United States Patent [191
`Rath
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,964,679
`Oct. 23, 1990
`
`[73] Assignee:
`
`[54] MONITORING METHOD AND APPARATUS
`FOR A BRAKE SYSTEM OF HEAVY-DUTY
`VEHICLES
`[75] Inventor: Heinrich-Bernhard Rath, Vallendar,
`Fed. Rep. of Germany
`Lucas Industries Public Limited C0.,
`West Midland, United Kingdom
`[21] Appl. No.: 314,019
`[22] Filed:
`Feb. 23, 1989
`[30]
`Foreign Application Priority Data
`Feb. 23, 1988
`Fed. Rep. of Germany ..... .. 3805589
`
`[51] 1111.015 ......................... .. B60T 8/32; B60Q 1/50
`
`[52] U.S. c1. . . . . .
`
`. . . . . . . . . . . .. 303/100; 180/171;
`
`180/179; 188/1.1l; 303/20
`[58] Field 61 Search ............. .. 303/100, 93, 20, 94-97,
`303/102, 104, 113, 103, 109, 110, 92, 105, 112,
`2-3, DIGS. 34; 340/438, 439, 441, 442, 451;
`73/9; 180/171, 179, 175-178, 197; 188/181 A,
`11, 1.11; 364/426.02, 426.04, 426.05
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56]
`
`3,549,212 12/1970 Leiber .................... .. 303/DIG. 4 X
`3,791,702 2/ 1974 Burckhardt et a1. ......... .. 303/ 100 X
`3,800,904 4/1974 Zelenka ............. ..
`303/ 100 X
`3,893,330 7/1975 Shutz et al. ..
`........... .. 73/9
`4,076,330 2/1978 Leiber .... ..
`.. 188/1.11 X
`4,079,802 3/ 1978 Kawata .......... ..
`303/ 100 X
`4,110,732 8/1978 Jarocha et a1.
`303/95 X
`4,170,274 10/ 1979 Collonia .......................... .. 303/95 X
`
`4,229,727 10/ 1980 Gilhooley ..................... .. 180/121 X
`4,402,047 8/1983 Newton et 0.1.
`4,419,654 12/1983 Funk ................ ..
`4,484,280 11/ 1984 Brugger et a1. ..... ..
`4,610,483 9/1986 Matsumoto et a1. ..
`
`4,685,745 8/1987 Reinecke . . . . . . . . . . .
`
`. . . . .. 303/ 100
`
`4,779,202 10/ 1988 Leiber
`
`303/ 100 X
`
`4,779,447 10/1988 Rath . . . . . . .
`
`. . . . . . . . . . .. 73/9
`
`188/1.11
`4,790,606 12/1988 Reinecke
`180/121 X
`4,796,716 l/1989 Masuda .... ..
`180/171 X
`4,797,826 l/ 1989 Onogi et a1. .... ..
`.. 303/ 100 X
`4,811,808 3/1989 Matsumoto et al. ..
`4,843,553 6/1989 Ohata ............................ .. 180/179 X
`Primary Examiner-Douglas C. Butler
`[57]
`ABSTRACT
`A method of and an apparatus for controlling a brake
`system in a heavy-duty vehicle provide for continu
`ously measuring parameters which are characteristics of
`the state of the vehicle, such as the velocity of the vehi
`cle, the inclination of the roadway, the axle load, and
`the transverse acceleration. Furthermore, the braking
`capability is being monitored continuously. To that end
`the temperature of the brakes, their condition of wear,
`the state of a compressed air reservoir, and the tire
`pressure are measured. For any given state of the vehi
`cle and brakes it is determined whether or not the stop
`ping distance to be expected will be longer than a prede
`termined rated stopping distance. If that is so, the driver
`is warned and/or a reduction of the travelling speed is
`initiated automatically.
`
`3 Claims, 1 Drawing Sheet
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`Swagway_1006
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`U.S. Patent
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`Oct.23, 1990
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`1
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`MONITORING METHOD AND APPARATUS FOR
`A BRAKE SYSTEM OF HEAVY-DUTY VEHICLES
`
`The instant invention relates to a method of and an
`apparatus for monitoring a brake system in a heavy
`duty vehicle.
`Heavy-duty vehicles, such as especially loaded trucks
`with trailers, busses, etc. become a source of great dan
`ger if the braking system is defective. The risk they pose
`can become aggravated still further by human incompe
`tence, particularly by tired drivers.
`It is an object of the invention to provide a method
`and apparatus for monitoring a brake system of heavy
`duty vehicles by means of which any risk caused by
`technical or human inadequacies in respect of the retar
`dation of the vehicle can be countered automatically.
`The method devised according to the invention to
`solve this problem provides for measuring the following
`magnitudes which are characteristic of the state of the
`vehicle:
`’
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`as the predetermined maximum stopping distance and is
`indicated to the driver in addition to the instantaneous
`actual velocity of the vehicle.
`Apart from that, it is possible to warn the driver,
`optically and/or acoustically, of the risk that the brak
`ing capacity is insufficient for the instantaneous condi
`tion of the vehicle in correspondence with the result of
`the comparison between the maximum permissible stop
`ping distance and the actual stopping distance to be
`expected or in correspondence with the comparison
`between the rated vehicle speed and the actual vehicle
`speed.
`Any intentional or negligent ignoring of the alarm
`signal on the part of the driver can be avoided by a
`further development of the invention according to
`which a means is provided which will positively cause
`the actual velocity of the vehicle to be reduced in corre
`spondence with the signal which is responsive to the
`comparison or in case of deviations beyond a given
`tolerance of the actual speed from the rated speed. This
`means can be rendered inoperative voluntarily for a
`given period of time each, especially by an actuator
`member and/or by brie?y shoving the throttle full
`open.
`An embodiment of the invention will be described
`further below with reference to the accompanying
`drawing.
`The FIGURE is a diagrammatic presentation of an
`apparatus for controlling a truck braking system.
`All four wheels 10a, 10b, 10c, and 10d of the truck are
`braked in per se known manner by an anti-lock system
`ABS 12 The ABS system including its control 12 are of
`conventional type known to those skilled in the art and,
`therefore, need not be described in detail here.
`The brake system is monitored by means of a proces
`sor 14. The ?ow of information and commands to and
`from the processor 14 to the various units is shown by
`arrows in the FIGURE. The engine, transmission, and
`brake pedal are designated by reference numerals 16,
`18, and 20, respectively. The brake pedal which the
`driver operates by his foot is coupled to a compressed
`air reservoir in order to enhance the brake pressure.
`The pressure prevailing in the compressed air reservoir
`is determined by a pressurized air sensor 22 and a corre
`sponding measuring signal is input into the processor
`14.
`An inclination sensor 24 determines the inclination of
`the horizontal longitudinal axis of the truck and gener
`ates a corresponding signal likewise for input into the
`processor 14.
`.
`A transverse acceleration sensor 26 determines the
`transverse acceleration of the truck, in other words
`?nds out if the truck is running through a curve. As is
`well-known the coef?cient of brake pressure is reduced
`in response to the transverse acceleration.
`Likewise provided is an axle load sensor 28 which is
`mounted on the axles of the vehicle (only one being
`shown in the drawing) to detect the loading condition
`of the truck. It is possible to replace the axle load sen
`sors on the axles of the vehicle by wheel load sensors
`associated with the individual wheels. That’ has the
`advantage of permitting a comparison to be made be
`tween the wheel loads on the left side of the vehicle and
`those on the right side of the vehicle to ?nd out if there
`is a risk of the vehicle turning over, for instance in a
`curve. Such tilting risk does exist as soon as the wheel
`loads on one side of the vehicle are less than a predeter
`mined minimum value, and in this manner the driver
`
`the velocity (V) of the vehicle,
`the inclination (N) of the roadway,
`the axle load (A),
`the transverse acceleration (Q),
`as well as the following magnitudes which are charac
`teristic of the state of the brake:
`the temperature (T) of the brakes,
`the condition of wear (S) of the brakes,
`the condition of a brake pressure source, such as the
`pressure (P) in a compressed air reservoir,
`the tire pressure (PR),
`and for determining, on the basis of the resulting brake
`and vehicle conditions and in consideration of a given
`maximum permissible stopping distance (XsolI), whether
`or not the predetermined maximum permissible stop
`ping distance (X5011) will be exceeded if the brakes
`should be applied, and for advising the driver of a possi
`ble surpassing of the stopping distance
`The apparatus designed according to the invention to
`meet the object speci?ed is characterized by the follow
`ing measuring means:
`a sensor for the vehicle speed,
`a sensor for the roadway inclination,
`a sensor for the axle load,
`a sensor for the transverse vehicle acceleration,
`a sensor for the temperature of the brakes,
`a sensor for the state of wear of the brakes,
`a sensor for the state of a brake pressure source, and
`a sensor for the tire pressure,
`as well as
`'
`a processor which receives measuring signals from
`the sensors, calculates a stopping distance to be
`expected on the basis thereof, and compares it with
`a predetermined, maximum permissible stopping
`distance, and emits a signal in response to the result
`of the comparison.
`A preferred further development of the method ac
`cording to the invention provides for adjusting the
`maximum permissible stopping distance in response to
`at least one of the magnitudes which are characteristic
`of the state of the vehicle (especially the velocity). The
`adjustment is made based on values of experience, tak
`ing into account a desired safety.
`In accordance with another modification of the
`method according to the invention a maximum rated
`vehicle speed is determined which is coordinated with
`the given state of the brakes and of the vehicle as well
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`signal which cannot fail to be head and/0r seen is given
`to the driver or possibly even an automatic reduction of
`the velocity of the vehicle or even forced braking is
`initiated, as will be described further below.
`There are various possibilities of determining the
`actual stopping distance‘ XL“ to be expected.
`The actual stopping distance Xi,‘ to be expected is a
`function of the values of all the parameters mentioned
`above:
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`may be warned. In addition to such indication, forced
`braking may be initiated.
`A trailer sensor 30 establishes the fact of a trailer
`being hooked up to the truck or not. The trailer is cou
`pled to the truck by connections 42. The trailer, too, is
`equipped with axle load sensors (not shown) and, if
`desired, with all the other sensors described with refer
`ence to the truck.
`As shown in the drawing, each wheel 10a, b,c.d has its
`own brake 32. Likewise associated with each wheel is a
`brake wear sensor 34, a brake temperature sensor 36,
`and a tire pressure sensor 38. A sensor 39 determines the
`velocity of the vehicle. The measuring signals of all the
`sensors are input into the processor 14.
`An indicating or display means 40 is provided to
`inform the driver of the truck whether or not safe brak
`ing is possible with the given instantaneous condition of
`the vehicle.
`The brake system shown in the drawing operates as
`follows:
`_
`All the sensors mentioned are known per se to a per
`son skilled in the art of vehicles, speci?cally in the ?eld
`of brakes so that their structure need not be explained
`here.
`The sensors 22,24,26,28,30,32,34,36,38,39 supply their
`measuring signals according to a given clock rate to the
`processor 14. For example, a complete set of measuring
`data may be input every millisecond for processing in
`the processor 14.
`The stopping distance XL“ to be expected for a given
`state of the vehicle, assuming a customary reaction
`speed of the driver and usual brake actuation, essentially
`depends on the following parameters:
`velocity V of the truck,
`inclination N of the roadway,
`loading condition (axle load) A,
`trailer operation AB (yes/ no),
`transverse acceleration Q of the truck,
`temperature T of the brakes,
`wear S of the brakes,
`state of a brake pressure source (compressed air reser
`voir) P, and
`pressure in the tires P R.
`The ?rst ?ve of the decisive dimensions listed above
`relate to the state of the vehicle, while the last four
`parameters refer to the brake system.
`The data measured with the aid of the sensors then
`are to be used for calculating whether or not safe brak
`ing is possible in the instantaneous driving situation.
`The driver is to be informed at all times whether the
`stopping distance to be expected will or will not exceed
`a predetermined stopping distance X5011.
`The stopping distance X3011 which is to be set for the
`comparison is memorized from the very beginning in
`the processor 14. This value itself is varied as a function
`of the respective travelling speed of the vehicle deter
`mined by the velocity sensor 39 because, at high speeds,
`a longer stopping distance must be put up with than at
`low speeds. The maximum permissible stopping dis
`tance X3011 to be set may correspond, for example, in
`meters to the vehicle velocity in km/h or a fraction
`thereof.
`The respective actual stopping distance Xi" to be
`expected is calculated from the sensor measuring signals
`which are continuously fed at a high clock rate into the
`processor 14. If the calculated actual stopping distance
`Xi“ exceeds the predetermined maximum permissible
`(velocity responsive) stopping distance X5011 an alarm
`
`Leaving aside the trailer operation for which there is
`only the answer “yes” or “no”, each of the other eight
`parameters theoretically may have any desired number
`of values, regardless of the other parameters. That
`would require the processor 14 to be programmed such
`that it would calculate the corresponding actual stop
`ping distance Xim for any desired set of values of all
`eight parameters. To accomplish that, the functional
`dependencies of the actual stopping distance would
`have to be laid down in the processor, a procedure
`requiring extensive amounts of theoretical and empiri
`cal preparatory work.
`Simpler and yet suf?ciently reliable determination of
`the actual stopping distance X3, can be realized by sub
`dividing all the parameters into individual measuring
`intervals, such as five intervals. The number of intervals
`may be made different for the various parameters. For
`example, a higher number of intervals may be selected
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`for those parameters which do not enter linearly into
`the stopping distance but instead at a higher power,
`such as the velocity, while a lower number may be
`chosen for those parameters whose values are're?ected
`by a lower power in the actual stopping distance.
`The storage space and calculatory requirements of
`the processor 14 are reduced considerably by such divi
`sion of measuring ranges into a ?nite number of inter
`vals. It is suf?cient to associate one actual stopping
`distance each with each possible combination of mea
`suring value intervals of all parameters. If, for instance,
`?ve measuring intervals are ?xed for each of the eight
`parameters, the result is some 390,000 possible interval
`combinations with each of which an actual stopping
`distance must be coordinated. Even if this coordination
`need not be done empirically in each case but instead
`can be calculated previously with a suf?ciently high
`degree of accuracy, the memorizing and calculating
`expenditure still is considerable, but can be accom
`plished.
`The determination of the actual stopping distance can
`be simpli?ed in the following manner.
`A single corresponding actual stopping distance Xi“
`is determined for a set of average values of parameter
`data. This means that, to begin with, typical “normal”
`mean values are established regarding the eight parame
`ters mentioned above which may vary continuously.
`For example, the speed is set at 80 km/h, the roadway
`inclination at 0', the loading condition at a typical aver
`age value, the transverse acceleration at 0 km/s2, the
`brake temperature at 30° C., etc. Based on this set of
`average values of a total of eight values, the actual
`stopping distance is determined which is to be expected
`at a normal reaction speed of the driver and normal
`brake pressure. That can be done in simple manner
`empirically.
`Thereupon it is determined experimentally and/or
`theoretically, for each one of the parameters mentioned,
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`Xm=f(parameter) x XL,“
`
`is determined. The function f(parameter) thus de?ned
`describes how the actual stopping distance to be ex
`pected will change if this particular parameter only is
`varied, while the other parameters keep their above
`mentioned “normal” values. The variation of the se
`lected parameter then is with reference to the “normal”
`value of that particular parameter in the set of mean
`values mentioned. In other words, the argument “pa
`rameter” in the function f(parameter) is the difference
`between the “normal” value and the instantaneous
`value of this magnitude.
`The function f is determined for all of the parameters
`and ?led in the processor 14. As regards the parameters
`velocity, roadway inclination, loading condition, and
`transverse acceleration, the functional dependence of
`20
`the actual stopping distance results from elemental
`physical relationships and can be predetermined theo
`retically with a good degree of accuracy. The in?uence
`of the transverse acceleration of the vehicle in a curve
`on the stopping distance has been examined empirically
`(Automobiltechnische Zeitschrift, 1969, pp.l8l-l89).
`The greater the transverse acceleration of the vehicle,
`the shorter the stopping distance to be expected of the
`vehicle. Here again, a functional dependence can be
`established in advance.
`The resulting stopping distance thus is as follows:
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`how a change thereof in?uences the actual stopping
`digital or employs bars, corresponding colors may be
`distance, in other words the function
`chosen).
`If the driver should not react to the alarm signal
`warning him of excessive velocity, then the velocity is
`reduced positively and automatically to the extent re
`quired. This may be done by moving the accelerator
`pedal forcibly in the sense of power reduction and/or
`by cutting in an engine brake. The velocity may be
`lowered also by an automatic step-down of the trans
`mission. In case of vehicle conditions which are ex
`tremely hazardous, such as particularly if the brake
`temperature is exceeding a predetermined maximum
`value and also if the wear sensor indicates that the lin
`ings are so worn that safe braking is no longer war
`ranted, forced braking of the vehicle is released.
`If the transverse acceleration sensor 26 indicates that
`the transverse acceleration approaches a predetermined
`critical value at which turning-over of the vehicle be
`comes a possibility then, too, the driver first is warned
`as described above and/or the vehicle is retarded auto
`matically.
`The driver is in a position to bridge all the forced
`measures taken automatically in accordance with the
`invention. Yet that will be recorded nondestructively in
`the memory of the processor 14. In certain situations the
`driver must be able to overcome the speed reductions
`which otherwise would be initiated automatically. This
`applies to situations on the road where nothing but
`acceleration of the vehicle will help avoid a risky state,
`for instance, on the passing lane.
`Moreover, the various brake temperatures of the
`individual wheel brakes determined by the temperature
`sensors 36 may be compared. And the course in time of
`the temperature rise of the brake disks may be deter
`mined and compared in the computer with given “nor
`mal” courses so as to identify a defective brake. If, for
`example, the measurement of the temperature provides
`that individual brakes run much hotter than other
`brakes of the same vehicle, it may be concluded that
`there is a defect, such as a seized piston, a defective
`bearing, etc.
`What is claimed is:
`1. A method of monitoring a brake system in a heavy
`duty vehicle, the method comprising the steps of
`measuring the velocity (V) of the vehicle,
`measuring the inclination (N) of the roadway,
`measuring the axle load (A),
`measuring the transverse acceleration (Q) of the vehi
`cle,
`.
`measuring the temperature (T) of the brakes,
`measuring the condition of wear (S) of the brakes,
`measuring the condition (P) of a brake pressure
`source, and
`measuring the tire pressure (PR) of the tires of the
`vehicle, and
`determining on the basis of said measured velocity
`(V), inclination (N), axle load (A), transverse accel
`eration (Q), temperature (T), wear (S), condition
`(P) of a brake pressure source, and tire pressure
`(PR), a stopping distance (X,-;;) to be expected,
`comparing said stopping distance (X131) to be ex
`pected with a maximum permissible stopping dis
`tance (xsull), and
`generating a warning signal if said stopping distance
`(Xm) to be expected exceeds said maximum permis
`sible stopping distance (X3011).
`
`The constant of proportionality “a” can be determined
`empirically and depends in particular on the mass of the
`vehicle.
`As regards the parameters relating to the condition of
`the brake, especially the brake temperature and the
`wear of the brake linings, maximum values may be set.
`When they are surpassed the capability of the vehicle to
`be braked at all is at risk. The function then rises
`abruptly, delivering, for instance, an “in?nite” stopping
`distance.
`The individual functions f(parameter) are ?led in
`programmed fashion in the processor, and the actual
`stopping distance X3, is determined at the preestab
`lished clock frequency for each given state of the vehi
`cle.
`If the actual stopping distance Xi,’ determined ex
`ceeds the predetermined rated stopping distance X3011
`the indicating or display means 40 issues an acoustical
`and/ or optical alarm signal to warn the driver.
`It is possible as well to calculate the vehicle velocity
`V which belongs to each actual stopping distance and at
`which the actual and the rated stopping distances would
`be the same. Both velocities can be indicated at the same
`time to the driver on the display means 40. For example,
`the “normal” instantaneous travelling speed of the vehi
`cle measured by the tachometer may be shown by a
`white pointer, and the maximum permissible velocity
`based on the instantaneous, calculated actual stopping
`distance may be shown by a red pointer (if the display is
`
`It is obvious that the individual functions “f” in the
`above formula, as a rule, are different for each parame
`ter. As is known, the function f(V) is as follows:
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`2. A method according to claim 1, characterized in
`that said maximum permissible stopping distance (X3011)
`is varied in response to said measured velocity (V) of
`the vehicle.
`3. A method according to claim 1, characterized in
`that the method further comprises
`determining on the basis of said measured inclination
`(N), axle load (A), transverse acceleration (Q),
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`temperature (T), wear (S), condition (P) of brake
`pressure source, and tire pressure (PR) a maximum
`rated vehicle speed at which the expected stopping
`distance (Xm) does not exceed the maximum per
`missible stopping distance (X3011) and
`indicating said maximum rated vehicle speed.
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