Method and system for locating an acoustic source relative to a vehicle

Abstract

An improved method for locating an acoustic source relative to a vehicle that requires, for example, only a single microphone is disclosed. The method comprises: obtaining an acoustic signal transmitted by the acoustic source; determining an observer frequency, referenced to the vehicle, of the acoustic signal; stipulating a velocity of the acoustic source; stipulating a relative position of the acoustic source relative to a position of the vehicle; determining a signal frequency; and locating the acoustic source by performing, n times, a Doppler calculation using the determined observer frequency, the stipulated velocity, the determined signal frequency, and the stipulated relative position.

Claims

1. A method for locating an acoustic source relative to a vehicle, the method comprising: obtaining an acoustic signal transmitted by the acoustic source; determining a determined observer frequency, referenced to the vehicle, of the obtained acoustic signal; stipulating a plurality of stipulated velocities of the acoustic source; stipulating a plurality of stipulated relative positions of the acoustic source relative to a position of the vehicle; determining a first determined signal frequency; and locating the acoustic source by performing a plurality of Doppler calculations using the determined observer frequency, the first determined signal frequency, and a plurality of different combinations of velocity and relative position values from the plurality of stipulated velocities and the plurality of stipulated relative positions.

2. The method according to claim 1, wherein at least one of (i) the plurality of stipulated velocities, (ii) the plurality of stipulated relative positions, and (iii) the first determined signal frequency is within a respective associated range of values having a plurality of single values, each respective associated range of values being at least approximately implemented in a current driving situation on which the locating is based.

3. The method according to claim 2 further comprising: limiting, in an iterative exclusion process, the respective associated range of values for at least one of (i) the plurality of stipulated velocities, (ii) the plurality of stipulated relative positions, and (iii) the first determined signal frequency.

4. The method according to claim 1 further comprising: iteratively excluding combinations of at least one of (i) the plurality of stipulated velocities, (ii) the plurality of stipulated relative positions, and (iii) the first determined signal frequency that are inconsistent with the determined observer frequency.

5. The method according to claim 1 further comprising: determining a second determined signal frequency in every n-th Doppler calculation of the plurality of Doppler calculations; and comparing the second determined signal frequency and the first determined signal frequency.

6. The method according to claim 5 further comprising: determining a difference between the second determined signal frequency and the first determined signal frequency from the plurality of Doppler calculations, wherein the locating is performed based on the combination of velocity and relative position values from the plurality of stipulated velocities and the plurality of stipulated relative positions that result in a smallest difference between the second determined signal frequency and the first determined signal frequency.

7. The method according to claim 1, wherein at least one of (i) two successive determinations of the determined observer frequency and (ii) two successive Doppler calculations of the plurality of Doppler clalculations take into account a change of velocity and relative position of the acoustic source.

8. The method according to claim 1, wherein at least one of the acoustic source and the vehicle moves during at least one of the obtaining of the acoustic signal and the locating of the acoustic source.

9. The method according to claim 1, wherein only a single microphone of the vehicle is used for the locating.

10. An apparatus for locating an acoustic source relative to a vehicle, the apparatus comprising: a data processing device configured to: determine a determined observer frequency, referenced to the vehicle, of a recorded acoustic signal transmitted by the acoustic source; stipulate a plurality of stipulated velocities of the acoustic source; stipulate a plurality of stipulated relative positions of the acoustic source relative to a position of the vehicle; determine a first determined signal frequency; and locate the acoustic source by performing a plurality of Doppler calculations using the determined observer frequency, the first determined signal frequency, and a plurality of different combinations of velocity and relative position values from the plurality of stipulated velocities and the plurality of stipulated relative positions.

11. A system for locating an acoustic source relative to a vehicle, the system comprising: an acoustic recording device configured to record an acoustic signal transmitted by the acoustic source; and a data processing device configured to: determine a determined observer frequency, referenced to the vehicle, of the recorded acoustic signal; stipulate a plurality of stipulated velocities of the acoustic source; stipulate a plurality of stipulated relative positions of the acoustic source relative to a position of the vehicle; determine a first determined signal frequency; and locate the acoustic source by performing a plurality of Doppler calculations using the determined observer frequency, the first determined signal frequency, and a plurality of different combinations of velocity and relative position values from the plurality of stipulated velocities and the plurality of stipulated relative positions.

12. The system according to claim 11, wherein a processor of the data processing device executes a computer program.

13. The system according to claim 12, wherein the computer program is stored on a computer-readable storage medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantageous exemplary embodiments of the disclosure are described in detail below with reference to the accompanying figures, in which:

(2) FIG. 1 shows a vehicle having a system that allows an acoustic source to be located relative to the vehicle,

(3) FIG. 2 shows a graph depicting determination and stipulation values or parameters that are used for locating an acoustic source relative to a vehicle,

(4) FIG. 3 shows a graph depicting different determinations of the location of the acoustic source,

(5) FIG. 4 shows a flowchart for a method for locating an acoustic source relative to a vehicle.

DETAILED DESCRIPTION

(6) The figures are merely schematic and not to scale. Throughout the figures, elements that are the same, have the same effect or are similar are provided with the same reference signs.

(7) FIG. 1 shows a vehicle 100, which, in the present case, in exemplary fashion, is a motor vehicle driving in at least partially automated fashion. Accordingly, the vehicle 100 has actuators (not denoted in more detail) and a vehicle drive, these being able to be electronically actuated for the purpose of automated driving control, for example for the purpose of accelerating, braking, steering, etc., the vehicle 100.

(8) The vehicle 100 further has a vehicle system 110, for example in the form of a driving assistance system, which has a data processing apparatus 120, for example in the form of an electronic controller, for actuating the actuators and the vehicle drive, multiple further sensors 130 interacting therewith, such as for example optical sensors, ultrasonic sensors, LIDAR, etc., and an acoustic recording device 140, likewise interacting therewith, for recording sounds, tones or the like from an acoustic source 200 arranged in the vehicle environment, i.e. in exterior surroundings of the vehicle. The acoustic source 200 can be for example another road user, but in particular a service vehicle, such as for example a police vehicle, fire vehicle, emergency service vehicle or the like. The data processing device 120 has a processor 121 and a memory 122 for storing program instructions for operating the vehicle 100. In the present case, the further sensors 130 are, in exemplary fashion, cameras that e.g. optically record the area in front of and behind the vehicle 100 and supply these recording data to the data processing device 120, which can thus steer the vehicle 100 through the vehicle environment, that is to say for example the road traffic.

(9) The acoustic recording device 140 has a plurality of microphones 141. In some exemplary embodiments, the microphones 141 may be oriented toward the outside, in particular in a direction pointing away from the vehicle 100. It should be noted that a single microphone 141 is already adequate in the description below, which means that this hardware costs can be saved.

(10) In particular when using a single instance of the microphones 141 or when using one of the microphones 141, locating the acoustic source 200 relative to the vehicle 100 is a non-trivial problem. In particular in an automated driving mode of the vehicle 100, the locating or the most accurate determination of the location of the acoustic source 200 possible can be used as information for determining the driving strategy, a driving maneuver or the like of the vehicle 100. There follows an explanation that the acoustic recording device 140 can be used to locate the acoustic source 200 at least with sufficient accuracy.

(11) For the purpose of better illustration, FIG. 2 shows a graph having a coordinate system that has an x axis, which specifies a length of displacement in meters (m), for example, and a y axis, which likewise specifies a length of displacement in meters (m). Merely in exemplary fashion, the vehicle 100, which can also be referred to as the ego-vehicle, is arranged at least approximately at the coordinate origin of the coordinate system. The acoustic source 200 is arranged in the first quadrant, that is to say is at a distance from the vehicle 100 both in the X direction and in the Y direction. A current location of the acoustic source 200 can be specified using an x coordinate and a y coordinate in the present case for the purpose of illustration, e.g. as S (x, y). There is a distance d between the vehicle 100 and the acoustic source 200.

(12) It is assumed that either only the vehicle 100 moves, only the acoustic source 200 moves or both the vehicle 100 and the acoustic source 200 move. Depending on the assumption, the vehicle 100 moves with a velocity vector |ν.sub.E | along the y axis, as indicated in the graph. It should be noted that the proper motion of the vehicle 100 is defined as movement in the y direction, which means that the vector velocity vector |ν.sub.E | always points in the same direction. Moreover, the velocity v.sub.E of the vehicle 100 is the velocity component of |ν.sub.E | specified at an angle α (angle with respect to the y axis) in the direction of the acoustic source 200. Similarly, depending on the assumption, the acoustic source 200 moves with an absolute value of the velocity vector |ν.sub.S | at an angle γ (angle in respect of the y axis). An acoustic signal S transmitted by the acoustic source 200 has a velocity v.sub.S in the direction of the vehicle 100.

(13) On the basis of FIG. 2, a Doppler calculation can be performed using equation (1)

(14) $\begin{array}{cc}{f}_s=f_E\frac{c+.Math.\stackrel{.Math.}{v_s}.Math.\cos \left(\gamma -\alpha \right)}{c+.Math.\stackrel{.Math.}{v_E}.Math.\cos \alpha }& \left(1\right)\end{array}$
where f.sub.S specifies a signal frequency of the acoustic signal S, f.sub.E specifies an observer frequency of the acoustic signal S and c specifies the speed of sound. For the purpose of determining the location of the acoustic source 200 on the basis of this equation (1), in particular determining the direction, distance, velocity, direction of movement and/or frequency of the acoustic source 200 or of the acoustic signal S transmitted thereby, the problem exists that the equation has five unknown variables |ν.sub.S |, γ, α, d and f.sub.S, that is to say that the equation is underdetermined. In this case, d describes the distance between the vehicle and the acoustic source. This is necessary in order to be able to calculate changes in the other variables over time.

(15) To solve this problem, the data processing device 120 is configured to limit some of the unknown variables to values or a range of values that is realistic in the driving mode of the vehicle 100, as explained in even more detail later on. Additionally, changes in the Doppler shift determinable by equation (1) are obtained on the basis of a relative movement between the vehicle 100 and the acoustic source 200. A combination of these two effects permits a sufficiently accurate assessment of the five variables, this assessment being able to be taken as a basis for the acoustic source 200 to be located with sufficient accuracy relative to the vehicle 100.

(16) The data processing device 120 is in particular configured to use acoustic recording of the acoustic signal S to determine a value of the observer frequency f.sub.E, referenced to the vehicle 100, of the recorded acoustic signal S. Moreover, the unknown variables are assessed, which means that initially a multiplicity of possible values, e.g. a range of values, of the velocity v.sub.S of the acoustic source 200 are stipulated. In addition, a multiplicity of values, e.g. a range of values, of an acoustic source position of the acoustic source 200 relative to the position of the vehicle 100 are stipulated, wherein the acoustic source position contains an assessment of the aforementioned variables x, y, d, α, in particular. For the processing of these data in the data processing device 120, it is moreover assumed that the velocity and direction of the acoustic source does not change or hardly changes, that is to say is substantially constant, for at least a short period of time. Moreover, it can optionally be assumed that the signal frequency f.sub.S contains repetitive or other known sequences, as is the case in particular with emergency signals from a siren.

(17) The acoustic source 200 is located by the data processing device 120 by virtue of equation (1) being solved for a number of times for a selection of preferably equally spaced, realistic values of f.sub.E, |ν.sub.S |, y, α and d, that is to say iteratively. Between the iterations or iteration steps, a new acoustic source position of the acoustic source 200 is determined on the assumption that at least |ν.sub.S |, y, α and d are provided. If the assumption does not lead to a constant value, or to a value within a specific frequency range, of f.sub.S in a majority of iterations or in all iterations, it is eliminated, so that a smaller number of options remains. From the assumptions with the smallest differences in f.sub.S, the data processing device 120 determines the location, the velocity and the direction of the acoustic source 200, and also the frequency of its acoustic signal S. The data processing device 120 can then provide this information for use in driving strategy planning, driving control or the like for the vehicle 100. As such, the vehicle 100 can also get out of the way of the acoustic source 200 in automated fashion, e.g. by virtue of the route, driving trajectory, etc., being replanned as appropriate.

(18) FIG. 3 illustrates the locating of the acoustic source 200 by the data processing device 120 in a graph. Said graph again has an x axis in the form of a length of displacement in meters (m) and a y axis in the form of a length of displacement in meters (m) and shows the vehicle 100 at least approximately at the coordinate origin of the graph. The reference sign 200 denotes the actual position of the acoustic source, wherein the velocity vector |ν.sub.S | is represented by an arrow in the present case. The reference sign 200′ denotes all possible calculated (estimated) positions of the acoustic source, which, in the present case merely in exemplary fashion, after a number of iterations, have a difference that are below a specific threshold value in the present case. It should be noted that the difference was ascertained by determining the root mean square (RMS), for example. Moreover, it should be noted that, for the sake of clarity, not all of the possible positions are denoted by a reference sign. All arrows not denoted by a reference sign, which in the present case again denote a velocity vector, therefore also correspond to possible positions of the acoustic source 200. The reference signs 200″ indicate those acoustic source positions (determined by the data processing device 120) of the acoustic source that have the smallest difference in the number of iterations and can accordingly be regarded as the most likely position of the acoustic source. In this case too, the respective velocity vector is depicted by an arrow.

(19) FIG. 4 uses a flowchart to summarize a method for locating the acoustic source 200 relative to the vehicle 100. The method is performed in particular using the data processing device 120 described above and the acoustic recording device 140.

(20) A step S1 involves the acoustic signal S transmitted by the acoustic source 200 being obtained. A step S2 involves the observer frequency f.sub.E, referenced to the vehicle 100, of the obtained acoustic signal S being determined, for example recorded or measured. A step S3 involves a velocity v.sub.S of the acoustic source 200 being stipulated. A step S4 involves the acoustic source position x, y, d, α relative to a position of the vehicle 100 being stipulated. A step S5 involves the signal frequency f.sub.S being determined. A step S6 involves the acoustic source 200 being located by means of a Doppler calculation, performed n times, using the observer frequency f.sub.E, the velocity v.sub.S, the signal frequency f.sub.S and the acoustic source position x, y, d, α.