GB2512440A

GB2512440A - Driver assistance system

Info

Publication number: GB2512440A
Application number: GB1400811.4A
Authority: GB
Inventors: Dirk Schmid; Burkhard Iske; Michael Schumann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-01-18
Filing date: 2014-01-17
Publication date: 2014-10-01
Anticipated expiration: 2034-01-17
Also published as: DE102013200793A1; GB201400811D0; FR3001189A1; FR3001189B1; GB2512440B

Abstract

According to the invention a driver assistance system for assisting a driver of a vehicle 1 is proposed, having at least one sensor group 5, 60, 70, which comprises at least one first ultrasonic sensor 10, 10' of a first type and at least one second ultrasonic sensor 20, 20' of a second type. The ultrasonic sensors are disposed in such a way that they have at least partially overlapping sensing ranges 12, 22. According to the invention the ultrasonic sensors of the first type are configured to sense a short range and the ultrasonic sensors of the second type are configured to sense a long range. A control unit 50 drivers the sensors and evaluates the echo signals, which are combined to produce a continuous and gap-free sensing range. The groups of sensors can be placed at both the front and rear of the vehicle. The short range sensors can have a lower sensitivity than the long range sensors, and can be operated at a different frequency. Alternatively the signals can be emitted separately from one another in respect of time.

Description

Description Title

Driver assistance system

Background art

Ultrasonic sensors that operate on the echo-sounding principle are meantime not only being used for the known park assist system but also form the standard measuring system for sensing the surrounding area for a large number of further driver assistance systems. Examples of these are park assist (sensors gauge the parking space as the vehicle drives past and the vehicle steers automatically while manoeuvring into the parking space) or side view assist (indication of overtaking vehicles in the blind spot) Thus for example from DE 10 2004 047 479 Al a method of classifying lateral delimitations of a parking space for a park assist system of a motor vehicle is known. A vehicle has one front and one rear distance sensor for each side of the vehicle. The distance sensors take the form of ultrasonic sensors. As the vehicle drives past a parking space, the length and depth of the parking space Is scanned by means of the distance sensors. With the aid of the rear distance sensor determination of the lateral delimitation of the parking space is additionally effected.

DE 10 2007 002 738 Al describes a method of assisting a parking operation, whereby objects that are situated in the area surrounding the vehicle are differentiated with regard to their state of motion. This makes it possible for example to blank out moving traffic. For this purpose, in the course of gauging the parking space ultrasonic sensors of a blind-spot detection system are utilized. If for example the vehicle to be parked is being overtaken by a vehicle at a side remote from the parking space, the overtaking vehicle is identified as a moving object by means of the blind-spot detection system and therefore ignored.

In the near future further functions that are likewise based on object detection by means of ultrasonic sensors will be realized, such as ACC pull-away assistance, pedestrian detection, automatic "garage parker" or pre-crash detection.

This broadening of the functional spectrum means that increased demands will be placed on the ultrasonic sensor equipment. In particular, extending the sensing range to include greater measuring distances presents difficulties here since for the basic park assist function", for which the employed ultrasonic sensors were originally developed, the priority is coverage of a short range (approximately 0.1 m -2.5 m). If the sensing range of the sensors is to be increased, a compromise has to be reached at least with regard to the following design-and/or dimensional characteristics: Beam angle of the sound cone: For gap-free short-range coverage the beam angle should be as large as possible. To achieve a high sensing range, however, it should be narrow and focussed in the main sensing direction in order also to avoid unwanted echoes from lateral objects located far away.

Duration and maximum power of the sending pulse: In order to minimize the blind zone immediately in front of the sensor diaphragm after emission of the acoustic pulse, the pulse has to be as short as possible, for example between 150 ps and 400 ps. Pulses as short as this result in good short-range coverage. However, in order to achieve a high sensing range, the pulse should be as long as possible, for instance up to 2 ms, and contain a great deal of energy (power) These two dimensional characteristics are linked with further sensor properties, such as for example the diaphragm geometry, the power input, and they therefore also directly influence the manufacturing costs incurred.

If the entire detection range from short range to long range is to be covered by a single type of ultrasonic sensor, the sensor design will always entail a compromise between the possible extremes. The optimum simultaneous fulfilment of conflicting reguirements also inevitably leads to higher costs for development and manufacture than would be the case with optimization for a specific detection range.

Disclosure of the invention

Tn order to avoid the drawbacks of the known systems, according to the invention a driver assistance system for assisting a driver of a vehicle is proposed, having at least one sensor group, which comprises at least one first ultrasonic sensor of a first type and at least one second ultrasonic sensor of a second type. The ultrasonic sensors are disposed in such a way that they have at least partially overlapping sensing ranges. According to the invention the ultrasonic sensors of the first type are configured to sense a short range and the ultrasonic sensors of the second type are configured to sense a long range. Here, by short range is meant a range of ca. 0.1 to 2.5 metres from the appropriate ultrasonic sensor. By long range is meant a range of ca. 1 to 8 metres.

The driver assistance system preferably comprises a control unit, which is configured to drive the various ultrasonic sensors and to evaluate the echo signals received by the ultrasonic sensors in order to draw conclusions about objects in the sensing range of the ultrasonic signals. As a result of the overlapping sensing ranges the echo signals may be combined in such a way as to produce a continuous and gap-free total sensing range.

The object of the invention is to disentangle the conflicting requirements of ultrasonic sensors for sensing the short range and the long range by employing two different variants of ultrasonic sensor. The first variant (type 1) is optimized for the short range, the second variant (type 2) for the long range.

What is new is the special arrangement of the two sensor types in a sensor group, wherein the two types have partially overlapping sensing ranges. Both sensor types are preferably connected to the same control device, in which the echo signals of the two sensor types are combined in such a way as to produce a continuous and gap-free sensing range.

By bringing together the sensing ranges of both sensor types in one control device the advantages of both types are combined without having to accept their drawbacks.

Sensor type 1 may be optimized for the short range, sensor type 2 for the long range.

In a preferred embodiment of the invention at least two sensor groups (also referred to as sensor clusters) are provided, wherein a first sensor group is disposed at the rear of the vehicle and a second sensor group is disposed at the front of the vehicle. Each sensor group has both ultrasonic sensor types.

The different sensor types are differentiated for example by the following parameters: Type 1: * large sound beam angle (horizontal ca. ii 600, vertical ± 30°), * short original acoustic pulse (ca. 300 jas) , nean transmitting power, low transmitting energy, * high attenuation, short reverberation time after transmission (less than 1 ms) but low sound pressure (cc.

2 Pa at 30 cm distance) and lower sensitivity of reception.

Type 2: * small sound beam angle (horizontal ca. ± 30° or less, vertical ca. ± 15°), * long original acoustic pulse (ca. 1-2 ms), high transmitting power, high transmitting energy, * low attenuation, hence longer reverberation time after transmission, but higher sound pressure (mm. 3 Pa at 30 cm distance) and higher sensitivity of reception.

It is also possible to make the external dimensions of the sensor and the mechanical construction identical for both sensor types, with the result that it is possible to present an approximate shared-component approach. This means that many mechanical structural elements, for example the sensor housing and the mounting, may be identical while only sound transducers and electronics are different. It is therefore possible to reduce the complexity of manufacture and the cost of the driver assistance system and the costs compared to conventional systems. A differentiation may be achieved by mechanically coding the housing/mounting, for example by means of grooves and pins at various positions, or by means of differences in the data protocol at the interface between sensor and control device.

This separate optimization leads to better results and lower overall costs than a compromise design with only one sensor type. Among other things, the following assistance functions may therefore be presented better than before: * ACO pull-away assistance: improved free-space definition as a result of higher sensing range, more redundancy in the overlapping range of the ultrasonic sensors, i.e. more robust definition possible * improved blindness detection by means of redundant sensors * earlier detection of pre-crash situations and hence extension to higher speed range possible.

* functions with brake intervention may be realized also at higher speeds (extension of speed range) * improved SVA funotion with higher sensing range and earlier warning for the driver * improved gauging (orientation of the parking space and obstruction detection) for transverse parking spaces * improved function display for Back Over Avoidance as a result of gap-free coverage of the rear space of 0.1 m to 6 m and simultaneous delimitation of the lateral detection zone to the travel path of the vehicle.

The first and the seoond ultrasonic sensors are preferably controlled in such a way that they do not mutually influence one another, for example in that they are driven to emit ultrasonic pulses one after the other or in that they transmit at different frequencies.

In an advantageous manner, given a use of overlapping frequency ranges for the first and the second ultrasonic sensors cross-echoes between the two sensor types may be evaluated, thereby increasing the reliability of detection and also enabling object height estimation by means of vertical trilateration.

Brief description of the drawings

Figure 1 diagrammatically shows a side view of a vehicle with a driver assistance system according to a first embodiment of the invention.

Figure 2 diagrammatically shows in plan view a vehicle with a driver assistance system according to a second embodiment of the invention.

Embodiments of the invention A first embodiment of the invention is represented in Figure 1. A vehicle 1 is eguipped with a driver assistance system according to the invention. For this purpose a first ultrasonic sensor of a first type 10 and a second ultrasonic sensor of a second type 20 are disposed at the rear of the vehicle 1. The two ultrasonic sensors 10 and form a sensor group 5. The two sensor types in the present case are installed at different heights h, h' above the ground. The sensors are therefore arranged spaced vertically apart from one another. The first ultrasonic sensor 10 is configured to sense a short range 12, the second ultrasonic sensor 20 is configured to sense a long range 22. According to the invention the measuring ranges 12 and 22 have an overlap, thereby producing a continuous total measuring range.

Depending on the height of the reflex point on the respective object 30 and/or 40 the sound paths d, d', d" between objects 30 and 40 and the ultrasonic sensors 10 and differ in length. From the difference of the sound paths d, d', d" and the difference of the installation heights h, h' conclusions may be drawn about the height of the reflex point by means of trigonometric functions (known method of trilateration) . The trilateration between two sensors has already been used in a horizontal plane for many years as a standard method in parking assistance in order to calculate the two-dimensional position of an object in the horizontal plane (parallel to the ground) An additional useful effect arises in this embodiment due to the fact that the sensing ranges in the vertical direction do not fully overlap. Thus, the smaller object of the two represented objects 30, 40 dips through in the short range 12 below the sound cone 22 of the second ultrasonic sensor 20 and is therefore detected only by the first ultrasonic sensor 10. This is recorded by a control unit 50 (not visible in this representation) and evaluated as indicative of a comparatively low object height.

It is conceivable for the two ultrasonic sensors 10 and 20 to be operated at different freguencies. This allows a separation and association of the received echo signals.

In the case of non-overlapping freguency ranges it is moreover possible to increase the send blast rate and hence reduce the response time. Both sensor types may then send simultaneously without mutually interfering with one another.

Alternatively, given a use of overlapping freguency ranges (for example typical working ranges may be 45 -55 kHz for type 1 and 40 -50 khz for type 2) for the first and second ultrasonic sensors cross-echoes between the two sensor types may be evaluated, thereby increasing the reliability of detection and also enabling object height estimation by means of vertical trilateration.

A further advantageous arrangement of ultrasonic sensors of the different types according to the invention is shown in plan view in Figure 2. In this embodiment two sensor groups 60, 70 are provided. A first sensor group 60 is disposed at the rear of the vehicle 1 and comprises four ultrasonic sensors 10 of the first type for sensing the short range and four ultrasonic sensors 20, 20' of the second type for sensing the long range. According to the invention the ultrasonic sensors 10 and 20 are arranged in such a way as to produce overlapping sensing ranges 12 and 22. A second sensor group 70 is disposed at the front of the vehicle 1 and comprises six ultrasonic sensors 10, 10' of the first type for sensing the short range and two ultrasonic sensors 20 of the second type for sensing the long range. A control unit 50 controls all of the ultrasonic sensors 10, 10', 20, 20' and evaluates the received signals. Objects in the area surrounding the vehicle may be detected and the information may be used for various drive assist functions.

With the arrangement represented in Figure 2 different functions may be realized. The two ultrasonic sensors 20 of the second type in the second sensor group 70 (front cluster) that are aligned in the direction of travel enable optimum coverage of the travel path in forward direction for the funotions ACO pull-away assistance, pre-crash detection and parking brake assist.

The narrow sound cone (corresponding to the sensing range 22) of the second type enables an easy association of the detected objects with the travel path. Horizontal trilateration is not necessary for this purpose, with the added result that no lateral measuring errors may arise.

The gap-free coverage of the travel path right up to the bumper is guaranteed by the six ultrasonic sensors 10, 10' of the first type. These also enable the basic park assist function.

In the first sensor group 60 (rear cluster) the two ultrasonic sensors 20 of the second type that are aligned counter to the direction of travel may be used for pre-crash detection and parking brake assistance. The ultrasonic sensors 20' that are aligned obliquely rearwards at the corners may be used for example for a Side View Assist (SVA) function or a lane change assist function with a higher sensing range than previously.

The system configuration of Figure 2 is only an example of a particularly advantageous embodiment. The number of ultrasonic sensors of type 1 and type 2 within a sensor group, the arrangement of the sensors and/or the number of sensor groups may vary from vehicle to vehicle.