Patent Application
20080007446
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
Referring first to
The vehicle control device 1 includes a recognition/inter-vehicle distance control ECU 3. The distance control ECU 3 includes a microcomputer, and includes an input/output interface (I/O), various drive circuits and detector circuits. These hardware construction is known and hence not described here in detail.
The distance control ECU 3 receives detection signals from a laser radar sensor 5 which is the vehicle radar device, a vehicle speed sensor 7, a brake switch 9 and a throttle position sensor 11, and sends drive signals to an alarm sound generator 13, a distance indicator 15, an abnormality indicator 17, a brake actuator 19, a throttle actuator 21 and to an automatic transmission controller 23.
To the distance control ECU 3, further, there are connected an alarm sound volume-setting unit 24 for setting the volume of alarm sound, an alarm sensitivity-setting unit 25 for setting the sensitivity in the alarm determination processing, a cruise control switch 26, a steering sensor 27 for detecting the amount of operating a steering wheel (not shown), and a yaw-rate sensor 28 for detecting the yaw-rate occurring in the vehicle. The distance control ECU 3 further includes a power source switch 29, and starts executing predetermined processing upon the turn-on of the power source switch 29.
As shown in
The polygonal mirror 73 has six mirrors with different plane tilting angles, and is capable of producing a laser beam so as to discretely scan over ranges of predetermined angles in the direction of vehicle width and in the direction of vehicle height. The laser beam is thus scanned in a two-dimensional manner. The scanning pattern will now be described with reference to
In
When the laser beam that is reflected is received upon radiating the laser beam onto the above detection area 121, the laser radar CPU 70 calculates scanning angles θx and θy representing angles of radiating the laser beams and a distance L that is measured, and outputs them to the distance control ECU 3. The two scanning angles θx and θy are such that the longitudinal scanning angle θy represents an angle between the Z-axis and a line along which the laser beam is projected onto the YZ plane, and the transverse scanning angle θx represents an angle between the Z-axis and a line along which the laser beam is projected onto the XZ plane.
As shown in
Referring to
The integration processing unit 88 specifies, out of the received light signals that are temporarily stored, the received light signals of a predetermined number corresponding to the predetermined number of laser beams radiated neighboring each other in the direction of X-axis as a range of the received light signals to be integrated. The integration processing unit 88 calculates the integrated signal (integrated received light signal) of the received light signals belonging to the specified range. The range of the received light signals that are specified by, and are to be integrated by, the integration processing unit 88 and how to calculate the integrated signal, will now be described with reference to
It may be attempted to detect the preceding vehicle by using the vehicle radar device of this embodiment. In this case, the preceding vehicle has a reflector on the rear surface thereof to highly reflect the laser beam. The vehicle body, too, reflects the laser beam relatively highly though it is not as high as that of the reflector. Usually, therefore, the light reflected by the preceding vehicle is sufficiently intense, and it is possible to detect the preceding vehicle from the received light signals of single reflected light. However, when, for example, mud, snow and the like adheres to the rear surface of the preceding vehicle, the intensity of light reflected by the preceding vehicle drops. In this case, therefore, it becomes probable that the preceding vehicle cannot be detected based on the individual received light signals corresponding to light reflected by the preceding vehicle.
Therefore, a plurality of received light signals are integrated to amplify the received light signals which are reflected by the preceding vehicle to detect even the reflected waves having small intensities. The integration processing unit 88, first, specifies the received light signals that are to be integrated. That is, as shown in
Thus, integrated signals obtained by integrating the received light signals belonging to the specified ranges are successively output in synchronism with specifying the range of the received light signals to be integrated. Referring to
As shown in
By calculating the integrated signal by the integration processing unit 88, therefore, it is possible to improve a ratio (S/N ratio) of the received light signal component So and the noise component No. As a result, even when the received light signal component S contained in each received light signal is so small that it cannot be easily distinguished from the noise component N, use of the above integrated signals makes it possible to detect the reflecting object based on the received light signal component So that is amplified.
As described above, further, the integrated processing unit 88 moves the range of the received light signals that are to be integrated by shifting the received light signals one by one. This minimizes a drop in the resolution of detection based on the integrated signals while integrating four received light signals. That is, if the signals to be integrated are calculated by simply grouping the received light signals output from the light-receiving element 83 in a number of 4, the sensitivity for detecting the reflected light can be improved but the resolution of detection by the integrated signals drops greatly. On the other hand, if the range of the received signals to be integrated is shifted by an amount of one received light signal each time, a drop in the resolution of detection can be suppressed.
In the description of using
The integration processing unit 88 successively outputs the integrated signals obtained by integrating the received light signals belonging to each of the ranges of the received light signals to be integrated, i.e., successively outputs the integrated signals of each of the lines from the line 1 up to line (327−range of the received light signals to be integrated+1) while shifting the range of the received light signals to be integrated.
Referring to
Referring to
The state machine unit 89 determines the state of the verification point along a state transition diagram of
When the condition for the first determination or the sixth determination does not hold (NO), the verification point is determined to be in the “peak search” state and is shifted to a next verification point to repeat the same determination. The “rise start” state literally represents a point at a moment when the peak waveform starts rising to represent the reception of the wave reflected by the reflecting object. The first determination shown in
(first determination #1D)
Condition 1: (c>b) AND [(c−b)>Th (threshold value)] AND (a>b)
Condition 2: (c>b) AND [(c−b)>Th] AND [(c−b)>(|b−a|×2)]
Further, the sixth determination shown in
(sixth determination #6D)
Condition 1: (c>b) AND [(c−b)>Th/4] AND [(c−b)>(|b−a|×3)]
Condition 2: (c>b) AND (b>a) AND [(c−b)+(b−a)>(Th×0.625)]
Here, in the diagram of state transition of
In the case of a peak waveform of a general shape shown in
By giving attention to the fact that a plurality of points which are continuing in time and are forming a peak waveform, follow a particular state transition, the state machine unit 89 determines in which state of “peak search”, “rise start”, “rising”, “falling”or “rise check”, the verification point is present from the signs of differences in the signal components among the verification point and at least two points preceding and succeeding the verification point in time and from the magnitudes of the differences.
Therefore, if a plurality of points continuing in time follow a particular state transition like, for example, “Rise start ST2”→“Rising ST3”→“Falling ST4”→“Peak search ST1”, a point series consisting of the plurality of points is determined to be a group forming the peak waveform.
When the state machine unit 89 finishes the determination of state transition for all points, a received signal integration converter unit 90 stores the integrated signals of a point series belonging to a group that forms a peak waveform that follows any one of the above five state transitions (a) to (e), and executes a processing for changing (converting) the magnitudes of the signal components to “0” (zero) for the points that do not belong to the group for forming the peak waveform. It is therefore made possible to pick up the integrated signals only of the point series belong to the group forming the peak waveform out of the integrated signals output from the integration processing unit 88.
Next, described below is how to determine the state of points by the state machine unit 89 after the point is determined to be in the “rise start” state (after the case 1). In
(second determination #2D)
Condition: (c>b) AND (a<b)
When the condition of the second determination does not hold, i.e., when the state is not “rising”, the verification point shifts to the “falling—1” state. When shifted to the “falling—1” state, a fourth determination (#4D) shown in
(fourth determination #4D)
Condition 1: (c<b) AND (b<a) AND (a−b)>Th AND
Condition 2: |b−c|<Th AND b<a AND (a−b)>Th AND
The state transition described above is the state transition of (a) “Rise start”→“Falling—1”→“Peak search”.
Next, when the condition of the fourth determination does not hold after having shifted to the state of “Falling—1”, the verification point shifts to the state of “Falling—2”. A seventh determination #7D shown in
The seventh determination shown in
(seventh determination #7D)
Condition: |b−c|<Th AND (b<a) AND
A sixth determination #6D shown in
Here, the state transition from the “rise check” state to the “rise start” state represents as shown in
Next, the description returns to when the point is determined to be in the “rising” state of the above-mentioned “case 2”. Here, a third determination #3D shown in
(third determination #3D)
Condition: (c<b) AND (a<b)
When the condition of the third determination holds in the “rising” state of the “case 2”, the next point shifts to the “falling—1” state. The point that has shifted to the “falling—1” state represents the state transition same as those described in the “case 3” and in the “case 4”.
Next, when the seventh determination does not hold in the “case 4”, the verification point is just shifted to the “falling—3” state. After the shift, the first determination is executed for the same verification point. When the condition of the first determination holds, a point next of this point is regarded to be in the “rise start” state. Here, too, the state transition is exhibited from the state forming a valley after the end of the preceding peak in the synthesized waveform of a plurality of peaks to the “rise start” state of the next peak.
In this case, separation of the peak is determined like the state transition in the case of (d). In the case of (d), the falling state of the preceding peak gradually comes to a halt and the next peak is going to rise. In this case, however, the next peak suddenly starts rising while the preceding peak is falling, making a difference. The above state transition it the state transition of (e) “Rise start”→“Rising—3”→“Rise start”.
When the first determination does not hold at a point in the “falling—3” state, the point readily shifts to the “falling—4” state. Thereafter, a fifth determination #5D shown in
(fifth determination #5D)
Condition: (b<a)
When the condition of the fifth determination holds, the peak ends at a point which precedes the point, and the point is returned to the “peak search” state to determine the state for picking up a next new peak. The above state transition is the state transition of (b) “Rise start”→“Falling—4”→“Peak search”. When the fifth determination does not hold, the next point is shifted to “falling 1” to repeat the shift of state transition.
In the foregoing was described the processing for determining the state by the state machine unit 89. Here, however, the state transition diagram shown in
The conditional formulas of the determinations shown in
The offset storing unit 91 shown in
In the case of a group (peak group PK) forming a peak waveform as shown, for example, in
A differential processing storing unit 93 removes the offset component stored in the offset storing unit 91 from the integrated signal component of a point series belonging to the peak group PK stored in the received signal integration/conversion unit 90. That is, as shown in
By removing the offset components from the integrated signal components PKi of points belonging to the peak group PK as described above, it is allowed to remove the noise components superposed on the integrated signal components of the point series belong to the peak group PK without the need of measuring the background noise unlike that of the prior art.
When there are a plurality of peak groups PK as a result of determination by the state machine unit 89, a group number storing unit 92 imparts group numbers to all points belonging to the peak groups PK to distinguish the peak groups PK, and stores the integrated signals of point series belonging to the peak groups PK in relation to the group numbers.
When there is only one peak group PK, it can be easily learned from the integrated signal from which the offset component is removed by the differential processing/storing unit 93 that a point having a signal component which is not zero is the point belonging to the peak group PK. When there is a plurality of peak groups PK and, particularly, when two peaks are attached thereto, however, the boundary in the peak waveform becomes obscure in the integrated signal from which the offset component is removed by the differential processing/storing unit 93.
In the case of a waveform synthesizing two peaks as shown in, for example,
As shown in
The points of group numbers other than “0” (zero) are the points picked up as a peak group PK. For example, the four points having the group number “1” are the points belonging to the same peak group PK. The group number “1” is followed by three points having the group number “2” without holding the group number “0” therebetween. This indicates that the two peaks having the group number “1” and the group number “2” had been attached to each other, and were separated apart into two peaks with the peak separation point as a boundary.
The differential processing/storing unit 93 removes the offset component stored in the offset storing unit 91 from the integrated signal component of the point series belonging to the peak group PK stored in the received signal integration/conversion unit 90, imparts a group number to the integrated signal after the offset has been removed for each of the peak groups PK and stores them.
As shown in
A distance calculation unit 94 specifies a group number of a peak group that is to be picked up, and picks up an integrated signal from which the offset has been removed, that is in agreement with the specified group number from the integrated signals from which the offset has been removed and to which the group numbers have been imparted being stored in the differential processing/storing unit 93. The distance to the reflecting object is calculated from the time until the center of peak waveform of the integrated signal that is picked up is estimated from when the light is emitted. The calculated distance up to the reflecting body is output to the laser radar CPU 70.
Therefore, when it is desired to pick up only an integration signal after the offset has been removed to which, for example, a group number “1” has been imparted, the group number “1” is specified to pick up only the integrated signal from which the offset has been removed and to which the group number “1” has been imparted. Further, the distances can be calculated from the respective peaks by respectively picking up the peaks for the rest of all group numbers.
The laser radar CPU 70 forms position data based on the distance to the reflecting object input from the distance calculation unit 94 and on the scanning angles θx and θy of the corresponding laser beams. Specifically, from the distance and the scanning angles θx and θy, the position data of the reflecting object are calculated on the XYZ rectangular coordinate system with the center of laser radar as an origin (0, 0, 0), the direction of vehicle width as X-axis, the direction of car height as Y-axis, and the direction toward the front of the vehicle as Z-axis. The position data in the XYZ rectangular coordinate system are output as distance data to the distance control ECU 3.
When the distance to the reflecting object is to be calculated based on the integrated signal, the scanning angle θx of the laser beam corresponding to the integrated signal is the scanning angle θx of the laser beam at the central position among the plurality of laser beams corresponding to the plurality of integrated received light signals.
The distance control ECU 3 executes inter-vehicle distance control by recognizing the object based on the distance data from the laser radar sensor 5, and by controlling the vehicle speed by sending drive signals to the brake actuator 19, throttle actuator 21 and automatic transmission control unit 23 to meet the conditions of the preceding vehicle obtained from the recognized object. An alarm determining processing is also executed to produce an alarm in case the recognized object is staying in a predetermined alarm region for a predetermined period of time. The object in this case may be a vehicle travelling in front or a vehicle that is at rest ahead.
The distance ECU 3 will now be briefly described. The distance data output from the laser radar sensor 5 are sent to an object recognition block 43. Based on the three-dimensional position data obtained as the distance data, the object recognition block 43 calculates a central position (X, Y, Z) of the object, and a size (W, D, H) of the object such as width W, depth D and height H. Based on a change in the central position (X, Y, Z) with the passage of time, further, a relative speed (Vx, Vy, Vz) of the object is calculated with the position of the subject (own) vehicle as a reference. The object recognition block 43 further discriminates whether the object is at rest or is moving relying upon the vehicle speed (speed of the subject vehicle) output from the vehicle speed calculation block 47 based on the value detected by the vehicle sensor 7 and upon the relative speed (Vx, Vy, Vz) calculated above. Based on the result of discrimination and the central position of the object, objects are selected that affect the traveling of the subject vehicle, and the distances are displayed on the distance display unit 15.
Further, based on a signal from the steering sensor 27, a steering angle calculation block 49 calculates a steering angle and based upon a signal from the yaw-rate sensor 28, a yaw-rate calculation block 51 calculates a yaw-rate. Further, a curve radius (radius of curvature) calculation block 57 calculates a radius of curve (radius of curvature) R based on the vehicle speed from the vehicle speed operation block 47, steering angle from the steering angle calculation block 49 and yaw-rate from the yaw-rate calculation block 51. Based on the curve radius R, central position coordinate (X, Z), etc., the object recognition block 43 determines the probability in that the object is a vehicle and the probability in that the object is traveling in the same lane as the subject vehicle. An abnormal sensor detector block 44 detects any abnormal value of data calculated by the object recognition block 43. When the data have abnormal values, this fact is displayed on the abnormality indicator unit 17.
A block 53 for determining a preceding vehicle selects the preceding vehicle based on a variety of data obtained from the object recognition block 43, and calculates a distance Z to the preceding vehicle in the direction of Z-axis and a relative speed Vz. Then, a block 55 for controlling the inter-vehicle distance and for determining the alarm, determines whether an alarm be produced when it is the alarm determination or determines the content of vehicle speed control when it is the cruise determination, based on the distance Z to the preceding vehicle, relative speed Vz, preset state of the cruise control switch 26, state in which the brake switch 9 is depressed, position from the throttle position sensor 11 and a sensitivity setpoint by the alarm sensitivity setting unit 25. When the alarm must be produced, an alarm generating signal is output to the alarm sound generator 13. When it is the cruise determination, control signals are sent to the automatic transmission control unit 23, to the brake actuator 19 and to the throttle actuator 21 to effect the required control operations. When these control operations are executed, required display signals are output to the distance display unit 15 to notify the conditions to the driver.
According to the radar device 5 of this embodiment, the peak waveform is not picked up by subtracting the background noise as in the prior art. Instead, the shape of waveform of the integrated signal is determined to directly pick up the peak waveform. This suppresses the three problems ([Problem 1] the level of background noise fluctuates; [Problem 2]a peak waveform to which a plurality of peaks are attached is regarded to be a mass of peak waveform; [Problem 3] when the second signal reflected by another object is received just after the receipt of the first reflection signal having a high peak intensity, the peak waveform of the second reflected signal is not detected) which are inherent in the prior art. It is therefore made possible to suitably pick up the peak waves of the reflecting objects. The above embodiment may be modified as follows.
The method of picking up the peak waveforms of the above embodiment may be combined with a method of picking up the peak waveforms using background noise disclosed in US 2005/0200833.
A background write determining unit 96 of
The background noise storing unit 97 stores an integrated signal of when there is no reflecting object, which corresponds to background noise. The differential processing unit 98, executes the processing for removing the background noise stored in the background noise storing unit 97 from the integrated signal of when there is a reflecting object, and outputs the integrated signal from which the noise has been removed to the distance calculation unit 94.
When the result of determination that a reflecting object is present for a predetermined period of time is output from the background write determining unit 96 or when the user has instructed to return back to the embodiment of the invention by using a switch (not shown in
By employing the method of picking up the peak waveform of this embodiment in combination with the method of picking up the peak waveform using the background noise as described above, the method of picking up the peak waveform of this embodiment can be used as temporary means in a situation (traffic jamming) where the background noise cannot be measured.
The above embodiment has dealt with an example of integrating the received light signals based on a plurality of laser beams radiated neighboring one another among the scanning lies scanned in the direction of X-axis. However, a predetermined number of received light signals may be integrated within a predetermined period of time, that are output based on the transmission waves radiated over a predetermined angle. In this case, too, the signal components corresponding to the waves reflected by the reflecting object are amplified. Here, however, random noise components that are superposed on the received light signals due to various factors are amplified to a small degree. Therefore, the integrated signals feature an improved S/N ratio of the received signal components to the waves reflected by the reflecting object.
In the above embodiment, the integration processing unit 88 has shifted the range of the received light signals to be integrated by one received light signal each time. However, the range of the received light signals to be integrated may be shifted each time by a plurality of received signals which is not larger than the number of the received light signals to be integrated. In this case, too, the resolution for detecting the integrated signals can be improved as compared to when the received signals are, at least, grouped in a predetermined number to calculate an integrated signal therefrom.
The above embodiment has dealt with an example of integrating the received light signals based on a plurality of laser beams radiated neighboring one another among the scanning lies scanned in the direction of X-axis. However, the received light signals to be integrated are not limited to those of the laser beams radiated neighboring one another in the X-axis direction but may be those of the laser beams radiated neighboring one another in the Y-axis direction. Further, the range of laser beams radiated neighboring one another may cover a plurality of scanning lines in the directions of X-axis and Y-axis.
The above embodiment uses the polygonal mirror 73 having different plane tilting angles for two-dimensionally scanning the laser beams. However, this can similarly be realized even by using a galvano-mirror capable of effecting the scanning in the direction of the vehicle width and by using a mechanism capable of varying the tilting angle of the mirror surface. However, the polygonal mirror 73 offers an advantage of realizing the two-dimensional scanning by simply turning it.
In the above embodiment, the distance and the corresponding scanning angles θx and θy are converted in the laser radar sensor 5 from the polar coordinate system into an XYZ rectangular coordinate system. However, the processing may be executed by the object recognition block 43.
The above embodiment has employed the laser radar sensor 5 using a laser beam. However, it is also allowable to use electromagnetic waves such as millimeter waves or ultrasonic waves. However, there is no need to stick to the scanning system only, and there may be employed any system for measuring the azimuth in addition to the distance. When there is used, for example, an FMCW radar or a Doppler radar with millimeter waves, there are obtained the data of distance to the preceding vehicle and the data of relative speed of the preceding vehicle at one time from the reflected waves (received waves). Therefore, no step is necessary for calculating the relative speed based on the distance data, that is required when the laser beams are used.
In the above embodiment, integrated signals are calculated by integrating a plurality of received light signals in order to detect even those reflecting objects that reflect the laser beam insufficiently. The reflecting objects, however, may be detected based upon the individual received light signals.
The above embodiment has illustrated the case where the radar device was used as a radar device for a vehicle. However, the radar device is not limited for vehicle use only but can be used for detecting, for example, persons invading into predetermined areas.
The above embodiment has illustrated an example of using the scanning system shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-184806 | Jul 2006 | JP | national |
