Methods for monitoring the distance of a vehicle

Abstract

A method for monitoring the distance of a vehicle from an object using a sensor, wherein the time of flight of a signal is detected by the sensor, the distance to a possible object is determined from this, and a warning signal is generated depending on the distance thus determined, characterized in that the detected signal is assigned to at least one of several predefined areas (1, 2, 3, 4, 5, 6, 7) and a fulfillment value (Z) between 0 and 1 for the at least one area (1, 2, 3, 4, 5, 6, 7) is determined from the signal by a membership function, and that the warning signal is triggered depending on the predetermined assignment to at least one individual area (1, 2, 3, 4, 5, 6, 7) and / or the predetermined fulfillment value (Z) of at least one individual area (1, 2, 3, 4, 5, 6, 7).

Description

[0001] The invention relates to a method for monitoring the distance of a vehicle from an object by means of a sensor, in particular designed as an ultrasonic sensor, wherein the time of flight of a signal is recorded by means of the sensor, the distance to a possible object is determined from this and a warning signal is generated depending on the distance thus determined. State of the art

[0002] A device based on this method, known as "Parkpilot," is already widely used with great success and, due to its evident prior use, is considered state of the art. In this known system, distance sensors installed in the rear bumper detect objects behind the vehicle using ultrasonic pulses, similar to sonar. The sensor signals are evaluated in a control unit, which calculates the distance to the nearest detected object. As soon as the calculation indicates that an obstacle is less than, for example, 1.2 meters from the vehicle, a warning signal is issued to the driver in the form of an intermittent tone. The pause between individual tones of the warning signal shortens as the vehicle approaches the obstacle, until the warning signal becomes a continuous tone at a distance of 30 centimeters.At the same time, the distance is displayed on a multi-colored LED display located in the rear of the vehicle.

[0003] German patent DE 198 43 564 A1 describes a warning device for monitoring the distance between a vehicle and an object. This device also measures the vehicle's speed to issue a long-range warning signal even if the measured distance exceeds a threshold, provided there is still a risk of collision. This offers the advantage that the warning device is effective both at close range (less than 1.5 m) and at greater distances (up to approximately 10 m), and in both distance ranges provides the driver with only the necessary warnings of potential obstacles.By generating different warning signals depending on whether an obstacle is in close proximity to the vehicle or at a greater distance from it, it is ensured that the driver can correctly interpret the perceived warning signal and react to it appropriately.

[0004] Distance calculation in ultrasonic parking assist systems is fundamentally based on a mathematically precise calculation of the travel time. In practice, however, cases can occur where the signal return, i.e., the echo, is partially interrupted. A mathematically precise evaluation is not possible in these cases, necessitating the use of special calculation methods. Due to these differing calculation methods, discontinuous results cannot be reliably ruled out, potentially leading to abrupt changes in the calculated distance values. To avoid such abrupt signal transmission, which would be perceptible to the driver, further calculations are performed to smooth these jumps, a process that is quite complex in practice.

[0005] Document DE 199 03 210 A1 discloses a vehicle with an obstacle detection device with ultrasonic wave transmitters / receivers.

[0006] Document US 4,528,563 A discloses a rearward-facing obstacle detection system for a motor vehicle which detects obstacles within several warning zones defined near the vehicle body.

[0007] Document DE 10 2004 050 626 A1 discloses a device for monitoring the environment of a motor vehicle with a first and a second object sensor system for detecting at least one area of ​​the motor vehicle environment.

[0008] Document DE 10 2005 005 309 A1 also discloses a vehicle obstacle detection system. Disclosure of the invention Advantages of the invention

[0009] The inventive method for monitoring the distance of a vehicle from an object, in which the detected signal is assigned to at least one of several predefined areas, and in which the warning signal is triggered depending on the predetermined assignment to at least one individual area or a predetermined fulfillment value of at least one individual area, has the advantage that an unambiguous signal is provided to the driver even when an exact calculation of the distance is not possible or is associated with high effort due to non-linear special cases. In particular, according to the invention, there are no discrete limit values, so that the risk of display jumps is reduced to a minimum. At the same time, the experience of the application engineers can be optimally incorporated into the predetermination of the areas.Furthermore, the procedure can be easily adapted to different vehicles or environmental conditions by changing the individual areas, without requiring a change to the control program.

[0010] The measures listed in the dependent claims enable advantageous further developments and improvements of the invention specified in the independent claim.

[0011] It is particularly advantageous if, from several detected signals from different sensors, an assigned range and / or fulfillment value is determined and the warning signal is triggered based on a logical connection. This easily avoids a discontinuous connection of potentially differing signals from the various sensors, as the connection rules ensure a clear signal for the driver, particularly while preventing discontinuous signal progression.

[0012] According to another promising implementation of the method, the linking is based on Boolean operators, thus allowing simplified programming even for special cases. In particular, complex IF-ELSE statements are eliminated in practice. Operations such as intersection (AND), union (OR), and complement (NOT) are performed. Function classes such as the T-norm, S-norm, and negation can be used to model these operations.

[0013] Furthermore, it proves particularly useful if the output signal emitted by the sensor is additionally assigned to an area in order to improve the assignment of potentially blurred signals and their conversion into a meaningful warning signal for the driver.

[0014] It proves particularly easy if the areas are selected identically in order to counter transition problems in the overlap area and to simplify signal provision.

[0015] In particular, it proves especially advantageous if the signal evaluation is based on an assignment of the signal to fuzzy sets, which serve as the basis for this assignment, already known in principle as fuzzy logic. In contrast to a unique assignment based on mathematical calculations, this allows a signal to be "partially" contained within the fuzzy set. According to the invention, the degree of membership is described by a membership function that assigns a real number between 0 and 1 to the signals of a basic set.

[0016] Another particularly practical implementation of the method is achieved when, based on the sensor's detected signals, either an assignment to a specific area or a mathematical calculation of the distance is performed. This advantageously allows for a mathematically unambiguous distance calculation when this is readily possible due to the signal detection. The delivery of the warning signal to the driver can thus be improved thanks to the precise calculation.

[0017] To quantitatively inform the driver about the estimated distance to the object or the extent of a collision risk, intermittent warning signals can be used for the driver, the period or duty cycle of which can vary depending on the estimated distance or the estimated collision risk.

[0018] Visual and / or audible warning signals are suitable for the driver, so that, for example, an array of LEDs can be used as a warning signal device. The number of illuminated LEDs or their intensity can be used as a measure of the estimated distance, and the LEDs can flash at different periods or duty cycles to signal a risk of collision with an object.

[0019] To avoid disturbing the driver with a prolonged warning signal, a further development of the invention allows the warning signal to be manually interrupted, thus preventing unwanted distraction of the driver from driving. The interruption is automatically lifted, for example, as soon as the object is outside the detection range. Consequently, it is ensured that a warning signal is triggered upon subsequent approach to an object, even if the signal was interrupted during the previous approach.

[0020] According to an advantageous further development, a plurality of similar warning signals are controlled and issued depending on the detected direction of the object in order to indicate this direction to the driver. Brief description of the drawing

[0021] An embodiment of the invention is shown in the drawing and explained in more detail in the following description.

[0022] Each diagram shows the distance and a fulfillment value. Fig. 1. Several areas for different distance ranges of a direct echo of a first signal, Fig. 2 several areas for different distance ranges of a direct echo of a second signal, Fig. 3 several areas for different spacing ranges of a cross-echo of the first and second signals and Fig. 4. An evaluation diagram for determining the obstacle distance. Embodiments of the invention

[0023] The inventive method for monitoring the distance of a vehicle from an object using an ultrasonic sensor is described based on the Fig. 1, Fig. 2 to Fig. Figure 3 describes how each diagram shows different, overlapping areas 1, 2, 3, 4, 5, 6, 7 for different distances plotted on the abscissa. In the Fig. 1 and Fig. In the two diagrams shown for direct signal acquisition using a first and a second sensor, respectively, the ranges 1, 2, 3, 4, 5, 6, and 7 are defined identically and include five further ranges as intermediate stages between range 1 (near range) and range 7 (long range). In contrast, for a [missing information] in the Fig. 3. Diagram of a cross-echo signal shown in the Fig. 1 and Fig. In the diagrams shown, the sensors assigned to areas 1, 2, 3, 4, 5, 6, and 7 are given a different, larger distance. A fulfillment value Z, between 0 and 1, is determined for at least one area from the sensor signals received. The areas 1, 2, 3, 4, 5, 6, and 7 thus determined, or the fulfillment values ​​Z of the two sensors and the cross-echo, are then combined, and a warning signal is triggered for the driver if necessary.

[0024] Examples include the Fig. Figures 1-3 show a graphical representation of the signal acquisition and a derived fulfillment value. The y-axis plots the fulfillment values ​​for each range against the measured distance. For each distance value, a fulfillment value can be determined for the respective range. First, based on ranges 1 and 2 into which the determined signal value falls, one or more applicable rules 1 and 3 are selected from the corresponding rules 1 to 3: Rule 1: If direct echo of the first signal = range 2 and direct echo of the second signal = area 1 and cross-echoes of the first and second signals = area 2 then obstacle distance = area 1 Rule 2: If direct echo of the first signal = range 5 and direct echo of the second signal = range 6 and cross-echoes of the first and second signals = no cross-echo then obstacle distance = range 6 Rule 3: If direct echo of the first signal = range 2 and direct echo of the second signal = area 2 and cross-echoes of the first and second signals = area 1 then obstacle distance = area 2

[0025] Since in the present example no measured value falls into a range affected by rule 2, and thus the membership = 0, rule 2 is not applicable.

[0026] The evaluation according to rules 1 and 3 therefore results for the values ​​shown based on the in Fig. The evaluation diagram shown in section 4 for the obstacle distance to be determined, from which the assignment of the value 15 cm for area 1 and the value 40 cm for area 2 can be seen, is as follows: 0.9*15cm+0.6*15cm+0.3*15cm+0.3*40cm+0.2*40cm+0.1*40cm0.9+0.6+0.3+0.2+0.1=21.25cm

[0027] Here, the results from the Fig. 1 - 3 read-off fulfillment values ​​multiplied by the obstacle distances, which are determined according to rules 1 and 3 taking into account the evaluation diagram. Fig. Each result in 4. The fulfillment values ​​are added together in the denominator.

Claims

[1] Method for monitoring the distance of a vehicle from an object by means of a sensor, wherein the time of flight of a signal is recorded by means of the sensor, the distance to a possible object is determined from this and a warning signal is generated depending on the distance thus determined, characterized by , that the detected signal is assigned to at least one of several predefined areas (1, 2, 3, 4, 5, 6, 7) and a fulfillment value (Z) between 0 and 1 is determined from the signal for the at least one area (1, 2, 3, 4, 5, 6, 7) by a membership function, and that the warning signal is triggered depending on the predetermined assignment to at least one single area (1, 2, 3, 4, 5, 6, 7) and / or the predetermined fulfillment value (Z) of at least one single area (1, 2, 3, 4, 5, 6, 7). [2] Method according to claim 1, characterized by, that from several detected signals from different sensors an assigned area (1, 2, 3, 4, 5, 6, 7) and / or fulfillment value (Z) is determined and the warning signal is triggered due to a logical connection. [3] Method according to claim 2, characterized by that the linking is based on Boolean operators. [4] Method according to at least one of the preceding claims, characterized by that the signal evaluation is based on an assignment of the signal to fuzzy quantities. [5] Method according to at least one of the preceding claims, characterized by , that based on the signals received by the sensor, either an assignment to a range (1, 2, 3, 4, 5, 6, 7) or a mathematical calculation of the distance is performed. [6] Method according to at least one of the preceding claims, characterized by that intermittent warning signals are used for the driver. [7] Method according to at least one of the preceding claims, characterized by that visually and / or audibly perceptible warning signals are generated for the driver. [8] Method according to at least one of the preceding claims, characterized by , that the output of the warning signal can be interrupted manually. [9] Method according to at least one of the preceding claims, characterized by that the sensor is designed as an ultrasonic sensor

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