Vehicle speed estimation device, position calculation device, and program

Abstract

The invention provides a vehicle speed estimation device, a position calculation device, and a program capable of calculating the actual vehicle speed with high precision by correcting the speed of a vehicle calculated by a wheel speed sensor. The vehicle speed estimation device is provided with: a first vehicle speed calculation unit that calculates a first vehicle speed of a vehicle by means of a wheel speed sensor; a second vehicle speed calculation unit that calculates a second vehicle speed of the vehicle on the basis of a signal from the positioning satellite; a scale factor estimation unit that estimates a scale factor corresponding to the first vehicle speed on the basis of the relationship between the first vehicle speed and the ratio of the first vehicle speed to the second vehicle speed; and a vehicle speed estimation unit that estimates the actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on Japanese Patent Application No. 2023-049068 filed in Japan on March 24, 2023, and the contents of the underlying application are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to a vehicle speed estimating device and a program. Background Art

[0004] Patent Document 1 discloses a technology that estimates a speed error based on the correlation between the difference between the vehicle speed calculated from the wheel speed and the vehicle speed calculated from the GPS and the vehicle acceleration, and corrects the vehicle speed calculated from the wheel speed using the speed error.

[0005] Patent Document 1: Japanese Patent No. 6400450.

[0006] However, it is known that the error caused by the speed of the vehicle varies. In the technology described in Patent Document 1, the error cannot be corrected by the speed of the vehicle, and the accuracy of the estimated speed is low. Summary of the Invention

[0007] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a vehicle speed estimating device, a position calculating device, and a program capable of calculating the actual vehicle speed with high accuracy by correcting the vehicle speed calculated using a wheel speed sensor.

[0008] A first embodiment of a vehicle speed estimation device includes: a first vehicle speed calculation unit that calculates a first vehicle speed of the vehicle using a wheel speed sensor; a second vehicle speed calculation unit that calculates a second vehicle speed of the vehicle based on a signal from a positioning satellite; a proportional factor estimation unit that estimates a proportional factor corresponding to the first vehicle speed based on a relationship between the ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; and a vehicle speed estimation unit that estimates the actual vehicle speed by multiplying the first vehicle speed by the proportional factor.

[0009] According to the vehicle speed estimating device of the first aspect, it is possible to provide a vehicle speed estimating device capable of calculating the actual vehicle speed with high accuracy by correcting the vehicle speed calculated by the wheel speed sensor.

[0010] In the vehicle speed estimating device of the second embodiment, the proportional factor estimating unit divides the vehicle speed range into a plurality of speed ranges and estimates the proportional factor for each speed range.

[0011] According to the vehicle speed estimating device of the second aspect, it is possible to provide a vehicle speed estimating device capable of simplifying the process of estimating the scaling factor compared to the case of estimating the scaling factor for each first vehicle speed.

[0012] A vehicle speed estimating device according to a third embodiment includes an acceleration calculating unit that calculates acceleration based on a first vehicle speed, and a proportional factor estimating unit that estimates a proportional factor corresponding to the first vehicle speed based on a ratio between the first vehicle speed and the second vehicle speed and a relationship between the first vehicle speed and the acceleration.

[0013] According to the vehicle speed estimating device of the third aspect, it is possible to provide a vehicle speed estimating device capable of calculating the actual vehicle speed with higher accuracy than when the error in the first vehicle speed is corrected without using the vehicle acceleration.

[0014] The vehicle speed estimation device of the fourth embodiment includes an acceleration calculation unit, which uses an acceleration sensor to calculate the acceleration of the vehicle. In the proportional factor estimation unit, a proportional factor corresponding to the first vehicle speed and acceleration is estimated based on the ratio of the first vehicle speed to the second vehicle speed and the relationship between the first vehicle speed and the acceleration.

[0015] According to the vehicle speed estimating device of the fourth aspect, it is possible to provide a vehicle speed estimating device capable of calculating the actual vehicle speed with higher accuracy than when the error in the first vehicle speed is corrected without using the vehicle acceleration.

[0016] The vehicle speed estimating device of the fifth embodiment includes: an acceleration calculation unit for calculating the acceleration of the vehicle using an acceleration sensor; and a speed change calculation unit for calculating the amount of speed change, that is, the speed change amount, by integrating the acceleration. When the acceleration is below a threshold value, a proportional factor estimating unit estimates a proportional factor corresponding to the first vehicle speed based on the relationship between the ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed. In the vehicle speed estimating unit, when the acceleration is below the threshold value, the actual vehicle speed is estimated based on the proportional factor corresponding to the first vehicle speed. When the acceleration exceeds the threshold value, the actual vehicle speed is estimated by adding the speed change amount based on the acceleration to the first vehicle speed.

[0017] According to the vehicle speed estimating device of the fifth aspect, it is possible to provide a vehicle speed estimating device capable of calculating the actual vehicle speed with higher accuracy even when the acceleration is large.

[0018] The vehicle speed estimating device of the sixth embodiment includes: an acceleration calculation unit for calculating the acceleration of the vehicle using an acceleration sensor; and a time offset calculation unit for calculating the time offset between the first vehicle speed and the second vehicle speed based on the difference between the first vehicle speed and the second vehicle speed corrected for the acceleration by a proportional factor estimated by a proportional factor estimating unit based on the first vehicle speed. When the acceleration is below a threshold value, the proportional factor estimating unit estimates the proportional factor corresponding to the first vehicle speed based on the ratio of the first vehicle speed to the second vehicle speed and the relationship between the first vehicle speed. In the vehicle speed estimating unit, when the acceleration is below the threshold value, the actual vehicle speed is estimated based on the proportional factor corresponding to the first vehicle speed. When the acceleration exceeds the threshold value, the time offset with reference to the first vehicle speed is made by an amount corresponding to the time offset and the actual vehicle speed is output.

[0019] According to the vehicle speed estimating device of the sixth aspect, the actual vehicle speed can be calculated with higher accuracy regardless of the magnitude of the acceleration.

[0020] The seventh type of position calculation device is a vehicle speed estimating device that estimates the actual vehicle speed of the vehicle and calculates the position of the vehicle based on the actual vehicle speed estimated by the vehicle speed estimating device, wherein the vehicle speed estimating device includes: a first vehicle speed calculation unit that calculates the first vehicle speed of the vehicle using a wheel speed sensor; a second vehicle speed calculation unit that calculates the second vehicle speed of the vehicle based on a signal from a positioning satellite; a proportional factor estimating unit that estimates a proportional factor corresponding to the first vehicle speed based on the ratio of the first vehicle speed to the second vehicle speed and the relationship between the first vehicle speed; and a vehicle speed estimating unit that multiplies the first vehicle speed by the proportional factor to estimate the actual vehicle speed of the vehicle.

[0021] According to the position calculation device of the seventh aspect, it is possible to provide a position calculation device capable of calculating the position of a vehicle with high accuracy based on the vehicle speed with high accuracy.

[0022] The program of the eighth method enables the computer to function as a first vehicle speed calculation unit, a second vehicle speed calculation unit, a proportional factor estimation unit, and a vehicle speed estimation unit, wherein the above-mentioned first vehicle speed calculation unit uses a wheel speed sensor to calculate the first vehicle speed of the vehicle, the above-mentioned second vehicle speed calculation unit calculates the second vehicle speed of the vehicle based on a signal from a positioning satellite, the above-mentioned proportional factor estimation unit estimates the proportional factor corresponding to the first vehicle speed based on the ratio of the first vehicle speed to the second vehicle speed and the relationship between the first vehicle speed, and the above-mentioned vehicle speed estimation unit multiplies the first vehicle speed by the proportional factor to estimate the actual vehicle speed.

[0023] According to the program of the eighth aspect, it is possible to provide a program capable of calculating the actual vehicle speed with high accuracy by correcting the vehicle speed calculated by the wheel speed sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a block diagram showing an example of the configuration of the vehicle speed estimating system according to the first embodiment.

[0025] Figure 2 This is a schematic block diagram of the vehicle speed estimating device according to the first embodiment.

[0026] Figure 3 This is an explanatory diagram showing the relationship between the actual vehicle speed and the proportional factor with respect to the wheel speed in the first embodiment.

[0027] Figure 4 This is an explanatory diagram for explaining an example of the flow of operations of the vehicle speed estimating device according to the first embodiment.

[0028] Figure 5 This is an explanatory diagram for explaining an example of the flow of operations of the vehicle speed estimating device according to the second embodiment.

[0029] Figure 6 This is a block diagram showing an example of the configuration of a vehicle speed estimating system according to a third embodiment.

[0030] Figure 7 This is an explanatory diagram for explaining an example of the flow of operations of the vehicle speed estimating device according to the third embodiment.

[0031] Figure 8 This is a block diagram showing an example of the configuration of a vehicle speed estimating system according to a fourth embodiment.

[0032] Figure 9 This is a block diagram showing an example of the configuration of a vehicle speed estimating system according to a fifth embodiment.

[0033] Figure 10 This is a block diagram showing an example of the configuration of a vehicle speed estimating system according to a sixth embodiment.

[0034] Figure 11 It is an explanatory diagram for explaining the timing shift in the sixth embodiment. DETAILED DESCRIPTION

[0035] Hereinafter, an example of this embodiment will be described in detail with reference to the drawings.

[0036] [First embodiment]

[0037] Figure 1 1 is a block diagram showing an example of the system configuration of the vehicle speed estimation system 10 according to the first embodiment. Figure 1 As shown, the vehicle speed estimation system 10 of the present embodiment includes a wheel speed sensor 50 , a GNSS (Global Navigation Satellite System) receiver 60 , a vehicle speed estimation device 100 , and a position calculation device 200 .

[0038] The wheel speed sensor 50 is mounted on the vehicle and detects the number of pulses generated by the rotation of the tire per unit time, and transmits the detected number of pulses to the first vehicle speed calculation unit 110 .

[0039] The GNSS receiver 60 receives signals from positioning satellites and transmits the received signals to the second vehicle speed calculation unit 120 .

[0040] The vehicle speed estimation device 100 is a device for estimating the speed of a vehicle. Furthermore, the vehicle speed estimation device 100 is mounted on the vehicle whose speed is being estimated. Furthermore, the vehicle speed estimation device 100 is not limited to being entirely mounted on the vehicle whose speed is being estimated. Part of the structure of the vehicle speed estimation device 100 may be incorporated into another device connected to the vehicle via a network (not shown).

[0041] The position calculation device 200 calculates the vehicle's position based on the vehicle speed estimated by the vehicle speed estimation device 100. Furthermore, the position calculation device 200 is mounted on the vehicle whose position is being calculated. Furthermore, the position calculation device 200 is not limited to being mounted on the vehicle; it may also be provided by another device connected to the vehicle via a network (not shown). Furthermore, the position calculation device 200 is not limited to being provided as a separate device from the vehicle speed estimation device 100; its functionality may also be provided by the vehicle speed estimation device 100.

[0042] Figure 1 The vehicle speed estimation device 100 and position calculation device 200 of the illustrated configuration can be configured using a computer including a CPU, RAM, and a ROM storing programs and various data for executing the processing routines described below. Since the vehicle speed estimation device 100 and the position calculation device 200 are generally computer-based, the vehicle speed estimation device 100 will be used as a representative example for the following description.

[0043] Figure 2 2 is a block diagram showing the hardware configuration of the vehicle speed estimating device 100 .

[0044] like Figure 2 As shown, the vehicle speed estimation device 100 includes a CPU (Central Processing Unit) 101 , a ROM (Read Only Memory) 102 , a RAM (Random Access Memory) 103 , a storage 104 , an input unit 105 , a display unit 106 , and a communication unit 107 . These components are connected to each other via a bus 108 so as to be communicable with each other.

[0045] CPU 101 is a central processing unit (CPU) that executes various programs and controls various components. Specifically, CPU 101 reads programs from ROM 102 or storage 104 and executes them using RAM 103 as a work area. CPU 101 controls the various components described above and performs various calculations based on the programs stored in ROM 102 or storage 104. In this embodiment, programs are stored in ROM 102 or storage 104.

[0046] ROM 102 stores various programs and data. RAM 103 temporarily stores programs and data as a work area. Storage 104 is composed of a HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs including an operating system and various data.

[0047] The input unit 105 includes a pointing device such as a mouse and a keyboard, and is used for performing various inputs.

[0048] The display unit 106 is, for example, a liquid crystal display. The display unit 106 displays various information based on the control of the CPU 101. Alternatively, the display unit 106 may be a touch panel type and function as the input unit 105.

[0049] The communication unit 107 is used to communicate with the wheel speed sensor 50 , the GNSS receiver 60 , the position calculation device 200 , and the like.

[0050] The vehicle speed estimation device 100 uses the above-mentioned hardware resources to realize various functions. Figure 1 The functional structure implemented by the vehicle speed estimation device 100 will be described. Figure 1 As shown, the vehicle speed estimating device 100 functionally includes a first vehicle speed calculating unit 110 , a second vehicle speed calculating unit 120 , a scale factor estimating unit 130 , and a vehicle speed estimating unit 140 .

[0051] The first vehicle speed calculation unit 110 calculates a first vehicle speed based on the number of tire pulses and tire circumference detected by the wheel speed sensor 50. Hereinafter, the first vehicle speed is also referred to as the "wheel speed." The calculated wheel speed is then passed to the scale factor estimation unit 130 and the vehicle speed estimation unit 140.

[0052] The second vehicle speed calculation unit 120 calculates the second vehicle speed based on the signals from the positioning satellites received by the GNSS receiver 60. Hereinafter, the second vehicle speed is also referred to as the "GNSS speed." The calculated GNSS speed is then passed to the scale factor estimation unit 130. The GNSS speed calculated based on the signals from the positioning satellites is more accurate than the wheel speed. Specifically, the GNSS speed calculated based on the signals from the positioning satellites is susceptible to influences such as visibility from the vehicle to the positioning satellites and the surrounding environment, such as buildings. However, it is known that the vehicle speed calculated based on Doppler information has a small offset component and is highly accurate.

[0053] The scaling factor estimation unit 130 estimates the scaling factor corresponding to the wheel speed based on the relationship between the ratio of the wheel speed to the GNSS speed (GNSS speed / wheel speed: the numerator is the GNSS speed and the denominator is the wheel speed) and the wheel speed. Specifically, the ratio of the wheel speed to the GNSS speed is calculated, and the scaling factor is calculated based on the relationship between the wheel speed and the GNSS speed. Figure 3 The calculated ratio is corrected based on the relationship between the wheel speeds shown in FIG. 1 and FIG. 2 to estimate the proportional factor. Figure 3 This diagram illustrates the relationship between the actual vehicle speed and the scaling factor for the wheel speed. Figure 3 The actual speed is the correct value of the vehicle's speed measured by the measuring device. Figure 3 The point in is the wheel speed, and is the scale factor of the estimated straight line. Figure 3 It can be seen that the faster the actual vehicle speed, the larger the proportional factor with the wheel speed. In other words, the faster the wheel speed, the greater the difference with the actual speed, so it can be seen that the proportional factor needs to be increased. Here, the proportional factor is estimated by using the relationship between the wheel speed and the actual vehicle speed calculated using the least squares method, but it is not limited to this. According to the above Figure 3 The straight line shown is constructed by forming a function of a scale factor whose slope and the point of tangency with the axis are linearly expressed. The scale factor is estimated by substituting the wheel speed into the above function. Alternatively, the scale factor can be estimated by calculating the ratio of the wheel speed to the GNSS speed after correcting the wheel speed according to the change in tire radius. The scale factor function is not limited to a linear formula.

[0054] Here, the cause of the error is explained. The radius of the tire changes due to the type of tire, air pressure, wear rate, etc., so the proportional factor is estimated based on the state of the tire mounted on the vehicle to calculate the actual speed of the vehicle. However, it is known that the radius of the tire changes according to the speed of the moving vehicle due to centrifugal force, temperature (air pressure) changes, etc. Therefore, the faster the speed, the greater the error between the wheel speed and the actual vehicle speed. That is, for example, if the proportional factor assuming a low-speed area is continuously used in a high-speed area, the position error of the vehicle continues to be generated toward the rear of the vehicle, and the position error increases. Therefore, by estimating the proportional factor based on the speed of the moving vehicle, the accuracy of the calculation of the actual speed of the vehicle can be improved.

[0055] The vehicle speed estimating unit 140 estimates the actual vehicle speed by multiplying the wheel speed by a proportional factor.

[0056] The calculation of the vehicle's actual speed will be described using a specific example. For example, when the wheel speed is 25 m / s and the GNSS speed is 26 m / s, the ratio of the wheel speed to the GNSS speed is 1.04. According to the function of the scale factor, if the wheel speed scale factor at 25 m / s is, for example, 0.998, then correcting the ratio of the wheel speed to the GNSS speed using the wheel speed scale factor yields 1.04 × 0.998 = 1.03792. This value becomes the scale factor estimated by the scale factor estimation unit 130. Multiplying the scale factor by the wheel speed of 25 m / s yields 25 m / s × 1.07676 = 25.948. This value becomes the actual vehicle speed estimated by the vehicle speed estimation unit 140.

[0057] The position calculation device 200 calculates the vehicle position based on the actual vehicle speed calculated by the vehicle speed estimation device 100. That is, in dead reckoning, which calculates the vehicle speed using the wheel speed, the vehicle's position in the course direction is calculated based on where the vehicle has traveled at the wheel speed.

[0058] Next, the operation of the vehicle speed estimating device 100 will be described.

[0059] Figure 4 This is an explanatory diagram showing an example of the flow of operations of the CPU 101 of the vehicle speed estimating device 100 according to the first embodiment.

[0060] First, in step S100, the first vehicle speed calculation unit 110 calculates the vehicle's wheel speed based on the number of tire pulses and tire circumference received from the wheel speed sensor 50. The second vehicle speed calculation unit 120 calculates the vehicle's GNSS speed based on signals from positioning satellites received by the GNSS receiver 60. The process then proceeds to step S102.

[0061] In step S102, the second vehicle speed calculation unit 120 determines the validity of the GNSS velocity. For example, the accuracy of the GNSS velocity is determined based on the DOP (Dilution of Precision), residual error, and the like. If the GNSS velocity is determined to be valid, the process proceeds to step S104. On the other hand, if the GNSS velocity is not determined to be valid, the process returns to step S100.

[0062] In step S104, the first vehicle speed calculation unit 110 determines the validity of the wheel speed. For example, it determines whether the acceleration is below a threshold value and the wheel speed is above a threshold value. If the acceleration exceeds the threshold value and the wheel speed is below the threshold value, the wheel speed is not determined to be valid. If the wheel speed is determined to be valid, the process proceeds to the next step S106. On the other hand, if the wheel speed is not determined to be valid, the process returns to step S100.

[0063] In step S106 , the ratio of the wheel speed to the GNSS speed and the function of the above-mentioned scaling factor are estimated or updated, and then the process proceeds to the next step S108 .

[0064] In step S108 , the scale factor is estimated using a function of the scale factor according to the wheel speed, and then the process proceeds to the next step S110 .

[0065] In step S110 , the wheel speed is multiplied by the scaling factor to estimate the actual vehicle speed. The above-mentioned process is then repeated.

[0066] Furthermore, the above-mentioned processing may be frequently changed or may be started at various triggers.

[0067] As described above, according to this embodiment, by correcting the vehicle speed calculated by wheel speed sensor 50, the actual vehicle speed can be calculated with high accuracy. Specifically, the actual vehicle speed can be calculated with high accuracy, taking into account changes in the tire radius that vary with vehicle speed. Furthermore, the vehicle's position can be calculated based on the calculated, highly accurate actual vehicle speed.

[0068] [Second embodiment]

[0069] Next, use Figure 5 The second embodiment will now be described. While the scale factor estimating unit 130 estimates the scale factor for each wheel speed in the first embodiment, the second embodiment differs in that the scale factor estimating unit 130 estimates the scale factor for each speed range. The following description will focus on the differences from the first embodiment, and any overlapping descriptions will be simplified or omitted.

[0070] The proportional factor estimating unit 130 estimates the proportional factors in the speed areas divided into a plurality of areas. For example, although not shown in the figure, the speed area is divided into three, namely, a low-speed area of ​​0 m / s and less than 10 m / s, a medium-speed area of ​​10 m / s and less than 20 m / s, and a high-speed area of ​​20 m / s and more. Furthermore, the proportional factor estimating unit 130 estimates the proportional factor at one speed in each speed area. Here, one speed includes the center point of each speed area, etc. The proportional factors of each speed area are connected by an approximate straight line, and a function of the proportional factor is prepared based on the approximate straight line. Furthermore, the proportional factor can be estimated based on various wheel speeds. In addition, the speed area is not limited to being divided into three, as long as there are two or more speed areas.

[0071] Next, the operation of the vehicle speed estimating device 100 will be described.

[0072] Figure 5 This is an explanatory diagram showing an example of the flow of operations of the CPU 101 of the vehicle speed estimating device 100 according to the second embodiment.

[0073] First, in step S200, the first vehicle speed calculation unit 110 calculates the vehicle's wheel speed based on the number of tire pulses and tire circumference received from the wheel speed sensor 50. The second vehicle speed calculation unit 120 calculates the vehicle's GNSS speed based on signals from positioning satellites received by the GNSS receiver 60. The process then proceeds to step S202.

[0074] In step S202, the second vehicle speed calculation unit 120 determines the validity of the GNSS velocity. For example, the accuracy of the GNSS velocity is determined based on the DOP (Dilution of Precision) and residual error. If the GNSS velocity is determined to be valid, the process proceeds to step S204. On the other hand, if the GNSS velocity is not determined to be valid, the process returns to step S200.

[0075] In step S204, the first vehicle speed calculation unit 110 determines the validity of the wheel speed. For example, it determines whether the acceleration is below a threshold and the wheel speed is above a threshold. If the acceleration exceeds the threshold and the wheel speed is below the threshold, the wheel speed is not determined to be valid. If the wheel speed is determined to be valid, the process proceeds to the next step S206. On the other hand, if the wheel speed is not determined to be valid, the process returns to step S200.

[0076] In step S206, the process is divided into a low speed range, a medium speed range, or a high speed range according to each wheel speed calculated in step S200, and then the process proceeds to step S208, step S210, or step S212, respectively.

[0077] In steps S208 , S210 , and S212 , the ratio of the wheel speed to the GNSS speed is estimated or updated, and the process proceeds to the next step S214 .

[0078] In step S214, the function of the scale factor is estimated or updated, and then the process proceeds to step S216.

[0079] In step S216, the scale factor is estimated using a function of the scale factor according to the wheel speed. Then, the process proceeds to the next step S218.

[0080] In step S218, the wheel speed is multiplied by the scaling factor to estimate the actual vehicle speed. The above-mentioned process is then repeated.

[0081] In the present embodiment, by configuring in this manner, the process of estimating the scale factor can be simplified compared to the case where the scale factor is estimated for each wheel speed.

[0082] [Third embodiment]

[0083] Next, use Figure 6 as well as Figure 7 A third embodiment will be described.

[0084] In the first embodiment described above, the scale factor estimating unit 130 did not consider the vehicle's acceleration (fore-aft acceleration) when estimating the scale factor. However, in the third embodiment, the scale factor estimating unit 130 differs in that it estimates the scale factor while taking acceleration into account. The following description will focus on the differences from the first embodiment, and any overlapping descriptions will be simplified or omitted.

[0085] like Figure 6 As shown, the vehicle speed estimating device 100 functionally includes an acceleration calculating unit 150 .

[0086] The acceleration calculation unit 150 calculates acceleration (fore-aft acceleration) based on the wheel speed. Acceleration is calculated using a known technique, for example, by estimating the slope of speed change based on time-differential or time-series data of the wheel speed.

[0087] Scale factor estimation unit 130 estimates a scale factor corresponding to the wheel speed based on the ratio of wheel speed to GNSS speed and the relationship between wheel speed and acceleration. Here, the wheel speed error is proportional to acceleration and has a negative correlation. That is, as acceleration increases, the error increases. Furthermore, the error varies proportionally with wheel speed. Therefore, scale factor estimation unit 130 estimates the wheel speed error using the following equation. The scale factor is then estimated using the corrected wheel speed that corrects for the error caused by acceleration.

[0088] [Formula 1]

[0089]

[0090] [Formula 2]

[0091] e=α e xV1 (2)

[0092] Here, V1 is the vehicle speed pulse speed before correction, x is the vehicle acceleration, and α is the coefficient. In addition, e is the estimated value of the wheel speed error, α e is the estimated value of coefficient α. e For example, the least square method is applied to the equation (1) to estimate the value. By using the least square method, the time required to obtain the estimated value α can be shortened. e The estimated value of the error is subtracted from the wheel speed to calculate the corrected wheel speed.

[0093] Here, the cause of the error caused by acceleration is explained. It is known that the radius of the tire changes due to changes in tire load, slip rate, etc. when the vehicle accelerates or decelerates. Therefore, a difference between the wheel speed and the actual vehicle speed occurs according to the acceleration. In addition, even if the tire radius does not change, if there is a time offset between the wheel speed and the actual vehicle speed, the timing of the speed change will also be offset, thus apparently generating a speed error proportional to the acceleration. Therefore, compared with using a scale factor estimated without assuming acceleration, the accuracy of the actual vehicle speed calculation can be improved by using an estimated scale factor. In the case of error estimation, the reference GNSS speed is regarded as the actual vehicle speed.

[0094] Next, the operation of the vehicle speed estimating device 100 will be described.

[0095] Figure 7 This is an explanatory diagram showing an example of the flow of operations of the vehicle speed estimating device 100 according to the third embodiment.

[0096] First, in step S300, the first vehicle speed calculation unit 110 calculates the vehicle's wheel speed based on the number of tire pulses and tire circumference received from the wheel speed sensor 50. The second vehicle speed calculation unit 120 calculates the vehicle's GNSS speed based on signals from positioning satellites received by the GNSS receiver 60. The process then proceeds to step S302.

[0097] In step S302 , the acceleration calculation unit 150 calculates the acceleration based on the wheel speed, and then proceeds to step S304 .

[0098] In step S304, the second vehicle speed calculation unit 120 determines the validity of the GNSS velocity. For example, the accuracy of the GNSS velocity is determined based on the DOP (Dilution of Precision) and residuals. If the GNSS velocity is determined to be valid, the process proceeds to step S306. On the other hand, if the GNSS velocity is not determined to be valid, the process returns to step S300.

[0099] In step S306, the first vehicle speed calculation unit 110 determines the validity of the wheel speed. For example, it determines whether the acceleration is below a threshold value and the wheel speed is above a threshold value. If the acceleration exceeds the threshold value and the wheel speed is below the threshold value, the wheel speed is not determined to be valid. If the wheel speed is determined to be valid, the process proceeds to the next step S308. On the other hand, if the wheel speed is not determined to be valid, the process returns to step S300.

[0100] In step S308 , the ratio of the wheel speed to the GNSS speed and the function of the above-mentioned scaling factor are estimated or updated, and then the process proceeds to the next step S310 .

[0101] In step S310 , the scale factor is estimated using a function of the scale factor according to the wheel speed, and then the process proceeds to the next step S312 .

[0102] In step S312, the wheel speed is multiplied by the scaling factor to estimate the actual vehicle speed. The above-mentioned process is then repeated.

[0103] In this embodiment, this configuration enables more accurate calculation of the actual vehicle speed. Specifically, while it is understood that vehicle acceleration or deceleration causes errors in the wheel speed based on the number of pulses from the wheel speed sensor 50, by correcting for these errors and estimating the proportionality factor, the actual vehicle speed can be calculated with greater accuracy than would be possible without error correction.

[0104] [Fourth embodiment]

[0105] Next, use Figure 8The fourth embodiment will now be described. While the acceleration calculation unit 150 estimated acceleration in the third embodiment, the fourth embodiment differs in that it uses an acceleration sensor to calculate acceleration. The following description will focus on the differences from the first embodiment, simplifying or omitting any overlapping descriptions.

[0106] The vehicle speed estimation system 10 further includes an acceleration sensor 70 .

[0107] The acceleration sensor 70 is mounted on the vehicle and detects the acceleration of the vehicle (front-rear acceleration) and transmits the detected acceleration to the acceleration calculation unit 150 .

[0108] The acceleration calculation unit 150 acquires the acceleration (fore-aft acceleration) detected by the acceleration sensor 70 .

[0109] In the scale factor estimating unit 130 , similarly to the third embodiment described above, a scale factor corresponding to the wheel speed is estimated based on the ratio between the wheel speed and the GNSS speed and the relationship between the wheel speed and the acceleration.

[0110] [Fifth embodiment]

[0111] Next, use Figure 9 The fifth embodiment will now be described. While the acceleration estimation scaling factor was considered in the third and fourth embodiments described above, the fifth embodiment estimates the actual vehicle speed by using the scaling factor similarly to the first embodiment when the acceleration is below a threshold. However, when the acceleration exceeds the threshold, the scaling factor is not used, and the actual vehicle speed is estimated based on the speed change due to acceleration. The description will focus on the differences from the above embodiments, and any overlapping descriptions will be simplified or omitted.

[0112] like Figure 9 As shown, the vehicle speed estimating device 100 functionally includes a speed change calculating unit 160 .

[0113] The speed change calculation unit 160 calculates the speed change amount, which is the amount of speed change, by integrating the acceleration.

[0114] When the acceleration calculated by the acceleration calculation unit 150 is below a threshold, the scaling factor estimation unit 130 estimates a scaling factor corresponding to the wheel speed based on the ratio of the wheel speed to the GNSS speed and the relationship between the wheel speed, similar to the first embodiment described above. Specifically, when the acceleration is low, the acceleration estimation scaling factor is ignored, while when the acceleration is high, no scaling factor is estimated. The acceleration threshold is preferably a value so low that the acceleration is considered to be substantially constant speed.

[0115] When the acceleration is below the threshold, the vehicle speed estimation unit 140 estimates the actual vehicle speed based on a proportional factor corresponding to the wheel speed estimated by the proportional factor estimation unit 130. Specifically, when the acceleration is negligibly small, the actual vehicle speed is estimated using the proportional factor, similar to the first embodiment.

[0116] Furthermore, when the acceleration exceeds a threshold, the vehicle speed estimation unit 140 estimates the actual vehicle speed by adding the speed change based on the acceleration to the wheel speed. Specifically, the vehicle speed is estimated by adding the speed change using the actual vehicle speed estimated based on the scaling factor when the acceleration exceeds the threshold as the initial value.

[0117] In the present embodiment, by configuring in this manner, the actual vehicle speed can be calculated with higher accuracy even when the acceleration is large.

[0118] [Sixth embodiment]

[0119] Next, use Figure 10 as well as Figure 11 The sixth embodiment will now be described. In the sixth embodiment, when the acceleration is below a threshold, the actual vehicle speed is estimated by taking into account the speed estimation scaling factor, similar to the first embodiment. However, when the acceleration exceeds the threshold, the reference wheel speed timing is corrected based on the magnitude of the time offset between the estimated wheel speed and the GNSS speed. The following description will focus on the differences from the above embodiments, and any overlapping descriptions will be simplified or omitted.

[0120] like Figure 10 As shown, the vehicle speed estimation device 100 functionally includes a time offset calculation unit 170 .

[0121] The time offset calculation unit 170 calculates the time offset between the wheel speed and the GNSS speed based on the difference between the wheel speed and the GNSS speed after the acceleration is corrected by a proportional factor corresponding to the speed.

[0122] The scale factor estimating unit 130 is the same as that of the fifth embodiment.

[0123] The vehicle speed estimating unit 140 estimates the actual vehicle speed based on the proportional factor corresponding to the wheel speed estimated by the proportional factor estimating unit 130. Figure 11 As shown, as the vehicle speed at time t0, the actual vehicle speed is outputted by shifting the reference wheel speed by an amount corresponding to the timing shift amount estimated by the timing shift calculation unit 170.

[0124] Here, the causes of time offset are explained. Even when the wheel speed and GNSS speed are identical, there may be a time offset between them due to processing delays within the wheel speed sensor 50 and GNSS receiver 60. Generally, GNSS speed is assigned the highly accurate time information inherent to GNSS. On the other hand, the wheel speed sensor 50 and acceleration sensor 70 are not assigned time information, so they are assigned time information to account for sensor delays used for processing. Therefore, even if the difference from the GNSS speed is relatively small, a time offset may still occur.

[0125] Figure 11 The relationship between the wheel speed corrected by the proportional factor according to the speed and the GNSS speed in the case where there is a time offset between the wheel speed and the GNSS speed is shown. Figure 11 (A) is the case of wheel speed delay, Figure 11 (B) is the case where the wheel speed is ahead. Figure 11 As shown in the figure, when the magnitude of the time offset is ΔT, if ΔT is sufficiently small and the acceleration x is considered to be a constant value, the velocity error becomes ΔT·x. Moreover, due to the advance or delay of the time offset, the sign of ΔT changes, and the slope of the velocity error is proportional to ΔT (see Figure 11 (A) right and Figure 11 (B) solid line on the right). Here, Figure 11 The right picture of (A) and Figure 11 The solid line in the right graph of (B) represents the "speed error relative to acceleration" when there is a time offset. The dashed line represents the "speed error relative to acceleration" when using the wheel speed before or after ΔT. Furthermore, if the acceleration changes to a value that cannot be considered constant during ΔT, the speed error is not ΔT·x, but corresponds to the value obtained by integrating the acceleration over the time period of ΔT.

[0126] The magnitude of the time offset ΔT is calculated using the following steps. First, similar to the fifth embodiment, the scale factor estimation unit 130 estimates a scale factor corresponding to the velocity only when the acceleration is below a threshold. Next, when the acceleration exceeds the threshold, the time offset calculation unit 170 observes whether the velocity error or the scale factor change is positive or negative, and calculates the slope relative to the acceleration using the least squares method. This slope represents the magnitude of the time offset ΔT. The positive or negative sign of the slope corresponds to the advance or delay of the time offset.

[0127] Here, if the error due to acceleration is directly reflected in the change in the scale factor to estimate the velocity, it is the same as the third and fourth embodiments. On the other hand, the sixth embodiment is different in that the magnitude of the time offset ΔT is calculated to correct the time offset, thereby reducing the error due to acceleration.

[0128] exist Figure 11 In the example, t0 represents the time of the current reference GNSS speed, which is the case when the wheel speed is offset by ΔT. Figure 11 In (A), the wheel speed is delayed, so the wheel speed after ΔT can be used as the wheel speed at time t0 as the speed at the same time as the GNSS speed at time t0. Figure 11 In (B), the wheel speed is ahead, so the wheel speed ΔT before can be used as the reference wheel speed at time t0. Alternatively, integrating the acceleration over the time interval that shifts the reference time and adding the original wheel speed can achieve the same effect as shifting the reference time.

[0129] In the present embodiment, by configuring in this manner, the actual vehicle speed can be calculated with higher accuracy regardless of the magnitude of the acceleration.

[0130] Furthermore, the time shift may be corrected by directly shifting the time of the reference wheel speed and estimating the vehicle speed by adding the speed change obtained by integrating the acceleration within the time interval of the time shift. The same effect can be achieved.

[0131] The above description uses the vehicle speed estimation device 100 and the position calculation device 200 as examples of embodiments. Embodiments may also be implemented as programs for causing a computer to execute the functions of the various components of the vehicle speed estimation device 100 and the position calculation device 200. Embodiments may also be implemented as computer-readable non-transitory storage media storing these programs.

[0132] In addition, the present disclosure is not limited to the above-described embodiment, and various modifications other than the above-described configuration are possible without departing from the gist of the present disclosure.

[0133] Furthermore, the process flow of the program described in the above embodiment is merely an example, and therefore, in the above embodiment, unnecessary steps may be deleted, new steps may be added, or the processing order may be changed without departing from the spirit of the present invention.

[0134] In the above embodiments, the processing involved in the embodiments is implemented by a computer using a software configuration by executing a program, but the present invention is not limited thereto. The embodiments may also be implemented by hardware configuration or a combination of hardware and software configurations.

Claims

1. A vehicle speed estimation device comprising: a first vehicle speed calculation unit for calculating a first vehicle speed of the vehicle using a wheel speed sensor; a second vehicle speed calculation unit for calculating a second vehicle speed of the vehicle based on a signal from a positioning satellite; a proportional factor estimating unit that estimates a proportional factor corresponding to the first vehicle speed based on a relationship between the ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; as well as a vehicle speed estimating unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the proportional factor; and 2. The vehicle speed estimating device according to claim 1, wherein: The scale factor estimating unit divides the vehicle speed range into a plurality of speed ranges and estimates a scale factor for each speed range.

3. The vehicle speed estimating device according to claim 1 or 2, wherein: An acceleration calculation unit is provided, wherein the acceleration calculation unit calculates acceleration based on the first vehicle speed. The proportional factor estimating unit estimates a proportional factor corresponding to the first vehicle speed based on a ratio between the first vehicle speed and the second vehicle speed and a relationship between the first vehicle speed and the acceleration.

4. The vehicle speed estimating device according to claim 1 or 2, wherein: An acceleration calculation unit is provided, wherein the acceleration calculation unit calculates the acceleration of the vehicle using an acceleration sensor. The proportional factor estimating unit estimates a proportional factor corresponding to the first vehicle speed and the acceleration based on a ratio between the first vehicle speed and the second vehicle speed and a relationship between the first vehicle speed and the acceleration.

5. The vehicle speed estimating device according to claim 1 or 2, wherein: have: an acceleration calculation unit that calculates the acceleration of the vehicle using the acceleration sensor; and The speed change calculation unit calculates the speed change amount by integrating the acceleration. The proportional factor estimating unit estimates a proportional factor corresponding to the first vehicle speed based on a ratio of the first vehicle speed to the second vehicle speed and a relationship between the first vehicle speed when the acceleration is equal to or less than a threshold value. In the vehicle speed estimating unit, when the acceleration is below a threshold value, the actual vehicle speed is estimated based on a proportional factor corresponding to the first vehicle speed. When the acceleration exceeds the threshold value, the actual vehicle speed is estimated by adding the speed change based on the acceleration to the first vehicle speed.

6. The vehicle speed estimating device according to claim 1 or 2, wherein: have: An acceleration calculation unit calculates the acceleration of the vehicle using an acceleration sensor; and a time offset calculation unit that calculates a time offset between the first vehicle speed and the second vehicle speed based on a difference between the first vehicle speed and the second vehicle speed corrected by the proportional factor estimated by the proportional factor estimating unit based on the first vehicle speed, with respect to the acceleration; The proportional factor estimating unit estimates a proportional factor corresponding to the first vehicle speed based on a ratio of the first vehicle speed to the second vehicle speed and a relationship between the first vehicle speed when the acceleration is equal to or less than a threshold value. In the vehicle speed estimating unit, when the acceleration is below a threshold value, the actual vehicle speed is estimated based on a proportional factor corresponding to the first vehicle speed. When the acceleration exceeds the threshold value, the time at which the first vehicle speed is referenced is offset by an amount corresponding to the time offset, and the actual vehicle speed is output.

7. A position calculation device, comprising: a vehicle speed estimating device for estimating an actual vehicle speed; and a device for calculating a position of the vehicle based on the actual vehicle speed estimated by the vehicle speed estimating device, wherein: The vehicle speed estimating device comprises: a first vehicle speed calculation unit, configured to calculate a first vehicle speed of the vehicle using a wheel speed sensor; a second vehicle speed calculation unit for calculating a second vehicle speed of the vehicle based on a signal from a positioning satellite; a proportional factor estimating unit that estimates a proportional factor corresponding to the first vehicle speed based on a ratio of the first vehicle speed to the second vehicle speed and a relationship between the first vehicle speed; as well as The vehicle speed estimating unit estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the proportional factor.

8. A program for causing a computer to function as a first vehicle speed calculation unit, a second vehicle speed calculation unit, a proportional factor estimation unit, and a vehicle speed estimation unit, wherein: The first vehicle speed calculation unit calculates a first vehicle speed of the vehicle using a wheel speed sensor. The second vehicle speed calculation unit calculates a second vehicle speed of the vehicle based on a signal from a positioning satellite. The proportional factor estimating unit estimates a proportional factor corresponding to the first vehicle speed based on a relationship between the ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed. The vehicle speed estimating unit estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the proportional factor.

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