JP2010203788A - Vehicle radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the accuracy of distance measuring performed based on a difference between a receiving waveform and a reference waveform even if the environment around a vehicle changes. <P>SOLUTION: A receiving waveform sampling part 51 samples receiving waveform signals at predetermined time intervals. The intervals of sampling receiving waveform signals are preferably set based on the speed of the vehicle. A reference waveform acquiring part 52 collects a predetermined number of the sampled receiving waveform signals, performs statistic processing on the sampled receiving waveform signals, and obtains a statistically processed waveform signal as a reference waveform signal. The acquisition of the reference waveform by statistic processing is repeated while the vehicle is running, so that the currently held reference waveform is updated to the latest reference waveform. Thereby, it is possible to maintain the accuracy of distance measuring even if the environment around the vehicle changes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicular radar apparatus that transmits a radar wave to the outside of a vehicle, receives a reflected wave reflected by an object existing around the vehicle, and performs distance measurement.

  A general pulse radar device calculates a distance based on a round-trip propagation time until a transmitted pulse signal is reflected by a target to be measured and received. For example, Patent Document 1 discloses a pulse radar device that transmits a pulse to the outside in a wide band and samples a received waveform received in the wide band with a wide band sampling pulse.

Japanese National Patent Publication No. 10-511182

  The received waveform required for ranging by the radar device is only the waveform reflected by the target to be measured, but in reality, ranging including the pulse waveform that jumps directly from the transmitting antenna to the receiving antenna. A waveform on which a reflected wave other than the target of interest is superimposed is received.

  Therefore, a method is known in which accurate distance measurement is performed by preliminarily holding a waveform caused by influences other than these targets as a reference waveform and taking a difference between the received waveform (input waveform) and the reference waveform.

  However, in a radar apparatus mounted on a vehicle, the environment around the vehicle greatly changes during traveling, and reflected waves other than the distance measurement object due to a change in road surface shape or the appearance of a manhole or a joint change greatly. For this reason, it is difficult to maintain accurate distance measurement only by previously holding a reference waveform assumed in advance.

  The present invention has been made in view of the above circumstances, and a vehicle capable of maintaining accurate distance measurement even when the environment around the vehicle changes when distance measurement is performed based on the difference between the received waveform and the reference waveform. An object of the present invention is to provide an industrial radar device.

  In order to achieve the above object, a vehicle radar apparatus according to the present invention receives a reflected wave reflected by an object from a radar wave transmitted to the outside of the vehicle as a received waveform, and based on the difference between the received waveform and a reference waveform. A radar device for a vehicle that measures a distance to an object, wherein the received waveform sample unit samples the received waveform at a predetermined interval when the vehicle travels, and the received waveform sampled by the received waveform sample unit is statistically processed and A reference waveform acquisition unit that acquires a reference waveform, and a reference waveform update unit that updates a reference waveform currently held by the reference waveform acquired by the reference waveform acquisition unit are provided.

  According to the present invention, when ranging is performed based on the difference between the received waveform and the reference waveform, the received waveform sampled at a predetermined interval during traveling is statistically processed to acquire the reference waveform, and is currently held Since the reference waveform is updated, accurate ranging can be maintained even when the environment around the vehicle changes.

Configuration diagram of a radar device for vehicles Illustration of differential waveform Block diagram of reference waveform acquisition function Reference waveform acquisition processing flowchart Explanatory diagram showing the relationship between vehicle speed and sampling interval

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a vehicle radar device (hereinafter simply referred to as “radar device”) that measures the distance to an object 100 that is mounted on a vehicle such as an automobile and exists around the vehicle. The radar apparatus 1 is basically configured of a radar unit 20 including a transmission antenna 2a, a reception antenna 2b, and a signal processing circuit unit 5, and a control unit 50 that controls the radar unit 20 to perform ranging processing and the like. ing.

  Although FIG. 1 shows a transmission / reception antenna separation type device in which the transmission antenna 2a and the reception antenna 2b are separated, the transmission antenna 2a and the reception antenna 2b may be integrated. Further, in FIG. 1, one radar unit 20 is shown, but the number of radar units 20 is a number according to application to an actual automobile. When a plurality of radar units 20 are mounted on the vehicle, ranging is performed while switching the radar unit 20 to be controlled by the control unit 50.

  The signal processing circuit unit 5 shows an example in which a known equivalent time sampling method is adopted in FIG. That is, the signal processing circuit unit 5 includes a pulse generation unit 6, a band pass filter (BPF) 7, a sweep waveform generation unit 8, a time sweep pulse generation unit 9, a band pass filter 10, and a sample / hold (S / H) circuit 11. , A low-pass filter (LPF) 12 and an amplifier 13.

  The pulse generator 6 generates a transmission pulse having a predetermined frequency in synchronization with the clock signal CLK1 supplied from the control unit 50. This transmission pulse is limited to a predetermined frequency band by a bandpass filter (BPF) 7 and transmitted as a radar wave from the transmission antenna 2a to the outside of the vehicle.

  The sweep waveform generation unit 8 generates a sweep signal having a waveform (for example, a ramp wave) for frequency sweeping the transmission pulse using the timing signal CLK2 for each frame supplied from the control unit 50 as a trigger. This sweep signal is input to the time sweep pulse generator 9.

  The time sweep pulse generation unit 9 is synchronized with the clock signal CLK1 from the control unit 50 and based on the sweep signal output from the sweep waveform generation unit 8, the time sweep pulse delayed by a predetermined amount with respect to the transmission pulse. Is generated. This time sweep pulse is input to the sample / hold circuit 11.

  The sample / hold circuit 11 uses the time sweep pulse as a trigger to temporarily hold and sample the received signal received by the receiving antenna 2b and from which noise has been removed by the bandpass filter 10. The sampling waveform at this time is a waveform obtained by expanding the waveform received by the receiving antenna 2b on the time axis (equivalent time sampling).

  The reception waveform sampled for the equivalent time is passed to the low-pass filter 12 to cut high-frequency noise. Further, the signal passing through the low-pass filter 12 is amplified to a predetermined output level by the amplifier 13 and input to the control unit 50.

  The control unit 50 is a central configuration of a ranging system using the radar unit 20. The control unit 50 is a peripheral circuit that outputs a clock signal and timing signal to the signal processing circuit unit 5 with a microprocessor at the center, and an analog signal (signal from the amplifier 13) input from the signal processing circuit unit 5 as a digital signal. An A / D converter or the like for converting the signal to the signal is provided.

  The control unit 50 supplies a clock signal and a timing signal to the signal processing circuit unit 5 and performs distance measurement processing for calculating a distance to an object existing outside the vehicle based on the received signal processed by the signal processing circuit unit 5. Mainly done. This distance measurement process is performed based on a differential waveform as shown by a solid line in FIG.

  That is, the control unit 50 holds the baseband waveform shown by the alternate long and short dash line in FIG. 2 as the reference waveform. Then, a differential waveform between the reference waveform and a received waveform (a waveform indicated by a broken line in FIG. 2) acquired via the receiving antenna 2b and the signal processing circuit unit 5 is calculated, and distance measurement is performed based on the differential waveform. Do.

  The received waveform in FIG. 2 shows data obtained by A / D converting the waveform of one frame (one cycle) with a resolution of 200 samples and 8 bits. The period of one frame is, for example, about 20 to 40 msec.

  In addition, as a reception waveform when calculating the differential waveform, a raw waveform acquired via the reception antenna 2b and the signal processing circuit unit 5 may be used, but in order to further reduce the influence of noise or the like, a plurality of waveforms are used. A waveform obtained by statistically processing the raw waveform may be handled as a received waveform.

  Ranging based on the difference waveform can be performed using a general method based on an absolute average value based on the overall size of the difference waveform, and other various methods. At this time, distance measurement can be performed by acquiring a reflected waveform in a situation where an object to be measured does not exist in the vehicle external environment as a reference waveform held by the control unit 50. For example, the reflection waveform in the standard road surface condition where the object to be measured does not exist is acquired by offline experiment or simulation, and written in the memory in advance, or a value suitable for each vehicle at the time of inspection at the time of shipment By writing, distance measurement becomes possible.

  However, the above-described method in which the reference waveform is held in advance in the system may cause accurate distance measurement only under standard road surface conditions. Therefore, as shown in FIG. 3, the control unit 50 includes a received waveform sample unit 51, a reference waveform acquisition unit 52, and a reference waveform update unit 52 as functions for acquiring a reference waveform, and the reference waveform during traveling Get while learning.

  The reception waveform sample unit 51 samples the reception waveform signal (measurement waveform signal) output from the amplifier 13 of the signal processing circuit unit 5 at a predetermined time interval. The sampling interval of the measurement waveform signal is set to an interval much longer than one frame of the received waveform, for example, an interval of 2 sec.

  In this case, the measurement waveform may be sampled at a predetermined interval, but it is desirable to vary the sampling interval according to the traveling speed of the vehicle. That is, while the vehicle is running at a low speed, the road surface condition with a short distance is sampled. When the vehicle is running at a high speed, the road surface condition is sampled with a long distance. Therefore, by changing the acquisition timing of the reference waveform according to the vehicle speed, it is possible to perform sampling of a certain road surface length regardless of the vehicle speed.

  The reference waveform acquisition unit 52 collects a predetermined number of measurement waveform signals sampled by the reception waveform sample unit 51 and performs statistical processing, and sends the statistically processed waveform signals as reference waveform signals to a distance measurement processing unit (not shown). The acquisition of the reference waveform by the statistical processing is performed by any one of average value extraction, median value extraction, and mode value extraction, and is repeatedly executed while the vehicle is running. For example, when the received waveform is sampled at intervals of 2 seconds, 8 (14 seconds) are collected and averaged, and the averaged waveform is used as the reference waveform.

  The reference waveform update unit 53 updates the currently held reference waveform with the latest reference waveform acquired by the reference waveform acquisition unit 52. For example, when a received waveform is sampled at intervals of 2 seconds and an average value (moving average value) of 8 samples is used as a reference waveform, the reference waveform is updated at intervals of 2 seconds.

  However, it is desirable to stop updating the reference waveform when the following conditions (1) and (2) are satisfied.

(1) When the difference value between the frame of the current reference waveform and the measurement waveform exceeds the threshold value When the difference value between the frame of the current reference waveform and the measurement waveform becomes large, the detection state is due to the approach of the object. Is expected. At this time, if the reference waveform is updated, there is a possibility that even if the object detection state is entered, the difference value becomes small due to statistical processing, and the object cannot be detected. Therefore, it is possible to prevent the object from being lost by setting a threshold value indicating the presence of the object in advance and not updating the reference waveform when the difference waveform exceeds the threshold value.

(2) When the vehicle is stopped When the vehicle is not moving, it is not necessary to update the reference signal. If the measured waveform changes in response to this, it is estimated that the object around the vehicle has changed. Therefore, when the stop state of the vehicle is detected from a vehicle speed signal from a wheel speed sensor or the like, the reference waveform immediately before the vehicle stop state is maintained and the update is stopped. This makes it possible to prevent erroneous determination due to updating the reference waveform.

  The reference waveform update unit 53 stores the reference waveform data in a non-volatile memory such as a flash memory before the system is stopped. Then, it is read from the memory at the next system startup, and the read reference waveform is set as an initial value at the system startup. That is, since the reference waveform has not been acquired at the time of system startup, it is possible to accurately detect an object from the time of system startup by reading the reference waveform stored at the previous system stop.

  Here, when the system is stopped, the distance measurement operation is stopped when the power to the radar unit 20 and the control unit 50 is turned off, or even when the power is supplied, the control unit 50 is in the standby state. This is when the operation is stopped. When the system is stopped, the operation is stopped after various data saving processing and the like are executed. On the other hand, the time when the system is started is when power is supplied to the radar unit 20 and the control unit 50 to start the distance measuring operation, or when the control unit 50 returns from the standby state and starts the distance measuring operation.

  The process related to the acquisition of the reference waveform in the control unit 50 is performed by, for example, the program process shown in the flowchart of FIG. Next, the reference waveform acquisition program processing will be described.

  The program process shown in FIG. 4 is a process executed after the system is started and initialized. First, in the first step S1, the reference waveform stored at the time of the previous system stop is read, and the object can be detected as the initial reference waveform after the system is started.

  Subsequently, it progresses to step S2 and it is judged based on signals, such as a wheel speed sensor, whether the vehicle is a stop state. As a result, when the vehicle is traveling, the process proceeds from step S2 to step S3, and a sampling interval for securing a predetermined number of received waveforms according to the vehicle speed is set.

  For example, when 8 samples are ensured during the travel distance of 100 m, the relationship between the vehicle speed V and the sampling interval S is mapped as shown in FIG. Then, the sampling interval S corresponding to the vehicle speed V is set with reference to this map.

  In step S4 following step S3, the received waveform is sampled at the sampling interval S. In step S5, it is determined whether or not the difference value between the current reference waveform and the received waveform exceeds a threshold value indicating the presence of an object. As a result, if the difference value exceeds the threshold value, the update of the reference waveform is stopped while the current reference waveform is held in step S6, and the process returns to step S2.

  On the other hand, if the difference value does not exceed the threshold value in step S5, the received waveform of a predetermined number of samples (for example, 8) is statistically processed (averaged here) and acquired as a reference waveform in step S7. In step S8, the currently held reference waveform is updated with the newly acquired reference waveform, and the process returns to step S2.

  Thereafter, when it is detected in step S2 that the vehicle has stopped, the process branches from step S2 to step S9 to determine whether or not the system is stopped. If the system is not stopped, the updating of the reference waveform is stopped while the reference waveform updated last before the system is stopped in step S10, and the process returns to step S2. On the other hand, if the system is stopped, the current reference waveform is stored in the flash memory or the like in step S11, and other save processing is performed to end this processing.

  As described above, in the present embodiment, when distance measurement is performed based on the difference between the received waveform and the reference signal, the received waveform sampled at a predetermined interval during running is statistically processed to obtain the reference signal, and always Update to the latest value. Thereby, even if the environment around the vehicle changes greatly, distance measurement can be performed using the reference signal corresponding to the environment change, and accurate distance measurement can be maintained.

  At that time, by changing the timing of sampling the received waveform according to the vehicle speed, it is possible to acquire a reference signal at a constant road surface length. This reference signal is not updated when an object is detected or when the vehicle is stopped, thereby preventing an object from not being detected or erroneously determined. Further, when the system is started, the reference waveform stored before the system is stopped can be used to accurately detect an object from the time of starting the system.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 20 Radar unit 50 Control unit 51 Received waveform sample part 52 Reference waveform acquisition part 53 Reference waveform update part 100 Object

Claims (6)

A radar device for a vehicle that receives a reflected wave reflected by an object as a received waveform from a radar wave transmitted to the outside of the vehicle, and performs distance measurement on the object based on a difference between the received waveform and a reference waveform,
A received waveform sampler that samples the received waveform at predetermined intervals when the vehicle is running;
A reference waveform acquisition unit that statistically processes the reception waveform sampled by the reception waveform sample unit and acquires the reference waveform;
A vehicular radar apparatus comprising: a reference waveform update unit that updates a reference waveform currently held by the reference waveform acquired by the reference waveform acquisition unit.   The vehicular radar apparatus according to claim 1, wherein the reception waveform sampling unit varies an interval for sampling the reception waveform in accordance with a vehicle speed.   3. The vehicular radar according to claim 1, wherein the reference waveform update unit stops updating the reference waveform when a difference value between the received waveform and the reference waveform exceeds a predetermined threshold value. apparatus.   The vehicle according to any one of claims 1 to 3, wherein the reference waveform update unit holds the reference waveform acquired before the vehicle stops and stops updating the reference waveform when the vehicle stops. Radar equipment.   The said reference waveform update part memorize | stores the said reference waveform before a system stop, and makes this memorize | stored reference waveform the reference waveform at the time of the next system starting, The any one of Claims 1-4 characterized by the above-mentioned. Vehicle radar system.   6. The vehicular radar apparatus according to claim 1, wherein the statistical processing is any one of average value extraction, median value extraction, and mode value extraction.

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