EP1628862A1 - Procede et dispositif pour determiner une grandeur de frottement representant les frottements qui agissent entre une chaussee et des pneumatiques de vehicule - Google Patents

Procede et dispositif pour determiner une grandeur de frottement representant les frottements qui agissent entre une chaussee et des pneumatiques de vehicule

Info

Publication number
EP1628862A1
EP1628862A1 EP04721878A EP04721878A EP1628862A1 EP 1628862 A1 EP1628862 A1 EP 1628862A1 EP 04721878 A EP04721878 A EP 04721878A EP 04721878 A EP04721878 A EP 04721878A EP 1628862 A1 EP1628862 A1 EP 1628862A1
Authority
EP
European Patent Office
Prior art keywords
value
determined
vehicle
friction
slip
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Withdrawn
Application number
EP04721878A
Other languages
German (de)
English (en)
Inventor
Daniel Buck
Michael Diebel
Hans-Georg Engel
Sinan Kazan
Frank-Werner Mohn
Martin Wenz
Richard Zimmer
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.)
Mercedes Benz Group AG
Original Assignee
DaimlerChrysler AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by DaimlerChrysler AG filed Critical DaimlerChrysler AG
Publication of EP1628862A1 publication Critical patent/EP1628862A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • 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

Definitions

  • the invention relates to a method and a device for determining a coefficient of friction, which represents the coefficient of friction between the roadway and vehicle tires.
  • Document DE 37 05 983 AI describes a device for monitoring the degree of utilization of the prevailing road friction when braking and / or accelerating a motor vehicle.
  • the device has sensors for detecting the vehicle acceleration and the wheel speeds. From these variables, the instantaneous wheel slip is continuously determined for at least one wheel and a function is formed which reflects the functional dependence of the wheel slip on the vehicle acceleration. The function determined in this way is compared with stored slip characteristic curves in order to select the slip characteristic curve which comes closest to the function and thus corresponds to the currently prevailing road condition. The relationship between the highest detected acceleration value and the maximum of the slip characteristic is then formed. This ratio is a measure of how far the wheels are from the block driving or spinning, ie how great is the prevailing road surface friction.
  • a method for determining the adhesion / slip characteristic is known from document DE 43 00 048 AI. For this purpose, when driving the vehicle, it is concluded from the measured value pairs of the slip and the coefficient of adhesion used for a given slip that the course of the respective tire characteristic curve in the overall coefficient of adhesion / field of slip is determined.
  • the utilization of the frictional connection associated with the respective value of the brake slip is determined mathematically as a function of the measured braking deceleration of the vehicle, the rear axle load component and the wheelbase-related center of gravity of the vehicle.
  • a method for determining the coefficient of friction is known from Japanese laid-open publication JP 11248438 A, in which the coefficient of friction is dependent on the determined wheel slip and vehicle acceleration is determined.
  • a slip-based method or a corresponding device for determining a coefficient of friction value which represents the coefficient of friction between the roadway and vehicle tires, is to be created, which is compared to the methods or devices known from the prior art with simpler means, ie enables this determination with less technical effort.
  • a wheel slip variable that describes the wheel slip present on this vehicle wheel is determined for at least one vehicle wheel.
  • the coefficient of friction is determined as a function of this wheel slip size.
  • wheel slip sizes are determined at various, in particular successive times, during a predetermined operating state of the vehicle, and the value-based frequency distribution is determined for these wheel slip sizes or for axle-specific slip sizes determined as a function of these wheel slip sizes. This value-based frequency distribution is evaluated to determine the coefficient of friction.
  • warning system which uses a navigation system to determine the course of the road on the route in front of the vehicle and which uses a display device to indicate to the driver by means of traffic signs symbolizing danger spots that there are danger spots in the course of the road such as curves and / or roundabouts and / or intersections.
  • Fig. 1 for the first embodiment is a schematic
  • FIG. 2 shows a flowchart for the first embodiment, which represents the method according to the invention which runs in the device according to the invention
  • Fig. 3 is a schematic for the second embodiment
  • FIG. 5 shows a flowchart for the second embodiment, which represents the method according to the invention running in the device according to the invention
  • ⁇ b shows a first decision criterion used in the second embodiment
  • Fig. ⁇ c a second decision criterion used in the second embodiment.
  • Block 101 represents the core of the device according to the invention.
  • the method according to the invention runs, which is illustrated in FIG. 2 with the aid of a flow chart and which is described in detail below.
  • wheel speed variables vij which describe the wheel speeds of the individual vehicle wheels
  • Block 102 is wheel speed sensors assigned to the individual vehicle wheels and means of conversion with which the detected wheel speeds are converted into wheel speeds.
  • the wheel speed sensors and the conversion means can be structurally separate, or each wheel speed sensor can have a corresponding conversion means. sen.
  • block 101 can also be supplied with wheel speed variables nij which describe the wheel speeds of the individual vehicle wheels. In this case, the necessary conversion takes place in block 101 and block 102 is wheel speed sensors assigned to the individual vehicle wheels.
  • the wheel speed variables vij can also be made available to block 101 on the basis of regulation and / or control devices contained in the vehicle.
  • These regulating and / or control devices can be, for example, devices for brake slip control and / or for traction control and / or for regulating the yaw rate, which is also referred to as yaw angular velocity, of the vehicle.
  • the nomenclature used above in connection with the two sizes vij and nij has the following meaning:
  • the index i indicates whether it is a front or a rear vehicle wheel.
  • the index j indicates whether it is a left or a right vehicle wheel.
  • a yaw angular velocity variable ⁇ which describes the filtered yaw angular velocity
  • block 103 is a yaw rate sensor and a corresponding filter means.
  • the yaw rate sensor and the filter means can form a structural unit.
  • the two components can also be arranged spatially separated in the vehicle.
  • an unfiltered yaw angular velocity variable can also be supplied to block 101. In this case, the required filtering is carried out in block 101.
  • the yaw angular velocity variable ⁇ fll or the unfiltered yaw angular velocity variable can also be assigned to block 101 of regulation and / or control devices contained in the vehicle, in particular by a device for regulating the yaw rate of the vehicle.
  • a signal BLS which is generated by a brake light switch 104 and which indicates whether the driver has actuated the brake pedal or not, is also supplied to block 101.
  • the method according to the invention runs by processing the input variables vij, ⁇ fll and BLS supplied to it.
  • a coefficient of friction value F ⁇ is determined which represents the coefficient of friction between the roadway and vehicle tires.
  • the coefficient of friction value F ⁇ does not reflect the value of the coefficient of friction, but merely indicates whether the road is rough or slippery. This means that with the coefficient of friction F ⁇ it is not possible to make a quantitative but only a qualitative statement regarding the coefficient of friction, namely whether it is a smooth or a non-slip road. As can be seen from the main use of the coefficient of friction F ⁇ described below, with this main use it is entirely sufficient to be able to make a qualitative statement about the coefficient of friction between the roadway and vehicle tires.
  • the coefficient of friction F ⁇ is fed to a block 105, which is a display device which is integrated, for example, in the dashboard, in this case the display device is integrated in the instrument cluster, or in the center console of the vehicle, in this case it can is the display of a navigation system, is installed.
  • a display device which is integrated, for example, in the dashboard, in this case the display device is integrated in the instrument cluster, or in the center console of the vehicle, in this case it can is the display of a navigation system, is installed.
  • the driver can be shown whether the vehicle is currently on a road with a smooth or non-slip surface. Driving on a smooth road can be indicated to the driver, for example, by showing a snowflake. The driver can thus, for example, adjust to a smooth road surface when starting off.
  • the block 105 or the display device 105 is part of a warning system contained in the vehicle.
  • the illustration of such a warning system in FIG. 1 has been omitted for the sake of clarity. However, the functionality of such a warning system will be described below for better understanding.
  • Such a warning system uses a navigation system to determine the course of the road in front of the vehicle. Danger points such as curves, roundabouts, intersections etc. are shown to the driver in a display device, this is block 105 shown in FIG. 1, by showing a traffic sign symbolizing the danger point. For example, if the driver approaches a curve and the curvature of this curve exceeds a certain dimension, the curve in front of him is indicated by the display of a corresponding warning symbol, in this case it can be arrows, for example, in the display device. Two different embodiments of such a warning system are conceivable. In a first embodiment, a warning is given only when the vehicle speed exceeds a speed threshold value corresponding to the danger point.
  • the warning and thus the information is displayed regardless of the vehicle speed.
  • further quantities can be supplied to block 101, which is indicated by the dashed lines of the two blocks 107 and 108.
  • a quantity T describing the outside temperature can be supplied to block 101 from outside .
  • block 101 can be supplied with a size of windshield wiper, which represents the operation of the windshield wiper.
  • FIG. 1 A further option is shown in FIG. This further option concerns the output and utilization of the coefficient of friction F ⁇ .
  • the coefficient of friction F ⁇ can also be supplied to various regulating and / or control devices contained in the vehicle, which are represented by a block 106 shown in broken lines.
  • the information of the coefficient of friction value F ⁇ can be used, for example, to modify the regulation and / or control algorithms of the regulation and / or control devices. Brake and slip control and / or traction control and / or yaw rate control and / or distance control may be mentioned by way of example as possible regulation and / or control devices.
  • the coefficient of friction F ⁇ can also be processed in the warning systems mentioned above. This processing then leads to the information for the driver about curves, intersections, etc. being output earlier, for example on a smooth road surface, ie with a low coefficient of friction.
  • the method according to the invention begins with a step 201, which is followed by a step 202.
  • steps 202 various initializations are carried out. So in this step are a time counter t count here ? a predetermined number of slip class counters ⁇ kZäh e r, and a velocity keits Sungsdorfn Attacher a Ze i he g initialized. The meaning of the individual counters or pointers is discussed in the description of the following steps.
  • Step 202 is followed by step 203, in which the input variables to be supplied to block 101 are provided. Specifically, it concerns the wheel speed variables vij and / or the yaw angle speed variable ⁇ ß! and / or around the signal BLS.
  • a speed variable vref is determined which describes the vehicle reference speed. Because in order to determine wheel slips, you need the actual speed of the vehicle over the ground.
  • the method described below for determining the speed variable vref relates to a vehicle Rear-wheel drive. Appropriate adjustments are necessary for a vehicle with front-wheel drive or all-wheel drive.
  • the BLS signal distinguishes between these two cases.
  • the brake light switch 104 is not actuated in the drive case.
  • the signal it generates has, for example, the value 0.
  • the brake light switch 104 is actuated in the event of braking.
  • the signal generated by it has the value 1, for example. That the two cases of drive case and brake case are differentiated with the aid of a signal which is generated by a brake light switch 104.
  • the speed variable vref is determined by averaging the wheel speeds of the two non-driven wheels. In a vehicle with rear-wheel drive, therefore, by averaging the wheel speeds vvj of the front wheels. In order to improve the determination of the speed variable vref, the wheel speeds vvj of the front wheels are limited to the smaller of the wheel speeds vhj of the rear wheels. The reason for this limitation is that in the case of a drive, a non-driven wheel cannot be faster than a driven wheel.
  • the speed variable vref is determined by averaging the wheel speeds of the fastest and second fastest wheels. The reason for this is as follows: When braking, the two braked and therefore slower wheels should not be used when determining the speed variable vref.
  • a gradient limitation can be carried out when determining the speed variable vref. This gradient limitation is implemented as follows: As can be seen from the illustration in FIG. 2, the method shown is a cyclic method. Consequently, as long as the determination of the speed variable vref is running, a value for this speed variable vref is determined for successive time steps that are spaced apart by the cycle time.
  • the cycle time which is determined by the computing cycle of the processor used, is typically on the order of approximately 10 to 20 milliseconds.
  • the value of the speed variable vref for the subsequent time step is based on the value of the speed variable vref that was present for the previous time step, taking into account a value for the change in the speed variable vref that occurs within a Maximum cycle time is determined. This is a limitation.
  • the cycle time also specifies the time grid in which, for example, the values of the input variables are read in in block 101.
  • the speed variable vref is determined by averaging the wheel speeds vvj of the rear wheels.
  • a speed change variable a xF ii t which describes the acceleration and / or deceleration behavior of the vehicle, is determined.
  • an unfiltered speed change variable a x is first determined from the speed variable vref using the following equation:
  • the variable T represents the cycle time, which, as already mentioned, typically has a value of 10 to 20 milliseconds.
  • the variable t denotes the current time step. Accordingly, t-1 denotes the previous time step. Equation (1) represents a difference quotient.
  • the unfiltered speed change variable a x can also be determined as a mathematically formulated time derivative of the speed variable vref.
  • step 205 filtering- dependent change in vehicle speed turns the unfiltered speed change variable a x into the speed change variable a xF ii t (t) using the equation
  • the expression max means that the larger value is selected from the two values in brackets.
  • the expression abs means that the amount of the bracketed expression is formed.
  • the filter described by equation (2) has the characteristics of a low-pass filter. It is averaging that is tracked depending on the speed of the vehicle.
  • the speed change variable a xF iit is formed as a function of the speed variable vref by forming a difference quotient or a time derivative and subsequent filtering, with the filtering realizing an average value that is tracked depending on the speed of the vehicle.
  • step 206 which follows the step 205, it is determined whether there is a cornering or not. To this
  • the yaw rate ist ß is evaluated.
  • it is checked whether the value of the yaw angular velocity variable embassy ß is less than a predetermined threshold value.
  • the predefined threshold value can, for example, be on the order of approximately 0.6 degrees / second. If the value of the yaw rate variable ⁇ ßl is smaller than the predetermined threshold value, which is equivalent to the fact that there is no noticeable cornering, the coefficient of friction value F ⁇ can be determined, which is why a step 207 is carried out after step 206.
  • the value of the yaw rate ssen ß is greater than the predetermined Threshold value, which is equivalent to the fact that there is a noticeable cornering, the determination of the coefficient of friction F ⁇ cannot be carried out. For this reason, a step is made back from step 206 to step 202.
  • the query taking place in step 206 ensures that the determination of the coefficient of friction F ⁇ is carried out only when driving straight ahead. Because when cornering due to the cornering there are different slip values on the two sides of the vehicle, which would lead to falsification when determining the coefficient of friction.
  • a value for the longitudinal acceleration of the vehicle is determined as a function of the speed variable vref and the yaw angle speed variable ⁇ ⁇ . This is compared, for example, by forming the quotient with the speed change variable a xF iit, from which a minimum coefficient of friction can be determined, which serves as an estimate of the coefficient of friction present between the roadway and the vehicle tire.
  • a predetermined threshold value it is checked whether the magnitude of the speed change variable a xF_. ⁇ t () is greater than a predetermined threshold value. If this is the case, then step 208 is carried out after step 207. If, on the other hand, this is not the case, a step 213 to be described is carried out after the step.
  • the time counter t Zah - ler increments. This can be according to the relationship, for example
  • the time counter t e r Zah is incremented each time processing of step 208 to the value of the cycle time T.
  • the incrementation of the time counter carried out in step 208 has the following meaning: the two queries taking place in steps 206 and 207 determine whether a predetermined operating state of the vehicle is present, in which only the determination of the coefficient of friction F ⁇ is carried out.
  • This predetermined operating state of the vehicle is defined by the yaw angle speed variable ⁇ fl and / or the speed change variable a xF iit (t).
  • This predefined operating state of the vehicle is a straight-ahead drive in which there is a minimum acceleration or a minimum deceleration of the vehicle.
  • the incrementing of the time counter in step 208 is intended to document how long this predetermined operating state of the vehicle has been present.
  • step 209 the method according to the method according to the invention for determining the coefficient of friction F ⁇ Required slip monitoring carried out.
  • wheel slip variables ⁇ ij for the individual vehicle wheels are first determined in a known manner as a function of the wheel speed variables vij and the speed variable vref.
  • a vehicle is based on a rear-wheel drive which has two axles.
  • a vehicle with front-wheel drive or a vehicle with all-wheel drive corresponding changes or adjustments have to be made in the following versions.
  • a slip size ⁇ VA is determined both for the front axle and a slip size ⁇ HA for the rear axle.
  • the slip size ⁇ VA is determined by averaging the two wheel slip sizes ⁇ vj, ie the wheel slip sizes of the two front wheels.
  • the two slip sizes ⁇ V A and ⁇ H A are used as a basis for further slip monitoring.
  • the slip monitoring is carried out axially.
  • the slip monitoring is generally carried out individually for the wheel, ie by evaluating the wheel slip variables ⁇ ij. In this case, a corresponding statement about the existing coefficient of friction is then obtained for each of the vehicle wheels.
  • the slip size ⁇ Ha determined for the rear axle is evaluated.
  • the slip size ⁇ VA determined for the front axle is evaluated.
  • the actual slip monitoring takes place as follows: With the help of driving tests, it was determined in advance which value range for the wheel slip sizes ⁇ ij and thus the axial slip sizes ⁇ VA and ⁇ HA can be expected. The entire range of values determined was divided into individual slip classes. The subdivision can be finer for small slip values, ie the interval length of the individual slip class is smaller for small slip values. Whereas the subdivision towards larger slip values can become coarser, which means that with larger slip values the interval length of the individual slip class is larger. An associated slip class counter ⁇ kZa ier is assigned to each of the slip classes determined in this way.
  • step 209 is carried out as long as the conditions of steps 206 and 207 are fulfilled.
  • step 209 and thus the slip monitoring or classification of the slip sizes taking place in it is carried out during a predetermined operating state of the vehicle for a large number of successive points in time.
  • This classification or sorting of the slip sizes into the individual slip classes results in a value-based frequency distribution for the axial slip sizes.
  • step 209 Every time step 209 is carried out, an axle-wise slip size ⁇ VA or ⁇ HA is determined. This slip size is then assigned to one of the slip classes depending on its value. Here, the corresponding to this class slip slip class counter ⁇ k Zah e r is incremented. This process is repeated as long as the conditions of steps 206 and 207 are met within the time frame defined by the query contained in step 210. As a result, this procedure results in a value-based frequency distribution for the slip sizes.
  • the slip monitoring can also be carried out individually for the wheel.
  • This has the advantage that in this case, for example, so-called ⁇ -split situations can also be recognized.
  • the slip monitoring carried out individually for the wheel has the advantage that even very short control interventions, such as that of one Yaw rate control can be performed, can be clearly recognized. Against this background, it could be advisable to switch from axle-by-wheel to wheel-specific slip monitoring in the event of such short control interventions. Long control interventions are recorded by the axle-by-hatch observation, which is why it is not necessary to carry out wheel-specific control interventions in the presence of such control interventions.
  • the maximum value of the speed change variable a xFl ⁇ t (t) is also determined in step 209.
  • the current value of the speed change variable a xFl ⁇ t (t) is first determined each time step 209 is called. This current value of the speed change quantity a xFlit (t) is compared with the value of the speed change quantity pointer a pointer .
  • Step 209 is followed by step 210 already mentioned above.
  • a query is checked with the aid of whether the value of the time t payer Zah he i is greater than a predetermined first time threshold value is, for example, corresponds to a time period of 10 seconds. If this is not the case, the process jumps back from step 210 to step 203. If, however, the time counter z here greater than the predetermined first time threshold value, a step 211 is then carried out after step 210.
  • step 211 the coefficient of friction size F ⁇ is determined by evaluating the value-based frequency distribution and the maximum value of the speed change variable a x ⁇ . ⁇ t (t).
  • the percentage distribution of the slip size ⁇ VA or ⁇ HA over the individual slip classes is first determined.
  • the sum of all slip class counters is formed and the individual slip class counters divided by this sum.
  • the coefficient of friction F ⁇ is then determined.
  • Table Percentage slip given at different vehicle accelerations or decelerations on different road surfaces.
  • the table above has the following structure: Apart from the header, the table is essentially divided into four line complexes. Two line complexes concern non-slip road conditions and two line complexes concern smooth road conditions.
  • a first line complex describes various grippy road conditions on dry asphalt
  • a second line complex describes various grippy road conditions on uneven snow
  • a third line complex describes various smooth road conditions on flat snow
  • a fourth line complex describes driving situations in which the vehicle is on a smooth road and at the same time brief control interventions by a brake slip controller (ABS) and / or a traction slip controller (ASR) and / or a yaw rate controller (ESP) expire.
  • ABS brake slip controller
  • ASR traction slip controller
  • ESP yaw rate controller
  • Each of the lines belonging to the four line complexes has the following structure according to the header of the table:
  • a range of values for the speed change variable a x _ F ii t (t) is given.
  • slip class the value range to be expected from the axially slip sizes ⁇ V A or ⁇ H A or the wheel slip sizes ⁇ ij, which is to be expected from experience, is divided into individual slip classes.
  • the present embodiment is one It is subdivided into 9 slip classes, which should not be a limitation, of course, this range of values can also be divided into finer or coarser ones. According to the prevailing road conditions, a distinction is made according to the four line complexes mentioned above, and according to the respective range of values for the speed change variable a xF nt (t), there is one for the axle-wise slip variables ⁇ V A or ⁇ H A or the wheel slip variables ⁇ ij characteristic distribution, a so-called frequency distribution in which a frequency can be specified for each of the slip classes. This frequency distribution can be determined empirically using driving tests, for example. The frequency distribution indicates how the axles occurring when the vehicle is traveling on a smooth or rough road
  • the number of individual lines combined to form a line complex depends on how finely the value ranges for the speed change variable a xF nt (t) are divided.
  • each of the lines contained in the table describes a frequency distribution that is characteristic of the respective road conditions and the respective value range of the speed change variable a ⁇ pii t (t) for the wheel slip variables ⁇ ij or for the axially slip variables ⁇ VA or ⁇ Ha .
  • the coefficient of friction F ⁇ or the information to be assigned to the coefficient of friction F ⁇ is determined as follows: First, by evaluating the maximum value of the speed change variable a xF üt (t), the rows of the table in question are determined. For this purpose, it is checked in which of the intervals listed in the first column this maximum value is contained. Subsequently, it is determined which of these rows in question has a distribution that corresponds to the frequency distribution as a value determined for the axially slip sizes ⁇ V A or ⁇ HA or to the value-based frequency distribution determined for the wheel slip sizes ⁇ ij. For this purpose, it is checked for each line in question whether the for all
  • Slip class counter ⁇ Z ähier the percentage value assigned to it is contained in the interval of the respectively associated slip class. If there is a line in which there is a match for all slip classes, this line determines the information to be assigned to the coefficient of friction value F ⁇ . Depending on the result, the information "smooth" or “handy” is assigned to the coefficient of friction F ⁇ , or a correspondingly coded signal value.
  • a separate coefficient of friction value can be determined for several successive, identical, predetermined operating states of the vehicle. In other words, several mutually independent determinations of coefficient of friction are carried out in succession.
  • the method according to the invention can be improved in that an average value is formed from several such coefficient of friction values.
  • the above table can be expanded with characteristic slip distributions for additional road surfaces such as gravel or sand and for additional road properties, for example a roadway covered with leaves or water on the road. Accordingly, the table should be supplemented with further line complexes.
  • a step 212 is carried out in which the further processing of the coefficient of friction F ⁇ takes place.
  • the information of the coefficient of friction F ⁇ is shown to the driver with the aid of the display device 105 shown in FIG. That the driver is informed whether the road currently being used has a grippy or smooth surface.
  • the coefficient of friction F ⁇ can be fed to other regulating and / or control devices 106 arranged in the vehicle for further processing.
  • the system jumps back to step 202.
  • step 207 In the event that it is determined in step 207 that the magnitude of the speed change variable a xi ⁇ t (t) is smaller than the predetermined threshold value, the step 213 already mentioned is then carried out after step 207.
  • a query is used to check whether the value of the time counter t Zier is greater than a predetermined second time threshold value, which corresponds, for example, to a time period of 0.5 seconds. If this is not the case, the process jumps back from step 213 to step 202. If, on the other hand, the time counter t Za ie r is greater than the second time threshold value, then step 211 is carried out after step 213.
  • the two in steps 210 and 213 by evaluation of the time counter t Zah he i performed time queries have the following background:
  • time query of step 213 that the determination of Reibwertiere F ⁇ is only carried out to ensure, when the predetermined operating state of the vehicle, a There is a predetermined minimum duration and so a large number of wheel slip sizes ⁇ ij has been determined that the determination of the coefficient of friction F ⁇ can be regarded as reliable.
  • the time query contained in step 210 has the function of ending the determination of the coefficient of friction F ⁇ when a predetermined period of time has been reached or exceeded, the value of which can be set at 10 seconds, for example.
  • the background to this is that, after a certain period of time, so many wheel slip sizes ⁇ ij have been determined that an additional determination of further wheel slip sizes ⁇ ij would not bring about an improvement in the quality of the determination of the coefficient of friction F ⁇ .
  • a first optional step by evaluating the quantity T outside describing the outside temperature, it can be checked whether the outside temperature is greater than a predetermined temperature threshold value which, for example, represents a temperature of 15 degrees Celsius. If this is the case, it can be assumed that there is a non-slip road. In this case, the processing of steps 202 to 213 can be omitted, and the large F ⁇ can be directly assigned a value that represents a grippy road surface.
  • a predetermined temperature threshold value which, for example, represents a temperature of 15 degrees Celsius. If this is the case, it can be assumed that there is a non-slip road.
  • the processing of steps 202 to 213 can be omitted, and the large F ⁇ can be directly assigned a value that represents a grippy road surface.
  • a second optional step can be inserted.
  • this second optional step it can be checked by evaluating the outside temperature describing the large T outside and the large F SC e-.benscher, which represents the operation of the windshield wiper, whether a low outside temperature is present and the windshield wiper is operating at the same time. If this is the case, ie if there is precipitation and the temperature is low at the same time, it can be assumed that the road surface conditions have a low coefficient of friction. In this case too, steps 202 to 213 can be omitted, and the large F ⁇ can be directly assigned a value that represents a smooth road surface.
  • this method according to the invention takes advantage of the fact that the tire slip behavior is typically different on a grippy or smooth road surface.
  • the relationship shown in a ⁇ -slip curve is thus used.
  • the slip behavior is determined during a predetermined operating state of the vehicle.
  • This predefined operating state of the vehicle is a straight-ahead drive during an acceleration or deceleration phase of the vehicle. It is therefore a speed change size defined operating state of the vehicle.
  • the axially slippage variables ⁇ V A or ⁇ HA are only determined during an acceleration or deceleration phase of I a xF iit I> 0.5 m / s 2 and a minimum time of 0.5 s and a maximum time of 10 s .
  • the slip size is calculated and classified in each cycle and the number of occurrences is stored in the corresponding slip class and the maximum acceleration or Deceleration value determined during the acceleration or deceleration phase.
  • the absolute number of occurrences of the hatches is calculated in a percentage distribution of the hatches over the hatch classes.
  • the determined values that is to say the percentage values of the slip classes and the maximum acceleration or deceleration value, are then checked as to whether they lie within a certain range. For the individual slip and for the determined acceleration or deceleration, there is a range that is clearly determined by means of a minimum and a maximum permissible value.
  • a table hit is found when all area conditions of a table row are met. After each slip observation phase, the table is run through completely, which means that multiple hits are possible.
  • FIG. 3 shows an overview of a second embodiment of the device according to the invention, a block 301 representing the core of this device. The specific structure of this block is explained in more detail with reference to FIG. 4.
  • various input variables are fed to block 301.
  • wheel speed variables nij which describe the wheel speeds of the individual vehicle wheels, are supplied to block 301.
  • Block 302 is wheel speed sensors assigned to the individual vehicle wheels.
  • block 301 is supplied with wheel speed variables vij rather than wheel speed variables nij.
  • block 302 would correspond to block 102.
  • Block 301 is supplied with a yaw rate variable pap ⁇ 1 which describes the filtered yaw rate.
  • Block 303 corresponds to block 103.
  • a transverse acceleration variable ay which describes the transverse acceleration of the vehicle, is supplied to block 301. Both the block 304 and the supply of the transverse acceleration variable ay are shown in dashed lines, which has the following meaning:
  • the transverse acceleration variable ay is not absolutely necessary for the implementation of the method according to the invention. Whether the lateral acceleration variable ay is required depends on the type of curve detection, which is discussed in connection with block 407.
  • a signal BLS generated by a brake light switch 305 is also fed to block 301. This is it a logic signal which, for example, assumes the TRUE state when the brake light switch is switched and thus the brake pedal is actuated, and which assumes the FALSE state when the brake light switch is not switched and therefore the brake pedal is not actuated. Otherwise, the brake light switch 305 corresponds to the brake light switch 104.
  • a quantity FEAAZ is supplied to block 301, which contains information about the state of regulation and / or control devices contained in the vehicle. That this variable contains information about whether one or which of these regulation and / or control devices is active and is carrying out a regulation or control intervention.
  • These devices can be, for example, devices for brake slip control and / or for traction control and / or for controlling the yaw rate of the vehicle.
  • the size FEAAZ has a different information content, depending on which of the above-mentioned devices is active. For example, if the device for brake slip control is active, the size FEAAZ contains information for each vehicle wheel as to whether or not there is brake slip on this vehicle wheel. If the device for traction control is active, the size FEAAZ contains information for each vehicle wheel as to whether traction is present on this vehicle wheel or not. In both cases, the information is provided on a wheel-specific basis for the following reason: Both an intervention for brake slip control and an intervention for traction control provide high braking or traction values for a longer period of time on individual vehicle wheels. When determining the value-based frequency This leads to a shift in the value-based frequency distributions determined individually for the wheel towards large amounts.
  • the information as to which wheel has a braking or traction slip is evaluated.
  • a plausibility check of the determined coefficient of friction values can also be carried out by means of an estimate of the transmitted force, which is a measure of the utilized and thus actually existing coefficient of friction. This is because the frequency distribution, which shows a high wheel slip, could give the impression that there is a slippery road surface. If, when estimating the transmitted force, it emerges that there is a high coefficient of friction, then there must be a slippery road rather than a slippery one. Details are discussed below.
  • the size FEAAZ only contains general information about whether a brake intervention is being carried out on one of the vehicle wheels or not. This blanket information is sufficient for the following reason: A brake intervention carried out as part of the control of the yaw angular velocity causes a yaw moment acting on the vehicle in order to stabilize a transversely dynamic, unstable condition of the vehicle in which not inconsiderable cross-slip occurs. Since the present method for determining the coefficient of friction is based on the evaluation of the longitudinal slip present on the individual vehicle wheels, the consideration of such driving situations when determining the frequency distribution by value would falsify the result, ie falsify the determined coefficient of friction. great lead.
  • a block 307 which for example is a temperature sensor and the block 107 corresponds to the block 301 is a variable describing the outdoor temperature T s Auss supplied.
  • a block F8 can optionally be supplied with a quantity F Re gen, which is indicated by the dashed line, starting from a block 308, which is, for example, a rain sensor.
  • block 301 is informed whether there is water on the windshield, for example due to precipitation or a wet road (splashing water).
  • information about the wiping activity of the windshield wiper can be communicated to block 301 with the aid of this variable. This information can be, for example, the number of wiping operations per unit of time.
  • the block 301 may be optional, which is indicated by the dashed representation, starting from a block 309 which corresponds to the block 108, a variable F ⁇ C heib e nis c h he be supplied, which represents the operating state of the wiper.
  • the disc disc size can contain various information.
  • a coefficient of friction value F ⁇ is determined which represents the coefficient of friction between the roadway and vehicle tires.
  • a measure is determined which reflects the road conditions in a qualitative manner, in the form of a distinction as to whether it is grippy or slippery, i.e. smooth road.
  • Block 310 is a warning system already described in connection with the first embodiment, which uses a display device to warn the driver of traffic signs symbolizing danger points to danger points in the course of the road points.
  • the display device is represented in FIG. 3 by a block 311, which corresponds to block 105.
  • the warning system 310 is notified of the Reibwertt determined, ie whether it is ⁇ is a smooth or non-slip surfaces.
  • the coefficient of friction value F ⁇ can assume the following states in detail and thus contain the following information: No coefficient of friction information is available, this state is assumed in particular when the coefficient of friction determination is initialized; there is a high coefficient of friction and therefore a grippy road surface; there is a low coefficient of friction and therefore a slippery or wet or smooth road surface.
  • the mode of operation of the warning system is influenced by the information communicated to the warning system 310 with the aid of the coefficient of friction F ⁇ , for example this information is used for switching characteristic curves or for access, ie the selection of parameters or maps dependent on the coefficient of friction.
  • this information is used for switching characteristic curves or for access, ie the selection of parameters or maps dependent on the coefficient of friction.
  • block 311 is a display device included in the warning system.
  • the information communicated to the display device 311 with the aid of the coefficient of friction F ⁇ makes the display of a warning symbol, which can be a snowflake, for example, and with which the driver is made aware of the presence of a low coefficient of friction and thus of a slippery or slippery road surface should be triggered.
  • the display device 311 can either be supplied with the same information as the warning system 310, ie information about the determined coefficient of friction class. Alternatively, only a request to display the warning symbol can be made. As a further alternative, no size or signal is supplied to the display device 311. In this case, the display device 311 is controlled by variables generated internally in the warning system 310.
  • wheel speed variables vij are determined on the basis of the wheel speed variables nij supplied to it.
  • the wheel speeds are converted into wheel speeds using a value for the wheel circumference.
  • the wheel speeds determined in this way are then filtered and output to a block 402 and a block 403 as wheel speed variables vij. If, as already described in connection with FIG. 3, block 301 is supplied to block 301 instead of wheel speed variables nij, block 401 is not necessary in this way. In this case, the functions of block 401 are contained in block 302.
  • the vehicle reference speed variable vref determined depending on the wheel speed variables vij supplied to it.
  • the speed variable vref determines the speed variable vref.
  • the speed variable vref is determined from this wheel speed by means of filtering. The filtering is intended to limit the speed variable vref to be determined.
  • the speed variable vref is determined by forming the mean value of the wheel speeds of the two non-driven wheels; in a vehicle with rear-wheel drive from the wheel speeds of the two front wheels.
  • a limitation is advantageously carried out in such a way that the temporal change in the speed variable is limited to a maximum value for two successive cycle times.
  • the speed variable vref is fed to a block 403, a block 406, a block 409 and optionally, as shown by the broken line, a block 407.
  • wheel slip variables ⁇ ij for the vehicle wheels are determined as a function of the wheel speed variables vij supplied to them and the speed variable vref.
  • ⁇ ij (vij - vref) / vref
  • the wheel slip sizes ⁇ ij are fed to a block 404 to be described below for further processing.
  • standstill detection is carried out by evaluating the speed variable vref supplied to it.
  • the speed variable vref is compared with a predetermined threshold value, which is, for example, in the order of 3 m / s.
  • the result of this evaluation is fed to a block 408 to be described with the aid of a quantity FStill, which corresponds to a logical variable.
  • the following assignment applies, for example, to the FStill variable: If the speed variable vref falls below the threshold value, an almost stationary vehicle or a vehicle at a standstill can be assumed, which is why the value TRUE is assigned to the FStill variable.
  • the speed variable vref is greater than the threshold value
  • the value FStill is assigned the value FALSE.
  • the size FStill thus contains information about whether the vehicle is almost standing or whether the vehicle is at a standstill.
  • cornering detection is carried out by evaluating the variables supplied to it.
  • the cornering detection is fed to block 408 with the aid of a variable FKurve, which corresponds to a logical variable.
  • the size FKurve thus contains information about whether the vehicle is cornering or not, or whether the vehicle is cornering or not.
  • the lateral acceleration variable ay and the yaw angle velocity variable ⁇ ß are evaluated in order to detect cornering.
  • this first embodiment there is a
  • the value FKurve is assigned the value TRUE. If, on the other hand, it is determined that both the transverse acceleration variable ay and the yaw angle velocity variable ⁇ ⁇ are below the respective associated threshold value, a straight-ahead drive is recognized. In this case, the value FKurve is assigned the value FALSE.
  • the threshold value for the lateral acceleration is, for example, in the order of 2 m / s ⁇ 2.
  • the threshold value for the yaw angular velocity is, for example, in the order of 10 ° / s.
  • the yaw angle speed variable ⁇ ⁇ and the speed variable vref are evaluated in order to detect cornering.
  • the following relationship is evaluated, in which a quotient formed as a function of the yaw angle speed variable ⁇ fl and the speed variable vref, taking into account the track width of the vehicle Fzg track width, is compared with a threshold value Sl:
  • cornering occurs when the above relation is fulfilled, that is to say when said quotient is greater than the threshold value S1, and the speed variable vref is greater than an associated threshold value which has, for example, the value zero.
  • the value FKurve is assigned the value TRUE. Otherwise there is no cornering, which is why the value FKurve is assigned the value FALSE.
  • the quotient represents a measure of the radius of the curve traveled by the vehicle.
  • the threshold value S1 corresponds to a multiple of the interval length of the slip classes, into which the considered slip area on which the frequency distribution is based is divided. The quotient is therefore compared with a multiple of the interval length, since a noticeable cornering, such as occurs during a turning maneuver, leads to different wheel slip on the two sides of the vehicle, which is noticeable in a shift in the value-based frequency distribution for the left and right vehicle wheels makes.
  • the threshold value S1 is therefore a measure of the shift in the value-based frequency distribution that occurs due to cornering.
  • FIG. 4 The alternative embodiment of cornering detection is indicated in FIG. 4 by the fact that the supply of both the speed variable vref and the transverse acceleration variable ay to block 407 is shown in broken lines.
  • the variables FStill and FKurve supplied to it determine whether there is a predetermined operating state of the vehicle in which the frequency distribution is determined in terms of value. The result of this evaluation is from the block 408 with the help of a size FKlass. If it is determined during the evaluation of the two variables FStill and FKurve that at least one of these two variables has the value TRUE, the frequency distribution by value is not determined. In other words: If the vehicle is almost at a standstill or if the vehicle is cornering, in particular a noticeable curve, the frequency distribution by value is not determined. In this case, the value FKlass is assigned the value FALSE, for example.
  • the frequency distribution is determined in terms of value.
  • the value FKlass is assigned the value TRUE, for example. Driving situations in which the vehicle is almost at a standstill or traversing a noticeable curve are suppressed because, as far as wheel slip is concerned, these are highly dynamic processes in which a determination of the coefficient of friction by means of evaluating a frequency distribution based on value does not result in reliable, ie provides usable results.
  • the result of the evaluation carried out in block 408 is fed to one of the three blocks 403 or 404 or 405. This is indicated in FIG. 4 by supplying the size FKlass to a dashed block in which the three blocks 403, 404 and 410 are combined. This makes it possible to influence the workflow of at least one of these three blocks, and thus to intervene in various ways in determining or evaluating the frequency distribution by value or to prevent it.
  • block 404 which has already been mentioned, a classification of the wheel slip sizes ⁇ ij fed to it is carried out, ie for the wheel slip sizes ⁇ ij their frequency distribution in terms of value is determined.
  • the result of this classification ie the value-based frequency distributions determined for the individual vehicle wheels, are supplied to block 405 already mentioned in the form of the variables ⁇ ktabij.
  • block 405 the value-based frequency distributions supplied to it for the individual vehicle wheels are evaluated, as a result of which a wheel friction value F ⁇ ji is determined for each of the vehicle wheels.
  • the result of this evaluation is fed to a block 411 to be described in the form of the wheel friction values F ⁇ ij for further processing.
  • the details of the work processes taking place in blocks 404, 405 and 411 are discussed in detail in connection with FIG. 5.
  • the size FEAAZ is fed to the dashed block, in which the three blocks 403, 404 and 405 are combined. If this variable indicates that the device for regulating the yaw angular velocity has brake intervention, the determination of the frequency distribution by value taking place in block 404 is hidden as long as said brake intervention continues. Alternatively, the evaluation taking place in block 405 can also be suspended.
  • a longitudinal acceleration variable ax describing the longitudinal acceleration of the vehicle is determined as a function of the speed variable vref supplied to it. This can be done, for example, by forming a time derivative or by suitable filtering.
  • the longitudinal acceleration quantity ax is fed to a block 410.
  • the power transmission is estimated in block 410.
  • the acceleration acting on the vehicle in particular the longitudinal acceleration acting on the vehicle, is related to the gravitational constant, as a result of which a measure of the coefficient of friction used in the respective driving situation can be determined. Concerning. Two embodiments are conceivable for the concrete realization of this estimate of the power transmission.
  • the supplied signal BLS are two different traveling states of the vehicle when estimating the braking case and the drive and free roll case.
  • the estimated value for the coefficient of friction for both the front axle and the rear axle results from the actual vehicle acceleration or deceleration, the gravitational constant g and a variable MUE_ROLL representing the rolling resistance value of an average asphalt track.
  • the estimated value for the coefficient of friction results, for example, from the relationship
  • the estimated value ⁇ PlausVA for the coefficient of friction corresponds to the value MUE_ROLL
  • the estimated value ⁇ PlausHA for the coefficient of friction on the rear axle corresponds according to a relationship
  • the longitudinal acceleration acting on the vehicle is set in relation to the gravitational constant g, whereby the factor a determines the contingent axle load distribution on the rear axle is taken into account.
  • the determination of the acceleration acting on the vehicle includes, for example, the vehicle acceleration resulting from engine intervention or vehicle deceleration due to engine intervention, as well as a deceleration component resulting from air resistance and / or rolling resistance.
  • the two variables ⁇ PlausVA and ⁇ PlausHA are fed to block 411.
  • an estimate of the power transmission is proposed, which is implemented with less computing effort.
  • the power transmission is estimated, for example, using the following quotient:
  • the size ⁇ Plaus represents the measure of the coefficient of friction used in the present driving situation.
  • the size ⁇ Plaus is fed from block 410 to block 411. Since this second embodiment is less precise than the first embodiment, the second embodiment is only mentioned here, while it will not be discussed in the further course. For this reason, the size ⁇ Plaus was not entered in FIG. 4.
  • ⁇ PlausVA and ⁇ PlausHA further sizes are supplied to block 411. These are the sizes FEAAZ and T outside already described in connection with FIG. 3, as well as the optionally supplied sizes F Re g s and F Sc h e ibenwischer •
  • the block 411 is supplied with the signal BLS.
  • the wheel friction variables F ⁇ ij are checked for plausibility with the aid of the variables mentioned above and the coefficient of friction F ⁇ is determined on the basis of the result obtained. During this plausibility check, further conditions can be taken into account, for example depending on the distance traveled by the vehicle or over the period of time that a predetermined state is present.
  • This method according to the invention begins with a step 501, which is followed by a step 502 in which different sizes are initialized.
  • slip class counters ⁇ ktabij to be described are initialized.
  • an intermediate variable F ⁇ _Plaus as well as the wheel friction variables F ⁇ ij and the coefficient of friction F ⁇ are initialized.
  • Both the intermediate variable F ⁇ _Plaus, the wheel friction variables F ⁇ ij and the coefficient of friction size F ⁇ are assigned values that indicate that no coefficient of friction information is currently available.
  • the coefficient of friction quantity F ⁇ contains both a component intended for block 310 and a component for block 311, these two components are also initialized in accordance with the explanations regarding the coefficient of friction quantity F ⁇ .
  • Step 502 is followed by step 503, in which the input variables to be supplied to block 301 are provided. Specifically, it is the wheel speed quantities nij, the yaw angular velocity quantity ⁇ ß , which optionally processed transverse acceleration variable ay, the signal BLS, the size FEAAZ, the size outsid n ⁇ and the two optional processed sizes F R eg e n or F Sche ibenwischer- It can be provided that the sizes T outside gen F Re and F Sch yew squeegees are not present in each pass of step 503 in aktualjone- re shape, but an updated value is provided, for example, only every tenth cycle. This is justified because, for example, the outside temperature changes only slowly.
  • step 504 various sizes are determined. These are the wheel speed variables vij determined in block 401, the speed variable vref determined in block 402, the quantity FStill determined in block 406, the variable FKurve determined in block 407 and the longitudinal acceleration variable ax determined in block 409.
  • step 505 the wheel slip sizes ⁇ ij are determined.
  • Step 505 is followed by step 506, in which it is determined whether the predetermined operating state of the vehicle is present.
  • step 506 the evaluation of the two variables FStill and FKurve described in connection with block 408 is carried out. If it is determined in step 506 that the vehicle is in the predefined operating state, in this case there is a drive at a minimum speed that is essentially straight, which is why the frequency distribution for the wheel slip variables ⁇ ij can be determined, then step 506, step 507 is executed. If, on the other hand, it is determined in step 506 that the specified operating state of the vehicle is not present, in this case the vehicle is almost at a standstill or the vehicle is making a curve, in particular a noticeable curve O 2004/083012
  • step 503 is carried out again after step 506.
  • the branching realized with the aid of step 506 ensures that as long as the predetermined operating state of the vehicle is not present, the determination of the frequency distribution by value is not carried out, the variables required for this, in particular the wheel slip variables ⁇ ij, are nevertheless provided.
  • step 505 can also follow step 506.
  • step 506 This would mean that the wheel slip variables ⁇ ij are only determined when the specified operating state of the vehicle is present.
  • the wheel slip variables ⁇ ij are determined both when the predetermined operating state of the vehicle is present and when it is not present.
  • the value-based frequency distribution of the wheel slip sizes ⁇ ij is determined.
  • a separate frequency distribution for the associated wheel slip variable ⁇ ij is determined for each of the vehicle wheels.
  • This slip range is used as the basis for determining the frequency distribution by value. It is divided into a predetermined number of slip classes, which advantageously have an equidistant width, ie an identical interval length. It is also conceivable to change the interval length of the individual slip class Sen to adapt to the expected structure of the frequency distribution in terms of value, and to allow narrower slippage classes in certain areas and broader in certain areas, as is indicated, for example, in the first embodiment.
  • slip classes are advantageously arranged symmetrically to the slip value “zero”.
  • the slip class which comprises the minimum slip value or immediately adjoins it is referred to as the first slip class.
  • the slip class which comprises the maximum slip value or adjoins it directly, is called the last hatching class.
  • steps 503 to 509 are to be carried out once per cycle time, which is, for example, in the order of 10 to 100 milliseconds.
  • wheel slip sizes ⁇ ij are available every 10 to 100 milliseconds and are sorted into the specified slip classes in order to determine the frequency distribution by value. If the specified operating state of the vehicle is present, the frequency distribution in terms of value is updated and evaluated in each cycle time.
  • the frequency distribution by value is advantageously determined for each of the vehicle wheels, which means that the corresponding wheel slip size is also sorted for each of the vehicle wheels.
  • the frequency distribution in terms of value is determined with the aid of the already mentioned slip class counter ⁇ ktabij, with a separate slip class counter being provided for each of the vehicle wheels.
  • the individual slip class counters are advantageously multidimensional sizes, so-called vector sizes, which contain a number of counter elements corresponding to the number of slip classes. point. Each individual counter element thus represents the frequency of occurrence of the value of the wheel slip size in the associated slip, while the slip class counter itself represents the value-based frequency distribution of the values of the wheel slip size in the entire slip range.
  • the counter element belonging to the first slip class is incremented. If it is established in this comparison that the value of the wheel slip size is greater than the maximum slip value, the counter element belonging to the last slip class is incremented.
  • the determination of the coefficient of friction according to the invention is a cyclical method. For this reason, when determining the individual occurrence frequencies and thus when determining the values
  • the frequency distribution must be standardized in a suitable manner, since the sum of all occurrences, ie the sum of the values of the counter elements of a slip class counter, must always be 100%.
  • step 508 wheel friction values F ⁇ ij are determined for the individual vehicle wheels.
  • the procedure on which this is based will be described with reference to FIGS. 6a, 6b and 6c, only one of the vehicle wheels being considered, but the procedure is identical for all vehicle wheels.
  • FIG. 6 a shows a value-based frequency distribution obtained by classifying the wheel slip variables determined for a vehicle wheel, which is characteristic of the wheel / road friction pairing.
  • the slip is plotted on the abscissa, starting with the first and ending with the last slip class.
  • the frequencies h of the individual slip classes which are also referred to as occurrence frequencies, are plotted on the ordinate.
  • the entire diagram shown in FIG. 6a represents the value-based frequency distribution of the associated wheel slip size determined for a vehicle wheel.
  • the determination of the wheel friction value F ⁇ ij proceeds as follows: First, the slip class with the greatest frequency, ie with the greatest frequency of occurrence of all hatches. Then, starting from the first slip class in the direction of the slip class with the greatest frequency of occurrence, that slip class gl is determined for which the first thing that applies is that its frequency of occurrence is greater than a predetermined value MUE_ FREQUENCY_MIN. The average slip value ⁇ gl is determined for this slip class gl.
  • the slip let g2 is determined for which the first thing that applies is that its frequency of occurrence is greater than the specified value MUE_ FREQUENCY_MIN.
  • the mean slip ⁇ g2 is also determined for this slip class g2.
  • the spread g of the wheel slip size is determined according to the following relationship:
  • the slip classes must have a minimum frequency of occurrence corresponding to the specified value MUE_H ⁇ UFIGkeit_MIN, so that these slip classes are taken into account when determining the slip spread, which is described by the spread g
  • the pattern of wheel slip size ie the value-based frequency distribution
  • the pattern of wheel slip size can be described or characterized and a decision made as to whether it is a grippy or slippery road surface.
  • the fact is that the frequency distribution in terms of value is narrow and high on a rough road, whereas it is wide and flat on a slippery road.
  • Figure 6b shows a first boundary line.
  • a coordinate system on the abscissa of which the scattering width g is plotted and on the ordinate of which the greatest frequency of occurrence is plotted, is a parabolic boundary line which is given by a function equation of the form
  • a wheel friction value F ⁇ j i can thus be determined by comparing the determined pair of values with the values specified by the boundary line for each of the vehicle wheels.
  • FIG. 6c An alternative to the border line shown in Figure 6b is shown in Figure 6c.
  • This is a boundary line defined in sections by several straight line segments.
  • the boundary line shown has four straight lines, which are specified by five support points. This is not meant to be a limitation. Of course, boundary lines with more or fewer support points can also be used. For the approximation of a curve shape predetermined by the interpolation points, functions other than line segments can also be used in order to connect the interpolation points to one another.
  • the second border line has the advantage over the first boundary line that the computational effort required for the evaluation is lower.
  • the division also applies that a non-slip road is to be assumed for value pairs that lie above the boundary line and a slippery road surface for value pairs that are below the boundary line.
  • the determination of the wheel friction values F ⁇ ij is dependent on a first variable, namely the spread g, which describes the spread, based on the wheel slip, of the value-based frequency distribution determined for the respective wheel slip variable ⁇ ij, and a second variable, that of the greatest frequency of occurrence of all corresponds to the slip classes belonging to the value-based frequency distribution.
  • the value of the wheel friction variables F ⁇ ij is ultimately determined by comparing the values of the first and second variables with pairs of values specified for grippy and slippery road conditions.
  • the procedure described above for determining the wheel friction values F ⁇ ij can advantageously be supplemented as follows, in this case this supplement should advantageously be used both in an evaluation based on the first boundary line and in an evaluation based on the second boundary line, be applicable:
  • the average slip value is determined for the slip class with the highest frequency of occurrence.
  • This mean slip value is taken into account when determining the wheel friction values F ⁇ ij, which means that in addition to the comparison of the pair of values, which is made up of the spread and the greatest frequency of occurrence, with the boundary line, another condition for evaluating whether a non-slip or there is a slippery road surface, is evaluated.
  • a non-slip road is recognized and a corresponding value is assigned to the wheel coefficient of friction F ⁇ ij if the determined pair of values lies above the limit line and the above average slip value is less than a threshold value that represents the wheel slip ratios when the traction control system is active, and the above average slip value is larger is a threshold value that represents the wheel slip ratios with active brake slip control. If all three of the above conditions are not met, the road is slippery and the wheel friction coefficient F ⁇ ij is assigned a corresponding value.
  • the value-based frequency distribution shown in FIG. 6a is again discussed.
  • the shape of this frequency distribution shows that these frequency distributions are arranged in a quasi-Gaussian distribution.
  • the size of the spread has the character of a standard deviation.
  • the method according to the invention is implemented in a control unit which has a powerful processor or computer, the standard distribution can alternatively be determined and evaluated instead of the spread.
  • an intermediate variable F ⁇ _Plaus is first determined by evaluating the quantities and signals supplied to block 411. This is done with the aid of various plausibility activity queries with which different subsets of the quantities and signals fed to block 411 are evaluated for plausibility checking. As already explained in connection with step 502, the intermediate variable F ⁇ _Plaus is assigned a value after the initialization, which indicates that there is currently no friction value information. As soon as one of the plausibility queries listed below is fulfilled, the intermediate variable F ⁇ _Plaus is assigned a value that represents a slippery road. If, on the other hand, none of the following plausibility queries are met, the intermediate variable F ⁇ _Plaus is assigned a value that represents a rough road.
  • plausibility queries can also be taken into account, for example in which the size of Fscheienischer is evaluated, or which is based on an evaluation with which it is determined whether a yaw rate control contained in the vehicle is active or whether a traction control system contained in the vehicle is active or whether a brake slip control contained in the vehicle is active.
  • the coefficient of friction F ⁇ is then determined depending on the value of the intermediate quantity F ⁇ _Plaus.
  • the following explanations are based on the assumption that the coefficient of friction F ⁇ , as already described in connection with FIG. 3, contains both a component intended for block 310 and a component for block 311. However, this should not be a limitation. The following explanations can also be applied to the case or transferred that a single coefficient of friction F ⁇ is used for the two blocks 310 and 311.
  • the component of the coefficient of friction size F ⁇ determined for the block 310 is assigned a value after the initialization, which indicates that no coefficient of friction information is currently available.
  • this component of the coefficient of friction F ⁇ is referred to below as the switchover component. If, immediately after this initialization state, the intermediate variable F ⁇ _Plaus has a value that represents a non-slip road, the switchover component is assigned a value that represents a non-slip road. If, after this value assignment, the intermediate variable F ⁇ _Plaus has a value that represents a slippery road, the switchover component is immediately assigned a value that represents a slippery road.
  • a distance counter is assigned a first distance value, for example in the order of 500 meters. If, immediately after the initialization state, the intermediate variable F ⁇ _Plaus has a value that represents a slippery road, the switchover component is immediately assigned a value that represents a slippery road. In this case too, the distance counter is assigned the first distance value. In general it can be stated: If the intermediate size F ⁇ _Plaus has a value that represents a slippery road, the value of friction F ⁇ is immediately assigned a value that also represents a slippery road.
  • the intermediate variable F ⁇ _Plaus has a value that represents a non-slip roadway
  • the changeover of the changeover Switching component to the value that represents the grippy road surface only carried out when the vehicle has covered a predetermined route that corresponds to the first route value and the value of the intermediate variable F ⁇ _Plaus has not changed during this route.
  • the route counter is assigned a second route value that is greater than the first route value.
  • the second distance counter is on the order of 1000 meters. This ensures that if the intermediate variable F ⁇ _Plaus again assumes the value that represents a rough road, the vehicle must travel a longer distance before the coefficient of friction F ⁇ is assigned the value that represents a rough road.
  • a change in the switchover component from a value that represents a rough road to a value that represents a slippery road takes place immediately, i.e. without the vehicle having to travel a predetermined distance and thus without a deliberately caused time delay.
  • the changeover component changes from a value that represents a slippery road to a value that represents a non-slip road with a time delay that depends on the distance traveled by the vehicle.
  • the distance traveled by the vehicle is of different lengths, and depends on whether it is a one-time or a repeated switching of the intermediate variable F ⁇ _Plaus between a value of a non-slip road represents and a value that represents a slippery road surface.
  • the component of the coefficient of friction size F ⁇ determined for the block 311 is assigned a value after the initialization, which indicates that no coefficient of friction information is currently available.
  • this component of the coefficient of friction F ⁇ is referred to below as the display component. If, immediately after this initialization state, the intermediate variable F ⁇ _Plaus has a value that represents a non-slip road, the display component is assigned a value that represents a non-slip road. If, after this value assignment, the intermediate variable F ⁇ _Plaus has a value that represents a slippery roadway, a value that represents a slippery roadway is only assigned to the display component after a predetermined period of time.
  • the intermediate variable F ⁇ _Plaus again has a value that corresponds to a non-slip road during this period, the value that represents a non-slip road remains for the coefficient of friction value F ⁇ .
  • the display component is switched from a value that represents a rough road to a value that represents a slippery road only if the intermediate variable F ⁇ _Plaus has the value that represents a slippery road for a predetermined period of time. If, immediately after the initialization state, the intermediate variable F ⁇ _Plaus has a value that represents a slippery road, then in this case too, a value that represents a slippery road is assigned to the display component only after a predetermined period of time.
  • the intermediate variable F ⁇ _Plaus again has a value during this period that corresponds to a rough road, the friction coefficient ß F ⁇ the value that represents a non-slip road.
  • the intermediate size F ⁇ _Plaus has a value that represents a non-slip road, the display component is only switched to the value that represents the non-slip road , if the vehicle has covered a route defined by a third route value, which is of the order of 1000 meters, and the value of the intermediate variable F ⁇ _Plaus has not changed during this route.
  • the intermediate variable F ⁇ _Plaus again has a value that corresponds to a slippery road surface
  • the distance counter which is used to check whether the vehicle has completed the route corresponding to the third route value.
  • the vehicle has to complete this route again. If it is determined during the predefined period of time that the intermediate variable F ⁇ _Plaus has changed its value and is again assuming the value that represents a non-slip road, then the already completed completion of the predefined route is continued.
  • a change in the display component from a value that represents a rough road to a value that represents a slippery road takes place only after a specified period of time has elapsed and therefore only with a time delay.
  • the size FEAAZ indicates that a brake intervention is being carried out to regulate the yaw rate, the output of the display component and thus the representation of the snowflake symbol is advantageously suppressed.
  • step 503 is carried out again.
  • wheel slip sizes ⁇ ij are determined at different times. For these wheel slip sizes ⁇ ij or for axially dependent slip sizes ⁇ v A * - ⁇ HA determined as a function of these wheel slip sizes ⁇ ij, their frequency distribution in terms of value is determined. The coefficient of friction F ⁇ is determined by evaluating this frequency distribution in terms of value.
  • the wheel slip variables can be permanently determined and their frequency distribution in terms of value is only determined and evaluated when the specified operating state of the vehicle is present, as can be seen, for example, from FIG. 5 belonging to the second embodiment.
  • This procedure is particularly useful when the wheel slip sizes are provided, for example, by a slip control system in the vehicle.
  • the wheel slip sizes can only be determined when the predetermined operating state of the vehicle is present, as can be seen, for example, from FIG. 2 belonging to the first embodiment. It should be noted that the wheel slip size can also be determined permanently in the first embodiment.
  • the first and second embodiments differ as follows: With the method according to the invention of the first embodiment, the determination and evaluation of the frequency distribution in terms of value is limited in time. Both are carried out within a defined time window. In addition, the frequency distribution by value is only determined when the predetermined operating state of the vehicle is present. This determination is terminated if the predefined operating state of the vehicle is no longer present during an ongoing determination. In the method according to the invention of the second embodiment, on the other hand, the determination and evaluation of the frequency distribution by value is time-unlimited, ie continuous carried out slowly. There is no time window. If the specified operating state of the vehicle is present, the frequency distribution in terms of value is determined in the form of an update or update. If the operating state of the vehicle is no longer present during the ongoing determination of the frequency distribution by value, the determination of the frequency distribution is suspended or interrupted but not ended. It is continued again after the operating state has been restored.

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Regulating Braking Force (AREA)
  • Navigation (AREA)

Abstract

La présente invention concerne un procédé qui sert à déterminer une grandeur de frottement (Fµ) qui représente les frottements qui agissent entre une chaussée et des pneumatiques de véhicule. A cet effet, est déterminée pour au moins une roue du véhicule, une grandeur de glissement de roue (?ij) qui décrit le glissement de roue au niveau de cette roue. La grandeur de frottement (Fµ) est déterminée en fonction de cette grandeur de glissement de roue (?ij). A cet effet, des grandeurs de glissement de roue (?ij) sont déterminées à différents instants, en particulier successifs, au cours d'un état de fonctionnement prédéterminé du véhicule. Pour ces grandeurs de glissements de roue (?ij) ou pour des grandeurs de glissement par essieu (?VA et ?HA) déterminés en fonction de ces grandeurs de glissement de roue (?ij), leur distribution de fréquence par valeurs est déterminée. La grandeur de frottement (Fµ) est déterminée par évaluation de cette répartition de fréquence par valeurs.
EP04721878A 2003-03-21 2004-03-19 Procede et dispositif pour determiner une grandeur de frottement representant les frottements qui agissent entre une chaussee et des pneumatiques de vehicule Withdrawn EP1628862A1 (fr)

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DE10312787 2003-03-21
PCT/EP2004/002916 WO2004083012A1 (fr) 2003-03-21 2004-03-19 Procede et dispositif pour determiner une grandeur de frottement representant les frottements qui agissent entre une chaussee et des pneumatiques de vehicule

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Families Citing this family (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7267148B2 (en) * 1999-08-10 2007-09-11 Michelin Recherche Et Technique S.A. Measurement of adherence between a vehicle wheel and the roadway
DE102004021367A1 (de) * 2004-04-30 2005-11-17 Robert Bosch Gmbh Verfahren und Vorrichtung zum Begrenzen der Geschwindigkeit eines Fahrzeugs
US8335625B2 (en) * 2005-09-06 2012-12-18 Nissan Motor Co., Ltd. Slip control device and method for a vehicle
WO2008092003A2 (fr) * 2007-01-25 2008-07-31 Honda Motor Co., Ltd. Commande de systèmes de véhicule pour améliorer la stabilité
JP2008197819A (ja) * 2007-02-09 2008-08-28 Sumitomo Electric Ind Ltd 識別装置及び識別方法
US20080228329A1 (en) * 2007-03-13 2008-09-18 Honeywell International Inc. Methods and systems for friction detection and slippage control
WO2009113001A1 (fr) 2008-03-13 2009-09-17 Philips Intellectual Property & Standards Gmbh Système de capteur, système de contrôle de véhicule et système d'information du conducteur de sécurité de véhicule
JP5458584B2 (ja) * 2009-01-29 2014-04-02 日産自動車株式会社 情報提供装置及び情報提供方法
DE102011015509A1 (de) * 2010-06-30 2012-01-05 Wabco Gmbh Verfahren und Vorrichtung zur Steuerung zumindest eines Fahrerassistenzsystems eines Fahrzeuges und damit ausgestattetes Fahrzeug
DE102010063017A1 (de) * 2010-12-14 2012-06-14 Robert Bosch Gmbh Verfahren in einem Fahrerassistenzsystem zur Erkennung von Nässe auf einer Fahrbahn
US9550480B2 (en) * 2011-10-21 2017-01-24 Autoliv Nissin Brake Systems Japan Co., Ltd. Vehicle brake hydraulic pressure control apparatus and road surface friction coefficient estimating device
US9387859B2 (en) * 2012-09-20 2016-07-12 Pioneer Corporation Slip ratio estimation device and slip ratio estimation method
DE102016203545A1 (de) * 2016-03-03 2017-09-07 Continental Teves Ag & Co. Ohg Verfahren zur Bestimmung von Fahrbahngriffigkeitsklassen
DE102016211728A1 (de) * 2016-06-29 2018-01-04 Trw Automotive U.S. Llc Reibwertschätzer
US10427645B2 (en) * 2016-10-06 2019-10-01 Ford Global Technologies, Llc Multi-sensor precipitation-classification apparatus and method
EP3562702A1 (fr) 2016-12-30 2019-11-06 Elaphe Propulsion Technologies Ltd. Agencement permettant de déterminer un couple maximal admissible
DE102017221050A1 (de) * 2017-11-24 2019-05-29 Robert Bosch Gmbh Verfahren und Vorrichtung zum Detektieren von Anomalien in Signaldaten für eine Reibwertschätzung für ein Fahrzeug
EP3587201B1 (fr) * 2018-06-21 2022-10-12 Volvo Car Corporation Procédé et système de détermination du frottement pneu-route dans un véhicule
JP7306943B2 (ja) * 2019-09-30 2023-07-11 Ｔｏｙｏ Ｔｉｒｅ株式会社 車両走行条件評価方法及びシステム

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4435448B4 (de) * 1993-10-13 2007-10-11 Volkswagen Ag Verfahren zur permanenten Ermittlung des Fahrbahnreibwerts
US5774821A (en) * 1994-11-25 1998-06-30 Itt Automotive Europe Gmbh System for driving stability control
EP0788955B1 (fr) * 1995-09-19 2003-11-26 Japan Electronics Industry, Ltd. Méthode de commande pour des systèmes d'antiblocage
DE19754162A1 (de) * 1997-09-19 1999-03-25 Itt Mfg Enterprises Inc Verfahren und Anordnung zur systematischen Bewertung des dynamischen Verhaltens eines Regelsystems
DE19911525C1 (de) * 1999-03-16 2000-09-28 Bosch Gmbh Robert Verfahren und Vorrichtung zum Ermitteln einer Referenzgröße für die Radgeschwindigkeiten eines Fahrzeugs
DE10126459C1 (de) * 2001-05-31 2003-01-16 Daimler Chrysler Ag System und Verfahren zum Ermitteln von Fahrbahnreibwerten im Bereich eines Fahrzeugs
JP4114044B2 (ja) * 2001-07-17 2008-07-09 トヨタ自動車株式会社 タイヤ作用力検出装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2004083012A1 *

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US20070016354A1 (en) 2007-01-18
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JP2006521237A (ja) 2006-09-21

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