DE102014107304B4 - Sensor arrangement with an ultrasonic sensor with storage device for a motor vehicle and motor vehicle - Google Patents

Abstract

Sensor arrangement (2) with at least one ultrasonic sensor (3) for a motor vehicle and an evaluation device (4),
wherein the ultrasonic sensor (3) comprises a transmitting device (8) for emitting ultrasonic waves, wherein the transmitting device (8) has a membrane and an actuating unit with which the membrane is movable for emitting the ultrasonic waves,
wherein the ultrasonic sensor (3) comprises a memory device (9) in which at least one operating parameter of the ultrasonic sensor (3) is stored,
wherein as the at least one operating parameter of the ultrasonic sensor (3) at least one resonance value (fR) is stored in the memory device (9), which describes a resonance frequency of the transmitting device (8),
wherein the evaluation device (4) is designed to receive the at least one resonance value (fR) stored in the memory device (9) from the ultrasonic sensor (3),
characterized in that
at least one desired value (f _soll ) for the resonance frequency of the transmitting device (8) of the ultrasonic sensor (3) is stored in the evaluation device (4) and the evaluation device (4) is designed to replace the at least one desired value (f _soll ) with the at least one received resonance value (fR).

Description

The present invention relates to an ultrasonic sensor for a motor vehicle, comprising a transmitting device for emitting ultrasonic waves, wherein the transmitting device has a membrane and an actuating device with which the membrane can be moved to emit the ultrasonic waves, and comprising a memory device on which at least one operating parameter of the ultrasonic sensor is stored. Furthermore, the present invention relates to a sensor arrangement comprising an ultrasonic sensor and an evaluation device. Furthermore, the present invention relates to a motor vehicle with such a sensor arrangement. Finally, the present invention relates to a method for producing an ultrasonic sensor for a motor vehicle.

Since ultrasonic sensors are increasingly being used beyond their actual parking assistance functionality, such as for driving assistance with active braking interventions based on a detected risk of collision, it must be ensured during vehicle operation that the ultrasonic sensors on the vehicle can reliably detect obstacles in the vehicle's vicinity and reliably measure distances up to a predetermined range. If the ultrasonic sensors are blocked, i.e., covered by an additional mass, such as dirt, snow, and/or ice, this functionality can no longer be guaranteed.

Methods for detecting a blocked state of an ultrasonic sensor are already known from the prior art. The known methods for detecting ice or dirt are fundamentally based on the evaluation of side effects caused by the additional mass on the ultrasonic sensor. For example, an additional mass influences the so-called decay time of the membrane of the ultrasonic sensor or generates a virtual echo or a pseudo-echo, which can be detected by appropriate evaluation of the electrical received signal of the ultrasonic sensor. However, in the worst case scenario, the additional mass can neither change the decay time of the membrane nor cause additional echoes. In such situations, the blocked state of the ultrasonic sensor cannot be detected, and the sensor is no longer able to detect a real object or reliably measure distances.

In this context, the DE 10 2009 040 992 A1 The proposed method involves recording the decay time of the ultrasonic sensor following membrane excitation and comparing it with the excitation frequency. Depending on the result of this comparison, it is determined whether the ultrasonic sensor is blocked or not.

Furthermore, the DE 10 2010 021 960 A1 A method in which the oscillation time of the membrane is evaluated over several measurement cycles of the ultrasonic sensor to detect the blocked state of an ultrasonic sensor. The measurement of the change in the resonance frequency of the ultrasonic sensor and the resulting deviation from a fundamental resonance frequency without contamination depend on various factors. For example, the temperature and a related change in the mechanical properties of the ultrasonic sensor or the membrane can play a role. Such a change in the resonance frequency due to temperature influences can be corrected using existing temperature information, which is stored, for example, in an evaluation device.

A very large and currently uncorrectable influencing factor are the component tolerances of the ultrasonic sensor itself. In particular, the membranes of ultrasonic sensors can exhibit large tolerances after production due to variations in shape and strength or thickness. The total tolerance for the resonance frequency can, for example, be in the range of several hundred Hz or even in the range of several kHz. It should be noted that the ultrasonic sensor has a bandwidth in the range of +/- 2 kHz. Frequency shifts that can occur due to contamination or blockage of the membrane can lie within these tolerances.

This provides some relief in the document DE 102 47 971 A1 The method described above involves measuring the natural frequency or resonance frequency of the ultrasonic sensor and comparing it with stored reference values. To determine the resonance frequency of the ultrasonic sensor, the sensor is excited and the decay frequency is measured. This decay frequency or the resonance frequency of the ultrasonic sensor is stored in a memory device, for example, an EEPROM, of a motor vehicle control unit.

From the DE 102 36 879 A1 An obstacle detection device and a related communication device are known.

From the US2007157728 A1 An ultrasonic distance sensor is known. The frequency of the transmitted signals and a frequency range of the received signals are controlled depending on the ambient temperature so that they always match a resonant frequency of the bulkhead, which changes depending on the ambient temperature.

From the DE 102012220311 A1 is a method for detecting sensor degradation in distance sensors, comprising the following steps: a) transmitting at least one transmission pulse; b) detecting a sensor signal at least in one decay interval; and c) determining a degree of degradation based on a frequency response of the detected sensor signal.

It is the object of the invention to show a solution how an ultrasonic sensor of the type mentioned at the beginning can be operated more reliably and how, in particular, a blocked state of the ultrasonic sensor can be determined more precisely.

This object is achieved according to the invention by a sensor arrangement with an ultrasonic sensor and by a motor vehicle having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

A sensor arrangement according to the invention comprises at least one ultrasonic sensor according to the invention and an evaluation device. The evaluation device is designed to receive the at least one resonance value stored in the memory device from the ultrasonic sensor. In other words, the at least one resonance value is transmitted from the ultrasonic sensor or the memory device of the ultrasonic sensor to the evaluation device. The evaluation device can, in particular, be a central control unit of the motor vehicle, which is also referred to as an Electronic Control Unit (ECU). The sensor arrangement can also comprise several of the ultrasonic sensors according to the invention. Thus, each of the ultrasonic sensors can transmit its resonance value to the evaluation device. In this way, the evaluation device can reliably control the individual ultrasonic sensors depending on their resonance frequency.

An ultrasonic sensor according to the invention for a motor vehicle comprises a transmitting device for emitting ultrasonic waves, wherein the transmitting device has a membrane and an actuating device with which the membrane can be moved to emit the ultrasonic waves, and a memory device on which at least one operating parameter of the ultrasonic sensor is stored, wherein as the at least one operating parameter of the ultrasonic sensor at least one resonance value is stored on the memory device, which describes a resonance frequency of the transmitting device.

According to the invention, at least one target value for the resonance frequency of the transmitting device of the ultrasonic sensor is stored in the evaluation device, and the evaluation device is designed to replace the at least one target value with the at least one received resonance value. For example, a target value for the resonance frequency of the ultrasonic sensor can be stored in a memory unit of the evaluation device, which is used to control and/or evaluate the sensor signals of the ultrasonic sensor. This value can then be replaced by the at least one resonance value transmitted from the ultrasonic sensor to the evaluation device. In this way, the ultrasonic sensor can be operated more reliably.

The invention is based on the finding that ultrasonic sensors typically have a memory device. Operating parameters of the ultrasonic sensor can be stored on this memory device. For example, manufacturer-specific data such as the country, line, and/or plant in which the ultrasonic sensor was manufactured can be stored. In this case, at least one resonance value is additionally stored in the memory device. This at least one resonance value describes a resonance frequency or a natural frequency of the transmitting device of the ultrasonic sensor. The transmitting device comprises the membrane and the actuating device, with which the membrane can be set into mechanical vibration. The membrane and the actuating unit thus form an oscillatory system that has a mechanical resonance frequency. This resonance frequency is measured, in particular, after the ultrasonic sensor has been manufactured and stored in the memory device. Thus, for example, an evaluation device or a control unit of the motor vehicle can access this resonance value and use it to operate the ultrasonic sensor. In this way, the ultrasonic sensor can be operated reliably depending on its actual resonance frequency.

Preferably, the memory device contains a first resonance value which describes a first resonance frequency of the transmitting device at a first temperature, and at least one second resonance value which describes a second resonance frequency frequency of the transmitting device at a second temperature different from the first temperature. In other words, a plurality of resonance values, each determined at different temperatures, can be stored in the memory device. This takes into account that the resonance frequency of the ultrasonic sensor or of the transmitting device can change due to a change in temperature. This can be due to the temperature dependence of the material stiffness (modulus of elasticity) of the transmitting device itself and/or the adjacent components. In this way, the temperature influence on the resonance frequency of the transmitting device can be reliably taken into account.

The storage device is preferably designed as a non-volatile memory. In such a non-volatile memory, which can also be referred to as a read-only memory, the stored information can be retained even when the ultrasonic sensor is not currently in operation or not supplied with electrical power. For example, the storage device can be designed as an EPROM memory, a flash memory, a ROM memory, an OTP memory, or the like. This ensures that the at least one resonance value is reliably stored in the storage device of the ultrasonic sensor.

Preferably, the transmitting device and the storage device are arranged on a common carrier element and/or in a common housing. The transmitting device and the storage device of the ultrasonic sensor can be arranged, for example, on a common circuit board. Alternatively or additionally, the transmitting device and the storage device can be arranged in a common housing. Furthermore, further components or parts of the ultrasonic sensor can be arranged on the carrier element or in the housing. Thus, a space-saving ultrasonic sensor can be provided which additionally comprises a storage device in which the resonant frequency of the transmitting device of the ultrasonic sensor is stored.

Furthermore, it has proven advantageous if the ultrasonic sensor has a temperature detection device for detecting the temperature of the ultrasonic sensor. The temperature detection device can also be arranged in the carrier element of the ultrasonic sensor or in the housing of the ultrasonic sensor. In particular, the temperature detection device is designed to determine a temperature of the transmitting device of the ultrasonic sensor. In this way, the current temperature of the transmitting device can be reliably determined. This information can be taken into account, for example, in addition to the at least one resonance value that describes the resonance frequency of the transmitting device at the currently detected temperature or in a range of the currently detected temperature.

The ultrasonic sensor preferably has an interface for outputting the at least one resonance value stored in the memory device. In other words, a communication interface is provided by means of which the at least one resonance value can be transmitted to an evaluation device of the motor vehicle. This interface can, for example, be connected to the CAN bus of the motor vehicle. In this way, the resonance value stored in the memory device can be easily made available.

In one embodiment, the evaluation device is designed to control the transmitting device of the ultrasonic sensor depending on the at least one received resonance value. For example, the control unit of the transmitting device can be controlled by the evaluation device such that it operates at its determined resonance frequency. In this way, the transmitting device can be operated energy-efficiently.

In a further embodiment, the evaluation device is designed to determine the transmitting device of the ultrasonic sensor for determining a current resonance frequency of the transmitting device. Based on this, the current resonance frequency of the transmitting device can be determined.

Preferably, the evaluation device is designed to determine a blocked state of the ultrasonic sensor based on a comparison of the currently determined resonance frequency and the at least one received resonance value. In the blocked state, the transmitting device of the ultrasonic sensor can be obscured by an additional mass, such as dirt, snow, and/or ice. In this way, the current resonance frequency of the ultrasonic sensor is changed. Based on a comparison of this current resonance frequency and the resonance frequency stored in the memory device of the ultrasonic sensor, a blocked state of the ultrasonic sensor can be reliably determined.

The motor vehicle according to the invention comprises the sensor arrangement according to the invention. The evaluation device of the sensor arrangement is preferably designed to determine a blocked state of the ultrasonic sensor when the ignition of the motor vehicle is activated. Thus, it can be determined, especially before starting a journey with the motor vehicle, whether the at least one ultrasonic sensor is blocked or not. In this case, the driver can be informed, for example, by a corresponding display, that the at least one ultrasonic sensor is blocked. This can increase safety during operation of the motor vehicle.

A method for producing an ultrasonic sensor of a motor vehicle comprises providing a transmitting device of the ultrasonic sensor, providing a storage device of the ultrasonic sensor, arranging the transmitting device and the storage device on a common carrier element, determining at least one resonance frequency of the transmitting device, determining at least one resonance value based on the at least one determined resonance frequency and storing the at least one determined resonance value in the storage device.

After the individual components of the ultrasonic sensor have been assembled, the resonance frequency of the transmitting device is determined and stored in the memory. Furthermore, other operating parameters, such as the transmitted sound intensity and the received sensitivity, can also be stored in the memory. In addition to the resonance value, the tolerance value can also be stored in the memory. This value describes the difference between the determined resonance frequency and a target resonance frequency of the transmitting device. Thus, the component tolerances of the transmitting device can also be stored in the memory.

The preferred embodiments presented with reference to the ultrasonic sensor according to the invention and their advantages apply accordingly to the sensor arrangement according to the invention, the motor vehicle according to the invention and the method.

Further features of the invention emerge from the claims, the figures, and the description of the figures. All features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures, can be used not only in the respective specified combination, but also in other combinations or even on their own.

The invention will now be explained in more detail using a preferred embodiment and with reference to the accompanying drawings.

• 1 in schematischer Darstellung ein Kraftfahrzeug mit einer Sensoranordnung gemäß einer Ausführungsform der Erfindung;
• 2 in schematischer Darstellung einen Ultraschallsensor der Sensoranordnung, der eine Speichereinrichtung, eine Temperaturerfassungseinrichtung und eine Schnittstelle aufweist; und
• 3 einen Graphen, der eine Anpassung eines in einer Auswerteeinrichtung der Sensoranordnung hinterlegten Soll-Werts für die Resonanzfrequenz einer Sendeeinrichtung des Ultraschallsensors beschreibt.

They show:

• 1 a schematic representation of a motor vehicle with a sensor arrangement according to an embodiment of the invention;
• 2 in a schematic representation of an ultrasonic sensor of the sensor arrangement, which has a memory device, a temperature detection device and an interface; and
• 3 a graph describing an adjustment of a target value stored in an evaluation device of the sensor arrangement for the resonance frequency of a transmitting device of the ultrasonic sensor.

One in 1 The motor vehicle 1 shown is, for example, a passenger car. The motor vehicle 1 comprises a sensor arrangement 2, which has a plurality of ultrasonic sensors 3 and an electronic evaluation device 4, which can be designed, for example, as a control unit. The number and arrangement of the ultrasonic sensors 3 are shown in 1 are shown merely by way of example and may vary depending on the embodiment. In this exemplary embodiment, a plurality of ultrasonic sensors 3 are arranged on a front bumper 5 of the motor vehicle 1; a plurality of ultrasonic sensors 3 are also arranged on a rear bumper 6 of the motor vehicle 1.

With regard to the installation of the ultrasonic sensors 3, two alternative embodiments can be provided. On the one hand, the ultrasonic sensors 3 can each be arranged in a recess of the respective bumper 5, 6, so that the transmitting device of the respective ultrasonic sensors 3 is arranged within the respective continuous recess of the bumpers 5, 6. On the other hand, however, a concealed installation of the ultrasonic sensors 3 behind the respective bumpers 5, 6 can also be provided, so that the transmitting device of the ultrasonic sensors 3 is located on the rear side of the respective bumper 5, 6, and the ultrasonic signals are transmitted and received through the material of the bumper 5, 6.

The ultrasonic sensors 3 are each designed to detect distances to obstacles located in the vicinity of the motor vehicle 1. The measured distance values are transmitted from the ultrasonic sensors 3 to the evaluation device 4, which processes the measured values of the ultrasonic sensors 3. In the motor vehicle 1, several driver assistance systems 7a to 7x can be provided, which are designed to provide different functionalities in the motor vehicle 1, based on the measured distances of the ultrasonic sensors 3. In 1 The different driver assistance systems 7a to 7x are shown as separate components; however, multiple functionalities can also be provided by a common control unit, which then assumes the function of multiple driver assistance systems. The following systems, for example, can be provided as driver assistance systems 7a to 7x: a parking assistance system in which the measured distances are output acoustically and/or visually, an automatic parking assistance system for automatic parking, an automatic braking assistance system, which serves to automatically brake the motor vehicle 1 based on the risk of collision detected based on the measured values of the ultrasonic sensors 3, a blind spot monitoring system, a distance maintenance system, a collision detection system, and the like.

In 2 A highly simplified top view of an ultrasonic sensor 3 is shown. The ultrasonic sensor 3 comprises a transmitting device 8, which serves to transmit an ultrasonic signal. For this purpose, the transmitting device 8 comprises a membrane (not shown here) which can be moved or set into mechanical vibration by an actuating unit. The membrane can be made of aluminum, for example, and the actuating unit can comprise a corresponding actuator, for example a piezoelectric actuator. The membrane and the actuating unit thus form an oscillatory system that has a resonant frequency. This resonant frequency can be between 40 kHz and 60 kHz, for example. Due to manufacturing tolerances during the manufacture of the transmitting device 8, and in particular of the membrane, this resonant frequency can deviate from a target value. The ultrasonic sensor 3 also comprises a memory device 9. The memory device 9 can in particular be designed as a non-volatile memory. The transmitting device 8 and the memory device 9 are arranged together in a housing of the ultrasonic sensor 3.

In order to take into account the tolerances of the resonance frequency of the transmitting device 8, the resonance frequency of the transmitting device 8 is measured after the ultrasonic sensor 3 has been manufactured. For this purpose, the membrane can be excited using the actuating unit and a decay frequency of the transmitting device 8 can be determined. Based on the measured resonance frequency of the transmitting device 8, at least one resonance value fR is determined and stored in the memory device 9 of the ultrasonic sensor 3. The resonance value fR describes the determined or measured resonance frequency of the transmitting device 8. In particular, it is also provided that the resonance frequency of the transmitting device 8 is measured at different temperatures T and that a resonance value fR is determined for each predetermined temperature and stored in the memory device 9.

In addition, the ultrasonic sensor 3 comprises a temperature detection device 10. The temperature detection device 10 is designed to detect the current temperature T of the ultrasonic sensor 3. In other words, the temperature detection device 10 detects the respective sensor temperature. For this purpose, the temperature detection device 10 comprises a temperature sensor which is arranged in and/or on the housing 11 of the ultrasonic sensor 3 or in the immediate vicinity of the ultrasonic sensor 3. The storage device 9 and the temperature detection device 10 are connected to an interface 12 of the ultrasonic sensor 3. The resonance value fR stored in the storage device 9 and the temperature T currently detected by the temperature detection device 10 can be transmitted to the evaluation device 4 via the interface 12.

In the evaluation device 4 or in a memory unit of the evaluation device 4, at least one target value f _soll for the resonance frequency of the respective ultrasonic sensors 3 is usually stored. This target value f _soll for the resonance frequency can correspond to a standard value for the resonance frequency of the transmitting device of the ultrasonic sensor 3. Component tolerances resulting from manufacturing are not taken into account here. In particular, various target frequencies f _soll for the resonance frequency are stored as a function of the temperature T. This is shown in the graph according to 3 illustrated. The temperature T of the transmitting device 8 is plotted on the abscissa. The frequency f is plotted on the ordinate. The dashed line 13 describes the course of the target value f _{target of} the resonance frequency as a function of the temperature T. In comparison, the solid line describes the course of the measured resonance frequency of the transmitting device of an ultrasonic sensor 3 as a function of the temperature T. The measured resonance frequency is stored in the memory device 9 of the ultrasonic sensor 3 in the form of several resonance values fR, which were determined for different temperatures T.

In the present embodiment according to 3 It can be seen that, for example, at a temperature T of 30°C there is a significant difference between the target value f _target for the resonance frequency and the resonance frequency fR. Here it is provided that the resonance values fR are transmitted from the storage device 9 of the ultrasonic sensor 3 to the evaluation device 4. Within the evaluation device 4 the target values f _target for the resonance frequency stored there are replaced by the resonance values fR. In particular it is provided that each of the ultrasonic sensors 3 installed on the motor vehicle 1 sends its respective resonance values fR to the evaluation device 4 and the resonance values fR for each of the ultrasonic sensors 3 are stored in the evaluation device 4.

With further reference to 1 It will now be explained how the evaluation device 4 can be used to determine a blocked state of the respective ultrasonic sensors 3. The evaluation device 4 is also designed to control the actuating units of the respective ultrasonic sensors 3. First, the actuating unit is actuated with a corresponding excitation signal for a predetermined period of time. Subsequently, the mechanical oscillation of the actuating device 9 is recorded. In this way, the current resonance frequency or natural frequency of the transmitting device 8 can be determined. The frequency that arises when the transmitting device 9 oscillates corresponds to the current resonance frequency of the transmitting device 8.

To determine the blocked state, the evaluation device 4 first detects the current resonance frequency of the respective ultrasonic sensors 3. In this case, the current temperature T, which was determined using the temperature detection device 10, can also be transmitted from the respective ultrasonic sensor 3 to the evaluation device 4. Depending on a comparison based on the currently detected temperature T, the currently detected resonance frequency of the transmitting device 8 of the ultrasonic sensor 3 can be assigned to the reference value fR for this temperature T stored in the evaluation device 4. Based on a comparison between the currently measured resonance frequency and the resonance value fR, which is carried out by means of the evaluation device 4, it can be determined whether there is an additional mass on the ultrasonic sensor 3. This comparison can be carried out for each of the ultrasonic sensors 3 installed on the motor vehicle 1.

Because at least one resonance value fR is stored in the memory device 9 of the ultrasonic sensor 3, component tolerances can be eliminated as an influencing factor. In this way, a blocked state or ice and dirt detection can be set very selectively. Furthermore, a rapid query of the (fundamental) resonance frequency of the respective transmitting device 8 can be enabled by the evaluation device 4, for example, during initialization of the evaluation device 4. Thus, for example, averaging of all ultrasonic sensors 3 of the motor vehicle 1 is no longer necessary.

Claims (11)

Sensor arrangement (2) with at least one ultrasonic sensor (3) for a motor vehicle and an evaluation device (4), wherein the ultrasonic sensor (3) comprises a transmitting device (8) for transmitting ultrasonic waves, wherein the transmitting device (8) has a membrane and an actuating unit with which the membrane is movable for transmitting the ultrasonic waves, wherein the ultrasonic sensor (3) comprises a memory device (9) in which at least one operating parameter of the ultrasonic sensor (3) is stored, wherein as the at least one operating parameter of the ultrasonic sensor (3) at least one resonance value (fR) is stored in the memory device (9), which describes a resonance frequency of the transmitting device (8), wherein the evaluation device (4) is designed to receive the at least one resonance value (fR) stored in the memory device (9) from the ultrasonic sensor (3), characterized in that at least one desired value (f _soll ) for the resonance frequency of the transmitting device (8) of the ultrasonic sensor (3) is stored in the evaluation device (4), and the evaluation device (4) is designed to replace the at least one desired value (f _soll ) by the at least one received resonance value (fR). Sensor arrangement (2) according to Claim 1 , characterized in that a first resonance value (fR), which describes a first resonance frequency of the transmitting device (8) at a first temperature, and at least one second resonance value, which describes a second resonance frequency of the transmitting device (9) at a second temperature different from the first, are stored in the storage device (9). Sensor arrangement (2) according to Claim 1 or 2 , characterized in that the memory device (9) is designed as a non-volatile memory. Sensor arrangement (2) according to one of the preceding claims, characterized in that that the transmitting device (8) and the storage device (9) are arranged on a common carrier element and/or are arranged in a common housing (11). Sensor arrangement (2) according to one of the preceding claims, characterized in that the ultrasonic sensor (3) has a temperature detection device (10) for detecting a current temperature (T) of the ultrasonic sensor (3). Sensor arrangement (2) according to one of the preceding claims, characterized in that the ultrasonic sensor (3) has an interface (12) for outputting the at least one resonance value (fR) stored in the memory device (9). Sensor arrangement (2) according to claim one of the Claims 1 until 6 , characterized in that the evaluation device (4) is designed to control the transmitting device (8) of the ultrasonic sensor (3) as a function of the at least one received resonance value (fR). Sensor arrangement (2) according to one of the Claims 1 until 7 , characterized in that the evaluation device (4) is designed to control the transmitting device (8) of the ultrasonic sensor (3) to determine a current resonance frequency of the transmitting device (8). Sensor arrangement (2) according to Claim 8 , characterized in that the evaluation device (4) is designed to determine a blocked state of the ultrasonic sensor (3) based on a comparison of the currently determined resonance frequency and the at least one received resonance value (fR). Motor vehicle (1) with a sensor arrangement (2) according to one of the Claims 1 until 9 . Motor vehicle (1) according to Claim 10 , characterized in that the evaluation device (4) of the sensor arrangement (2) is designed to determine a blocked state of the ultrasonic sensor (3) when activating an ignition of the motor vehicle (1).

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