Vehicle speed calculation device

Abstract

To provide a vehicle speed calculation device capable of suppressing deterioration in correction accuracy of a vehicle speed.SOLUTION: A vehicle speed calculation device comprises a target type determination unit, a vehicle speed calculation unit, a positional relation calculation unit, and a vehicle speed correction unit. When a target is an on-road object, the positional relation calculation unit calculates positional relation in a height direction between the vehicle and a fixed target based on an installation height of a radar sensor from a road surface, and when the target is an upper object, calculates positional relation in the height direction between the vehicle and the fixed target based on an up-down detection angle of the target detected by the radar sensor, or an up-down detection angle range of the radar sensor and a front-to-rear distance of the fixed target at the timing when the fixed target is lost from the up-down detection angle range. When the target is an on-road object, the vehicle speed correction unit increases the degree of correction of the vehicle speed using a relative vehicle speed compared to that when the target is the upper object.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] This disclosure relates to a vehicle speed calculation device.

Background Art

[0002] Conventionally, as a technical document related to a vehicle speed calculation device, Japanese Patent No. 6832166 is known. Japanese Patent No. 6832166 discloses a technique for correcting a detected own vehicle speed detected by a vehicle speed sensor using the relative speed of a target detected by a radar sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology as described above, the angular resolution of the radar sensor in the vertical direction of the vehicle may be relatively coarse. Therefore, for example, when the target is an upper target, the detection accuracy of the vertical detection angle of the target decreases, and as a result, the correction accuracy of the vehicle speed may decrease.

[0005] An object of this disclosure is to provide a vehicle speed calculation device capable of suppressing a decrease in the correction accuracy of the vehicle speed.

Means for Solving the Problems

[0006] This disclosure teethA vehicle speed calculation device for calculating the vehicle speed of a vehicle, comprising: an object type determination unit that determines whether a fixed object in front of the vehicle is a road object or an overhead object based on the power received by the vehicle's radar sensor; a vehicle speed calculation unit that calculates the vehicle speed based on the detection result of the vehicle's wheel speed sensor; a position relationship calculation unit that calculates the position relationship between the vehicle and the fixed object based on the detection result of the radar sensor; and a vehicle speed correction unit that corrects the vehicle speed based on the relative speed and position relationship of the fixed object with respect to the vehicle detected by the radar sensor. A data storage unit that stores information on the received power of the radar sensor, The system includes a position relationship calculation unit which, when the fixed target is a road object, calculates the positional relationship between the vehicle and the fixed target based on the installation height of the radar sensor from the road surface; when the fixed target is an overhead object, calculates the positional relationship between the vehicle and the fixed target based on the vertical detection angle of the fixed target detected by the radar sensor, or the vertical detection angle range of the radar sensor and the front-to-rear distance of the fixed target at the time the fixed target is lost from the vertical detection angle range; and the vehicle speed correction unit which, when the fixed target is a road object, increases the degree of correction of the vehicle speed using relative speed and position relationship compared to when the fixed target is an overhead object. death , The object type determination unit determines whether a fixed object is a road object or an overhead object based on the information of received power accumulated during the period until the vehicle passes the fixed object or until the received power is lost. It determines that the fixed object is an overhead object if the front-to-rear distance of the fixed object at the time the received power is lost is greater than or equal to a predetermined value, the rate of decrease in received power before loss relative to the front-to-rear distance of the fixed object is greater than or equal to a predetermined value, the rate of decrease in relative speed relative to the front-to-rear distance of the fixed object is greater than or equal to a predetermined value, and the fixed object is within the left-to-right detection range of the radar sensor or the left-to-right distance of the fixed object is less than or equal to a predetermined value. . [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a vehicle speed calculation device that can suppress a decrease in the accuracy of vehicle speed correction. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram of a vehicle speed calculation device according to one embodiment. [Figure 2] This is a plan view illustrating the positional relationship between the vehicle and the target object. [Figure 3] This is a side view illustrating the positional relationship between the vehicle and the target object. [Figure 4] This is a side view illustrating the positional relationship between the vehicle and the target object. [Figure 5]This figure shows the change in the received power of the radar sensor over time. [Figure 6] This is a flowchart showing the processing performed by the vehicle speed calculation device shown in Figure 1. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to the drawings.

[0010] Figure 1 is a block diagram of a vehicle speed calculation device according to one embodiment. As shown in Figure 1, the vehicle speed calculation device 1 includes a wheel speed sensor 2, a radar sensor 3, and an ECU [Electronic Control Unit] 10. The vehicle speed calculation device 1 calculates the vehicle speed of the vehicle 8 (see Figure 2).

[0011] The wheel speed sensor 2 is mounted on the wheel or drive shaft of the vehicle 8 (see Figure 2). The drive shaft rotates integrally with the wheel. The wheel speed sensor 2 detects the rotational speed of the vehicle 8's wheel. The wheel speed sensor 2 transmits the detection result to the ECU 10.

[0012] As shown in Figures 2 and 3, the radar sensor 3 is installed at the front end of the vehicle 8. The radar sensor 3 is located approximately in the center of the vehicle 8 in the left-right direction. The radar sensor 3 is located at a predetermined distance from the road surface 7. The installation height D4 of the radar sensor 3 from the road surface 7 is stored in advance in the memory of the ECU 10. The radar sensor 3 emits radio waves or light toward the front of the vehicle 8. The radar sensor 3 detects a fixed object 9 by receiving radio waves or light reflected by the fixed object 9 located in front of the vehicle 8. The fixed object 9 is an object whose position is fixed relative to the road. The radar sensor 3 is, for example, a millimeter-wave radar.

[0013] The radar sensor 3 detects the relative speed of the stationary object target 9 with respect to the vehicle 8. The direction of the relative speed of the stationary object target 9 is parallel to the virtual line connecting the radar sensor 3 and the stationary object target 9. The radar sensor 3 detects the relative distance of the stationary object target 9 with respect to the vehicle 8. The relative distance of the stationary object target 9 is the length of the virtual line connecting the radar sensor 3 and the stationary object target 9 in a straight line. The radar sensor 3 detects the left - right detection angle α1 of the stationary object target 9. The left - right detection angle α1 is the angle formed by the virtual line connecting the radar sensor 3 and the stationary object target 9 with respect to the X - axis when viewed from the Z - axis direction (the up - down direction of the vehicle 8). The radar sensor 3 detects the up - down detection angle α2 of the stationary object target 9. The up - down detection angle α2 is the angle formed by the virtual line connecting the radar sensor 3 and the stationary object target 9 with respect to the X - axis when viewed from the Y - axis direction (the left - right direction of the vehicle 8). The angular resolution of the radar sensor 3 in the XZ plane is coarser than the angular resolution of the radar sensor 3 in the XY plane. That is, the detection accuracy of the up - down detection angle α2 by the radar sensor 3 is lower than the detection accuracy of the left - right detection angle α1 by the radar sensor 3. The radar sensor 3 transmits the detection result to the ECU 10.

[0014] The ECU 10 is an electronic control unit having a CPU [Central Processing Unit] and a storage unit. The storage unit is, for example, a ROM [Read Only Memory] or a RAM [Random Access Memory] etc. In the ECU 10, for example, various functions are realized by the program stored in the storage unit being executed by the CPU.

[0015] Functionally, the ECU 10 includes a vehicle speed calculation unit 11, a position relationship calculation unit 12, a relative vehicle speed calculation unit 13, a vehicle speed correction unit 14, a data storage unit 15, and an object type determination unit 16.

[0016] The vehicle speed calculation unit 11 calculates the vehicle speed of the vehicle 8 based on the detection result of the wheel speed sensor 2. The vehicle speed calculation unit 11 calculates the vehicle speed of the vehicle 8 based on the diameter of the wheel stored in advance and the rotational speed of the wheel transmitted from the wheel speed sensor 2.

[0017] The position relationship calculation unit 12 calculates the position relationship (hereinafter simply referred to as "position relationship") between the vehicle 8 and the fixed target 9 based on the detection results of the radar sensor 3. The position relationship is the relative position of the vehicle 8 and the fixed target 9 in three-dimensional space. The position relationship includes the position relationship in the height direction between the vehicle 8 and the fixed target 9. Figures 2 to 4 are diagrams for explaining the position relationship between the vehicle and the target. As shown in Figures 2 to 4, the position relationship includes the front-to-back distance D1 of the fixed target 9, the left-to-right distance D2 of the fixed target 9, and the up-to-down distance D3 of the fixed target 9. The front-to-back distance D1 is the distance between the radar sensor 3 and the fixed target 9 in the X-axis direction (front-to-back direction of the vehicle 8). The front-to-back distance D1 is the distance between the vehicle 8 and the fixed target 9 in the X-axis direction. The left-to-right distance D2 is the distance between the radar sensor 3 and the fixed target 9 in the Y-axis direction. The up-to-down distance D3 of the fixed target 9 is the distance between the radar sensor 3 and the fixed target 9 in the Z-axis direction.

[0018] As shown in Figures 2 and 3, when the fixed object 9 is an overhead object, the vertical distance D3 of the fixed object 9 is often unknown. The position relationship calculation unit 12 calculates the position relationship based on the vertical detection angle α2, etc., when the fixed object 9 is an overhead object. Specifically, the position relationship calculation unit 12 calculates the position relationship based on the relative distance of the fixed object 9 (the length of the imaginary line connecting the radar sensor 3 and the fixed object 9 in a straight line), the horizontal detection angle α1, and the vertical detection angle α2. The position relationship calculation unit 12 may also calculate the position relationship when the front-to-back distance D1 is far enough to reduce the influence of the vertical distance D3 (when the front-to-back distance D1 is farther than a predetermined value) when the fixed object 9 is an overhead object. The predetermined value for the front-to-back distance D1 is a value predetermined based on the height of a typical overhead object. An overhead object is located above the vehicle 8 in the Z-axis direction. Examples of overhead objects include traffic lights, road signs, streetlights, elevated bridges, or pedestrian bridges.

[0019] As shown in FIG. 4, when the fixed object marker 9 is a road object, the vertical distance D3 of the fixed object marker 9 substantially coincides with the installation height D4 of the radar sensor 3 from the road surface 7. When the fixed object marker 9 is a road object (when the vertical distance D3 of the fixed object marker 9 is known), the positional relationship calculation unit 12 calculates the positional relationship based on the installation height D4 etc., without relying on the vertical detection angle α2. Specifically, the positional relationship calculation unit 12 calculates the positional relationship based on the relative distance of the fixed object marker 9 (the length of the virtual line connecting the radar sensor 3 and the fixed object marker 9 in a straight line), the left and right detection angles α1, and the installation height D4. When the fixed object marker 9 is a road object, the positional relationship calculation unit 12 may calculate the positional relationship when the front-rear distance D1 is close enough (when the front-rear distance D1 is closer than a predetermined value) that the influence of the road surface gradient need not be considered. The predetermined value regarding the front-rear distance D1 is a value predetermined based on a general road surface gradient etc. The road object is provided on the road surface 7. The road object is, for example, a road iron plate, a manhole cover, a bridge joint, or a railway track etc. The road iron plate is, for example, a construction iron plate laid on the road surface 7 etc.

[0020] The relative vehicle speed calculation unit 13 calculates the relative vehicle speed of the vehicle 8 based on the relative speed of the fixed object marker 9 detected by the radar sensor 3 and the positional relationship. The direction of the relative vehicle speed is parallel to the X-axis direction (the traveling direction of the vehicle 8). Thus, the relative vehicle speed of the vehicle 8 is the traveling speed of the vehicle 8 calculated based on the relative speed of the fixed object marker 9 with respect to the vehicle 8 and the positional relationship.

[0021] The vehicle speed correction unit 14 corrects the vehicle speed calculated by the vehicle speed calculation unit 11 based on the relative speed of the fixed object marker 9 with respect to the vehicle 8 detected by the radar sensor 3 and the positional relationship. Specifically, the vehicle speed correction unit 14 uses the relative vehicle speed calculated by the relative vehicle speed calculation unit 13 to correct the vehicle speed calculated by the vehicle speed calculation unit 11. The vehicle speed correction unit 14 adjusts the proportion occupied by each of the vehicle speed calculated by the vehicle speed calculation unit 11 and the relative vehicle speed calculated by the relative vehicle speed calculation unit 13 in the vehicle speed.

[0022] Specifically, the vehicle speed correction unit 14 calculates the corrected vehicle speed based on, for example, the formula V = f1 × V1 + f2 × V2. V1 is the vehicle speed calculated by the vehicle speed calculation unit 11 (vehicle speed before correction), f1 is the first correction coefficient, V2 is the relative vehicle speed calculated by the relative vehicle speed calculation unit 13, f2 is the second correction coefficient, and V is the corrected vehicle speed. In other words, the vehicle speed correction unit 14 calculates the corrected vehicle speed V by adding up the product of the vehicle speed V1 calculated by the vehicle speed calculation unit 11 and the first correction coefficient f1, and the product of the relative vehicle speed V2 calculated by the relative vehicle speed calculation unit 13 and the second correction coefficient f2. The sum of the first correction coefficient f1 and the second correction coefficient f2 is, for example, 1.

[0023] The vehicle speed correction unit 14 increases the degree of correction of the vehicle speed V1 using the relative vehicle speed V2 when the fixed object 9 is a road object compared to when the fixed object 9 is an overhead object. Specifically, the vehicle speed correction unit 14 increases the second correction coefficient f2 when the fixed object 9 is a road object compared to when the fixed object 9 is an overhead object. For example, when the fixed object 9 is an overhead object, the vehicle speed correction unit 14 uses 0.9 as the first correction coefficient f1 and 0.1 as the second correction coefficient f2, while when the fixed object 9 is a road object, it uses 0.1 as the first correction coefficient f1 and 0.9 as the second correction coefficient f2. In this way, the vehicle speed correction unit 14 increases the degree of influence of the relative vehicle speed V2 on the vehicle speed V when the fixed object 9 is a road object compared to when the fixed object 9 is an overhead object.

[0024] The data storage unit 15 stores various types of information. The data storage unit 15 buffers various types of data. The data storage unit 15 stores over time the relative speed of the fixed target 9 detected by the radar sensor 3, the relative distance (or front-to-back distance D1) of the fixed target 9, the left-to-right detection angle α1, and the up-to-down detection angle α2. The data storage unit 15 stores over time the vehicle speed calculated by the vehicle speed calculation unit 11 and the positional relationship calculated by the positional relationship calculation unit 12. The data storage unit 15 stores over time the relative vehicle speed calculated by the relative vehicle speed calculation unit 13.

[0025] The data storage unit 15 does not have to store the relative vehicle speed calculated by the relative vehicle speed calculation unit 13 for each calculation cycle. The data storage unit 15 may store the relative vehicle speed only when the front-to-rear distance D1 is close enough that the effect of the road surface gradient does not need to be considered (when the front-to-rear distance D1 is closer than a predetermined value) if the fixed object 9 is an object on the road. The data storage unit 15 may store the relative vehicle speed only when the front-to-rear distance D1 is far enough that the effect of the vertical distance D3 can be reduced (when the front-to-rear distance D1 is farther than a predetermined value) if the fixed object 9 is an object above.

[0026] The data storage unit 15 stores information on the received power of the radar sensor 3 over time. Figure 5 shows the change in the received power of the radar sensor 3 over time when the fixed target 9 is an overhead object. As shown in Figure 5, the received power P corresponding to the fixed target 9 gradually increases and then gradually decreases as the longitudinal distance D1 decreases. The received power P begins to decrease when the longitudinal distance D1 is the decrease start distance T1 and disappears when the longitudinal distance D1 is the disappearance distance T2. The data storage unit 15 continues to store information on the received power P for the fixed target 9 until the received power P disappears or until the vehicle 8 passes the fixed target 9 (the longitudinal distance D1 becomes zero). The decrease start distance T1 and the disappearance distance T2 are correlated with the height of the fixed target 9. The decrease start distance T1 and the disappearance distance T2 each increase as the height of the fixed target 9 increases. In other words, the received power P begins to decrease earlier and disappears earlier as the height of the fixed target 9 increases.

[0027] The target type determination unit 16 determines whether the fixed target 9 is a road object or an overhead object based on the received power P of the radar sensor 3. The target type determination unit 16 determines whether the fixed target 9 is a road object or an overhead object based on the information of the received power P accumulated during the period until the received power P for the fixed target 9 is lost, or during the period until the vehicle 8 passes the fixed target 9. The target type determination unit 16 determines whether the fixed target 9 is a road object or not based on, for example, the method described in Japanese Patent Application Publication No. 2013-156147.

[0028] The target type determination unit 16 determines that the fixed target 9 is an overhead object if the front-to-rear distance D1 (disappearance distance T2) of the fixed target 9 at the time the received power P disappears is greater than or equal to a predetermined value, the rate of decrease of the received power P before disappearance with respect to the front-to-rear distance D1 of the fixed target 9 is greater than or equal to a predetermined value, the rate of decrease of the relative speed of the fixed target 9 with respect to the front-to-rear distance D1 of the fixed target 9 is greater than or equal to a predetermined value, and the fixed target 9 is within the left-to-right detection range of the radar sensor 3 or the left-to-right distance D2 of the fixed target 9 is less than or equal to a predetermined value. The rate of decrease of the received power P before disappearance is, for example, the division value (ΔP / (T1-T2)) obtained by dividing the amount of change in received power P by the difference between the decrease start distance T1 and the disappearance distance T2. The relative speed of the fixed target 9 is the product of the cosine of the detection angle of the fixed target 9 (the angle made with respect to the X axis by the imaginary line connecting the radar sensor 3 and the fixed target 9) and the relative vehicle speed, and tends to decrease sharply just before the received power P disappears. The predetermined values ​​for the disappearance distance T2, the predetermined value for the rate of decrease of the received power P before disappearance, the predetermined value for the rate of decrease of the relative speed of the fixed target 9, and the predetermined value for the left-right distance D2 of the fixed target 9 are all predetermined values ​​based on the height of typical overhead objects, etc.

[0029] Next, the processing of the ECU 10 in the vehicle speed calculation device 1 of this embodiment will be described. Figure 6 is a flowchart showing the processing by the ECU 10. As shown in Figure 6, in step S1, the ECU 10 determines whether or not the fixed target 9 is a stationary object. For example, the ECU 10 determines that the fixed target 9 is a stationary object if the difference between the vehicle speed calculated by the vehicle speed calculation unit 11 and the relative vehicle speed calculated by the relative vehicle speed calculation unit 13 is less than or equal to a predetermined value. For example, the ECU 10 determines that the fixed target 9 is not a stationary object (the fixed target 9 is a moving object) if the difference between the vehicle speed calculated by the vehicle speed calculation unit 11 and the relative vehicle speed calculated by the relative vehicle speed calculation unit 13 is greater than a predetermined value. This predetermined value is, for example, about 20% of the vehicle speed calculated by the vehicle speed calculation unit 11.

[0030] If the fixed target 9 is a stationary object (step S1: YES), the ECU 10 stores the detection result of the radar sensor 3 in step S2. If the fixed target 9 is not a stationary object (step S1: NO), the ECU 10 terminates the current process. In step S3, the ECU 10 determines whether the fixed target 9 is a road object or not. If the fixed target 9 is a road object (step S3: YES), the ECU 10 increases the degree of correction of the vehicle speed using relative vehicle speed in step S4. If the fixed target 9 is not a road object (step S3: NO), the ECU 10 determines whether the fixed target 9 is an overhead object or not in step S5. If the fixed target 9 is an overhead object (step S5: YES), the ECU 10 decreases the degree of correction of the vehicle speed using relative vehicle speed in step S6.

[0031] As explained above, the angular resolution of the radar sensor 3 in the Z-axis direction may be relatively coarse. Therefore, if the fixed target 9 is an object above, the detection accuracy of the vertical detection angle α2 of the fixed target 9 may decrease, potentially reducing the accuracy of the positional relationship calculation. If the fixed target 9 is a road object, the vertical distance D3 of the fixed target 9 approximates the installation height D4 of the radar sensor 3 from the road surface 7. When the fixed target 9 is a road object, the positional relationship calculation unit 12 calculates a positional relationship with relatively high reliability based on the installation height D4 of the radar sensor 3 from the road surface 7, instead of the vertical detection angle α2 of the fixed target 9. When the fixed target 9 is an object above, the positional relationship calculation unit 12 calculates a positional relationship with relatively low reliability based on the vertical detection angle α2 of the fixed target 9 detected by the radar sensor 3. When the fixed target 9 is a road object, the vehicle speed correction unit 14 increases the degree of correction of the vehicle speed using relative vehicle speed compared to when the fixed target 9 is an object above. As a result, even if the accuracy of calculating the positional relationship when the fixed target 9 is an object above it decreases due to a decrease in the detection accuracy of the vertical detection angle α2 of the fixed target 9, the decrease in the accuracy of vehicle speed correction is suppressed. Therefore, the decrease in the accuracy of vehicle speed correction is suppressed by the vehicle speed calculation device 1.

[0032] The vehicle speed calculation device 1 includes a data storage unit 15 that stores information on the received power of the radar sensor 3. The target type determination unit 16 determines whether the fixed target 9 is a road surface object or an overhead object based on the information on the received power P stored during the period until the vehicle 8 passes the fixed target 9, or until the received power P disappears. This allows the type of fixed target 9 to be determined with a simple configuration. In other words, since the target type determination unit 16 determines the type of fixed target 9 after the vehicle 8 has passed the fixed target 9 or after the received power P has disappeared, it is possible to determine the type of fixed target 9 without using advanced determination methods used in PCS [Pre-Crash Safety], for example, where real-time determination is required.

[0033] The target type determination unit 16 determines that the fixed target 9 is an overhead object if the longitudinal distance D1 of the fixed target 9 at the time the received power P is lost is greater than or equal to a predetermined value, the rate of decrease of the received power P before loss relative to the longitudinal distance D1 of the fixed target 9 is greater than or equal to a predetermined value, the rate of decrease of the relative speed of the fixed target 9 relative to the longitudinal distance D1 of the fixed target 9 is greater than or equal to a predetermined value, and the fixed target 9 is within the left-right detection range of the radar sensor 3 or the left-right distance D2 of the fixed target 9 is less than or equal to a predetermined value. This makes it possible to determine whether or not the fixed target 9 is an overhead object with a simple configuration. In other words, since the target type determination unit 16 determines the type of fixed target 9 after the vehicle 8 has passed the fixed target 9 or after the received power P has been lost, it is possible to determine whether or not the fixed target 9 is an overhead object without using advanced determination methods used in PCS [Pre-Crash Safety] etc., which require real-time determination.

[0034] The radar sensor 3 is a millimeter-wave radar. When the radar sensor 3 is a millimeter-wave radar, the angular resolution of the radar sensor 3 in the Z-axis direction tends to be coarse. Therefore, the above-mentioned effect is particularly pronounced when the radar sensor 3 is a millimeter-wave radar.

[0035] While embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above. This disclosure can be implemented in various forms, including the embodiments described above, with various modifications and improvements based on the knowledge of those skilled in the art.

[0036] The position relationship calculation unit 12 may calculate the positional relationship between the vehicle 8 and the fixed object 9 in the height direction based on the vertical detection angle range of the radar sensor 3 and the front-to-rear distance D1 of the fixed object 9 at the time when the fixed object 9 is lost from the vertical detection angle range, if the fixed object 9 is an object above. Specifically, the position relationship calculation unit 12 calculates the front-to-rear distance D1 of the fixed object 9 based on the relative distance of the fixed object 9 (length of a virtual line connecting the radar sensor 3 and the fixed object 9 in a straight line) and the left-to-right detection angle α1 at the time when the fixed object 9 is lost from the vertical detection angle range. The position relationship calculation unit 12 calculates the vertical distance D3 of the fixed object 9 based on the front-to-rear distance D1 of the fixed object 9 at the time when the fixed object 9 is lost from the vertical detection angle range and the maximum vertical detection angle of the radar sensor 3 (half of the vertical detection angle range). Note that the time when the fixed object is lost from the vertical detection angle range means the time when the fixed object moves out of the vertical detection angle range. In other words, the timing at which a fixed target is lost from the vertical detection angle range means the timing at which the fixed target is no longer present within the vertical detection angle range.

[0037] The vehicle speed correction unit 14 may use 1.0 as the first correction coefficient f1 and 0.0 as the second correction coefficient f2 when the fixed target 9 is an object above. In other words, when the fixed target 9 is an object above, the vehicle speed correction unit 14 may set the degree of influence of the relative vehicle speed V2 on the vehicle speed V to zero.

[0038] The position relationship calculation unit 12 may calculate the position relationship based on the vertical detection angle α2 at the timing when the front-to-back distance D1 is greater than or equal to a predetermined value, if the fixed object target 9 is an object above. The larger the front-to-back distance D1, the smaller the vertical detection angle α2 tends to be, and the influence of the vertical detection angle α2 on the calculation of the position relationship tends to be smaller. Therefore, by using the vertical detection angle α2 at the timing when the front-to-back distance D1 is greater than or equal to a predetermined value, the accuracy of the position relationship calculation can be improved. The predetermined value for the front-to-back distance D1 is a value predetermined based on the height of a typical object above.

[0039] The position relationship calculation unit 12 may calculate a relationship including the front-to-back distance D1 of the fixed target 9 based on the relative distance and left-to-right detection angle α1 of the fixed target 9, assuming that the vertical detection angle α2 is sufficiently small.

[0040] When the fixed object marker 9 is a road object, the reliability of the relative vehicle speed calculated by the relative vehicle speed calculation unit 13 is relatively high, so for example, the second correction coefficient f2 may be larger than the first correction coefficient f1.

[0041] In the case where the fixed object target 9 is neither an overhead object nor a road object (step S5: NO), the second correction coefficient f2 may be, for example, greater than or equal to the second correction coefficient f2 when the fixed object target 9 is an overhead object, and less than or equal to the second correction coefficient f2 when the fixed object target 9 is a road object.

[0042] The vehicle speed correction unit 14 does not need to correct the vehicle speed calculated by the vehicle speed calculation unit 11 using the relative vehicle speed calculated by the relative vehicle speed calculation unit 13. The vehicle speed correction unit 14 may correct the vehicle speed calculated by the vehicle speed calculation unit 11 based on the relative speed and positional relationship of the fixed target 9 detected by the radar sensor 3. In other words, the ECU 10 does not need to be equipped with a relative vehicle speed calculation unit 13.

[0043] In step S2, the ECU 10 may terminate the process without proceeding to step S3 if the vehicle 8 changes course, if foreign matter is attached to the radar sensor 3, if the received power P is unstable (for example, if the vehicle 8 is traveling through a tunnel or other area with a relatively large amount of reflections that act as disturbances), if the left-right distance D2 between the radar sensor 3 and the fixed object 9 is, for example, about 2m or more, if the change in the relative speed of the fixed object 9 is, for example, 2% or more, if the road surface 7 is not flat (for example, if there are steps or steep slopes), or if an inertial force of a predetermined value or more is generated in the vehicle 8. In step S4 or step S5, the vehicle speed may be corrected only if the left-right distance D2 is less than or equal to a predetermined value (for example, about 0.9m). The vehicle 8 may be an autonomous vehicle. [Explanation of Symbols]

[0044] 1...Vehicle speed calculation device, 3...Radar sensor, 8...Vehicle, 9...Fixed target, 11...Vehicle speed calculation unit, 12...Position relationship calculation unit, 13...Relative vehicle speed calculation unit, 14...Vehicle speed correction unit, 15...Data storage unit, 16...Target type determination unit.

Claims

1. A vehicle speed calculation device for calculating the vehicle speed of a vehicle, A target type determination unit that determines whether a fixed target in front of the vehicle is a road object or an overhead object based on the power received by the vehicle's radar sensor, A vehicle speed calculation unit calculates the vehicle speed of the vehicle based on the detection results of the vehicle's wheel speed sensor, A position relationship calculation unit calculates the positional relationship between the vehicle and the fixed target based on the detection results of the radar sensor, A vehicle speed correction unit corrects the vehicle speed based on the relative speed of the fixed target to the vehicle detected by the radar sensor and the positional relationship. The system includes a data storage unit that stores information on the received power of the radar sensor, The positional relationship calculation unit calculates the positional relationship in the height direction between the vehicle and the fixed object based on the installation height of the radar sensor from the road surface if the fixed object is a road object, and calculates the positional relationship in the height direction between the vehicle and the fixed object based on the vertical detection angle of the fixed object detected by the radar sensor, or the vertical detection angle range of the radar sensor and the front-to-rear distance of the fixed object at the time when the fixed object is lost from the vertical detection angle range. The vehicle speed correction unit, when the fixed target is a road object, increases the degree of correction of the vehicle speed using the relative speed and positional relationship compared to when the fixed target is an overhead object. The object type determination unit determines whether the fixed object is a road object or an overhead object based on the information of the received power accumulated during the period until the vehicle passes the fixed object, or during the period until the received power is lost. A vehicle speed calculation device that determines that a fixed object is an overhead object when the front-to-rear distance of the fixed object at the time the received power is lost is greater than or equal to a predetermined value, the rate of decrease of the received power before it is lost with respect to the front-to-rear distance of the fixed object is greater than or equal to a predetermined value, the rate of decrease of the relative speed with respect to the front-to-rear distance of the fixed object is greater than or equal to a predetermined value, and the fixed object is within the left-to-right detection range of the radar sensor or the left-to-right distance of the fixed object is less than or equal to a predetermined value.

2. The vehicle speed calculation device according to claim 1, wherein the radar sensor is a millimeter-wave radar.

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