Automatic brake control device, automatic brake control method, program, and recording medium

Abstract

Obstacles in a brake activation area can be detected by an ultrasonic sensor provided in the rear of a vehicle, and brakes can be activated automatically. However, it has been found that when the vehicle moves backward at a high speed, even if an obstacle is located in the brake activation area, the obstacle could be detected at a position shifted to the side.　In this automatic brake control device, the location of an obstacle while a vehicle is moving backward is detected by an ultrasonic sensor installed in the rear section of the vehicle and automatic brakes are activated, a brake activation area is set at planar coordinates corresponding to the detection location of the ultrasonic sensor, and the brake activation area includes a low-speed activation area set when the vehicle is moving backward at a low speed with respect to a set vehicle speed, and a high-speed activation area set when the vehicle is moving backward at a high speed with respect to the set vehicle speed.　

Description

Technical Field

[0001] The present invention relates to an automatic brake control device, an automatic brake control method, a program, and a recording medium using an ultrasonic sensor.

Background Art

[0002] An obstacle detection device that detects an obstacle using a sensor that transmits ultrasonic waves or electromagnetic waves and receives a reflected wave reflected by an obstacle is known. The obstacle detection device detects an obstacle from the reception result of the reflected wave by the sensor. When ultrasonic waves or electromagnetic waves are transmitted from the sensor, if an obstacle exists within the detection range of the sensor, the transmitted ultrasonic waves or the like hit the obstacle and are reflected. As a result, the sensor receives the reflected wave and detects the obstacle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, obstacles in the brake operating area can be detected by ultrasonic sensors or radar sensors installed at the rear of the vehicle, and the brakes can be automatically activated. However, radar sensors have a long detection range, and the brakes may be activated by distant obstacles, making them unsuitable for detecting obstacles when reversing a vehicle, such as for parking. Experiments have shown that with ultrasonic sensors, if the vehicle's reversing speed is relatively high, the position of the obstacle is detected incorrectly, making it difficult for the automatic brakes to activate and potentially causing the vehicle to get too close to the obstacle. On the other hand, if the operating area is expanded to detect the incorrect position, the brakes may be activated for obstacles that are not in a position to collide with during low-speed reversing. The present invention aims to provide good automatic brake control using ultrasonic sensors. [Means for solving the problem]

[0005] An automatic brake control device according to one embodiment of the present invention is a vehicle automatic brake control device that detects the position of an obstacle when the vehicle is reversing using an ultrasonic sensor installed at the rear of the vehicle and activates the automatic brake, wherein a brake operating area is set in planar coordinates corresponding to the detection position of the ultrasonic sensor, and the brake operating area includes a low-speed operating area set when reversing at a low speed relative to a set vehicle speed, and a high-speed operating area set when reversing at a high speed relative to a set vehicle speed. [Effects of the Invention]

[0006] The above-described automatic braking control system allows the automatic brakes to be activated even if the position of an obstacle is detected as being different during high-speed reverse driving. Furthermore, during low-speed reverse driving, the braking area can be optimized for low-speed reverse driving. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram showing the system configuration of the vehicle. [Figure 2] Example of a waveform received by an ultrasonic sensor. [Figure 3]An explanatory diagram for obstacle detection at the rear of a vehicle. [Figure 4] The braking area of ​​a vehicle. [Figure 5] The operating area of ​​the vehicle at low speeds and the operating area at high speeds. [Figure 6] Basic flow of Example 1. [Figure 7] Operation area setting process flow for Example 1. [Figure 8] Automatic brake detection processing flow for Example 1. [Figure 9] Low-speed operating area and high-speed operating area of ​​Example 2. [Figure 10] Low-speed operating area and high-speed operating area of ​​Example 3. [Modes for carrying out the invention]

[0008] Figure 1 shows the system configuration of a vehicle 1 equipped with an automatic brake control device 2 according to an embodiment of the present invention. The direction indicated by the arrow on the right is the front of the vehicle 1. The direction in which the arrow extends is the vehicle length direction, and the direction perpendicular to the arrow is the vehicle width direction. The vehicle 1 has four ultrasonic sensors installed at the rear, arranged in a left-right direction: a first ultrasonic sensor 21, a second ultrasonic sensor 22, a third ultrasonic sensor 23, and a fourth ultrasonic sensor 24. The first ultrasonic sensor 21, the second ultrasonic sensor 22, the third ultrasonic sensor 23, and the fourth ultrasonic sensor 24 are connected to an ECU 26, which is a computer, via sensor signal lines 25. The ECU 26 receives the output signals from the first to fourth ultrasonic sensors 21 to 24. The ECU 26 is also connected to a vehicle speed sensor 4 and a brake system 5 via signal lines 3.

[0009] The fourth ultrasonic sensor 24 and the third ultrasonic sensor 23 are installed symmetrically with respect to the central axis CL of the vehicle 1, as opposed to the first ultrasonic sensor 21 and the second ultrasonic sensor 22, and their functions are the same as those of the first ultrasonic sensor 21 and the second ultrasonic sensor 22. Therefore, the first ultrasonic sensor 21 and the second ultrasonic sensor 22, which are shown by the square dotted lines, will be described below.

[0010] The ECU 26 intermittently generates and transmits ultrasonic waves from the first ultrasonic sensor 21. It then detects the position of a nearby obstacle from the delay time T of the reflected waves received by the first ultrasonic sensor 21 and the second ultrasonic sensor 22 from the time of transmission. This position can be expressed in coordinates in the front, rear, left, and right directions relative to the vehicle 1.

[0011] Figure 2 shows an example of a waveform received by an ultrasonic sensor. The horizontal axis represents time, and the vertical axis represents the intensity of the received wave. Pulsed ultrasonic waves are repeatedly generated at detection intervals Δt. The detection interval Δt is set to be sufficiently longer than the delay time T from the transmission of the ultrasonic wave to the reception of the reflected wave. In Figure 2, the generated wave is captured near t0 when the ultrasonic wave is generated, and the reflected wave is captured at the delay time T. Therefore, the distance to the obstacle can be measured from the delay time T and the speed of sound in the air. Then, the position of the obstacle when the vehicle is reversing is detected by four ultrasonic sensors installed at the rear of the vehicle 1: the first ultrasonic sensor 21, the second ultrasonic sensor 22, the third ultrasonic sensor 23, and the fourth ultrasonic sensor 24, and the automatic brake is activated.

[0012] The coordinates of the obstacle lie on the curve of the arc Ar, which is centered at the receiving position of the ultrasonic sensor and has a radius equal to the measured distance. Figure 3 illustrates the detection of the obstacle's location. The distance to the obstacle's location can be obtained from the delay time T(21) detected by the first ultrasonic sensor 21 and the delay time T(22) detected by the second ultrasonic sensor 22. Figure 3 shows the arc Ar(21) with a radius equal to the distance indicated by the delay time T(21) and the arc Ar(22) with a radius equal to the distance indicated by the delay time T(22). The obstacle's coordinate P can be detected as the intersection of the arcs Ar(21) and Ar(22).

[0013] When the obstacle coordinates P obtained in this way are within a predetermined range from the perspective of vehicle 1, vehicle 1 automatically applies the brakes. Figure 4 shows the brake activation area Br, which is the range in which the brakes are automatically applied, as a dotted line. When vehicle 1 is reversing, even if an obstacle is detected at obstacle coordinates P1, the automatic brake control device 2 does not apply the brakes because it is outside the brake activation area Br. As vehicle 1 continues to reverse and the position of the obstacle becomes obstacle coordinates P2, it is now within the brake activation area Br, so the automatic brake control device 2 automatically applies the brakes and stops vehicle 1. This makes it possible to avoid collisions with obstacles when vehicle 1 is reversing.

[0014] However, experiments have revealed that when the reverse speed increases, and during high-speed reverse movement, the detection position shifts outward from the brake activation area Br, causing an obstacle to be detected at the shift coordinate Ps position when the obstacle is at the obstacle coordinate P2 position in Figure 4. This phenomenon is thought to be partly due to the first ultrasonic sensor 21 and the second ultrasonic sensor 22 approaching the obstacle that is the reflection source between the time the first ultrasonic sensor 21 emits ultrasonic waves and the time the reflected waves reach the first ultrasonic sensor 21 and the second ultrasonic sensor 22. Furthermore, when there is an obstacle near the side of the brake activation area Br, the reflected wave path is less likely to decrease during reverse movement for the second ultrasonic sensor 22, which is located near the center, than for the first ultrasonic sensor 21, which is located to the side. The effect of this phenomenon becomes greater during high-speed reverse movement, and the shift of the detection position to the shift coordinate Ps begins to affect the brake operation. In addition, when receiving reflected waves while moving, it is difficult to receive the range of high sound pressure of the reflected waves, which is also considered to be a cause of this phenomenon. Furthermore, even though an obstacle is located within the brake activation area Br, where the brakes should normally be automatically applied, the automatic brakes do not activate, resulting in a delay in braking. [Examples]

[0015] In the first embodiment, the reverse speed obtained from the vehicle speed sensor 4 is detected. When the vehicle is moving backward at a low speed slower than a predetermined speed, if an obstacle position is detected in the low-speed operation area BL shown in FIG. 5, the automatic brake is activated. Also, when the vehicle is moving backward at a high speed faster than the predetermined speed, if an obstacle position is detected in the high-speed operation area BH shown in FIG. 5, the automatic brake is activated. The operation area BS where the brake is activated is set in the plane coordinates corresponding to the detection positions of the four ultrasonic sensors, i.e., the first ultrasonic sensor 21, the second ultrasonic sensor 22, the third ultrasonic sensor 23, and the fourth ultrasonic sensor 24. And the operation area BS includes the low-speed operation area BL set for low-speed backward movement with respect to the set vehicle speed Vt and the high-speed operation area BH set for high-speed backward movement with respect to the set vehicle speed Vt.

[0016] The high-speed operation area BH and the low-speed operation area BL are rectangular areas set by a lateral collision determination line defining the vehicle width direction and a longitudinal collision determination line defining the vehicle length direction. The high-speed operation area BH and the low-speed operation area BL are the areas inside the rectangle. In FIG. 5, the low-speed operation area BL is a rectangular area set by the lateral collision determination line YL and the longitudinal collision determination line XL. Also, the high-speed operation area BH is a rectangular area set by the lateral collision determination line YH and the longitudinal collision determination line XH. The high-speed operation area BH is an area including the low-speed operation area BL and is wider in the vehicle width direction of the vehicle 1. Also, in the first embodiment, the high-speed operation area BH is wider also in the rearward direction than the low-speed operation area BL. By setting the high-speed operation area BH and the low-speed operation area BL as rectangular areas, it is possible to easily determine whether the obstacle coordinates P are in the operation area BS, and the burden on the ECU 26 can be reduced.

[0017] Next, the flowchart of Embodiment 1 will be described. FIG. 6 shows the basic flow. This flow starts when the vehicle 1 reverses. At least at the start of the flow, the positions on the plane coordinates of the low-speed operation area BL and the high-speed operation area BH, and the set vehicle speed Vt are stored in the memory of the ECU 26. When the vehicle 1 reverses, in the operation area setting process of step s1, an operation area BS where the automatic brake operates is set. Then, in the automatic brake determination process of step s2, it is determined whether to operate the automatic brake. This flow is repeatedly performed as long as the vehicle 1 is reversing.

[0018] In the operation area setting process of step s1 shown in FIG. 7, the reverse speed Vb is obtained in step s11. Then, in step s12, it is determined whether the reverse speed Vb is lower than the set vehicle speed Vt. If the reverse speed Vb is lower than the set vehicle speed Vt, in step s13, the low-speed operation area BL shown in FIG. 5 is set as the operation area BS. On the other hand, if the reverse speed Vb is not lower than the set vehicle speed Vt, in step s14, the high-speed operation area BH is set as the operation area BS.

[0019] In the automatic brake determination process of step s2 shown in FIG. 8, in step s21, the obstacle coordinates P are detected by the first ultrasonic sensor 21 to the fourth ultrasonic sensor 24. The right rear of the vehicle 1 and the left rear are detected by the first ultrasonic sensor 21 and the second ultrasonic sensor 22, and the third ultrasonic sensor 23 and the fourth ultrasonic sensor 24 to detect the delay time T of the reflected wave, and the obstacle coordinates P are calculated. Then, in step s22, it is determined whether the obstacle coordinates P are within the operation area BS. If the obstacle coordinates P are within the operation area BS, the automatic brake is operated in step s23. If the obstacle coordinates P are not within the operation area BS, the automatic brake is not operated.

[0020] As a result of the above flow, as shown in Figure 5, the lateral collision detection line YH that defines the vehicle width direction of the high-speed operating area BH extends outside the shift coordinate Ps in the vehicle width direction. Therefore, as shown in Figure 4, even if the original obstacle coordinate P is detected at the position of the shift coordinate Ps during high-speed reverse driving, the automatic brake can be activated. Furthermore, during low-speed reverse driving, the low-speed operating area BL, where the lateral collision detection line YL that defines the vehicle width direction is in a narrow position in the vehicle width direction, is set as the operating area BS. Therefore, the automatic brake is less likely to activate when reversing slowly in a narrow space. [Examples]

[0021] Figure 9 shows the low-speed operating area BL and high-speed operating area BH in Example 2. In Example 2, the low-speed operating area BL is the same as in Example 1, but the high-speed operating area BH is different. In Example 2, the high-speed operating area BH does not extend to the rear and has a wider shape in the vehicle width direction compared to the low-speed operating area BL. In Example 2 as well, when reversing at high speed, the automatic brake will activate even if an obstacle at obstacle coordinate P is detected at the position of shift coordinate Ps, as shown in Figure 9. Furthermore, when reversing at low speed, the decision to activate the automatic brake is made based on the low-speed operating area BL, which is narrow in the vehicle width direction, so the automatic brake will not activate and the vehicle 1 will not stop when reversing at low speed in a narrow space. [Examples]

[0022] In Example 3, the operating area expands in multiple stages from low-speed reverse to high-speed reverse. Figure 10 shows the low-speed operating area BL and high-speed operating areas BH1 to BH3 of Example 3. In Example 2, the low-speed operating area BL is the same as in Examples 1 and 2. When the reverse speed Vb becomes the set vehicle speed Vt, the high-speed operating area BH1 is set to operating area BS. As the reverse speed Vb increases further, the operating area BS expands in multiple stages in the vehicle width direction, expanding to the high-speed operating area BH3 via the high-speed operating area BH2. By appropriately designing the expansion width in the vehicle width direction in relation to the reverse speed Vb, it is possible to balance the detection of shift coordinates Ps that are detected with a positional shift with the elimination of unnecessary automatic braking during low-speed reverse.

[0023] In the flow of Example 3, in the operating area setting process of step s1 in Figure 7, multiple judgment processes are performed for multiple set vehicle speeds. Then, one of the following is set for the operating area BS: low-speed operating area BL, high-speed operating area BH1, high-speed operating area BH2, or high-speed operating area BH3. In Example 3, there are three stages for the high-speed operating area, but there may be two stages or four or more stages.

[0024] Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and any design changes, etc., that do not depart from the spirit of the present invention are also included. Furthermore, the above-described embodiments can be combined by utilizing each other's technologies, as long as there are no particular contradictions or problems in their purpose and configuration.

[0025] The flowchart of the embodiment illustrates an automatic brake control method for a vehicle. The flowchart is a program that enables a computer to implement the functions of detecting the position of an obstacle when the vehicle is reversing using an ultrasonic sensor installed at the rear of the vehicle 1, and setting a brake operating area in planar coordinates corresponding to the position detected by the ultrasonic sensor. This program may be recorded on a computer-readable recording medium as an obstacle detection program. [Explanation of Symbols]

[0026] 1 vehicle 2. Automatic braking control system 21. First ultrasonic sensor 22 Second ultrasonic sensor 23 Third ultrasonic sensor 24. Fourth ultrasonic sensor 25 Sensor signal line 26 ECU 3 signal lines 4. Vehicle speed sensor 5 Brake System Ar arc Br brake operating area BS operating area BL Low-speed operating area BH High-Speed ​​Operating Area BH1 High-speed operating area BH2 High-speed operating area BH3 High-speed operating area CL center axis P Obstacle coordinates P1 Obstacle coordinates P2 Obstacle Coordinates Ps Shift Coordinates T delay time Vb reverse speed Vt setting vehicle speed Δt Detection period

Claims

1. An automatic brake control device for a vehicle that detects the position of an obstacle when the vehicle is reversing using an ultrasonic sensor installed at the rear of the vehicle and activates the automatic brake, The ultrasonic sensor comprises a first ultrasonic sensor and a second ultrasonic sensor located closer to the center of the vehicle than the first ultrasonic sensor. The reflected ultrasonic waves transmitted from the first ultrasonic sensor are received by the first ultrasonic sensor and the second ultrasonic sensor, and the position of the obstacle is detected from the delay time from transmission. A brake operating area is set in the planar coordinate system corresponding to the detection position of the ultrasonic sensor. The brake operating area is defined as a rectangular region by a lateral collision detection line defining the vehicle width direction and a longitudinal collision detection line defining the vehicle length direction, and includes a low-speed operating area set when reversing at a low speed relative to the set vehicle speed, and a high-speed operating area set when reversing at a high speed relative to the set vehicle speed. An automatic brake control device characterized in that the high-speed operating area is wider in the vehicle width direction than the low-speed operating area, corresponding to the fact that the coordinates of the obstacle detected in the high-speed operating area are shifted outward in the vehicle width direction compared to the coordinates of the obstacle detected in the low-speed operating area.

2. After the vehicle's reverse speed reaches the set speed, the spacing between the lateral collision detection lines widens in multiple stages as the reverse speed increases, while the longitudinal collision detection line remains unchanged. The automatic brake control device according to claim 1.

3. An automatic brake control method for a vehicle that uses an ultrasonic sensor installed at the rear of the vehicle to detect the position of an obstacle when the vehicle is reversing and activates the automatic brake, The ultrasonic sensor comprises a first ultrasonic sensor and a second ultrasonic sensor located closer to the center of the vehicle than the first ultrasonic sensor. The reflected ultrasonic waves transmitted from the first ultrasonic sensor are received by the first ultrasonic sensor and the second ultrasonic sensor, and the position of the obstacle is detected from the delay time from transmission. A brake operating area is set in the planar coordinate system corresponding to the detection position of the ultrasonic sensor. The brake operating area is defined as a rectangular region by a lateral collision detection line defining the vehicle width direction and a longitudinal collision detection line defining the vehicle length direction, and includes a low-speed operating area set when reversing at a low speed relative to the set vehicle speed, and a high-speed operating area set when reversing at a high speed relative to the set vehicle speed. A vehicle automatic brake control method characterized in that the high-speed operating area is wider in the vehicle width direction than the low-speed operating area, corresponding to the fact that the coordinates of the obstacle detected in the high-speed operating area are shifted outward in the vehicle width direction compared to the coordinates of the obstacle detected in the low-speed operating area.

4. On the computer, The system includes a function that detects the position of obstacles when the vehicle is reversing using an ultrasonic sensor installed at the rear of the vehicle, A program for implementing a function to set a brake operating area in planar coordinates corresponding to the detection position of the ultrasonic sensor, The ultrasonic sensor comprises a first ultrasonic sensor and a second ultrasonic sensor located closer to the center of the vehicle than the first ultrasonic sensor. The reflected ultrasonic waves transmitted from the first ultrasonic sensor are received by the first ultrasonic sensor and the second ultrasonic sensor, and the position of the obstacle is detected from the delay time from transmission. The brake operating area is defined as a rectangular region by a lateral collision detection line defining the vehicle width direction and a longitudinal collision detection line defining the vehicle length direction, and includes a low-speed operating area set when reversing at a low speed relative to the set vehicle speed, and a high-speed operating area set when reversing at a high speed relative to the set vehicle speed. A program characterized in that the high-speed operating area is wider in the vehicle width direction than the low-speed operating area, corresponding to the fact that the coordinates of the obstacle detected in the high-speed operating area are shifted outward in the vehicle width direction compared to the coordinates of the obstacle detected in the low-speed operating area.

5. On the computer, The system includes a function that detects the position of obstacles when the vehicle is reversing using an ultrasonic sensor installed at the rear of the vehicle, A computer-readable recording medium that stores a program for realizing a function to set a brake operating area in planar coordinates corresponding to the detection position of the ultrasonic sensor, The ultrasonic sensor comprises a first ultrasonic sensor and a second ultrasonic sensor located closer to the center of the vehicle than the first ultrasonic sensor. The reflected ultrasonic waves transmitted from the first ultrasonic sensor are received by the first ultrasonic sensor and the second ultrasonic sensor, and the position of the obstacle is detected from the delay time from transmission. The brake operating area is defined as a rectangular region by a lateral collision detection line defining the vehicle width direction and a longitudinal collision detection line defining the vehicle length direction, and includes a low-speed operating area set when reversing at a low speed relative to the set vehicle speed, and a high-speed operating area set when reversing at a high speed relative to the set vehicle speed. A computer-readable recording medium on which a program is recorded is characterized in that the high-speed operating area is wider in the vehicle width direction than the low-speed operating area, corresponding to the fact that the coordinates of the obstacle detected in the high-speed operating area are shifted outward in the vehicle width direction compared to the coordinates of the obstacle detected in the low-speed operating area.

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