JP2001122094A - Control method and device for brake device - Google Patents

Abstract

[PROBLEMS] To provide a method and an apparatus capable of reducing a risk that a following vehicle collides with a vehicle equipped with such control of a brake device. A method and a device for controlling a braking device are proposed, in which the braking force is increased independently of the driver in at least one driving situation. If a danger of collision from behind is detected, the increased braking force is reduced or limited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a brake device.

[0002]

2. Description of the Related Art In modern brake systems, the electrical control increases the braking force applied to the wheels in at least one driving situation independently of the driver. An example for electric control, in which the applied braking force is increased independently of the driver, is disclosed in DE 197 197 A1.
38390. The control unit for the proposed braking device detects when the driver wants to apply a brake having approximately the maximum braking force, based on the driver's braking desire. When such a driver's braking request is detected, at least at the selected wheel brake, the braking force is increased by the driver's setting until the braking force reaches the maximum braking force. In a known manner, the vehicle is further equipped with one device,
With this device, it is possible to evaluate, for example, the danger potential of a vehicle equipped with this device against a rear-end collision. By measuring the distance to the obstacle in front of the vehicle and / or the relative speed thereto, the control of the braking device is made responsive or non-responsive, in which case the danger potential is high. For example, in order to avoid a collision, the braking force is increased independently of the driver as early as possible, while when the danger potential is low, the driver is independent of the driver only when the driver's braking desire is relatively large. The braking force is increased. Thus, the known device improves the braking characteristics of the vehicle. The reason for this is that in order to achieve near maximum braking force, the driver no longer has to depress the brake with full force, but only to indicate the corresponding braking desire by operating the brake pedal. By detecting the danger potential ahead of the vehicle, control is further improved. The reason is that when a dangerous potential exists, the necessity for causing such a braking force increase is detected earlier than when there is no dangerous potential. However, this alone does not solve the problem of the following vehicle. If such an automatic braking force increase occurs in a vehicle equipped with a corresponding device and the vehicle behind the vehicle does not have such a function, there is a risk that a following vehicle will collide with the vehicle. Such dangers are ubiquitous if a large braking force independent of the driver, which cannot be achieved by a normal driver under all conditions, can be set by means of electric brake control.

In order to detect a vehicle and / or to measure a distance to the vehicle and / or to calculate a relative speed with respect to the vehicle, radar signals, Devices are known that detect a vehicle based on laser, ultrasonic and infrared signals, output a signal indicative of the distance to the vehicle, and determine a relative speed between the two vehicles based on the signal. As an alternative to this method, it is also known in the prior art to detect a vehicle with at least one video camera and / or measure the distance to this vehicle (see, for example, US Pat. No. 5,410,346).

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an arrangement which make it possible to reduce the risk of a following vehicle crashing into a vehicle equipped with such a control of the braking device.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for controlling a braking device, in which a braking force is increased independently of a driver on at least one wheel in at least one driving situation. In this case, the braking force is increased independently of the driver, or the increase is limited, thereby achieving the brake device control method of the present invention.

[0006] The above object is also achieved by a control device for a braking device, comprising a control unit for increasing a braking force on at least one wheel independently of a driver in at least one driving situation, wherein a danger of collision from behind is detected. And a detection device that acts on the control unit so as to reduce or limit the increased braking force when danger is detected. Achieved.

[0007] The method described below advantageously avoids the risk of a rear-end collision due to a trailing vehicle when the automatic braking force is increased, preferably with substantially maximum braking force. This is achieved by determining the danger potential behind the vehicle, in which case, if the danger potential is high, in order to prevent a subsequent vehicle from crashing into this vehicle or to avoid such a collision risk,
The increased braking force is reduced.

In determining whether a braking force reduction takes place after an automatic braking force increase, in addition to the risk potential behind the vehicle, the risk potential in front of the vehicle evaluated according to the state of the art described at the outset is used simultaneously. Is particularly advantageous. When the danger potential at the rear of the vehicle is substantially greater than the danger potential at the front of the vehicle, the braking force reduction is emphasized. On the other hand, when the relationship is reversed, the braking force reduction is not performed after the automatic braking force increase, Alternatively, only a slight reduction in braking force takes place.

It is particularly advantageous to use a camera in the rear area of the vehicle, with which it is possible to detect the danger potential behind the vehicle. It is particularly advantageous when the video camera is used as is in other applications, for example as a rearview mirror, parking assist or access verification. In this case, the camera present is used for vehicle detection and / or distance measurement.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 shows a time diagram in which the time course of the brake pedal position Bp (dashed line) and the applied braking force Bk (solid line) is graduated. The basis of this diagram is the electrical control of the braking device, in which in the event of the presence of a particular driver characteristic, e.g. derived from the driver's desired time change, the braking device is provided with a control to reduce the braking distance. The braking force is increased beyond the set value. This so-called brake assist function is, in a preferred embodiment, a brake pedal actuation signal (stroke, force, supply pressure, etc.).
Is started when the time change of the data exceeds a predetermined threshold value. At time TB, it is assumed that the driver has activated the brake application by operating the brake pedal. Up to time TE, the brake pedal position increases, after which the brake pedal position remains constant for the rest of the braking process. According to the prior art described at the outset, the gradient of the brake pedal actuation signal after time TB is determined. At time point TE, it has been detected that the gradient has exceeded a predetermined threshold value, so that after time point TE an automatic braking force increase, generally a full braking process, is introduced. Therefore, until then,
The braking force that has changed in response to the pedal operation is increased from time TE until reaching the maximum value as shown in FIG. This maximum value is maintained unless the driver stops increasing the braking force by resetting the brake pedal. In this case, the threshold value for the gradient is variable and, for example, as in the prior art described at the outset, is a function of whether a danger (eg, an obstacle just before a collision) has been detected in front of the vehicle.

[0011] This known method does not take into account the danger of the vehicle following the vehicle. By increasing the braking force to a maximum value after time point TE, the braking effect of the vehicle on existing road conditions is optimized and the braking distance is reduced. A vehicle not equipped with a corresponding device, in which the braking action is only provided by the driver, for example, may not be able to follow this shortened braking distance and may collide.
Therefore, devices in the rear area of the vehicle, such as video cameras, range radars, distance measuring devices operating on the basis of ultrasound, laser or infrared signals, determine whether there is another vehicle behind the vehicle. It is designed to be. Here, the danger potential at the rear of the vehicle is determined, and if no danger at the front of the vehicle is detected, the braking force in the active automatic braking force increase is reduced. As a result, an extension of the brake value is obtained, and a rear-end collision in which the extension of the brake value is possible can be avoided. Preferably a function of speed,
When the following vehicle enters the safety range of the preceding vehicle, the determined distance and / or the calculated relative speed
When it is substantially determined that the following vehicle cannot be stopped without a collision, the danger behind the vehicle is estimated in the same manner as the danger ahead of the vehicle.

This solution is illustrated in FIG. 3 by a time diagram similar to FIG. Again, suppose that the driver operated the brake pedal at time TB.
Here, two different driver types are shown, a first driver (I) operating harder on the brake pedal and another driver (II) operating weaker on the brake pedal. The threshold value for initiating the automatic braking force increase is changed as a function of the determined danger potential by the device for determining the danger potential ahead of the vehicle described in the prior art at the beginning. In addition, not only in the case of a driver performing a strong brake operation, but also in the case of a driver performing a weak brake operation, an increase in the automatic braking force is led. Subsequently, the braking force is increased to a maximum value independent of the driver setting. At time TV, the measuring device mounted in the rear area determines that a dangerous potential exists behind the vehicle, while a sufficient braking distance is available in front of the vehicle. In this case, at the time point TV, the braking force is reduced from the maximum value to a predetermined value still independently of the driver's operation of the brake pedal.

The identification of the danger potential is determined, for example, by the method described in the prior art mentioned at the outset. A measuring device, for example a video camera, mounted in the rear area of the vehicle determines the presence of another vehicle. Further, the distance to the obstacle is determined by the measuring device, and the relative speed with respect to the vehicle is calculated based on the change of the vehicle speed and the distance. In the simple case, the danger potential is detected when the following vehicle is within a distance to the vehicle, which is preferably a function of the speed. A rather accurate identification of the danger potential is based on the fact that the relative speed is determined, and
It is determined whether the distance available to the vehicle behind is sufficient for the vehicle to stop without collision. If this is the case, no danger potential is inferred, whereas if the opposite is true, there is a danger potential. The danger potentials determined before and after are compared with each other. In this case, this result may be used for evaluation. For example, when the rear danger is detected but the front danger is not detected, the increased braking force is reset. In general, if a danger potential is detected in front, this information basically has a higher value than information that danger is imminent from the rear. This is based on the fact that the front detector is more reliable than the rear detector. In this case, the information ahead is always regarded as important. Safety devices (such as airbags) present in the vehicle have also been considered in the evaluation. Whenever the driver sets a relatively high braking force via pedal operation, the braking force is increased.

If the danger behind the vehicle is evaluated higher than the danger ahead of the vehicle, the increased braking force is reduced.
In this case, it is preferable that the braking force is not reduced below the braking force set by the driver. The braking force reduction may be performed as a function of how much the rear hazard and the front hazard are, where the greater the rear hazard and the less the hazard ahead. The lower the braking force, the greater.

When the danger potential at the rear of the vehicle decreases in the course of the course and / or when the driver further depresses the brake pedal, the braking force reduction is stopped and a new increase to the maximum braking force takes place.

FIG. 2 shows a control device for controlling the braking device, which implements the method described above. Control unit 10
The control unit 10 has at least one microcomputer. The control unit 10 receives the brake and
A pedal operation signal value is supplied. In addition, line 16
The wheel rotation speed information is transmitted from the measuring device 18 via the. Furthermore, in a preferred embodiment, the accelerator pedal actuation value is transmitted from the measuring device 22 via the input line 20. Furthermore, an input line 24 is provided, via which the control unit 10 is connected to a control unit 26 of the adaptive cruise control. One or more signal values are transmitted via this input line 24, from which the dangerous potential ahead of the vehicle is derived. Similarly, one or more signals are transmitted to the control unit 10 via a line 28 from a video camera 30 mounted on the rear of the vehicle or its evaluation unit,
The hazard potential behind the vehicle is determined from these signals. Via the output line 32, the control unit 10 operates the electrically actuated adjusting element 34 of the braking device, which increases the braking force at at least one wheel brake or reduces the braking force at this wheel brake. . In this case, in a preferred embodiment, a valve of a hydraulic or electro-hydraulic brake device is intended, or an actuator of a wheel brake with an electric clamping device.

In a preferred embodiment, information on the distance to obstacles in front of and behind the vehicle and / or the relative speed of the obstacles is transmitted via input lines 24 and 28. From these values, for example, by comparing distance information with defined safety limits and / or by assessing the risk of collision with obstacles from distance, relative speed and own deceleration, And the danger potential behind. Furthermore, since the expected course of the obstacle is additionally taken into account, the danger potential is only detected when the obstacle is on the collision course.

In the microcomputer of the control unit 10, a program for executing the above-mentioned method and determining an output signal is provided, and the output signal performs a corresponding control of the brake device. An example of such a program is shown in the flowchart of FIG. 4 as a preferred embodiment.

The illustrated program is started at a predetermined time. In a first step 100, it is checked whether the driver has started an automatic braking force increase due to driver characteristics. This is done in a manner known from the prior art,
This is done by deriving a corresponding characteristic based on comparing the slope of the brake pedal actuation signal with a threshold value. In this case, the threshold value is variable and is, in particular, a function of the hazard potential ahead of the vehicle determined according to the state of the art described at the outset. If such a characteristic does not exist, step 102 adjusts the braking force in accordance with the actual driver setting, the program is terminated and restarted at the next time.

If it is determined in step 100 that there is a brake request for the automatic braking force increase, step 106
As a result, the automatic braking force rise is started, and for example, the maximum braking force is set in this braking request. Subsequently, at step 104, the driver
It is checked whether it is desired to reset the pedal and stop the automatic braking force increase. If this is the case, the automatic braking force increase is stopped and the braking force is set according to step 102. If there is not enough reset of the brake pedal, at step 108
The danger potential behind the vehicle checks whether a condition exists for a reduction in the increased braking force. For this, as described above, for example, because other vehicles behind the vehicle are within a distance range that is a function of speed,
It is determined whether another vehicle behind the vehicle is within the danger area for the own vehicle. Furthermore, it is checked whether a danger exists ahead of the vehicle, for example, if the own vehicle is within the corresponding distance range to the vehicle traveling ahead. If the danger from the rear is greater than the danger from the front, step 110 reduces the increased braking force. If the danger ahead is rated higher than the danger behind, the braking force is not changed (automatic braking force increase) and continues from step 104 at the next program run.

If the braking force is reduced, step 1
At 12, it is checked whether the driver is operating the brake pedal relatively hard. If this is not the case, the program is repeated from step 100 at the next point in time. If the driver is operating the brake pedal relatively hard, the program is again executed at the next point in time, again from the start of the automatic braking force increase in step 106.

If there is already a danger potential from the rear at the beginning of the automatic braking force increase, no braking force increase takes place or a slight braking force increase takes place, that is, the increased braking force is limited. .

[Brief description of the drawings]

FIG. 1 is a time diagram showing the operation of an electrically controlled braking device in a specific driving situation, in which an automatic braking force increase takes place according to the state of the art described above.

FIG. 2 is an overall block circuit diagram of a control device for a brake device in which the above-described control for reducing the risk of a rear-end collision accident is reduced.

FIG. 3 is a time diagram of the operation of the control by the control device of FIG. 2;

FIG. 4 is a flowchart showing a preferred embodiment of control by the control device of FIG. 2 as a computer program.

[Explanation of symbols]

 Reference Signs List 10 Control unit 14 Measuring device (brake pedal) 18 Measuring device (wheel rotation speed) 22 Measuring device (accelerator pedal) 26 Control unit of ACC (Adaptive running speed control device) 30 Video camera (its evaluation unit) 34 Adjustment element Bp Brake pedal position Bk Braking force

Claims (10)

[Claims] In a control method of a brake device for increasing a braking force on at least one wheel independently of a driver in at least one driving situation, when a danger of collision from behind is detected, the driver and the driver are separated from each other. A method of controlling a brake device, wherein the brake force that has been independently increased is reduced or the increase is limited. 2. The method according to claim 1, wherein the reduction or limitation is performed only when the risk of collision from behind is evaluated higher than the risk of collision ahead of the vehicle. 3. The danger from the rear of the vehicle is derived on the basis of at least one value, namely the distance to the vehicle traveling behind the vehicle and / or the relative speed of the vehicle and / or the course of the vehicle. 3. The method according to claim 1, wherein the method comprises: 4. The danger ahead of the vehicle is derived on the basis of at least one signal, namely the distance to the vehicle traveling ahead, the relative speed to this vehicle and / or the course of the vehicle. The method according to any one of claims 3 to 3. 5. The method according to claim 1, wherein the increased braking force is reduced or limited only when a danger from behind is detected and a danger in front of the vehicle is not determined. A method according to claim 1. 6. The reduction or limitation of the increased braking force is reset when there is no danger from the rear and / or when the driver operates the brake pedal in a direction that amplifies the braking action. The method according to any one of claims 1 to 5, characterized in that: 7. The one or more signals from which the danger from behind is inferred from one or more signals are determined by a video camera mounted on the rear of the vehicle. 7. The method according to claim 6. 8. The method according to claim 1, wherein the danger from behind is determined on the basis of a radar, a laser, an ultrasonic transmitter or an infrared radiator. 9. The magnitude of the braking force reduction or braking force limit is a function of the value of the danger of collision from the rear and possibly the value of the danger of driving forward, and / or the braking force is set by the driver. 9. A method according to claim 1, wherein the braking force is not reduced or limited below the applied braking force. 10. In at least one driving situation,
A control device for a braking device, comprising a control unit (10) for increasing a braking force on at least one wheel independently of a driver, wherein a danger of collision from behind is detected and said danger is raised if a danger is detected. A control device for a brake device, further comprising detection means for acting on the control unit so as to reduce or limit the applied braking force.