Method for operating a radar sensor in a motor vehicle and motor vehicle

Abstract

The invention relates to a method for operating a radar sensor (2, 7), in particular a long-range radar sensor (2, 7), in a motor vehicle (1), wherein the radar sensor (2, 7) has a detection range (5, 5') pointing to a front area or a rear space of the motor vehicle (1), the radar sensor (2, 7) is operated with a transmission power that determines the range of the radar sensor (2, 7), radar data of the radar sensor (2, 7), in particular within the radar sensor (2, 7) itself, are evaluated for detecting an object (6) in the detection range (5, 5'), wherein the transmission power of the radar sensor (2, 7) is increased from a first transmission power value to a second transmission power value when a switching criterion is met, the switching criterion indicating that the radar sensor (2, 7) has not detected an object (6), in particular one that meets a relevance criterion.

Description

Technical Field

[0001] The invention relates to a method for operating a radar sensor, in particular a long-range radar sensor, in a motor vehicle, wherein the radar sensor has a detection range pointing toward an area in front of or behind the motor vehicle, the radar sensor is operated with a transmission power that determines the range of the radar sensor, and radar data of the radar sensor are evaluated, in particular in the radar sensor itself, for detecting objects in the detection range. The invention also relates to a motor vehicle. Background Art

[0002] At present, the use of radar sensors in modern motor vehicles is widespread. Different types of radar sensors are known in this regard in order to detect the environment of the motor vehicle. Short-range radar (SRR) has a maximum measuring range of up to 30m, medium-range radar (MRR) has a maximum effective range of up to 150m, and long-range radar (LRR) has a maximum effective range of up to 250m. Long-range radar (LRR) is often used here to monitor the front area and rear space of the motor vehicle at a longer distance. The radar data received by the radar sensor of the motor vehicle is used by different vehicle functions of different vehicle systems, especially driver assistance systems. For example, it is known that the radar data of the long-range radar sensor is used in the vehicle functions of the longitudinal guidance adaptive cruise control system (ACC system), overtaking assistance, lane change assistance, and is also used for safety systems, such as avoidance systems. In addition, the radar data from the long-range radar sensor is also usually used when the motor vehicle is at least partially, especially completely, automatically guided.

[0003] Modern radar sensors installed in motor vehicles for environmental monitoring usually use semiconductor technology at least partially, wherein a transmitting chip, in particular a so-called MMIC, is usually used as a transmitting unit to transmit radar signals. Depending on the transmission power used, such a transmitting chip can heat up.

[0004] In this regard, it is known in the prior art to operate radar sensors in motor vehicles at a constant transmission power in order to prevent the transmitting chip, in particular the MMIC, from being thermally damaged or destroyed. In this case, the transmission power is adjusted to a transmission power value such that under all temperature conditions, for example in the range of -40°C to +80°C, the thermal load is harmless to the transmitting chip and generally exhibits a margin / potential. This results in a reduction of the transmission power actually used compared to the transmission power that is possible in principle, in order to enable the radar sensor to achieve a permanent function under thermal framework conditions. For example, long range radar sensors (LRR) are nowadays usually adjusted to a transmission power of 10 dBm, although the transmitting chip may emit a transmission power of 13 dBm (20 mW) or modern transmitting chips may even emit a transmission power of 14 dBm (30 mW).

[0005] However, due to the reduction in the transmission power when the radar sensor is in continuous operation, the maximum effective range of the radar sensor that can detect objects will also be reduced. This is also accompanied by a reduction in the probability of identifying small objects, such as motorcycles. However, it should be noted here that as the supervision of object recognition continues to increase, radar sensors with medium effective range (MRR) and long effective range (LRR) must meet the emerging requirements. Therefore, for example, it can be stipulated that motorcycle drivers within a distance of 55m must be identified in any case (for example, see the current version of the steering standard ECT79 at the time of this application).

[0006] DE 10 2004 017 720 A1 proposes that, in order to detect objects in the vehicle environment in a radar sensor system, the transmission power of the radar signal is adaptively controlled as a function of the actual distance to the nearest object, taking into account the functional parameters predefined for the desired radar function. It can be provided that the closer the object, the lower the transmission power, in order to avoid crosstalk. Such an overcontrol is desirable in particular when measurements are to be made at close ranges, for example at distances of only a few meters, so that the teaching of this document relates in particular to short-range radars (SRR), in particular also to so-called near field radars (NFR-Near Field Radar), which are intended to measure at ranges of up to one meter or less.

[0007] DE 10 2007 046 648 A1 relates to a radar sensor for detecting the traffic environment in a motor vehicle. The radar sensor has an adjustable transmitting and / or receiving amplifier and a control device for adjusting the transmitting and / or receiving gain, wherein the traffic environment is continuously evaluated by an evaluation device and the control device is influenced depending on the current evaluation in order to reduce the number of interfering radar echoes from irrelevant objects, especially in city traffic. For this purpose, complex beamforming methods and complex modifications of antenna components are described.

[0008] DE 103 47 214 A1 relates to a radar system with at least one detector for special weather conditions. Depending on the special weather conditions detected by the at least one detector, the transmission power of the radar system is controlled, wherein, for example, in the case of low visibility, a power boost is to be performed. However, this will amplify so-called clutter, for example caused by raindrops and / or snowflakes. Summary of the invention

[0009] It is therefore an object of the present invention to enable a radar sensor to detect an object as early as possible in the simplest possible manner, in particular while maintaining continuous operation.

[0010] To achieve this object, according to the invention, in a method of the type mentioned at the outset, the transmit power of the radar sensor is increased from a first transmit power value to a second transmit power value when a switching criterion is met, which indicates that the radar sensor has not detected an object that particularly meets a relevance criterion.

[0011] The invention is based on the finding that, when investigating a typical journey of a motor vehicle, which has a front or rear radar sensor with a long range, in which at least one relevant object is present in the detection range of the radar sensor most of the time, the absence of (relevant) objects in the detection range can be detected to a lesser extent. It is therefore proposed that, when no objects, in particular no relevant objects, are detected in the detection range, the transmit power of the radar sensor is increased in order to increase the detection range and thus also to be able to identify smaller objects, such as motorcycle drivers, at an earlier stage. It is therefore proposed according to the invention to focus on dynamic transmit power regulation instead of regulating the transmit power to an average continuous power.

[0012] Due to conservative power regulation for thermal protection of the transmitting unit of the radar sensor, in particular the transmitting chip, the transmitting power is reduced and thus the effective range and the detection capability of smaller objects are reduced. Now it is usually the case that high transmitting power is not required anyway, because the objects are close enough to be detected with low transmitting power. The present invention now makes it possible to increase the transmitting power of the radar sensor on roads with less traffic and in areas with a small number of (relevant) objects, in order to obtain early detection when (relevant) objects do appear.

[0013] If an object suddenly appears again, in particular a relevant object that meets the relevance criterion, the transmission power can be reduced accordingly again. Therefore, within the scope of the present invention, it can be said in general that the transmission power is reduced again from the second transmission power value to the first transmission power value when the reduction criterion is met, wherein at least one first reduction criterion of at least one reduction criterion checks whether an object that meets the relevance criterion is detected by the radar sensor. However, at the same time, temperature monitoring can also be carried out expediently, for example by means of a temperature sensor on or in the radar sensor. Therefore, a suitable improvement of the present invention provides that at least one second reduction criterion of at least one reduction criterion checks whether the temperature of the radar sensor, in particular the transmitting unit of the radar sensor, exceeds a first threshold value and / or whether a thermal margin value that is temperature-dependent or time-dependent on the measured temperature is below a second threshold value.

[0014] Therefore, if no (relevant) object is detected and there is sufficient thermal margin, the transmit power can be increased to a second transmit power value, which can in particular correspond to the maximum effective power of the transmit chip as a transmit unit, until an object is detected or a maximum temperature is reached (first threshold) or the thermal margin is deemed to be too low (second threshold).

[0015] In this context, a particularly advantageous embodiment of the invention provides that, when a first reduction criterion is met, the transmission power is reduced from a second transmission power value to a first transmission power value continuously or stepwise, in particular as a function of the distance and / or the relative speed of the detected object, in such a way that the object continues to be detected by the radar sensor despite the reduction in the transmission power. In other words, when a (relevant) object is identified, the transmission power can be reduced again stepwise, wherein this is done in a particularly advantageous manner such that the resulting effective range is equal to the distance or is greater than the distance by a tolerance value. In other words, this ensures that the object continues to be identified and can therefore be tracked (so-called "tracking"). At the same time, however, the thermal load on the transmitting unit, in particular the transmitting chip, is reduced again.

[0016] At this point it should also be generally pointed out that the evaluated radar data used only for evaluating the switching criterion can also advantageously be provided by a tracking algorithm (tracking algorithm) in the radar sensor, i.e. in particular by a tracking unit of a control device of the radar sensor. For example, the tracking unit implementing the tracking algorithm can provide information whether a (relevant) object is just being tracked. In the second case, the starting point is that there is currently no (relevant) detected object. Nowadays, such tracking algorithms are usually implemented in the radar sensor itself, which can also apply to the dynamic transmission power control described here, for which purpose the control device of the radar sensor can have a corresponding transmission power unit or a corresponding transmission power algorithm.

[0017] At this point, it should be emphasized again that the invention provides a particularly easy to implement variant of dynamic transmission power control, which can be implemented with existing means (temperature sensor, tracking algorithm) and, for example, can be implemented by a small control loop in the transmission power algorithm with only a few lines of code. In other words, the required information, such as whether the tracking algorithm is tracking the relevant object and whether the temperature sensor, which is specifically assigned to the radar sensor or arranged in the radar sensor, is already available in terms of thermal load and only needs to be queried in order to implement the transmission power control in a simple manner without complex beamforming control methods and antenna directional characteristic control methods. Despite this easy implementability, early recognition of (relevant) objects is possible, after which, when no (relevant) object is recognized, the transmission power is increased even briefly, so that better recognition is achieved and thus safety in road traffic is improved. In other words, in a simple control loop, an improvement in early object recognition can be achieved by a dynamic design of the interaction of the transmission power with the recognition of the (relevant) object and the temperature information.

[0018] In this context, it should also be pointed out that the thermal load of the transmitting unit, in particular the transmitting chip, in the radar sensor has been previously adjusted to a maximum ambient temperature of 80° C. to 85° C. in conjunction with a continuous transmitting power. However, 80° C. is only reached in the rarest cases, since even in the desert, temperatures of 50° C. or higher usually occur only briefly. A large part of the earth's surface lies in the moderate temperature range, wherein the temperature for a long period of the year is also far from the limit of 30° C. Therefore, it has proven feasible to briefly increase the transmitting power until the (relevant) object reappears in the detection range of the radar sensor.

[0019] Here, the evaluation of the switching criterion and at least one reduction criterion preferably involves relevant objects, wherein in particular it can be provided that the relevance criterion is selected in such a way that the objects classified as follows meet the relevance criterion: the objects should be considered by the function using the radar data of the radar sensor. Here, the classification of objects from the radar data is already known to a large extent in the prior art, so as to keep the number of objects actually to be evaluated by the vehicle function as small as possible and, for example, to exclude edge road structure objects or the like as largely as possible. Accordingly, the objects can be subordinately classified into a relevance class. For example, such a relevance class can contain dynamic objects, i.e. other road participants. The vehicle functions using the radar data of the radar sensor can, for example, include ACC functions, overtaking assistance functions, lane change assistance functions, safety functions (such as avoidance assistance functions) and functions for at least partially automatically guiding the motor vehicle. Here, the relevance criterion can also take into account whether the corresponding vehicle function is currently activated.

[0020] Preferably, the second transmission power value is increased by 20% to 50%, in particular by 30%, relative to the first transmission power value, and / or the effective range given by the second transmission power value is increased by 30%-70%, in particular by 50%, relative to the effective range given by the first transmission power value. For example, increasing the transmission power from a continuous power of 10 dBm to a short-term power of 13 dBm can already ensure a 50% increase in the effective range and thus ensure an earlier detection of the (relevant) object. It should be pointed out here that legal regulations, such as in Germany, which stipulate a maximum effective isotropic power output of 55 dBm, are generally not a problem, although these legal regulations specify the addition of the transmission power in dBm and the antenna gain in dBi. In long-range radar sensors, the transmission power is typically in the range of 10 dBm to 14 dBm, while the antenna gain is typically in the range of 15 dBi to 21 dBi, so that even when using the second transmission power value of the maximum possible transmission power, operation is carried out far from these limits.

[0021] As already explained, a radar sensor having a transmitting unit designed as a transmitting chip, in particular an MMIC, is preferably used as the radar sensor. It can be particularly advantageous here to provide for a temperature sensor integrated in the transmitting chip to measure the temperature of the radar sensor, in particular the temperature of the transmitting chip. Although within the scope of the invention it is in principle possible to use temperature measured values ​​of the external temperature and / or the ambient temperature for temperature monitoring, according to the invention it is preferred to use a temperature sensor close to the transmitting chip or preferably integrated therein, in order to be able to monitor the thermal load of the transmitting chip as realistically as possible.

[0022] In addition to the method, the invention also relates to a motor vehicle having a radar sensor, in particular a long-range radar sensor, wherein the radar sensor has a detection range directed toward the area in front of or behind the motor vehicle, the radar sensor is operated with a transmission power that determines the range of the radar sensor, and the radar sensor also has a control device that is designed to carry out the method according to the invention. All configurations and explanations related to the method according to the invention apply analogously to the motor vehicle according to the invention, so that the advantages already mentioned can also be achieved with this motor vehicle.

[0023] In particular, the control device can have, for example, a transmitting power unit for carrying out the method according to the invention, which can, for example, receive data from a tracking unit of the control device, such as directly from a temperature sensor and / or from a temperature monitoring unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further advantages and details of the present invention will be apparent from the following description of the embodiments and with reference to the accompanying drawings. The drawings show:

[0025] Figure 1 A flow chart showing an embodiment of a method according to the present invention;

[0026] Figure 2 showing a first driving situation;

[0027] Figure 3 showing a second driving situation;

[0028] Figure 4 shows a motor vehicle according to the invention; and

[0029] Figure 5 The functional structure of a radar sensor is shown. DETAILED DESCRIPTION

[0030] Figure 1 A flow chart of an exemplary embodiment of a method according to the invention for operating a long-range radar sensor (LRR) in a motor vehicle is shown. The radar sensor is directed towards the area in front of the motor vehicle or the space behind it. Since at least one vehicle function of the motor vehicle is active for a relatively long period of time, a permanent operation of the radar sensor is required in order to provide radar data for the vehicle function. The radar sensor itself is already designed for a first evaluation of the radar data in that the detected objects are classified, in particular based on a relevance criterion for filtering out objects that are not relevant for at least one vehicle function, and are tracked by a tracking algorithm in a tracking unit, wherein the tracking (tracking) is limited to relevant objects. Relevant objects may include, for example, other traffic participants and / or obstacles on the roadway.

[0031] In normal operation of the radar sensor, step S1, the radar sensor is operated with a transmission power according to a first transmission power value. The normal operation of the radar sensor here relates to situations which occur significantly more frequently according to basic knowledge, in which at least one relevant object is detected and tracked. The first transmission power value is selected in this case such that an overheating of a transmission chip, here an MMIC, used as a transmission unit in the radar sensor is prevented. The first transmission power value results in a specific first effective range and a specific detection capability for smaller objects, such as motorcycle drivers.

[0032] In step S2, it is checked whether the switching criterion is met. At present, when no relevant object is detected, that is, when no relevant object is tracked in the tracking unit, the switching criterion is met. If the switching criterion is not met, step S1 is continued to be performed using the first transmission power value, and when the switching criterion is met, it branches to step S3, in which the transmission power is increased to a second transmission power value that is higher than the first transmission power value. In one example, the transmission power can be increased to the maximum effective power of the transmitting chip, for example. With the increase from 10 dBm as the first transmission power value to 13 dBm as the second transmission power value, a second effective range that is increased by 50% compared to the first effective range can be achieved. The transmission power increased in this way not only increases the effective range, but also correspondingly increases the detection capability of smaller objects, so that the relevant objects can be detected earlier overall. In other words, when there is no relevant object in the detection area, increasing the transmission power in a way that can be easily confirmed and implemented will ensure the earliest possible recognition of the newly appearing relevant object.

[0033] In step S4, a second reduction criterion is checked, by means of which it is to be determined whether overheating of the transmit chip is imminent, for example when the second transmit power value takes longer than expected or the like. For this purpose, it can be checked whether the temperature measurement value of the temperature sensor exceeds a first threshold value and / or whether the thermal margin is below a second threshold value if a thermal balance is introduced. If the second reduction criterion is met, the transmit power is at least temporarily reduced again to the first transmit power value, step S1.

[0034] Otherwise, in step S5, a first reduction criterion is checked, which monitors whether a new relevant object is detected earlier by the radar sensor due to the increased transmission power. If this is not the case, step S3 is continued, but if this is the case, a branch is made to step S6. In step S6, the transmission power is reduced stepwise (or alternatively also continuously) starting from the second transmission power value to the first transmission power value, wherein when the first transmission power value is reached, step S1 is continued again. The stepwise (or alternatively also continuous) reduction, which depends on the distance and / or the relative speed of the detected object, ensures that the object can also continue to be detected and can therefore be tracked. In other words, the transmission power is selected in such a way that the effective range allows the object to continue to be detected.

[0035] Figure 2 and Figure 3 This is explained in more detail based on two traffic situations. Figure 2A motor vehicle 1 according to the invention with a long-range front radar sensor 2 is shown on a road 3. Another road user is approaching and is within the detection range 5 of the radar sensor 2. The radar sensor is operated with a transmission power according to a first transmission power value, which results in a relatively short range. However, in Figure 3 In the case of , there are no further road users 4 and therefore no relevant objects, so that the transmission power according to the second transmission power value is used and the detection area 5 ′ is provided with a significantly increased effective range of, for example, 50%. Figure 3 The new relevant object 6 indicated by way of example in can be detected at an early stage.

[0036] Figure 4 The schematic diagram of the principle of a motor vehicle 1 according to the invention is shown which, in addition to the long-range front radar sensor 2 already described, currently also comprises a long-range or medium-range rear radar sensor 7 which can forward its pre-evaluated radar data, i.e. data relating in particular to tracking relevant objects, to various vehicle systems 8 which implement vehicle functions that utilize the radar data.

[0037] The functional structure of the radar sensors 2 and 7 is as follows: Figure 5 . Therefore, the radar sensor 2, 7 has, in addition to the antenna assembly 9, a control device 13, to which a transmitting unit 11 and a receiving unit 12, which are constructed as a transmitting chip 10, are assigned, and the control device is designed to carry out the method according to the invention. A temperature sensor 14 is also integrated in the transmitting chip 10, in the present case an MMIC, which supplies its temperature measurement values ​​to the control device 13. In addition to the functional units known in principle, the control device 13 currently comprises a tracking unit 15 in each case, in which a tracking algorithm (tracking algorithm) is implemented, as is known in principle. The tracking unit 15 can also classify objects as relevant or irrelevant, however, this can also be done by a classification unit. The information about whether a relevant object 6 is detected, as well as the temperature measurement values ​​of the temperature sensor 14, are forwarded to a transmitting power unit 16 which is specifically used to carry out the method according to the invention.

Claims

1. A method for operating a long-range radar sensor (2, 7) in a motor vehicle (1), wherein: The radar sensor (2, 7) has a detection area (5, 5') pointing toward the area in front of or behind the motor vehicle (1), the radar sensor (2, 7) is operated with a transmission power that determines the effective range of the radar sensor (2, 7), radar data of the radar sensor (2, 7) are evaluated for detecting an object (6) in the detection area (5, 5'), It is characterized in that increasing the transmission power of the radar sensor (2, 7) from a first transmission power value to a second transmission power value when a switching criterion is met, the switching criterion indicating that the radar sensor (2, 7) has not detected an object (6) that meets the relevance criterion, A relevance criterion is selected in such a way that an object (6) classified as such that it is to be taken into account by a function using radar data of a radar sensor (2, 7) meets the relevance criterion.

2. The method according to claim 1, characterized in that Radar data from the radar sensor (2, 7) are evaluated in the radar sensor (2, 7) itself.

3. The method according to claim 1 or 2, It is characterized in that When at least one reduction criterion is met, the transmit power is reduced from the second transmit power value back to the first transmit power value.

4. The method according to claim 3, It is characterized in that At least one first of the at least one reduction criterion checks whether an object (6) meeting the relevance criterion is detected by the radar sensor (2, 7), and / or At least one second of the at least one reduction criterion checks whether the temperature of the radar sensor (2, 7) exceeds a first threshold value and / or whether a thermal margin value based on the temperature or correlated in time with the measured temperature is below a second threshold value.

5. The method according to claim 4, characterized in that The temperature of the radar sensor (2, 7) is the temperature of the transmitting unit (11) of the radar sensor (2, 7).

6. The method according to claim 4, It is characterized in that When a first reduction criterion is met, the transmission power is reduced continuously or stepwise from the second transmission power value to the first transmission power value in such a way that the object (6) continues to be detected by the radar sensor (2, 7) despite the reduced transmission power.

7. The method according to claim 6, characterized in that The transmission power is reduced as a function of the distance and / or the relative speed of the detected object (6).

8. The method according to claim 7, It is characterized in that The transmission power is reduced until it reaches the first transmission power value, so that the resulting effective range is equal to the distance or is greater than the distance by a tolerance value.

9. The method according to claim 1 or 2, It is characterized in that The second transmit power value is increased by 20% to 50% relative to the first transmit power value, and / or the effective range provided by the second transmit power value is increased by 30% to 70% relative to the effective range provided by the first transmit power value.

10. The method according to claim 9, characterized in that The second transmit power value is increased by 30% relative to the first transmit power value.

11. The method according to claim 9, characterized in that The effective range provided by the second transmit power value is increased by 50% relative to the effective range provided by the first transmit power value.

12. The method according to claim 1 or 2, It is characterized in that A radar sensor (2, 7) having a transmitting unit (11) designed as a transmitting chip (10) is used as the radar sensor (2, 7).

13. The method according to claim 12, characterized in that The transmitting chip is a MMIC.

14. The method according to claim 12, It is characterized in that A temperature sensor (14) integrated in a transmitting chip (10) is used to measure the temperature of a radar sensor (2, 7).

15. A motor vehicle (1) comprising a long-range radar sensor (2, 7), wherein: The radar sensor (2, 7) has a detection range (5, 5') pointing toward the area in front of or behind the motor vehicle (1), the radar sensor is operated with a transmission power that determines the effective range of the radar sensor (2, 7), and the radar sensor also has a control device (13) which is designed to carry out the method according to any one of claims 1 to 14.

Images