of the coefficient of friction takes place as a function of the measured or calculated wheel contact forces F z , ⁇ .
- the riot forces are either measured or, for example, determined using a model, e.g. with the vehicle mass in, the center of gravity height h and the acting lever arms (see Fig. 1)
- the longitudinal force circumferential slip gradient C x results from the longitudinal slip ⁇ that can be determined from vehicle and wheel speeds
- the gradient can be determined with the slip speed ⁇ .
- the slip speed ⁇ can be determined from further auxiliary signals, such as the wheel rotation speed ⁇ R , the wheel rotation acceleration ⁇ R , the longitudinal vehicle speed v x , the longitudinal vehicle acceleration a x and the wheel radius r.
- the size T A is the sampling time.
- the lateral force slip angle gradient C y can be determined using a measured or estimated slip angle a. If the slip angle is not available, the gradient in the form of dF VM dt ⁇ ,
- the slip angular velocity ⁇ can be determined from further auxiliary signals, cf. Embodiment.
- the size T A is the sampling time.
- a longitudinal force standardized by the axis can be determined from the longitudinal force and the contact force of the axis
- the longitudinal force on the front axle can be approximately calculated from the brake pressure P B , VA as the sum of the brake pressures on the axle
- An axially normalized lateral force can be approximately calculated from the lateral acceleration of the front axle a y , ra or rear axle a y , ra .
- the lateral accelerations can be determined directly from the sensor information or calculated from derived signals, such as from the acceleration of the center of gravity, using the yaw rate and yaw acceleration.
- the criterion for determining the coefficient of friction is fulfilled if one or more slip stiffness values fall below defined threshold values S xr S y , ie
- the adhesion utilization ⁇ can be customized for each wheel
- the maximum coefficient of friction is estimated individually for the wheel with the aid of the lateral force slip angle gradient.
- the slip angle speed is determined axially
- the lateral force slip angle gradient on each wheel is a function of the threshold value S a in the range 0.5-5 degrees / s, preferably 1 degree / s with C y0, preferably 0.3 1 / degree
- the lateral force slip angle gradient C y is compared with the threshold value S y .
- S y is in the range 0.02 to 0.06 1 / degree, the maximum adhesion utilization is
- the coefficient of friction ⁇ k is the current utilization of the adhesion at the sampling time k according to Eq. (2.13) when viewed by wheels and Eq. (2.15) or (2.17) when viewed axially.
- the coefficient of friction ⁇ k - ⁇ is the adhesion utilization in the previous sampling time.
- the coefficient of friction ⁇ ma ⁇ , vA / HA is distributed along the characteristic force-dependent characteristic curve in FIG. 5 to the wheels of the corresponding axle.
- This distribution takes into account the fact that when cornering, the force utilization and thus also the maximum coefficient of friction on the relieved inner wheel is always higher than on the loaded outer wheel Distribution curve is non-linear, e.g. exponential.
- An axially determined maximum coefficient of friction of 1.0, for example, must be taken into account with a value of 1.8 on the inside of the curve and 0.9 on the outside of the curve, depending on the wheel load / load.
Landscapes
- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Mathematical Physics (AREA)
- Control Of Driving Devices And Active Controlling Of Vehicle (AREA)
- Regulating Braking Force (AREA)
Abstract
Currently available systems for regulating driving dynamics, such as for example ESP or TCS, require in the driving dynamical limit range information about the actual maximum coefficient of friction ( mu -max) between tires and roadway to function reliably. A proven approach is to use, once the regulation is active, the actual utilization of grip as the maximum coefficient of friction. The invention relates to a method for determining the actual maximum coefficient of friction ( mu -max) independently from the activation of the regulation. According to the inventive method, values (C_x, C_y) are permanently determined that represent the utilization of grip in the longitudinal and/or transverse direction, based on measured and/or estimated variables that represent the actual longitudinal forces (F_x), lateral forces (F_y) and vertical forces (F_z) acting upon the individual wheels and tires, while using the measured or calculated actual state variables that represent the slip angle ( alpha ) and/or the slip angle velocity ( alpha ) and/or the longitudinal slip ( gamma ) and/or the longitudinal slip velocity ( gamma ). The determined values (C_x, C_y) are compared with threshold values (S_x, S_y) and are evaluated to determine the maximum coefficient of friction ( mu -max) while using additional auxiliary variables if the resulting values of comparison are smaller than the threshold values.
Description
Verfahren zum Ermitteln eines maximalen ReibwertesMethod for determining a maximum coefficient of friction
Die Erfindung betrifft ein Verfahren zum Ermitteln eines maximalen Reibwertes zwischen Reifen und Fahrbahn eines Fahrzeugs aus Kraftinformationen, die bei dem Kontakt zwischen Reifen und Fahrbahn auftreten.The invention relates to a method for determining a maximum coefficient of friction between the tire and road surface of a vehicle from force information that occurs when the tire and road surface come into contact.
Einleitung und Stand der TechnikIntroduction and state of the art
Heutige Fahrdynamikregelsysteme, wie z.B. ESP (Elektronisches Stabilitäts Programm) oder TCS (Traction Control System) benötigen im fahrdynamischen Grenzbereich für eine sichere Funktion eine Information über den aktuellen maximalen Reibwert zwischen Reifen und Fahrbahn. Ein bewährtes Vorgehen ist, nach Eintritt in die Regelung, die aktuelle Kraftschlussausnutzung als den maximalen Reibwert zu verwenden (WO 96/16851) .Today's vehicle dynamics control systems, such as ESP (Electronic Stability Program) or TCS (Traction Control System) require information about the current maximum coefficient of friction between the tire and the road in the dynamic range of the vehicle in order to function safely. A best practice is to use the current frictional engagement as the maximum coefficient of friction after entering the control (WO 96/16851).
Der Erfindung liegt die Aufgabe zugrunde, den aktuellen maximalen Reibwert unabhängig vom Eintritt in eine Regelung zu ermitteln.The invention has for its object to determine the current maximum coefficient of friction regardless of the entry into a control system.
Erfindungsgemäss wird diese Aufgabe dadurch gelöst, dass ein gattungsgemässes Verfahren so durchgeführt wird, dass Werte, die die Kraftschlussausnutzung in Längs- und/oder Querrichtung darstellen, auf Basis von gemessenen und/oder geschätzten Grossen, die die auf die einzelnen Räder und Reifen wirkenden aktuellen Längskräfte, Seitenkräfte sowie die Aufstandskrafte wiedergeben, unter Einbeziehung von gemessenen oder berechneten aktuellen Zustandsgrößen, die den Schräglaufwinkel und/oder die Schräglaufwinkelgeschwindigkeit und/oder den Längsschlupf und/oder die Langsschlupfgeschwindigkeit wiedergeben, permanent ermittelt werden, und die ermittelten Werte mit Schwellwerten verglichen und einer Auswertung zur Bestimmung des maximalen
Reibwertes unter Einbeziehung von weiteren Hilfsgrößen, wie Längskraft, Seitenkraft, Aufstandskraft, Längsbeschleunigung, Querbeschleunigung, Fahrzeugmasse und/oder Ersatzgrößen zugeführt werden, wenn die Vergleichsergebnisse die Schwellwerte unterschreiten. Einbezogen in das Verfahren sind weitere Hilfsgrössen und/oder Ersatzgrössen, wie Gierrate, Gierbeschleunigung, Lenkwinkelgeschwindigkeit, Raddrehgeschwindigkeit und -beschleunigung,According to the invention, this object is achieved in that a generic method is carried out in such a way that values which represent the use of traction in the longitudinal and / or transverse direction, on the basis of measured and / or estimated variables, which are the current ones acting on the individual wheels and tires Longitudinal forces, lateral forces and the riot forces are reproduced, including the measured or calculated current state variables, which represent the slip angle and / or the slip angle speed and / or the longitudinal slip and / or the slow slip speed, are permanently determined, and the determined values are compared with threshold values and one Evaluation to determine the maximum Coefficient of friction including other auxiliary variables, such as longitudinal force, lateral force, contact force, longitudinal acceleration, lateral acceleration, vehicle mass and / or substitute variables are supplied if the comparison results fall below the threshold values. Other auxiliary variables and / or substitute variables, such as yaw rate, yaw acceleration, steering angle speed, wheel rotation speed and acceleration, are included in the method.
Längsgeschwindigkeit, Längsbeschleunigung, Querbeschleunigung, ggf. Motordrehzahl, Motormoment, Motorträgheitsmoment, Wirkungsgrad, Radträgheitsmoment, Radradius, und Bremsdruck, die zur Ermittlung der Kräfte, der Schlupfänderung und/oder SchräglaufWinkeländerung herangezogen werden.Longitudinal speed, longitudinal acceleration, lateral acceleration, if necessary engine speed, engine torque, engine moment of inertia, efficiency, wheel moment of inertia, wheel radius, and brake pressure, which are used to determine the forces, the slip change and / or slip angle change.
Vorteilhaft ist das Verfahren zur Bestimmung des aktuellen maximalen Reibwertes unabhängig vom Eintritt in die Regelung. Ein derart geschätzter Reibwert kann vorteilhaft zur Detektion des fahrdynamischen Grenzbereichs verwendet werden. Hiermit sind erweiterte ESP-Funktionalitäten, wie z.B. eine Schwimmwinkelregelung, oder TCS-Funktionalitäten möglich.The method for determining the current maximum coefficient of friction is advantageous regardless of the entry into the control. A coefficient of friction estimated in this way can advantageously be used for the detection of the driving dynamic limit range. This includes extended ESP functionalities, such as Float angle control or TCS functionalities possible.
Dabei ist das Verfahren gekennzeichnet durch die Schritte: Ermitteln von Gradienten der Kraftschlussausnutzung zwischen Reifen und Fahrbahn in Längsrichtung als Funktion des Schlupfes oder der Schlupfgeschwindigkeit,The method is characterized by the following steps: determining gradients of the adhesion utilization between the tire and the road in the longitudinal direction as a function of the slip or the slip speed,
Ermitteln von Gradienten der Kraftschlussausnutzung zwischen Reifen und Fahrbahn in Querrichtung als Funktion des Schräglauf inkeis oder der SchräglaufWinkelgeschwindigkeit, Vergleichen der Gradienten mit Schwellwerten und Ermitteln des maximalen Reibwertes aus den Längs-, Seiten-, Aufstandskräften oder den Längskräften, den Aufstandskräften, der Querbeschleunigung, der Längsbeschleunigung, der Fahrzeugmasse und/oder Ersatzgrössen, wenn das
Vergleichsergebniss die Schwellwerte unterschreitet.Determination of gradients of the frictional engagement between the tire and the roadway in the transverse direction as a function of the slip angle or the slip angle speed, comparing the gradients with threshold values and determining the maximum coefficient of friction from the longitudinal, lateral, contact forces or the longitudinal forces, the contact forces, the lateral acceleration, the Longitudinal acceleration, vehicle mass and / or substitute sizes, if that Result of comparison falls below the threshold values.
Wenn ein Vergleichsergebnis ermittelt wird, bei dem der ermittelte Wert den Schwellwert nicht unterschreitet, wird ein Ersatzwert μ0 als Reibwert verwendet wird. Der Ersatzwert ist bevorzugt μ0 = 1.If a comparison result is determined in which the determined value does not fall below the threshold value, a substitute value μ 0 is used as the coefficient of friction. The substitute value is preferably μ 0 = 1.
Um Gradientenschwankungen durch variierende Aufstandskrafte Fz auszuschließen, erfolgt die Ermittlung der Gradienten aus den mit den Aufstandskräften normierten Längs- und/oder Seitenkräften mindestens eines Rades oder mindestens einer Fahrzeugachse und dem Schräglaufwinkel oder der Schräglaufwinkelgeschwindigkeit oder dem Schlupf oder der Schlupfgeschwindigkeit mindestens eines Rades. Dabei erfolgt vorteilhaft die Ermittlung der Gradienten aus der mit den Aufstandskräften normierten Längskraft mindestens einer Fahrzeugachse nach der BeziehungIn order to rule out gradient fluctuations due to varying contact forces F z , the gradients are determined from the longitudinal and / or lateral forces standardized by the contact forces of at least one wheel or at least one vehicle axis and the slip angle or the slip angle speed or the slip or the slip speed of at least one wheel. The gradients are advantageously determined from the longitudinal force normalized with the contact forces of at least one vehicle axle according to the relationship
Gl . ( 2 . 6) p ^x,VAIHA -t<x,n,VAtHA ~ p wobei dEq. (2. 6) p ^ x, VAIHA - t < x, n, VAtHA ~ p where d
Vorderachse des Fahrzeugs nachFront axle of the vehicle after
Gl . ( 2 . 7 ) FxyA = -(- KByApByA - 2JRώR VA) und/oder die rEq. (2. 7) F xyA = - (- K ByA p ByA - 2J R ώ R VA ) and / or the r
Längskräfte der Hinterachse des Fahrzeugs nachLongitudinal forces of the rear axle of the vehicle
Gl. (2.8) ,HA = -{MMigη -KB^pB,m - {2JR + JMig 2)ώR A) r bestimmt werden. Die Ermittlung der Gradienten aus der mit den Aufstandskräften normierten Seitenkraft mindestens einer Fahrzeugachse erfolgt nach der Beziehung
Gl . (2 . 11 ) ay,VAIHA y,VA/HA g άEq. (2.8) , HA = - {M M i g η -K B ^ p B, m - {2J R + J M i g 2 ) ώ RA ) r. The determination of the gradients from the lateral force standardized by the contact forces of at least one vehicle axle is carried out according to the relationship Eq. (2.11) a y, VAIHA y, VA / HA g ά
Vorteilhaft werden die Längskraft-Umfangschlupf-Gradienten für mindestens ein Rad nach der BeziehungThe longitudinal force-circumferential slip gradients are advantageous for at least one wheel according to the relationship
und/oder die Seitenkraft-Schräglaufwinkel-Gradienten für mindestens ein Rad nach der Beziehung and / or the lateral force slip angle gradients for at least one wheel according to the relationship
ermittelt, determined,
Zweckmässig ist, dass die Aufstandskrafte modellbasiert nach der BeziehungIt is appropriate that the riot forces based on the relationship
bestimmt werden. Die Aufstandskrafte einer Achse ergeben sich aus der Summe der Aufstandskrafte der Räder einer Achse. Die modellbasierte Ermittlung der Aufstandskrafte aus Fahr- und Fahrzeugzustandsgrößen hat den Vorteil, dass Sensoren für die Erfassung der Aufstandskrafte entfallen können.be determined. The contact forces of an axle result from the sum of the contact forces of the wheels of an axle. The model-based determination of the riot forces from driving and vehicle condition variables has the advantage that sensors for the detection of the riot forces can be omitted.
Weiterhin ist es vorteilhaft, .dass die maximale Kraftschlussausnutzung radindividuell nach der Beziehung
Furthermore, it is advantageous that the maximum use of traction is wheel-specific according to the relationship
ermittelt wird und die maximale Kraftschlussausnutzung für die Hinterachse des Fahrzeugs nach der Beziehungis determined and the maximum adhesion utilization for the rear axle of the vehicle according to the relationship
Gl . (2 . 15) HA
oder für die Vorderachse des Fahrzeugs nach der BeziehungEq. (2.15) HA or for the front axle of the vehicle according to the relationship
Gl . ( 2 . 17 ) μVA
ermittelt wird.Eq. (2. 17,) μ VA is determined.
Vorteilhaft ist ein Mikrocontrollerprogrammprodukt vorgesehen, das direkt in den Speicher einer Fahrdynamikregelung, wie ESP, ACT, ABS (Antiblockiersyste ) -Regelung und dgl., geladen werden kann und Softwarecodeabschnitte umfasst, mit denen die Schritte gemäss einem der Ansprüche 1 bis 11 ausgeführt werden, wenn das Produkt auf einem Mirkrocontroller läuft. Das Mikrocontrollerprogrammprodukt ist auf einem mikrocontrollergeeigneten Medium gespeichert. Unter Mikrocontroller versteht man einen hochintegrierten Baustein, der auf einem Chip Mikroprozessor, Programmspeicher, Datenspeicher, Ein- und Ausgabeschnittstellen und Peripheriefunktionen (z.B. Counter, Bus-Controller, etc.) integriert.A microcontroller program product is advantageously provided, which can be loaded directly into the memory of a vehicle dynamics control, such as ESP, ACT, ABS (anti-lock braking system) control and the like, and comprises software code sections with which the steps according to one of claims 1 to 11 are carried out, if the product runs on a microcontroller. The microcontroller program product is stored on a microcontroller suitable medium. A microcontroller is a highly integrated component that integrates a microprocessor, program memory, data memory, input and output interfaces and peripheral functions (e.g. counters, bus controllers, etc.) on a chip.
Vorteilhafte Weiterbildungen der Erfindung sind in den Unteransprüchen angegeben.Advantageous developments of the invention are specified in the subclaims.
Ein Aus ührungsbeispiel ist in der Zeichnung dargestellt und wird im Folgenden näher beschrieben.
Es zeigenAn exemplary embodiment is shown in the drawing and is described in more detail below. Show it
Fig. 1 eine schematische Darstellung der Reifenkräfte in einem radfesten KoordinatensystemFig. 1 is a schematic representation of the tire forces in a wheel-fixed coordinate system
Fig. 2 a)eine Kraftschlussausnutzungs-Schlupf-Kurve b) eine Krafschlussausnutzungs-Schräglaufwinkel-Kurve2 a) a frictional utilization-slip curve b) a frictional utilization-slip angle curve
Fig. 3 eine schematische Regelstruktur mit radweise ermittelten Gradienten3 shows a schematic control structure with gradients determined by wheels
Fig. 4 eine schematische Regelstruktur mit achsweise ermittelten Gradienten4 shows a schematic control structure with axially determined gradients
Fig. 5 eine Kraftschlussausnutzungs- Aufstandskraft -KurveFig. 5 is a force-utilization riot force curve
In Fig. 1 sind die Reifenkräfte in den radfesten Koordinatensystemen eines Fahrzeugs beispielhaft dargestellt. Die durch den Reifen-Fahrbah -Kontakt an den Reifen auftretenden Kräfte der einzelnen Räder können Radlängs- bzw. umfangskräfte, Querkräfte und/oder RadaufStandskräfte sein. In Fig. 1 sind beispielhaft Radlängskräfte Fx und Querkräfte Fy in den radfesten Koordinatensystemen eines Fahrzeugs dargestellt. Die Kräfte werden mit Indices bezeichnet . Es gilt1 shows the tire forces in the wheel-fixed coordinate systems of a vehicle as an example. The forces of the individual wheels which occur on the tires as a result of the tire roadway contact can be longitudinal or circumferential forces, lateral forces and / or wheel contact forces. 1 shows longitudinal wheel forces F x and lateral forces Fy in the wheel-fixed coordinate systems of a vehicle. The forces are designated with indices. It applies
H = Hinterachse des FahrzeugsH = rear axle of the vehicle
V = Vorderachse des FahrzeugsV = front axle of the vehicle
R = rechtsR = right
L = linksL = left
1 = Abstand der Achse vom Schwerpunkt b = halbe Spurweite des Rades .1 = distance of the axis from the center of gravity b = half track width of the wheel.
2. Beschreibung des Verfahrens2. Description of the procedure
Für das Verfahren werden die durch den Reifen-Fahrbahn-Kontakt auftretenden Schnittkräfte der einzelnen Räder verwendet. Diese
können z.B. durch geeignete Sensorik, wie z.B. Seitenwandtorsionssensoren, Kraftmessfelgen, Oberflächensensoren, Zuspannkraft-/druck- Bestimmung aus Ansteuersignalen des Bremsenaktuators über ein mathematisches Modell oder Zuspannkraft-/druck- Messung des Bremsenaktuators, (Umfangskräfte) , Federwegsensoren bzw. Drucksensoren bei Luftfedern oder mit einem Radlastmodell aus Quer- und Längsbeschleunigungsinformation (Aufstandskrafte) erzeugt werden oder indirekt aus Fahrzustandsgrößen über ein mathematisches Modell abgeleitet werden. Diese Kräfte können Radlängskräfte, Querkräfte und/oder RadaufStandskräfte sein. Näherungsweise können als Ersatz zu den Kräften gemessene oder geschätzte Längs- , Querbeschleunigungen, Raddrehgeschwindigkeiten und -beschleunigungen sowie Motormoment und -drehzahl verwendet werden. Die Signalinformation kann entweder direkt oder als weiterverarbeitete Information, z.B. mit unterschiedlichen Zeitkonstanten gefiltert, genutzt werden.The cutting forces of the individual wheels arising from the tire-road contact are used for the method. This can, for example, by means of suitable sensors, such as sidewall torsion sensors, force measuring rims, surface sensors, application force / pressure determination from control signals of the brake actuator via a mathematical model or application force / pressure measurement of the brake actuator, (circumferential forces), travel sensors or pressure sensors for air springs or with a wheel load model can be generated from lateral and longitudinal acceleration information (contact forces) or derived indirectly from driving state variables using a mathematical model. These forces can be longitudinal wheel forces, lateral forces and / or wheel contact forces. Approximately, longitudinal or lateral accelerations, wheel rotational speeds and accelerations, as well as engine torque and rotational speeds, can be used as a substitute for the forces. The signal information can be used either directly or as further processed information, eg filtered with different time constants.
In Fig. 2 sind typische Verläufe der Längskraft Fx eines Reifens in Abhängigkeit des Längsschlupfes λ (Fig 2a) und der Querkraft Fy in Abhängigkeit des Schräglaufwinkels a (Fig 2b) dargestellt. Das Verfahren zur Bestimmung des aktuellen maximalen Reibwertes nutzt die Tatsache, dass die Steigung dieser Kennlinien bei zunehmender Kraftschlussausnutzung, d.h. bei zunehmendem Längsschlupf λ bzw. Schräglaufwinkel a , sinkt. Dies gilt ebenso für kombinierte Beanspruchungen in Längs- und Querrichtung, z.B. Bremsen in der Kurve. Lediglich die Maxima sind zu höheren Schlupf- bzw. Schräglaufwinkelwerten verschoben. Unterschreitet eine der Steigungen Cx oder Cy definierte Schwellen, so wird davon ausgegangen, dass der maximale Reibwert zwischen Reifen und Fahrbahn erreicht ist. Diese Betrachtung kann für jedes einzelne Rad eines Fahrzeuges oder auch achsweise durchgeführt werden. Die achsweise
Betrachtung wird man bevorzugt in querdynamischen Manövern durchführen. Reibwertunterschiede rechts und links spielen in querdynamischen Manövern eine eher untergeordnete Rolle.2 shows typical courses of the longitudinal force F x of a tire as a function of the longitudinal slip λ (FIG. 2a) and the lateral force F y as a function of the slip angle a (FIG. 2b). The method for determining the current maximum coefficient of friction makes use of the fact that the slope of these characteristic curves decreases with increasing utilization of the adhesion, ie with increasing longitudinal slip λ or slip angle a. This also applies to combined loads in the longitudinal and transverse directions, for example braking in a curve. Only the maxima are shifted to higher slip or slip angle values. If one of the slopes C x or C y falls below defined thresholds, it is assumed that the maximum coefficient of friction between the tire and the road has been reached. This consideration can be carried out for each individual wheel of a vehicle or on an axle basis. The axially Consideration will preferably be performed in transverse dynamic maneuvers. Differences in the coefficient of friction on the right and left play a subordinate role in transverse dynamic maneuvers.
Das Verfahren, das in seiner Grundstruktur in den Fig. 3 und 4 dargestellt ist, besteht aus drei aufeinander aufbauenden Teilen:The method, which is shown in its basic structure in FIGS. 3 and 4, consists of three parts which build on one another:
Berechnung der Gradienten Cx und Cy (Steigung derCalculate the gradients C x and C y (slope of the
Reifenkennlinien) aus den gemessenen oder berechneten Reifenkräften Fx, Fy, Fz mindestens eines Rades oder achsweise in Näherung zu Fx aus dem gemessenen oder berechneten Motormoment, der Motordrehzahl, demTire characteristics) from the measured or calculated tire forces F x , F y , F z of at least one wheel or axially in approximation to F x from the measured or calculated engine torque, the engine speed, the
Bremsdruck und der Raddrehgeschwindigkeit und -beschleunigung und in Näherung zu Fy aus der gemessenen oder berechnetenBrake pressure and the wheel rotation speed and acceleration and in approximation to F y from the measured or calculated
Querbeschleunigung ay mindestens einer Fahrzeugachse, dem gemessenen oder berechneten Schräglaufwinkel a oder alternativ der Schräglaufwinkelgeschwindigkeit άLateral acceleration a y of at least one vehicle axis, the measured or calculated slip angle a or alternatively the slip angle speed ά
(SchräglaufWinkeländerung) > dem gemessenen oder berechneten(Slip angle change)> the measured or calculated
Längsschlupf λ oder alternativ der Schlupfgeschwindigkeit λ (Schlupfänderung) mindestens eines Rades , sowie weiterer Hilfsgrößen z.B. Gierrate ψ , Gierbeschleunigung ψ , Lenkwinkel δ , Lenkwinkelgeschwindigkeit δ , Raddrehgeschwindigkeit ωR , Raddrehbeschleunigung ώR , der Längsgeschwindigkeit vx, der Längsbeschleunigung ax sowie dem Radradius r.Longitudinal slip λ or alternatively the slip speed λ (slip change) of at least one wheel, as well as other auxiliary variables such as yaw rate ψ, yaw acceleration ψ, steering angle δ, steering angle speed δ, wheel rotation speed ω R , wheel rotation acceleration ώ R , the longitudinal speed v x , the longitudinal acceleration a x and the wheel radius r.
Kriterien zur Bestimmung des Reibungskoeffizienten 4ιax zwischen Reifen und Fahrbahn.Criteria for determining the coefficient of friction 4ax between tire and road surface.
Durch Vergleich der berechneten Gradienten Cx oder Cy mit definierten Schwellen wird entschieden ob das Maximum der
Kraftschlussausnutzung vorliegt und welcher Reibwert als Reibungskoeffizient
verwendet wird.By comparing the calculated gradients C x or C y with defined thresholds, it is decided whether the maximum of the Use of the frictional connection exists and what coefficient of friction is used as the coefficient of friction is used.
Berechnung des Reibungskoeffizienten / ax Calculation of the coefficient of friction / a x
Sind die Kriterien nicht erfüllt, so erfolgt eine Standartvorgabe für den Reibungskoeffizient = to - Sind die Kriterien erfüllt, so wird die momentan vorhandene Kraftschlussausnutzung pro Rad als Reibungskoeffizienten / ,i oder achsweise als /4naχ,vA/HA> Die vorhandene Kraftschlussausnutzung kann entweder direkt aus den Reifenkräften (Kammscher Kreis) oder indirekt aus Ersatzgrößen, wie Längs- und Querbeschleunigung, Motormoment, Motordrehzahl, Bremsdruck und Raddrehgeschwindigkeit und -beschleunigung ermittelt werden. Bei einer achsweisen Bestimmung des Reibungskoeffizienten 4ιax,vAHA erfolgt zusätzlich eine radindividuelle Reibwertverteilung in Abhängigkeit der gemessenen oder berechneten RadaufStandskräfte Fz,ι.If the criteria are not met, there is a standard specification for the coefficient of friction = to - If the criteria are met, the currently available frictional utilization per wheel is used as the coefficient of friction /, i or axially as / 4naχ, vA / HA> The existing frictional utilization can either be direct from the tire forces (Kammscher Kreis) or indirectly from substitute variables such as longitudinal and lateral acceleration, engine torque, engine speed, brake pressure and wheel rotation speed and acceleration. When the coefficient of friction 4 ia x , v AH A is determined axially, a wheel-specific distribution of the coefficient of friction takes place as a function of the measured or calculated wheel contact forces F z , ι.
2.1 Bestimmung der Gradienten Cx und Cy 2.1 Determination of the gradients C x and C y
2.1.1 Radweise Bestimmung der Gradienten aus den Reif nkräf en2.1.1 Determining the gradients from the tire forces wheel by wheel
Um Gradientenschwankungen durch variierende Aufstandskrafte Fz auszuschließen, werden die Längs- und Seitenkräfte mit der Aufstandskraft normiert, d.h.In order to rule out gradient fluctuations due to varying contact forces F z , the longitudinal and lateral forces are standardized with the contact force, ie
Gl. (2.1) F = — F = y *■" p ' y'n F ' Eq. (2.1) F = - F = y * ■ "p ' y ' n F '
Die Aufstandskrafte werden entweder gemessen oder z.B. modellgestützt bestimmt, z.B. mit der Fahrzeugmasse in, der Schwerpunkthöhe h sowie den wirkenden Hebelarmen (vgl. Fig. 1)
The riot forces are either measured or, for example, determined using a model, e.g. with the vehicle mass in, the center of gravity height h and the acting lever arms (see Fig. 1)
Der Längskraft-Umfangsschlupf-Gradienten Cx ergibt sich mit dem aus Fahrzeug- und Radgeschwindigkeiten ermittelbaren Längsschlupf λ zuThe longitudinal force circumferential slip gradient C x results from the longitudinal slip λ that can be determined from vehicle and wheel speeds
dFXΛ dF XΛ
Gl. (2.3) C = x,n dFXM dt ΔF x.n 11 dλ dt dλEq. (2.3) C = x, n dF XM dt ΔF xn 1 1 dλ dt dλ
Steht der Schlupf nicht zur Verfügung, so kann mit der Schlupfgeschwindigkeit λ der Gradient bestimmt werden. Die Schlupfgeschwindigkeit λ kann aus weiteren Hilfssignalen, wie der Raddrehgeschwindigkeit ωR , der Raddrehbeschleunigung ώR , der Fahrzeuglängsgeschwindigkeit vx , der Fahrzeuglängsbeschleunigung ax sowie dem Radradius r ermittelt werden. Die Größe TA ist die Abtastzeit.If the slip is not available, the gradient can be determined with the slip speed λ. The slip speed λ can be determined from further auxiliary signals, such as the wheel rotation speed ω R , the wheel rotation acceleration ώ R , the longitudinal vehicle speed v x , the longitudinal vehicle acceleration a x and the wheel radius r. The size T A is the sampling time.
Gl. (2.4) = ώRr ωRr ' aχ Eq. (2.4) = ώ R r ω R r 'aχ
Der Seitenkraft-Schräglaufwinkel-Gradient Cy kann mit einem gemessenen oder geschätzten Schräglaufwinkel a bestimmt werden. Steht der Schräglaufwinkel nicht zur Verfügung, so kann mit der Schräglaufwinkelgeschwindigkeit ά der Gradient in Form von
dFVM dt Δ ,The lateral force slip angle gradient C y can be determined using a measured or estimated slip angle a. If the slip angle is not available, the gradient in the form of dF VM dt Δ,
Gl. (2.5) c„=-a- y,n y,„» 1 da dt da Tä aEq. (2.5) c "= - a - y, ny," »1 da dt da T ä a
bestimmt werden. Die SchräglaufWinkelgeschwindigkeit ά kann aus weiteren Hilfssignalen ermittelt werden, vgl. Ausführungsbeispiel. Die Größe TA ist die Abtastzeit.be determined. The slip angular velocity ά can be determined from further auxiliary signals, cf. Embodiment. The size T A is the sampling time.
2.1.2 Achsweise Bestimmung der Gradienten2.1.2 Determining the gradients by axis
Eine achsweise normierte Längskraft kann aus der Längskraft und der Aufstandskraft der Achse nachA longitudinal force standardized by the axis can be determined from the longitudinal force and the contact force of the axis
berechnet werden. Bei einem Standardantrieb kann die Längskraft an der Vorderachse näherungsweise aus dem Bremsdruck PB,VA als Summe der Bremsdrücke an der Achse, einembe calculated. In a standard drive, the longitudinal force on the front axle can be approximately calculated from the brake pressure P B , VA as the sum of the brake pressures on the axle
Proportionalitätsfaktor KB,VA I dem Radträgheitsmoment JR/ dem Radradius r und der Raddrehbeschleunigung ώRyA (Mittelwert der Raddrehbeschleunigungen der Achse) < berechnet werden zuProportionality factor K B , VA I, the wheel moment of inertia J R / the wheel radius r and the wheel spin ώ RyA (mean value of the wheel spin of the axle) <are calculated
Gl- (2-7) FxyA = -{- KByApByA - 2JRώR A )Gl- (2-7) F xyA = - {- K ByA p ByA - 2J R ώ RA )
Die Längskraft an der Hinterachse kann näherungsweise aus dem Bremsdruck PB,HA als Summe der Bremsdrücke an der Achse, einem Proportionalitätsfaktor KB,HA , dem Radträgheitsmoment JR, dem
Radradius r und der Raddrehbeschleunigung ώR HA (Mittelwert der Raddrehbeschleunigungen der Achse) > dem Motormoment MM, dem Motorträgheitsmoment JM, dem Übersetzungsverhältnis als Verhältnis von Motordrehzahl zu Raddrehzahl ig = ωM l 'G)R>HA und dem Wirkungsgrad η berechnet werden zuThe longitudinal force on the rear axle can be approximated from the brake pressure P B , HA as the sum of the brake pressures on the axle, a proportionality factor K B , HA , the wheel moment of inertia J R , the Radius r and the wheel spin ώ R HA (mean value of the wheel spin of the axle)> the engine torque M M , the engine moment of inertia J M , the gear ratio as a ratio of engine speed to wheel speed i g = ω M l 'G) R> HA and the efficiency η to be calculated
Gl. (2.8) Fx = )bRM )
Eq. (2.8) F x =) b RM )
Die Längssteifigkeit pro Achse ergibt sich ausThe longitudinal stiffness per axis results from
Eine achsweise normierte Seitenkraft kann näherungsweise aus der Querbeschleunigung der Vorderachse ay,ra oder Hinterachse ay,ra berechnet werden.An axially normalized lateral force can be approximately calculated from the lateral acceleration of the front axle a y , ra or rear axle a y , ra .
π - y-M + y' hr ~ _ mHAa y,HA _ ay,m Fz,h, + Fz FZ<HA mmg g π - y- M + y ' hr ~ _ m HA a y , HA _ a y, m F z, h , + F z F Z <HA m m gg
Die Querbeschleunigungen lassen sich direkt aus den Sensorinformationen ermitteln oder aus abgeleiteten Signalen, wie z.B. aus der Schwerpunktsbeschleunigung mit Hilfe der Gierrate und Gierbeschleunigung berechnen. Die Schräglaufsteifigkeit pro Achse ergibt sich mit der zeitlichen Ableitung der Querbeschleunigung zu
Gl.(2.11) CyyA/HA =-^ g etThe lateral accelerations can be determined directly from the sensor information or calculated from derived signals, such as from the acceleration of the center of gravity, using the yaw rate and yaw acceleration. The slip rigidity per axis results from the time derivative of the lateral acceleration Eq. (2.11) CyyA / HA = - ^ g et
2.2 Kriterien zur Bestimmung des Reibungskoeffizienten ^ιax 2.2 Criteria for determining the coefficient of friction ^ ιax
Das Kriterium zur Bestimmung der Reibungskoeffizienten ist erfüllt, wenn eine oder mehrere Schräglaufsteifigkeiten festgelegte Schwellwerte Sxr Sy unterschreiten, d.h.The criterion for determining the coefficient of friction is fulfilled if one or more slip stiffness values fall below defined threshold values S xr S y , ie
Gl.(2.12) C„ < S,, i χ≡ { l..A,VA,HA } Eq. (2.12) C „<S ,, i χ≡ {l..A, VA, HA}
2.3 Berechnung des Reibungskoeffizienten max2.3 Calculation of the friction coefficient max
Sind die Kriterien nach Gl . (2.17) nicht erfüllt, so erfolgt eine Standardvorgabe für den Reibungskoeffizient 4,ax = μ0. Anderenfalls kann der maximale Reibungskoeffizient aus der Kraftschlussausnutzung sowie weiteren Hilfsgrößen wie im folgenden beschrieben bestimmt werden.If the criteria according to Eq. (2.17) is not met, there is a standard specification for the coefficient of friction 4, ax = μ 0 . Otherwise, the maximum coefficient of friction can be determined from the adhesion utilization and other auxiliary variables as described below.
Bestimmung der KraftschlussausnutzungDetermination of the adhesion utilization
Die Kraftschlussausnutzung μ kann radindividuell mitThe adhesion utilization μ can be customized for each wheel
^FX 2 + F;^ F X 2 + F;
Gl. (2.13) μ =Eq. (2.13) μ =
oder achsweise mit der Fahrzeugmasse m aus dem dem Ansatzor axially with the vehicle mass m from the approach
Gl- ( -14) μVAFzyA + μHAF2m
bestimmt werden zuGl- (-14) µ VA F zyA + µ HA F 2m to be determined
Für den Spezialfall, dass FXf VA klein ist, giltFor the special case that F Xf VA is small, applies
Für die Vorderachse gilt entsprechendThe same applies to the front axle
m^a] + a y,HAm ^ a] + a y, HA
Gl. (2.17) z,HA VA ~ ~ HA -Y-> ∞Ü HA = 4 x,HA +F z,VA F z.,VA ■ z,HAEq. (2.17) z, HA VA ~ ~ HA -Y-> ∞ Ü HA = 4 x, HA + F z, VA F z., VA ■ z, HA
Für den Spezialfall, dass FX/HA klein ist, giltFor the special case that F X / HA is small, applies
3 Ausführungsbeispiel3 embodiment
Im Ausführungsbeispiel wird radindividuell der maximale Reibwert mit Hilfe des Seitenkraft-Schräglaufwinkel-Gradienten geschätzt. Die Schräglaufwinkelgeschwindigkeit wird achsweise bestimmt zuIn the exemplary embodiment, the maximum coefficient of friction is estimated individually for the wheel with the aid of the lateral force slip angle gradient. The slip angle speed is determined axially
Der Seitenkraft-Schräglaufwinkel-Gradient an jedem Rad ergibt sich in Abhängigkeit des Schwellwertes Sa im Bereich 0.5 - 5 Grad/s, vorzugsweise 1 Grad/s mit Cy0 vorzugsweise 0.3 1/Grad zu The lateral force slip angle gradient on each wheel is a function of the threshold value S a in the range 0.5-5 degrees / s, preferably 1 degree / s with C y0, preferably 0.3 1 / degree
Der Seitenkraft-Schräglaufwinkel-Gradient Cy wird mit dem Schwellwert Sy verglichen. Bei Cy < Sy , wobei Sy im Bereich 0,02 bis 0,06 1/Grad liegt, wird die maximale KraftschlussausnutzungThe lateral force slip angle gradient C y is compared with the threshold value S y . At C y <S y , where S y is in the range 0.02 to 0.06 1 / degree, the maximum adhesion utilization is
radindividuell nach der Beziehung μ
ermittelt. zindividual wheel according to the relationship μ determined. z
Der maximale Reibwert wird bestimmt zuThe maximum coefficient of friction is determined too
Der Reibwert μk ist die aktuelle Kraftschlussausnutzung zum AbtastZeitpunkt k nach Gl. (2.13) bei radweiser Betrachtung und Gl. (2.15) bzw. (2.17) bei achsweiser Betrachtung. Der Reibwert μk-ι ist die Kraftschlussausnutzung im vorherigen Abtastzeitpunkt .The coefficient of friction μ k is the current utilization of the adhesion at the sampling time k according to Eq. (2.13) when viewed by wheels and Eq. (2.15) or (2.17) when viewed axially. The coefficient of friction μ k -ι is the adhesion utilization in the previous sampling time.
Im Falle der achsweisen Betrachtung wird der Reibwert μmaχ,vA/HA entlang der Aufstandskraft-abhängigen Kennlinie in Fig. 5 auf die Räder der entsprechenden Achse verteilt. Diese Verteilung berücksichtigt, dass bei Kurvenfahrt die Kraftschlussausnutzung und damit auch der maximale Reibwert am entlasteten, inneren Rad stets höher ist als am belasteten, äusseren Rad. Die
Verteilungskurve ist nichtlinear, z.B. exponentiell. Ein achsweise ermittelter maximaler Reibwert von z.B. 1.0 muß je nach Radentlastung/-belastung auf der Kurveninnenseite mit einem Wert von 1.8 und auf der Kurvenaussenseite mit 0.9 berücksichtigt werden.
In the case of an axle-wise consideration, the coefficient of friction μ ma χ, vA / HA is distributed along the characteristic force-dependent characteristic curve in FIG. 5 to the wheels of the corresponding axle. This distribution takes into account the fact that when cornering, the force utilization and thus also the maximum coefficient of friction on the relieved inner wheel is always higher than on the loaded outer wheel Distribution curve is non-linear, e.g. exponential. An axially determined maximum coefficient of friction of 1.0, for example, must be taken into account with a value of 1.8 on the inside of the curve and 0.9 on the outside of the curve, depending on the wheel load / load.
Claims
1. Verfahren zum Ermitteln eines maximalen Reibwertes zwischen Reifen und Fahrbahn eines Fahrzeugs aus Kraftinformationen, die bei dem Kontakt zwischen Reifen und Fahrbahn auftreten, dadurch gekennzeichnet, dass Werte, die die Kraftschlussausnutzung in Längs- und/oder Querrichtung darstellen, auf Basis von gemessenen und/oder geschätzten Grossen, die die auf die einzelnen Räder und Reifen wirkenden aktuellen Längskräfte, Seitenkräfte sowie die Aufstandskrafte wiedergeben, unter Einbeziehung von gemessenen oder berechneten aktuellen Zustandsgrößen, die den Schräglaufwinkel und/oder die1. A method for determining a maximum coefficient of friction between the tire and the lane of a vehicle from force information that occurs in the contact between the tire and the lane, characterized in that values that represent the adhesion utilization in the longitudinal and / or transverse direction, based on measured and / or estimated values, which reflect the current longitudinal forces, lateral forces and the contact forces acting on the individual wheels and tires, including measured or calculated current state variables, the slip angle and / or the
Schräglaufwinkelgeschwindigkeit und/oder den Längsschlupf und/oder die Langsschlupfgeschwindigkeit wiedergeben, permanent ermittelt werden, und die ermittelten Werte mit Schwellwerten verglichen und einer Auswertung zur Bestimmung des maximalen Reibwertes unter Einbeziehung von weiteren Hilfsgrößen, wie Längskraft, Seitenkraft, Aufstandskraft, Längsbeschleunigung, Querbeschleunigung, Fahrzeugmasse und/oder Ersatzgrößen zugeführt werden, wenn die Vergleichsergebnisse die Schwellwerte unterschreiten.Play slip angle speed and / or the longitudinal slip and / or the slow slip speed, be determined permanently, and compare the determined values with threshold values and an evaluation to determine the maximum coefficient of friction including further auxiliary variables such as longitudinal force, lateral force, contact force, longitudinal acceleration, lateral acceleration, vehicle mass and / or substitute variables are supplied if the comparison results fall below the threshold values.
2. Verfahren nach Anspruch 1, gekennzeichnet durch die Schritte Ermitteln von Gradienten der2. The method according to claim 1, characterized by the steps of determining the gradient of
Kraftschlussausnutzung zwischen Reifen und Fahrbahn in Längsrichtung als Funktion des Schlupfes oder der Schlupfgeschwindigkeit,Use of traction between the tire and the road in the longitudinal direction as a function of the slip or the slip speed,
Ermitteln von Gradienten der Kraftschlussausnutzung zwischen Reifen und Fahrbahn in Querrichtung als Funktion des Schräglaufwinkels oder der SchräglaufWinkelgeschwindigkeit, Vergleichen der Gradienten mit Schwellwerten und Ermitteln des maximalen Reibwertes aus den Längs-, Seiten, Aufstandskräften oder den Längskräften, den Aufstandskräften, der Querbeschleunigung, der Längsbeschleunigung, der Fahrzeugmasse und/oder Ersatzgrössen, wenn das Vergleichsergebniss die Schwellwerte unterschreitet.Determining gradients of the adhesion utilization between the tire and the road in the transverse direction as a function of the slip angle or the slip angle speed, Comparing the gradients with threshold values and determining the maximum coefficient of friction from the longitudinal, lateral, contact forces or the longitudinal forces, the contact forces, the lateral acceleration, the longitudinal acceleration, the vehicle mass and / or substitute values if the comparison result falls below the threshold values.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass bei einem Vergleichsergebnis, bei dem der ermittelte Wert den Schwellwert nicht unterschreitet, ein Ersatzwert als Reibwert verwendet wird.3. The method according to claim 1, characterized in that in a comparison result in which the determined value does not fall below the threshold value, a substitute value is used as the coefficient of friction.
4. Verfahren nach Anspruch 2, gekennzeichnet durch die Ermittlung der Gradienten aus den mit den Aufstandskräften normierten Längs- und/oder Seitenkräften mindestens eines Rades oder mindestens einer Fahrzeugachse und dem Schräglaufwinkel oder der Schräglaufwinkelgeschwindigkeit oder dem Schlupf oder der Schlupfgeschwindigkeit mindestens eines Rades.4. The method according to claim 2, characterized by the determination of the gradients from the longitudinal and / or lateral forces normalized with the contact forces of at least one wheel or at least one vehicle axis and the slip angle or the slip angle speed or the slip or the slip speed of at least one wheel.
5. Verfahren nach Anspruch 4, gekennzeichnet durch die Ermittlung der Gradienten aus der mit den Aufstandskräften normierten Längskraft mindestens einer Fahrzeugachse nach der Beziehung5. The method according to claim 4, characterized by determining the gradients from the longitudinal force normalized with the contact forces of at least one vehicle axle according to the relationship
Gl. (2.9) C 'xxyyAAlIHHAA ~ = mit τpEq. (2.9) C 'x x y y A A l I H HA A ~ = with .tau..sub.p
Gl. (2.Eq. (2nd
6) FXιlιyA/HA = 'VA/m wobei die6) F XιlιyA / HA = ' VA / m where the
^z,VA/HA^ Z, VA / HA
Längskräfte der Vorderachse des Fahrzeugs nach Gl- (2.Longitudinal forces of the front axle of the vehicle Gl- (2nd
7) Fx A = -(-KByApB A - 2JRώRyA) und/oder die r7) F x A = - (- K ByA p BA - 2J R ώ RyA ) and / or the r
Längskräfte der Hinterachse des Fahrzeugs nachLongitudinal forces of the rear axle of the vehicle
Gl. (2.Eq. (2nd
8) FXJIA = bestimmt werden.8) F XJIA = be determined.
Verfahren nach Anspruch 4, gekennzeichnet durch die Ermittlung der Gradienten aus der mit den Aufstandskräften normierten Seitenkraft mindestens einer Fahrzeugachse nach der BeziehungA method according to claim 4, characterized by determining the gradients from the lateral force normalized with the contact forces of at least one vehicle axle according to the relationship
G (jI nΛ i ni) r ^y.VA/HA - ~ ayyAIHA 1 T • g aG (j I n Λ in i ) r ^ y.VA / HA - ~ ayyAIHA 1 T • ga
Verfahren nach Anspruch 2 oder 4, dadurch gekennzeichnet, dass die Längskraft-Umfangschlupf-Gradienten für mindestens ein Rad nach der BeziehungA method according to claim 2 or 4, characterized in that the longitudinal force circumferential slip gradients for at least one wheel according to the relationship
Gll. n (1.5,) r Cx = dF*>—» = dF*'» dt » ^ lr. dλ dt dλ TA λ und/oder die Seitenkraft-Schräglaufwinkel-Gradienten für mindestens ein Rad nach der BeziehungGl l . n (1.5,) r C x = dF *> - »= dF * '» dt »^ l r. dλ dt dλ T A λ and / or the lateral force slip angle gradient for at least one wheel according to the relationship
ermittelt werden. be determined.
Verfahren nach einem der Ansprüche 1, 2, 4 bis 6, dadurch gekennzeichnet, dass die Aufstandskrafte modellbasiert nach der Beziehung Method according to one of claims 1, 2, 4 to 6, characterized in that the riot forces based on the model according to the relationship
bestimmt werden.be determined.
9. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die maximale Kraftschlussausnutzung radindividuell nach der Beziehung9. The method according to any one of claims 1 to 7, characterized in that the maximum adhesion utilization of the wheel individually according to the relationship
ermittelt wird. is determined.
10. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die maximale Kraftschlussausnutzung achsweise nach der Beziehung10. The method according to any one of claims 1 to 7, characterized in that the maximum adhesion utilization by axis according to the relationship
für die Hinterachse des Fahrzeugs oder for the rear axle of the vehicle or
für die Vorderachse ermittelt wird. is determined for the front axle.
11. Verfahren nach Anspruch 1 oder 2, gekennzeichnet durch die Schritte11. The method according to claim 1 or 2, characterized by the steps
Ermitteln der Schräglaufwinkelgeschwindigkeit ά an der Vorder- und Hinterachse des Fahrzeugs nach Massgabe der Querbeschleunigung ay , der Längsgeschwindigkeit v^. , derDetermine the slip angle speed ά on the front and rear axles of the vehicle in accordance with the lateral acceleration a y , the longitudinal speed v ^. , the
Gierbeschleunigung ψ , der Gierwinkelgeschwindigkeit ψ , der Lenkwinkelgeschwindigkeit δ und/oder dem Abstand zwischen dem Schwerpunkt und der Vorderachse lv bzw. der Hinterachse lh ,Yaw acceleration ψ, the yaw angular velocity ψ, the steering angular velocity δ and / or the distance between the center of gravity and the front axle l v or the rear axle l h ,
Vergleichen der Schräglaufwinkelgeschwindigkeit ά mit Schwellwerten S ,Comparing the slip angle speed ά with threshold values S,
Ermitteln der Seitenkraft-Schräglaufwinkel-Gradienten Cy an jedem Rad in Abhängigkeit von dem Vergleichsergebniss Determine the lateral force slip angle gradient C y on each wheel as a function of the comparison result
Ermitteln des maximalen Reibwertes max nach den Beziehungen für die maximale Kraftschlussausnutzung (Gl.2.13, 2.15, 2.17), wenn Cy < Sy ist.Determine the maximum coefficient of friction max according to the relationships for the maximum adhesion utilization (Eq. 2.13, 2.15, 2.17) if C y <S y .
12. Mikrocontrollerprogrammprodukt, das direkt in den Speicher einer Fahrdynamikregelung, wie ESP, ASR, ABS-Regelung und dgl . , geladen werden kann und Softwarecodeabschnitte umfasst, mit denen die Schritte gemäss einem der Ansprüche 1 bis 10 ausgeführt werden, wenn das Produkt auf einem MikroController läuft. 12. Microcontroller program product, which is stored directly in the memory of a vehicle dynamics control, such as ESP, ASR, ABS control and the like. , can be loaded and comprises software code sections with which the steps according to one of claims 1 to 10 are carried out when the product runs on a microcontroller.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10208815A DE10208815B4 (en) | 2002-03-01 | 2002-03-01 | Method for determining a maximum coefficient of friction |
DE10208815 | 2002-03-01 | ||
PCT/EP2003/001967 WO2003074337A1 (en) | 2002-03-01 | 2003-02-26 | Method for determining a maximum coefficient of friction |
Publications (1)
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EP1483143A1 true EP1483143A1 (en) | 2004-12-08 |
Family
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Family Applications (1)
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EP03743341A Withdrawn EP1483143A1 (en) | 2002-03-01 | 2003-02-26 | Method for determining a maximum coefficient of friction |
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US (1) | US20050234628A1 (en) |
EP (1) | EP1483143A1 (en) |
JP (1) | JP2005518987A (en) |
DE (1) | DE10208815B4 (en) |
WO (1) | WO2003074337A1 (en) |
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Also Published As
Publication number | Publication date |
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WO2003074337A1 (en) | 2003-09-12 |
DE10208815A1 (en) | 2003-09-18 |
US20050234628A1 (en) | 2005-10-20 |
JP2005518987A (en) | 2005-06-30 |
DE10208815B4 (en) | 2011-05-19 |
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