Wheel-slip detection system

A wheel-slip detection system and/or method for implementing self-readhesion or resticking viscous sticking phenomenon after all the wheels of a car have assumed a slipping condition. The detected data are self-retained until all of the wheel speed differences .DELTA.V become smaller than the first speed value .DELTA..alpha.2 regardless of the restoration of all wheel acceleration by the brake release application. Through this method, it is possible to prevent repeated occurrence of any simultaneous gentle or sluggish-slip state of all the wheels when self-readhesion application is not expected so that the increase of brake distance is avoided.

FIELD OF THE INVENTION 
This invention relates to a brake system for railroad cars in which the 
speed of the wheels fixed to the cars is detected and based on the speed 
signals to evaluate and to determine whether a slipping condition is 
occurring on the wheels of the car. 
BACKGROUND OF THE INVENTION 
There is a wheel-slip detection system shown and described in Japanese Pat. 
No. 57-55001, which is a prior type of method for detecting wheel-slip. 
This patent relates to the detection of the speeds of all the wheels and 
the selection of the one with the highest speed to establish the basic 
speed reference to which the speeds of the various wheels are compared to 
determine the speed differential, or to determine the differential value 
of said speed differentials or differentiating the various wheels of said 
wheels to obtain the reduced speeds. When these various speed 
differentials, the various differential values, or the various reduced 
speeds exceed the set value, this unit determines that skidding of the 
wheels is occurring in this method. This skidding information is 
transmitted to the braking system, and is used to control the braking 
force applied to the wheels of the car. 
In the case of railroad vehicle wheels, even when said braking force is not 
decreased, there are times when the slipping condition is dissipated 
naturally in a "resticking viscous sticking phenomenon" or 
self-readhesion. This phenomenon, or effect, shortens the controlling 
distance so that it is something which should be utilized as much as 
possible. 
The prior art method of accomplishing the above results is by making the 
set value higher than a certain selected value and expanding the relative 
spread of the insensitive width, so that it is possible to detect a 
smaller slipping condition if the above-mentioned method was employed. 
On the other hand, when all of the wheels of the car have almost the same 
small skidding values, the wheel which serves as the basic wheel is in a 
skidding situation, and the speed differential of the various wheels with 
respect to the basic speed or the differential speeds of said speed 
differential are small, or when the speeds of each wheel are 
differentiated in order to yield a small differential speed. The method of 
the prior art in which the set value is in the insensitive zone was made 
large and the small slips, hereafter called "sluggish slip", cannot be 
detected, no matter how long it takes. It will be appreciated that in the 
worst possible case, when all the wheels of the car become locked and the 
control distance to be extended causes damage to the outer rims of the 
wheels, namely, causing flat spots on the wheels, become a problem. 
OBJECTS AND SUMMARY OF THE INVENTION 
This invention utilizes the resticking viscous or self-readhesion effect 
phenomenon when a large number of wheels are in a sluggish slip. The 
system detects this situation and makes possible a reduction in the 
control distance and, at the same time, prevents the formation of flat 
spots on the outer rims of the wheels. Once the sluggish slips are 
generated and when the sluggish slips take place, the detection state is 
maintained until the wheels return to approximately normal speeds to 
improve the shortening of the control distance or to prevent the formation 
of flat spots, which are the objectionable. The specific means are 
provided to detect the speed of n wheels, where n is an integer of 3 or 
higher; and then selecting the wheel with the highest speed as the 
standard speed and to determine the speed differential with respect to the 
selected wheel relative to the various other wheels. The system then 
determines the differential values of the differential speeds to ascertain 
the proper speed reduction by differentiating the speed of the wheels and 
using these speed differentials or their differentiated values to 
determine whether the standard value is exceeded. In this method for 
detecting slips, there is a first set value, and a second set value larger 
than said first set value. 
When the first set value is exceeded at a speed differential, its 
differentiated value or the number of reduced speeds become greater than 
the set number, the speed differential or its differential value fall 
below the second set value, and all the accelerations determined by 
differentiating the speeds of the various wheels fall below the basic 
acceleration, all wheels are determined to be slipping, and therefore 
all-wheels-slipping information provides an output. 
After this all-wheels-slipping information has been outputted, this 
information is stored as well as when at least one of the accelerations or 
its differentiated value exceeds the first set value and said 
all-wheels-slipping information is stored in accordance with the present 
invention. 
According to the present method of this invention, when a large number of 
wheels of the particular car go into the "sluggish slip" state, the 
greater number of the speed differential, its differential value, or its 
reduced speed exceeds the first set value so that its number becomes 
greater than the set number, and when all of the accelerations fall below 
the standard acceleration. In other words, the speed differentials or the 
reduced speeds between the various wheels during braking become small and, 
in addition, the situation becomes limited to when the wheels are not in a 
state of acceleration (recovery), such as when the self-readhesive viscous 
behavior can be expected. This is detected as a "sluggish slip" of the 
wheels. 
At the same time, when the information is received that all the wheels are 
slipping, an output occurs. The output is followed by an acceleration 
evaluation which will maintain the all-wheels-slipping information, even 
when some of the wheels are in a speed recovery mode during the 
speed-determining period. Furthermore, when at least one of the speed 
differentials or its differential value exceeds the first set value, the 
acceleration evaluation circuit determines that the wheels have not yet 
fully recovered so that it memorizes or stores all-wheels-slipping 
information. When all of the speed differentials become less than said 
first set value and the speed of all the wheels have returned to 
approximately normal speeds so that the sluggish slip is resolved, another 
evaluation is made, and the all-wheels-slipping information disappears or 
is dumped. 
In addition, after the all-wheels-slipping information is outputted and at 
least one of the speed differential types exceeds the second set value, it 
will be determined that the wheels corresponding to this state have 
experienced significant slipping and such slipping information is 
outputted and, at the same time, the all-wheels-slipping information will 
be dumped. 
Further, once the all-wheels-slipping information has been produced and 
when at least one of the speed differentials exceeds the second set value, 
the wheels in this slip state are considered to be slipping excessively.

BRIEF DESCRIPTION OF THE INVENTION 
In the following explanation of the preferred embodiment, it will be 
assumed that the number of wheels n is four (4) with reference to FIG. 1. 
Referring to the drawings, and in particular to FIG. 1, there is one 
example of a wheel-slip detection system which incorporates the 
operational method of the present invention. 
As shown, four (4) velocity generators G1, G2, G3, and G4 are provided near 
each end of the axles for generating alternating current voltage signals 
having a frequency proportional to the rotational speed of the respective 
wheel of the vehicle. The output signals of the generators G1-G4 are fed 
to the respective one of four (4) speed or velocity-detection circuits 
S1-S4, which produce speed differentials corresponding to the frequency of 
the wheels V1-V4. These speed signals V1-V4 are transmitted to the 
recovery-detection circuit KK and also to the maximum-speed generation 
circuit MAX, as well as to the low-sensitivity slip-detection circuit LK 
and the high-sensitivity slip-detection circuit HK. 
The recovery-detection circuit KK differentiates the speed signals V1-V4 
and compares the acceleration signals derived from the detection units 
D31-D34 with the acceleration signal produced by an acceleration 
generation circuit K3. The acceleration comparison circuits C31-C34 
compare the acceleration signals from said detectors D31-D34 with the 
standard acceleration signal of said generation circuit K3. Each 
comparator outputs a "0" signal when the various acceleration signals are 
below the standard acceleration signal, and outputs a "1" when the various 
acceleration signals exceed the basic acceleration signal. 
That is, when the acceleration of the differentiated wheel speed exceeds 
the selected standard acceleration, the recovery-detection circuit KK will 
be expected to be in a self-resticking state. In addition, the output of 
said recovery-detection circuit KK is transmitted by way of an OR gate 
OR3, an inverter IV3, and an OR gate OR4 to an AND gate AN5 and, in turn, 
to the brake control apparatus (not shown) to convey the behavior and the 
acceleration information of each of the various wheels. 
The maximum-speed generation circuit MAX selects the highest number 
(fastest) of speed signals V1-V4 from said detection circuits S1-S4 and 
outputs this value as the standard speed signal V.sub.max, and transmits 
this value to the second basic speed generator circuit LC of the 
low-sensitivity slip-detection circuit LK and to the first standard speed 
generator circuit HC of the high-sensitivity slip-detection circuit HK. 
The low-sensitivity slip-detection circuit LK includes a deceleration 
speed-detection circuit L1 and a speed-differential detection circuit L2. 
The deceleration speed-detection circuit L1 compares the outputs of the 
deceleration speed detectors D21-D24, obtained by differentiating speed 
signals V1-V4, with the standard low-speed generator K2. The standard 
deceleration speed signals from the generator K2 or deceleration speed 
signals from the detector circuits D21-D24 output "0" when the respective 
deceleration speed signals drop below the standard deceleration speed 
signals, and "1" when the respective deceleration speed signals exceed the 
standard deceleration signals. 
In other words, when the deceleration speed detection circuit L1 for 
low-sensitivity exceeds the comparatively large standard deceleration 
speed obtained by differentiating the vehicle speed, it is assumed that a 
large slipping condition is occurring on the wheels of the car. The output 
of the detection circuit L1 is transmitted to the AND gate AN5 by way of 
the OR gate OR2 and inverter IV2, and is simultaneously transmitted as 
deceleration speed information of each wheel to the dynamic control 
mechanism and brake control device and other devices carried by the car. 
The speed differential detection circuit L2 inputs the standard speed 
signals V.sub.max from the maximum speed generation circuit MAX, and 
compares the second standard speed generator signals LC output as the 
difference between the standard speed signals and the second set value 
V.sub.max -V.sub..alpha.2 and the various speed signals V1-V4 and the 
second basic signals V.sub.max -V.sub..alpha.2, and outputs "1" when each 
speed signal V1-V4 falls short of the second basic speed signal V.sub.max 
-V.sub..alpha.2, and outputs "0" when the various speed signals V1-V4 
exceed the second basic speed signal V.sub.max -V.sub..alpha.2 through the 
second speed differential comparator C01-C04 which make up this system. 
That is, this low-sensitivity speed differential detector L2 compares the 
various speed signals V1-V4 with the standard speed signals V.sub.max and 
when the speed differential exceeds the second set value V.sub..alpha.2, 
which is comparatively large, it is assumed that significant slipping is 
generated by the wheels of the car. The output of the detection circuit L2 
is transmitted to the AND gate AN5 through the OR gate OR2 and inverter 
IV2 and, at the same time, the information is transmitted as 
low-sensitivity slipping information to the other devices. 
As a result, when the low-sensitivity slip-detection circuit LK, comprised 
of the deceleration speed detector L1 and speed differential detection 
circuit L2, outputs "1" from either of the comparators C21-C24 and 
C01-C04, it will be assumed that significant slipping has occurred in one 
of the corresponding wheels of the car, while when "0" is the output, it 
will be assumed that no significant slipping has been generated in any of 
the wheels of the car. 
The high-sensitivity slip-detection circuit HK inputs the standard speed 
signals V.sub.max from the maximum speed generation circuit MAX and 
compares the first standard speed generator HC output as the first 
standard speed signals from the results V.sub.max -V.sub..alpha.2, 
obtained by reducing the first set value V.sub..alpha.1 from which the 
standard speed signal V.sub.max has been substracted, and outputs "1" when 
each speed signal V1-V4 drops short of the first standard speed signal 
V.sub.max -V.sub..alpha.1 and is comprised of the first speed differential 
comparator C11-C14. 
That is, this high-sensitivity slip-detection circuit HK compares the 
various speed signals V1-V4 with the standard signal V.sub.max and when 
the speed differential exceeds the comparatively small first set value 
V.sub..alpha.1, it assumes the comparatively small fist set value 
V.sub..alpha.1, it assumes that slipping has been generated on at least 
one of the wheels of the car. Conversely, when the speed differential is 
less than the first set value V.sub..alpha.1, it assumes that no slipping 
is present in the wheels. The output of the detection circuit HK is not 
only transmitted to the high-sensitivity wheel-slip evaluation circuit HT, 
but is also transmitted through OR gate OR5, AND gate AN5, and OR gate OR6 
to the AND gate AN5. 
The high-sensitivity wheel-slip evaluation circuit HT uses the number 3 as 
the set number for making evaluations and is comprised of AND gates 
AN1-AN4 and OR gate OR1. When three (3) of the first speed differential 
comparators C11-C14 of the high sensitivity slip-detection circuit HK 
outputs "1", OR gate OR1 outputs "1", and this is used to determine that 
the majority of wheels of the car are slipping. Conversely, when the 
number of first speed differential comparators is two (2) or less, it is 
assumed that there is no slipping in a majority of the car wheels. The 
output of the evaluation circuit HT is transmitted through the OR gate OR5 
to the AND gate AN5. 
The output side of this AND gate AN5 is connected to the input side of said 
OR gate OR4. The AND gate AN5 and OR gate OR4 make up a stick or 
self-latching circuit. At the same time, the output side of the AND gate 
AN5 is connected to the input side of the AND gate AN6 which, together 
with the OR gate OR6, make up a stick or self-latching circuit. When the 
output from this AND gate AN5 is "1", this is information on 
all-axles-slipping, namely, sluggish-slip, and this information is 
transmitted to all the other equipment. 
The operation of the equipment illustrated in FIG. 1 will be explained in 
greater detail below, with reference to FIGS. 2 and 3, which specifically 
illustrate a graphic example of the speed V translation for each wheel of 
the car during braking at time t. 
In FIGS. 2 and 3, V4 is the speed V.sub.max of the high-speed axle wheel, 
and V1-V3 are the speeds of the wheels on the other axles, while 
V.sub..alpha.1 is the first set value, and V.sub..alpha.2 is the second 
set value. 
Initially, let us consider the graphic example of FIG. 2. It will be seen 
that there is no axle in acceleration up to time t1. Thus, there is no 
axle which exceeds the standard reduced speed, and the speed differential 
between the axles is less than the first set value V.sub..alpha.1 and none 
of the wheels is slipping. 
Up to time t1, the outputs of all the acceleration comparators C31-C34 of 
the deceleration detection circuit KK are "0", and the output of the 
deceleration speed comparators C21-C24 of the low-sensitivity 
slip-detection circuit LK and the second speed differential comparators 
C01-C04 are "0", and the output of the OR gate OR2 is "0" and that of the 
inverter IV2 is "1". On the other hand, the outputs of all the first speed 
differential comparators C11-C14 of the high-sensitivity slip-detection 
circuit HK are "0", and the output of the OR gate OR1 of the 
high-sensitivity number of slipping axles evaluation circuit HT is "0", 
while the output of the OR gate OR6 is "0". In other words, up to the time 
t1, the output of the OR gate OR6, which is one of the inputs to the AND 
gate AN5, is "0", and the output of the AND gate AN5 is also "0", and no 
all-axles-slipping information is available. 
During the time required to go from time t1 to time t2, the speed 
differential between the speed V1 and the standard speed V.sub.max exceeds 
the set value V.sub..alpha.1, and only the output of the first speed 
differential comparators C11 is "1". The output of the OR gate OR5 becomes 
"1", but prior to this, the output of the AND gate AN5 is "0", so that the 
output of the AND gate AN5 remains "0". Thus, the set number of the 
high-sensitivity axle-slipping evaluation circuit HT is three (3), so that 
the output of the OR gate OR1 remains "0", and the output of the OR gate 
OR6 also remains "0". Thus, during time between times t1-t2, the output of 
the AND gate AN5 is also "0", and no all-axles-slipping information is 
released. In addition, at this time, conditions of the deceleration 
detection circuit KK and the low-sensitivity slip-detection circuit LK are 
the same up to time t1, and the OR gate OR4 and inverter IV2 outputs are 
"1". 
When time t2 expires, and up to time t3, the speed V.sub.3 along with the 
speed V1, have the speed differential with the standard speed exceeding 
the first set value V.sub..alpha.1. The outputs of the first speed 
differential comparators C11 and C13 become "1", and the output of the OR 
gate OR5 is also "1". This is similar to the interval between said time 
t1-t2 so that the outputs of the AND gate AN6 and OR gate OR1 are "0", and 
the output of the OR gate OR6 remains "0". As a result, during the time 
period t2-t3, the output of the AND gate remains "0", and not axle-slip 
information is released. Furthermore, the states of the deceleration 
detection circuit KK and the low-sensitivity slip-detection circuit LK are 
the same as up to the time t3, and the outputs of the OR gate OR4 and 
inverter IV2 remain "1". 
When time t3 expires, in addition to speeds V1 and V3, V2 has a speed 
differential with the standard speed V.sub.max exceeding a first set value 
V.sub..alpha.1 and the three (3) outputs at the first speed differential 
comparator C11-C13 of the high-sensitivity slip-detection circuit HK 
become "1". Since the set number of the high-sensitivity axle-slip 
evaluation circuit HT is three (3), the output of the OR gate OR1 becomes 
"1" despite the output of the AND gate AN6 being "0", and the output of 
the OR gate OR6 becomes "1". During the interval between times t3 and t4, 
the states of deceleration detection circuit KK and low-sensitivity 
slip-detection circuit LK remain the same up to time t3, and the outputs 
of the OR gate OR4 and the inverter IV2 remain "1". As a result, when time 
t3 is passed, the output of the AND gate AN5 becomes "1", and 
all-axles-slipping, sluggish-slip information is released. 
Then, based on this all-axles-slipping information, the braking force is 
increased, and when time t4 is passed, speeds V1-V4 begin to recover. On 
the other hand, during the interval between and up to time t5, all the 
speed differentials exceed the first set speed V.sub..alpha.1 so that the 
output of the OR gate OR1 is "1". Thus, the two (2) inputs to the AND gate 
AN6 are "1", and its output becomes "1" so that the output of the OR gate 
OR6 remains "1". At the same time, every speed V1-V4 is in a recovery 
status, so that their degrees of acceleration are all less than the 
standard acceleration, and the outputs of all the accelerating comparators 
C31-C34 of the deceleration detection circuit KK are "0". The inverter IV3 
output is "1", and the OR gate OR4 output is "1". In addition, at this 
time, there is no speed which exceeds the standard deceleration speed, and 
there is not speed differential which exceeds the second fixed value 
V.sub..alpha.2 so that the outputs of all the comparators C21-C24 of the 
low-sensitivity slip-detection circuit LK and C01-C04 are "0" while the 
inverter IV2 output is "1". As a result, during the interval between time 
t4-t5, the all-axles-slipping information is to be expected. Furthermore, 
when at least one of the accelerations exceeds the standard acceleration, 
the output of the corresponding accelerating comparator becomes "1", and 
the output of the OR gate OR3 becomes "1". The output of the inverter IV3 
becomes "0", but the OR gate OR4 has a feedback of "1" from the AND gate 
AN5, which is the all-axles-slipping information to bring about a 
self-retention or holding condition. Thus, the output of the OR gate OR4 
remains at "1", and the all-axles-slipping information is in the 
self-retention or holding state. 
As we approach time t5, the basic speed V.sub.max of speed V2 has a speed 
differential with respect to V.sub.max which is below the first set value, 
and the speed differential which exceeds the first set value becomes two 
(2), thus, the high-sensitivity number of slipping axles circuit HT of the 
OR gate OR1 output becomes "0". However, the two (2) outputs of the first 
speed comparators C11 and C13 are at "1" so that the output of the OR gate 
OR5 is also "1" and, together with the output of the AND gate AN5, which 
is an all-axles-slipping information, is at "1" which is fed back to the 
AND gate AN6. Thus, the AND gate AN6 is in a self-retention or holding 
state and its output remains "1", so that the OR gate OR6 output retains 
the value "1". At this time, the deceleration detection circuit KK and the 
low-sensitivity slip-detection circuit LK are in the same state as they 
were during the time interval t4-t5. The stick circuit of the OR gate OR4 
outputs "1" for a self-retention, and the output of inverter IV2 is "1". 
As a result, even in this time interval t5-t6, the output of the AND gate 
AN5 remains "1", and the all-axles-slipping information is retained. 
When time t6 is reached, the speed differential relative to the standard 
speed V.sub.max of speed V.sub..alpha.1, with respect to speed V2, falls 
below the first set value V.sub..alpha.1, and the speed differential which 
exceeds it becomes "1". The output of the OR gate OR1 of the 
high-sensitivity axle-slipping evaluation circuit HT remains "0", which is 
similar to that of the time interval t5-t6. The output of the first speed 
differential comparator C13 is at "1" and the output of the AND gate AN5 
is also "1", which causes the output of the AND gate AN6 to stay at "1". 
As a result, the output of the OR gate OR6 is also set at "1". At this 
time, as in time interval t5-t6, the outputs of the OR gate OR4 and the 
inverter IV2 are "1". Thus, even during time interval t6-t7, the output of 
the AND gate AN5 remains at "1", and the all-axles speed information is 
maintained in a self-retention state. 
When time t7 is passed, all the speed differentials become less than the 
first set value V.sub..alpha.1, so that the high-sensitivity 
slip-detection circuit HK and the outputs of the comparators C11-C14 are 
at "0". The output of the OR gate OR1 remains at "0", while the output of 
the OR gate OR5 also becomes "0" along with that of the OR gate OR6. As a 
result, when time t7 is passed, the outputs of the OR gate OR4 and the 
inverter IV1 and the output of the AND gate AN5 become "0", and all the 
information disappears. In this state, it is assumed that all the wheels 
are not slipping and will remain in nearly normal speeds, and have 
decelerated. 
Furthermore, the above state in which the axle-slipping information is 
self-maintained, and if for some reason it declerates quickly, exceeding 
the basic deceleration and/or the deceleration exceeds the second set 
value V.sub..alpha.2, the low-sensitivity slip-detection circuit LK 
detects this situation and brings about corresponding decelerating 
information of the wheel and/or outputs low-sensitivity slip information, 
along with the output of the OR gate OR2, and becomes "1". The output of 
inverter IV2 becomes "0", so despite the outputs of the OR gates OR4 and 
OR6, the output and the AND gate AN5 becomes "0", and all slip information 
disappears. 
Another graphic illustration, which slightly differs from that illustrated 
in FIG. 2, is shown in FIG. 3 and operates in the following manner. 
It will be appreciated that up to time t10, there is no speed in any 
deceleration stage, so that the outputs of inverter IV3 and the OR gate 
OR4 are both "1". There is no speed which exceeds the standard 
deceleration so the output of inverter IV2 is at "1", and when the number 
of decelerations which exceed V.sub..alpha.1 is less than two (2), the 
state before this is attained as the output of AND gate AN5 at "0". Thus, 
the output of the OR gate OR6 is also "0". As a result, no axle-slip 
information is released before time t10. 
During the time interval t10-t11, the deceleration speed of speed V2 
exceeds the standard deceleration speed so that the output of the 
deceleration speed comparators C22 is "1" and the output of inverter IV2 
becomes "0", regardless of the outputs of the OR gates OR4 and OR6, and 
thus no all-axles-slipping information is released. On the other hand, at 
this time, the deceleration speed information with regard to speed V2 is 
released. 
During time interval t11-t12, speed V2 has recovered and its acceleration 
exceeds the standard acceleration, so that the output of the acceleration 
comparator C32 becomes "0". The output of inverter IV3 becomes "0", and 
the preceding state has the output of the AND gate AN5 at "0". Thus, the 
output of the OR gate OR4 is "0", regardless of the outputs of the 
inverter IV2 and the OR gate OR6. The output of the AND gate AN5 remains 
"0", and no all-axles-slipping information is released. 
During time interval t12-t13, the speed differential of speed V1, with 
respect to the standard speed V.sub.max, exceeds that of the second set 
value V.sub..alpha.2 so that the output of the second speed differential 
comparator C01 is "1". Thus, the output of inverter IV2 becomes "0", 
regardless of the state of the outputs of the OR gates OR4 and OR6. Thus, 
the output of the AND gate AN5 remains at "0", and no all-axles-slipping 
information is released. On the other hand, no low-sensitivity slip 
information is released at this time with respect to speed V1. 
During time interval t13-t14, speed V1 has recovered and its acceleration 
exceeds the standard acceleration so that the output of the acceleration 
comparator C31 is "1". The output of the inverter IV3 is at "0" as is the 
output of the AND gate AN5 which is also "0". The output of the OR gate 
OR4 becomes "0" and, consequently, despite the outputs of the inverter IV2 
and the OR gate OR6, the output of the AND gate AN5 remains "0" and no 
all-axles-slipping information is released. 
During time interval t14-t15, the acceleration of speed V1 and V2 during 
recovery, is below that of the standard acceleration, so that the outputs 
of all the acceleration comparators C31-C34 are at "0". The outputs of 
inverter IV3 and OR gate OR4 become "1". The deceleration speed V3 is 
below the standard deceleration speed and, together with three of the 
speed differentials exceeding the first set value V.sub..alpha.1, but 
falling short of the second set value V.sub..alpha.2, the result is that 
the outputs of all the deceleration speed comparators C21-C24 and the 
second speed comparators C01-C04 become "0". The output of the inverter 
IV2 becomes "1" and, together with the outputs of three of the first speed 
differential comparators C11-C13, becomes "1". The outputs of the OR gates 
OR1 and OR6 become "1". The output of the AND gate AN5 becomes "1", and 
the all-axles-slipping information is released. 
During time interval t15-t16, the situation is just as it was during the 
time interval t5-t6 (as shown in FIG. 2); and during the time interval 
t16-t17, the situation is the same as for the time interval t6-t7 in FIG. 
2. Similarly, after time interval t17, the situation is the same as after 
time t7 in FIG. 2, so that any further explanation will be omitted for the 
purpose of convenience. 
In both of the above-described examples, the number of wheels was assumed 
to be four (4) and the set number for the sluggish-slip, which is a 
determining factor in the evaluation of wheel-slip, was set at three (3). 
However, if the number of wheels n is more than three (3) and the set 
number is more than two (2), the present system can still be used 
effectively. 
Similarly, in both of the examples, the low-sensitivity slip-detection 
circuit LK was comprised of the deceleration speed-detection circuit L1 
and the speed differential detection circuit L2, but either one will do by 
itself, or a mode in which the speed differential's differentiated value 
is evaluated or a combination of these modes will also do. 
Furthermore, in both of the examples, the high-sensitivity slip-detection 
circuit HK was assumed to evaluate the speed differential, but this can be 
replaced by an evaluation of the differential value of the speed 
differential. 
As is clear from the description above, the following advantageous features 
and effects can be achieved by the subject invention: 
1. When the majority of the wheels of the car go into a sluggish-slip and 
start a small slip almost simultaneously, it is usually the case that the 
speed differential, its differential value, or the deceleration speed is 
insensitive and will normally not exceed the large second set value so 
that they are unable to detect this situation. Under this condition, if 
there are no wheels which are accelerating, namely, under recovery, the 
effect of self-resticking viscous adhesion cannot be expected to occur. 
Thus, there is a possibility of all the wheels being locked-up, but when 
this invention is employed in such situations, a first set value, smaller 
than the second set value, is used jointly so that the speed differential, 
its differential value, or reduced speed exceeds the first set value. 
Thus, it is assumed that all the wheels are slipping and this information 
is relased and can be used by initiating a reinforced brake force on all 
wheels. Consequently, the viscous resticking property can be accelerated 
and the control distance can be effectively reduced so as to prevent the 
generation of flat spots on the outer rim of the wheels of the car. 
2. When the value of the speed differential or its differential value has 
exceeded the first set value, or when an acceleration which exceeds the 
standard acceleration is present; in other words, when there is a wheel in 
the midst of recovery, namely, in acceleration, the situation is not 
evaluated as all axle-slip, namely, sluggish-slip, so that self-viscous 
resticking or self-readhesion phenomena can be utilized effectively and a 
reduction in control distance can be accomplished. 
3. When there is a wheel in which a large slip has been initiated which 
could not be expected from its speed differential or its differential 
value, the situation is not evaluated as all wheels are slipping, so that 
only the slip of the particular wheel alone can be evaluated. 
4. After all axle-slip information is released, even when there is a wheel 
in the process of recovery, all the wheels are restored to roughly normal 
speeds; that is, until the speed differentials are in an insensitive 
status, and recover to less than a small first set value, the 
all-axles-slipping information is self-retained so this information can be 
used to reinforce the braking force. Thus, all wheels can be controlled so 
that they will not generate sluggish-slip, and the reduction in said 
control distance and the prevention of the formation of flat spots on the 
outer rim of the wheels of the car can be avoided. 
The following is a list of nomenclature in reference to the system of the 
present invention: 
G1-G4: speed generator 
S1-S4: speed detection system 
V1-V4: speed--MAX: maximum speed generation circuit 
V.sub.max : basic speed--KK: deceleration detection circuit 
LK: low-sensitivity slip-detection circuit 
HK: high-sensitivity slip-detection circuit 
HT: high-sensitivity number of slipping axles evaluation circuit 
L1: deceleration speed detection circuit 
L2: speed differential detection circuit 
K2: standard deceleration n speed generator 
K3: standard acceleration generator 
V.sub..alpha.1 : first set value 
V.sub..alpha.2 : second set value 
The following list is pertinent to FIG. 1: 
1. speed generator 
2. speed detector 
3. acceleration 
4. standard acceleration 
5. deceleration detection circuit 
6. acceleration comparator 
7. acceleration information 
8. maximum speed generator 
9. standard deceleration speed 
10. deceleration speed detection circuit 
11. deceleration speed comparator 
12. deceleration speed 
13. deceleration speed information 
14. second standard speed generator 
15. second set value 
16. low-sensitivity slip-detection circuit 
17. second speed differential comparator 
18. speed differential detection circuit 
19. first set value 
20. first speed differential comparator 
21. first standard speed generator 
22. all-axles-slipping information 
23. high-sensitivity slip-detection circuit 
24. high-sensitivity number of slipping axles evaluation circuit 
The following list is pertinent to FIG. 2: 
1. speed V 
2. first set value .alpha.1 
3. second set value .alpha.2 
4. time t 
5. wheel velocities V1, V2, V3, V4 
The following list is pertinent to FIG. 3: 
1. speed V 
2. first set value .alpha.1 
3. second set value .alpha.2 
4. time t 
5. wheel velocities V1, V2, V3, V4 
It will be understood that various alterations and changes may be made by 
those skilled in the art without departing from the spirit and scope of 
the subject invention. Therefore, it will be appreciated that certain 
modifications, ramifications, and equivalents will be readily apparent to 
a skilled artisan and, accordingly, it is understood that the present 
invention is not to be limited to the exact embodiment shown and described 
but should be afforded the full scope and protection of the appended 
claims.