Method for determining the course of a land vehicle by comparing signals from wheel sensors with signals of a magnetic sensor

In a method for determining the location of a land vehicle wherein the driving distance and course changes are derived from wheel pulses generated by sensors in the course of the revolution of the wheels of a vehicle axle by respectively a preset angle, the course changes derived from the wheel pulses are compared with comparison course changes which are obtained independently of the wheel pulses. Correction values are derived from the result of the comparison. The comparison course changes are preferably detected with the aid of a magnetic sensor (compass).

BACKGROUND OF THE INVENTION 
The invention is based on a method with the species of the dead-reckoning 
navigation, corrected by magnetic sensor and odometer signals. 
In known location determination systems for vehicles, information regarding 
the respectively driven distance is derived from the revolution of the 
wheels, while in some systems a magnetic sensor detects the course and in 
other systems a measurement of the difference of the wheel revolutions 
detects the change of the course. Both methods have disadvantages. The 
magnetic sensor often experiences interference--for example because of 
steel structures close to the path of the vehicle or because of changes of 
the magnetic properties of the vehicle. Since errors in detecting path 
changes with the aid of wheel pulses accumulate in the course of driving 
the vehicle, large inaccuracies result with increasing length of the 
drive. But deviations of the course changes determined with the aid of the 
wheel pulses from the actual values occur for many reasons. For example, 
the diameters of the two wheels do not agree, or the effective axle width 
changes with the degree of turning and the load on the vehicle. 
Accordingly, differences in the wheel pulses already occur with 
straight-ahead driving, and the deviations during cornering are added. 
A further difficulty in connection with the known systems lies in that the 
wheel sensors employed deliver a limited number of pulses per wheel 
revolution for reasons of cost and because of the severe operating 
conditions in the vehicle. It is therefore advantageous to use the sensors 
of an anti-locking system, for example, which only supply 96 pulses per 
wheel revolution. 
SUMMARY OF THE INVENTION 
It is the object of the invention to recite a method for determining the 
location of a land vehicle, wherein the evaluation of the wheel pulses 
generated by the revolution of the wheels on a vehicle axle is improved 
over the known systems. It is intended in particular to correct the 
deviations on account of the tires, the design of the axle and the 
operational status of the vehicle. This object is to be attained with as 
small as possible an effort of time and calculations. 
The method has the advantage that the inaccuracies present during 
evaluation of the wheel pulses are corrected. In this case correction 
takes place adaptively. Changes occurring during the life of the vehicle 
or the tires are taken into consideration without readjustments needing to 
be made by the user or in the shop. 
A further development of the invention consists in that the course changes 
and the comparison course changes are observed over an observation course 
over which the vehicle is driven, which is divided into a number of 
observation windows and the length of which is a function of speed, and 
that over an observation course started for a defined purpose (recognition 
of straight-ahead driving, recognition of the sign of a course change, 
evaluation of cornering) observation is terminated and a new observation 
course is started if it becomes apparent after summation within an 
observation window that the purpose is no longer served. This further 
development allows extensive use of straight and curved paths for the 
respective observation. 
By means of another further development it is provided that during 
comparison course changes over one observation course which is small in 
respect to a preset value, a correction value is derived from the 
difference in the number of wheel pulses of both wheels, and that the 
correction value is stored and is used for the correction of the number of 
wheel pulses of at least one of the wheels. 
This further improvement makes an effective correction of the wheel pulses 
during straight-ahead driving possible. In particular, errors are being 
corrected which are caused by different sizes of the circumference of the 
wheels. This correction is particularly important, because deviations from 
the straight-ahead driving in respect to actual straight-ahead driving add 
up to considerable distance and position errors over extended driving 
distances. In addition, further evaluations require wheels of the same 
size, so that other values, which will be described later, are also 
affected by this error. 
Another further development of the invention consists in that during course 
changes over an observation course which are greater than a preset minimum 
value, the difference between the course changes and the comparison course 
changes is calculated, that stored correction factors are increased, if 
the course changes are less than the comparison course changes, that the 
correction factors are reduced if the course changes are greater than the 
comparison course changes, that the correction factors for different 
driving operations changed in this manner and respectively determined by a 
speed range and a course change range are stored and that the derived 
course change during the respective driving operation is weighted with the 
changed, stored correction factor. 
A quite exact determination of course changes is possible with the help of 
this further development although, besides the change of the effective 
axle width, during cornering numerous effects falsify the values obtained 
from the evaluation of the wheel pulses. 
In an advantageous embodiment of this further development, the correction 
factors for both signs of the course changes are separately determined and 
stored. Actually, with sufficiently symmetrical behavior of the vehicle a 
mutual determination and memorization of the correction factors for course 
changes which are of the same value, but are in a different direction, is 
possible.

DETAILED DESCRIPTION 
In the arrangement in accordance with FIG. 1, disks 1, 2 with a magnetic 
division, which is respectively scanned by a sensor 3, 4, are assigned to 
the non-driven wheels of a vehicle for generating the wheel pulses. Such 
devices are already present in vehicles with an anti-locking system and 
generate 96 pulses per wheel revolution. In the exemplary embodiment 
illustrated in FIG. 1, the wheel pulses L of the sensor 3 associated with 
the left wheel are supplied in the form of path pulses to a navigation 
device 5 which forms vectors from the wheel pulses L and the course 
information, which are added in accordance with the method for composite 
locating. Since navigation devices of this type are known, a detailed 
description in connection with the present invention is unnecessary. 
However, it should be pointed out that with locating devices for land 
vehicles, assistance is frequently provided by means of stored road maps. 
In the course of this checks are made, for example, whether the respective 
location is still on a road and the locating result is correspondingly 
corrected. This is also possible in connection with location information 
obtained by means of the method of the invention; but the invention is not 
limited to such systems. 
In addition to the distance traveled, the course change of the vehicle 
d.alpha./dt is derived from the wheel pulses L, R generated by the sensors 
3, 4 which, in respect to the digital signal processing, will be expressed 
in what follows as course change delta .alpha. between two scanning 
points. Because the wheel circumferences are different, the evaluation of 
the wheel pulses while the vehicle is moving straight ahead results in a 
circle with the radius r=B/(U/(U-delta U)-1). Here, r is the radius of the 
circle, B the axle width of the vehicle, U the circumference of one of the 
wheels and delta U the circumference error between the wheels. A 
circumference error of 1 mm results in a radius of 2.7 km, which results 
in an angular deviation of 1.degree. after a travel distance of 47 m. Even 
with delta U=0.3 mm, the radius r=9 km, which corresponds to an error of 
1.degree. in 157 m. Therefore the wheel pulses L and R at 6 are corrected 
prior to calculating the angle or the course change in such a way that 
their average frequency during straight-ahead driving is the same. For 
this purpose the correcting unit 6 is controlled by an observation unit 7 
as described hereinafter. 
The smaller wheel which rolls over the same distance as a larger wheel 
supplies too many pulses. The pulses of the smaller wheel are added 
together by means of measuring intervals. After a pulse number to be 
determined, respectively one pulse is subtracted from the pulses of the 
smaller wheel. The pulse number IZ is IZ=U.sub.k1 /(U.sub.gr -U.sub.k1). 
In a preferred embodiment, the wheel circumferences are determined in the 
course of calibration. The wheel circumferences are then known with an 
accuracy of 0.1 mm, for example. Through observation of straight path 
sections, a wheel circumference is suitably changed by 0.1 mm, for 
example, if necessary. IZ can again be determined with these new wheel 
circumferences. This modified or adapted wheel circumference, too, is 
processed as a function of speed. For this reason it is necessary to 
redefine IZ when the speed range is changed. The uncorrected course 
changes of the wheels are used for this observation in order to disconnect 
the adaptation processes. 
A magnetic sensor 8 is used to determine whether there is a straight path, 
the output signal of which is also supplied to the observation unit 7. 
Although a magnetic sensor provides very undependable results particularly 
in a vehicle, it is however possible through steps described in connection 
with FIGS. 3 to 5 to carry out the formation of correction values, for 
example the pulse number IZ, in the case where the signal M is 
substantially undisturbed. 
The corrected wheel pulses LC and RC are supplied by the correction device 
6 to a device 9 for forming a course change signal delta .alpha.. However, 
this value still is subject to different errors, which are not removed by 
only correcting the wheel pulses. Therefore another correction device 10 
is provided, which is also controlled by the observation unit 7. This 
correction depends on the steering angle, i.e. the course change signal 
itself. In addition, the correction is made as a function of speed. For 
this reason the wheel pulses L are also supplied to the correction device 
10. The output signals of the correction device 10 are supplied to the 
navigation device 5 and the observation device 7. 
Only some essentials of the method of the invention will be described by 
means of the arrangement illustrated in FIG. 1. The method of the 
invention can comprise the following detailed steps: 
correction of the pulses of the smaller wheel after determination of the 
circumferential difference between the wheels, 
determination of the direction of a course change, 
correction of the calculated course changes. 
In the course of executing these method steps, measured values (wheel 
pulses, signal of the magnetic sensor) are observed over observation 
courses and are evaluated. If the evaluation shows that there is a driving 
situation which is suitable for forming a correction value, the respective 
correction value is formed from the measured values and stored. Then the 
stored correction values are used for correction until the driving 
situation permits the formation of another correction value for the same 
type of correction. 
The present correction value is suitably not only simply replaced by a 
further correction value. On the one hand, erratic changes of the 
correction values are not expected, so that such changes lead to the 
conclusion that there were errors in detection. On the other hand, the 
above mentioned method steps form a plurality of control circuits 
intermeshed with each other which, for reason of stability, should have 
sufficient inertia. Thus, suitable averaging between the present and the 
further correction values is proper for attaining low-pass behavior. 
The length of the observation courses is adapted to the requirements of the 
several method steps and depends on the vehicle speed. The importance of 
the dependence on speed of the length is explained by means of the 
following example. An observation course for determining straight-ahead 
driving, such as is required for determining the circumferential 
correction, should be as long as possible for attaining a high degree of 
accuracy. But as a rule, such long straight distances regularly only occur 
on superhighways, where driving is at high speeds. At low speeds which are 
almost exclusively used in city traffic, correction values would 
practically never be obtained with long observation courses. However, 
because of their dependence on speed, the observation courses in city 
traffic become so short that correction values can be determined over 
sufficiently short time periods. 
FIG. 2 shows an exemplary embodiment of an arrangement for executing the 
method of the invention in which, because of a high degree of integration, 
only a few components are required. The functions of the devices 6, 7, 9 
and 10 shown in FIG. 1 are performed by a microcomputer 21 in the 
arrangement in accordance with FIG. 2. A suitable display device is 
provided as output device, for example an LCD display. The wheel pulses L 
and R of the sensors 3, 4 are respectively supplied to a counter 23, 24, 
the count of which is entered into the microcomputer 21 by means of a 
signal issued by the microcomputer 21. In an exemplary embodiment operated 
in actuality, the count was read in every 150 ms, after which the counter 
was returned to zero. For the course, a customary magnetic sensor 8 
provides an angle .alpha..sub.M in the shape of a pulse-width modulated 
signal. By means of an appropriate converter 25 the pulse width is 
converted into a corresponding digital signal and entered regularly into 
the microcomputer 21. 
Determination of Straight-ahead Driving. 
FIG. 3 schematically represents the path 31 of a vehicle. Individual 
positions P1 to P9 of the vehicle are indicated by cross strokes. The 
vehicle pulls an observation course after itself, so to speak, which has 
been boxed for the position P1. The observation course 32 consists of four 
observation windows F1 to F4, and the data collected while driving over 
the respective course (wheel pulses, course information of the magnetic 
sensor) are added up in each observation window. The observation windows 
F1 to F4 are operated in the form of a loop memory. When the vehicle 
arrives at the next position P2, the content of the oldest window is 
replaced by the data which had been added up in the meantime. 
The respective course change delta .alpha..sub.M is stored in the 
observation windows for determining straight-ahead driving. The contents 
of the storage spaces assigned to the observation windows are shown for 
the positions P1 to P9 as a table in FIG. 4. The signal .alpha..sub.M of 
the magnetic sensor is interrogated repeatedly during an observation 
window, so that it is possible already to reduce a portion of the 
interference by means of the low-pass effect being generated. In addition, 
methods for processing the output signal of a magnetic sensor are known in 
accordance with which, in addition to the signal representing the course, 
a further signal is generated which takes the quality of the course signal 
into consideration. A method of this type is described in U.S. patent 
application P No. 36 44 683 of the present applicant. 
If the vehicle is in position P1, the observation windows are filled with 
positive values for delta .alpha..sub.M, because the entire observation 
course is formed by a right-hand curve. This is also valid for position 
P2. But a straight line starts at this position, so that in the successive 
position P3 an observation window 4 is already filled with the value 0. 
However, in actuality no discrete values (+, 0, -) occur. This 
illustration was selected merely for the sake of clarity. 
When the vehicle has reached the next position P4, the contents of two 
observation windows already are 0. At position P6 all four observation 
windows have the value 0. Therefore it is determined at this time that the 
vehicle has driven in a straight path over the observation course 33 shown 
in dashed lines in FIG. 3. A circumferential difference of the wheels can 
be calculated, a suitable correction value stored or the circumference of 
a wheel can be suitable changed from the respective simultaneously 
observed wheel pulses or from the difference between the wheel pulses. 
An extensive utilization of the path sections which in general are suited 
for the respective observation becomes possible by means of splitting the 
observation course into individual observation windows and by cyclically 
processing them. If, for example, the signals of one observation course 
were to be evaluated and a new observation course were to be started then, 
an assured utilization of a short straight path would not be possible in 
the example in accordance with FIG. 3. The observation course in position 
P5 has another curved section, while the then following observation course 
in position P9 again contains curved sections. 
Because the deviations of the effective wheel diameters depend, among other 
factors, on the vehicle speed, the correction values are respectively 
determined for individual speed ranges, and are stored and utilized. Here 
it has been shown to be advantageous to divide the occurring speeds into 
ranges of 30 km/h, wherein the first range extends to 40 km/h, so that the 
speeds usually maintained in city traffic fall into one range. As already 
mentioned, the observation course is switched as a function of the speed 
ranges, for example in a total range of 60 m to 800 m. 
An observation is broken off, i.e. the observation windows are erased, when 
the limits of a speed range are exceeded, because the evaluation of 
signals of different speed ranges is not sensible. Also, an observation 
course is only continued, if a minimal speed (for example, loss of a 
wheel) is not downwardly exceeded, if delta .alpha..sub.M is less than 
5.degree., for example, and if no sensor error has been detected. Such a 
one is present, for example, if the quality signal of the magnetic sensor 
or a plausibility test of the wheel pulses detects an error. For example, 
strong deviations of the wheel pulses L and R from each other suggest an 
error, because with even the narrowest curve radii the ratio of the wheel 
pulses cannot be greater than 1.5, for example. 
For further description of the derivation of correcting values for the 
wheel pulses, the most important values used in the course of observation 
have been compiled in the form of a table in FIG. 5. In this case the four 
observation windows F1 to F4 for the course change delta .alpha..sub.M 
have been complemented by observation windows FL1 to FL4 for the wheel 
pulses L and observation windows FR1 to FR4 for the wheel pulses R. A 
further value comprises the the sum of all "old" observation windows, 
while the values DEL, DELL and DELR respectively represent the value which 
is in summation, L, R, delta .alpha..sub.M. The value ZAE indicates the 
respectively active observation window. The values LAE and TEI are used to 
set the length of the observation windows and thus of the observation 
course. For this purpose, TEI is set to a speed-dependent value and LAE is 
incremented until it is greater than TEI. In this case, the setting is 
LAE=LAE-TEI and DEL is stored in the observation window indicated by ZAE. 
ZAE is cyclically set forward, the new window sum SUM is formed and the 
value DEL is erased. 
The sum formed from the observation windows and from the value DEL is 
subsequently evaluated. Thus, a past value of the maximum length of the 
product of the number of windows +1 and the value TEI is always evaluated 
with small calculating effort. 
FIG. 6 shows a greatly simplified flow diagram of the program in the 
microcomputer 21 (FIG. 2) which is used for detecting straight-ahead 
driving and for determining the correction values for the correction of 
the wheel pulses. Starting at 41 is followed by initialization at 42, in 
which the values SUM, DEL and LAE are set to 0. ZAE is set to 1. Then, at 
43, an inquiry regarding the number of wheel pulses L, R and of the course 
.alpha..sub.M is made. Delta .alpha..sub.M is formed in the program 
section 44 by forming the difference with the inquiry in the previous 
program run. Following this, the speed v is calculated at 45 from the 
result of the inquiry of the wheel pulses L and at 46 the value TEI is 
read out from a memory as a function of the range in which the calculated 
speed v lies. To arrive at a more accurate speed calculation, it is 
possible to count the wheel pulses over several cycles of the program 
(scanning intervals), followed by a division by the number of cycles. 
The program branches at 47, depending on whether the speed v has reached 
another range or whether there are other reasons for terminating the 
observation and beginning a new observation. If this is the case, new 
initialization is performed at 42. But if the vehicle still operated in 
the same speed range, the values DEL, DELL and DELR are increased in the 
following program section 48 by delta .alpha..sub.M, L or R, respectively. 
The value LAE is also incremented at 49. 
This is followed by branching at 50, depending on whether LAE is greater 
then TEI. If this is not (yet) the case, the program steps 43 to 49 are 
repeated. But if LAE is greater than TEI, processing of an observation 
window is terminated. Then LAE is set to LAE=LAE-TEI at 51. The values 
collected as the values DEL, DELL and DELR are assigned to the observation 
windows F, FL and FR, each of which is defined by ZAE (program section 
52). In program section 53 the sums of respectively four observation 
windows are formed. Following this, the subsequent observation windows 
(ZAE=1) are set to 0 at 54. After that ZAE is incremented at 55, in which 
case the value 0 follows a value 4. 
At 56 the program is branched depending on whether SUM is smaller than a 
preset threshold value SUM1. By means of this it is determined in the 
course of processing each observation window whether there is 
straight-ahead driving. If SUM is not smaller than SUM1, the subsequent 
observation window is processed as described. But if SUM is smaller than 
SUM1, the diameter difference delta U, and from this the pulse number IZ, 
is calculated in program section 57 from the values SUML and SUMR. The 
pulse number IZ is averaged with the pulse number IZ.sub.(k-1) in the 
memory at 58 and the result is stored as correction value. This is then 
continuously available for correction, and when the pulse number 
IZ.sub.(k)u from the wheel pulses of the smaller wheel has been reached, 
one pulse is subtracted. 
Determination of the Direction of the Course Change 
To prevent mistakes and to adapt the correct parameters it is important to 
recognize during location determination if and in which direction the 
course changes--in other words, whether the operation is over straight 
distances, left or right curves. A sufficiently long observation course is 
necessary for this in order to also detect slight curves in the 
superhighway. For this, a vector number is used as criteria because of the 
equidistance (120 to 180 ms) of the detection over the speed range (for 
example 0 to 300 km/h). To obtain an evaluation independent of the number 
of teeth of the wheel sensor, 
ZAE=constant/UPu 
is determined for the observation course, where the constant is selected as 
20.96, for example, and UPu is the number of pulses per revolution. 
The differences between the already corrected wheel pulses LC and RC are 
collected over the observation course. If the result is a sum greater than 
1, for example 2, the sign of the sum corresponds to the difference in 
direction. Slighter curves are clearly detected by this. But detection is 
delayed. In accordance with a further embodiment of the invention, a newly 
taken direction is detected more quickly in that the newly added pulse 
differences are examined for value and sign. 
If they already correspond to the direction present on the observation 
course or if they are 0, they are processed. If, however, they have an 
opposite sign and a value equal to 0, they are taken into consideration 
once, because this might be the previously mentioned pulse correction. But 
if differences having the opposite sign and a value equal to 1 show up for 
a second time, the present values for the observation course are erased 
and a new observation course is started. In case of differences with the 
"wrong" sign and a value greater than 1, the present values are already 
being erased when this occurs for the first time, and a new observation is 
started. 
Correction of the Detected Course Changes 
If the vehicle moves on a circular arc, the course change delta .alpha. is 
proportional to the angular speed omega with which the vehicle moves 
around the center (FIG. 7). The angular speed is a result of: omega=v/r, 
where v is the speed of the vehicle and r the radius of the curve. If the 
angular speed--as already briefly described in connection with FIG. 1--is 
calculated from the differences of the pulses L and R, the following 
connection applies: omega=k.delta I/delta t. Among others, the axle width 
is contained in the constant k. 
However, the effective axle width is not constant, but depends on the 
steering angle, the speed and other factors. For this reason the angular 
speeds or course changes calculated from the differences in pulses are 
multiplied by factors which are detected, stored and applied in accordance 
with an adaptive method for several speed ranges, course change ranges and 
for both directions of course change. This method will be described in 
detail below by means of the flow diagram shown in FIG. 8. 
After initial start-up at 61, initialization takes place at 62. Then the 
values delta .alpha..sub.M and delta .alpha..sub.C are observed in program 
section 63. Observation takes place in a manner similar to the observation 
for the purpose of detecting straight-ahead driving and for the purpose of 
circumferential correction of the wheels. For this reason details of the 
observation 63 are not shown in FIG. 8. Because of the greater differences 
between the pulses RC and LC it is possible to select a shorter 
observation course during cornering than during the observation of 
straight-ahead driving and observation of the direction of change. After 
the subsequent branching 64, the observation is continued until the 
observation window is full. 
After that it is determined by means of a comparison with stored threshold 
values at 65 in which range delta .alpha..sub.C is located. It is then 
decided at 66 whether this range is still the same as in the previous 
observation window. If this is not the case, the observation must be 
terminated and the observation program must be re-initialized at 62. But 
if the course change or the curve radius is still in the same range, a 
check is subsequently made at 67 whether the speed is still in the 
previous range. If this is not the case, a new observation is also 
started. Otherwise a check is made at 68 whether there is a sensor error 
or not. This can take place, for example, by an evaluation of the quality 
signal of the magnetic sensor 8 (FIG. 1) or a plausability test of the 
wheel pulses. 
If there is no sensor error, it is determined at 69 whether the observation 
course is complete. If this is not the case, observation is continued at 
63. If, however, the observation course is complete, branching takes place 
at 70 depending on whether delta .alpha..sub.M is greater, equal to or 
less than delta .alpha..sub.C. If delta .alpha..sub.M is greater than 
delta .alpha..sub.C, the correction value C for the respectively 
determined range (B.sub.v, B.sub.delta .alpha.) is increased by a preset 
value delta C at 71. If the two values for the course change are the same, 
C remains unchanged. Otherwise the correction value C is reduced at 72. C 
is stored at 73. 
For the purpose of as exact as possible a correction it would be necessary 
to provide a division into many small ranges for the speed v as well as 
for the course change delta .alpha.. However, driving situations suitable 
for correction within each one of these ranges then occur relatively 
seldom. The calculation effort is also increased. For this reason a 
compromise between the accuracy of the correction (number of ranges) and a 
sufficiently frequent correction has to be found for the respective use. 
In an arrangement realized in accordance with the invention, ten speed 
ranges and four course change ranges for respectively both directions of 
change were selected. Here, a non-linear division of the ranges for the 
course change delta .alpha. was made, because a driving situation with 
large course change values occurs less often and these ranges are 
otherwise very slowly learned. As limits, 1/8, 3/8 and 5/8 of the dynamic 
threshold value are for example possible, which is normalized in such a 
way that it is calculated as a whole number. 
The course change values used in the end for composite locating are 
calculated in accordance with the formula: delta .alpha..sub.C =delta 
.alpha..C(B.sub.v, B.sub.delta .alpha.). Because the detection of 
correction factors C in the limit ranges does not make sense when 
cornering, observation and thus adaptation of the correction factors C 
takes clearly place below the threshold value delta .alpha..sub.max of the 
course change delta .alpha.. This threshold value is shown in FIG. 9 as a 
function of speed. The straight part applies to driving with the smallest 
possible curve radius (turning circle). At higher speeds the maximum 
course change delta .alpha..sub.max is reversely proportional to the 
speed. The curve shown in FIG. 9 only shows an absolute upper threshold 
delta .alpha..sub.max for values of delta .alpha. which can be evaluated. 
Since the plurality of drivers virtually never reach the upper threshold 
ranges, within the framework of a further embodiment of the method of the 
invention the total range of the course change used for observation and 
adaptation is related to a dynamic threshold value which is continuously 
adapted and which normally lies below delta .alpha..sub.max. This takes 
place in such a way that the dynamic threshold value is initiated at, for 
example, 50% of the mathematically possible value of a lateral 
acceleration of, for example, 4 m/sec.sup.2 and is slightly increased in 
case of it being exceeded. In this case an increase by only a slight 
amount is made. In addition, sudden excesses of more than 25%, for 
example, are considered to be no longer valid, because this could be 
anti-lock breaking. 
When dividing the speed ranges into sections, it is possible to state for 
every range a maximum expression for an expression which is proportional 
to the course change. For initialization, this value is inserted into a 
table of the dynamic values. Because of this, sensible learning is 
possible from the start, because each increase in the normalization value 
requires re-learning of the factors. To take driving dynamics into 
consideration, double this value is inserted into the table for threshold 
values. It represents a limit, which must never be exceeded. 
FIG. 10 shows a table of the correction factors for the course changes, 
which is actualized during each learning process and is continuously used 
for composite locating. In addition to the correcting factors C(B.sub.v, 
B.sub.delta .alpha.) for ten speed ranges B.sub.v =0 to 9 and eight course 
change ranges B.sub.delta .alpha. =1 to 4 and -1 to -4, absolute and 
dynamic threshold values delta .alpha..sub.max, delta .alpha..sub.maxdyn 
for the course change have been entered into the table. A table of this 
type is stored in a non-volatile memory associated with the microcomputer 
21 (FIG. 2) and is actualized as described during operation of the vehicle 
.