JPH06331464A - System to determine adhesion coefficient of vehicle - Google Patents

Abstract

PURPOSE: To determine the precise potential of the adhesion and its momentary value with a simple configuration by use of a known measured value by using at least one fuzzy logic from variables of vehicle acceleration, wheel acceleration and control pressure. CONSTITUTION: A fuzzy logic part 100 determines and outputs the potential μPot of coefficient of traction by use of corrected vehicle acceleration aX', corrected wheel acceleration aR', and braking pressure (p) which are inputs. Since some fuzzy rules have different results depending on whether the value of the potentials μPot of the adhesion coefficient is small or large, the fuzzy rule is weighted according to the area where the value of the potential μPot of the adhesion coefficient is just present. The weighting is performed by use of a classification block 101 and a correction block 102 through the control input of the fuzzy logic part 100. The classification block 101 detects whether the potential μPot of the adhesion coefficient is small, middle or large, and transmits the result to the correction block 102.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for determining the sticking coefficient of a vehicle.

[0002]

2. Description of the Related Art A system of this type for determining the adhesion coefficient of a vehicle is DE35353543A1 (= US479453).
Known from 8). The publication describes a method of continuously obtaining an adhesion coefficient between a wheel being braked and a running surface of the wheel. The sticking coefficient is determined from braking pressure and wheel speed using an identification algorithm through a mathematical model.

DE 424047A1 (Japanese Patent Laid-Open No. 6-28)
No. 037) describes a method and apparatus for positioning an actuator using fuzzy logic. The same publication also describes details of the fuzzy operation.

[0004]

The object of the present invention is to provide a system which makes it possible to determine the adhesion coefficient of a vehicle from an already known measured quantity.

[0005]

In order to solve this problem, according to the invention, the maximum possible value of the adhesion coefficient is determined from at least one fuzzy logic from the variables of vehicle acceleration, wheel acceleration and braking pressure. The configuration for obtaining the potential as is adopted.

Further, according to the present invention, a configuration is also adopted in which the instantaneous value of the adhesion coefficient is obtained from at least one fuzzy logic from the variables of the vehicle acceleration and the wheel acceleration.

[0007]

The present invention has the advantage that the adhesion coefficient can be obtained with relatively little effort. Particularly effective is the use of fuzzy logic (inference) in the system of the present invention, which eliminates the need for an exact mathematical model. Another advantage is that in order to carry out the method according to the invention usually only sensors already provided in the vehicle in the first place are required.

A relatively small number of membership functions can be obtained by adjusting the membership function of the fuzzy logic when obtaining the potential of the adhesion coefficient, or by selecting the fuzzy rule when obtaining the instantaneous value of the adhesion coefficient. It becomes possible to obtain great accuracy by using fuzzy rules.

Through correcting the vehicle acceleration and the wheel acceleration with the adaptation coefficient, the membership function and the fuzzy rule when the condition is equal on the right side and the left side of the vehicle are compared with the case where the road surface is not homogeneous. Can also be used.

In the preferred embodiment, the fuzzy logic membership function is adjusted according to the determined adhesion coefficient potential, vehicle speed and braking pressure.

Also, a set of fuzzy rules for determining the instantaneous value of the adhesion coefficient according to vehicle acceleration, wheel acceleration and braking pressure is selected.

When obtaining the potential of the adhesion coefficient, the characteristic value is calculated according to the difference in the potential of the adhesion coefficient between the left side and the right side of the vehicle, the time change of the difference in the wheel acceleration between the left side and the right side of the vehicle, the braking pressure and the variable of the vehicle speed. The correction coefficient obtained from the map is multiplied by the vehicle acceleration. In that case, the difference in the potential of the adhesion coefficient between the left side and the right side of the vehicle is obtained using the fuzzy logic from the difference in the wheel acceleration between the left side and the right side of the vehicle, the time change of the difference, and the variable of the vehicle speed.

On the other hand, the wheel acceleration is multiplied by the correction coefficient obtained by using the characteristic line according to the vehicle speed.

The present invention may be used in connection with antilock braking systems, traction control systems or inter-vehicle distance control systems.

[0015]

[Examples] Next, two examples for obtaining an adhesion coefficient (coefficient of static friction) between a wheel and a road surface will be described. The first embodiment is used to determine the potential μPot of the sticking coefficient, ie the sticking coefficient which is maximally possible under the given conditions, the second embodiment acts on the instantaneous value of the sticking coefficient, ie at that moment. It is used to calculate the adhesion coefficient.

FIG. 1 shows the adhesion coefficient potential μPot.
A block circuit diagram of an embodiment for determining is shown. The block circuit diagram is divided into two functional groups.

In the first functional group, the same condition prevails on the right side and the left side of the vehicle, that is, on the assumption that the adhesion coefficients on the right side and the left side of the vehicle are equal, the potential μPot of the adhesion coefficient is obtained. Used for. This is the case, for example, when braking or acceleration is performed during straight running on a homogeneous road surface. The first functional group is a fuzzy logic (inference) unit 100 and a classification block 101.
And a modification block 102.

The addition of the second functional group makes it possible to use the system according to the invention even when different adhesion factors occur on the left and right sides of the vehicle, for example due to uneven road surfaces. In this context, the second functional group regulates some of the input signals of the first functional group, in particular the signal aX relating to vehicle acceleration and the signal aR relating to wheel acceleration. The second functional group is the calculation block 104 and the fuzzy logic unit 1.
06, a characteristic value map 108 for obtaining the correction coefficient c1 of the vehicle acceleration aX, a connection point 110, a characteristic value map 112 for obtaining the correction coefficient c2 of the wheel acceleration aR, and a connection point 114.

The individual elements of the first functional group are connected as follows.

The fuzzy logic unit 100 has four inputs and one output. The first input is connected to the output of the connection point 110, and the second input is connected to the output of the connection point 114 that belongs to the second functional group like the connection point 110. The corrected input signal of the vehicle acceleration aX 'is applied to the first input of the fuzzy logic unit 100, and the corrected input signal of the wheel acceleration aR' (for the left or right vehicle) is applied to the second input. It A signal of the braking pressure p is applied to the third input. The fourth input is the control input, which is connected to the output of the correction block 102. The membership function used in the fuzzy logic 100 can be adjusted via the control input. Correction block 10
2 has three inputs. A signal of the braking pressure p is applied to the first input, and the vehicle speed v is applied to the second input.
The X signal is applied and the third input is the classification block 101.
Connected with the output of. The classification block 101 has two inputs, a vehicle speed vX signal is applied to a first input, and a second input is connected to an output of the fuzzy logic unit 100.

The individual elements of the second functional group are connected as follows.

The calculation block 104 has two inputs,
The signal of the wheel acceleration aRl on the left side of the vehicle or the signal of the wheel acceleration aRr on the right side of the vehicle is applied to the input. Furthermore, the calculation block 104 has two outputs, the first output of which is the wheel acceleration aRl on the left and right sides of the vehicle.
And aRr is output as a signal of a difference daR, and the second output is output as a time change (time differential) ddaR of the difference daR. The first output is connected to the first input of the fuzzy logic unit 106, and the second output is connected to the second input of the fuzzy logic unit 106 and the first input of the characteristic value map 108. A signal of the vehicle speed vX is applied to the third input of the fuzzy logic unit 106. Fuzzy logic unit 106
Output is the difference dμPot of the potential μPot of the adhesion coefficient between the left side and the right side of the vehicle, and the characteristic value map 1
08 second input. Characteristic value map 10
The signal of the braking pressure p is applied to the third input of
The signal of the vehicle speed vX is applied to the input of.

The output of the characteristic value map 108 is the connection point 110.
Of the vehicle acceleration aX is supplied to the second input of the connection point. A signal of the vehicle speed vX is applied to the input of the characteristic value map 112. The output of the characteristic value map 112 is connected to the first input of the connecting point 114, and the signal of the wheel acceleration aR (on the left or right side of the vehicle) is applied to the second input of the connecting point.

The potential μPot of the adhesion coefficient is obtained as follows: The fuzzy logic unit 100 uses a fuzzy operation from the corrected vehicle acceleration aX ', the corrected wheel acceleration aR' and the braking pressure p which are the input quantities. Then, the value of the potential μPot of the adhesion coefficient is obtained, and this value is output. The fuzzy logic unit 100 stores a series of fuzzy rules, and the vehicle acceleration aX ′ corrected by each fuzzy rule and the corrected wheel acceleration a
The ambiguous information of the adhesion coefficient potential μPot is associated with the combination of ambiguous information of R ′ and the braking pressure p. Ambiguous information is represented by membership functions, as is common in fuzzy processing. Fuzzy rules and membership functions are empirically required during the development or setting stage. In that case,
It is assumed that the left and right sides of the vehicle are under the same conditions.

It has been shown that some fuzzy rules give good results when the value of the adhesion coefficient potential μPot is small, and that other fuzzy rules give good results at medium or large values. ing.
Therefore, it is proposed to weight the fuzzy rules according to the region in which the value of the potential μPot of the adhesion coefficient lies. In the described embodiment, the weighting is done using the classification block 101 and the modification block 102 via the control inputs of the fuzzy logic. The classification block 101 detects whether the adhesion coefficient potential μPot is small, medium, or large, and sends the result to the correction block 102. The subdivision into small, medium, and large classification means, for example, the adhesion coefficient potential μPo.
This is done by comparing with an appropriate threshold of t.
The vehicle speed vX is taken into account when subdividing.

The correction block 102 is supplied with the braking pressure p as another input amount, and determines the coefficient f1 for the membership function of the vehicle acceleration and the coefficient f2 for the membership function of the wheel acceleration from the two input signals, respectively. Both of these coefficients f1 and f2 are supplied to the fuzzy logic unit 100 via a control input.
And applied to the membership function described above.
In this way, the membership function is scaled (the values of the membership functions of vehicle acceleration and wheel acceleration are multiplied by the coefficients f1 and f2, thereby increasing or decreasing the membership function). That is, the effectiveness of the membership function varies depending on the coefficient. This causes the fuzzy rules applied to the membership function to be correspondingly weighted. That is, since a fuzzy rule uses a membership function, the influence of one fuzzy rule on another rule is larger or smaller depending on the membership function used for the fuzzy rule. Coefficients f1 and f in the correction block 102
The determination of 2 is performed, for example, by reading from the characteristic value map in which the coefficients f1 and f2 are stored according to the braking pressure p and the vehicle speed vX.

In order to be able to refer to the rules and membership functions stored in the fuzzy logic unit 100 in order to obtain the potential μPot of the adhesion coefficient even when the conditions of the left half and the right half of the vehicle are different. Before the signals of the vehicle acceleration aX and the wheel acceleration aR are supplied to the fuzzy logic unit 100, the respective signals are multiplied at the connection points 110 to 114 by the correction factors c1 and c2. The correction coefficient c1 is read from the characteristic value map 108 and supplied to the connection point 110. The correction coefficient c2 is read from the characteristic line 112 and supplied to the connection point 114.

The characteristic value of the map 108 is particularly related to the potential difference dμPot of the adhesion coefficient between the left side and the right side of the vehicle. The difference dμPot is the difference d between the wheel accelerations aRl and aRr between the left side and the right side of the vehicle by the fuzzy logic unit 106.
It is obtained from the time change daR of aR and the difference daR. In principle, the fuzzy logic unit 106 is the fuzzy logic unit 1.
Works like 00, but of course other fuzzy rules and membership functions are used.

The difference daR between the wheel accelerations aRl and aRr between the left side and the right side of the vehicle and the time change ddaR of the difference daR are calculated by the calculation block 104 from the wheel acceleration aR on the left side of the vehicle.
1 and the wheel acceleration aRr on the right side of the vehicle. The wheel accelerations aRl and aRr can be obtained, for example, by using an acceleration sensor or from the time change (time derivative) of the wheel rotation speed.

The braking pressure p can be detected by a braking pressure sensor provided in the braking device.

The values of the potential μPot of the adhesion coefficient obtained by the system of the present invention are the connection points 11 respectively.
4 is the wheel acceleration aR on the left side of the vehicle or the wheel acceleration aR on the right side of the vehicle.
It is a value related to the left or right side of the vehicle depending on whether it represents r. Therefore, in order to obtain the potential of the adhesion coefficient on both sides of the vehicle, the system shown in FIG. 1 must be provided in duplicate, or the wheel accelerations on the left and right sides of the vehicle must be alternately supplied to the connection point 114. .

Potential of the obtained adhesion coefficient μPo
The value of t is fed, for example, to a device that controls the inter-vehicle distance and is further processed there.

FIG. 2 is a block circuit diagram for obtaining the instantaneous value μMom of the adhesion coefficient. As with the embodiment shown in FIG. 1, the block circuit diagram shown in FIG. 2 is also divided into two functional groups, in which case the second functional group has already been described and is shown in FIG. It is exactly the same as the second functional group.

The first functional group of FIG. 2 is constructed similarly to the functional group of FIG. It is composed of a fuzzy logic unit 200 and a rule selection unit 202. The fuzzy logic unit 200 calculates the instantaneous value μMom of the adhesion coefficient from the corrected vehicle acceleration aX ′ applied to the first input and the corrected wheel acceleration aR ′ applied to the second input, and the calculated instantaneous value Output the value μ Mom. Through the control inputs of the fuzzy logic unit 200, it is possible to determine which fuzzy rule to apply. The control input is connected to the output of the rule selection unit 202, which outputs the corrected vehicle acceleration a applied to its three inputs.
A fuzzy rule is selected according to X ', the corrected wheel acceleration aR' and the braking pressure p.

The instantaneous value of the adhesion coefficient obtained using the system shown in FIG. 2 is supplied to, for example, an antilock brake system (ABS) or a traction control system (driving slip reduction system). In order to obtain the instantaneous values μMom of the adhesion coefficient on the left side and the right side of the vehicle, in the embodiment shown in FIG. 2 as well as in the embodiment shown in FIG. 1, another device shown in FIG. If necessary, the vehicle left wheel acceleration signal aRl and the vehicle right wheel acceleration signal aRr are alternately supplied to the connection point 114.

[0036]

As is apparent from the above description, according to the present invention, it is possible to realize a simple structure using a measurement amount already known in the system for determining the adhesion coefficient of a vehicle.
Moreover, the potential of the adhesion coefficient and its instantaneous value can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment for obtaining a potential μPot of an adhesion coefficient.

FIG. 2 is a block diagram of an embodiment for obtaining an instantaneous value μMom of an adhesion coefficient.

[Explanation of symbols]

 100 Fuzzy Logic Unit 101 Classification Block 102 Correction Block 104 Calculation Block 106 Fuzzy Logic Unit 108 Characteristic Value Map 112 Characteristic Value Map (Characteristic Line) 200 Fuzzy Logic Unit 202 Rule Selection Unit

 ─────────────────────────────────────────────────── ————————————————————————————————————————————————————— Inventor Joachim Angsenberger 52223 Germany Stallberg Breiningerberg 62

Claims (8)

[Claims] 1. Vehicle acceleration (aX), wheel acceleration (a
R) and braking pressure (p) variables to determine the potential (μPot) as the maximum possible value of the adhesion coefficient using at least one fuzzy logic (100) to determine the adhesion coefficient of the vehicle System. 2. The potential of the obtained adhesion coefficient (μ
System according to claim 1, characterized in that the membership function of the fuzzy logic (100) is adjusted according to Pot), vehicle speed (vX) and braking pressure (p). 3. At least one fuzzy logic (2) from the variables of vehicle acceleration (aX) and wheel acceleration (aR).
00) is used to determine an instantaneous value (μMom) of the adhesion coefficient, which is a system for determining the adhesion coefficient of a vehicle. 4. Vehicle acceleration (aX), wheel acceleration (a)
4. A system according to claim 3, characterized in that a set of fuzzy rules for determining the instantaneous value of the adhesion coefficient ([mu] Mom) according to R) and the braking pressure (p) is selected. 5. A vehicle acceleration (aX) is a time difference (ddaR) of a difference in potential of adhesion coefficient (dμPot) between a left side and a right side of a vehicle and a difference in wheel acceleration (aRl, aRr) between a left side and a right side of the vehicle. ), The braking pressure (p) and the vehicle speed (vX) are combined with a correction coefficient (c1) obtained from the characteristic value map (108). The system described in. 6. The potential difference (dμPot) between the left side and the right side of the vehicle is the difference (daR) between the wheel accelerations (aRl, aRr) between the left side and the right side of the vehicle, and the change over time (ddaR). ) And a variable of vehicle speed (vX) using fuzzy logic (106). 7. The wheel acceleration (aR) is the vehicle speed (v).
System according to any one of claims 1 to 6, characterized in that it is combined with a correction factor (c2) determined using a characteristic line (112) according to X). 8. The system according to claim 1, wherein the system is used in connection with an anti-lock braking system, a traction control system or an inter-vehicle distance control system.