Radar apparatus installed on vehicle for managing reflector information

Abstract: A radar apparatus installed on a vehicle includes a transmission section (10, 20, 30), a reception section (10, 40) and a processing section (50). The transmission section includes at least a transmission antenna, and emits transmission wave toward a detection area in a front of the vehicle. The transmission wave is reflected by a reflector to produce reflection wave, and the detection area includes a plurality of sub-areas. The reception section includes at least a reception antenna, and receives and detects the reflection wave. The processing unit detects a reflector indication data indicative of a reflector attribute based on the detecting result by the reception section, and then determines whether there is the reflector in the detection area, based on the reflector indication data. Also, the processing section manages the reflector indication data over a management area which is wider than the detection area.

Description: The present invention relates to a radar apparatus installed on a vehicle which permits detection of reflector objects such as a preceding vehicle or an obstacle and management of information indicative of the detected reflector. Radar systems installed on a vehicle can be used as tracking systems for tracking preceding vehicles and alarm systems for preventing collisions. A radar beam, typically a microwave beam in the millimeter range or a laser beam, is radiated from the radar system. When a reflector object is present in the field of view of the radar system the emitted beam is reflected. Reflection waves received from the reflector then allow to obtain information about the reflector. For application to vehicles it is conventionally known to use FM radar systems which transmit frequency modulated waves, AM radar systems which transmit amplitude modulated waves or pulse radar systems. In order to monitor a region in front of a vehicle it is known to mechanically scan a sharp radar beam over a predetermined angle range, or to successively emit sharp radar beams from a plurality of antennas which are arranged at slightly different antenna directions from each other. By processing the data acquired in scanning the region in front of the vehicle, information on the azimuth position and the distance of the reflector can be obtained. In the Japanese Patent No. 2567332 a time division radar system is disclosed in which a radar beam is electronically scanned and a weighting and averaging operation is performed in accordance with the reception level of the reflected waves. As the resolutions of distance and azimuth angle improved, vehicle radar systems have been developed wherein the detection area (field of view) in front of the vehicle is divided in distance and in azimuth angle (width) into meshes so as to form sub-areas of a two-dimensional structure. In these radar systems, reflector objects such as a preceding vehicle are detected over the sub-areas. One example of a radar system which has its field of view divided in distance and in azimuth angle into sub-areas is disclosed in the Japanese Laid-Open Patent Application JP-A-5-180934. In this known radar system, a group of continuous sub-areas in which reflection waves are detected is considered to represent a single reflector object. Movement in the detected sub-areas is managed so as to detect the relative velocity between the own vehicle and the reflector. The reflector (detection object) is managed only in the field of view of the radar apparatus. When the reflector is detected in a center portion of the field of view, perfect data on the shape of the reflector can then be obtained within the tolerance limits of the spatial resolution. However, when the reflector is detected in a peripheral portion of the field of view of the radar apparatus, only imperfect data can be obtained on the shape of the reflector due to lack of data for a portion outside this field of view. Therefore, when an object which initially has been detected in the center portion of the field of view of the radar apparatus is about to leave the field of view, the quality of the data on the center position and width, formerly perfect, is getting lost. The same problem applies to a vehicle radar system known from US 5668739 A. In this known system, object data on an object being tracked are managed only over the field of view of the radar system as well. It is therefore an object of the present invention to overcome the above problem and to permit tracking a detected reflector object even when this object is about to leave the detection area or field of view of the radar system. In order to achieve the above object, there is provided in a first aspect of the present invention a radar apparatus according to claim 1. In a further aspect, the present invention provides a method of operating a radar apparatus according to claim 15. Preferred embodiments of the inventive apparatus and method are given in the dependent subclaims. A preferred embodiment of the radar apparatus of the present invention and its way of operating will be described below in detail with reference to the attached drawings. In the drawings: Fig. 1 is a block diagram illustrating the structure of a radar apparatus installed on a vehicle according to an embodiment of the present invention; Fig. 2 is a conceptual diagram to explain the relation between a detection area and a management area in the radar apparatus according to the embodiment of Fig. 1; Fig. 3 is a conceptual diagram to explain a method of detecting and managing the center position and width of a reflector by the radar apparatus in the above embodiment; Fig. 4 is another conceptual diagram to explain the method of detecting and managing the center position and width of the reflector by the radar apparatus in the above embodiment; Fig. 5 is a conceptual diagram to explain the method of detecting and managing the center position and width of the reflector by the radar apparatus in the above embodiment; and Fig. 6 is a conceptual diagram to explain the method of detecting and managing the center position and width of the reflector by the radar apparatus in the above embodiment. Fig. 1 is a block diagram illustrating the structure of a radar apparatus installed on a vehicle according to an embodiment of the present invention. The radar apparatus is composed of a transmission and reception antenna section 10, an FM signal generating circuit 20, a transmission section 30, a reception section 40, and a detection and control section 50. The transmission and reception antenna section 10 is composed of transmission antennas 11a to 11e and reception antennas 12a to 12e. Five sets of transmission antenna and reception antenna correspond to transmission and reception channels A to E, respectively. The transmission antennas and the reception antennas are formed as a defocus parabolic multi-beam antenna composed of a common parabolic reflecting mirror and a plane array antenna as a primary emitter which is arranged to be opposite to the reflecting mirror in the neighborhood of the focus of this reflecting mirror. The respective transmission antennas 11a to 11e are installed to radiate beams in slightly different directions from each other in azimuth. The reflection waves which are generated from the beams which have been radiated from the respective transmission antennas are received by the reception antennas 12a to 12e. The FM signal generating section 20 is composed of a voltage controlled oscillator (VCO) 21, a sweep circuit 22, and a voltage dividing circuit 23. The sweep circuit 22 supplies a triangular modulation voltage to the voltage controlled oscillator 21 in response to a control signal from the detection and control section 50. The voltage controlled oscillator (VCO) 21 generates a high frequency signal in a submillimeter wave band based on the triangular modulation voltage supplied from the sweep circuit 22. The voltage dividing circuit 23 divides the high frequency signal into two components to be supplied to the transmission section 30 and the reception section 40. The transmission section 30 is composed of a transmission switching circuit 31 and frequency triple increasing circuits 32a to 32e. The transmission switching circuit 31 sequentially supplies the divided component of the high frequency signal to the frequency triple increasing circuits 32a to 32e in response to a timing control signal supplied from the detection and control section 50. Each of the frequency triple increasing circuits 32a to 32e increases the frequency of the divided component of the high frequency signal to 3 times such that a beam is radiated from the corresponding one of the transmission antennas 11a to 11e. Each of the reception antennas 12a to 12e receives a reflection wave to generate a reflection FM signal. The reception section 40 is composed of a station switching circuit 41, frequency triple increasing circuits 42a to 42e, mixers 43a to 43e, and a beat selector 41. The station switching circuit 41 receives the divided component of the high frequency signal from the voltage dividing circuit 23 and sequentially supplies this signal component to the frequency triple increasing circuits 42a to 42e in response to a timing control signal supplied from the detection and control section 50. Each of the frequency triple increasing circuits 42a to 42e increases the frequency of the divided component of the high frequency signal to 3 times and outputs a station FM signal to the corresponding one of the mixers 43a to 43e. Each of the mixers 43a to 43e receives the reflection FM signal and the station FM signal to output a beat signal between the reception FM and the station FM signal to the beat selector 44. The beat selector 44 outputs one of the beat signals supplied from the mixers 43a to 43e in accordance with a timing control signal supplied from the detection and control section 50. The detection and control unit 50 is composed of a CPU 51, an amplifying circuit 52, an analog to digital (A/D) converting circuit 53, a fast Fourier transform circuit (FFT)54, a timing control circuit 55 and a memory (MEM) 56. The amplifying circuit 52 amplifies the selected beat signal outputted from the beat selector 44 and supplies it to the A/D converting circuit 53. The A/D converting circuit 53 converts the amplified beat signal into digital form. The FFT 54 performs fast Fourier transform to the digital beat signal and supplies the transformed signal to the CPU 51. The CPU, based on a software which is stored in the memory 56 performs a detecting and managing process on the spectrum data resulting from the fast Fourier transform to thereby obtain reflector indication data. The CPU 51 stores the reflector indication data in the memory 56. More specifically, the FM signal generating section 20 generates an FM signal having a predetermined voltage level and a center frequency of approximately 20 GHz in the submillimeter wave band and changing straightly in a predetermined period from. The FM signal is approximately equally divided by the voltage dividing circuit 23. One of the divided signal components is supplied to the transmission section 30 and the other is supplied to the reception section 40. In the transmission section 30, the FM signal supplied from the FM signal generating section 20 is distributed to the frequency triple increasing circuits 32a to 2e by the transmission switching circuit 31. Thus, the frequency of the FM signal is increased to 3 times by the corresponding one of the frequency triple increasing circuits 32a to 32e, so that it is converted into a millimeter wave band FM signal in the 60 GHz band. The converted FM signals are supplied to the transmission antennas 11a to 11e in order to be radiated from the respective transmission antennas toward the front of the vehicle. A part of the FM signals which have been radiated from the front of the vehicle through the transmission antennas 11a to lie is reflected by the reflector such as a preceding vehicle, and then is received by the corresponding one of the reception antennas 12a to 12e. Thus, reflection FM signals are generated. The reflection FM signal is supplied to a corresponding one of the mixers 43a to 43e at one of the input terminals. The other input terminal of each of the mixers 43a to 43e is supplied with one of the station FM signals supplied from the FM signal generating section 20. The station FM signal is selected by the station switching circuit 41 at a predetermined timing. The frequency of the selected station FM signal is increased to 3 times by a corresponding one of the frequency triple increasing circuits 42a to 42e, to generate a millimeter wave band station FM signal. Beat signals of the reflection FM signal and the station FM signal are outputted from the mixers 43a to 43e. The beat signals are selected in order by the beat selector 44 for the respective transmission and reception channel and are supplied to the amplifying circuit 52 of the detection and control unit 50. The beat signal is amplified by the amplifying circuit 52 and converted into a digital signal by the analog to digital converting circuit 53, and then is supplied to the fast Fourier transform circuit 54. The beat signal is converted into a frequency spectrum of the beat signal and is supplied to the CPU 51. The CPU 51 detects from the frequency spectrum, reflector indication data indicating a reflector attribute such as the center position and width of the reflector and the azimuth angle to the reflector. Also, the CPU 51 detects the distance to the reflector based on the timing when the beam is radiated and the timing when the reflection wave is received. Further, the CPU 51 controls the timing control circuit 55 to generate various timing control signals, based on which the operations of the various sections in this FM radar apparatus are controlled. Fig. 2 is a conceptual diagram to explain the structure of a management area M. The management area M is composed of a detection area D and peripheral areas Ma and Me. The detection area is formed as an area of a fan type which spreads radially in the front of the vehicle on which this radar apparatus is installed. The detection area D of this fan type is composed of five sub-areas Da, Db, Dc, Dd and De of a thin fan type which have substantially identical shape to each other. The five sub-areas Da, Db. Dc, Dd and De corresponds to the transmission and reception channels A to E, respectively. The FM signal beams are radiated to the five sub-areas Da to De from the transmission antennas 11a to 11e shown in Fig. 1, respectively. The FM signal beam has a width approximately equal to, or slightly wider that of the corresponding sub-area. Also, the reflection wave is generated in the corresponding sub-area and is received by the corresponding one of the reception antennas 12a to 12e. The peripheral areas Ma and Me are formed on both sides of the detection area D and have substantially the same width as a preceding vehicle. The management area M is an area used to manage the movement of the reflector such as the preceding vehicle which has been detected in the detection area D. It is supposed that the reception levels of the reflection FM signals have been detected to be higher than a predetermined threshold value in three continuous sub-areas Db, Dc and Dd. Also, it is supposed that the distances R from the vehicle on which the radar apparatus is installed to the reflector are approximately equal to each other. Here, that the distances to the reflector detected in the respective sub-areas are approximately equal to each other means that a difference between the distances is smaller than a threshold value which has been previously set to the length of a typical vehicle. In this case, the CPU 51 determines that a single reflector exists over the sub-areas Db, Dc and Dd, and determines the center position P of the reflector and the width W of the reflector. In this embodiment, the center position P and the width W are determined as reflector attribute in units of sub-areas. Therefore, the center position P is determined to be the center sub-area Dc. Also, the width of the reflector is determined to be three sub-areas. The reflector indication data such as the center position P and the width W are stored and held in the memory 56. Thus, the movement of the reflector can be managed. In this case, the end portion positions may be detected and stored in the memory 56, in addition to the center position P and the width W. The center position P of the reflector can be expressed as a combination (R, Q) of distance R from the own vehicle and the center position Q of the sub-area. In the example shown in Fig. 2, the center position Q of the sub-area and the width W can be expressed by the following equations (1) and (2). Q = Dcc W = Rsin(  b +  c +  d) where Dcc is the center position of the sub-area Dc (more precisely, an azimuth angle of the center), and b, c, d are the opening angles of the sub-areas Db, Dc and Dd, respectively. As an example, it is supposed that the opening angle of each sub-area is 0.1 degrees and the distance R from the own vehicle is 50 meters. In this case, the width W of the reflector which has been detected over three sub-areas is 2.6 meters. This value is nearly the same as the width of about 2 meters of a typical motorcar. In this case, the reflector is determined to be a single vehicle. Also, when the detected width W of the reflector is larger than a predetermined threshold value, this reflector is determined to be two or more vehicles or a road or a construction. The predetermined threshold value is previously set to a value indicative of the width of a road or the width of a lane. Generally, the size of the transmission and reception antennas is set to a sufficiently small value, compared with the width of the vehicle. Therefore, each sub-area corresponding to the beam of the FM signal radiated from each transmission antenna represents a thin fan shape spreading radially from a point where the transmission and reception antennas are located, as shown in Fig. 2. In this case, considering that the opening angle of each sub-area is as small as 1 degree, the boundaries between the sub-areas can be considered a group of parallel lines. Fig. 3 is a diagram to explain the reflector detecting and managing method for a case in which the detected sub-areas of the reflector which is being managed based on its center position P and width W change with time. The time axis is set to the downward direction in the figure. In this example, the peripheral area He is composed of three sub-areas. In this figure, the state that the reflector moves to the right while the distance R from the own vehicle is kept constant is illustrated. That is, as the time increases from t1 to t2 to t3, the center position P changes from the center position Dcc of the sub-area Dc through the center position Ddc to the center position Dec. In this case, at the time t1, the CPU 51 sets "1" to bits of the memory 56 corresponding to the sub-areas Db, Dc and Dd. Also, at the time t2, the CPU 51 sets "1" to a bit of the memory 56 corresponding to the sub-area De and resets the bit corresponding to the sub-area Db to "0". At the time t3, the CPU 51 sets "1" to a bit of the memory 56 corresponding to the left sub-area of the peripheral area Me and resets the bit corresponding to the sub-area Dc to "0". At time t4, the center position P goes out of the detection area D and at time t5, the whole reflector goes out of the detection area D. At this time, the CPU 51 sets "1" to a bit of the memory 56 corresponding to the center sub-area of the peripheral area Me and resets the bit corresponding to the sub-area Dd to "0". In the example of Fig. 3, as shown at times t3 and t4, even if a part of the reflector goes out of the detection area D, the management of the reflector is continued based on the center position P and the width W, as far as the remaining part of the reflector exists in the detection area D. Also, as shown at time t5, after the whole of the reflector goes out of the detection area D, the reflector is regarded to exist in the peripheral area Me, and is managed for a predetermined time. At this time, the CPU 51 sets "1" to a bit of the memory 56 corresponding to the right sub-area of the peripheral area Me and resets the bit corresponding to the sub-area De to "0". When a part of a reflector comes again into the detection area D at a time t 6 within the predetermined time, a part of the reflector is detected and it is determined that the previously detected reflector has come back. On the other hand, when a part of a reflector comes again into the detection area D at a time t 6 after the predetermined time, it is determined that a new reflector has been detected. At this time, the CPU 51 sets "1" to a bit of the memory 56 corresponding to the sub-area De of the detection area Me and resets the bit corresponding to the right sub-area of the peripheral area Me to "0". Thereafter, the movement of the reflector is managed. The widths of the peripheral areas Ma and Me which are provided on both sides of the detection area D may be previously set to a value corresponding to the width of a road lane or the width of the vehicle. Or, the widths of the peripheral areas Ma and Me may be dynamically set to a value which is equal to the width of the reflector which has been detected in the detection area D. Fig. 4 is a diagram to explain the reflector detecting and managing method for a case where the reflector moves in a direction reverse to that of Fig. 3. That is, at first, a part of the reflector is detected only in the sub-area De at time t1. In this case, the center position P is detected and managed to be equal to the center position Dec of this sub-area De. Also, the width W is detected and managed to be equal to the width of this sub-area De. Subsequently, at time t2, even if the reflector goes out of the detection area D once during this management, the reflector is regarded to exist in the peripheral area and is managed for the predetermined time period. When returning to the detection area D at the time t3 before the above predetermined time elapses, the reflector is determined to be the reflector having the width already detected. In this case, only the center position is updated to the lateral direction. Next, at time t4, when the center position P of the reflector moves toward the center of the detection area D, the width W increases from the width of the sub-area De to the width of the summation of sub-areas De and Dd. In this case, the center position P and the width W are updated to a new center position and a new width. Thereafter, at time t5, the center position of the reflector further moves in the direction of the center of the detection area D, so that the width W increases to the summation of the three continuous sub-areas De, Dd and Dc. In this case, the width is updated to a new increased width together with the center position in lateral direction. Subsequently, at time t6, even if the center position of the reflector moves further to the left direction, the width W does not increase. In this case, only the center position of the reflector in lateral direction is updated to a new value. In this way, the width of the reflector already detected is updated to a new value only when the width of the reflector exceeds the managed value. The description of the bit setting operation by the CPU 51 has been omitted in the foregoing However, this operation is performed similarly to that shown in Fig. 3. In the above description, the detection operation is performed based on whether reflection waves having a reception level higher than the predetermined threshold value are detected, and the reflector width is determined, in units of sub-areas of the detection area D. In this example, the center position of the reflector and the width of the reflector are detected and managed as numerical values. In determinig the center position of the reflector in lateral direction, a weighting and averaging operation in azimuth angle may be used based on the reception level of the reflection wave. Particularly, a weighting and averaging operation in azimuth angle of the centerline of each fan-shaped sub-area can be used. It is supposed that the azimuth angles of the centerlines of the fan-shaped sub-areas are a, b, c, d, and e, and the reception levels of the reflection waves which are received in the sub-areas are La, Lb, Lc, Ld, and Le. In this case, the center position Θ of the reflector in lateral direction can be calculated as the result of the following weighting and averaging operation. Θ = (Laa + Lbb + Lcc + Ldd + Lee)/(La + Lb + Lc + Ld + Le) Fig. 5 shows a case where the reception levels Lb and La of the reflection waves increase monotonously from the sub-area Db of the detection area D to the sub-area Da thereof. In this case, when the center position Θ of the reflector in lateral direction is calculated using the above-mentioned weighting and averaging operation, the center position is calculated to be an intermediate value between the azimuth angles of a and b. However, it is expected that the actual center position of the reflector is in the sub-area Da or the peripheral area Ma. Therefore, in the embodiment of the present invention, an imaginary reception level Lb' of the reflection wave is supplemented at a position symmetrical to the azimuth angle having the reception level Lb with respect to the azimuth angle having the maximum level La, as shown by the dotted line outside the detection area D. As a result, the center position Θ of the reflector (or azimuth angle a) is determined to be in the center Dac of the sub-area Da. Then, the width W of the reflector is detected over three sub-areas having reception levels higher than the predetermined threshold value, including the imaginary reception level These values are managed for the management area Ma including the peripheral area Ma. It is supposed that after the state illustrated in Fig. 5, the reception levels of the reflection waves change with movement of the reflector to the state shown in Fig. 6. That is, the reception levels increase monotonously in order of Lc, Lb, and La to the direction of the peripheral area Ma, as illustrated in Fig. 6. In this case, two imaginary reception levels Lb and Lc of the reflection waves are supplemented at symmetrical positions with respect to the maximum reception level La of the reflection waves, as shown by the dotted lines outside the detection area D. As a result, the center position Θ of the reflector does not change. However, an extension over five sub-areas is detected, and the width is updated based on this new value. As described above, the determination of whether the reception levels of the reflection waves increase monotonously to the direction of the peripheral area is performed by comparing the reception levels over all the sub-areas where the reflection waves are detected. However, the determination may be performed to some having higher ones of the reception levels which are detected to be higher than the predetermined threshold value, instead that the comparing operation is performed to all the sub-areas where reflection waves are detected. Also, the comparing operation may be performed by a simple comparing operation or by a weighting and comparing operation in which suitable coefficients are multiplied with the reception levels. In the above description, the center position and width of the reflector are detected and managed. However, it is possible to detect and manage only one of the center position and width of the reflector. Also, an example has been described above, in which the transmission antenna and the reception antenna are formed as a defocus parabolic multi-beam antenna, which is composed of a common parabolic reflecting mirror and a plane array antenna as a primary emitter arranged in the neighborhood of the focus of this reflecting mirror. However, the radar apparatus may be formed to have a structure, in which a beam is radiated over the whole detection area from a single transmission antenna to have substantially uniform level, and the reflection waves may be received by a plurality of reception antennas having a narrow directivity to cover a corresponding sub-area. On the contrary, the radar apparatus may be formed to have a structure, in which a beam is radiated from a transmission antenna having a narrow directivity to each sub-area, and the reflection waves are received by a single reception antenna having a wide directivity. Moreover, an example of an FM radar apparatus which radiates a frequency modulated wave has been described. However, various other systems can be applied such as an AM radar apparatus which radiates an amplitude modulated wave and receives the reflection wave, or a pulse radar apparatus which radiates an electromagnetic pulse wave and receives the reflection wave, and which detects the distance to the reflector from the time difference between radiation and reception. Moreover, an example has been described, in which millimeter wave band electromagnetic waves are radiated and the reflection waves are received. However, the radar apparatus may alternatively emit microwaves of another frequency, a laser beam or supersonic waves, for example. As described above in detail, the radar apparatus of the present invention has the advantage that, because the position and width of the reflector are managed based on the reception information of the reflection waves from the reflector, the detection of the object is possible in an area which is wider than the actual detection area. When the radar apparatus of the present invention is used for tracking a preceding vehicle, there is an advantage that loss of the preceding vehicle in steep corners is made minimum, and stable tracking drive becomes possible.

Claims: A radar apparatus installed on a vehicle, comprising: a transmission section (10, 20, 30) including transmitting antenna means (11a, 11b, 11e) for emitting transmission waves toward a detection area (D) in front of said vehicle, a reception section (10, 40) including receiving antenna means (12a, 12b, 12e) for receiving reflection waves produced by reflection of said transmission waves by a reflector object, said reception section (10, 40) providing a reception result based on said received reflection waves, and a processing unit (50) responsive to said reception result as provided by said reception section (10, 40) for determining presence of said reflector object within said detection area (D), said processing unit (50) being arranged for generating, based on said reception result, object data indicative of at least one attribute (P, W) of said reflector object and managing said object data to track said reflector object, characterized in that said processing unit (50) is arranged for managing said object data over a management area (M) which is wider than said detection area (D). The radar apparatus according to claim 1, characterized in that said processing unit (50) determines that said reflector object is present in said detection area (D) when a reception level of said reflection waves in at least one of a plurality of sub-areas (Da - De) of said detection area (D) is higher than a predetermined threshold value. The radar apparatus according to claim 2, characterized in that said processing unit (50) is arranged for determining, as a width attribute of said reflector object, an object width (W) in units of said detection sub-areas (Da - De). The radar apparatus according to claim 3, characterized in that said processing unit (50) is arranged for determining said object width (W) based on a number of continuous ones of said detection sub-areas (Da - De) in which said reception level of said reflection waves is higher than said predetermined threshold value, and based on a predetermined width value set for each of said detection sub-areas (Da - De). The radar apparatus according to claim 2, characterized in that said processing unit (50) is arranged for determining a distance to said reflector object based on an emission time of said transmission waves and a reception time of said reflection waves, each of said detection sub-areas (Da - De) having a fan shape with an opening angle, said processing unit (50) being further arranged for calculating a width value for each detection sub-area (Da - De) based on said opening angle and said distance to said reflector object, and for determining, as a width attribute of said reflector object, an object width (W) based on a number of continuous ones of said detection sub-areas (Da - De) in which said reception level of said reflection waves is higher than said predetermined threshold value, and based on said calculated sub-area width values. The radar apparatus according to any one of claims 2 to 5, characterized in that said processing unit (50) is arranged for determining, as a position attribute of said reflector object, an object center position (P) based on continuous ones of said detection sub-areas (Da - De) in which said reception level of said reflection waves is higher than said predetermined threshold value. The radar apparatus according to any one of claims 2 to 6, characterized in that said processing unit (50) is arranged for determining, as a position attribute of said reflector object, an object center position (P) based on reflection wave reception levels (La, Lb, Lc) which exceed said predetermined threshold value in continuous ones (Da, Db, Dc) of said detection sub-areas (Da - De), and based on an azimuth angle (a, b, c) of each of said continuous detection sub-areas (Da, Db, Dc). The radar apparatus according to claim 7, characterized in that said processing unit (50) is arranged for supplementing in said management area (M) at least one imaginary reception level (Lb, Lc) corresponding to said reflection wave reception levels (La, Lb, Lc) higher than said predetermined threshold value, when these reflection wave reception levels (La, Lb, Lc) increase monotonously in said continuous detection sub-areas (Da, Db, Dc), said processing unit (50) being further arranged for determining said object center position (P) based on said reflection wave reception levels (La, Lb, Lc) higher than said predetermined threshold value, said at least one imaginary reception level (Lb, Lc), and said azimuth angle (a, b, c) of each of said continuous detection sub-areas (Da, Db, Dc). The radar apparatus according to any one of claims 2 to 8, characterized in that said processing unit (50) is arranged for determining, as a position attribute of said reflector object, an object center position (P) based on higher ones of reflection wave reception levels exceeding said predetermined threshold value in continuous detection sub-areas, and based on an azimuth angle of each of said detection sub-areas having said higher reflection wave reception level. The radar apparatus according to any one of claims 1 to 9, characterized in that said processing unit (50) is arranged for continuing management of said object data when it is determined that said reflector object has left at least in part said detection area (D), but is present in a peripheral area (Ma, Me) of said management area (M) outside said detection area (D). The radar apparatus according to claim 10, characterized in that said processing unit (50) is arranged for continuing management of said object data when it is determined that said reflector object, after leaving said detection area (D), returns into said detection area (D) within a predetermined time. The radar apparatus according to claim 11, characterized in that said processing unit (50) is arranged for stopping management of said object data when it is determined that said reflector object, after leaving said detection area (D), stays out of said detection area (D) for more than said predetermined time. The radar apparatus according to any one of claims 1 to 12, characterized in that said management area (M) includes said detection area (D) and peripheral areas (Ma, Me) on both sides of said detection area (D), said peripheral areas (Ma, Me) being predetermined in terms of width. The radar apparatus according to any one of claims 1 to 12, characterized in that said management area (M) includes said detection area (D) and peripheral areas (Ma, Me) on both sides of said detection area (D), said processing unit (50) being arranged for setting a width of said peripheral areas (Ma, Me) based on a detected width (W) of said reflector object. A method of operating a radar apparatus installed on a vehicle, comprising the steps of: emitting transmission waves toward a detection area (D) in front of said vehicle, receiving reflection waves produced by reflection of said transmission waves by a reflector object and providing a reception result based on said received reflection waves, based on said reception result, determining presence of said reflector object within said detection area (D) and generating object data indicative of at least one attribute (P, W) of said reflector object, and managing said object data to track said reflector object, characterized by the step of managing said object data over a management area (M) which is wider than said detection area (D). The method according to claim 15, characterized by the steps of subdividing said detectiona area (D) into a plurality of sub-areas (Da - De), and determining that said reflector object is present in said detection area (D) when a reception level of said reflection waves in at least one of said detection sub-areas (Da - De) is higher than a predetermined threshold value. The method according to claim 16, characterized by the step of detecting said reflector object in units of said detection sub-areas (Da - De). The method according to any one of claims 15 to 17, characterized by the step of continuing management of said object data when it is determined that said reflector object has left at least in part said detection area (D), but is present in a peripheral area (Ma, Me) of said management area (M) outside said detection area (D). The method according to claim 18, characterized by the step of continuing management of said object data when it is determined that said reflector object, after leaving said detection area (D), returns into said detection area (D) within a predetermined time. The method according to claim 19, characterized by the step of stopping management of said object data when it is determined that said reflector object, after leaving said detection area (D), stays out of said detection area (D) for more than said predetermined time. The method according to any one of claims 15 to 20, characterized in that said management area (M) includes said detection area (D) and peripheral areas (Ma, Me) on both sides of said detection area (D), said peripheral areas (Ma, Me) being predetermined in terms of width. The method according to any one of claims 15 to 20, characterized in that said management area (M) includes said detection area (D) and peripheral areas (Ma, Me) on both sides of said detection area (D), a width of said peripheral areas (Ma, Me) being automatically set based on a detected width (W) of said reflector object.

Inventors: KUDOH HIROSHI, KUDOH, HIROSHI
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1999
Main classification: G01S13
IPC codes: G01S7, G01S13, B60R21, G01S15, G01S17, B60W30