WO2008063120A1

WO2008063120A1 - Adaptive brake control

Info

Publication number: WO2008063120A1
Application number: PCT/SE2007/050809
Authority: WO
Inventors: Magnus GRANSTRÖM
Original assignee: Scania Cv Ab
Priority date: 2006-11-22
Filing date: 2007-11-01
Publication date: 2008-05-29
Also published as: SE0602484L

Abstract

The present invention relates to a brake control solution for a motor vehicle (100), wherein at least one brake means (110) is adapted to apply a brake force to at least one wheel (120) of the vehicle (100) in response to reference signal (sref ). A control unit (130) receives: an operator-generated input signal (s man ) describing a desired brake force to be applied to the at least one wheel (120); an automatically generated antilock control signal (sABS) describing a brake force to be applied to the at least one wheel (120) to avoid locking thereof; and a steering signal (sα) indicative a steering wheel angle (α) of the vehicle (100). In response to the received signals (sm an, sABS, sα), the control unit (130) produces the reference signal (sref ), such that the brake force specified by this signal is derived in consideration of antilock criteria as well as a handling parameter (f h ) comprising a first directional control component reflecting the steering wheel angle (α). Thus, any steering wheel maneuvers performed during ABS-assisted braking influence the behavior of the at least one brake means (110) in a positive manner regarding vehicle handling.

Description

Adaptive Brake Control

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates generally to adaptive braking systems and safety solutions concerning vehicle handling. More particularly the invention relates to a brake control system according to the preamble of claim 1 and a motor vehicle according to claim 9. The invention also relates to a method of controlling at least one brake means of a motor vehicle according to the preamble of claim 10, a computer program according to claim 18 and a computer program product according to claim 19.

Modern vehicles are often equipped with adaptive and relatively advanced brake systems. It is especially important that the brake systems of heavy vehicles, such as trucks, busses and tractors be flexible, since these vehicles are often driven on proble- matic surfaces. Moreover, the axle pressures may here vary substantially over time. Therefore, particular considerations are required to ensure stability when braking these types of vehicles. To this aim, sophisticated antilock brake systems (ABSs) may be included.

US 6,318,820 describes an antilock control method for so-called μ-split surfaces, i.e. wherein the right and the left wheels of the same axle experience different coefficient of friction. Here, the antilock control involves controlling the brake pressure in cycles; such that the higher coefficient of friction is utilized as efficiently as possible.

US 2001/0002770 discloses a braking force control system wherein a vehicle body slip angular velocity is calculated. This parameter, in turn, forms a basis for correcting an actual steering angle. Thereby, a brake control is enabled, which provides an enhanced vehicle handling on slippery roads.

FR 2 861 043 describes a vehicle steering device having a calculation unit for determining a time-derivative of a difference between measured and calculated wheel angles. A counter-lock of the front wheels is here accepted if the value of the derivative is smaller than a predetermined threshold during a predetermined duration.

However, there is yet no antilock brake solution that provides satisfying vehicle stability when braking hard while subjecting the vehicle to handling maneuvers.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a so- lution, which mitigates the problem above, and thus offers a reliable braking solution capable of efficiently retarding a vehicle while maintaining good handling of the vehicle also on problematic surfaces.

According to one aspect of the invention, the object is achieved by the initially described system, wherein the control unit is adapted to control the at least one brake means on the further basis of the handling parameter exclusively if a handling criterion is fulfilled. This criterion, in turn, is fulfilled if: at least one of a threshold steering wheel angle and a threshold steering wheel angle time derivative is exceeded; and the threshold steering wheel angle and/or the threshold steering wheel angle time derivative are/is exceeded after that the control unit has initiated reception of the antilock control signal.

This system is advantageous in that it strikes a good balance between short brake distance and superlative vehicle handling. At the same time, the brake control procedure can be simplified whenever the vehicle travels essentially straight. Moreover, handling compensation can be avoided in cases when this is actually unnecessary. For example, any ABS-assisted braking which is instigated when the vehicle is in the course of passing a sharp corner does not risk to become overcompensated.

According to one embodiment of this aspect of the invention, the handling parameter represents a factor larger than zero, and smaller than or equal to one. The control unit is here adapted to investigate whether or not the antilock control signal is received. If this is found to be the case, the control unit is adapted to produce the reference signal to the at least one brake means by multiplying the antilock control signal with the handling parame- ter. Otherwise, the control unit is adapted to set the reference signal equal to the operator-generator input signal. Hence, a straightforward and uncomplicated steering-wheel adjustment of the brake force is attained.

Preferably, the control unit is adapted to produce the handling parameter such that a relatively large steering wheel angle results in a comparatively small handling-parameter value, and conversely, a relatively small steering wheel angle results in a comparatively large handling-parameter value.

According to another embodiment of this aspect of the invention, the control unit is adapted to perform low-pass filtering of the steering wheel angle. Furthermore, the first directional component includes a low-pass filtered representation of the steering wheel angle. Thus, the brake control becomes more stable.

According to yet another embodiment of this aspect of the inven- tion, the handling parameter further comprises a second directional control component reflecting a time derivative of the steering wheel angle. The control unit is here preferably adapted to produce the handling parameter such that a relatively large time- derivative value results in a comparatively small handling-para- meter value, and conversely, a relatively small time-derivative value results in a comparatively large handling-parameter value. Thus, also the speed of the steering wheel maneuvers can be weighed into the brake control algorithm in straightforward and uncomplicated manner.

According to a further embodiment of this aspect of the invention, the control unit is adapted to perform low-pass filtering of the time derivative of the steering wheel angle. Moreover, the second directional component includes a low-pass filtered representation of the time derivative of the steering wheel angle. Thereby, the stability of the brake control is improved. According to still another embodiment of this aspect of the invention, the reference signal expresses: a brake pressure to be applied by the at least one brake means, a target slip value in respect of the at least one wheel or a target retardation of the vehicle. Namely, the proposed system is generally applicable irrespective of the specific nature of the brake control signal. Of course, this provides a high degree of flexibility.

According to another aspect of the invention, the object is achieved by a motor vehicle, which includes the above-proposed sys- tern.

According to still another aspect of the invention, the object is achieved by the method described initially, wherein the method involves controlling the at least one brake means on the further basis of the handling parameter exclusively if a handling crite- rion is fulfilled. This criterion is fulfilled if: at least one of a threshold steering wheel angle and a threshold steering wheel angle time derivative is exceeded; and the threshold steering wheel angle and/or the threshold steering wheel angle time derivative are/is exceeded after that the control unit has initiated reception of the antilock control signal. The advantages of this method, as well as the preferred embodiments thereof, are apparent from the discussion hereinabove with reference to the proposed vehicle arrangement.

According to a further aspect of the invention the object is achieved by a computer program directly loadable into the internal memory of a computer, comprising software for controlling the above proposed method when said program is run on a computer.

According to another aspect of the invention the object is achie- ved by a computer program product, having a program recorded thereon, where the program is to make a computer control the above proposed method.

Further advantages, advantageous features and applications of the present invention will be apparent from the following des- cription and the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by means of embodiments, which are disclosed as examples, and with reference to the attached drawings. Figure 1 schematically shows a brake control system according to one embodiment of the invention,

Figure 2 depicts a diagram exemplifying typical relationships between retardation forces and lateral forces applicable when handling a motor vehicle, Figure 3 depicts a diagram illustrating a reference signal as a function of time for controlling a brake means according to one embodiment of the invention, and

Figure 4 shows a flow diagram illustrating the method ac- cording to one embodiment of the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Initially, we refer to Figure 1 , which shows a block diagram over a brake control system according to one embodiment of the invention. The system is included in a motor vehicle 100, e.g. an automobile, a truck, a bus or a tractor, and the system is adapted to control at least one brake means 1 10 of the vehicle 100, such that a given brake force is applied to at least one of the vehicle's wheels 120.

The system, in turn, includes a control unit 130 and a sensor means 140. The sensor means 140 is adapted to register a steering signal s_α indicative a steering wheel angle α of the vehicle 100.

The control unit 130 is adapted to receive an operator-generated input signal s_man describing a desired brake force to be applied to the at least one wheel 120 of the vehicle 100. I.e. the input signal s_man typically reflects the driver's intended braking of the vehicle 100. The control unit 130 is also adapted to receive an automatically generated antilock control signal S_{ABS >} which describes a brake force to be applied to the at least one wheel 120 in order to avoid locking of the at least one wheel 120. Consequently, the antilock control signal S_ABS may originate from a per se known ABS unit (not shown). Moreover, the cont- rol unit 130 is adapted to receive the steering signal s_α from the sensor means 140.

The control unit 130 is adapted to produce a reference signal s_rΘf based on the input signal s_man and the antilock control signal S_ABS, such that a magnitude of the reference signal s_rΘf is deli- mited by whichever of the input signal s_man the antilock control signal S_ABS that represents a smallest brake force to be applied. The control unit 130 is also adapted to produce a handling parameter f_h including a first directional control component that reflects the steering wheel angle α. Thus, when at least one handling criterion is fulfilled, the control unit 130 is further adapted to produce the reference signal s_rΘf based on the handling parameter f_h. This results in that the at least one brake means 1 10 is controlled, such that a brake force is applied to the at least one wheel 120 in consideration of antilock criteria as well as vehicle handling criteria.

It is further advantageous if the control unit 130 includes, or is associated with, a computer readable medium 135, which has a program recorded thereon; where the program is adapted to make the unit 130 control the above-described procedure.

Preferably, the handling parameter f_h represents a factor larger than zero, and smaller than or equal to one (i.e. 0 < f_h ≤ 1 ). In such a case, the control unit 130 is adapted to produce the reference signal s_rΘf, so that:

(a) the reference signal s_rΘf is equal to the input signal s_man (if neither the antilock criteria nor the vehicle handling criteria are fulfilled),

(b) s_rΘf is equal to the antilock control signal S_ABS if the anti- lock control signal S_ABS is present, however the vehicle handling criteria are not fulfilled), or (c) s_rΘf is equal to s_ABs-fh if both the antilock and the vehicle handling criteria are fulfilled).

SABs-fh ≤ SABS, since 0 < f_h ≤ 1 . Whenever the antilock control signal S_ABS is present, it is normally also true that S_ABS < s_man- These relationships will be further elucidated below with referen- ce to Figures 2 and 3.

Figure 2 depicts a diagram that exemplifies a simplified relationship between a retardation force μ_rΘt and a lateral force μι_at, which are applicable when handling a motor vehicle during braking. The vertical axis indicates the friction force μ, and the hori- zontal axis shows a slip value s. The slip for a wheel 120 of a vehicle 100 is normally defined as (see Figure 1 ): v — v s = ^ *-

V, where v_v is the speed of the vehicle 100, and v_w is the speed of the wheel 120 in question.

Thus, the slip s = 0 for a free-rolling wheel, and s = 1 for a completely locked wheel.

An ABS is typically designed such that if wheel locking is detected during braking, the slip value s is allocated a new value in order to avoid such locking. The slip value s preferably depends on the currently estimated conditions, e.g. involving vehicle speed and road conditions. However generally, the slip value s is determined as: s=min(s_man, S_AB_S) where s_man is a slip value derived from a driver input, e.g. the force with which the braking pedal is depressed, and

S_ABS is the slip value calculated by the ABS.

Naturally, a maximum retardation is attained for slip values s around the peak slip value s_A, i.e. where the retardation force μ_rΘt is maximal μ_ret-A- However, as can be seen in Figure 2, the lateral friction force μι_at__A is here relatively low. This may lead to severe stability problems, especially if the vehicle is subjected to handling, i.e. performs a maneuver transverse to its direction of motion. Typically, this means that the vehicle passes a corner, or swerves.

The rationale behind the present invention is therefore to adjust the slip value s from the prima facie optimal s_A-point along a line A towards lower slip values s (as indicated by the arrows), if it is estimated that vehicle handling occurs during the brake procedure. The lower slip values s may be represented by s_B or s_c along the lines B and C respectively. At the slip value s_B the re- tardation force μ_ret-B is lower than the value μ_ret-A applicable at the slip value s_A, and at the slip value s_c the retardation force μ_rΘt-c is even lower. However, for these the slip values s_B and s_c, the corresponding lateral friction forces μ,_at-B and μι_at._c respectively are considerably higher than the lateral friction force μι_at-_A at the slip value s_A.

According to the invention, steering wheel maneuvers are used as indicators of vehicle handling. Therefore, a steering wheel angle α of the vehicle 100 is repeatedly registered, and the reference signal s_rΘf to the brake means 1 10 is produced such that the steering wheel angle α is taken into consideration. Specifically, a handling parameter f_h is defined, which includes a first directional control component reflecting the steering wheel angle α.

According to one embodiment of the invention, the handling pa- rameter f_h represents a factor larger than zero, and smaller than or equal to one. Returning now to Figure 1 , the control unit 130 is here adapted to investigate whether or not the antilock control signal S_ABS is received. If so, the control unit 130 is further adapted to produce the reference signal s_rΘf by multiplying the anti- lock control signal s_ABs with the handling parameter f_h. If, however, the antilock control signal s_ABs is found not to be present, the control unit 130 is adapted to produce the reference signal s_rΘf, such that the reference signal s_rΘf is set equal to the operator-generated input signal s_man-

As a rule, the control unit 130 is adapted to produce the hand- ling parameter f_h, such that a relatively large steering wheel angle α results in a comparatively small handling-parameter value f_h. Conversely, a relatively small steering wheel angle α results in a comparatively large handling-parameter value f_h.

To improve the stability of the operation system, according to one embodiment of the invention, the control unit 130 is adapted to perform low-pass filtering of the steering wheel angle α. Here, the first directional component includes a low-pass filtered representation of the steering wheel angle α. For example, the handling-parameter f_h may be determined as:

f_h = e-^kα' [1 ] where k is a factor selected depending on the characteristics of the vehicle (possibly the factor k is a function of the vehicle speed v_v), and (X_f is the low-pass filtered representation of the steering wheel angle α.

For example, the factor k may depend on the maximum possible steering wheel angle α, which may vary substantially between a heavy truck and a sports car. In any case, the factor k is assig- ned such a value that a first directional component kα_f ² attains appropriate magnitudes for a typical range of steering wheel angles α for the vehicle 100.

According to another embodiment of the invention, the control unit 130 is adapted to produce the handling parameter f_h, such it also includes a second directional control component, which reflects a time derivative ά of the steering wheel angle α. Namely, the driver may need to perform rapid and relatively small steering-wheel movements to compensate for different coefficient of friction experienced by different wheels on the same axle when handling the vehicle on a μ-split surface. Hence, the steering wheel angle α may be relatively small, however the time-derivative ά thereof may be comparatively large.

Preferably, analogous to the discussion above, the control unit 130 is adapted to produce the handling parameter f_h such that a relatively large time-derivative value ά results in a comparatively small handling-parameter value f_h; and a relatively small time- derivative value ά results in a comparatively large handling-pa- rameter value f_h. For stability reasons, it is further advantageous if the control unit 130 is adapted to perform low-pass filtering of the time derivative ά of the steeri ng wheel angle α. In such a case, a second directional component, e.g. expressed c₂άf , of the handling-parameter f_h includes a low-pass filtered represen- tation ά_f of the time derivative ά of the steering wheel angle α. Consequently, the handling parameter f_h may be determined as:

f_h = e-^{(ciαf +C2άf2 )} [2] where Ci is a first factor (possibly a function of the vehicle speed v_v), (X_f is the low-pass filtered representation of the steering wheel angle α,

C₂ is a second factor (possibly also a function of the vehicle speed v_v), and ά_f is the low-pass filtered representation of the time de- rivative ά of the steering wheel angle α.

Naturally, there exist many alternative means to represent the above-mentioned expressions for the handling parameter f_h. For example, the handling parameter f_h may be determined as:

fh = 1 - M l

where d is a coefficient (possibly a function of the vehicle speed

Vv) ,

or

^J1 where di is a first coefficient (possibly a function of the vehicle speed v_v), and d₂ is a second coefficient (possibly also a function of the vehicle speed v_v),

respectively.

Analogous to the factor k, the values of the factors Ci and C₂, and the coefficients d, di and d₂ preferably depend on the vehicle characteristics (e.g. the maximum possible steering wheel angle α).

According to another embodiment of the invention, the control unit 130 is adapted to control the at least one brake means 1 10 based on the handling parameter f_h exclusively if at least one handling criterion is fulfilled. This means that upon non-fulfillment of the handling criteria, f_h is set to 1 by the control unit 130 when producing the reference signal s_rΘf = s_ABs-fh- According to this embodiment, a handling criterion is deemed fulfilled if the steering wheel angle α exceeds a threshold steering wheel angle α_th, and/or the time derivative ά of the steering wheel angle α exceeds a threshold steering wheel angle time derivative cc_th . Thereby, the braking control algorithm is simplified when it is estimated that the vehicle travels straight on a road having an unproblematic surface.

Figure 3 depicts a diagram, which illustrates how the proposed reference signal s_rΘf may be represented as a function of time t when controlling a brake means according to one embodiment of the invention. Here, we assume that a driver initially produces an operator-generated input signal s_man that describes a desired brake force to be applied to at least one wheel of the vehicle. Then, at a first point in time t-i , an ABS of the vehicle starts to override the input signal s_man by generating an antilock control signal S_ABS describing a brake force applicable to the at least one wheel 120 to avoid locking of the at least one wheel. Subsequently, at a second point in time t₂, the proposed handling parameter f_h further reduces the brake effect specified by the antilock control signal S_ABS in order to improve the vehicle handling.

In order to sum up, the general method of controlling brake means of a motor vehicle according to the invention will now be described with reference to the flow diagram in Figure 4.

A first step 410, receives an operator-generated input signal S_man describing a desired brake force to be applied to at least one wheel of the vehicle. A second step 420, investigates whether or not an automatically generated antilock control signal S_ABS is present. If no such signal S_ABS is present, a step 430 follows in which a reference signal s_rΘf is produced. The reference signal s_rΘf is adapted to control a brake force to be applied by at least one brake means to said at least one wheel, and in step 430, the reference signal s_rΘf is set equal to the input signal Sman- Thereafter, a step 480 follows.

If, however, step 420 finds that the automatically generated antilock control signal S_ABS is present, the procedure continues to a step 440. This step receives the antilock control signal S_ABS describing a brake force to be applied to the at least one wheel, where the brake force has been calculated, so that it is estimated that locking of the at least one wheel will be avoided.

A step 450, preferably executed in parallel with step 440, recei- ves a steering signal s_α indicative of a steering wheel angle α of the vehicle. A step 460, subsequent to step 450, then generates a handling parameter f_h, which includes a first directional control component reflecting the steering wheel angle α. As mentioned initially, the steering signal s_α is disregarded if it is found that a threshold steering wheel angle and/or a threshold steering wheel angle time derivative is exceeded after that the reception of the antilock control signal has been initiated. Namely, thereby, overcompensation of an ABS-assisted braking having been instigated when the vehicle is already in the course of passing a sharp corner can be avoided. It should also be pointed out that it is preferable that, if the steering wheel angle and/or its time derivative has a non-zero value when initiating a brake procedure, this/these initial value/s is/are set as a respective reference relative to which it is determined whether or not said handling criterion is fulfilled. A subsequent step 470 produces a reference signal s_rΘf (i.e. as an alternative to the signal produced in step 430) based on the input signal s_man, the antilock control signal S_ABS and the handling parameter f_h. Preferably, the reference signal s_rΘf is here produced, such that a magnitude of the reference signal s_rΘf is delimited by whichever signal of the input signal s_man and the product of the handling parameter f_h and the antilock control signal S_ABS that represents a smallest brake force to be applied to the at least one wheel. Consequently, s_rΘf = min(s_man, s_ABs-f_n)- Since the antilock control signal S_ABS must be present for entering step 470 via step 420, it is essentially always the case that: s_ABs fh < Sman- However, if a cycle repeat time through procedure (i.e. from step 410 to 480) is relatively long, and the driver releases the brake pedal shortly after that the ABS has started to operate, it is possible that s_man < s_ABs-f_n in step 470.

Nevertheless, a step 480 following step 470 and the above-mentioned step 430, generates a brake control signal to the at least brake means based on the reference signal s_rΘf, which has been generated either in step 430 or in step 470. Thereafter, the pro- cedure loops back to step 410 again.

All of the process steps, as well as any sub-sequence of steps, described with reference to Figure 4 above may be controlled by means of a programmed computer apparatus. Moreover, although the embodiments of the invention described above with reference to the drawings comprise computer apparatus and processes performed in computer apparatus, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code; object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Program- mable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal which may be conveyed directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.

Claims

1 . A brake control system for a motor vehicle (100) comprising a control unit (130) adapted to: receive an operator-generated input signal (s_man) descri- bing a desired brake force to be applied to at least one wheel (120) of the vehicle (100), receive an automatically generated antilock control signal (S_ABS) describing a brake force to be applied to the at least one wheel (120) in order to avoid locking of the at least one wheel (120), and produce a reference signal (s_rΘf) based on the received signals (Sman, S_ABS) such that a magnitude of the reference signal (Srβf) is delimited by whichever of the input signal (s_man) the anti- lock control signal (S_ABS) that represents a smallest brake force to be applied, the reference signal (s_rΘf) being adapted to control the at least one brake means (1 10) such that a given brake force is applied to at least one wheel (120) of the vehicle (100), the system comprising a sensor means (140) adapted to register a steering signal (s_α) indicative of a steering wheel angle (α) of the vehicle (100), and the control unit (130) is adapted to receive the steering signal (s_α) and control the at least one brake means (1 10) on the further basis of a handling parameter (f_h) comprising a first directional control component reflecting the steering wheel angle (α), characterized in that the control unit (130) is adapted to control the at least one brake means (1 10) on the further basis of the handling parameter (f_h) exclusively if a handling criterion is fulfilled, the handling criterion being fulfilled if at least one of a threshold steering wheel angle (α_th) and a threshold steering wheel angle time derivative (όc_th ) is exceeded, and the threshold steering wheel angle (α_th) and/or the threshold steering wheel angle time derivative ( όc_th ) are/is exceeded after that the control unit (130) has initiated reception of the antilock control signal (S_ABS)-

2. The system according to claim 1 , characterized in that the handling parameter (f_h) represents a factor larger than zero, and smaller than or equal to one; and the control unit (130) is adapted to investigate whether or not the antilock control signal (S_ABS) is received, and if so, produce the reference signal (s_rΘf) to the at least one brake means (1 10) by multiplying the antilock control signal (S_ABS) with the handling parameter (f_h).

3. The system according to claim 2, characterized in that the control unit (130) is adapted to produce the handling parameter (f_h) such that: a relatively large steering wheel angle (α) results in a comparatively small handling-parameter value (f_h), and a relatively small steering wheel angle (α) results in a comparatively large handling-parameter value (f_h).

4. The system according to claim 3, characterized in that the control unit (130) is adapted to perform low-pass filtering of the steering wheel angle (α), and the first directional component comprises a low-pass filtered representation of the steering wheel angle (α).

5. The system according to any one of the claims 2 to 4, characterized in that the handling parameter (f_h) further comprises a second directional control component reflecting a time derivative ( ά ) of the steering wheel angle (α).

6. The system according to claim 5, characterized in that the control unit (130) is adapted to produce the handling parameter

(f_h) such that: a relatively large time-derivative value ( ά ) results in a comparatively small handling-parameter value (f_h), and a relatively small time-derivative value ( ά ) results in a comparatively large handling-parameter value (f_h).

7. The system according to claim 6, characterized in that the control unit (130) is adapted to perform low-pass filtering of the time derivative (ά ) of the steering wheel angle (α), and the second directional component comprises a low-pass filtered representation of the time derivative ( ά ) of the steeri ng wheel angle (α).

8. The system according to any one of the preceding claims, characterized in that the reference signal (s_rΘf) expresses one of: a brake pressure to be applied by the at least one brake means (1 10), a target slip value in respect of the at least one wheel (120), and a target retardation of the vehicle (100).

9. A motor vehicle (100) comprising at least one brake control system according to any one of the preceding claims.

10. A method of controlling at least one brake means (1 10) of a motor vehicle (100), wherein the at least one brake means (1 10) is adapted to apply a brake force to at least one wheel (120) of the vehicle (100) in response to a reference signal (s_rΘf), the method comprising: receiving an operator-generated input signal (s_man) describing a desired brake force to be applied to the at least one wheel (120), receiving an automatically generated antilock control signal (S_{AB S}) describing a brake force to be applied to the at least one wheel (120) in order to avoid locking of the at least one wheel (120), produci ng the reference signal (s_rΘf) based on the received signals (s_man, S_{AB S}) such that a magnitude of the reference signal (S_re_f) is delimited by whichever of the input signal (s_man) the antilock control signal (S_{AB S}) that represents a smallest brake force to be applied to the at least one wheel (120), registering a steering signal (s_α) indicative of a steering wheel angle (α) of the vehicle (100), and produci ng the reference signal (s_rΘf) on the further basis of a handling parameter (f_h) comprising a first directional control component reflecting the steering wheel angle (α), characterized by controlling the at least one brake means (1 10) on the further basis of the handling parameter (f_h) exclusively if a handling criterion is fulfilled, the handling criterion being fulfilled if at least one of a threshold steering wheel angle (α_th) and a threshold steering wheel angle time derivative (όc_th ) is exceeded, and the threshold steering wheel angle (α_th) and/or the threshold steering wheel angle time derivative ( όc_th ) are/is exceeded after that the control unit (130) has initiated reception of the antilock control signal (S_ABS)-

1 1 The method according to claim 10, characterized by the handling parameter (f_h) representing a factor larger than zero, and smaller than or equal to one; and the method comprises: investigating whether or not the antilock control signal (SABS) is received, and if so, producing the reference signal (s_rΘf) to the at least one brake means (1 10) by multiplying the antilock control signal (S_ABS) with the handling parameter (f_h).

12. The method according to claim 1 1 , characterized by pro- ducing the handling parameter (f_h) such that: a relatively large steering wheel angle (α) results in a comparatively small handling-parameter value (f_h), and a relatively small steering wheel angle (α) results in a comparatively large handling-parameter value (f_h).

13. The method according to claim 12, characterized by low- pass filtering the steering wheel angle (α), and the first directional component comprising a low-pass filtered representation of the steering wheel angle (α).

14. The method according to any one of the claims 1 1 to 13, characterized by the handling parameter (f_h) further comprising a second directional control component reflecting a time derivative ( ά ) of the steering wheel angle (α).

15. The method according to claim 14, characterized by pro- ducing the handling parameter (f_h) such that: a relatively large time-derivative value ( ά ) results in a comparatively small handling-parameter value (f_h), and a relatively small time-derivative value ( ά ) results in a comparatively large handling-parameter value (f_h).

16. The method according to any one of the claims 14 or 15, characterized by low-pass filtering the time derivative (ά ) of the steering wheel angle (α), and the second directional component comprising a low-pass filtered representation of the time derivative ( ά ) of the steering wheel angle (α).

17. The method according to any one of the claims 10 to 16, characterized by the reference signal (s_rΘf) expressing one of: a brake pressure to be applied by the at least one brake means (1 10), a target slip value in respect of the at least one wheel

(120), and a target retardation of the vehicle (100).

18. A computer program directly loadable into the internal memory of a computer, comprising software for controlling the steps of any of the claims 10 to 17 when said program is run on the computer.

19. A computer program product (135), having a program recorded thereon, where the program is to make a computer control the steps of any of the claims 10 to 17.