JP2019023595A - Radar system - Google Patents

Abstract

To provide a radar system using a chirp signal the frequency of which continuously changes capable of achieving a control method with reduced power consumption.SOLUTION: A radar system 101 is configured to transmit plural times a chirp signal which is a modulation wave in which the frequency is continuously increased or reduced, to perform a series of detection processing of the position or speed of an object from the received signal to the respective transmission signals, and repeating the detection processing to thereby continuously detect the position of the object. As the operation mode of the detection processing, plural operation modes in which any one or more of the number of transmission, transmission interval and transmission time of the chirp signal is different are available so as to switch the operation mode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radar apparatus that detects surrounding objects using radio waves.

  Conventionally, a radar device mounted on an automobile uses a radio wave of a frequency band having excellent linearity such as a millimeter wave band (77 GHz, 79 GHz), and a signal (chirp) modulated so that the frequency continuously increases or decreases. There is known an FCM (Fast Chirp Modulation) type radar apparatus that calculates a relative distance, velocity, and direction (angle) by radiating a signal) and processing a reflected wave from a surrounding object.

  In the above signal processing, the beat signal obtained by synthesizing the transmission wave and the reception wave is digitized by A / D conversion, and further subjected to FFT processing (first time) so that the relative distance from the frequency of the beat signal to the object Ask for. In addition, the chirp signal transmission and the received wave FFT processing are repeated a plurality of times, and the detected frequency component is subjected to the FFT processing (second time) to obtain the relative velocity with the object from the phase rotation frequency of the beat signal. .

  As a radar apparatus using the above FCM method, for example, a radar apparatus described in Patent Document 1 has been proposed.

JP 2016-3873 A

  In the above-described radar apparatus using the FCM method, a series of processes are repeatedly performed, in which the chirp signal is transmitted, the received beat signal is A / D converted at high speed, and the converted signal is subjected to FFT processing. For this reason, there is a problem that the power consumption of the apparatus becomes large for transmission / reception of these radio waves and signal processing.

  An object of the present invention is to provide a radar apparatus that realizes a control method with reduced power consumption in a radar apparatus using the FCM method.

In order to solve the above problems, in the present invention,
A chirp signal, which is a modulated wave whose frequency is continuously increased or decreased, is transmitted a plurality of times, the object position or velocity is detected from the received signal for each transmitted signal, and the detection process is repeated. In the radar apparatus that continuously detects the position of the object, the operation mode of the detection processing has a plurality of operation modes in which at least one of the number of transmissions of the chirp signal, the transmission interval, or the transmission time is different. The operation mode can be switched.

  ADVANTAGE OF THE INVENTION According to this invention, the radar apparatus which reduced the power consumption of an apparatus can be provided.

1 is a block diagram of a radar apparatus according to a first embodiment of the present invention. 1 is a block diagram of a radar apparatus according to a first embodiment of the present invention. Illustration of radar detection operation by FCM method Explanatory drawing of the operation mode of the radar apparatus of FIG. Explanatory drawing of the control method in the control processing part of FIG. Explanatory drawing of the operation mode of the radar apparatus of FIG. Configuration diagram of radar apparatus according to second embodiment of the present invention Explanatory drawing of the operation mode of the radar apparatus of FIG. Configuration diagram of radar apparatus according to third embodiment of the present invention Explanatory drawing of the operation mode of the radar apparatus of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  1, FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6 are explanatory views of an embodiment of the present invention. 1 and 2 are configuration diagrams of a radar apparatus mounted on a vehicle according to the present invention. FIG. 3 is a diagram illustrating the principle of radar detection operation by the FCM method, and FIGS. 4, 5, and 6 are diagrams illustrating the transmission operation of the radar. The present embodiment is an example of a radar apparatus that is mounted on an automobile and reduces the power consumption by reducing the number of times of transmission of a chirp signal to be transmitted according to the situation.

  Prior to the description, the detection principle by the FCM (Fast Chirp Modulation) method will be described with reference to FIG. The radar device radiates radio waves and detects the position, velocity, etc. based on the received waves reflected by the surrounding objects. In the FCM system, a signal (chirp signal), that is, a transmission wave 301 that is modulated so that its frequency increases uniformly in a ramp shape is emitted. A signal in which the radio wave is reflected back to the object, that is, a reception wave 302 is received. The reception wave 302 is received with a delay by a time corresponding to the distance reciprocating between the radar apparatus and the object with respect to the transmission wave 301. A frequency difference occurs between the transmission wave 301 and the reception wave 302 due to a delay, and a beat signal 303 is obtained by synthesizing two waveforms having different frequencies. The frequency of the beat signal is determined according to the delay time (ie, distance) between the transmission wave 301 and the reception wave 302 before synthesis. Therefore, the distance can be obtained from the frequency of the beat signal.

  Therefore, in order to obtain the frequency of the beat signal, after conversion by the A / D converter 304, the FFT processor 305 performs frequency conversion (first FFT processing). As a result, a signal strength 306 is obtained for each frequency band (distance BIN). Further, a strong signal is obtained at the distance BIN where the object exists. In this first FFT processing, the maximum distance that can be detected and the resolution of the distance are determined according to the sampling frequency and the number of samples during the A / D conversion. That is, the higher the sampling frequency, the higher the frequency of the beat signal can be detected, and as a result, it is possible to detect farther distances. Also, the greater the number of samplings, that is, the longer the sampling period, the lower the beat frequency can be detected and the higher the distance resolution.

  When the radar apparatus and the object have relative velocities, the phase of the beat signal obtained from each chirp signal rotates. Further, the rotational speed of the phase is determined according to the relative speed with respect to the object. Therefore, the relative speed with respect to the object is obtained from the rotational speed of the phase of the beat signal. For this purpose, the chirp signal is transmitted a plurality of times (the number of times indicated by n in the figure, for example, 1024 times, etc.), and the signal component of the same distance BIN for each chirp signal is again processed by the FFT processor 307. Frequency conversion (second FFT processing) is performed, and as a result, a signal strength 308 for each frequency band (speed BIN) is obtained. Based on the signal intensity 308 obtained as a result of the two FFT processes as described above, the peak portion 309 is detected. The speed BIN where the peak 309 exists indicates the number of rotations of the phase, that is, the speed of the detected object. A distance BIN where the peak 309 exists indicates a relative distance to the object.

  In the second FFT processing, the earlier the chirp signal transmission cycle is, the higher the phase change period can be detected, and as a result, the faster speed can be detected. Further, the longer the transmission period for repeatedly transmitting the chirp signal, the lower the phase change period can be detected, and as a result, the speed resolution can be increased. That is, when the chirp signal transmission cycle is changed, the upper limit of the relative speed that can be detected changes. For example, if the chirp signal transmission cycle is early, the upper limit of the detection speed is faster, while if the chirp signal transmission cycle is slower, the upper limit of the detection speed is lower. Further, when the transmission period of the chirp signal is increased or decreased, for example, when the transmission cycle is the same and the number of transmissions is increased or decreased, the detection speed resolution is increased or decreased.

  When there are a plurality of detected objects, there are also a plurality of detected peaks, and the position and speed can be detected for each object.

  Next, the configuration of the radar apparatus of the present invention will be described with reference to FIGS. In FIG. 1, 101 is a radar device of the present invention, 102 is a control processing unit for controlling the radar device and processing signals, and is composed of a control element such as a CPU. 103 is a PLL (Phase Locked Loop) or VCO (Voltage). The oscillator whose output frequency is controlled by the control processing unit 102, 104 is a transmission unit that amplifies and outputs the signal output by the preceding oscillator 104, 105 is a transmission antenna, 106 is a reception antenna, A signal 107 received by the receiving antenna and the modulated signal output from the oscillator 103 are mixed by the mixer 108 to generate a difference beat signal. After the unnecessary frequency is removed by the band limitation, the signal is sent to the A / D converter 109. Receiving unit 110 for conversion and output, 110 communicates with an external device That for interface, 111 based on the information of the detected object from the radar device, a vehicle control unit for controlling the vehicle.

  2 is a diagram showing details of the control processing unit 102 shown in FIG. 1, in which 102 is an operation mode selection unit for selecting an operation mode (described later), and 202 is an operation mode from the operation mode selection unit. The transmission control unit 203 controls the oscillation output of the oscillator 103 and its frequency based on the instruction of the A / D converter, and the 203 performs the first FFT process and the second FF process as described above for the A / D converted beat signal. Reference numeral 204 denotes an FFT processing unit that converts the signal intensity for each distance BIN and speed BIN, and 204 is a detected object calculation unit that detects the position and distance of the object from the signal intensity based on the FFT processing result.

  Next, the operation will be described with reference to FIG. The radar apparatus according to the present invention has two modes of operation mode 1 and operation mode 2, which are different in the transmission form of the chirp signal. In operation mode 1, the chirp signal is repeatedly transmitted n times, and after a certain pause period, the same transmission is repeated again. The control processing unit 102 performs FFT processing of the received wave in parallel with the transmission of the chirp signal, and further performs detection object calculation processing and the like during the pause period. The transmission of these chirp signals and the rest period thereafter are set as one cycle (referred to as one frame), and the object detection process is performed once in that frame. In the next frame, the chirp signal is transmitted again, and a new detection process is repeatedly performed based on the received signal. Although the frame 401 in the operation mode 1 shows an example in which the chirp signal is transmitted n times, the number of transmissions is, for example, 1024 (2 to the 10th power), and the number of transmissions is a power of 2. This is the number of times that the chirp signal is transmitted to the power of 2 in accordance with the FFT processing because the number of times the chirp signal is transmitted is the number of inputs of the second FFT in the processing in the FFT processing unit 203.

In operation mode 2, the number of chirp signal transmissions in frame 402 is 1/2 ^{m of the} number of transmissions in operation mode 1 (where m is a natural number of 1 or more). In operation mode 2, the number of transmissions of the chirp signal is reduced, but for the same reason as described above, the number of transmissions is set to a power of 2 for the second FFT processing. Further, by taking a long pause period after chirp transmission, the time of one frame is set to the same time in the operation mode 1 and the operation mode 2 so that the period of one detection operation is the same.

  The operation mode 2 is different from the operation mode 1 in that the number of transmissions of the chirp signal is reduced to reduce the transmission power, and the A / D converter 109 performs conversion processing according to the number of times the number of chirp signals is reduced. Furthermore, since the number of first FFT processing in the FFT processing unit 203 and the number of input data of the second FFT processing are reduced, the power required for the processing can be reduced.

On the other hand, in the operation mode 2, in order to reduce the number of transmissions of the chirp signal, the resolution of the detection speed is lowered according to how the number of transmissions is reduced. For example, when the number of transmissions is halved, the resolution of the speed is lowered to ½. In other words, if the resolution was 1 km / h until then, it would be 2 km / h. However, since the upper limit speed for detecting the maximum speed depends on the transmission cycle of the chirp signal, the operation mode 1 and the operation mode 2 are equivalent.
In the operation mode 2, the speed detection resolution is lower than that in the operation mode 1, but the power consumption can be reduced.

As described above, when increasing or decreasing the number of times of transmission of the chirp signal, the transmission interval, or the transmission time, the radar apparatus increases the power of 2 or decreases it to 1 of the power of 2. It has a characteristic configuration.

  The control processing unit 102 switches the two operation modes within a range that does not hinder the operation of the radar device while monitoring the object detection status, and reduces power consumption. Next, the operation will be described. The operation mode selection unit 201 of the control processing unit 102 selects, for example, to operate in the operation mode 1 at the time of startup, and instructs the transmission control unit 202 to transmit the chirp signal of the operation mode 1 together with the FFT. The processing unit 203 is instructed about the number of FFT processes corresponding to the selected operation mode. Further, information on the selected operation mode is notified to the vehicle control unit 111 connected to the outside via the communication interface 110. The transmission control unit 202 controls the oscillator 103 so as to transmit a chirp signal of the instructed operation mode, and transmits the chirp signal. The FFT processing unit 203 performs an FFT process according to the transmission mode, and outputs the processing result to the detected object calculation unit 204. In other words, the radar apparatus outputs information related to the operation mode of the detection process to an externally connected apparatus. The detected object calculation unit 104 calculates the peak value of the signal intensity from the input FFT processing result, the distance to the object, and the relative speed based on the previous detection result, and the result is obtained via the communication interface 110. Notify the vehicle control unit 111. At the same time, the operation mode selection unit 201 is notified of the detection result.

  The operation mode selection unit 201 selects the operation mode of the next frame based on the detection result of the detected object calculation unit 204 using, for example, the determination condition shown in FIG. For example, when there is no detected object, the operation mode 2 is selected to reduce power consumption. Alternatively, even when a detected object exists, if the distance from the object is far away, the operation mode 2 is selected because the resolution of the speed is acceptable even if it is low. When the detected object exists nearby, the operation mode 1 is selected to increase the detection accuracy. As described above, the operation mode selection unit 201 selects an operation mode according to the detection status, instructs the selected control mode to the transmission control unit, continues the subsequent detection repeatedly, and detects the object detection status. When it changes, it operates to change the operation mode each time. In other words, the radar apparatus includes a control processing unit that selects an operation mode and controls chirp signal transmission and object detection processing according to the selection, and the control processing unit includes at least an object detection result or an external input. The operation mode is selected according to one of them. Therefore, even when the operation mode 2 that reduces power consumption is selected, the operation as a radar apparatus is less hindered because the operation mode 1 is switched to the measurement mode 1 that performs measurement with higher accuracy when necessary.

  In the above description, the description is given on the assumption that there is only one detected object. However, when there are a plurality of detected objects, if any one of the detected objects meets the conditions of the operation mode 1, the operation mode Operate to select 1. Or you may judge combining conditions, such as the number of objects to be detected, a position, or speed.

  The selected operation mode or the resolution of the detection speed linked to the operation mode is notified to the vehicle control unit 111 via the communication interface 110. The vehicle control unit 111 can receive information on the resolution of the detection speed as information related to the operation mode or the operation mode, and can use it for determination at the time of vehicle control.

In the example shown in FIG. 4, the case where the operation mode 1 and the operation mode 2 are switched as the operation mode has been described. However, the present invention is not limited to this, and the number of chirp signal transmissions is further reduced as shown in FIG. Alternatively, the operation mode 3 may be added to select any one of the operation modes 1, 2, and 3. This figure is obtained by adding an operation mode 3 in which the number of chirp signals to be transmitted is further reduced in addition to the operation mode 1 and the operation mode 2 described in FIG. In the frame 603 of this operation mode 3, the number of chirp signal transmissions is ½ ^{m ′} (where m ′ is a natural number exceeding m shown in the frame 602). As already described, the number of transmissions is set to a power of 2 for the second FFT process. In addition, with a pause period after chirp transmission, the time for one frame is set to the same time as in operation mode 1 or operation mode 2 so that the cycle of one detection operation is the same.

  As described above, a device that transmits a modulated wave with a changed transmission frequency and detects the object based on a received wave reflected by a surrounding object, and continuously increases or decreases the frequency. The chirp signal, which is a modulated wave, is transmitted multiple times, the object position or the object position or velocity is detected from the received signal for each transmission signal, and the object position is continuously detected by repeating the detection process. In the radar apparatus using the FCM method, the detection process is performed by switching among a plurality of operation modes in which any one or more of the number of transmissions of the chirp signal to be transmitted, the transmission interval, or the transmission time is different. With this configuration, the power consumption of the apparatus can be reduced. In addition, since the cycle of one detection process is set to be the same in the frame 401 and the frame 402, the detection process cycle is maintained even when the operation mode is switched, so the object detection cycle does not change. The notification cycle of the detection detection result to the outside is also the same, and the influence on the processing operation of the external vehicle control unit 111 can be reduced.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The present invention is an example in which selection of an operation mode is instructed from an external device and detection processing is performed in the instructed operation mode.

  FIG. 7 is a diagram showing a control processing unit of the radar apparatus and a vehicle control unit connected to the outside. In FIG. 7, reference numeral 701 denotes a camera for photographing the outside of the vehicle and monitoring obstacles, road surface conditions, and the like. A map storage unit that stores map information, a position detection unit 703 such as a GPS, a vehicle speed detection unit 704 that detects the speed of the vehicle, and other components that operate in the same manner as in FIGS. 1 and 2 are the same. The code | symbol is attached | subjected. The vehicle control unit 111 shown in FIG. 7 determines the radar operation mode based on various sensors and map information connected to the outside. For example, the operation mode of the radar apparatus 101 is determined depending on whether the vehicle is traveling on a highway or in an urban area. In an urban area, an object to be detected such as a host vehicle, another vehicle, or a pedestrian may travel at a relatively low speed and may have a low relative speed with the detectable object. On the other hand, on a highway, a higher relative speed needs to be detected. The vehicle control unit 111 instructs an operation mode to the radar apparatus 101 according to the traveling state of the host vehicle.

Next, the operation mode will be described with reference to FIG. In the frame 801 of the operation mode 1 in the figure, the chirp signal is repeatedly transmitted n times (where n is a power of 2), and the same transmission is repeated again after a certain pause period. Further, in the frame 802 in the operation mode 2, the number of transmissions of the chirp signal is 1/2 ^{m of the} number of transmissions in the operation mode 1 (where m is a natural number of 1 or more), but between one chirp signal and the next one. The transmission period is lowered with a pause period. That is, the chirp signal is transmitted once every 2 ^m times as compared with the transmission of the chirp signal in the frame 801. As a result, the period during which the chirp signal is transmitted is approximately the same length in frames 801 and 802. Thereby, in the operation mode 2, the detection upper limit value of the relative speed with respect to the object to be detected becomes 1/2 ^{m in} the case of the operation mode 1. However, the speed resolution is the same in operation modes 1 and 2. In this operation mode 2, since the number of times of chirp signal transmission is reduced and the number of FFT processing is also reduced accordingly, the power consumption for the detection operation can be reduced.

The vehicle control unit 111 instructs the radar apparatus 101 to operate in the operation mode 1 or the operation mode 2 according to the traveling state of the host vehicle. Further, in the case of the operation mode 2, for example, if the number of times of the chirp signal transmission in the operation mode 2 is ½ ^m of that in the mode 1, the parameter m is designated to designate the chirp signal transmission cycle. You can also.

  In the case of the present embodiment, the external vehicle control unit 111 designates the operation mode 1 according to the traveling state of the vehicle, for example, when traveling on a highway, and when the vehicle is traveling in an urban area, the upper limit of the detection speed. By specifying operation mode 2 that operates with lower power consumption but lower power consumption, the power consumption of the radar apparatus can be reduced.

  Next, a third embodiment of the present invention will be described with reference to FIGS. The present invention is an example in which a temperature sensor is provided in a radar apparatus and an operation mode is selected according to the output.

  FIG. 9 is a diagram showing a control processing unit of the radar apparatus. In FIG. 9, reference numeral 901 denotes a temperature sensor provided in the radar apparatus, and the other components that operate in the same manner as in FIGS. 1 and 2 are the same. The code | symbol is attached | subjected. The operation mode selection unit 201 shown in the figure performs an operation mode selection process based on the detection result of the detected object calculation unit 204 as in the case of the first embodiment. Further, the temperature of the radar apparatus itself is measured by the temperature sensor 901. As a result of this measurement, when the apparatus temperature rises above a predetermined value, the operation mode selection unit 201 operates to select an operation mode with less power consumption. Further, the operation mode selection unit 201 notifies, for example, information relating to detection accuracy to the external vehicle control unit or the like via the interface unit as the selected operation mode or information related to the operation mode. As a result, the vehicle control unit can recognize that the operation mode has been changed, and can make a determination accordingly.

  FIG. 10 shows an example of the operation mode. In the frame 1001 of the operation mode 1 shown in the figure, the chirp signal is repeatedly transmitted n times (where n is a power of 2), and the same transmission is repeated again after a certain pause period. Here, it is assumed that the number of samples when the beat signal generated from the received wave for one transmission of the chirp signal is captured by A / D conversion is S.

On the other hand, in the frame 1002 in the operation mode 2, the frequency change speed at the time of transmitting the chirp signal is the same as that in the frame 1001, and the transmission time per one time is reduced to approximately ½ ^m . At the same time, the number of samples when the beat signal is A / D converted is reduced to S / 2 ^m . Reducing the number of samples at the time of A / D conversion means that the number of inputs of the first FFT is reduced as described with reference to FIG. 3, and the resolution of the relative distance to the object to be detected is lowered. When the number of samples is set to 1/2 ^m as in the frame 1002, the distance resolution is also reduced to 1/2 ^m . Since the transmission time of the chirp signal is reduced and the number of input data to be subjected to FFT processing is reduced and the amount of processing is reduced, the power consumption required for these processes can be reduced. In the operation mode 2 as well, since the sampling cycle is the same, the maximum value of the detected relative distance is the same. Regarding the detection of the relative speed, the number of chirp signals to be transmitted is the same in the operation modes 1 and 2, and since both are the same n times, the maximum value and resolution of the relative speed that can be detected are the same.

  As described above, the operation mode 2 can reduce the power consumption, although the resolution of the relative distance is lower than that of the operation mode 1.

  In the above example, when the radar apparatus becomes hot, selecting the operation mode 2 can reduce the power consumption and suppress the temperature rise of the apparatus. Further, by suppressing the temperature rise, the reliability of the apparatus is improved.

  The operation mode is changed according to the detection result of the temperature sensor 901. However, the operation mode is not limited to the temperature sensor. For example, the voltage of the input power source is monitored as another detection device, and the voltage is less than a predetermined value. In this case, the operation mode may be switched to the operation mode 2 in order to operate with lower power consumption.

  In the description of each embodiment described above, the description has been made on the assumption that there is one reception antenna. However, when a plurality of reception antennas are provided, the reception processing and FFT processing are similarly performed on the reception signal at each antenna. From the plurality of processing results, the detected object calculation unit can also detect the object.

  As an operation mode with reduced transmission power, when the number of chirp signal transmissions is reduced (FIGS. 4 and 6), when the chirp signal transmission cycle is lengthened (FIG. 8), or when the chirp signal transmission time is shortened Each example in the case (FIG. 10) has been described, but it is also possible to carry out these simultaneously to further reduce power consumption.

  Further, the case where the frequency of chirp signal transmission is continuously increased has been described as an example, but conversely, operation can be similarly performed using a transmission wave whose frequency decreases continuously.

DESCRIPTION OF SYMBOLS 101 Radar apparatus 102 Control processing part 103 Oscillator 104 Transmission part 105 Transmission antenna 106 Reception antenna 107 Reception part 108 Mixer 109 A / D converter 110 Interface 111 Vehicle control part

Claims (4)

A device that transmits a modulated wave with a changed transmission frequency and detects the object based on a received wave reflected by a surrounding object,
Transmits a chirp signal, which is a modulated wave whose frequency is continuously increased or decreased, multiple times, performs detection processing of the position or speed of the object from the received signal for each transmitted signal,
In a radar apparatus that continuously detects the position of an object by repeatedly performing the detection process,
The operation mode of the detection process includes a plurality of operation modes in which any one or more of the number of times of transmission of the chirp signal, a transmission interval, or a transmission time is different, and the operation mode can be switched. Radar device. The radar apparatus according to claim 1, wherein
The radar apparatus includes a control processing unit that selects the operation mode and controls transmission of the chirp signal and object detection processing according to the selection.
The radar apparatus according to claim 1, wherein the control processing unit selects an operation mode according to at least one of an object detection result or an external input. The radar apparatus according to claim 1 or 2,
The radar apparatus outputs information related to an operation mode of detection processing to an externally connected apparatus. The radar apparatus according to any one of claims 1 to 3,
The radar apparatus is characterized in that when increasing or decreasing the number of transmissions, transmission interval, or transmission time of the chirp signal, it is increased to a power of 2 or decreased to a power of 2. Radar device.

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