JP3208229B2 - Forward warning radar system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular forward-looking radar device mounted on a vehicle to watch an obstacle existing in front of the vehicle, and more particularly, to a radar system for tracking a reflected signal from an obstacle. The present invention relates to a method for searching for a car or the like.

[0002]

2. Description of the Related Art A forward warning radar device for a vehicle is mounted on a vehicle such as an automobile and contributes to forward warning of the vehicle. This type of device can be configured to detect a distance based on, for example, a time delay of a reflection signal with respect to a transmission signal. That is, a predetermined transmission signal is transmitted in front of the vehicle, a reflection signal from an obstacle is received, and a time delay of the reflection signal with respect to the transmission signal is detected. Since the detected time delay is the time required for the signal to reciprocate between the vehicle and the obstacle, it can be converted into the distance from the vehicle to the obstacle. When the distance is detected for an obstacle,
In other words, once the reflected signal from an obstacle is captured by the search, the device operates to continue capturing the reflected signal from the obstacle. Thus, an obstacle such as a preceding vehicle is tracked, and the inter-vehicle distance is continuously monitored.
Therefore, this type of device is expected to be used as a device for automatically controlling the inter-vehicle distance with a preceding vehicle, that is, as a sensor unit of an inter-vehicle distance control device.

[0003]

However, if the vehicular forward-looking radar device of the above-described principle is simply applied to such an application, there is a problem in how to deal with an interrupted vehicle. That is, according to the principle described above, if a new obstacle, for example, an interrupting car appears at a shorter distance than the preceding vehicle that has been tracked after the tracking operation has begun once, the preceding vehicle that has been tracked up to that point will be used. It is no longer possible to keep track, and the search operation must be started again to catch a new obstacle such as an interrupting vehicle. Since such a search is necessary again, it is difficult to meet the demand for stable and quick control required in applications such as inter-vehicle distance control.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and when a new obstacle appears at a distance closer to the obstacle that has been tracked until then, this new obstacle is created. It is an object of the present invention to speed up the search and tracking.

[0005]

In order to achieve such an object, a warning method according to the present invention transmits a transmission signal having a predetermined configuration to the front of a vehicle in which the vehicle is mounted, and exists in front of the vehicle. The presence or absence of a reflected signal from an obstacle is within a predetermined search range, and the approximate distance from the vehicle to the obstacle is obtained based on the time delay of the reflected signal with respect to the transmission signal,
When the search is performed and the approximate distance is obtained, the search is repeatedly performed while setting the search range so as to search only a range closer to the approximate distance as viewed from the vehicle, and the search is performed in parallel with the search. It is characterized by detecting a precise distance from a vehicle to an obstacle by tracking a reflection signal from the obstacle based on the approximate distance.

Further, in the alerting method of the present invention, when searching for a reflected signal, a search signal having the same configuration as the transmission signal is generated, and a correlation value between the received reflected signal and the generated search signal is obtained. The phase difference of the search signal with respect to the transmission signal is sequentially increased within a predetermined search range so that the correlation value increases to a predetermined value or more, and the phase difference between the search signal and the search signal at the time when the correlation value increases to the predetermined value or more is controlled. It is characterized in that a phase difference of a signal is detected as an approximate distance.

According to the alerting method of the present invention, when tracking a reflected signal from an obstacle, a tracking signal having a configuration corresponding to a transmission signal is generated, and a correlation value between the received reflected signal and the generated tracking signal is generated. Is calculated, and the phase difference of the tracking signal with respect to the transmission signal is gradually increased / decreased based on the phase difference corresponding to the approximate distance so that the correlation value becomes a predetermined value. A phase difference between a tracking signal and a transmission signal is detected as a precise distance.

[0010] In the alerting method according to the present invention, the transmission signal is modulated by a code composed of a plurality of chips, and the tracking signal has the same configuration as the transmission signal.
, A second tracking signal delayed within two chip lengths with respect to the first tracking signal, the product of the received reflected signal and the first tracking signal, and the reflected signal And the second tracking signal are obtained, and the phase difference of the first tracking signal with respect to the transmission signal is gradually increased / decreased with reference to the phase difference corresponding to the approximate distance, thereby obtaining the two types of obtained. Tracking is performed on the reflected signal from the obstacle so that the tracking error, which is the difference between the products, becomes 0. When the sum of the two types of products obtained is equal to or smaller than a predetermined value, it is regarded that the obstacle is not being tracked, and the tracking process is performed. Is stopped.

The forward warning radar apparatus for a vehicle according to the present invention provides a transmission pseudo noise (Pseudo Noi
(se: PN) code, a transmitting means for transmitting a signal phase-modulated by the code to the front of the vehicle, a receiving means for receiving a signal arriving from the front of the vehicle, and a search means having the same configuration as the transmission PN code. A search channel for generating a PN code in a phase controllable manner and calculating and demodulating a product of the search PN code and a received signal, and a tracking PN code having a configuration corresponding to the transmission PN code to be phase controllable. Raise,
While controlling the tracking channel for calculating and demodulating the product of the tracking PN code and the received signal, and controlling the phases of the search PN code and the tracking PN code, the product value obtained by the search channel and the tracking channel is A control arithmetic unit that calculates the distance from the vehicle to the obstacle based on the search PN code so that the phase difference with the transmission PN code sequentially increases within a predetermined search range. Controlling, calculating the correlation value between the received signal and the search PN code by integrating the product obtained by the search channel, and determining the threshold value of the calculated correlation value to determine the approximate distance from the vehicle to the obstacle. And calculating the approximate distance from the vehicle to the obstacle while setting the search range based on the approximate distance obtained by the calculation so that a range closer to the approximate distance as viewed from the vehicle is searched. The phase of the tracking PN code is controlled so that the phase difference between the transmission PN code and the transmission PN code gradually increases / decreases in the vicinity of the phase difference corresponding to the approximate distance in parallel with the calculation of the approximate distance from the vehicle to the obstacle. By calculating the correlation value between the received signal and the tracking PN code by integrating the product obtained by the tracking channel, and determining the calculated correlation value as a threshold value, the precise distance from the vehicle to the obstacle can be calculated. The operation is performed.

[0010]

According to the alerting method of the present invention, first, a transmission signal having a predetermined configuration is transmitted in front of a vehicle on which the vehicle is mounted. When there is an obstacle such as a preceding vehicle ahead of the vehicle, the transmission signal is reflected by the obstacle. The time from transmitting the transmission signal to receiving the reflection signal, that is, the time delay of the reflection signal with respect to the transmission signal, is the time required for the signal to reciprocate between the vehicle and the obstacle, and hence the distance from the vehicle to the obstacle. Since it corresponds to the distance, the distance from the vehicle to the obstacle can be continuously obtained by detecting the time delay by searching for the reflected signal from the received signal and tracking the reflected signal.

In the present invention, the search and the tracking are executed in parallel. That is, first, the presence or absence of a reflected signal from an obstacle existing in front of the vehicle is executed within a predetermined search range. This search is performed so that the approximate distance from the vehicle to the obstacle is obtained. When the approximate distance is obtained based on the time delay of the reflected signal with respect to the transmission signal in the search, tracking is started based on the obtained approximate distance, and a search for a new obstacle is started. A search for a new obstacle is performed in parallel. Specifically, while tracking the reflected signal from the obstacle based on the approximate distance obtained by the search, the precise distance from the vehicle to the obstacle is detected, but only the range closer than the obtained approximate distance is searched. The search range is set to perform the search, and the search is executed in parallel with the tracking. By such processing, in the present invention, for example, when an obstacle such as a preceding vehicle is captured by searching and the vehicle shifts to tracking, other obstacles such as an interrupting vehicle that may appear at a shorter distance than the obstacle are detected. Since the search for the obstacle is performed in parallel with the tracking, it is possible to quickly search for the interrupting vehicle and shift to the tracking. For example, automatic control of the following distance can be stabilized and speeded up.

Further, the alerting method of the present invention can be realized by performing a correlation operation.

First, the search processing can be realized by controlling the phase of the search signal having the same configuration as the transmission signal. First, a search signal is generated, and a correlation value between the received reflected signal and the search signal is obtained. The received reflected signal includes a transmission signal having the same configuration as the search signal, and this signal has a time delay corresponding to the distance between the vehicle and the obstacle with respect to the transmission signal. . Therefore, as a result of controlling the phase of the search signal, as the phase difference between the search signal and the transmission signal approaches the phase difference corresponding to the time delay, the correlation value between the reflection signal and the search signal increases. In the present invention, the phase difference of the search signal with respect to the transmission signal is sequentially controlled to increase within a predetermined search range, and the phase difference of the search signal with respect to the transmission signal at the time when the correlation value increases to a predetermined value or more is approximately equal to the distance. Is detected as Therefore, the search processing can be realized, for example, as a correlation operation of a PN code.

The tracking processing can be realized by controlling the phase of a tracking signal having a configuration corresponding to the transmission signal. First, a tracking signal is generated, and a correlation value between the received reflected signal and the generated tracking signal is obtained. Further, the phase difference between the tracking signal and the transmission signal is controlled to be gradually increased / decreased so that the correlation value becomes a predetermined value. At this time, the reference of the control of the phase difference is the phase difference corresponding to the approximate distance. That is, the tracking processing is performed using the approximate distance detected in the search processing. As a result of the step-up / step-down control, the phase difference between the tracking signal and the transmission signal when the correlation value becomes a predetermined value is detected as a precise distance. Therefore, the tracking processing can also be realized, for example, as a PN code correlation operation.

Further, by using the following two kinds of signals as tracking signals and using the difference and the sum of the product with the received signal, it is possible to detect a precise distance in a suitable manner, and to determine whether or not a tracking state exists. Can be suitably determined. That is, a first tracking signal having the same configuration as the transmission signal and a second tracking signal delayed by less than 2 chips from the signal are prepared, and the product of the received reflected signal and Obtained for each tracking signal. Further, a difference and a sum of the obtained two types of products are calculated. Since the phase difference between the two types of tracking signals is within two chip lengths, the difference between the products always becomes 0 at one point near the phase difference corresponding to the approximate distance obtained by the search. The sum always becomes non-zero in a certain range including the point where the value difference becomes zero. Therefore, by gradually increasing / decreasing the phase difference of the tracking signal so that the difference between the obtained two types of products becomes zero, it is possible to accurately track the reflected signal from the obstacle, and to calculate the product of the two types of products. When the sum is equal to or less than the predetermined value, it is considered that the obstacle is not being tracked, and the tracking process can be stopped. If necessary, a no-signal warning display can be performed.

Such an alerting method can be realized by using a spread spectrum method. The vehicular forward-looking radar device of the present invention is such an embodiment. That is, a signal phase-modulated by the transmission PN code having a predetermined configuration is transmitted by the transmitting unit to the front of the vehicle on which the vehicle is mounted, and the receiving unit receives a signal arriving from the front of the vehicle. The search processing is realized by the cooperation of the search channel and the control arithmetic unit, and the tracking processing is realized by the cooperation of the tracking channel and the control arithmetic unit.

Specifically, the search channel generates a search PN code under the control of the control arithmetic unit so that the phase difference from the transmission PN code sequentially increases within a predetermined search range. The product of the PN code and the received signal is calculated and demodulated. Since the search PN code has the same configuration as the transmission PN code, a correlation value between the received signal and the search PN code can be obtained by integrating the product obtained by the search channel. The control calculator performs such a correlation calculation, and further determines the approximate distance from the vehicle to the obstacle by determining the calculated correlation value as a threshold value. The control calculator generates the tracking PN code while controlling the tracking channel such that the phase difference with the transmission PN code gradually increases / decreases in the vicinity of the phase difference corresponding to the obtained approximate distance. The tracking channel calculates and demodulates the product of the tracking PN code and the received signal. The tracking PN code has a configuration corresponding to the transmission PN code, and a correlation value between the received signal and the tracking PN code can be obtained by integrating the product obtained by the tracking channel. The control computing unit determines the calculated correlation value as a threshold value,
For example, the tracking value is compared with a correlation value indicating a tracking state is equal to or more than a predetermined value and the tracking value is checked while the correlation value indicating the tracking error is compared with 0 to suppress and control the tracking error. Calculate the precise distance from the obstacle to the obstacle. In parallel with the tracking processing, the control computing unit sets a search range based on the approximate distance obtained by the calculation, and repeatedly executes the search processing so that a range closer to the approximate distance as viewed from the vehicle is searched. .

Therefore, in the forward warning radar apparatus for a vehicle according to the present invention, the warning method according to the present invention is realized by using the spread spectrum method. Further, the sharing method of the search channel and the tracking channel realizes the alerting method of the present invention with a simple circuit configuration and a logical configuration.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a vehicular forward warning radar device according to an embodiment of the present invention. This embodiment has a configuration in which the present invention is realized using a spread spectrum system. The spread spectrum system used in this embodiment is a so-called direct spread system, in which a carrier is phase-modulated by a PN code, which is a predetermined code sequence, and transmitted.
The received signal is despread by the PN code.

The PN generator 11 generates a PN code used for phase modulation of a carrier wave, that is, a PN code for transmission. As the transmission PN code, for example, an M-sequence code string or the like can be used. The transmitter 12 phase-modulates a carrier having a predetermined frequency with the transmission PN code,
Thereby, a transmission signal is generated. The transmission signal is wirelessly transmitted by the transmitting antenna 13.

The transmitting antenna 13 is provided, for example, at the front of the vehicle, and transmits a transmission signal toward the front of the vehicle. When an obstacle such as a preceding vehicle exists in front of the vehicle, this transmission signal is reflected by the obstacle. A receiving antenna 21 is provided, for example, at the front of the vehicle, and the reflected signal is received by the receiving antenna 21. Receiver 22
Amplifies the signal received by the receiving antenna 21 and outputs it to the search channel 3 and the tracking channel 4. The transmitting antenna 13 and the receiving antenna 21 may be shared by using an antenna duplexer.

The search channel 3 searches under the control of the control calculator 51 to determine whether or not the received signal output from the receiver 22 includes a reflected signal from an obstacle. In this search, the search channel 3 generates a search PN code, despreads the received signal using the search PN code,
The control calculator 51 executes a correlation calculation. To realize such a function, the search channel 3 includes a product calculator 31, a demodulator 32, a PN generator 33, and a phase controller 34.

The received signal output from the receiver 22 and the search PN code generated by the PN generator 33 are input to the product calculator 31. The search PN code is the transmission PN
This is the same code string as the code. The phase is controlled by the phase controller 34 based on the phase of the transmission PN code. The phase controller 34 controls the phase of the search PN code based on the phase information supplied from the control calculator 51.
Therefore, under the control of the control calculator 51, the phase of the search PN code is controlled. The product calculator 31 calculates the product of the received signal output from the receiver 22 and the search PN code, and the demodulator 32 demodulates the output of the product calculator 31. The result of the demodulation is supplied to the control calculator 51.

The control calculator 51 controls the phase of the search PN code via the phase controller 34. The control of the phase of the search PN code is executed such that the reflected signal (obstacle) is searched in the order from a point near the vehicle to be mounted to a distant place. That is, when the epoch lengths of the transmission PN code and the search PN code are te, the phase of the search PN code is controlled to be gradually delayed with respect to the transmission PN code. Further, the range of the phase control, that is, the search range is set at a maximum to a distance corresponding to the epoch length te. As will be described later, the search range is reduced and set at the start of tracking for the purpose of searching for an interrupted vehicle.

On the other hand, the control calculator 51 receives the output of the search channel 3, that is, the demodulated output of the demodulator 32. The control calculator 51 calculates a correlation value between the received signal and the search PN code by accumulating (integrating) the demodulated output of the demodulator 32 for a predetermined time, for example, an integral multiple of the epoch. The control calculator 51 detects the presence of an obstacle in front of the vehicle and the approximate distance from the vehicle to the obstacle by determining the correlation value obtained by the calculation as a threshold value. The control computing unit 51 supplies information indicating the presence or absence of an obstacle to a vehicle-mounted display or various control devices, and supplies phase information corresponding to the approximate distance to the phase controller 49 of the tracking channel 4.

FIGS. 2A to 2E show the principle of obstacle search in this embodiment.

First, as shown in FIG. 2A, a transmission signal is modulated by a transmission PN code having a predetermined epoch length te. The transmission PN code is a code string that repeats in epochs. If an obstacle exists in front of the vehicle, the transmission signal is reflected by the obstacle. At this time, the reception signal received by the reception antenna 21 is a signal as shown in FIG. That is, the signal is delayed with respect to the transmission signal.

The time delay td corresponding to this delay corresponds to the time that the radio wave travels from the transmitting antenna 13 to the receiving antenna 21 via an obstacle. By sequentially increasing the phase of the search PN code as described above, this time delay t
d can be detected. That is, when the phase of the search PN code is controlled to increase so that the phase difference with respect to the transmission PN code ranges from 0 to the epoch length te, the transmission PN code is increased.
The phase difference of the search PN code with respect to the code approaches the time delay td as shown in FIG. As described above, when the phase difference between the search PN code and the transmission PN code approaches the time delay td, the correlation value increases. The control calculator 51 compares the correlation value with a predetermined threshold value as shown in FIG. 2D, and detects the phase td1 of the search PN code at the time when the correlation value is exceeded (the search for the transmission PN code). PN code phase difference). This phase td1 substantially coincides with the time delay td. The control calculator 51 multiplies this phase td1 by c / 2 to detect the approximate distance from the vehicle to the obstacle. In addition,
c is the speed of the radio wave.

The approximate distance (phase td1) detected by such an operation exactly corresponds to the point X shown in FIG. In FIG. 2E, the horizontal axis represents the phase td1, and the vertical axis represents the product of the received signal and the search PN code.

As the phase td1 of the search PN code is controlled to increase, the product of the received signal and the search PN code becomes td-1.
The value becomes 0 up to the chip point, starts to increase linearly from the point of td-1 chip, reaches a maximum at a phase corresponding to the time delay td, and becomes 0 after the point of td + 1 chip. This relationship is clear from the nature of the PN code. Therefore, the correlation value, which is the integral value of the product of the received signal and the search PN code, is calculated by the above-described increase control to the point of td-1 chip and the time delay td
The threshold is reached at point X, which lies between the considerable points. From this relationship, the true distance (the phase of the point corresponding to the time delay td)
Is the approximate distance (phase td) detected by the above operation.
From 1), it can be seen that it exists within one chip.

The search channel 3 and the control arithmetic unit 51 execute a search for an obstacle based on such a principle, and obtain the approximate distance. The device of the present embodiment further has a function of tracking an obstacle using the approximate distance obtained as a result of the search. In the present embodiment, the tracking of the obstacle is executed in parallel with the search for the interrupting vehicle and the like. Tracking channel 4
Implements a function of tracking an obstacle captured by the search together with the control arithmetic unit 51. The tracking channel 4 is composed of product calculators 41 and 43, demodulators 42 and 44,
5, an adder 46, a PN generator 47, a delay unit 48, and a phase controller 49.

The product calculator 41 receives the received signal output from the receiver 22 and the tracking PN code generated by the PN generator 47, and calculates the product of the two. Tracking PN
The code is the same code sequence as the transmission PN code, and its phase is determined based on the phase of the transmission PN code.
Is controlled by The control computing unit 51 includes a phase controller 49
To control the phase of the tracking PN code. The product calculated by the product calculator 41 is supplied to a demodulator 42, which demodulates the product.

The product calculator 43 receives the received signal output from the receiver 22 and the tracking PN delayed by the delay unit 48.
Input the sign and calculate the product of both. The delay unit 48
The tracking PN code generated by the N generator 47 is delayed by one chip. Here, the chip is the minimum unit constituting the epoch. The product calculated by the product calculator 43 is supplied to a demodulator 44, which demodulates the product. The subtracter 45 generates a tracking error output ε by subtracting the output of the demodulator 44 from the output of the demodulator 42, and supplies the tracking error output ε to the control calculator 51. The adder 46 adds the output of the demodulator 44 to the output of the demodulator 44 to output the tracking state output es.
Is generated and supplied to the control calculator 51.

The control calculator 51 controls the phase td2 of the tracking PN code (the phase difference of the tracking PN code with respect to the transmission PN code) based on the approximate distance of the obstacle detected from the output of the search channel 3, and performs tracking. The tracking error output ε and the tracking state output es are input from the channel 4. Control calculator 51
Integrates the tracking error output ε and integrates the tracking error output ε based on the integrated value obtained as a result of integration of the tracking state output es and the integrated value obtained as a result.
The phase td2 of the N code is controlled. As a result, when the integrated value of the tracking error output ε becomes 0, the tracking P
The precise distance from the vehicle to the obstacle is calculated based on the phase td2 of the N code, and is output to an onboard display and various control devices. The control calculator 51 causes the search channel 3 to execute a search operation in parallel with the control of the tracking channel 4. The search range at that time is set to a range in which the approximate distance obtained by the previous search is the maximum distance.

FIGS. 2F and 2G show the principle of tracking in this embodiment. The horizontal axis of these figures is the phase td2 of the tracking PN code, and the vertical axis is the tracking error output ε and the tracking state output es, respectively.

First, assuming that there is no product calculator 43, demodulator 44, subtractor 45, adder 46 and delay unit 48, the product of the received signal and the tracking PN code in that case is shown in FIG.
As shown by P in FIG. 2 (f), it changes with the same tendency as in FIG. 2 (e). Next, assuming that the product calculator 41, the demodulator 42, the subtractor 45, and the adder 46 do not exist, the product of the received signal and the tracking PN code in that case is indicated by Q in FIG. P is delayed by one chip. As is clear from these, the tracking error output ε obtained by subtracting the output of the demodulator 44 from the output of the demodulator 42 by the subtractor 45 has the content indicated by PQ in FIG. . The tracking state output es obtained by adding the output of the demodulator 44 to the output of the demodulator 42 by the adder 46 has the content indicated by P + Q in FIG.

The tracking error output ε is calculated from td-1 chip to t
Up to d, the same value as P, and td + 1 chip to td +
Up to two chips, Q is a value obtained by inverting the sign. td to t
Up to d + 1, it decreases linearly with a gradient twice that of P, and becomes 0 at the point O of td-1 / 2 chip. The tracking state output es has the same value as P from td-1 chip to td, and the same value as Q from td + 1 chip to td + 2 chip. It takes a positive constant value from td to td + 1.

In this embodiment, when an obstacle is captured by the control of the search channel 3 and its approximate distance is obtained,
The control computing unit 51 controls the phase td2 of the tracking PN code so that the phase is in accordance with the approximate distance. Since the point at which the correlation value obtained based on the output of the search channel 3 exceeds the threshold value is the X point as described above, the phase td2 of the tracking PN code is controlled at the X point. Then, the tracking error output ε takes a positive value. Further, the tracking state output es has a value other than 0.

The control calculator 51 accumulates (integrates) the tracking error output ε and the tracking state output es for a period sufficiently longer than the epoch length te. In the state where the phase td2 of the tracking PN code is controlled to the point X, since the integrated value of the tracking error output ε is positive, the control calculator 51 supplies the phase information to the phase controller 49, and A small amount Δ is added to the phase td2 of the PN code to delay the phase (gradual increase control of the phase td2). This minute amount Δ is set sufficiently smaller than the chip length. For example, if the integrated value of the tracking error output ε is still positive after the addition, the control calculator 51 further adds a small amount Δ to the phase td2 of the tracking PN code. This addition is performed until the integrated value of the tracking error output ε becomes zero. When the integration value of the tracking error output ε becomes negative after passing the point O as a result of the addition, the control calculator 51 calculates the phase td2 of the tracking PN code.
, A small amount Δ is subtracted from the control value (gradual decrease control of the phase td2). By such a gradual increase / decrease control, the phase td2 of the tracking PN code is controlled to be the point O.

The phase td2 of the tracking PN code at point O
Is a value obtained by adding 1/2 chip to the time delay td. The control calculator 51 multiplies this phase td2 by c / 2. Thereby, the distance to the obstacle can be precisely obtained. When the distance to the obstacle fluctuates while the obstacle is being captured by the tracking channel 4 (that is, the phase td2 of the tracking PN code is in the range of td-1 chip to td + 1 chip), The obstacle can be tracked by the gradually increasing / decreasing control of. That is, when the integrated value of the tracking error output ε changes from 0 to a positive value due to the approach of an obstacle, the phase td2 is gradually increased, and conversely, when the integrated value of the tracking error output ε changes to a negative value due to the separation, the phase td2 is changed. Gradual decrease control is performed.

Further, the control calculator 51 outputs a tracking state output e.
The gradual increase / decrease control of the phase td2 of the tracking PN code is executed while confirming that the integral value of s is equal to or greater than a predetermined value.
That is, when the integrated value of the tracking state output es is equal to or less than the predetermined value, the phase td2 of the tracking PN code is out of the range near td, and the reflected signal from the obstacle is not captured. In this case, the tracking operation is stopped. In addition, a warning indicating that there is no signal can be displayed if necessary. When the integrated value of the tracking state output es is equal to or greater than a predetermined value, the reflected signal from the obstacle is in a captured state, and accordingly, the gradually increasing / decreasing control of the phase td2 of the tracking PN code is appropriately performed. I do.

Such a tracking operation by the tracking channel 4 and the control calculator 51 is executed in parallel with the search operation by the search channel 3 and the control calculator 51. For example, immediately after the power is turned on to the apparatus, first, the search range is set to the epoch length te, and then the search channel 3 and the control arithmetic unit 51 search for an obstacle. When the distance is detected, the control calculator 51 causes the tracking channel 4 to track the obstacle (for example, the preceding vehicle) using the result. The control calculator 51 is
When the tracking operation is started, the search range is set to a phase corresponding to the approximate distance of the preceding vehicle, and then the search channel 3 searches for another obstacle. In this case, since the search range is set to a range closer to the preceding vehicle, the search target is an object appearing at a closer distance, such as an interrupting vehicle. In this state, therefore, the search for the interrupting vehicle is performed while tracking the preceding vehicle, for example. When the interrupted vehicle is captured by the search, tracking of the interrupted vehicle and search for an obstacle located at a shorter distance than the interrupted vehicle are started.

FIG. 3 shows a flow of the operation of the control arithmetic unit 51 in this embodiment. As shown in this figure, the control calculator 51 first executes an obstacle search operation immediately after turning on the power.

Immediately after the power is turned on, first, the tracking P
After setting the epoch length te in the phase td2 of the N code and 0 in the phase td1 of the search PN code, (10
1, 102), an obstacle search is performed. Step 102
The setting of the phase td1 in means that the search is started from a point closest to the vehicle to be mounted. Since the phase td2 of the tracking PN code is used as information indicating the search range in step 104, setting the phase td2 in step 101 is equivalent to setting the search range (the maximum distance to be searched). I do.

In the obstacle search operation, first, a small amount Δ is added to the phase td1 of the search PN code (10).
3). The control computing unit 51 uses the search PN based on the addition result.
The code phase td1 is controlled, and a correlation value (a value obtained by integrating the output of the demodulator 32) obtained as a result of the control is compared with a predetermined threshold value. If the correlation value has not reached the threshold value, it is determined that an obstacle has not been captured, and the process returns to step 103. That is, the phase td of the search PN code
1 is increased and the search is continuously executed. If no obstacle exists within the search range in front of the vehicle, the phase td1 of the search PN code indicates the tracking PN indicating the search range.
The condition of step 105 is not satisfied even when the phase of the code reaches td2. When the phase td1 becomes equal to or greater than the phase td2, the process returns to step 102, where the phase td1 is reset to 0,
The search operation is started again.

When the condition of step 105 is satisfied at a certain phase td1, the control computing unit 51 first sets the search P
The phase td1 of the N code is set to the phase td2 of the tracking PN code (106). As described above, the phase td2 of the tracking PN code defines the search range.
At 06, the search range is set to a distance range closer to the previously captured obstacle. At the same time, this step 106
In the subsequently executed obstacle tracking operation, the tracking PN
This corresponds to determining the starting point of the code phase control. After the execution of step 106, the process returns to step 102 to execute the obstacle search, and the obstacle tracking operation from step 201 is executed. This obstacle search is a search at a distance shorter than the previously captured obstacle, for example, a search for an interrupting vehicle. The search for the interrupting vehicle and the tracking of the obstacle (preceding vehicle) are performed in parallel.

In step 201, the control arithmetic unit 5
1 inputs the tracking error output ε from the tracking channel 4 and integrates it, and compares the integrated value with 0. As described above, immediately after the start of the obstacle tracking operation, the integral value becomes positive. Therefore, the process proceeds to step 203, and the minute amount Δ is added to the phase td2. By repeating steps 201 and 203, the phase td2 of the tracking PN code is delayed. When the integral value becomes negative, the process proceeds to step 204, where a minute amount Δ is subtracted from the phase td2. Step 20
By repeating steps 1 and 204, the phase td2 of the tracking PN code advances. With such control, at some point, the integral value becomes 0, and step 205 is executed via step 202.

In step 205, the tracking state output es at the phase td2 at which the integrated value of the tracking error output ε becomes 0
It is determined whether or not the integrated value of is equal to or greater than a predetermined value es0. If this determination is made, since the vehicle is in the tracking state, the precise distance is calculated based on the phase td2 (206), and the result is output. After execution of step 206, the process returns to step 201, and obstacle tracking is executed. In addition, the integrated value of the tracking state output es becomes a predetermined value es due to the appearance of an interrupting vehicle or the like.
If the value is less than 0, the obstacle tracking operation ends and waits until an obstacle search result is obtained.

With such an operation, in this embodiment, a search for an interrupting vehicle or the like can be executed without interrupting the tracking. For example, when the vehicle is used as an inter-vehicle distance control sensor, a new obstacle can be quickly detected. It can detect and realize vehicle speed control. Further, a relatively simple device configuration is sufficient.

[0051]

As described above, according to the alerting method of the present invention, first, a search is performed to detect the approximate distance of an obstacle, and tracking of the obstacle is executed based on the detected approximate distance. In parallel, a search for a distance closer to this obstacle is performed, so that, for example, another obstacle such as an interrupting vehicle that may appear at a distance closer to this obstacle while tracking an obstacle such as a preceding vehicle. Can be searched quickly. Therefore, for example, automatic control of the inter-vehicle distance can be stabilized and speeded up.

According to the alerting method of the present invention, the search processing is performed using the phase control of the search signal having the same configuration as the transmission signal, and the phase control of the tracking signal having the configuration corresponding to the transmission signal is performed. Since the tracking processes are respectively executed using these methods, these processes can be realized using, for example, a spread spectrum method.

Further, according to the alerting method of the present invention, two types of signals having a predetermined phase relationship are used as tracking signals, so that a precise distance can be suitably detected, and whether or not tracking is possible. It is possible to suitably determine whether or not.

According to the vehicular forward-looking radar device of the present invention, by using the search channel, the tracking channel, and the control arithmetic unit that controls these, the vigilance method of the present invention can be realized using a spread spectrum system. .
Further, the device configuration and the logical configuration are relatively simple.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a vehicular forward warning radar device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the principle of search and tracking in this embodiment.

FIG. 3 is a diagram showing a flow of an operation of a control arithmetic unit in this embodiment.

[Explanation of symbols]

Reference Signs List 3 search channel 4 tracking channel 11, 33, 47 PN generator 12 transmitter 13 transmitting antenna 21 receiving antenna 22 receiver 31, 41, 43 product calculator 32, 42, 44 demodulator 34, 49 phase controller 45 Subtractor 46 Adder 48 Delayer 51 Control calculator te Epoch length td Time delay of received signal (reflected signal) with respect to transmission signal td1 Phase of search PN code td2 Phase of tracking PN code Δ Small amount ε Tracking error output es Tracking state output es0 Judgment threshold of integrated value of tracking state output

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (5)

(57) [Claims] 1. A transmission signal having a predetermined configuration is transmitted in front of a vehicle on which the vehicle is mounted, and the presence or absence of a reflected signal from an obstacle existing in front of the vehicle is searched for within a predetermined search range. In a warning method for detecting the distance from a vehicle to an obstacle based on a time delay of the reflected signal with respect to the transmission signal when the reflected signal is detected, a search for the reflected signal is performed so that an approximate distance from the vehicle to the obstacle is obtained. When the distance is obtained, the search is repeatedly performed while setting the search range so as to search only a range closer to the approximate distance as viewed from the vehicle, and in parallel with the search, based on the obtained approximate distance. A warning method characterized by detecting a precise distance from a vehicle to an obstacle by tracking a reflected signal from the obstacle. 2. The alerting method according to claim 1, wherein when searching for a reflected signal, a search signal having the same configuration as a transmission signal is generated, and a correlation value between the received reflected signal and the generated search signal is generated. The phase difference of the search signal with respect to the transmission signal is controlled to increase sequentially within a predetermined search range so that the correlation value increases to a predetermined value or more. A warning method characterized by detecting a phase difference of a search signal as an approximate distance. 3. The alerting method according to claim 1, wherein when tracking a reflected signal from an obstacle, a tracking signal having a configuration corresponding to the transmission signal is generated and the received reflected signal is generated. A correlation value of the tracking signal is obtained, and a phase difference of the tracking signal with respect to the transmission signal is gradually increased / decreased based on the phase difference corresponding to the approximate distance so that the correlation value becomes a predetermined value. A warning method characterized by detecting, as a precise distance, a phase difference between a tracking signal and a transmission signal at the time when the following condition is satisfied. 4. The alerting method according to claim 3, wherein the transmission signal is modulated by a code composed of a plurality of chips, and the tracking signal has the same configuration as the transmission signal. And a second tracking signal delayed within two chip lengths with respect to the first tracking signal. The product of the received reflected signal and the first tracking signal, and the reflected signal and the second The product of the tracking signals is obtained, and the phase difference of the first tracking signal with respect to the transmission signal is gradually increased / decreased with reference to the phase difference corresponding to the approximate distance. Tracking the reflected signal from an obstacle so that a certain tracking error becomes 0, and if the sum of the obtained two types of products is less than a predetermined value, consider that the obstacle is not being tracked and stop the tracking process. An alert method characterized by the following. 5. A transmitting means for transmitting a signal phase-modulated by a pseudo-noise code for transmission having a predetermined configuration to the front of a mounted vehicle, a receiving means for receiving a signal arriving from the front of the vehicle, A search channel for generating a search pseudo-noise code having the same configuration as the pseudo-noise code in a phase controllable manner, and calculating and demodulating a product of the search pseudo-noise code and a received signal; and a transmission pseudo-noise code. A tracking channel for generating a tracking pseudo-noise code having a corresponding configuration in a phase controllable manner, and calculating and demodulating a product of the tracking pseudo-noise code and a received signal; a search pseudo-noise code and a tracking pseudo-noise code A control operation unit that controls the phase of the code, and calculates the distance from the vehicle to the obstacle based on the product value obtained by the search channel and the tracking channel. The receiver controls the phase of the pseudo-noise code for search so that the phase difference with the pseudo-noise code for transmission sequentially increases within a predetermined search range, and integrates the product obtained by the search channel with the received signal and the search signal. By calculating the correlation value of the pseudo-noise code for use and determining the calculated correlation value as a threshold value, the approximate distance from the vehicle to the obstacle is calculated, and a range closer to the approximate distance from the vehicle is searched. Thus, while setting the search range based on the approximate distance obtained by the calculation, the calculation of the approximate distance from the vehicle to the obstacle is repeatedly executed, and the calculation of the approximate distance from the vehicle to the obstacle is performed in parallel with the calculation of the approximate distance from the vehicle. The phase of the tracking pseudo-noise code is controlled so that the phase difference from the pseudo-noise code gradually increases / decreases in the vicinity of the phase difference corresponding to the approximate distance, and the reception is performed by integrating the product obtained by the tracking channel. Calculating a correlation value between the detected signal and the tracking pseudo-noise code, and determining a threshold value of the calculated correlation value to calculate a precise distance from the vehicle to the obstacle. .