ENVIRONMENTAL SURVEILLANCE RADAR DEVICE

Abstract

Environmental monitoring radar device (20a, 20b) mounted on a vehicle and repeatedly transmitting and receiving radar waves to monitor a target in the vicinity of the vehicle, the device comprising: a signal generation unit (21) designed to generate a frequency difference signal indicating a frequency difference between a transmitted signal and a received signal; a spectrum generation unit (21) designed to perform a frequency analysis of the frequency difference signal generated by the signal generation unit in order to produce a frequency spectrum accordingly; a cycle setting unit (21) designed to set an update cycle for updating a determination reference, the determination reference being used to determine whether radio wave interference has occurred; a learning unit (21, S30, S40, S90) designed to learn the reference for determining the reference in order to calculate a learning value of the reference for determining the reference during a preset learning period, wherein the learning period is a period until an update time for the reference, which is determined by the update cycle set by the cycle setting unit; and an update unit (21, S60) designed to update a value of the determination reference to the learning value of the determination reference calculated by the learning unit at the update time, wherein the learning unit is designed to set the learning value to an initial value at the start of the learning period; to compare the learning value with a value of background noise of the frequency spectrum generated by the spectrum generation unit during the learning period; and to update the learning value to the value of the background noise if the value of the background noise is smaller than the learning value.

Description

Cross-reference to the relevant registration

[0001] The present application claims priority over Japanese patent application No. 2017-077485, which was filed on April 10, 2017, and the contents of which are hereby incorporated by reference. Technical field

[0002] The present invention relates to a radar device that monitors the surroundings of a vehicle. State of the art

[0003] A radar system mounted on a vehicle detecting a target in the vehicle's vicinity, such as another vehicle and a stationary object, can cause radio wave interference with a radar system mounted on a different vehicle. If these radar systems use a frequency analysis function or waveform for a beat signal to extract different pieces of information, as is the case with FMCW and multi-frequency CW radars, background noise in the frequency analysis function increases when these radar systems are subjected to radio wave interference. This background noise masks the peak in the frequency analysis function based on a wave reflected from the target, making it difficult to detect the target using the frequency analysis function.

[0004] These radar devices must therefore eliminate interference when radio wave interference occurs. To perform the interference removal process, the radar devices must accurately detect the occurrence of radio wave interference. Patent reference 1 below discloses a technique for comparing a noise level with a threshold value, which is a fixed value, and for detecting the occurrence of radio wave interference when the noise level is equal to or greater than the threshold value. Citation list of patent literature

[0005] PTL 1: JP 2008 - 232 833 A Summary of the invention

[0006] The background noise of a frequency spectrum can fluctuate depending on the condition and environment of a radar device. Background noise tends to fluctuate when the condition and environment of the radar device change, especially when the radar device is mounted on a vehicle. After detailed investigation, the inventors found the problem that the radar device might falsely detect the occurrence of radio wave interference in a situation where the background noise is relatively high when the threshold is fixed.After further detailed investigations, the inventors also found the problem that part of the peak, which is based on a wave reflected from a target, is removed from the frequency analysis function when the radar device mistakenly detects the occurrence of radio wave interference and takes a corresponding countermeasure, resulting in poorer target detection accuracy.

[0007] The present invention preferably provides a technique for accurately detecting radio wave interference.

[0008] One aspect of the present invention relates to vehicle-integrated environmental monitoring radar devices (20a, 20b) that repeatedly transmit and receive a radar wave to monitor a target in the vicinity of a vehicle. The environmental monitoring radar devices (20a, 20b) comprise a signal generation unit (21), a spectrum generation unit (21), a cycle setting unit (21), a learning unit (21, S30, S40, S90), and an update unit (21, S60). The signal generation unit generates a frequency difference signal that indicates a frequency difference between a transmitted signal and a received signal. The spectrum generation unit performs a frequency analysis of the frequency difference signal generated by the signal generation unit in order to produce a corresponding frequency spectrum.The cycle setting unit sets an update cycle to update a reference datum, which is used to determine whether radio wave interference has occurred. The learning unit learns the reference datum to calculate a learning value for it during a preset learning period. The learning period is the time until an update time for the reference datum, determined by the updated cycle set by the cycle setting unit. At the update time, the update unit updates a value of the reference datum to the learning value calculated by the learning unit.The learning unit is designed to set the learning value to an initial value at a start time of the learning period, to compare the learning value with a value of background noise of the frequency spectrum generated by the spectrum generation unit during the learning period, and to update the learning value to the value of the background noise if the value of the background noise is less than the learning value.

[0009] According to one aspect of the present invention, the lowest background noise value during the learning period is calculated as the learning value of the reference reference up to the update time. The reference reference is then updated to the calculated learning value at the update time. Even if the background noise fluctuates, a reference reference can thus be set according to the fluctuation of the background noise. This, in turn, makes it possible to accurately detect radio wave interference.

[0010] Note that the reference numerals in parentheses in the claims indicate how each element specified by these reference numerals corresponds to the specific arrangement described as a mode in the embodiments described below, but do not limit the technical scope of the present invention. Brief description of the drawings Fig. Figure 1 is a block diagram of a configuration of a vehicle-integrated system 100 according to the present embodiment. Fig. Figure 2 is a graph showing a time function of a beat signal in the absence of radio wave interference. Fig. Figure 3 is a graph showing a spectrum function of a beat signal in the absence of radio wave interference. Fig. Figure 4 is a graph showing a time function of a beat signal in the presence of radio wave interference. Fig. Figure 5 is a graph showing a spectrum function of a beat signal in the presence of radio wave interference. Fig. Figure 6 is a diagram showing periods for calculating a value of a reference and times for updating the reference. Fig. Figure 7 is a graph showing an initial value of a reference value, the background noise of the current processing cycle, and the lowest background noise of the previous processing cycle. Fig. Figure 8 is a flowchart that represents a processing routine for updating the determination reference. Description of the embodiments

[0011] An exemplary embodiment for carrying out the present invention is described below with reference to the drawings. 1. Configuration

[0012] A vehicle-integrated system 100 according to the present embodiment is referred to below with reference to Fig. 1 described. The vehicle-integrated system 100 includes a radar system 10, a driver assistance ECU 30, an alarm device 40, and another control ECU group 50. The vehicle-integrated system 100 is assumed to be a system mounted on a vehicle.

[0013] The radar system 10 includes radar devices 20a and 20b. Radar device 20a is a right rear radar device installed on the right side of the rear of the vehicle. Radar device 20b is a left rear radar device installed on the left side of the rear of the vehicle. Fundamentally, radar devices 20a and 20b are identical in design and function. In the following description, radar devices 20a and 20b are collectively referred to as radar device 20 or radar devices 20. The radar system 10 can include at least one radar device 20. In other words, the radar system 10 can include only one radar device 20 or three or more radar devices 20. In the present embodiment, radar device 20 corresponds to an environmental monitoring radar device.

[0014] The radar device 20 is a millimeter-wave radar that repeatedly transmits and receives a radar wave to monitor the surroundings of a vehicle. The radar device 20 can use any modulation system, for example, an FMCW system or a dual-frequency CW system. The radar device 20 includes a signal processing unit 21, a transmitting antenna unit 22, and a receiving antenna unit 23.

[0015] The signal processing unit 21 generates a transmit signal and sends a transmit wave, which is a radar wave, from the transmit antenna unit 22 based on the generated transmit signal. The receive antenna unit 23 receives a transmit wave (i.e., a reflected wave) that is reflected by a target. The signal processing unit 21 generates a receive signal from the reflected wave, which is received by the receive antenna unit 23 to generate a beat signal. The beat signal is a frequency difference signal whose frequency is a frequency difference between the transmit signal and the receive signal.

[0016] Furthermore, the signal processing unit 21 performs frequency analysis processing, such as an FFT, on the generated beat signal to produce a frequency spectrum and extracts one or more peaks as corresponding targets from this spectrum. If there is no radio wave interference, only a low noise level is superimposed on the frequency spectrum function or waveform of the beat signal, meaning that the background noise level in the frequency spectrum function of the beat signal is low, as shown in the Fig. 2 and Fig. Figure 3 shows this. This enables the signal processing unit 21 to successfully extract the target from the frequency spectrum.

[0017] However, if radio wave interference has occurred, the time function of the beat signal has a higher level of background noise superimposed on it than in the case where no radio wave interference occurs, which increases the background noise level of the frequency spectrum function, as shown in the Fig. 4 and Fig. Figure 5 shows that if radio wave interference has occurred, one or more peaks, each indicating a target, may be buried in the background noise, making it impossible for the signal processing unit 21 to extract one or more targets from the frequency spectrum.

[0018] In this regard, the signal processing unit 21 determines whether radio wave interference has occurred. If radio wave interference is determined to have occurred, the signal processing unit 21 performs an anti-interference measure and then extracts one or more peaks from the frequency spectrum. Examples of such an anti-interference measure include applying a median filter to the beat signal.

[0019] The signal processing unit 21 then generates target information based on the frequency spectrum and outputs the generated target information to the driver assistance ECU 30. Examples of target information include the distance from the vehicle to the target, the target's relative speed with respect to the vehicle, and the target's orientation with respect to the vehicle. In the present embodiment, the signal processing unit 21 performs the functions of a signal generation unit, a spectrum generation unit, a cycle setting unit, a learning unit, and an update unit.

[0020] The driving assistance ECU 30 receives target information from the respective radar device 20 of a target detected by that radar device 20 and sends and receives data to and from the control ECU group 50 via a network 35. The driving assistance ECU 30 issues an alarm output command to the alarm device 40 if a target is present in the vicinity of the vehicle that could potentially collide with the vehicle.

[0021] The alarm device 40 includes, for example, an indicator or display mounted on a door mirror or located inside a vehicle cabin, a vehicle-integrated loudspeaker, and / or a vehicle-integrated display. In response to the alarm output command issued by the driver assistance ECU 30, the alarm device 40 emits a warning tone or voice message, or displays a warning.

[0022] The control ECU group 50 contains several ECUs that are mounted on a different vehicle than the driver assistance ECU 30 and are connected to the network 35. 2. Reference to purpose

[0023] The following describes a reference point used by the signal processing unit 21 to determine whether radio wave interference has occurred. The signal processing unit 21 compares the background noise of a frequency spectrum with a threshold value and determines that radio wave interference has occurred if the background noise exceeds the threshold value. The threshold value is a value provided by adding a constant offset value to a reference value calculated based on the background noise of the frequency spectrum. In the present embodiment, a power minimum value in the frequency spectrum is used as the background noise.

[0024] The background noise fluctuates depending on the condition and / or environment of the radar device 20. For example, a higher temperature of the radar device 20 increases the background noise. The background noise also increases if the radar device 20 deteriorates over time. The background noise decreases when the vehicle moves from an urban street to a highway or from a city center to a remote area. This means that the signal processing unit 21 could erroneously detect the occurrence of radio wave interference if the reference point or the threshold is fixed.

[0025] To avoid such erroneous detection, the signal processing unit 21 learns a value of the determination reference during a fixed learning period Ts and updates the determination reference to the learned value every preset update cycle Tu.

[0026] In particular, at a time Ta1, a predetermined initial value for the reference point is set when the vehicle's ignition is switched on, as described in Fig. Figure 6 is shown. The signal processing unit 21 then starts learning the reference point and continues learning it during the learning period Ts. The initial value is used as the reference point value for the initial learning period Ts after the ignition is switched on.

[0027] A time point Tb1, which is the point at which the initial learning period Ts ends, serves as a point for updating the initial value of the reference. At time Tb1, the reference is updated from its initial value to a learned value NF1 calculated during the learning period Ts. The value NF1 of the reference updated at time Tb1 continues to be used until the update cycle Tu has elapsed since time Tb1.

[0028] A time point Tb2, which is a time point at which the update cycle Tu has elapsed since time Tb1, serves as a time point for updating the subsequent determination reference. The period from time Ta2, which is earlier than time Tb2, until time Tb2 is a second learning period Ts.

[0029] In other words, the update cycle Tu is longer than the learning period Ts, and the learning period Ts is set to a period from time Ta2 until the time to update the determination reference.

[0030] At time Ta2, the signal processing unit 21 sets a new initial value for the reference and starts learning a value of the reference. At time Tb2, the reference is updated from the value NF1 to a learned value NF2, which was calculated during the second learning period Ts.

[0031] The value NF2 of the determination reference, updated at time Tb2, continues to be used until the update cycle Tu has elapsed since time Tb2. Signal processing unit 21 then repeats the learning and updating of the determination reference in a similar manner.

[0032] As it is in Fig. As shown in Figure 7, the initial value of the reference datum should be set to a value that is higher than a standard background noise generated when there is no radio wave interference, and lower than a standard background noise generated when radio wave interference has occurred.

[0033] Furthermore, the signal processing unit 21 can set the value of the update cycle Tu. For example, the signal processing unit 21 can set the update cycle Tu to a specific period. Additionally, the signal processing unit 21 can change the update cycle Tu when the state of the radar devices 20 changes. The state of the radar device 20 can include the temperature of the radar device 20 and / or the deterioration state of the radar device 20.

[0034] In particular, the signal processing unit 21 can set the update cycle Tu to (1) a relatively shorter value in response to the fact that the state of the radar device 20 has changed relatively significantly, or (2) a relatively longer value while the state of the radar device 20 remains stable.

[0035] This makes it possible to quickly change the value of the reference point in response to a dramatic change in the background noise.

[0036] Furthermore, the signal processing unit 21 can modify the update cycle Tu when the vehicle's environment changes. The vehicle's environment includes an attribute of the road the vehicle is traveling on, such as a general road or a highway; a property of the area the vehicle is traveling in, such as an urban area or a wasteland; and a weather property, such as temperature, rain, and fair weather.

[0037] In particular, the signal processing unit 21 can set the update cycle Tu to (1) a relatively shorter value in response to the fact that the vehicle's environment has changed relatively significantly, or (2) a relatively longer value if the environment of the vehicle remains stable.

[0038] The signal processing unit 21 can obtain information about the vehicle's surroundings from the target information acquired by the radar device 20. The signal processing unit 21 can also obtain information about the vehicle's surroundings from a navigation device 60 if the vehicle is equipped with the navigation device 60, as indicated by a dashed line in Fig. 1 is specified. The navigation device 60, which has a storage device that stores map data, retrieves the current position of the vehicle and locates the position on the map. In addition, the signal processing unit 21 can change the update cycle Tu if the state of the radar device 20 as well as the vehicle's environment changes. 3. Processing

[0039] The following describes a processing routine for updating the determination threshold, which is performed by signal processing unit 21, with reference to the flowchart of the Fig. As described in section 8, the signal processing unit 21 executes a cycle of the processing routine each time it generates a frequency spectrum of a peak signal. The signal processing unit 21 has a preset value for the update cycle Tu for the determination reference.

[0040] First, in step S10, the signal processing unit 21 determines whether the time of the current cycle of the processing routine lies within the learning period Ts of the determination reference.

[0041] In particular, the signal processing unit 21 uses a counter value to determine whether the current processing cycle time is within the learning period Ts, as described later. The processing routine advances to S20 if it is determined that the current processing cycle time is within the learning period Ts. Conversely, if the current processing cycle time is not within the learning period Ts, the processing routine advances to S50.

[0042] Subsequently, in step S20, the signal processing unit 21 determines whether a measure against radio wave interference has been implemented. Implementing the measure against radio wave interference can reduce background noise, depending on the conditions of the radio wave interference. However, calculating a reference value from the background noise used in the measure against radio wave interference can result in a reference value that is lower than a suitable value. This can lead to a lower threshold value, resulting in an inaccurate detection of the radio wave interference.

[0043] For this reason, the signal processing unit 21 avoids learning the determination reference, and the processing routine proceeds to step S80 if step S20 determines that a measure against radio wave interference has been taken. In step S80, the signal processing unit 21 increments the counter value by 1 and then terminates the current cycle of the processing routine. Conversely, the processing routine proceeds to step S30 if step S20 determines that a measure against radio wave interference has not been taken.

[0044] In step S30, the signal processing unit 21 determines whether a value of the background noise in the current cycle of the processing routine is smaller than a learned value of the determination reference of the current time.

[0045] If, in step S30, it is determined that the value of the background noise is equal to or greater than the learned value in the current cycle of the processing routine, the processing routine proceeds to step S80. In step S80, the signal processing unit 21 increments the counter value by 1 and then terminates the current cycle of the processing routine.

[0046] On the other hand, if in step S30 it is determined that the value of the background noise in the current cycle of the processing routine is smaller than the learned value, the processing routine proceeds to step S40.

[0047] In step S40, the signal processing unit 21 updates the learned value to the value of the background noise in the current cycle of the processing routine, and then the processing routine proceeds to step S80. In step S80, the signal processing unit 21 increments the value of the counter by 1 and then terminates the current cycle of the processing routine.

[0048] This results in the learning value being set to the lowest value of the background noise during the learning period Ts. As described in Fig. As shown in Figure 7, the learning value is not updated during the current learning period Ts if the lowest value of the background noise in the previous processing cycles is less than the value of the background noise of the current cycle of the processing routine.

[0049] On the other hand, in step S50, signal processing unit 21 determines, based on the counter value, whether the current processing cycle time after the end of learning period Ts is a time to update the reference. If step S50 determines that the current processing cycle time is not a time to update the reference, the processing routine proceeds to step S70. Conversely, if step S50 determines that the current processing cycle time is a time to update the reference, the processing routine proceeds to step S60.

[0050] In step S60, signal processing unit 21 updates the value of the determination reference to the learned value of the current time. Then, signal processing unit 21 increments the counter value by 1 and subsequently terminates the current cycle of the processing routine.

[0051] After the update of the determination reference has been completed, the signal processing unit 21 determines in step S70, based on the value of the counter, whether the time of the current cycle of the processing routine lies within a usage period of the value of the determination reference.

[0052] If step S70 determines that the current processing routine cycle lies within the usage period of the reference value, the processing routine proceeds to step S80. In step S80, signal processing unit 21 increments the counter value by 1 and then terminates the current processing routine cycle.

[0053] If, on the other hand, step S70 determines that the current cycle time of the processing routine lies outside the usage period of the reference, the processing routine proceeds to step S90. In other words, the processing routine proceeds to step S90 if step S70 determines that the current cycle time of the processing routine is a start time immediately before the start of a corresponding learning period Ts, because the current cycle time of the processing routine does not coincide with 1. of the learning period Ts, 2. the time to update the reference to the determination, 3. the usage period of the intended reference.

[0054] In step S90, the signal processing unit 21 sets the value of the counter to 0 in order to initialize the counter, and sets the learning value to an initial value for the determination reference in order to initialize the learning value before the current cycle of the processing routine is completed. 4. Effects

[0055] The present embodiment described above achieves the following effects (1) to (5).

[0056] The effect (1) consists in the fact that the lowest value of the background noise in the learning period Ts is calculated as a learning value of the reference point, and the reference point is updated to the learning value at a time. Even if the background noise fluctuates, it is possible to adjust a value of the reference point according to the fluctuations of the background noise. This makes it possible to accurately detect radio wave interference.

[0057] The effect (2) consists in the fact that a change in the update cycle Tu corresponding to a change in the state of the radar device 20 enables a rapid change in a value of the determining reference when the background noise fluctuates due to changes in the state of the radar device 20.

[0058] The effect (3) is that a change in the update cycle Tu in accordance with a change in the vehicle's environment allows a rapid change in a value of the determining reference when the background noise fluctuates due to changes in the vehicle's environment.

[0059] The effect (4) is that keeping the update cycle Tu constant allows a reduction in the computational load of the signal processing unit 21.

[0060] The effect (5) is that interrupting an update of the learned value of the reference point during a measurement of radio wave interference makes it possible to prevent the reference point from becoming too small. This prevents an erroneous detection of radio wave interference. Other embodiments

[0061] Although the embodiment of the present invention has been described above, the invention is not limited to the embodiment described above, but can be implemented in various ways.

[0062] (a) In the embodiment described above, the background noise assumes the lowest power value in a frequency spectrum, but the present invention is not limited thereto. For example, a histogram of how frequently each power value appears can be generated based on a power value calculated for each frequency point or bar, and the most frequent power value can be used as a value of the background noise. An average of the power values ​​in the area excluding a region around the peak of a frequency spectrum function can also be used as the background noise.

[0063] (b) Several functions of a single component in the embodiment described above can be achieved by several components, or a single function of a single component can be achieved by several components. Furthermore, several functions of several components can be achieved by a single component, or a single function of several components can be achieved by a single component. Additionally, the configuration of the embodiment described above can be partially omitted. Furthermore, at least part of the configuration of the embodiment described above can be replaced by or added to the configuration of the other embodiment described above. Note that all modes contained within the technical ideas identified by the claims are embodiments of the present invention.

[0064] (c) The present invention can be implemented in various forms, for example as a system comprising the environmental monitoring radar device, a reference learning device, a program enabling a processing device to function as a reference learning device, a non-volatile recording medium such as a semiconductor memory on which the program is recorded, a method for learning a reference as well as the environmental monitoring radar device described above.

Claims

[1] Environmental monitoring radar device (20a, 20b) mounted on a vehicle and repeatedly transmitting and receiving radar waves to monitor a target in the vicinity of the vehicle, the device comprising: a signal generation unit (21) designed to generate a frequency difference signal indicating a frequency difference between a transmitted signal and a received signal; a spectrum generation unit (21) designed to perform a frequency analysis of the frequency difference signal generated by the signal generation unit in order to produce a frequency spectrum accordingly; a cycle setting unit (21) designed to set an update cycle for updating a determination reference, the determination reference being used to determine whether radio wave interference has occurred; a learning unit (21, S30, S40, S90) designed to learn the reference for determining the reference in order to calculate a learning value of the reference for determining the reference during a preset learning period, wherein the learning period is a period until an update time for the reference, which is determined by the update cycle set by the cycle setting unit; and an update unit (21, S60) designed to update a value of the determination reference to the learning value of the determination reference calculated by the learning unit at the update time, wherein the learning unit is designed to set the learning value to an initial value at the start of the learning period; to compare the learning value with a value of background noise of the frequency spectrum generated by the spectrum generation unit during the learning period; and to update the learning value to the value of the background noise if the value of the background noise is smaller than the learning value. [2] Environmental monitoring radar device according to claim 1, wherein the cycle setting unit is designed to change the update cycle according to a change in a state of the environmental monitoring radar device. [3] Environmental monitoring radar device according to claim 1 or 2, wherein the cycle setting unit is designed to change the update cycle according to a change in the environment of the vehicle. [4] Environmental monitoring radar device according to claim 1, wherein the cycle setting unit is designed to set the update cycle to a specific period. [5] Environmental monitoring radar device according to any one of claims 1 to 4, wherein the learning unit is designed to interrupt an update of the learning value when it is determined that a measure against radio wave interference has been carried out.

Images