DE19735687A1 - Brake control for road vehicles - Google Patents

Abstract

A proximity detector (8) is fitted on the brake pedal, to monitor the spacing of the brake foot from the pedal. A control circuit measures the speed of approach of the brake foot, as well as the acceleration of the foot to initiate the braking action before the brake foot has touched the brake pedal. The brake application is only applied if the brake foot is within a preset spacing from the brake pedal and if the dynamic state of the brake foot satisfies preset conditions. The proximity sensor covers a preset field of view.

Description

The invention relates to an apparatus and a method Driving a motor vehicle brake system, in particular the other via a distance sensor assigned to a brake pedal Behavior patterns of driver initiation processes can determine in order to thereby before the start of the Brake pressure build-up a measure of the expected braking request of the driver.

Conventionally designed brake systems for motor vehicles use the actuation of a as a measure of the braking process Brake pedals by the driver. As a result, the required braking time from various factors. After the occurrence of the event, a so-called called perception time. Then there is one certain time for the mental processing of perception, then the driver's foot movement occurs. The aforementioned  Times are caused, for example, by driver fatigue and thus through appropriate driver inattentiveness influenced more or less, so that it often becomes a unnecessary delay between the actual event, on the basis of which braking should take place, and that did neutral braking of the vehicle comes.

One approach to solving this problem is in WO 95/01898 described. According to this document, the position of the right foot of the driver detected, with a fast Change the position of the right foot from the accelerator pedal to Direction on the brake pedal on the need for one forced execution of a braking process closed becomes.

However, this prior art has the disadvantage that it does when the accelerator pedal is released quickly connected to a rapid change of foot towards the brake pedal is a danger assumed traffic situation and consequently a Full braking can be initiated. In addition, however also occur in the case of rapid foot reactions full braking without a specific emergency braking request is initiated, which in turn leads to an uncomfortable Vehicle reaction (jerk) leads. Such a system has still has the disadvantage that it does not respond to driving situations speaks in which the driver's foot does not come from the accelerator pedal. In particular, this is a problem when increased Motor vehicles with a cruise control and / or an intelli cruise control system (for example with an Ab level measurement to the vehicle in front) are.

The object of the invention is a device and Method for controlling a motor vehicle brake system create that from the movement behavior of the driver's brake foot immediately before applying the brake on the he  required control of the motor vehicle brake system can close a safe and reliable way.

According to the invention is a device for controlling a Motor vehicle brake system provided a distance Sensor can have a distance s of a brake pedal assigned driver's foot detected by the brake pedal. Wei Furthermore, a foot speed ds / dt of the driver's foot can be in Direction on the brake pedal can be determined, which a white More information about driver behavior before braking allowed. The device according to the invention can furthermore have a control unit that brakes the motor vehicle location according to the detected distance s and Can control foot speed ds / dt.

By evaluating the distance s from the brake pedal and the Foot speed ds / dt can start before braking conclude how critical the driving situation is. This allows the driver to initiate braking be evaluated, resulting in a considerable security ge winn leads.

The dependent claims show advantageous execution tion forms and further developments of the invention.

The distance sensor can be essentially spherical Have detection area. Furthermore, the distance can be a short-range distance sensor. The distance sensor can also have a flattened detection area.

Through the spherical detection area of the distance sensor can also approach the driver's foot from the sides can be grasped and evaluated, which leads to a further certainty lead in safety.  

In addition, it should be noted that the distance sensor can be designed such that it can also output the foot speed ds / dt in addition to the distance of the driver's foot from the brake pedal. The same applies to a foot speed change signal described later. Of course, a control unit or a circuit provided for this purpose can also determine the foot speed ds / dt and the foot speed change d ² s / dt ² from the distance signals of the distance sensor.

The control _{method according to the} invention cannot, for example, cause the motor vehicle _{brake system to react} if the foot speed ds / dt is below a predetermined foot _{speed limit value} ds / dt _limit . However, there can also be no reaction of the motor vehicle brake system if a change in foot speed d ² s / dt ² within a predetermined distance s _{limit of} the driver's foot brake pedal is negative and is below a predetermined negative limit value d ² s / dt ² _limit .

This can be used to evaluate a situation, for example in which the driver's brake foot is quickly heading in the direction on the brake pedal and then just before touching the Brake pedals slowed down or pulled back.

Due to the above-described embodiments, as already mentioned above, an unwanted braking of the Prevent vehicle effectively without a specific braking request be changed.

Furthermore, it should be noted that the predetermined distance s _{limit can be,} for example, about 5 to 10 cm.

External triggering or full braking of the motor vehicle brake system can then be initiated if the foot speed ds / dt is within a predetermined distance s _{limit of} the driver's foot from the brake pedal above a predetermined foot _{speed limit value} ds / dt _limit and a foot _{speed change} d ² s / dt ^{2 is} within of the predetermined distance s _is zero or positive.

The above-mentioned external triggering can be a full braking solution that reaches up to the control range of an ABS controller that may be present. However, the external triggering can also build up a lower brake pressure. To determine the target brake pressure output to the motor vehicle brake system, the detected distance s, the foot speed ds / dt and / or the foot speed change d ² s / dt ² can be used, in which case the brake pressure can be a function of the aforementioned values . As a result, the driver's behavioral pattern can be used to achieve an optimal, externally triggered braking, which optimally corresponds to the driver's will, before the actual braking process is triggered.

Furthermore, a pre-filling of the motor vehicle brake system can be initiated if the foot _speed ds / dt _exceeds the predetermined foot _{speed limit value} ds / dt _limit and the distance s is greater than the predetermined distance s _limit. As a result, the vehicle brake system can be optimally _adapted to the impending braking is being prepared. By filling the motor vehicle brake system, for example, the brake shoes can already be brought to the brake discs without the driver feeling any delay. A braking process that is then triggered consequently has an optimized response time, since the brake shoes no longer have to overcome dead time before they touch the brake disc.

Depending on the distance s, the foot speed ds / dt and / or the foot speed change d ² s / dt ² , the pre-filling pressure of the motor vehicle brake system can be set to who. If, for example, the foot speed ds / dt shortly before a certain distance s, which is already relatively close to the predetermined distance s _limit, is relatively high and the foot speed change d ² s / dt ^{2 is} above a certain limit value, then a high one can be used Probability can be expected that the driver will initiate braking. As a result, the pre-charge pressure of the vehicle brake system can be set as a function of the aforementioned values. The level of the pre-filling pressure can be set larger, for example, with increasing foot speed ds / dt and / or increasing positive foot speed change d ² s / dt ² . A pre-filling pressure can be selected which is higher than that at which the driver does not feel any braking. Even in these cases, the vehicle may decelerate slightly, which can further shorten the braking distance achieved later.

For example, with an increasing positive foot speed change d ² s / dt ^2, a pre-filling can take place at a larger distance s.

The pre-filling can, for example, with a pre-filling pressure take place, which is between 2 and 10 bar.

The following are exemplary embodiments of the invention explained in more detail using schematic drawings. It demonstrate:

Fig. 1 is a schematic representation of a motor vehicle;

Fig. 2 is a schematic representation of a distance sensor;

Fig. 3 is a schematic illustration of a brake pedal with an assigned driver's foot, together with a diagram illustrating the movement of the driver's foot relative to the brake pedal; and

Fig. 4 is a flow chart according to an embodiment of the invention.

Fig. 1 shows a motor vehicle 1 with wheels 5, wherein each wheel 5 is assigned a brake cylinder 3. The Bremszy cylinder 3 are connected via hydraulic lines 4 to a motor vehicle brake system 2 . The hydraulic lines 4 shown can be omitted if a brake-by-wire system is used. The motor vehicle brake system 2 can be controlled by a control unit 6 . This is done via a control line 9 . The control unit 6 is connected to a brake pedal 7 and a distance sensor 8 . The distance sensor 8 can be arranged on the brake pedal 7 (cf. FIG. 3).

The distance sensor 8 is shown in an enlarged view in FIG. 2. A detection area 10 is shown above and next to the distance sensor 8 . This, for example, spherical detection area 10 enables the distance sensor 8 to also detect the approach of a driver's foot 11 from the side.

Fig. 3 shows the brake pedal 7 to a distance thereto angeord Neten sensor 8. The driver's foot 11 is also shown.

Furthermore, FIG. 3 shows a diagram with the distance as the abscissa and the foot speed | ds / dt | as ordinate. The origin of this coordinate system is located on the brake pedal 7 . In this diagram, two lines are initially shown, which are labeled "trigger" and "non-trigger". These two pairs of values for the distance s and the foot speed ds / dt are intended to represent examples of a movement of the driver's foot 11 . If the driver's foot 11 moves approximately along the solid line (release), then it first moves at a large distance from the brake pedal 7 at a relatively low foot speed ds / dt. Then the foot speed ds / dt increases sharply, the foot speed change d ² s / dt ² and thus the increase in foot speed ds / dt being high. The slope of the foot speed ds / dt (ie d ² s / dt ² ) then decreases again somewhat, but remains at a high level. In this case, a triggering of the vehicle brake system 2 is caused since the driver's foot 11 does not perform a braking movement just before the brake pedal 7 , so that it can be concluded with a very high degree of certainty that the driver's will consists in braking.

The dashed line (non-triggering) shows a similar increase in the initial area as the aforementioned curve. After a relatively steep increase, however, this curve drops again, ie the change in foot speed d ² s / dt ² initially becomes zero and then negative. If this is the case, the driver's foot 11 initially moves very quickly in the direction of the brake pedal 7 , and is then _braked again by the driver within the predetermined distance s _limit . By detecting the distance of the driver's foot 11 from the brake pedal 7 and a determination of the driver's foot speed ds / dt and the driver's foot speed change (slope) d ² s / dt ² can thus be detected that the driver does not want braking, although initially a large value for the foot speed ds / dt and the change in speed (slope) d ² s / dt ^{2 were} determined. As a result, the actual driver's will can be detected very reliably.

At this point it should be noted that a triggering of the motor vehicle brake system 2 or a non-triggering and the already introduced predetermined distance s _limit do not of course have to represent fixed values, but that value ranges can be used instead of these values. For example, the solid tripping curve could be converted into a tripping area by drawing a straight line parallel to the abscissa below the tripping line shown, starting from the zero point of the abscissa to the right. This line would correspond to a zero slope of foot speed ds / dt. The area between this curve and the trigger curve shown would thus be a scatter band in which a triggering of the vehicle brake system 2 would be caused. The above applies in the same way to the dashed line (non-triggering), it being possible for an additional line to be drawn in there which is located above the dashed line shown.

Further, in FIG. 3 a dash-dotted line represents Darge showing a movement of the driver's foot 11 with a lower gradient. With a larger positive Fußgeschwindigkeitsänderung (slope of the foot speed ds / dt) d ² s / dt ² takes place already at a distance s _B, a pre-charge of the motor vehicle brake system. 2 However, if there is a smaller positive change in foot speed d ² s / dt ² (dash-dotted line), the motor vehicle brake system 2 is only primed at a smaller distance s _{A of} the driver's foot 11 from the brake pedal 7 .

The pre-filling can thus be adjusted in accordance with the movement of the driver's foot 11 in a foot speed / distance space.

FIG. 4 shows, in step 100, the detection of the distance s of the driver's foot from the brake pedal 11. 7 The foot speed ds / dt and the foot speed change d ² s / dt ^{2 are} then determined in a step 101, the foot speed ds / dt being the first time derivative of the detected distance s and the foot speed change d ² s / dt ^{2 being} the second derivative . The change in foot speed d ² s / dt ² thus represents the increase in foot speed ds / dt.

In a step 102 , it is determined whether the foot speed ds / dt is greater than the predetermined foot speed limit ds / dt _limit . If this is not the case, a branch is made to step 103 in that there is no reaction from the motor vehicle brake system 2 .

However, if it is determined in step 102 that the Fußge speed ds / dt is greater than the predetermined Fußge speed limit ds / dt _limit , it is determined in a step 104 whether the distance s is smaller than the predetermined distance s _limit . If this is not the case, the motor vehicle brake system 2 is pre-filled in a step 105 . This pre-filling process can depend on the distance s, the foot speed ds / dt and / or the change in foot speed d ² s / dt ² .

If it is judged in step 104 that the distance s is smaller than the predetermined distance s _limit , a branch is made to a step 106 in which it is checked whether the change in foot speed d ² s / dt ^{2 is} greater than or equal to zero. If this is the case, the motor vehicle brake system 2 is fully triggered in a step 109 . As already mentioned above, the so-called full triggering can of course also depend on the distance s, the foot speed ds / dt and / or the foot speed change d ² s / dt ² .

If it is judged in step 106 that the change in foot speed d ² s / dt ^{2 is} less than zero (ie the slope of ds / dt is negative), a branch is made to step 107 , in which a check is made to determine whether the change in foot speed d ² s / dt ^{2 is} smaller than a predetermined negative limit value d ² s / dt ² _limit . If the negative change in foot speed d ² s / dt ^{2 is} smaller than the limit value d ² s / dt ² _limit , the motor vehicle brake system 2 does not react in a step 110 . However, if the change in foot speed d ² s / dt ^{2 is} above the negative limit value d ² s / d ² _limit , a branch is made to a step 108 in which the brake system is primed. The statements made regarding step 105 also apply in the same way to step 108 .

In addition, it should be pointed out that ds / dt _limit and d ² s / dt ² _limit can depend on the distance s. In the near range, ds / dt _{limit can be} smaller than in the far range. The same can apply to d ² s / dt ² _limit .

In conclusion, it should be pointed out that to simplify the diagram in FIG. 3, the origin of the coordinates has been moved to the Bremspe dal 7 . As a result, an increase in the foot speed ds / dt in the direction of the brake pedal 7 (with a decreasing distance s) would be negative, since ds is negative. In the above description, however, a positive change in the foot pedal speed ds / dt means an increase in ds / dt as the distance s decreases.

Claims (11)

1. Device for driving a motor vehicle brake system, with

• - A device for detecting a position of a driver's foot ( 11 ) assigned to a brake pedal ( 7 ) and
• - a control unit ( 6 ) which receives position signals from the device and controls the motor vehicle brake system ( 2 ) accordingly,

characterized in that the device is a distance sensor ( 8 ) which detects a distance s of the driver's foot from the brake pedal ( 7 ) and via its output signals a foot speed ds / dt of the driver's foot ( 11 ) in the direction of the brake pedal ( 7 ) is determined and the control unit ( 6 ) controls the motor vehicle brake system ( 2 ) in accordance with the detected distance s and the foot speed ds / dt. 2. Device according to claim 1, characterized in that the distance sensor ( 8 ) has a substantially kugelför shaped detection area ( 10 ) and a Nahbe rich distance sensor. 3. Apparatus according to claim 1 or 2, characterized in that the control unit ( 6 ) causes no reaction of the vehicle brake system ( 2 ) when the Fußgeschwin speed ds / dt is below a predetermined Fußgeschwindig speed limit ds / dt _limit . 4. Apparatus according to claim 1 or 2, characterized in that the control unit ( 6 ) causes no reaction of the vehicle brake system ( 2 ) when a speed change of foot d ² s / dt ² within a _{predetermined} distance s _{limit of} the driver's foot ( 11th ) from the brake pedal ( 7 ) is negative and is below a predetermined negative limit value d ² s / dt ² _limit . 5. The device according to claim 4, characterized in that the predetermined distance s _{limit is} 5 to 10 cm. 6. The device according to claim 1 or 2, characterized in that the control unit ( 6 ) triggers an external triggering of the motor vehicle brake system ( 2 ) when the Fußge speed ds / dt within a predetermined _distance s _{limit 1 of} the driver's foot ( 11 ) from the brake pedal ( 7 ) lies above a predetermined foot _{speed limit value} ds / dt _limit and a foot _{speed change} d ² s / dt ^{2 is} zero or positive within the predetermined distance s _limit . 7. The device according to claim 1 or 2, characterized net gekennzeich that the control unit (6) causes a prefilling of the motor vehicle brake system (2) when the Fußge velocity ds / dt exceeds the predetermined Fußgeschwindig keitsgrenzwert ds / dt _cross exceeds and the distance s is greater than the predetermined distance s _limit 8. Device according to one of claims 1, 2 and 7, characterized characterized that the prefill with a prefill pressure is between 2 and 10 bar. 9. Device according to one of claims 1, 2, 7 and 8, characterized in that the pre-pressure from the stand from s, the foot speed ds / dt and / or the foot speed change d ² s / dt ² depends. 10. Device according to one of claims 1, 2, 7 to 9, characterized in that the control unit ( 6 ) with egg ner increasing positive foot speed change d ² s / dt ² a pre-filling takes place even at a large distance s. 11. Method for controlling a motor vehicle brake system, with the steps:

• - Detecting a position of a driver's foot ( 11 ) and a brake pedal ( 7 )
• - Controlling the motor vehicle brake system ( 2 ) accordingly, the position signals,

characterized in that distance s of the driver's foot ( 11 ) from the brake pedal ( 7 ) is detected and a foot speed ds / dt of the driver's foot ( 11 ) in the direction of the brake pedal ( 7 ) is determined and the motor vehicle brake system ( 2 ) corresponds to the detected distance s and the foot speed ds / dt is controlled.