JPH07280940A - Vehicle radar device - Google Patents

Abstract

PURPOSE:To obtain a radar for vehicle which enables highly accurate detection of a distance to a reflector and reduction in errors of detected distance regard less of the size of a reflection factor of the reflector. CONSTITUTION:Electromagnetic wave transmitted from a transmitting circuit 4 to be reflected on a reflector 5 is received by a receiving circuit 23 to be stored into a reflection waveform memory 24 having address. When the reflection waveform is used at a waveform data processing section 25 to calculate the time until the electromagnetic wave is transmitted from a transmitting circuit 4 and received by a receiving circuit 23, the address of the reflectmon waveform memory 24 is used. An average noise level is calculated from the reflection waveform and a rising part of the reflection waveform is approximated by an approximate wave form generation means to generate an approximate waveform. An intersection between the approximate waveform and the average noise level is defined as rising point by a distance calculation means to calculate the distance to the reflector 5 using the position of rising point at a certain time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle radar device, and more particularly to a device for detecting a moving or stationary reflector and measuring its distance by utilizing electromagnetic waves.

[0002]

2. Description of the Related Art As a conventional device of this type, an infrared tracking sensor for detecting a moving or stationary target object and measuring its distance by utilizing light in the infrared wavelength range is disclosed in Japanese Patent Laid-Open No. 59-59-59. It is described as a conventional device in Japanese Patent Publication No. 79173. FIG. 17 is a block diagram showing this infrared tracking sensor. In the figure, 1 is a trigger signal generating circuit, 2 is a drive circuit for generating electric pulses, and 3 is a laser diode (Laser Diode) for converting electric pulses into optical pulses.
e; hereinafter referred to as LD) 4 is a transmission circuit composed of the drive circuit 2 and the LD 3, and transmits an optical pulse to the reflector 5. 6
Is a photodiode (Photo Diode; hereinafter referred to as PD) for converting an optical pulse into an electric pulse, and 7 is P
An amplifier circuit for electrically amplifying the output of D6, 8 is a reference voltage generating circuit, 9 is a comparator, 10 is a counter for counting at a constant count interval, and 11 is a distance calculating circuit.

Next, the operation will be described. The trigger signal generation circuit 1 supplies a signal to start transmission to the drive circuit 2 of the transmission circuit 4 and a signal to start counting (start signal) to the counter 10. The drive circuit 2 receives the signal for starting transmission and generates an electric pulse. This electric pulse is converted into an optical pulse by the LD 3 and projected on the reflector 5. The optical pulse reflected by the reflector 5 is converted into an electric pulse by the PD 6, and is normally linearly amplified by the amplifier circuit 7 to be a reflected signal.

The reference voltage generating circuit 8 generates, for example, (output voltage value of the amplifier circuit 7 when there is no signal) + (constant voltage value) as a threshold value, and the comparator 9 generates the reflected signal and the threshold value. Compare. For example, when the reflection signal ≧ threshold, it is judged that the reflected light from the reflector 5 is received, and the comparison result “1” is output. When the reflection signal <threshold, the reflected light from the reflector 5 Is judged not to be received and the comparison result "0" is output. The counter 10 recognizes the comparison result "1" as a stop signal. In the counter 10, the trigger signal generation circuit 1
Counting is started by the start signal generated in step 1, and counting is performed at a constant count interval, for example, at 100 nsec intervals when an external clock (not shown) of 10 MHz is used.
Then, the counting is ended by the stop signal from the comparator 9, and the count value is output. As a result, the time from the transmission of the optical pulse from the transmission circuit 4 to the reception of the reflected light can be measured. The distance calculation circuit 11 calculates the distance (R) from the count value and the count interval to the reflector 5 by the formula 1. Distance (R) = (count value) × (count interval) × C / 2 (1) C: speed of light (3 × 10 ⁸ m / sec)

The problems of the conventional vehicle radar device will be described below. FIG. 18 is a graph showing the waveform of the reflected signal, where the horizontal axis represents time and the vertical axis represents amplitude. In the figure,
A straight line A indicates the threshold level set by the reference voltage generating circuit 8. t0 is the time when the transmission circuit 4 starts transmission. The reflected waveform has a mountain-shaped waveform with an upward convex shape as shown by a curve B or C, and the amplitude changes according to the reflectance of the reflector 5. When the reflector 5 has a high reflectance, the amplitude of the reflected waveform becomes large as shown by the curve B,
When the reflector 5 has a low reflectance, the amplitude of the reflected waveform becomes small as shown by the curve C.

When the reflected waveform has a large amplitude as shown by the curve B, the time position of the point where the value of the reflected signal reaches the threshold level, that is, the intersection of the curve B and the straight line A is t.
It is 1. The counter 10 outputs the count value from t0 to t1 to the distance calculation circuit 11, and the distance calculation circuit 11 uses the count value to calculate the distance (R) to the reflector 5 by Equation 1. When the reflected waveform has a small amplitude as shown by the curve C, the point where the value of the reflected signal reaches the threshold level, that is, the time position of the intersection of the curve C and the straight line A is t2. The counter 10 outputs the count value from t0 to t2 to the distance calculation circuit 11, and the distance calculation circuit 11 calculates the distance (R). in this way,
Due to the difference in the reflectance of the reflector 5, the distance to the reflector 5 was different, and an accurate distance could not be obtained.

Further, in the conventional vehicle radar device, since the range resolution is defined by the count interval of the counter 10,
The resolution of the calculated distance could not be improved. For example, if the count frequency is 10 MHz, the calculation can be made only with a resolution of 15 m. A high-speed counter is necessary to improve the distance resolution, and the high-speed counter is expensive.

[0008]

As described above, in the conventional vehicle radar device, since the reflection signals for the reflectors having the different reflectances at the same distance are different, the obtained reflector 5 is obtained.
There is a problem in that the distance to is different depending on the reflectance.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a radar device for a vehicle capable of accurately calculating the distance to a reflector. Another object of the present invention is to provide a vehicle radar device that can reduce the error in the calculated distance regardless of the reflectance of the reflector. It is another object of the present invention to provide a vehicle radar device that can simplify calculation when performing waveform processing for the above purpose.

[0010]

According to a first aspect of the present invention, there is provided a vehicle radar device, a transmitting means for transmitting an electromagnetic wave, a receiving means for receiving an electromagnetic wave transmitted from the transmitting means and reflected by a reflector, and an address. Waveform storing means for storing the waveform of the reflected signal received by the receiving means as waveform data,
And the time until the electromagnetic wave is transmitted from the transmitting means and received by the receiving means is calculated using the waveform data stored in the waveform storing means, and when calculating the distance from this time to the reflector, the address of the waveform storing means Is provided with a distance calculating means.

According to a second aspect of the present invention, there is provided a vehicular radar apparatus in which transmitting means for transmitting an electromagnetic wave, receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by a reflector, and receiving by the receiving means. Waveform storage means for storing the waveform of the reflected signal as waveform data, average noise level calculation means for calculating an average noise level from the waveform data, and approximate waveform generation for approximating the rising portion of the waveform of the reflected signal to generate an approximate waveform Means and the intersection of the approximate waveform and the average noise level as a rising point, and the time position of this rising point is used to calculate the time from the transmission of the electromagnetic wave to the rising point, and from this time the reflector It is provided with a distance calculation means for calculating the distance to.

In the vehicle radar device according to a third aspect of the present invention, the approximate waveform generating means in the second aspect of the invention is a straight line that includes a point where the slope of the rising portion of the waveform of the reflected signal is maximum. It is characterized in that it approximates and generates an approximate waveform.

According to a fourth aspect of the present invention, in the vehicle radar device according to the second aspect of the invention, the approximate waveform generating means approximates a section of the waveform of the reflected signal including the apex of the convex portion by curve approximation. Is generated.

According to a fifth aspect of the present invention, there is provided a vehicle radar device, which includes transmitting means for transmitting an electromagnetic wave, receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by a reflector, and receiving by the receiving means. Waveform storage means for storing the waveform of the reflected signal as waveform data, apex position calculation means for calculating the temporal position of the apex of the convex portion of the waveform of the reflected signal,
And a distance calculating means for calculating a time from the transmitting means to the apex position after the electromagnetic wave is transmitted using the apex position and calculating a distance from the time to the reflector.

According to a sixth aspect of the present invention, in the vehicle radar device, the waveform storage means according to any one of the second to fifth aspects has an address, and the distance calculation means uses the time difference depending on the address. Is calculated, and the distance from this time to the reflector is calculated.

According to a seventh aspect of the present invention, there is provided a vehicular radar apparatus in which transmitting means for transmitting an electromagnetic wave, receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by a reflector, and electromagnetic wave from the transmitting means. Distance calculation means for calculating the time from transmission to reception by the receiving means, and distance calculating means for calculating the distance to the reflector from this time, vertex level for detecting the level of the apex of the convex portion of the reflected signal received by the receiving means The detection means and the distance correction means for correcting the distance according to the level of the apex are provided.

[0017]

According to the first aspect of the present invention, the waveform data is stored as a digital value in the waveform storage means having an address, and the time until the electromagnetic wave is transmitted from the transmitting means to the receiving means by the distance calculating means. When calculating, the address of the waveform storage means is used.

According to the second aspect of the present invention, the average noise level calculation means calculates the average noise level from the waveform data stored in the waveform storage means, and the approximate waveform generation means approximates the rising portion of the waveform of the reflected signal. To generate an approximate waveform. The distance calculating means sets the intersection of the approximate waveform and the average noise level as a rising point, and calculates the distance to the reflector by using the temporal position of this rising point.

According to a third aspect of the present invention, the approximate waveform generating means according to the second aspect generates an approximate waveform by linearly approximating a section including a point where the slope of the rising portion of the waveform of the reflected signal is maximum. It shall be. The temporal position of the rising point is determined from this approximate waveform.

Further, according to a fourth aspect of the present invention, the approximate waveform generating means in the second aspect generates an approximate waveform by curve-approximating a section including a peak of a convex portion of a waveform of a reflected signal. The temporal position of the rising point is determined from this approximate waveform.

Further, according to a fifth aspect of the present invention, the apex position calculating means calculates the temporal position of the apex of the convex portion of the waveform of the reflection signal, and the distance calculating means uses the apex position to measure the distance to the reflector. To calculate. The temporal position of this apex is almost the same even if the reflectance of the reflector changes.

According to a sixth aspect of the present invention, the waveform storing means in the second to fifth aspects has an address, and the distance calculating means uses the address to transmit the electromagnetic wave from the transmitting means and the receiving means receives the electromagnetic wave. Calculate the time until it is done.

According to a seventh aspect of the present invention, the distance to the reflector is calculated, the vertex level calculating means calculates the level of the apex of the convex portion of the waveform of the reflection signal, and the distance correcting means calculates the apex of the apex. Correct the distance according to the level.

[0024]

【Example】

Example 1. Hereinafter, a vehicle radar device according to a first embodiment of the present invention will be described. FIG. 1 is a configuration diagram showing a vehicle radar device according to a first embodiment. In the figure, the transmission circuit 4 constitutes an electromagnetic wave transmission means for transmitting an electromagnetic wave.
Further, 21 is a logarithmic amplifier circuit, 22 is an A / D converter for converting an analog signal into a digital signal, and 23 is a PD 6,
The reflected signal receiving circuit having the logarithmic amplifier circuit 21 and the A / D converter 22 constitutes an electromagnetic wave receiving means for receiving the electromagnetic wave reflected by the reflector 5. Reference numeral 24 is a waveform storage means for storing the waveform of the reflected signal, which is composed of, for example, a reflected waveform memory.

Next, the operation will be described. As before,
The trigger signal generating circuit 1 gives a signal for starting transmission to the drive circuit 2 of the transmitting circuit 4, and also gives a signal for starting conversion (start signal) to the A / D converter 22. The drive circuit 2 receives the signal for starting transmission and generates an electric pulse. This electric pulse is converted into an optical pulse by the LD 3 and projected on the reflector 5. The optical pulse reflected by the reflector 5 is received by the reflected signal receiving circuit 23. Reflection signal receiving circuit 23
Then, the received signal is converted from the optical pulse to the electric pulse by the PD 6, and the logarithmic amplifier circuit 21 amplifies the amplitude according to the logarithmic conversion to obtain a reflected signal. Since logarithmic conversion is performed here, in the waveform of the received signal, even a signal with a large amplitude, that is, a signal with strong reflection is amplified without being saturated in amplitude.

The amplified reflection signal is converted from analog to digital by the A / D converter 22 and stored in the reflection waveform memory 24. In the A / D converter 22, the trigger signal generating circuit 1
The A / D conversion is started from the time when the start signal from is input, and the waveform of the reflection signal after the transmission is started is stored in the reflection waveform memory 24 at each sampling interval determined by the A / D converter 22. Digitally stored in sequence. The shorter the sampling interval of the A / D converter 22, the higher the distance resolution, and the distance resolution at 100 MHz (10 nsec intervals) is 1.5 m.

The relationship between the address in the reflection waveform memory and the waveform data will be described. FIG. 2 is an explanatory diagram illustrating an example of an internal storage format of the reflection waveform memory 24. In the memory, the address and the amplitude of the waveform data have a one-to-one correspondence. The first address of the memory is 1000, and the amplitude at the start of transmission is stored in the 1000 address as amplitude data. Hereinafter, amplitude data is stored at sampling intervals of 10 nanoseconds in the order of addresses. Each amplitude data is 1 byte (8 bits) and 25
If the amplitude data of 6 points is stored, the size of the reflection waveform memory is 256 bytes, and the 256th amplitude data is stored at the address 1255.

FIG. 3 is a waveform data processing unit 2 according to the first embodiment.
5 is a configuration diagram showing 5, an average noise level calculating means in this case is an average noise level calculating circuit, 27 is an approximate waveform generating means, for example, an approximate straight line generating circuit, 28 is a rising point calculating circuit, and 29 is a distance calculating circuit. Is. In this embodiment, the rising point calculation circuit 28 and the distance calculation circuit 29 constitute the distance calculation means. FIG. 4 is a flowchart showing the flow of processing in the waveform data processing unit 25.
The processing of the waveform data processing unit 25 will be described based on this flowchart. Prior to the process in this flowchart, the average noise level calculation circuit 26 calculates the average noise level in advance. This average noise level is calculated, for example, by a predetermined number of amplitude values of the reflection waveform stored in the reflection waveform memory 24 in the state where no optical pulse is transmitted (this waveform indicates the dark noise level of the receiving circuit), for example. 10
Calculate by averaging only ~ 20 sample data. This average noise level coincides with the amplitude level in the portion where the amplitude is substantially constant from the time t0 to the rising point in the reflection waveform of FIG.

In step ST1 of FIG. 4, the rising point calculation circuit 28 reads the average noise level calculated in advance by the average noise level calculation circuit 26. Next, in step ST2, the approximate straight line generation circuit 27 causes the reflection waveform memory 24
The waveform data stored in is read and the differential coefficient of the waveform data is calculated in step ST3. The calculation method of the differential coefficient is
For example, the smoothing differential method is used for the calculation. The number of smoothing points when calculating the smoothing differential value is 11 in this embodiment. Regarding the smoothing differential method, edited by Shigeo Minami, Waveform Data Processing for Scientific Measurement, CQ Publishing, pp. 111-1.
See page 13, "Chapter 6, Signal Waveform Detection and Extraction," for further details. Further, for example, by using the polynomial fitting method of the moving average method, it is possible to remove the noise in the reflected waveform and obtain the derivative. Of course, other methods may be used.

In step ST4, the point where the obtained differential coefficient is the maximum, that is, the point where the inclination of the reflection waveform in the increasing direction is the maximum is obtained. As shown by the curve B or the curve C in FIG. 5A, the reflection waveform is a convex curve, and the rising portion from the rising point tr to the apex (section indicated by P in the figure).
Then it becomes a positive differential coefficient. The value of the differential coefficient is as shown by the curve Db or the curve Dc in FIG. 5B, and has an inflection point at the maximum inclination of the reflected waveform. Next, the approximate straight lines pb and pc are calculated by the least square method using the waveform data of 11 points centered on the point where the differential coefficient is maximum (step ST5). In steps ST3, ST4 and ST5, the approximate straight line generation circuit 27 linearly approximates the rising portion of the reflected waveform to generate an approximate straight line.

Further, the rising point calculation circuit 28 finds the intersection between the approximate straight line and the average noise level in step ST6, and sets the time position of the intersection as the rising point. As a result, the rising point is t1 in the case of the curved line B having a high reflection intensity, and the rising point is t2 in the case of the curved line C having a low reflection intensity.

The rising point calculation circuit 28 recognizes the rising points t1 and t2 obtained above as the time when the optical pulse reflected by the reflector 5 is received by the receiving circuit 23. Then, the distance calculation circuit 29 calculates the time from the transmission of the optical pulse to the reception of the reception circuit 23 by using the position of the rising point, and calculates the distance to the reflector 5 from this time. To do. Specifically, the difference between the address of the rising point and the leading address of the reflection waveform memory is calculated in step ST7. If the first address is 1000 and the 20th point is a rising point, the rising address is 1019,
The difference between the two addresses is 19. In step ST8, the distance to the reflector 5 is calculated from the difference in address. If the sampling interval is 10 nanoseconds, the time from the transmission of the optical pulse from the transmission circuit to the reception of the optical pulse is 10 nanoseconds × 19 address = 190 nanoseconds. Therefore, the distance to the reflector is 190 nanoseconds x speed of light (3 x 10 ⁸ m) /
2 = 28.5 m.

As described above, in this embodiment, the approximate waveform is generated by linearly approximating the section including the point where the slope of the rising portion P of the reflected waveform is maximum, and the temporal position of the rising point is determined from this approximate waveform. is doing. Therefore, the temporal position of the rising point can be determined according to the inclination of the rising portion P, the distance can be calculated regardless of the reflectance of the reflector 5, and the distance accuracy can be improved. . For example, as apparent from FIG. 5, compared with the conventional rising points t1 and t2 in FIG. 18, both rising points t1 and t2 in this embodiment are close to the true rising point tr. Furthermore, the detection error (difference between t1 and t2) of the rising point due to the difference in the reflection intensity of the reflector 5 is small. Furthermore, in this embodiment, the reflection waveform memory 24
Since the reflected waveform is stored as a digital value corresponding to the address, the calculation in the subsequent waveform processing can be facilitated. Of course, instead of storing it as a digital value, it is also possible to store it in analog form and perform waveform processing.

Since the actual waveform data has variations in amplitude due to noise, if the smoothing process of the waveform data is added before calculating the differential coefficient in step ST3, the reliability of the calculated distance is further improved. This smoothing process is also edited by Shigeo Minami, Waveform data processing for scientific measurement, C
Q Publishing, pp. 84-110, "Chapter 5 Noise Reduction Method by Arithmetic Processing". For example, it is preferable to use the quadratic polynomial fitting method in which the rising portion of the reflected waveform is less blunt. Further, in the first embodiment, when calculating the approximate straight line by the method of least squares, 11 points of waveform data were used, centered on the point where the differential coefficient was the maximum, and 5 points before and 5 points after the point, but the number of data was 11 points. It is not limited to. However,
If it is too small, it is likely to be affected by the unevenness due to the noise of the waveform data, and if it is too large, the slope becomes flat. Therefore, it is desirable to have a score that can represent the slope of the rising portion with as little error as possible. Further, the linear approximation is not limited to the least square method, and the linear approximation may be performed by another method.

Further, when obtaining the rising point, in the above embodiment, the rising point was set as the 20th point of the waveform data and the distance was calculated using the address. However, the approximate straight line and the average noise level were calculated in the sample data. If the data is interpolated and calculated, the distance calculation accuracy can be further improved. For example, the distance resolution is 1. If the first decimal place is calculated like the 20.6th point between the 20th and 21st points of the address and the distance is calculated from the temporal position of this rising point.
This means an improvement of 10 times from 5 m to 15 cm.

Example 2. Hereinafter, a vehicle radar device according to a second embodiment of the present invention will be described. In the first embodiment, the approximate straight line generating circuit 27 linearly approximates the rising portion of the reflected waveform to generate an approximate straight line, but in the second embodiment, the rising portion of the reflected waveform is approximated to a curve to generate an approximate curve.
The overall configuration of the vehicle radar device according to this embodiment is the same as that of FIG. 1 in the first embodiment. FIG. 6 is a configuration diagram showing the waveform data processing unit 25 according to the second embodiment, where 31 is a vertex position calculation circuit and 32 is an approximate quadratic curve generation circuit. The apex position calculating circuit 31 and the approximate quadratic curve generating circuit 32 constitute an approximate waveform generating means. Other parts are the same as or equivalent to those in Embodiment 1, and in this embodiment also, the rising point calculation circuit 28 and the distance calculation circuit 29 constitute distance calculation means. FIG. 7 is a flowchart showing the flow of processing in the waveform data processing section 25, and the processing of the waveform data processing section 25 will be described below based on this flowchart. Similar to the first embodiment, the average noise level calculation circuit 26 calculates the average noise level in advance before the process in this flowchart.

In step ST1 of FIG. 7, the rising point calculating circuit 28 reads the average noise level calculated in advance by the average noise level calculating circuit 26. Next, in step ST2, the vertex position calculation circuit 31 reads the waveform data stored in the reflection waveform memory 24, and in step ST3.
Then, the differential coefficient of the waveform data is calculated. The differential coefficient is calculated by the smoothing differential method as in the first embodiment. In step ST14, the point where the differential coefficient changes from positive to negative, that is, the position of the apex of the reflected waveform is obtained. Figure 8
As shown by the curve B or the curve C in FIG. 8A, the reflection waveform is a convex curve, and its differential coefficient is positive at the vertex tt as shown by the curve Db or the curve Dc in FIG. 8B. Change to negative. Next, the approximate quadratic curve generation circuit 32 calculates the approximate quadratic curves qb and qc centering on the vertex position by the least square method using the waveform data of 11 points in the rising direction in front of the vertex position (step). ST15). Through steps ST3, ST14, and ST15, the vertex position calculation circuit 31 and the approximate quadratic curve generating circuit 32 approximate the rising portion of the reflected waveform by a quadratic curve to generate an approximate quadratic curve.

Further, the rising point calculation circuit 28 finds the intersection of the approximate quadratic curves qb and qc and the average noise level in step ST16, and sets the temporal position of the intersection as the rising point. As a result, the curve B, which is a reflection waveform with high reflection intensity,
In the case of, the rising point is t1, and in the case of the curved line C having a small reflection intensity, the rising point is t2.

The rising point calculation circuit 28 recognizes the rising points t1 and t2 obtained above as the time when the optical pulse reflected by the reflector 5 is received by the receiving circuit 23. Then, the distance calculation circuit 29 calculates the time from when the optical pulse is transmitted from the transmission circuit 4 to when it is received by the reception circuit 23 by using the position of the rising point, and the distance from the time to the reflector 5 is calculated. Calculation is performed by the same method as in Example 1 (step S
T7, ST8).

As described above, in this embodiment, the section including the apex of the convex portion of the reflected waveform is curve-approximated to generate an approximate waveform,
The temporal position of the rising point is determined from this approximate waveform. Therefore, the temporal position of the rising point can be determined according to the shape of the rising portion P of the convex portion, the distance can be calculated regardless of the magnitude of the reflectance of the reflector 5, and the distance accuracy can be improved. It will be possible. For example, FIG.
8, the rising points t1 and t2 in this embodiment are both true rising points t1 and t2.
It is close to r. Furthermore, the detection error (difference between t1 and t2) of the rising point due to the difference in the reflection intensity of the reflector 5 is small. As for the detection error, the error of t1 and t2 is smaller in the quadratic curve approximation in this embodiment than in the case of the linear approximation in the first embodiment. Therefore, regardless of the reflectance of the reflector,
The distance to the reflector can be calculated, and the accuracy of the distance to the reflector 5 can be improved.

As in the first embodiment, since the actual reflected waveform has a variation in amplitude due to noise, step ST3
If the smoothing process of the waveform data is added before calculating the differential coefficient with, the reliability of the calculated distance is further improved. As the smoothing method, for example, a quadratic polynomial fitting method in which the rising portion of the reflected waveform is less blunt may be used. Further, in the apex position calculation circuit 31, the differential coefficient is used as a method for obtaining the apex position, but the point where the amplitude is maximum may be used as the apex position, in which case the calculation becomes simple.

Further, in the second embodiment, when calculating the approximate curve by the method of least squares, the point at which the differential coefficient changes from positive to negative is used as the apex, and the waveform data of 11 points in the rising direction from this point is used. The number of data is not limited to 11 points, and the point in the rising direction from the vertex position was used.
Waveform data of a plurality of points including the apex tt may be used. Further, the method of calculating the approximated curve is not limited to the method of least squares, and it is not limited to the quadratic curve, and a higher-order curve may be approximated.

Similarly to the first embodiment, when the rising point is obtained, the distance is calculated by using the address. However, if the approximation curve and the average noise level are calculated by interpolating between the data of the sample data, The distance calculation accuracy can be further improved.

Example 3. Hereinafter, a vehicle radar device according to a third embodiment of the present invention will be described. The overall configuration of the vehicle radar device according to this embodiment is the same as that of FIG. 1 in the first embodiment. FIG. 9 is a configuration diagram showing the waveform data processing unit 25 according to the third embodiment, and the same reference numerals as those in the second embodiment indicate the same or corresponding portions. The vertex position calculation circuit 31 in this embodiment is an example of the vertex position calculation means. Also in this embodiment, the rising point calculating circuit 28 and the distance calculating circuit 29 constitute the distance calculating means. FIG. 10 is a flowchart showing the flow of processing in the waveform data processing unit 25, and the processing of the waveform data processing unit 25 will be described below based on this flowchart.

In step ST2 of FIG. 10, the vertex position calculation circuit 31 reads the waveform data stored in the reflection waveform memory 24, and in step ST3, the differential coefficient of the waveform data is calculated. The calculation method of the differential coefficient is the same as in the first embodiment.
Calculated by the smoothed differential method. In step ST14,
The point where the differential coefficient changes from positive to negative, that is, the position of the apex of the reflected waveform is obtained. The method for obtaining this is the same as in the second embodiment, and in FIG. 11, the vertex position is the point tt at which the differential coefficient changes from positive to negative.

Next, in step ST26, the rising point calculation circuit 28 sets the points returned from the vertex position calculated by the vertex position calculation circuit 31 for a predetermined time as the rising points t1 and t2. The predetermined time to be returned is set in advance from the time required for the level of the transmission pulse to reach the maximum from the rise, and is set to, for example, about 10 pieces of sample data. The rising points t1 and t2 obtained above are
The time when the light pulse reflected by the reflector 5 is received by the receiving circuit 23 is recognized. In step ST27, the distance calculation circuit 29 calculates the difference between the rising points t1 and t2 and the start address of the reflection waveform memory 24. Further, in step ST8, an optical pulse is transmitted from the transmission circuit 4 and then received by the reception circuit 23. The time to reach the reflector 5 is calculated and the distance to the reflector 5 is calculated from this time.

In this embodiment, the vertex position calculating circuit 31 calculates the temporal position of the convex vertex tt of the waveform data stored in the reflection waveform memory 24, and the distance calculating circuit 29 uses the vertex position to calculate the reflector. The distance to 5 is calculated.
Since the temporal positions of the vertices are almost the same even if the reflectance of the reflector 5 changes, the distance to the reflector 5 can be calculated regardless of the reflectance of the reflector 5. . Further, as compared with the first and second embodiments, the distance to the reflector can be calculated by a simple calculation regardless of the reflectance of the reflector, and the accuracy of the distance to the reflector 5 can be improved. Become.

As in the first and second embodiments, since the actual waveform data has variations in amplitude due to noise, if the waveform data is smoothed before calculating the differential coefficient in step ST3, the calculated distance is further increased. Improves reliability. As the smoothing method, for example, a quadratic polynomial fitting method in which the rising portion of the reflected waveform is less blunt may be used. Further, in the apex position calculation circuit 31, a differential coefficient is used as a method for obtaining the apex position, but the point at which the amplitude is maximum may be the apex position.

Further, when the vertex position calculating circuit 31 calculates the vertex position, if the points at which the differential coefficient changes from positive to negative are calculated between the data of the sample data, the distance resolution is improved. For example, if the differential coefficient changes from positive to negative between the 25th point and the 26th point, calculate the straight line connecting both points and calculate the point where this straight line crosses 0. Then, if the vertex position is calculated up to the 25.3th point and the first decimal place, the distance resolution is improved 10 times from 1.5 m to 15 cm. However, in this example, the sampling frequency is 100 MHz.

Further, in the above embodiment, the point which has returned from the apex position for a predetermined time is defined as the rising point, and the distance is calculated from the temporal position of the rising point. However, the apex position and the distance have a one-to-one correspondence. Therefore, a method of previously storing the correspondence between the vertex position and the distance as a table and reading the corresponding distance from the table when the vertex position is obtained may be used.
In this case, the processing speed can be further increased.

Example 4. Hereinafter, a vehicle radar device according to a fourth embodiment of the present invention will be described. The overall configuration of the vehicle radar device according to this embodiment is the same as that of FIG. 1 in the first embodiment. FIG. 12 is a configuration diagram showing the waveform data processing unit 25 according to the fourth embodiment, and the same reference numerals as those in the second embodiment indicate the same or corresponding portions. Also in this embodiment, the rising point calculating circuit 28 and the distance calculating circuit 29 constitute the distance calculating means. 33 is a vertex level detecting means for detecting the vertex level of the reflected waveform, which is realized by a vertex level calculating circuit in this embodiment. The apex level calculation circuit 33 calculates the amplitude value (apex level) at the apex position of the reflected waveform. Reference numeral 34 denotes a threshold value calculation unit, which is composed of an average noise level calculation circuit 35 and a threshold value calculation circuit 36, and calculates a threshold value for judging the rising point. Reference numeral 37 denotes a distance correction circuit which is an example of distance correction means, determines a correction value according to the vertex level calculated by the vertex level calculation circuit 33, and corrects the distance calculated by the distance calculation circuit 29.

FIG. 13 is a flow chart showing the flow of processing in the waveform data processing section 25. Prior to the processing in this flow chart, the threshold value calculating section 34 uses a threshold value for judging the rising point in advance. Is calculated. In this threshold value calculation method, for example, a value obtained by adding a certain value to the average noise level is used as the threshold value. The calculation method of the average noise level is the same as in the first and second embodiments, the reflection waveform stored in the reflection waveform memory 24 in the state where the optical pulse is not transmitted by the average noise level calculation circuit 26 (this waveform indicates the dark noise level of the reception circuit). .) Is calculated by averaging a fixed number of amplitude values. After calculating the average noise level, the threshold value calculation circuit 36 adds a constant value to the average noise level,
Use as a threshold.

The processing of the waveform data processing section 25 will be described below with reference to the flowchart shown in FIG. In step ST31, the rising point calculation circuit 28 reads the rising point detection threshold value calculated in advance by the threshold value calculation unit 34. The rising point calculation circuit 28 also reads the amplitude data representing the amplitude of the waveform data from the reflection waveform memory 24 point by point (step ST32), and compares the amplitude data with the threshold value (step ST33). As a result of the comparison, if the amplitude data is smaller than the threshold value, it is determined that it is not the rising point, the process returns to step ST32, the amplitude data of the next sampling interval is read, and it is compared with the threshold value. The amplitude data and the threshold value are sequentially compared, and when the determination in step ST33 is that amplitude data ≧ threshold value, it is determined that the amplitude data at that time point is the rising point.

The distance calculation circuit 29 stores the address of the rising point detected above (step ST34). The distance calculation circuit 29 calculates the time from the position of the rising point until the optical pulse is transmitted from the transmission circuit to the reception circuit, and calculates the distance to the reflector from this time.
Specifically, the difference between the address of the rising point and the leading address of the reflection waveform memory 24 is calculated in step ST35, and step S35 is performed.
At T8, the distance to the reflector 5 is calculated from the difference in address.

Next, in step ST2, the vertex level calculation circuit 33 reads the waveform data stored in the reflection waveform memory 24, and in step ST3, the differential coefficient of the waveform data is calculated. The differential coefficient is calculated by the smoothing differential method as in the first embodiment. In step ST14, similarly to the second embodiment, the point where the differential coefficient changes from positive to negative, that is, the position of the apex of the reflected waveform is obtained, and the amplitude value at this apex position is calculated as the apex level.

The distance correction circuit 37 reads the calculated vertex level and calculates a distance correction value according to the vertex level (step ST36). FIG. 14 shows an example of the relationship between the vertex level and the distance correction value. In the figure, the horizontal axis is the apex level and the vertical axis is the distance correction value, which is the relationship obtained by actual measurement with an actual device. Based on FIG. 14, a distance correction value table showing the relationship between the vertex level and the distance correction value is created in advance. As shown in FIG. 18, the larger the reflectance of the reflector 5, that is, the higher the vertex level, the smaller the error between the true distance and the calculated distance, and the smaller the reflectance of the reflector 5, that is, the smaller the vertex level. The error between the true distance and the calculated distance becomes large. On the other hand, in this embodiment, the smaller the vertex level, the larger the distance correction value. Since the apex level is equal to or higher than the threshold value for calculating the rising point, the section of the table used for the actual calculation is the maximum value Pmax of the apex from the threshold value (e.g.
5 is the maximum). The threshold value at this time fluctuates according to the average noise level. Based on the distance correction value table, the distance correction value according to the vertex level calculated by the vertex level calculation circuit 33 is determined. Next, step ST
At 37, a value obtained by subtracting the distance correction value from the distance calculated by the distance calculation circuit 29 is calculated as the final distance.

As described above, in this embodiment, the threshold value is calculated from the average noise level to determine the rising point of the reflected waveform, and the time position of this rising point is used to calculate the distance to the reflector. Further, the level of the apex of the convex portion of the reflected waveform is calculated, and the distance is corrected according to the apex level. Since the distance correction value is set to be larger as the vertex level is smaller, the distance detection error caused by the deviation of the rising point due to the reflectance of the reflector 5 can be reduced, and the reflectance of the reflector 5 can be reduced. The distance can be calculated regardless of the size, and the distance accuracy can be improved.

Further, in this embodiment, the reflection waveform memory 2
Since the reflected waveform is stored as a digital value corresponding to the address in 4, the calculation in the subsequent waveform processing can be facilitated and the accuracy of the distance to the reflector can be improved. Of course, instead of storing it as a digital value, it is also possible to store it in analog form and perform waveform processing.

Since the actual waveform data has variations in the amplitude due to noise, if the smoothing process of the waveform data is added before calculating the differential coefficient in step ST3, the reliability of the calculated distance is further improved. As the smoothing method, for example, a quadratic polynomial fitting method in which the rising portion of the reflected waveform is less blunt may be used. Further, in the apex level calculation circuit 33, the differential coefficient is used as the method for obtaining the position of the apex, but the point where the amplitude is maximum may be the position of the apex. Further, when calculating the rising point, the distance calculation accuracy can be further improved by interpolating the waveform data and the average noise level up to the point instead of calculating the distance using the address.

Example 5. Hereinafter, a vehicle radar device according to a fifth embodiment of the present invention will be described. This example
In the operation of the fourth embodiment, it is mainly configured by hardware,
The distance calculation means and the distance correction means are realized by software processing by a microcomputer. FIG. 15 is a configuration diagram showing a vehicle radar device according to this embodiment, and the same reference numerals as those in the conventional example indicate the same or corresponding portions. Also,
Also in this embodiment, after the optical pulse is converted into the electric pulse by the PD 6, the amplitude is amplified by the logarithmic amplification circuit 21 according to the logarithmic conversion to be a reflected signal. Since logarithmic conversion is performed here, in the waveform of the received signal, even a signal with a large amplitude, that is, a signal with strong reflection is amplified without being saturated in amplitude. Further, 38 is a vertex level detecting circuit which is an example of the vertex level detecting means, and 39 is a distance correcting circuit which is an example of the distance correcting means.

As in the conventional case, the counter 10 counts the time from receiving the count start signal (start signal) to receiving the stop signal, and the distance calculation circuit 11 calculates the distance to the reflector 5. The calculated distance does not take into consideration the reflectance of the reflector 5, and an error occurs in the calculated distance depending on the magnitude of the reflectance as shown in the problem. The apex level detection circuit 38 is a circuit that holds the values of the apexes of the convex portions of the reflected waveform, and the schematic configuration of the main circuit is a diode 41 and a capacitor 42 as shown in FIG. The diode 41 and the capacitor 42 are connected in series, the input voltage Vi is applied to both ends thereof (one end is grounded), and the voltage across the capacitor 42 is taken out as the output voltage Vo. In the section where the input voltage Vi increases toward the apex level, the voltage at the input end of the diode 41 ≧ the voltage at the output end of the diode 41 and the forward voltage is applied to the diode 41, so that the resistance of the diode 41 is small and the current flows. , Electric charges are accumulated in the capacitor 42. On the contrary, in the section where the input voltage Vi decreases from the apex level, the voltage at the input terminal of the diode 41 <the diode 4
Since the voltage at the output terminal of 1 is applied to the diode 41 in the opposite direction, a large current does not flow through the resistance of the diode 41 and no charge is stored in the capacitor 42. Therefore, when the input voltage Vi as shown in FIG. 16B is applied, the output voltage Vo becomes equal to the peak level of the input voltage Vi, and the peak value is held as shown in FIG. 16C. After that, the distance correction circuit 39 is similar to the fourth embodiment.
The distance calculated by the distance calculation circuit 11 is corrected by referring to, for example, the distance correction value table according to the level of the apex.

Thus, if the level of the vertex is obtained and the distance is corrected according to the vertex level, the distance correction value can be generated according to the reflectance of the reflector 5, and as a result, It is possible to accurately calculate the distance to the reflector 5 regardless of the reflectance of the reflector 5. Further, it is easier to calculate the level of the apex than to calculate the temporal position of the apex of the reflected waveform.

[0063]

As described above, according to the first aspect of the present invention, the transmitting means for transmitting the electromagnetic wave, the receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by the reflector,
Waveform storage means that has an address and stores the waveform of the reflected signal received by the reception means as waveform data, and an electromagnetic wave is transmitted from the transmission means using the waveform data stored in the waveform storage means and is received by the reception means. When calculating the time and the distance to the reflector from this time, the waveform data is stored as a digital value corresponding to the address by providing the distance calculation means that uses the address of the waveform storage means. ,
There is an effect that a vehicular radar device that can easily perform calculations in the subsequent waveform processing is obtained.

According to the second aspect, the transmitting means for transmitting the electromagnetic wave, the receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by the reflector, and the waveform of the reflected signal received by the receiving means are Waveform storage means for storing as waveform data, average noise level calculation means for calculating an average noise level from the waveform data, approximate waveform generation means for approximating the rising portion of the waveform of the reflected signal to generate an approximate waveform, and approximate waveform and average The rising point is the intersection with the noise level, and the time position of this rising point is used to calculate the time from the transmission of the electromagnetic wave to the rising point, and the distance from this time to the reflector is calculated. By providing the calculating means, the distance to the reflector can be calculated accurately,
In particular, there is an effect that an error in the calculated distance can be reduced regardless of the magnitude of the reflectance of the reflector, and a vehicle radar device capable of improving the distance resolution can be obtained.

According to the third aspect, the approximate waveform generating means in the second aspect of the invention generates an approximate waveform by linearly approximating a section including a point where the slope of the rising portion of the waveform of the reflected signal is maximum. By doing so, the distance to the reflector can be calculated accurately, and in particular, the error of the calculated distance can be reduced regardless of the magnitude of the reflectance of the reflector, and the distance resolution can be improved. There is an effect that can be obtained.

According to a fourth aspect, the approximate waveform generating means in the second aspect of the invention generates an approximate waveform by curve-approximating a section including a peak of a convex portion of a waveform of a reflected signal. As a result, the distance to the reflector can be calculated accurately, and in particular, the error of the calculated distance can be reduced regardless of the magnitude of the reflectance of the reflector, and the vehicle radar device capable of improving the distance resolution can be obtained. There is.

According to the present invention, the transmitting means for transmitting the electromagnetic wave, the receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by the reflector, and the waveform of the reflected signal received by the receiving means are Waveform storage means for storing as waveform data, apex position calculation means for calculating the temporal position of the apex of the convex portion of the waveform of the reflected signal, and time from the transmission of the electromagnetic wave using the apex position to the apex position By providing a distance calculating means for calculating the distance to the reflector from this time, the distance to the reflector can be calculated accurately, and the calculated distance can be calculated regardless of the magnitude of the reflectance of the reflector. There is an effect that it is possible to obtain a vehicle radar device capable of reducing the error and further improving the range resolution.

According to claim 6, the waveform storage means in the inventions of claims 2 to 5 has an address, and the distance calculation means calculates time from the difference between the addresses,
By calculating the distance to the reflector from this time, there is an effect that a vehicular radar device that can easily perform the calculations in claims 2 to 5 is obtained.

According to the present invention, the transmitting means for transmitting the electromagnetic wave, the receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by the reflector, and the electromagnetic wave transmitted from the transmitting means and received by the receiving means. Distance calculating means for calculating the time to reach the reflector from this time,
Since the apex level detecting means for detecting the level of the apex of the convex portion of the reflection signal received by the receiving means and the distance correcting means for correcting the distance according to the apex level are provided, the distance to the reflector can be accurately measured. There is an effect that a vehicular radar device can be obtained that can be calculated well and that the error in the calculated distance can be made small regardless of the magnitude of the reflectance of the reflector.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a vehicle radar device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an internal storage format of the reflection waveform memory according to the first embodiment.

FIG. 3 is a configuration diagram illustrating a waveform data processing unit according to the first embodiment.

FIG. 4 is a flowchart showing processing in the waveform data processing unit according to the first embodiment.

FIG. 5 is an explanatory diagram illustrating linear approximation of a reflected waveform according to the first embodiment.

FIG. 6 is a configuration diagram showing a waveform data processing unit according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing processing in the waveform data processing unit according to the second embodiment.

FIG. 8 is an explanatory diagram illustrating curve approximation of a reflection waveform according to the second embodiment.

FIG. 9 is a configuration diagram showing a waveform data processing unit according to a third embodiment of the present invention.

FIG. 10 is a flowchart showing processing in the waveform data processing unit according to the third embodiment.

FIG. 11 is an explanatory diagram illustrating a process related to a reflection waveform according to the third embodiment.

FIG. 12 is a configuration diagram showing a waveform data processing unit according to a fourth embodiment of the present invention.

FIG. 13 is a flowchart showing processing in the waveform data processing unit according to the fourth embodiment.

FIG. 14 is a graph showing a relationship between a vertex level and a distance correction value according to the fourth embodiment.

FIG. 15 is a configuration diagram showing a vehicle radar device according to a fifth embodiment of the present invention.

FIG. 16 is an explanatory diagram illustrating a configuration of a vertex level detection circuit according to the fifth embodiment.

FIG. 17 is a configuration diagram showing a conventional infrared tracking sensor.

FIG. 18 is a graph showing a waveform of a reflected signal, in which the horizontal axis represents time and the vertical axis represents amplitude.

[Explanation of symbols]

 4 Transmitting means 5 Reflector 23 Receiving means 24 Waveform storing means 26 Average noise level calculating means 27 Approximate waveform generating means 28 Rising point calculating circuit 29 Distance calculating circuit 31 Apex position calculating means 32 Approximate waveform generating means 33, 38 Apex level detecting means 37,39 Distance correction means

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Minoru Nishida 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Industrial Systems Research Center

Claims (7)

[Claims] 1. A transmission means for transmitting an electromagnetic wave, a reception means for receiving the electromagnetic wave transmitted from the transmission means and reflected by a reflector, and a waveform of a reflection signal having an address and received by the reception means as waveform data. Waveform storage means for storing as
And calculating the time until the electromagnetic wave is transmitted from the transmitting means and received by the receiving means using the waveform data stored in the waveform storage means, and when calculating the distance from this time to the reflector, A vehicle radar device comprising a distance calculation means that uses the address of the waveform storage means. 2. A transmitting means for transmitting an electromagnetic wave, a receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by a reflector, and a waveform for storing a waveform of a reflected signal received by the receiving means as waveform data. Storage means, average noise level calculation means for calculating an average noise level from the waveform data, approximate waveform generation means for approximating the rising portion of the waveform of the reflected signal to generate an approximate waveform, and the approximate waveform and the average noise level The intersection is defined as the rising point, and the time position of the rising point is used to calculate the time from the transmission of the electromagnetic wave to the rising point, and the distance from the time to the reflector is calculated. Vehicle radar device having a distance calculating means for 3. The approximate waveform generating means is for linearly approximating a section including a point where the slope of the rising portion of the waveform of the reflected signal is maximum to generate the approximate waveform. Vehicle radar device. 4. The radar apparatus for a vehicle according to claim 2, wherein the approximate waveform generating means generates an approximate waveform by curve-approximating a section including a peak of a convex portion of the waveform of the reflected signal. . 5. A transmitting means for transmitting an electromagnetic wave, a receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by a reflector, and a waveform for storing a waveform of a reflected signal received by the receiving means as waveform data. A storage unit, an apex position calculation unit that calculates a temporal position of the apex of the convex portion of the waveform of the reflected signal, and a time from the transmission of the electromagnetic wave from the transmission unit using the apex position to the apex position. A vehicle radar device comprising a distance calculating means for calculating and calculating a distance from the time to the reflector. 6. The waveform storage means has an address,
The distance calculation means calculates the time by the difference of the above address,
The vehicle radar device according to any one of claims 2 to 5, wherein the distance to the reflector is calculated from this time. 7. A transmitting means for transmitting an electromagnetic wave, a receiving means for receiving the electromagnetic wave transmitted from the transmitting means and reflected by a reflector, the electromagnetic wave being transmitted from the transmitting means to being received by the receiving means. Distance calculating means for calculating time and distance from the time to the reflector, apex level detecting means for detecting the level of the apex of the convex portion of the reflection signal received by the receiving means, and the apex level Vehicle radar device having a distance correcting means for correcting the distance according to the following.