WO2008003364A1

WO2008003364A1 - Ultrasonic sensor, vehicle comprising an ultrasonic sensor and method for operating said ultrasonic sensor

Info

Publication number: WO2008003364A1
Application number: PCT/EP2007/004077
Authority: WO
Inventors: Anton Lill
Original assignee: Valeo Schalter Und Sensoren Gmbh
Priority date: 2006-07-04
Filing date: 2007-05-09
Publication date: 2008-01-10
Also published as: DE102006032125A1; EP2035858A1

Abstract

The invention relates to an ultrasonic sensor for measuring the distance of objects, to a vehicle comprising said ultrasonic sensor in addition to a method for operating said type of ultrasonic sensor.

Description

Title: Ultrasonic sensor, vehicle with ultrasonic sensor and method for operating the ultrasonic sensor

description

The invention relates to an ultrasonic sensor for distance measurement of objects, comprising a converter having a housing and / or a carrier, in which and / or on which a vibratable membrane element is arranged for emitting signals and for receiving the emitted signals reflected on an object is.

Such ultrasonic sensors are known from the prior art in various ways.

FIGS. 1 to 5 show explanations of the prior art.

Figure 1 is a schematic representation of a prior art ultrasonic sensor;

FIG. 2 shows transit times of the signals emitted by the ultrasonic sensor according to FIG. 1, Figure 3 is a plan view of a bumper of a

Vehicle in which known ultrasonic sensors are arranged; and

Figures 4 and 5 triangulations for determining the distance a of an object to the vehicle.

In FIG. 1, a previously known ultrasonic sensor is identified by the reference numeral 10. The ultrasonic sensor 10 comprises a transducer 12, with which electrical signals are converted into sound signals and sound signals into electrical signals. The transducer 12 comprises a housing 14 in which a membrane element 16 with an active surface 17 and an electronics unit 18 are arranged. The electronics unit 18 serves to control the membrane element 16 and to preprocess the signals received by the membrane element 16. The transducer 12 or the membrane element 16 can be controlled via an evaluation unit 20, with which the received signals are evaluated.

The membrane element 16 may be formed according to the prior art as a cup-shaped aluminum part, on which the active surface 17 forming bottom a piezoelectric element is arranged. With appropriate energization of the piezoelectric element, the membrane element 16, or its active surface 17, vibrated and it sound signals are emitted. When on the membrane element 16, or its active surface 17, incident sound signals is the Membrane element 16, or its active surface 17, also vibrated, these vibrations from the piezoelectric element into electrical signals that are preprocessed by the electronic unit 18 and evaluated by the evaluation unit 20, are implemented.

Consequently, the distance a of the sensor 10, or of its membrane element 16, to an object 22 can be determined with such an ultrasonic sensor 10 together with the associated evaluation unit 20. For this purpose, according to FIG. 2, at the time t 1, the acoustic radiation is emitted by the membrane element 16 or its active surface 17 for a short time. At the time t2, these signals strike the object 22 at a distance a. There they are reflected and hit at the time t3 as echo signals again on the membrane element 16, or its active surface 17. In the evaluation unit 20, the transit time of the emitted and then again tl = t3 - tl, with tl: transit time. From the transit time tl and the speed of sound c, the distance a can then be calculated as follows: a = c * tl / 2.

It is known that a plurality of such ultrasonic sensors 10, or associated transducers 12, are accommodated on vehicles, and in particular in bumpers of vehicles. Preferably, an evaluation unit 20 is provided, which controls the individual transducers and evaluates their input signals. Figure 3 shows a schematic plan view of a bumper 24 of a vehicle, which provides a total of four transducers 12.1, 12.2, 12.3 and 12.4. As described for FIG. 2, the direct distance a _< ji or a _d4 from the respective converter 12.2 or 12.4 to the object 22.1 or 22.4 can be determined via the transducers 12.1 to 12.4. This measured distance

corresponds, as is apparent from Figure 3, not the actual distance a _{x of} the obstacle 22.1 to the vehicle. Only in the event that the object 22 lies on the main axis h of the radiation lobe of the respective transducer, the measured distance corresponds to the actual distance.

In order to eliminate this deviation between measured distance a _< u and actual distance ai, the prior art attempts by means of triangulation to calculate the actual distance ai between the vehicle or bumpers 24 and the object 22 from a plurality of measurements with a plurality of transducers.

In the triangulation illustrated in FIG. 4, it is assumed that the object 22 is located at the intersection of two circles K1 and K2, which are respectively arranged around the transducers 12.1 and 12.2, with which the object 22 is detected. The radii of the circles K1 and K2 then correspond to the respectively measured distances a _< n and a _d2 , which are measured by the two transducers 12.1 and 12.2. The actual distance a can then be calculated via the height of the triangle transducer 12.1, 12.2 and object 22. However, this method of triangulation fails when several objects are detected in the field of view of the individual transducers. Such a situation is shown in FIG. A clear assignment, which measured distance a _d n, a _d i ₂ or a _d2 i, a _d2 2 is assigned to which recognized object 22.1 or 22.2, is no longer possible here.

The method of triangulation described above can not be used even if, for example, an object extending over a larger subsection of the detection area, such as a wall, is present.

The present invention is therefore based on the object to provide ultrasonic sensors, by means of which, even in the presence of multiple objects in the detection range of the converter, a clear AbstandsbeStimmung the objects to a vehicle is possible.

This object is achieved by an ultrasonic sensor having the features of claim 1. Such an ultrasonic sensor is characterized in that at least one further membrane element for receiving the signals emitted by the first membrane element and reflected at the object is provided in the housing or on the carrier. Due to the provision of at least two directly adjacent to each other, provided in the same housing or on the same carrier membrane elements, it can be achieved that of only a signal transmitted to a membrane element, which are reflected on the same object, impinge on the two membrane elements with a very small time offset, provided that the object is not arranged in the region of the central longitudinal axis or centrally between the two main axes of the two membrane elements. Consequently, with only one measuring cycle, two distance values identifiable as belonging together are obtained. From these two, only very slightly differing distance values, one can then obtain the position of the object by triangulation.

From the knowledge of the distance between the two membrane elements, or their two main axes, and the transit time difference Δt, the angle α at which the transducer sees the object can be calculated. The associated input signals to the membrane elements, and the resulting associated distance values, can be clearly identified, since the transit time difference

Δt is very low at the very close arranged membrane elements.

In particular, it is advantageous if the distance x between the main axes of the at least two membrane elements arranged in the housing or on the common carrier is less than 10 cm and in particular in the range of 0.5 cm and 5 cm, ie x <10 cm and in particular 0.5 cm <x <5 cm. The distance x can also be selected such that d <x <4 _* d, where d is the diameter or width of the active area a membrane element in the direction of the main axis of the adjacent membrane element. In particular, the value x can be in the range of 2 * d to 3 _* d. By providing these distance values for x, the different transit times of a signal reflected on an object can still be determined with sufficient accuracy.

Preferably, the membrane elements provided are at least substantially identical and / or are the same when providing more than two membrane elements, the distances between adjacent major axes.

Advantageously, the main axes of the emission lobes of the at least two membrane elements run parallel to one another. In this way, a unique local relationship of the two membrane elements to each other can be produced, which is required for determining the respective distance from the respective membrane element to the object.

Advantageously, two further membrane elements can be provided so that the ultrasonic sensor has a total of three membrane elements. The total of three membrane elements can lie on a right-angled, equilateral and / or isosceles triangle. In a right-angled triangle, in a plane perpendicular to the major axis of the first membrane element, a first straight line intersecting the major axis of the first membrane element and the major axis of the second membrane element may be perpendicular to a major axis of the first membrane element and the major axis be arranged of the third membrane element intersecting second straight line. By providing at least a total of three membrane elements, the direction of the object in three-dimensional space can be determined.

Advantageously, the membrane elements can be arranged vertically one above the other in an installed position and / or two membrane elements horizontally next to each other. By providing two membrane elements vertically one above the other, the direction in which the object is present can be determined in a vertical plane. By providing two horizontally juxtaposed membrane elements can be determined in a horizontal plane in which direction the object lies within this plane. By superimposing the two directions determined in the two planes, the direction in three-dimensional space in which the object is present can be determined.

The at least two membrane elements can each be designed as separate, separate components, which are spatially spaced from each other. In particular, a decoupling means for vibration decoupling may be present between the two membrane elements.

In another embodiment of the invention, it is conceivable that the membrane elements are formed as one-piece, consisting of the same material component, said component then has two adjacent cup-shaped membrane recesses. The floors of the Membrane recesses then form the active surfaces. This has the advantage that only one component is to be provided and that the spatial distance of the two membrane recesses can be predetermined.

The component accommodating one membrane element and / or the two membrane elements can have a rectangular or round outer contour in plan view. The plan view is the view along a major axis.

According to a further advantageous embodiment of the invention, the sensor may provide an electronic unit, which is arranged in the housing and / or on the carrier. This electronic unit controls the at least two membrane elements or processes the received signals in such a way that an evaluation unit connected downstream of the electronic unit can evaluate the signals. The membrane elements may in particular be cup-shaped and comprise a piezoelectric element which sets the active surface in oscillation or which converts the oscillations of the active surface of the membrane element into electrical signals.

According to a further advantageous embodiment of the invention, it can be provided that, during operation of the sensor, the at least one further membrane element exclusively receives signals and does not emit any signals. This has the advantage that even comparatively small distances can be determined with the sensor according to the invention. Even if, if the one membrane element which is excited to generate signals is still in its decay phase, signals reflected at an object can be received with the other membrane element which only receives signals. Such a sensor can consequently detect objects in the vicinity of the sensor which a known sensor shown in FIG. 1 can not detect due to the decay time of its only one membrane element.

The sensor according to the invention may comprise an evaluation unit for evaluating the received signals, wherein the evaluation unit during operation of the sensor from the transit time difference of the signals received from the at least two membrane elements, the distance from the respective membrane element to the object and from the distances the direction at least within one of the main axes determined in each case two membrane elements plane, in which the object is detected. Thus, in operation of the sensor, the direction of the object within a plane formed by the major axes of two membrane elements can thereby be determined.

If three membrane elements are provided, the direction of the object in three-dimensional space can be determined in a corresponding manner.

According to a further advantageous embodiment of the invention, it is provided that the evaluation unit in the operation of the sensor, the transit time difference from the phase angle between determines the signals received with the at least two membrane elements. Due to the very low observed differences in transit time at the membrane elements of the delay difference is determined by the phase angle. In this case, phase comparators or phase demodulators can be used. From the wavelength and the phase difference of the received signals, the transit time difference can then be determined with the required accuracy.

The object mentioned at the outset is also achieved by a vehicle, in particular by a motor vehicle having an ultrasonic sensor according to the invention, the evaluation unit determining the actual, shortest distance of the object to the vehicle during operation of the sensor from the transit time difference of the signals received by the at least two membrane elements ,

The above-mentioned object is also achieved by a method for operating an ultrasonic sensor according to the invention, wherein a signal is transmitted with the first membrane element and wherein this signal reflected from the object is received by the first and at least one further membrane element, wherein from the transit time difference of the distance received by the respective membrane element to the object is calculated for the signals received by the at least two membrane elements. In this case, an unambiguous assignment of the associated signals impinging on the membrane elements is readily possible, because these have almost identical transit times due to the spatially adjacent membrane elements.

From the distances of the membrane elements to the object, taking into account two membrane elements, the direction in which the object is detected can be determined at least within a plane formed by the major axes of the two membrane elements.

Advantageously, as already mentioned, the transit time difference can be determined from the phase angle between the signals received by the at least two membrane elements.

Furthermore, as already mentioned, the further membrane element can advantageously serve exclusively for receiving signals. This has the advantage that objects located very close to the sensor can be clearly detected.

Further advantages and advantageous embodiments of the invention will become apparent from the following description, with reference to which various embodiments of the invention are described and explained in detail.

To show:

Figure 6 is a schematic representation of an ultrasonic sensor according to the invention; Figure 7 shows the time course of the sound signals of the ultrasonic sensor according to Figure 6;

FIG. 8 shows different phase shifts on an ultrasonic sensor according to the invention;

Figure 9 received signals of an inventive

Ultrasonic sensor in the presence of multiple objects;

FIG. 10 shows different embodiments of transducers of different ultrasonic sensors according to the invention; and

Figure 11 is a plan view of another ultrasonic sensor according to the invention.

FIG. 6 shows an inventive ultrasonic sensor 30, which differs from the ultrasonic sensor 10 according to FIG. 1 in that two mutually adjacent membrane elements S1 and S2 are provided in the housing 14. The main axes hi and h _{2 of} the two membrane elements Sl and S2 or their active surfaces 17 are arranged parallel to each other. The central main emission axis h lies centrally between the two main emission axes hi and h ₂ . Advantageously, the distance x between the two main emission axes hi and h _{2 is} less than 5 cm and is advantageously in the range between 2 cm and 3 cm. The distance x is greater than the diameter d of the active sensor surfaces 17 and less than twice d.

In the installed position of the ultrasonic sensor 30, the two membrane elements Sl and S2 are advantageously arranged side by side or one above the other.

The membrane element S1 is operated so that it can send and then receive. By contrast, the membrane element S2 can advantageously receive only.

For distance measurement, which is described with the aid of FIGS. 6 and 7, the membrane element S 1 emits a sound signal at the time t i. At time t ₂ , this signal strikes the object 22 at the distance a, where it is reflected. At the time t ₃ , the reflected signal impinges on the membrane element S2 and shortly thereafter, at the time t ₄ on the membrane element Sl. The reflected signals strike the object 22 later than the distance a _S2 from S2 to the object 22 due to the greater distance a _S i from the object 22 to the membrane element _S 1 than to the membrane element _S 2. If the object 22 were located on the main axis h, then the signals reflected at the object 22 would strike the two membrane elements S1 and S2 at the same time.

For each of the two membrane elements Sl and S2 now the duration of the signal can be determined. From this, the respective distance a _S i and a _S2 can be calculated. Overall, therefore, one obtains two associated ones with only one measuring cycle Distance values. The position of the object 22 can be determined by triangulation from these two distance values a _S i and a _S2 and the distance x between the main axes hi and h ₂ . Furthermore, the angle α between the central main axis h and the average distance a _s between the distances a _S i and a _S2 can also be determined in the plane spanned by the two main axes h _λ and h ₂ .

In order to determine the two transit times, which differ only slightly, with sufficient accuracy, it can be provided that the phase difference of the two incoming signals is evaluated. This can be done with phase comparators or phase demodulators. From the wavelength and the phase difference of the received signals, the transit time difference can be determined. For this purpose, three examples are shown in Figure 8, in which the phase angle φ are shown for different positions of the object 22. Depending on the direction and magnitude of the phase shift, it is possible to deduce the associated transit time, and thus the associated angle α.

Even if several objects should be present in the detection range of a transducer, an unambiguous assignment of received signals to an object can be achieved. Since the membrane elements Sl and S2 are arranged close to each other, incoming signals for both membrane elements always come approximately from the same reflection point on the same object. This excludes that intersections are formed with unrelated circles. FIG. 9 shows for example, the transit times at the two membrane elements Sl and S2 for three objects 22.1, 22.2 and 22.3. It becomes clear that for each object present in the field of view of the two membrane elements, there are always incoming signals in pairs, as long as the objects are not located on a circle around the sensor.

The described sensor 30 and the associated method are also suitable for spatially extended objects, such as walls. This is because the measurement is carried out with the two small-spaced membrane elements Sl and S2 in only one measuring cycle, which is based on only one reflection point on the object.

With the sensor according to the invention, moreover, the minimum measurable distance to an object is very small. This is due to the fact that with the provision of two, in particular acoustically well decoupled membrane elements, with the one membrane element a signal can be sent and with the other membrane element, the signal can be received, as long as the first membrane element still swinging. The second membrane element can consequently detect reflected signals, while the first membrane element can not detect such signals due to its decay phase.

If, according to FIG. 6, not only two membrane elements S1 and S2 but also three membrane elements are used which are not arranged along a line, an object can also be clearly recognized within the space via the associated solid angle become. Accordingly, two ultrasonic sensors can be used, wherein one ultrasonic sensor has two membrane elements arranged next to one another and the other ultrasonic sensor has two membrane elements arranged one above the other.

FIG. 10 shows various embodiments of conceivable transducers according to the invention of ultrasonic sensors.

According to FIG. 10 a, it can be provided that a common membrane component 32 is provided which forms the two membrane elements S 1 and S 2 and in particular can be made of aluminum. As is clear from the illustrated cross-section, the component 32 provides two pot-shaped membrane recesses 34 and 36 arranged next to one another. On the side facing away from the active surface 17 of the respective membrane element Sl and S2, a piezoelectric element 38 which can be set into oscillation by energization is arranged at the bottom of the respective membrane recess 34 and 36. The membrane component 32 is located in a housing 40, wherein a decoupling material 42 is provided between the housing 40 and the membrane component 32. In plan view, the membrane component 32 has a round outer contour. The piezoelectric elements 38 are electrically connected to the electronic unit 18, which is not shown in FIG.

The transducer according to FIG. 10b substantially corresponds to the transducer according to FIG. 10a, wherein the outer contour of the Membrane component is not round here, but is substantially rectangular.

The converter according to FIG. 10 c, in which the two membrane elements S 1 and S 2 are accommodated, provides for each of the two membrane elements S 1 and S 2 its own cup-shaped component 44. The two components 44 are surrounded in their respective radially outer region of decoupling material 42, - between the two components 44 is decoupling material 42nd

FIG. 11 shows another ultrasonic sensor 50 according to the invention which has a total of three membrane elements S1, S2 and S3. The ultrasonic sensor 50 is integrated in a bumper 24. In a plane perpendicular to the main axis hx of the membrane element Sl plane is the line g _lf the main axis h _x and the main axis h _{2 of} the membrane _element S2 intersects. Perpendicular to this straight line g _x runs a straight line g _{2 /} which lies in the same plane and the main axis hi and the main axis h _{3 of} the membrane element S3 intersects. In the installation position, therefore, the two membrane elements Sl and S2 are horizontal next to each other and the two membrane elements Sl and S3 vertically above the other. The three, in particular identical, membrane elements S1, S2 and S3 lie in the illustrated view on an isosceles, right-angled triangle. The distance Xi between the main axis hi and the main axis h ₂ corresponds to the distance X _{2 of} the main axis h _x to the main axis h ₃ . The distances Xi and X ₂ are in the range of 2 * d to 3 _* d, where d is the diameter of the active surface 17 of the membrane elements Sl, S2, S3. In the event that the membranes of the membrane elements Sl, S2, S3 have a rectangular contour (indicated by dashed lines in FIG. 11 on the membrane element S2), d is the width of the active surface in the direction of the main axis of the respectively adjacent membrane element.

With such an ultrasonic sensor, a reflection point, and thus an object, can be uniquely determined in three-dimensional space.

Claims

claims

An ultrasonic sensor (30, 50) for measuring the distance of objects, comprising a transducer (12) having a housing (14, 40) and / or a support, in and / or on which a vibratable membrane element

(S L) for emitting signals and for receiving the emitted, on an object (22) reflected signals is arranged, characterized in that in the housing

(14, 40) or at least one further carrier

Membrane element (S2, S3) for receiving the emitted with the first membrane element (Sl) and the object (22) reflected signals is provided.

2. Sensor (30, 50) according to claim 1, characterized in that for the distance x between adjacent major axes

(h _{1 (} h ₂ , h ₃ ) of the at least two membrane elements (Sl, S2, S3) applies: x <10 cm and in particular 0.5 cm <x <5 cm.

3. sensor (30, 50) according to claim 1 or 2, characterized in that for the distance x between adjacent major axes (hi, h ₂ , h ₃ ) of the at least two membrane elements (Sl, S2, S3) applies: d <x <4 _* d, where d is the diameter of the active surface (17) of a membrane element (S1, S2, S3) or the width of the active surface (17) of a membrane element (S1, S2, S3) in the direction of the main axis ( _hx , h ₂ , h ₃ ) of the at least one adjacent membrane element (Sl, S2, S3).

4. Sensor (30) according to claim 1, 2 or 3, characterized in that the main axes (hi, h _{2 /} h ₃ ) of the at least two membrane elements (Sl, S2, S3) parallel to each other.

5. Sensor (30, 50) according to at least one of the preceding claims, characterized in that two further membrane elements (S2, S3) are provided, wherein the total of three membrane elements (Sl, S2, S3) on a rectangular, equilateral and / or isosceles triangle.

6. Sensor (30, 50) according to any one of the preceding claims, characterized in that the at least two membrane elements (Sl, S2, S3) are arranged vertically above one another and / or horizontally next to one another in an installed position.

7. sensor (30, 50) according to at least one of the preceding claims, characterized in that the at least two membrane elements (Sl, S2, S3) are each ausgebidlet as separately formed, spaced from each other spatially arranged components (44).

8. Sensor (30, 50) according to at least one of claims 1 to 6, characterized in that the at least two membrane elements (Sl, S2, S3) as a common, one-piece and made of the same material membrane component

(32) are formed, which has at least two adjacent pot-shaped membrane recesses (34, 36).

9. sensor (30, 50) according to claim 8, characterized in that the membrane component (32) in plan view has a rectangular or round outer contour.

10. Sensor (30, 50) according to at least one of the preceding claims, characterized in that in the housing (14, 40) and / or on the carrier an electronic unit (18) is arranged, which drives the membrane elements (Sl, S2, S3) and / or processes the signals received from the membrane elements (S1, S2, S3).

11. Sensor (30, 50) according to at least one of the preceding claims, characterized in that during operation of the sensor, the at least one further membrane element (S2, S3) exclusively receives signals and does not emit signals.

12. Sensor (30, 50) according to at least one of the preceding claims, characterized in that the sensor comprises an evaluation unit (20) for evaluating the received signals, wherein the evaluation unit (20) during operation of the sensor from the transit time difference of at least two membrane elements (Sl, S2, S3) received signals the distance (a _S i, a _S 2) from the respective membrane element (Sl, S2, S3) to the object (22) and from the distances (a _S i, a _S 2) determines the direction (α) at least within a plane formed by the main axes of each two membrane elements (Sl, S2, S3), in which the

Object (22) is detected.

13. Sensor (30, 50) according to claim 12, characterized in that the evaluation unit (20) during operation of the sensor from the transit time difference in providing three membrane elements (Sl, S2, S3) from the signals received from the three membrane elements the direction within the three-dimensional space in which the object is detected.

14 sensor (30, 50) according to claim 12 or 13, according to any one of claims 10 or 11, characterized in that the evaluation unit (20) during operation of the sensor, the transit time difference from the phase angle between the with the at least two membrane elements (Sl, S2, S3) signals received.

15. Vehicle, in particular motor vehicle, comprising at least one ultrasonic sensor (30, 50) according to at least one of claims 11, 12 or 13, wherein the evaluation unit (20) during operation of the sensor from the transit time difference of the signals received from the at least two membrane elements the actual , shortest distance (a) of the object (22) to the vehicle.

16. A method for operating an ultrasonic sensor (30, 50) according to at least one of claims 1 to 14, characterized in that with the first membrane element (Sl) a signal is emitted and that this at an object (22) reflected signal from the first and is received by at least one further membrane element (S2, S3), wherein from the transit time difference of the distance (a _S i, a _S2 ) received from the respective membrane element (S1, S2, S3) to the object (22) is calculated for the signals received at least two membrane elements (S1, S2, S3).

17. The method according to claim 16, characterized in that from the distances (a _S i, a _S2 ) the direction (α) at least within one of the main axes (hi, h ₂ , h ₃ ) of two membrane elements (Sl, S2, S3) is determined, in which the object (22) is detected.

18. The method according to claim 17, characterized in that the transit time difference is determined from the phase angle between the signals received by the at least two membrane elements.

19. The method according to claim 17 or 18, characterized in that the at least one further membrane element (S2, S3) exclusively receives signals and does not emit signals.