Vehicle speed detection system and vehicle

Abstract

To provide a vehicle speed detection system capable of improving estimation accuracy of a vehicle body speed during braking.SOLUTION: A vehicle speed detection system for estimating a vehicle body speed of a vehicle includes a first acquisition unit configured to acquire a wheel speed of each of a plurality of wheels provided in the vehicle, a second acquisition unit configured to acquire speed information measurable by a distance measuring sensor provided in the vehicle, and an estimation unit configured to estimate the vehicle body speed based on a maximum wheel speed among the wheel speeds of the plurality of wheels and the speed information.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle speed detection system and a vehicle. [Background technology]

[0002] LiDAR installed on a vehicle measures the distance to an object. It is also possible to measure the vehicle's speed, which is sometimes called "vehicle speed."

[0003] The number of revolutions of the wheel is measured by, for example, a pulse generator PG, etc. The wheel speed can be measured from the number of revolutions of the wheel and the diameter of the wheel.

[0004] In addition, vehicles are equipped with an antilock brake system (ABS) that automatically releases and activates the brakes repeatedly even if the brake pedal is pressed when the wheels lock during emergency braking, restoring the grip of the wheels and maintaining the vehicle's driving stability. The ABS detects slippage by calculating the deceleration from the wheel speed and the speed difference with other wheels, and reduces the braking force on the wheel where slippage is detected, and adjusts the braking force to restore braking force on the wheel where slippage has subsided.

[0005] For example, Patent Document 1 discloses a vehicle control device having wheel speed detection means for detecting the wheel speed of each wheel, estimating the vehicle speed by averaging the detected wheel speeds, calculating a slip ratio based on the wheel speed and the vehicle speed, and anti-lock control means for preventing the wheels from locking by reducing the braking force applied to the wheels when the calculated slip ratio exceeds a predetermined target slip ratio.

[0006] In the following explanation, "slip ratio" refers to the percentage obtained by dividing the difference between the vehicle speed and the wheel speed by the vehicle speed. For example, the slip ratio is 0% when the brakes are not applied, and 100% when the wheels are completely locked. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-201081 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the vehicle control device described in Patent Document 1, if all wheels slip during braking, the accuracy of estimating vehicle speed decreases, which reduces the accuracy of slip ratio, resulting in a problem of reduced brake control performance.

[0009] An object of the present disclosure is to provide a vehicle speed detection system that can improve the accuracy of estimating vehicle speed during braking. [Means for solving the problem]

[0010] In order to achieve the above object, the vehicle speed detection system in the present disclosure includes: A vehicle speed detection system that estimates a vehicle speed, a first acquisition unit that acquires a wheel speed of each of a plurality of wheels provided on the vehicle; a second acquisition unit that acquires speed information measurable by a distance measurement sensor provided on the vehicle; an estimation unit that estimates the vehicle body speed based on a maximum wheel speed among the wheel speeds of the plurality of wheels and the speed information; Equipped with.

[0011] The vehicle in this disclosure is The above vehicle speed detection system, a correction unit that corrects GPS-related vehicle position information based on the vehicle speed estimated by the estimation unit; Equipped with. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to improve the accuracy of estimating the vehicle speed during braking. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram functionally illustrating sensors, control devices, and the like mounted on a vehicle according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a graph showing the change in speed information and wheel speed over time. [Figure 3] FIG. 3 is a block diagram functionally illustrating the vehicle speed detection system according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a block diagram showing the functions of the estimation unit in this embodiment. [Figure 5A] FIG. 5A is a graph showing the conversion of the speed information, wheel speed, and maximum wheel speed over time. [Figure 5B] FIG. 5B is a graph showing the change over time in the vehicle speed estimated by the estimation unit in this embodiment, compared with the maximum wheel speed and the like. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. 1 is a block diagram functionally illustrating sensors, control devices, and the like mounted on a vehicle according to an embodiment of the present disclosure. Vehicle 1 (see FIG. 3) is equipped with a control device 30 (Electronic Control Unit: ECU), a pulse generator PG for measuring the rotation speed of the wheels, an Electronic Control Brake System 11 (EBS), and a LiDAR (Light Detection And Ranging: LiDAR) 12 for measuring the distance from vehicle 1 to an object. Note that LiDAR 12 corresponds to the "distance measuring sensor" of the present disclosure.

[0015] The electronically controlled brake system 11 (EBS) receives wheel rotation speeds from multiple pulse generators PG. The electronically controlled brake system 11 has an antilock brake system (ABS) function, and uses the wheel speeds derived from the wheel rotation speeds as parameters for ABS brake control.

[0016] The wheel speed is input to the control device 30 from the electronically controlled brake system 11. The control device 30 also receives a measurement value measured by the rider 12. The measurement value measured by the rider 12 is a value corresponding to the speed, such as a distance.

[0017] Figure 2 is a graph showing the changes in speed information and wheel speed over time. The horizontal axis of Figure 2 shows time (s) and the vertical axis shows speed (km / h). In Figure 2, the speed information is shown with a dashed line, one of the two wheel speeds is shown with a thick solid line, and the other wheel speed is shown with a thin solid line. In Figure 2, for comparison with the speed information and wheel speed, the vehicle speed (travel speed) is shown with a thick dashed line, and the maximum wheel speed is shown with a medium-thick solid line.

[0018] Area A, enclosed by a dashed line in Figure 2, is an area where the difference in wheel speeds is large, indicating wheel slippage. When all wheels are slipping, the speed information contains a large amount of noise, which can reduce the accuracy of the wheel speeds and the vehicle speed detected based on the speed information. This reduces the accuracy of the slip ratio, which in turn reduces brake control performance and increases the braking distance.

[0019] The vehicle speed detection system according to the embodiment of the present disclosure is a system that can improve the accuracy of estimating the vehicle speed even when, for example, all of the wheels are slipping during braking of the vehicle 1.

[0020] (Control device 30) FIG. 3 is a block diagram functionally illustrating a vehicle speed detection system according to an embodiment of the present disclosure. The vehicle speed detection system 100 according to this embodiment includes a control device 30 (ECU). The control device 30 includes a control unit 31 and a storage unit 35. In FIG. 3, arrows indicate main data flows, and data flows not shown in FIG. 3 may also exist. In FIG. 3, each functional block indicates a functional unit configuration, rather than a hardware (device) unit configuration. Therefore, the functional blocks shown in FIG. 3 may be implemented in a single device, or may be implemented separately in multiple devices. Data may be exchanged between functional blocks via any means, such as a data bus or a controller area network (CAN bus).

[0021] The storage unit 35 is a ROM (Read Only Memory) that stores a computer program that realizes the control device 30, and a RAM (Random Access Memory) that serves as a work area for the control device 30. The storage unit 35 also includes interfaces such as an AD converter, a DA converter, an I / O port, and a CAN. The ROM may be a flash memory that stores an OS (Operating System), application programs, and various information referenced when the application programs are executed, or may be a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive).

[0022] The control unit 31 is a processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit) of the control device 30, and functions as a first acquisition unit 32, a second acquisition unit 33, and an estimation unit 34 by executing programs stored in the memory unit 35.

[0023] 3 shows an example in which the control device 30 is configured as a single device. However, the control device 30 may be realized by, for example, multiple processors, memories, and other computational resources. In this case, each unit constituting the control unit 31 is realized by at least one of multiple different processors executing a program.

[0024] The first acquisition unit 32 acquires multiple (four in this case) wheel speeds (v1, v2, v3, and v4 shown in FIG. 4) from the electronically controlled brake system 11 (EBS) at regular time intervals. The wheel speeds can be prepared according to the number of wheels of the vehicle.

[0025] The second acquisition unit 33 acquires a measurement value (a value corresponding to a speed, for example, a distance) from the lidar 12 at regular time intervals.

[0026] The estimation unit 34 repeats the process of estimating the vehicle speed v hat (^) using the wheel speeds and measurement values ​​acquired at regular time intervals. The process of estimating the vehicle speed v hat (^) repeated in this manner will be described later.

[0027] 4 is a block diagram showing the estimating unit 34 according to this embodiment. The estimating unit 34 includes a maximum value calculator 341, a differentiator 342, and a Kalman filter 343.

[0028] The wheel speeds v1, v2, v3, and v4 are input to the maximum value calculator 341. The maximum value calculator 341 calculates a maximum wheel speed V+n1, which is the maximum value among the wheel speeds v1, v2, v3, and v4.

[0029] The differentiator 342 differentiates the measurement values ​​of the LIDAR 12 and converts them into velocity information. The differentiator 342 also functions as a low-pass filter that removes high-frequency components, which are noise, from the measurement values. In other words, the measurement values ​​of the LIDAR 12 are converted into smoothed velocity information by the differentiator 342.

[0030] Specifically, when the function of extracting high frequency components from a measurement value is expressed in the frequency domain s, it becomes the following equation (1).

number

[0031] The speed V+n2, which is smoothed speed information, is output from the differentiator 342. The speed (n1-n2), which is the subtraction value obtained by subtracting the speed V+n2 from the maximum wheel speed V+n1, is input to the Kalman filter 343.

[0032] The Kalman filter 343 estimates the speed n1 hat (^) based on the speed (n1-n2).

[0033] The vehicle speed v hat (^) is output, which is the subtraction value obtained by subtracting the speed n1 hat (^) from the maximum wheel speed V+n1.

[0034] In this way, the estimation unit 34 estimates the vehicle speed v hat (^) based on the maximum wheel speed among the wheel speeds v1, v2, v3, and v4 acquired at regular time intervals and the smoothed speed information.

[0035] The vehicle speed v(^) estimated by the estimation unit 34 is input to the ABS, which is one function of the electronically controlled brake system 11. The ABS calculates the slip ratio based on the vehicle speed v(^) and the wheel speeds v1, v2, v3, and v4, and adjusts the braking force of the wheels based on the calculated slip ratio.

[0036] FIG. 5A is a graph showing changes over time in speed information, wheel speed, and maximum wheel speed. In FIG. 5A, the speed information is shown by a dashed line, one of two wheel speeds is shown by a thick solid line, the other wheel speed is shown by a thin solid line, and the maximum wheel speed is shown by a medium-thick solid line. FIG. 5B is a graph showing changes over time in the vehicle speed estimated by the estimation unit in this embodiment, compared with the maximum wheel speed, etc. In FIG. 5B, the speed information is shown by a dashed line, the maximum wheel speed is shown by a medium-thick solid line, and the estimated vehicle speed is shown by a thick solid line. As shown in FIG. 5B, the estimation unit 34 smooths the speed information and estimates the vehicle speed v (^) based on the smoothed speed information, i.e., the speed n1 (^) and the maximum wheel speed V+n1. This improves the accuracy of vehicle speed estimation during braking, even when all wheels are slipping, thereby improving the accuracy of the slip ratio and suppressing deterioration of brake control performance.

[0037] The vehicle speed detection system 100 in the above embodiment is a vehicle speed detection system that estimates the body speed of the vehicle 1, and includes a first acquisition unit 32 that acquires the wheel speed of each of a plurality of wheels provided on the vehicle 1, a second acquisition unit 33 that acquires speed information measurable by a lidar 12 provided on the vehicle 1, and an estimation unit 34 that estimates the body speed v hat (^) based on the maximum wheel speed among the wheel speeds of each of the plurality of wheels and the speed information.

[0038] With the above configuration, when braking the vehicle 1, even if all the wheels slip, the vehicle speed v (^) can be estimated by combining the speed information and the maximum wheel speed, thereby improving the accuracy of estimating the vehicle speed when braking.

[0039] Furthermore, in the vehicle speed detection system 100 according to the above embodiment, the speed information is smoothed. This removes less important speed information, such as noise, and therefore makes it possible to further improve the accuracy of estimating the vehicle speed based on the speed information.

[0040] Furthermore, in the vehicle speed detection system 100 according to the above embodiment, the estimation unit 34 subtracts the difference between the maximum wheel speed and the smoothed speed information, which is obtained by applying the Kalman filter 343, from the maximum wheel speed, and estimates the subtracted value as the vehicle speed v (^). This makes it possible to accurately and efficiently estimate the vehicle speed using the maximum wheel speed and speed information that contain errors.

[0041] (Variation) A vehicle equipped with the vehicle speed detection system of the present disclosure and a Global Positioning System (GPS) 13 may include a correction unit 20 that corrects vehicle position information related to the Global Positioning System 13 based on the vehicle speed v(^) estimated by the estimation unit 34. This allows the vehicle position information based on the GPS to be determined taking into account the vehicle speed v(^) estimated by the estimation unit 34, thereby improving the accuracy of the vehicle position information.

[0042] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present disclosure, and the technical scope of the present disclosure should not be interpreted as being limited by these embodiments. In other words, the present disclosure can be carried out in various forms without departing from its gist or main features. [Industrial Applicability]

[0043] The present disclosure is suitably used in vehicles equipped with a vehicle speed detection system that is required to improve the accuracy of estimating vehicle speed during braking. [Explanation of symbols]

[0044] 1 vehicle 11 Electronically Controlled Brake System (EBS) 12 LiDAR 13 Global Positioning System (GPS) 20 Correction unit 30 Control Unit (ECU) 31 Control Unit 32 First acquisition part 33 Second acquisition part 34 Estimation part 341 Maximum Value Calculator 342 Differentiator 343 Kalman Filter 35 Storage section 100 Vehicle speed detection system

Claims

1. A vehicle speed detection system that estimates a vehicle speed, a first acquisition unit that acquires a wheel speed of each of a plurality of wheels provided on the vehicle; a second acquisition unit that acquires speed information measurable by a distance measurement sensor provided on the vehicle; an estimation unit that estimates the vehicle body speed based on a maximum wheel speed among the wheel speeds of the plurality of wheels and the speed information; A vehicle speed detection system.

2. The velocity information is smoothed velocity information. The vehicle speed detection system according to claim 1 .

3. the estimation unit subtracts a value obtained by applying a Kalman filter to a difference between the maximum wheel speed and the smoothed speed information from the maximum wheel speed, and estimates the subtracted value as the vehicle speed. The vehicle speed detection system according to claim 2 .

4. The vehicle speed detection system according to claim 1; a correction unit that corrects GPS-related vehicle position information based on the vehicle speed estimated by the estimation unit; A vehicle equipped with:

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