PatentDe  


Dokumentenidentifikation EP0581894 27.04.1995
EP-Veröffentlichungsnummer 0581894
Titel BREMSEN MIT VERZÖGERUNGSSTEUERUNG.
Anmelder Allied-Signal Inc., Morristown, N.J., US
Erfinder PHIPPS, Jack, Ralph, Novi, MI 48375, US;
VERNER, Douglas, Robert, Sterling Heights, MI 48313, US
Vertreter Patentanwälte Hauck, Graalfs, Wehnert, Döring, Siemons, 80336 München
DE-Aktenzeichen 69201791
Vertragsstaaten DE, ES, FR, GB, IT
Sprache des Dokument En
EP-Anmeldetag 15.04.1992
EP-Aktenzeichen 929135119
WO-Anmeldetag 15.04.1992
PCT-Aktenzeichen US9203173
WO-Veröffentlichungsnummer 9219479
WO-Veröffentlichungsdatum 12.11.1992
EP-Offenlegungsdatum 09.02.1994
EP date of grant 22.03.1995
Veröffentlichungstag im Patentblatt 27.04.1995
IPC-Hauptklasse B60T 8/80

Beschreibung[en]
BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a method of controlling the braking of a vehicle, as more specifically defined in the preamble of Claim 1.

Document DE-A-37 22 107 is illustrative of such a prior electronic braking system. This document shows a brake system and method directed to the generation and distribution of hydraulic brake pressure to various brake mechanisms. The method is directed to the generation and distribution of hydraulic brake pressure to various brake mechanisms, by fencing wheel skid, generating a signal indicative of brake effort and monitoring the change in the velocity of wheel speed.

In conventional braking systems, a pressure is applied to each brake unit; the braking torque generated from the pressure acting on a piston (or pistons) forces some friction material to act on a rotating element (usually a drum or a disk). The same pressure is normally applied to both wheels of an axle. Frequently to prevent vehicle instability due to locking of the rear wheels before lockup of the front wheels, a proportioning valve(or valves) modulates to rear wheel brake pressure. Sometimes an adjustable proportioning valve, sensitive to vehicle spring deflection, is used which attempts to maintain proper brake balance. The adjustment rebalances the brakes (front to rear) as a result of changes in vehicle loading.

The usual (conventional) approach has some shortcomings. The coefficient of friction between the brake pads/shoes and the rotating element is not uniform. In high-volume production, the coefficient of friction may vary significantly batch to batch. Allowances are made for this variation, to insure that the rear wheels do not lock prematurely, causing vehicle instability. This "safety margin" results in less than best brake balance. Furthermore, the usual brake balancing schemes assume a nominal friction coefficient of friction of the brake pads and linings and also assume that the reaction torque at the tire/road interface is consistently related to brake torque. This is not always true since if the tire size (rolling radius) changes appreciably, the lever arm, through which the torque acts, will also change.

These shortcomings result in compromises in brake effectiveness, and can cause uneven wear of tires, brake linings, etc. A cost penalty, as well as some degradation in reliability, results from the addition of a load-sensing or a deceleration sensing proportioning valve to adjust the rear braking pressure as a function of the front braking pressure.

Although not a functional element, the subjective reaction of drivers to the perception of force required versus pedal travel, is limited by the need to provide enough fluid displacement to place the brake shoes/pads in contact with the drum/rotor. Pedal travel is dependent on the compliance of a brake and is also affected by any air entrained in the brake hydraulic fluid. The above factors determine the stroke of the master cylinder and therefore the stroke brake pedal. Geometry of the pedal/master cylinder combination can be varied within limits, but for ease of use, excessive travel of the pedal cannot be accommodated. Further, to develop the pedal force required to produce a pressure adequate to stop the vehicle under worst-case conditions, there are other constraints based on physical limitations of the operator.

The present invention is directed to a substantially improved method of regulating the braking effort at the individual wheels, which obviates most or all of the deficiencies noted above.

Specifically, the invention describes a method of regulating the rate of change of velocity (deceleration) of each wheel, based on a deceleration command generated by the operator. The invention envisions an electrically controlled braking system, where the input is an electrical signal derived by any of several sensing processes. The input signal is then examined by a microcontroller, and the appropriate braking activity at each wheel produced.

It is an object of the present invention to provide a braking system in which an allowance is made for differing wheel speeds when negotiating a bend or a corner. A further object of the present invention is to provide a braking system which accommodates the use of different sized tires such as resulting from the use of a temporary spare tire, the use of a severely deflated tire, or the replacement of a previously worn tire with a new one. A further object of the present invention is to provide for antilock braking control with no additional hardware and as such, to provide a cost effective braking system.

Accordingly, the invention comprises: a method of controlling the braking behavior of various wheels of a vehicle during a normal braking mode of operation and during an antilock braking mode of operation. The method uses a control unit or microcontroller which calculates various parameters over a known time or sampling increment. The method including the steps of:

  • 1.1 obtaining a value of the actual rotational velocity of each wheel (W&sub1;,W&sub2;);
  • 1.2 generating a first signal indicative of braking effort P(in) or desired vehicle deceleration;
  • 1.3 generating a per wheel velocity command signal the slope or deceleration of which is proportional to the desired vehicle deceleration p(in) and a multiplicative scale factor (ABSGi+Gi) for adjusting such deceleration during the normal braking mode and antilock braking mode,
  • 1.4 generating a per wheel error signal Ei as a difference between the wheel velocity command and actual rotational velocity of each wheel,
  • 1.5 operating upon the error signal Ei to generate a brake activity command signal Bi,
  • 1.6 regulating brake force in response to the brake activity command signal Bi.

Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

  • FIGURE 1 diagramatically illustrates a brake control system incorporating the present invention.
  • FIGURE 2 diagramatically illustrates a four wheel vehicle.
  • FIGURE 3 illustrates a deceleration command curve.
  • FIGURE 4 shows a time history of wheel velocity versus time.

DETAILED DESCRIPTION OF THE DRAWINGS

As mentioned above, the present invention utilizes an input signal which is examined by a microcontroller to generate a signal indicative of braking activity. Reference is briefly made to FIGURE 1 which diagramatically illustrates the braking system 10 incorporating the teachings of the present invention. There is shown a pedal force sensor 12 for measuring the operator applied braking force as the operator presses upon a brake pedal 14. The output of the sensor 12 diagramatically shown on line 16 is a pedal force input signal p(in). As can be appreciated, the units of the p(in) signal may be in volts per unit of applied braking force. This input signal is received by the microcontroller 20 which also receives as input signals additional system parameters and constants to generate a plurality of braking activity signals generally shown as Bi. In the present invention the pedal force input signal is sealed within the microcontroller 20 to yield a nominal deceleration command signal which is also referred to as p(in). This deceleration command signal is appropriately adjusted for various scale factors to generate a plurality of wheel deceleration command signals as described below.

If, for example, the brake mechanism 30 is a hydraulic brake, the brake activity signal Bi may be used to control the level of hydraulic pressure within the brake 30. FIGURE 1 diagramatically illustrates one method of achieving this control wherein the actual brake pressure is measured by a pressure sensor 32, the output of which is combined with the brake activity signal such as B&sub1; which would be a pressure command signal, to generate a pressure error signal which is communicated to a motor 34, which in turn rotates a pump 36 to pressurize the brake line. Pressure decay within the brake 30 may be achieved by opening an electrically responsive valve 38 in response to a valve activation signal Vi (i=1,2--n) to return brake fluid to the sump 40 of the pump 36. The brake 30 operates directly on a wheel 42, wheel speed Wi is sensed by a wheel speed sensor 44, the output of which is communicated to the microcontroller 20. FIGURE 1 also illustrates another method of brake activation utilizing an electrically controlled brake 30 wherein the brake activation signal, such as for example, B&sub2; is combined with a sensor 50 to generate an error signal causing a motor 52 to move a jack screw 54 thereby urging the friction material against the disk or drum. The applied braking force on the brake 30 is sensed by sensor 50 which can be implemented in many ways such as a torque sensor, a position sensor measuring the number of turns of the motor, or a current sensor measuring motor current which is indicative of developed motor torque. As before, a wheel speed sensor such as 44 is used to generate a signal indicative of the speed of the wheel 42 which is communicated to the microcontroller 20.

In view of the above, the invention contemplates obtaining a value indicative of the actual rotational velocity of each wheel of a vehicle. This is accomplished as the microcontroller 20 interrogates the various wheel speed sensor input signals Wi.

Reference is briefly made to FIGURE 2 which diagramatically illustrates a vehicle having four wheels. As will be seen from the description below, the present invention operates on sets of wheel speed information. In the preferred embodiment of the invention, the microcontroller 20 defines the front wheel rotational velocities (WFR, WFL) as a first set of input parameters and the rear wheel velocities (WRR, WRL) as a second independent set of input parameters. It should be appreciated that the sets of input parameters can also be defined in a split manner, that is, one set utilizing the front left wheel velocity WRR and rear right velocity WFL, while the other set using the front right velocity WFR and rear left velocity WRL. The microcontroller operates on each set of velocities identically. In the preferred embodiment of the invention, the wheel velocities for an exemplary set of such wheel velocities will be described as W&sub1; and W&sub2;.

The microcontroller identifies a command wheel velocity signal for each wheel in the set. If, for example, the microcontroller is implemented to keep track of the time variable t, each wheel velocity command signal Wci would be defined by equation 1.



Wci(t)=Wi(t)-p(in)*(ABSGi+Gi)t   (1)



wherein

   Wci (t) is the wheel velocity signal at time t for the ith wheel, i = 1,2,

   Wi(t) is the actual rotational velocity of the ith wheel,

   p(in) is a parameter or signal indicative of braking effort scaled approximately as a deceleration. This parameter may be viewed as a nominal deceleration command signal.

The combination scale factor (ABSGi+Gi) scales the nominal deceleration command signal to achieve a per wheel deceleration command p(in)(ABSGi+Gi) for each wheel. ABSGi is a variable gain factor increment used to adjust the rate of change or deceleration of the wheel velocity command signal during the antilock braking mode of operation. The parameter ABSGi is defined as zero when the braking system 10 is in its normal braking mode of operation. The parameter Gi is an additional gain factor used to adjust the rate of change or deceleration of the vehicle command signal during the normal braking mode of operation (straight ahead braking or braking in a turn).

In the preferred embodiment of the invention the microcontroller 20 is a sampled data device which samples various input parameters at sampling increments n, n+1, n+2, etc. and generates a corresponding plurality of signals. The wheel velocity command signals shown in FIGURE 1 can be implemented in such microcontroller 20 by utilizing equations 2 and 3.



Wci(0)=Wi(0)   (2)



Wci(n)=+p(in)*(ABSGi+Gi)+ Wci(n-1)   (3)



   With regard to equation 2, the variable Wci(0) is the initialized value of the ith wheel velocity command signal which is initialized to the value of the initial measured velocity of the ith wheel, i.e., Wi(0) each time the pedal is depressed. Thereafter, the wheel velocity command signal at any sample period n is given by equation 3 which may be generated within a register within the micro- controller 20 in a known manner. Thereafter and as diagramatically illustrated in FIGURE 1, an error signal E is generated for each wheel (i=1,2) for each set of wheel velocity parameters in accordance with equation 4.



Ei(n)=Wci(n) - Wi(n)   (4)



A braking activity signal Bi as mentioned above, is generated for each wheel. This signal may be thought of as a brake force command, brake torque command, pressure command, etc. Some appropriate scaling may be required. In the preferred embodiment of the invention, the braking activity signal Bi is obtained by operating on the error signal associated with each wheel, by a proportional, integral, differential controller (PID) which is diagramatically shown by equation 5.



Bi=[PID CONTROLLER] x Ei(n)   (5)



More specifically, the actual brake activity signal Bi as a result of the use of the PID controller is implemented utilizing the scheme shown in equations 6a and 6b wherein PK, DK and IK are constants of proportionality respectively associated with a term proportional to the error signal, its derivative and summation or integral value.



Bi=Ei(n)*PK + [Ei(n)-Ei(n-1)]*DK + Ei(n)*IK   (6a)



Bi=[Wci(n)-Wi(n)]*PK + [Wci(n-1) - Wi(n-1)]*DK + [E(n)]*IK   (6b)



   Reference is made to FIGURE 3 which shows a stop action moment in time and illustrates a situation where the wheel velocities of one of the sets of wheels (W&sub1;, W&sub2;) are different. This figure will be useful in illustrating how the gain factor Gi is obtained for straight line braking. It also illustrates how the present invention allows for the differing wheel speeds resulting from different sized tires and will also be useful in illustrating in how the present invention allows for differing wheel speeds when negotiating a bend or corner during normal braking operation. For whatever reason, at time T0, the wheel speeds W&sub1; and W&sub2; are of differing rates. The present invention envisions that the microcontroller 20, upon receipt of a brake activation signal (at time T0), will interrogate the wheel speed velocities W&sub1; and W&sub2;. Thereafter the microcontroller will generate the gain factor Gi associated with each wheel to appropriately adjust the deceleration (slope of the wheel velocity command) of each wheel such that each wheel will reach zero speed simultaneously. Returning to equation 3, and assuming for the moment that the gain factor ABSGi is zero, that is none of the wheels are in the antilock mode of operation, and recalling that the command signal p(in) is a braking effort signal scaled in terms of deceleration which would yield a desired nominal deceleration of the vehicle. In view of the above the microcontroller 20 will extrapolate the wheel speeds from the initial stored velocities Wi(0) to zero speed in the following manner. With regard to the wheel exhibiting the slowest rotational wheel velocity at time T0 the microcontroller 20 will extrapolate or decrement the initial wheel speed velocity of the slowest wheel W&sub1;(0) to zero at a rate which is generally equal to p(in) x G1 wherein G1 for the slowest wheel is equal to a constant K1. In the preferred embodiment of the invention the constant K1 is equal to 1. This extrapolation to zero at the above constant deceleration rate of p(in)xG1 is shown in FIGURE 3. Thereafter the microcontroller determines a preferred deceleration rate for the higher rotating wheel, i.e., W&sub2;, such that its velocity would reach zero speed simultaneously with that of the extrapolated value for W&sub1;. The adjusted deceleration rate for the higher speed wheel W&sub2; is also diagramatically shown in FIGURE 3 as p(in) G&sub2;. The above adjustment in the deceleration can be accomplished in a straightforward manner by permitting the gain factor G2 to be equal to



G2=[W&sub2;(0)/W&sub1;(0)]*G&sub1;   (7)



These gain factors are recalculated each time the pedal is depressed. In view of the above, the microcontroller has now established the command rate at which any particular wheel should decelerate during the normal braking mode of operation, this value being equal to p(in)*Gi.

Consider the dynamics of braking which occurs in a conventional hydraulically braked vehicle as the vehicle is negotiating a turn. When a vehicle is in a turn, the outside wheel, for example the left front wheel, of FIGURE 2, will rotate faster than the right front wheel. In addition because of the vehicle's weight transfer during the turn, the left front brake will typically be capable of generating a greater braking force at the tire/road interface than will the right front brake. This imbalance in braking forces may ultimately tend to destabilize the vehicle during an aggressive turn or accident avoidance maneuver. It is a design goal to achieve a brake system that yields a balance between the right and left hand braking forces while the vehicle is in a turn. This goal, however, is not often realized. This deficiency is addressed and solved by the present invention in the following manner. The microcontroller 20 first determines an index relating to the brake balance between for example the front left and front right wheels. If this index is greater than a threshold value, corrective action is taken to correct the brake balance. This is accomplished by determining an index value which is equal to the absolute difference between the right and left side brake activity commands in accordance with equation 8 below.



B&sub1; - B&sub2; > BT   (8)



wherein B&sub1; is the brake activity signal associated with one wheel, B&sub2; the brake activity associated with a second wheel and BT a threshold value. While the brake activity command signals Bi have been used in equation 8, it should be apparent that a measure of the brake activity, brake force, brake application, etc., can also be achieved by measuring the actual developed pressure in a hydraulic system or alternatively if an electrically braked system were used, the measurement of motor current, brake torque, etc., alternatively the position of the jack screw 34, can be used.

If the absolute value of the differences in the brake activity signals as defined in equation 8 is less than the threshold value BT, then one can assume the wheels are essentially operating in a balanced brake mode of operation. Further, if one is attempting to maintain a left/right brake balance in the vehicle during a turning maneuver, then one needs information to indicate to the microcontroller 20 that the vehicle has in fact begun such a turning maneuver. It is not desirable to monitor the position of the steering wheel or the tires themselves since this requires additional sensors and electronics, resulting in an increased cost of the system. In the present invention, however, the initiation of a turn is obtained implicitly by monitoring the brake activity command signals Bi (or alternatively any of the above mentioned feedback signals: pressure, position, torque, current, etc.). If the brake activity command such as B&sub1; of one wheel is increasing and if the brake activity command of the other wheel such as B&sub2; is decreasing as it normally will during a turning maneuver, then the gain factor Gi associated with each wheel will be modified to adjust the commanded deceleration (p(in)Gi) of that wheel. More specifically, the gain factor Gi associated with the wheel having a decreasing brake actuator command Bi is incremented while the gain factor associated with the wheel exhibiting an increasing brake activity command is decremented. This process is shown below in equation 9.



Gi(n)=Gi(n-1)*K + Gi(n-1)   (9)



wherein Gi(n) is the current gain factor, Gi(n-1) is the old value of the gain factor and K is a constant of proportionality or an incremental index which will be a positive and negative value as the case may be. If K is a positive value then the appropriate gain factor Gi will increase or be incremented and if K is a negative quantity then the gain factor Gi will be decremented. As can be appreciated, by modifying the gain factor Gi of the appropriate wheel, its desired rate of change or deceleration p(in)*Gi will appropriately increase or decrease, thereby resulting in a relative increase or decrease in the brake activity signal which will ultimately yield a more balanced braking condition while negotiating a turn.

Reference is made to FIGURE 4 which illustrates the wheel velocity command signal WC1 (in solid line) and actual wheel speed (in fragmented line). As can be seen from this FIGURE, the slope or commanded deceleration of the wheel velocity reference signal is p(in)G1. During normal brake operation it is anticipated that the actual wheel speed will only deviate marginally from the commanded velocity.

Having determined the gain factor indices Gi which essentially define the desired or recommended rate of change or decleration of each wheel during straightline braking and during a turning maneuver, it is now desirable to determine whether or not any particular wheel should be under antilock control. This is done by determining whether the deceleration ai of any wheel has exceeded its desired commanded deceleration by a given increment or threshold ABSTi as shown in equation 10.



Ai>Gi*p(in)*k&sub2; = GixK&sub2; = ABSTi   (10)



wherein k&sub2; is a scale factor greater than 1 and K&sub2; equals the product of the brake effort or deceleration command p(in) x constant k&sub2;. k&sub2; is typically in the range of 1.05 to 1.1.

In a microcontroller which calculates the various parameters over a known sampling increment, a value of the actual wheel acceleration ai can be obtained from a comparison of wheel velocity signals as generated by the wheel speed sensor 44 as shown in equation 11.



ai=Wi(n) - Wi(n-1)   (11 )



Reference is again made to FIGURE 4 which shows one of the wheels entering a skid condition. On inspection of the wheel velocity curve W&sub1;, one can see that the actual deceleration of this curve exceeds the desired deceleration p(in)*G&sub1; by an amount for the purpose of illustration, which is greater than the deceleration threshold value ABST&sub1;. This situation is indicative of the fact that the commanded brake activity command for this particular wheel is greater than the forces which can be generated at the tire/road interface causing an increased deceleration (negative acceleration) of the wheel in excess of the desired or commanded value. In this condition the wheel is tending toward lock-up. To bring this wheel under control it is desirable to decrease the brake actuation or activity force. This is done by commanding a less aggressive deceleration command for that particular wheel. This is accomplished in concert with equation 3 by modifying the gain factor ABSGi to decrease the slope of the commanded deceleration. This is achieved by generating a recurring index within the microcontroller in accordance with equation 12 as shown below:



ABSGi(n) = ai + ABSGi(n-1)   (12)



wherein ABSGi(n) is the new value of this parameter and ABSGi(n-1) is the prior or old value of this parameter. As can be seen from FIGURE 4 and equation 12 with the wheel decelerating rapidly, the new value of the gain factor ABSGi(n) will be a quantity which when added to the gain factor term Gi will decrease the slope of the commanded deceleration as shown in the interval subsequent to time t2 or sampling event n2. As such it can be seen that the commanded change in velocity of the wheel or its commanded deceleration has decreased (the slope of the curve has decreased) which in turn will cause for a smaller brake activity command Bi or reduced the brake activity or brake force applied to the brake 30. Subsequently, the wheel will begin to accelerate at some point in time such as t3 after the braking forces on the wheel have been sufficiently reduced. When the indexed value ABSGi(n) is again zero the normal braking mode of operation is entered and the factor ABSGi is maintained at zero until it is determined that the actual wheel deceleration exceeds the threshold value as described above whereupon the antilock lock mode of operations is again entered.

As can be seen, the antilock behavior of any particular wheel has been altered by modifying the reference deceleration command to a value less than that which would be commanded by the operator. Subsequently, the brake activity force is modified to allow the previously skidding wheel to reaccelerate to a speed nearly synchronous with that of the vehicle speed.

In view of the above, it can bee seen that the present invention provides for an automatic proportioning, that is each wheel will automatically do its share of braking. The proportioning achieved by the present invention is idependent of vehicle loading or load distribution. Control of any of the wheels in an antilock braking mode of application is implemented with minimal additional cost.

Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, that scope is intended to be limited only by the scope of the appended claims.


Anspruch[de]
  1. Verfahren zum Steuern des Bremsverhaltens verschiedener Räder eines Fahrzeuges in normaler Bremsbetriebsart und in Antiblockierbremsbetriebsart, wobei das Verfahren ein Steuergerät verwendet, das verschiedene Parameter in einem bekannten Zeitinkrement (t-t&sub1;) bzw. Δt berechnet, das als ein bekannter, auf Zeit basierender Skalierungsfaktor betrachtet wird, mit folgenden Schritten:
    • 1.1 ein Wert für den Drehgeschwindigkeits-Istwert jedes Rades (W&sub1;, W&sub2;) wird erfaßt;
    • 1.2 ein erster Signalwert wird erzeugt, der eine Bremskraft P (in) bzw. einen Fahrzeugsverzögerungs-Sollwert angibt;
    dadurch gekennzeichnet, daß das Verfahren folgende Schritte aufweist:
    • 1.3 pro Rad wird ein Radgeschwindigkeitsbefehlssignal erzeugt, dessen Abfall bzw. Verzögerung dem Fahrzeugverzögerungs-Sollwert p(in) proportional ist, sowie ein multiplikativer Skalierungsfaktor (ABSG&sub1; + G&sub1;) zum Einstellen dieser Verzögerung in der normalen Bremsbetriebsart und in der Antiblockierbremsbetriebsart;
    • 1.4 pro Rad wird ein Fehlersignal Ei als Differenz zwischen dem Radgeschwindigkeitsbefehl und dem Drehgeschwindigkeits-Istwert jedes Rades erzeugt;
    • 1.5 das Fehlersignal Ei wird verarbeitet, um ein Bremsbetätigungsbefehlssignal Bi zu erzeugen;
    • 1.6 die Bremskraft wird gemäß dem Bremsbetätigungsbefehlssignal Bi reguliert.
  2. Verfahren nach Anspruch 1, bei dem der Schritt 1.3 beinhaltet:
    • 2.1 das Radgeschwindigsreferenzbefehlssignal wird gemäß



      Wci(0) = Wi(0) und

      Wci(n) = +p(in)*(ABSGi+Gi) + Wci(n-1) erzeugt,



      wobei ABSGi ein variables Verstärkungsfaktorinkrement ist, um die Änderungsgeschwindigkeit bzw. Verzögerung des Geschwindigkeitsbefehlssignals in der Antiblockierbremsbetriebsart zu definieren, wobei der Wert gleich 0 für das normale Bremsen ist, und

      Gi ist ein Verstärkungsfaktor, der die Änderungsgeschwindigkeit bzw. Verzögerung des Geschwindigkeitsbefehlssignals beim normalen Bremsen Wci(t) definiert mit dem Radbefehlssignal als Abtastung n.
  3. Verfahren nach Anspruch 2, bei dem Schritt 2.1 beinhaltet:
    • 3.1 ein anfänglicher Wert der Radgeschwindigkeit Wi(0) für jedes Rad entsprechend dem Anfang des ersten Signals p(in) wird bestimmt,
    • 3.2 die anfängliche Radgeschwindigkeit jedes Rades ausgehend von dem Anfangswert Wi(0) nach der Drehzahl Null (Wi=0) wird derart extrapoliert, daß die extrapolierten Werte die Null-Drehzahl gleichzeitig erreichen, um den zugehörigen Verstärkungsfaktor Gi für jedes Rad zu bestimmten.
  4. Verfahren nach Anspruch 3, bei dem der Schritt 3.2 beinhaltet, daß die Verstärkungsfaktoren Gi definiert werden, wobei G&sub1; gleich k und G&sub2; = [W&sub2;(0)/W&sub1;(0)]*G&sub1; ist.
  5. Verfahren nach Anspruch 4, wobei die feste Konstante k gleich 1 ist.
  6. Verfahren nach Anspruch 1 mit folgenden Schritten:
    • 6.1 der Bremsbetätigungsbefehl wird variiert, um das Bremsgleichgewicht von Seite zu Seite einzustellen, wenn das Fahrzeug eine Kurve fährt, wobei Schritt 6.1 folgende Schritte beinhaltet:
      • 6.1.1 der Bremsbetätigungsbefehl Bi für einander gegenüberliegende Räder wird überwacht,
      • 6.1.2 es wird bestimmt, ob der Absolutwert der Differenz zwischen den Bremsbefehlen B&sub1;, B&sub2; pro Rad größer ist als ein Schwellwert BT,
      • 6.1.3 es wird bestimmt, ob der Bremskraftbefehl B&sub1; für ein Rad ansteigt, und ob der Bremskraftbefehl B&sub2; für das andere Rad abfällt,
      • 6.1.4 wenn die Bedingungen in den Schritten 6.1.2 und 6.1.3 erfüllt sind, wird der Verstärkungsfaktor Gi für das Rad mit dem abfallenden Bremsbetätigungsbefehl Bi inkrementiert und der Verstärkungsfaktor Gi für das Rad mit dem ansteigenden Bremsbetätigungsbefehl Bi dekrementiert.
  7. Verfahren nach Anspruch 6, bei dem die Verstärkungsfaktoren Gi um gleiche Beträge inkrementiert oder dekrementiert werden.
  8. Verfahren nach Anspruch 1 mit folgendem Schritt:
    • 8.1 es wird bestimmt, ob ein bestimmtes Rad in Antiblockiersteuerung gebremst werden soll, indem man feststellt, ob der Istwert der Radverzögerung den Sollwert der Verzögerung des Radgeschwindigkeitsbefehlssignals um einen Schwellwert ABSTi überschreitet.
  9. Verfahren nach Anspruch 8, bei dem der Schritt 8.1 beinhaltet:
    • 9.1 es wird bestimmt, ob eine Radverzögerung den Verzögerungsschwellwert ABSTi überschritten hat, worauf die Änderungsgeschwindigkeit oder Verzögerung des Geschwindigkeitsbefehlssignals Wci durch Modifizieren des ABSGi-Verstärkungsfaktorinkrementes derart variiert, daß



      ABSGi(n) = ai + ABSGi (n-1).
  10. Verfahren nach Anspruch 9 mit folgendem Schritt:
    • 10.1 die normale Bremsbetriebsart wird wieder aufgenommen, wenn ABSGi=0.
Anspruch[en]
  1. A method of controlling the braking behaviour of various wheels of a vehicle during a normal braking mode of operation and during an antilock braking mode of operation, the method using a control unit which calculates various parameters over a known time increment (t-t&sub1;) or Δt which may be considered as a known time based scale factor, the method including the steps of :
    • 1.1 obtaining a value of the actual rotational velocity of each wheel (W&sub1;, W&sub2;) ;
    • 1.2 generating a first signal indicative of braking effort P (in) or desired vehicle deceleration ;

         characterized in that the method includes the steps of :
    • 1.3 generating a per wheel velocity command signal the slope or deceleration of which is proportional to the desired vehicle deceleration p (in), and a multiplicative scale factor (ABSG&sub1; + G&sub1;) for adjusting such deceleration during the normal braking mode and antilock braking mode,
    • 1.4 generating a per wheel error signal Ei as a difference between the wheel velocity command and actual rotational velocity of each wheel,
    • 1.5 operating upon the error signal Ei to generate a brake activity command signal Bi,
    • 1.6 regulating brake force in response to the brake activity command signal B&sub1;.
  2. The method as defined in Claim 1 wherein the step 1.3 includes
    • 2.1 generating the wheel velocity reference command signal in accordance with the following



      Wci(0)=Wi(0) and

      Wci(n)=+p(in)*(ABSGi+Gi)+ Wci(n-1)



         wherein ABSGi is a variable gain factor increment to define the rate of change or deceleration of the velocity command signal wherein antilock braking and has a value of zero when in normal braking and

         Gi is a gain factor used to define the rate of change or deceleration of the velocity command signal during normal braking Wci(t) is the wheel command signal as sample n.
  3. The method as defined in Claim 2 wherein step 2.1 includes:
    • 3.1 determining an initial value of wheel velocity Wi(0) for each wheel corresponding to the beginning of the first signal p(in),
    • 3.2 extrapolating the initial wheel velocity of each wheel from the initial value Wi(0) to zero speed (Wi=0) such that the extrapolated values reach zero speed simultaneously to determine the respective gain factor Gi for each wheel.
  4. The method as defined in Claim 3 wherein the step 3.2 includes defining the gain factors Gi, wherein G&sub1; equals k and G&sub2; equals [W&sub2;(0)/W&sub1;(0)]*G&sub1; .
  5. The method as defined in Claim 4 wherein the fixed constant k equals 1.
  6. The method as defined in Claim 1 including the steps of:
    • 6.1 varying the brake actuation command to adjust the side to side braking balance when the vehicle is negotiating a turn, wherein step 6.1 includes the steps of:
      • 6.1.1 monitoring the brake actuator command Bi for opposing wheels;
      • 6.1.2 determining if the absolute value of the difference in the per wheel brake commands B&sub1;, B&sub2; is greater than a threshold value BT;
      • 6.1.3 determining if the brake force command B&sub1; for one wheel is increasing and if the brake force command B&sub2; for the other wheel is decreasing;
      • 6.1.4 if the conditions in step 6.1.2 and 6.1.3 are satisfied, incrementing the gain factor Gi associated with the wheel having a decreasing brake actuator command Bi and decrementing the gain factor Gi associated with the wheel having an increasing brake actuator command Bi.
  7. The method as defined in Claim 6 wherein the gain factors Gi are incremented or decremented by the same amount.
  8. The method as defined in Claim 1 including the step of
    • 8.1 determining whether or not any particular wheel should be under antilock control by determining if its actual wheel deceleration ai has exceeded the desired deceleration of the wheel velocity command signal by a threshold value ABSTi.
  9. The method as defined in Claim 8 wherein step 8.1 includes
    • 9.1 determining if any wheel deceleration has exceeded the deceleration threshold value ABSTi, then varying the rate of change or deceleration of the velocity command signal Wci by modifying the ABSGi gain factor increment such that



      ABSGi(n) = ai + ABSGi(n-1).
  10. The method as defined in Claim 9 including the step of
    • 10.1 resuming the normal braking mode when ABSGi=0.
Anspruch[fr]
  1. Méthode de commande du comportement de freinage des différentes roues d'un véhicule pendant le mode de fonctionnement de freinage normal et pendant le mode de fonctionnement de freinage antiblocage , utilisant une unité de commande qui calcule les différents paramètres sur une augmentation de temps connue (t-t&sub1;) ou Δt qui peut être considérée comme facteur de graduation basé sur le temps connu, cette méthode comprenant les étapes suivantes :
    • 1.1 obtention de la vitesse de rotation réelle de chaque roue (W&sub1; ,W&sub2;) ;
    • 1.2 production d'un premier signal indiquant l'effort de freinage P (in) ou décélération désirée du véhicule,

         caractérisée en ce que cette méthode inclut les étapes de:
    • 1.3 production d'un signal de commande de vitesse par roue dont la pente de décélération est proportionnelle à la décélération p(in) par roue désirée , et un facteur de graduation multiplicateur (ABSG&sub1;+ G&sub1;) pour régler cette décélération pendant le mode de foncctionnement normal de freinage et pendant le mode de freinage antiblocage,
    • 1.4 production d'un signal d'erreur par roue Ei comme différence entre la commande de vitesse de roue et la vitesse de rotation réelle de chaque roue ,
    • 1.5 commande du signal d'erreur Ei pour obtenir un signal de commande d'activité Bi du frein,
    • 1.6 régulation de la force de freinage en réponse au signal de commande d'activité du frein B&sub1;.
  2. Méthode selon la revendication 1 dans laquelle l'étape 1.3 inclut :
    • 2.1 la production d'un signal de commande de référence de vitesse de roue en conformité avec la relation suivante :



      Wci(0) = Wi(0) et

      W i(n) = +p (in)* (ABSG + G) + Wci(n-1)



      dans lesquelles ABSG est un accroissement du facteur de gain variable du taux de variation de la décélération du signal de commande de vitesse dans lequel le freinage antiblocagea a une valeur de zéro en freinage normal et

         Gi est un facteur de gain utilisé pour définir le taux de variation ou décélération du signal de commande de vitesse pendant qye le freinage normal Wci(t) est le signal de commande de roue comme l'échantillon n.
  3. Méthode selon la revendication 2 dans laquelle l'étape 2.1 inclut
    • 3.1 la détermination d'une valeur initiale de la vitesse de la roue Wi(0) pour chaque roue correspondant au commencement du premier signal p(in),
    • 3.2 l'extrapolation de la vitesse initiale de chaque roue de la valeur initiale Wi(0) à la vitesse zéro (Wi = 0) telle que les valeurs extrápolées atteignent la vitesse zéro simultanément pour déterminer le facteur de gain respectif Gi pour chaque roue.
  4. Méthode selon la revendication 3 dans laquelle l'étape 3.2 inclut la définition des facteurs de gain Gi, dans laquelle G&sub1; égale k et G&sub2; égale (W&sub2;(0) / W&sub1; (0) )*G
  5. Méthode selon la revendication 4 dans laquelle la constante fixe k égale 1.
  6. Méthode selon la revendication 1 incluant les étapes suivantes consistant :
    • 6.1 à faire varier la commande d'actionnement du frein pour régler l'équilibre de freinage côte à côte lorsque le véhicule négocie un tournant, dans lequel l'étape 61 inclut les étapes consistant :
      • 6.1.1 à controler la commande d'actionnement de frein Bi pour les roues opposées;
      • 6.1.2 à déterminer si la valeur absolue de la différence dans les commandes de frein par roue B&sub1;, B&sub2; est supérieur à la valeur de seuil BT;
      • 6.1.3 à déterminer si la commande de force de frein B&sub1; pour une roue augmente et si la commande de force de frein B&sub2;pour l'autre roue diminue;
      • 6.1.4 si les conditions des étapes 6.1.2 et 6.1.3 sont satisfaites, à incrémenter le facteur de gain Gi associé à la roue ayant une commande d'actionnement de frein décroissante Bi et à décrementer le facteur de gain Gi associé à la roue ayant une commande d'actionnement de frein croissante Bi.
  7. Méthode selon la revendication 6 dans laquelle les facteurs de gain G&sub1;sont incrémentés ou décrémentés de la même valeur.
  8. Méthode selon la revendication 1 incluant l'étape consistant à
    • 8.1 déterminer si une roue particulière devrait être ou non sous commande antiblocage en déterminant si sa décélération réelle a&sub1; a dépassé la décélération désirée du signal de commande de vitesse de la roue d'une valeur de seuil ABST.
  9. Méthode selon la revendication 8 dans laquelle l'étape 8.1 consiste à
    • 9.1 déterminer si la décélération d'une roue a dépassé la valeur de seuil de décélération ABSG, puis à faire varier le taux ou décélération du signal de commande de vitesse Wci en modifiant l'incrément de facteur de gain ABSG tel que



      ABSG&sub1;(n) = ai + ABSG &sub1; (n-1).
  10. Méthode selon la revendication 9 incluant l'étape consistant à
    • 10.1 reprendre le mode de freinage normal lorsque ABSGi= 0.






IPC
A Täglicher Lebensbedarf
B Arbeitsverfahren; Transportieren
C Chemie; Hüttenwesen
D Textilien; Papier
E Bauwesen; Erdbohren; Bergbau
F Maschinenbau; Beleuchtung; Heizung; Waffen; Sprengen
G Physik
H Elektrotechnik

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