Travel safety apparatus for vehicle

1. Field of the Invention

The present invention relates to a travel safety apparatus for a vehicle.

Priority is claimed on Japanese Patent Application No. 2005-250886, filed Aug. 31, 2005 and Japanese Patent Application No. 2006-169106, filed Jun. 19, 2006, the contents of which are incorporated herein by reference.

2. Description of Related Art

An apparatus is known for detecting an object around a vehicle for preventing a collision between the object and the vehicle or for reducing damage due to the collision, the apparatus having a plurality of detectors such as a radar and an imaging device and recognizing the object based on detection results of the detectors (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-99907).

In the apparatus of the aforementioned related art, a predetermined approximately sectorial detection assurance range in which a predetermined detecting accuracy is secured is set to each detector. The aforementioned apparatus performs a predetermined recognition processing in accordance with detection conditions such as whether or not the object is in an area which at least two detection assurance ranges cover and whether or not the object is in an area which only one of the assurance ranges covers. In addition, enlargement of each assurance range is sometimes required to determine a possibility of a collision swiftly with respect not only to the object ahead of the vehicle but also an object approaching the vehicle from the side.

However, the center angle of the detection assurance range of the radar is not easy to enlarge, while that of the imaging device can be enlarged, for example by applying a wide-angle lens. This is a cause of complexity in the apparatus constitution and rising cost. In addition, since the imaging device has a shorter assured detecting distance than the radar, the detection reliability of the imaging device tends to decline in accordance with changes of conditions such as weather.

The present invention is made in view of the aforementioned circumstances, and an object thereof is to provide a travel safety apparatus for a vehicle which can perform early detection of an object around the vehicle and swiftly determine whether or not there is a possibility of a collision between the object and the vehicle with high accuracy without enlarging the detection assurance ranges of a plurality of detectors.

A first aspect of the present invention is a travel safety apparatus for a vehicle including: a first object detector having a first detection area defined by a first detection angle, and detecting an object ahead of the vehicle; a second object detector having a second detection area defined by a second detection angle that is smaller than the first detection angle, and detecting an object ahead of the vehicle; a motion state determination unit determining the a motion state of the vehicle; a collision determination unit determining whether there is possibility of collision of an object detected in at least one of the first detection area and the second detection area to the vehicle based on the motion state determined by the motion state determination unit; a controller controlling the vehicle so that a collision is avoided when it is determined by the collision determination unit that there is possibility of collision of the object to the vehicle; and an object identity determination unit determining, when a first object is detected in the first detection area and a second object is detected in the second detection area, whether the first object and the second object are identical, wherein when a first object is detected in the first detection area and a second object is detected in the second detection area, and the first object and the second object are determined identical by the object identity determination unit, the collision determination unit determines whether there is possibility of collision of the first object that is identical with the second object to the vehicle.

The travel safety apparatus for a vehicle of the present invention determines the possibility of a collision between the vehicle and an object when the object detected in the detection area of the first detector is identical to the object detected in the detection area of the second detector. The detection accuracy of the possibility of the collision can therefore be improved.

The object identity determination unit may determine the first object and the second object to be identical when the first object is within a predetermined distance from the second object.

The first detection area may include a first reliable detection area and a first detectable area, and the second detection area may include a second reliable detection area and a second detectable area.

The second detector may be a millimeter-wave radar, and the second detectable area may be a sidelobe of the millimeter-wave radar, and wherein when a first object is detected in the first reliable detection area and a second object is detected in the second detectable area, and the first object and the second object may be determined identical by the object identity determination unit, the collision determination unit may determine whether there is possibility of collision of the first object that is identical with the second object to the vehicle.

In this case, when the object detected in the sidelobe as the predetermined detection pattern and the object detected by the first detector exists within a predetermined distance, the travel safety apparatus determines that these two objects are identical. Therefore, even when the detection reliability of the sidelobe is lower than that of the second reliable detection area, the desired detection accuracy and the reliability of the detection result can be secured by combining the detection result of the first detector with the detection result in the sidelobe. As a result, in addition to the second reliable detection area, the sidelobe can be added to the second detection area and the travel safety apparatus can swiftly determine the possibility of collision between the object not only ahead of the vehicle but also approaching from the side of the vehicle with high accuracy without enlarging the second reliable detection area itself.

The first reliable detection area may be a close area within a predetermined distance from the vehicle and the first detectable area may be a remote area more than the predetermined distance apart from the vehicle, and wherein when a first object is detected in the first detectable area and a second object is detected in the second reliable detection area, and the first object and the second object may be determined identical by the object identity determination unit, the collision determination unit may determine whether there is possibility of collision of the first object that is identical with the second object to the vehicle.

In this case, when the object detected in the remote area and the object detected by the second detector exists within a predetermined distance, the travel safety apparatus determines that these two objects are identical. Therefore, even when the detection reliability of the remote area is lower than that of the close area, the desired detection accuracy and the reliability of the detection result can be secured by combining the detection result of the second detector with the detection result in the remote area. As a result, in addition to the close area, the remote area can be added to the detection area of the first detector and the travel safety apparatus can swiftly determine the possibility of a collision between the object with high accuracy without enlarging the close area itself.

The travel safety apparatus of the present invention may further include a braking device provided in the vehicle, decelerating the vehicle; and an alarm device which outputs an alarm to an occupant of the vehicle, wherein the controller may operate at least one of the alarm device and the braking device at a predetermined first timing, based on the determination result of the collision determination unit.

In this case, the alarm device and/or the braking device of the vehicle can be operated with proper timing.

The second detector may be a millimeter-wave radar, and wherein the controller may operate at least one of the alarm device and the braking device at a predetermined second timing which is later than the first timing, when the second object is detected and the first object is not detected.

In this case, when only the millimeter-wave radar detects the object, the position detection accuracy is lower than when only the first detector such as a plurality of cameras detects the object or when both of the radar and the first detector detect the object. Then the travel safety apparatus determines the reliability of the collision determination result to be low and delays the operation timing of alarming and/or deceleration and the alarming and/or deceleration at improper timing can be prevented.

The first detector may be at least one camera, and wherein the controller may set a second deceleration degree greater than a first deceleration degree in normal operation to the braking device when the camera has detected the first object for a predetermined period of time.

In this case, if the object is continuously detected only by the cameras for a predetermined period of time, the safety apparatus determines that the reliability of the collision determination result is higher than before the object is continuously detected. The safety apparatus can perform proper operations for avoiding the collision or reducing the damage due to the collision by setting a greater deceleration degree than that in normal operation.

FIG. 1 is a block diagram showing a constitution of a travel safety apparatus for a vehicle according to an embodiment of the present invention.

FIG. 2 is a diagram showing examples of detection assurance ranges of cameras and a millimeter-wave radar of the vehicle and estimated travel paths of the vehicle and another vehicle if the vehicles maintain their current traveling states.

FIG. 3 is a diagram showing examples of the detection assurance ranges of the cameras and the millimeter-wave radar, and the detectable area of the radar.

FIG. 4 is a diagram showing examples of the detection assurance ranges of the cameras and the radar, and a sidelobe of the radar.

FIG. 5 is a diagram showing examples of detection patterns of the millimeter-wave reception level in regions of the detection assurance range and the detectable area of the radar, in which the regions are divided along an angular orientation.

FIG. 6 is a diagram showing examples of the detection assurance ranges of the cameras and the millimeter-wave radar, and a detectable area of the cameras.

FIG. 7 is a diagram showing an overlap amount.

FIG. 8 is a flowchart showing operations of the travel safety apparatus of the present embodiment.

FIG. 9 is a flowchart showing a flag value determination subroutine in S05 shown in FIG. 8 .

A travel safety apparatus of an embodiment of the present invention shall be described with reference to the accompanying drawings.

As shown in FIG. 1 , a travel safety apparatus 10 of the present embodiment is mounted in a vehicle that transmits drive power from an internal-combustion engine 11 to the drive wheels of the vehicle by means of a transmission (T/M) 12 such as an automatic transmission (AT) or a continuously variable transmission (CVT), and has a constitution provided with a processing unit 13 , a brake actuator 14 , an external sensor 15 , a vehicle state sensor 16 , an EPS actuator 17 , and an alarm device 18 .

The external sensor 15 has a constitution provided with a pair of cameras (hereinafter, simply referred to as “cameras”) including a CCD camera or CMOS camera capable of performing imaging in the visible-light region and infrared region, an image processing device, a beam-scan type millimeter-wave radar, and a radar controller.

The image processing device performs specific image processing such as filtering and binarization of external images ahead of the vehicle obtained by imaging of the cameras, generates a pair of image data consisting of two-dimensionally arranged pixels, and outputs the image data to the processing unit 13 .

In addition, the radar controller divides its approximately-sectorial detecting area set ahead of the vehicle into a plurality of regions along its center angular orientation. The radar controller emits a millimeter-wave transmission signal from the radar so as to scan each region and receives a reflected signal produced by the transmission signal being reflected by an object external to the vehicle. The controller generates a beat signal by mixing the reflected signal and the transmission signal and outputs the beat signal to the processing unit 13 .

Detection assurance ranges of the cameras and the millimeter-wave radar are detection areas in which a predetermined detecting accuracy is secured, and are set so as to partly overlap each other.

For example, a detection assurance range α 1 (a reliable detection area) having a predetermined angular range θ α (e.g., 90° (45° to left and right from the center in the width direction of the vehicle)) and a predetermined distance L α (e.g., 50 m from the cameras provided upper side in the vehicle cabin near the windshield at a predetermined interval in the width direction) is set to the cameras.

A detection assurance range β 1 having a predetermined angular range θ β (e.g., 30° (15° to left and right from the center in the width direction of the vehicle)) and a predetermined distance L β (e.g., 120 m from the millimeter-wave radar provided at the nose of the vehicle body) is set to the radar. As described, θ α is greater than θ β and L α is shorter than L β in this embodiment.

A region in which the assurance ranges α 1 and β 1 overlap each other is set as a first overlapping region γ 1 .

As shown in FIGS. 3 and 4 , a predetermined detectable range β 2 (a detectable area) and sidelobes β 3 (another detectable area) are set to the millimeter-wave radar as regions in which the objects can be detected at a detecting accuracy (for example, angular accuracy with respect to the position of the object) lower than in the assurance range β 1 . The detectable range β 2 is set to be adjacent to both ends of the assurance range β 1 within the angular range θ α .

As shown in FIG. 5 , millimeter-wave reception levels of the plurality of regions divided along the angular orientation (e.g., channels 1 to 5 ) show a predetermined pattern in the assurance range β 1 , the pattern in which the reception level is the highest in the center in the angular orientation (e.g., channel 3 ), decreasing to an end (e.g., channel 1 or 5 ). On the other hand, the detectable range β 2 shows another predetermined pattern in which the reception level is the highest in one end adjacent to the assurance range β 1 (e.g., channel 1 ), decreasing to the other end (e.g., channel 5 ).

A region in which the assurance range αl and the detectable range β 2 overlap each other is set as a second overlapping region γ 2 and a region in which the assurance ranges α 1 and the sidelobe β 3 overlap each other is set as a third overlapping region γ 3 .

As shown in FIG. 6 , a predetermined detectable range α 2 (a detectable area) is set to the cameras as a region in which the objects can be detected at a detecting accuracy (for example, distance accuracy with respect to the position of the object) lower than in the assurance range α 1 . The detectable range α 2 is adjacent to the assurance range α 1 and is located at a distance further than L α (e.g., 50 m to 67 m away from the cameras).

A region in which the assurance range β 1 and the detectable range α 2 overlap each other is set as a fourth overlapping region γ 4 .

The vehicle state sensor 16 has a constitution provided with a velocity sensor that detects the velocity of the vehicle (vehicle velocity); a yaw rate sensor that detects a yaw angle (angle of rotation of the vehicle's center of gravity about the vertical axis) and a yaw rate (angular velocity of the vehicle's center of gravity about the vertical axis); a steering angle sensor that detects a steering angle (magnitude in the direction of steering angle input by the driver) and the actual steering angle corresponding to the steering angle; a position sensor that detects the present position and travel direction of the vehicle based on a positioning signal such as a global positioning system (GPS) signal that measures the position of a vehicle using a satellite and a position signal transmitted from an information transmitter on the exterior of the vehicle, and moreover the detection result of an appropriate gyro sensor and acceleration sensor; and sensors for detecting the ON/OFF state of the direction indicators and brakes, as vehicle information of the vehicle.

The constitution of the processing unit 13 shall be described hereinbelow. An object position detection device 21 detects an object, such as another vehicle, present in the detecting areas of the cameras or the radar in the traveling direction of the vehicle based on the image data or beat signal input from the external sensor 15 , and calculates the position of the object. For example, the detection device 21 performs a predetermined recognition processing on the image data input from the image processing device of the external sensor 15 and measures the distance to the object by triangulation or the like based on the distance between the cameras provided in the vehicle cabin and the parallax of the object in the pair of image data obtained by the cameras.

The detection device 21 detects the position of the object by selecting the image data obtained by the cameras or the beat signal of the millimeter-wave radar in accordance with the detecting area where the object is detected. For example, when the object is detected in an area other than the overlapping regions γ 1 to γ 4 , that is, only the radar or the cameras detect the objects, the detection device 21 detects based on the corresponding detection result.

When the object is detected in the overlapping regions γ 1 to γ 4 , the detection device 21 selects a detection result of higher reliability based on the reliabilities of position parameters (such as distance and angular orientation) calculated based on each detection result. For example, the distance between the vehicle and the object, and the temporal change of the location of the object are calculated based on the beat signal of the millimeter-wave radar and the angular orientation of the position of the object, and its width dimension is calculated based on the image data of the cameras.

The detection device 21 also determines whether or not the object detected by the cameras and the object detected by the radar are the same when the object is detected in the regions γ 1 to γ 4 . For example as shown in FIGS. 3 , 4 , and 6 , the detection device 21 determines that the aforementioned two objects are identical if the distance between the position of the object F α determined by performing a predetermined processing on the image data obtained by the cameras and the position of the object F β detected in the predetermined pattern of the millimeter wave reception level based on the beat signal is not greater than a predetermined length in the longitudinal direction of the vehicle (e.g., 1 m or 3 m) and not greater than a predetermined length in the width direction of the vehicle (e.g., 2 m in oncoming vehicles and 5 m in crossing vehicles or 3 m in all vehicles).

An object velocity measuring device 22 measures the velocity of the object (the relative velocity of the vehicle or the absolute velocity) based on the temporal change of the location of the object detected by the object position detection device 21 . Even when the detection device 21 determines that the object detected by the cameras and the object detected by the radar in the regions γ 1 to γ 4 are identical, the measuring device 22 determines that the aforementioned two objects are not identical if the difference between the velocity of the object calculated based on the image data and the velocity of the object calculated based on the beat signal is not less than a predetermined value (e.g., 3 km/h) or if the moving orientation of each detection result varies by more than a predetermined extent.

An object travel path estimating device 23 estimates the travel path of the object (e.g., an estimated travel path QR of the object Q shown in FIG. 2 ) based on the change of the object position detected by the detection device 21 and the velocity of the object measured by the measuring device 22 .

A vehicle travel path estimating device 24 estimates the travel path of the vehicle (e.g., an estimated travel path PR of the vehicle P shown in FIG. 2 ) based on the temporal change of the vehicle position detected by the vehicle state sensor 16 , the running state of the vehicle, such as the velocity of the vehicle detected by the vehicle velocity sensor, and the yaw rate of the vehicle as detected by the yaw rate sensor.

A collision determination device 25 determines whether or not there is a possibility of the vehicle and the object coming into contact or colliding based on the velocity of the object input from the measuring device 22 , the travel path of the object input from the estimating device 23 , the travel path of the vehicle input from the estimating device 24 , and the position and the velocity of the vehicle measured by the vehicle state sensor 16 .

As shown in FIG. 2 , the collision determination device 25 estimates an arrival time TR (time to a collision) required for the vehicle P to arrive at a predicted collision region O, which is the region where the estimated travel path PR of the vehicle P and the estimated travel path QR of the object Q intersect.

Then the determination device 25 calculates an overlap amount LR, which is shown in FIG. 7 , between the estimated travel path QR and the vehicle P in the direction along the width direction of the path QR when the vehicle P has traveled for the arrival time TR (indicated by a reference numeral P 1 in FIG. 7 ) in the state of having maintained its present driving state (for example, its current velocity and the like). If there is no overlap between the path QR and the vehicle P 1 , the overlap amount LR becomes zero or a negative value.

When the overlap amount LR is greater than zero, the determination device 25 determines there to be a possibility of the vehicle P and the object coming into contact.

A traveling controller 26 is adapted to set at least one of timing and content of traveling control (e.g., degree of deceleration) for controlling the travel state of the vehicle so as to avoid a collision between the object and the vehicle or to reduce the damage due to a collision, in accordance with the object detecting conditions in detecting areas of the cameras and the radar of the external sensor 15 in addition to the determination result of the collision determination device 25 . The traveling controller 26 outputs a control signal to control the drive power of the internal combustion engine 11 , a control signal to control shifting of the transmission 12 , a control signal to control deceleration by the brake actuator 14 , and a control signal to control the steering of the vehicle by the steering mechanism (not illustrated) by the EPS actuator 17 to execute acceleration control, deceleration control, or steering control of the vehicle in accordance with the content set by the controller 26 itself.

An alarm controller 27 is adapted to set at least one of timing and content of an outputting alarm in accordance with the object detecting conditions in detecting areas of the cameras and the radar in addition to the determination result of the collision determination device 25 .

The alarm device 18 has a constitution including a tactual alarming device, a visual alarming device, and an audible alarming device.

The tactual alarming device such as a seatbelt or a steering controller notifies an occupant of the vehicle of the possibility of a collision by generating a fastening force that is tactually perceivable by the occupant with generation of a predetermined tension to the seatbelt, or by generating vibration (steering vibration), to a steering wheel for example, that is tactually perceivable by the occupant.

The visual alarming device such as a display notifies the occupant of the possibility of a collision by displaying a predetermined alarm message on the display, or by flashing a predetermined warning light in accordance with a control signal transmitted from the alarm controller 27 .

The audible alarming device such as a speaker notifies the occupant of the possibility of a collision by outputting a predetermined alarm sound or alarm voice in accordance with a control signal transmitted from the alarm controller 27 .

The vehicle travel safety apparatus 10 of the present embodiment has the aforementioned constitution and the operation thereof shall next be described.

In step S 01 shown in FIG. 8 , the processing unit 13 obtains parameters about the vehicle state such as the position and the traveling state (such as vehicle velocity and the yaw rate) of the vehicle detected by the vehicle state sensor 16 .

In step S 02 , the vehicle travel path estimating device 24 estimates the travel path of the vehicle based on the vehicle state obtained in step S 01 . In addition, the object travel path estimating device 23 estimates the travel path of the object based on the change of the object position detected by the object position detection device 21 and the velocity of the object measured by the object velocity measuring device 22 .

In step S 03 , the collision determination device 25 estimates the arrival time TR (time to a collision) required for the vehicle to arrive at the predicted collision region where the estimated travel paths of the vehicle and the object intersect.

In step S 04 , the determination device 25 calculates the overlap amount between the estimated travel path of the object and the vehicle in the direction along the width direction of the estimated travel path of the object when the vehicle has traveled for the arrival time in the state of having maintained its present drive state, and determines whether or not there is a possibility of the vehicle and the object coming into contact by determining whether or not the overlap amount is greater than zero.

If the determination result is “NO”, the operation is terminated. If the determination result is “YES”, the process proceeds to step S 05 .

In step S 05 , a flag value of a determination flag F is set based on a flag value determination subroutine shown in FIG. 9 . In step S 101 , the determination device 25 sets a provisional flag value in accordance with the object detecting conditions in detecting areas of the pair of the cameras and the millimeter-wave radar of the external sensor 15 . For example, the provisional flag value is set as “01” when the object is detected only in the detection assurance range α 1 of the cameras, the provisional flag value is set as “10” when the object is detected only in the detection assurance range β 1 of the radar, and the provisional flag value is set as “11” when the object is detected in the first overlapping region γ 1 where the assurance ranges α 1 and β 1 overlap each other. In addition, the provisional flag value is set as “100” when the object is detected in the second and third overlapping regions γ 2 and γ 3 , and the provisional flag value is set as “101” when the object is detected in the fourth overlapping regions γ 4 where the detectable range α 2 and the assurance range β 2 overlap each other.

In step S 102 , the determination device 25 determines whether or not the provisional flag value is “11”. If the determination result is “NO”, the process proceeds to step S 103 . If the determination result is “YES”, the process proceeds to step S 106 , which will be described later.

In step S 103 , the determination device 25 determines whether or not the provisional flag value is “100”. If the determination result is “NO”, the process proceeds to step S 104 . If the determination result is “YES”, the process proceeds to step S 111 , which will be described later.

In step S 104 , the determination device 25 determines whether or not the provisional flag value is “101”. If the determination result is “NO”, which means the provisional flag value is “01” or “10”, the process proceeds to step S 105 , the provisional flag value is set as a fixed flag value, and the subroutine is terminated. If the determination result is “YES”, the process proceeds to step S 114 , which will be described later.

In step S 106 , the determination device 25 determines whether or not the object detected by the cameras and the object detected by the radar are identical in the aforementioned manner. If the determination result is “YES”, the process proceeds to step S 107 , the flag value is fixed as “11”, and the subroutine is terminated. If the determination result is “NO”, the process proceeds to step S 108 .

In step S 108 , the determination device 25 determines whether or not the object detected by the cameras has higher risk of collision than the object detected by the radar. If the determination result is “YES”, the process proceeds to step S 109 , the flag value is fixed as “01”, and the subroutine is terminated. If the determination result is “NO”, the process proceeds to step S 110 , the flag value is fixed as “10”, and the subroutine is terminated.

In step S 111 , the determination device 25 determines whether or not the object detected by the cameras and the object detected by the radar are identical in the aforementioned manner. If the determination result is “YES”, the process proceeds to step S 112 , the flag value is fixed as “100”, and the subroutine is terminated. If the determination result is “NO”, the process proceeds to step S 113 , the flag value is fixed as “01”, and the subroutine is terminated. Because the object detected by the cameras is more reliable than the object detected by the radar in this case.

In step S 114 , the determination device 25 determines whether or not the object detected by the cameras and the object detected by the radar are identical in the aforementioned manner. If the determination result is “YES”, the process proceeds to step S 115 , the flag value is fixed as “101”, and the subroutine is terminated. If the determination result is “NO”, the process proceeds to step S 116 , the flag value is fixed as “10”, and the subroutine is terminated. Because the object detected by the radar is more reliable than the object detected by the cameras in this case.

The flag value “100” indicates that the object is detected in a state in which the position detection accuracy of the millimeter-wave radar in angular orientation is low and the flag value “101” indicates that the object is detected in a state in which the position detection accuracy of the cameras is low while a desired position detection accuracy of the radar in distance orientation is secured. In this condition, the detection accuracy of the cameras can be improved by changing the imaging condition such as various parameters in stereomatching in accordance with the detection result of the radar.

In step S 06 , the determination device 25 sets a first operation-timing determination threshold Ta for outputting the alarm and weak deceleration and a second operation-timing determination threshold Tb for strong deceleration based on a predetermined first operation-timing determination reference value T 1 and second operation-timing determination reference value T 2 (e.g., T 1 >T 2 , T 1 is 2 seconds, and T 2 is 1 second), and a predetermined adjustment time T 0 (e.g., 0.3 seconds), in accordance with each flag value of the determination flag F as shown in Table 1.

In the flag value “10” shown in Table 1, indicating that the object is detected only in the assurance range β 1 , the determination thresholds Ta and Tb are set to be shorter than in other flag values in which the object is detected in at least one of the assurance range α 1 and the detectable range α 2 by the length of the adjustment time T 0 .

That is, the operation timing of alarming and deceleration is delayed by the length of the adjustment time T 0 when the object is only detected by the radar because the position detection accuracy is relatively low, especially in its angular orientation. The travel safety apparatus of the present embodiment is therefore adapted to perform alarming and deceleration after the detection accuracy in the angular direction increases by the delay.

In step S 07 , the traveling controller 26 and the alarm controller 27 determine whether or not the arrival time TR is equal to or smaller than the first determination threshold Ta.

If the determination result is “NO”, the operation is terminated. If the determination result is “YES”, the process proceeds to step S 08 . In step S 08 , the alarm controller 27 performs alarming and the controller 26 performs deceleration at a first deceleration degree Ga (e.g., 0.15 G, 1 G=9.8 m/s 2 ) by the brake actuator 14 .

In step S 09 , the traveling controller 26 and the alarm controller 27 determine whether or not the arrival time TR is equal to or smaller than the second determination threshold Tb.

If the determination result is “NO”, the operation is terminated. If the determination result is “YES”, the process proceeds to step S 10 .

In step S 110 , the controller 26 determines whether or not the flag value of the determination flag F is other than “01”.

If the determination result is “NO”, which means that the object is only detected by the cameras, the process proceeds to step S 13 , which will be described later.

If the determination result is “YES”, which means that the object is detected in at least one of the assurance range β 1 , the detectable range β 2 , and the sidelobe β 3 , the reliability of the detection result is determined to be relatively high, the process proceeds to step S 11 .

In step S 11 , the alarm controller 27 performs alarming and the controller 26 performs deceleration at a second deceleration degree Gb (e.g., 0.6 G) which is greater than the first deceleration degree Ga by the brake actuator 14 .

In step S 12 , the controller 26 stops deceleration after a predetermined period (e.g., 1 second), and terminates the operation.

In step S 13 , the controller 26 determines whether or not a tracking number SR of the cameras performing detection of the object at predetermined intervals (e.g., 33 milliseconds) is not greater than a predetermined number S (the number at which a desired detection reliability is secured, e.g., 15).

If the determination result is “NO”, which means the object is continuously detected with the desired reliability, the process proceeds to aforementioned step S 11 .

On the other hand, if the determination result is “YES”, which means the object is not continuously detected with the desired reliability, the reliability of the detection result is determined to be low and the process proceeds to step S 14 .

In step S 14 , the controller 26 performs alarming and deceleration at the first deceleration degree Ga by the brake actuator 14 .

In step S 15 , the controller 26 stops deceleration after the predetermined period (e.g., 1 second), and terminates the operation.

As described above, the travel safety apparatus 10 for a vehicle of the present embodiment determines the possibility of a collision between the vehicle and the object in accordance with the determination result as to whether or not the object detected in the detecting area of the pair of cameras is the same as the object detected in the detecting area of the millimeter-wave radar, in which the detecting area has a narrower angular range than the area of the cameras. The detection accuracy of the possibility of a collision therefore can be improved.

When the object detected in the detectable range β 2 or the sidelobe β 3 of the radar as the predetermined detection pattern and the object detected by the cameras exist within a predetermined distance, the travel safety apparatus determines that these two objects are identical with reliability. That is, even when the detection reliability of the detectable range β 2 and the sidelobe β 3 is lower than that of the assurance range β 1 , the desired detection accuracy and the reliability of the detection result can be secured by combining the detection result of the cameras with the detection result in the detectable range β 2 and the sidelobe β 3 for identity determination. Due to the identity determination, in addition to the assurance range β 1 , the detectable range β 2 and/or the sidelobe β 3 can be added to the detecting area of the millimeter-wave radar and the travel safety apparatus can swiftly determine the possibility of the collision between the object not only ahead of the vehicle but also approaching from the side of the vehicle at a high accuracy without enlarging the assurance range β 1 itself.

Furthermore, when the object detected in the detectable range α 2 of the cameras, the range existing further than the assurance range α 1 , and the object detected by the radar exist within a predetermined distance, the travel safety apparatus determines that these two objects are identical with reliability. That is, even when the detection reliability of the detectable range α 2 is lower than that of the assurance range α 1 , the desired detection accuracy and the reliability of the detection result can be secured by combining the detection result of the millimeter-wave radar with the detection result in the detectable range α 2 for identity determination. Due to the identity determination, in addition to the assurance range α 1 , the detectable range α 2 can be added to the detecting area of the cameras and the travel safety apparatus can swiftly determine the possibility of a collision between the object with high accuracy without enlarging the assurance range α 1 itself.

When only the millimeter-wave radar detects the object, the position detection accuracy is lower than when only the cameras detect the object or when both of the radar and the cameras detect the object, especially in the angular orientation. Then the travel safety apparatus determines the reliability of the collision determination result to be low and delays the operation timing of alarming and deceleration. Since the alarming and deceleration are performed after the position detection accuracy of the radar in the angular orientation increases by the delay, the alarming and deceleration at improper timing can be avoided.

If the object is continuously detected only by the cameras for a predetermined period of time, the safety apparatus determines that the reliability of the collision determination result is higher than before the object is continuously detected. The safety apparatus can perform proper operations for avoiding a collision or reducing the damage due to a collision by decelerating at the relatively greater second deceleration degree Gb.

In the present embodiment, deceleration degrees are set in accordance with whether or not the object is detected only by the cameras as shown in step S 10 . However, it is not limited thereto and deceleration degrees may be set in accordance with changes of the object detection conditions.

For example, as shown in FIG. 2 , the flag value of the determination flag F set to the other vehicle Q crossing ahead of the vehicle P changes from “01” to other than “01”, and again changes into “01”. In this case, the deceleration degree may be set as the second degree Gb from the first degree Ga when the flag value changes from “01” to other than “01”. In addition, the deceleration degree may be maintained as the second degree Gb when the flag value changes from other than “01” to “01” even though the tracking number SR is not greater than the predetermined number S, because the desired detection reliability has been secured just before the change of the flag value. The occupant's sense of discomfort about the traveling of the vehicle thus can be avoided.

Though the pair of the cameras and the millimeter-wave radar are provided in the external sensor 15 in this embodiment, it is not limited thereto. A laser radar may be used instead of the cameras or the millimeter-wave radar.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.