Vehicle speed estimation device, position calculation device and program

Abstract

To provide a vehicle speed estimation device, a position calculation device, and a program capable of calculating actual vehicle speed with high accuracy by correcting vehicle speed calculated using a wheel speed sensor.SOLUTION: A vehicle speed estimation device includes: a first vehicle speed calculation unit for calculating first vehicle speed of a vehicle by a wheel speed sensor; a second vehicle speed calculation unit for calculating second vehicle speed of the vehicle based on a signal from a positioning satellite; a scale factor estimation unit for estimating a scale factor corresponding to the first vehicle speed from a relationship between ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; and a vehicle speed estimation unit for estimating actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle speed estimation device and a program. [Background technology]

[0002] Patent Document 1 discloses a technology that estimates a speed error from the correlation between the difference between the vehicle speed calculated from the wheel speed and the vehicle speed calculated by GPS, and the vehicle acceleration, and corrects the vehicle speed calculated from the wheel speed using the speed error. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6400450 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is known that errors occur depending on the vehicle speed, and the technique described in Patent Document 1 cannot correct errors depending on the vehicle speed, resulting in low accuracy in the estimated speed.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a vehicle speed estimation device, a position calculation device, and a program that can calculate the actual vehicle speed with high accuracy by correcting the vehicle speed calculated using a wheel speed sensor. [Means for solving the problem]

[0006] A vehicle speed estimation device according to a first aspect includes a first vehicle speed calculation unit that calculates a first vehicle speed of a 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 scale factor estimation unit that estimates a scale factor corresponding to the first vehicle speed based on a ratio between the first vehicle speed and the second vehicle speed and a relationship with the first vehicle speed; and a vehicle speed estimation unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor.

[0007] According to the vehicle speed estimation device of the first aspect, it is possible to provide a vehicle speed estimation device that can calculate the actual vehicle speed with high accuracy by correcting the vehicle speed calculated using the wheel speed sensor.

[0008] In the vehicle speed estimation device according to a second aspect, the scale factor estimation unit divides the speed range of the vehicle into a plurality of speed ranges and estimates a scale factor for each of the speed ranges.

[0009] According to the vehicle speed estimation device of the second aspect, it is possible to provide a vehicle speed estimation device that can simplify the process of estimating the scale factor compared to when the scale factor is estimated for each first vehicle speed.

[0010] A vehicle speed estimation device according to a third aspect includes an acceleration calculation unit that calculates acceleration from the first vehicle speed, and the scale factor estimation unit estimates a scale factor corresponding to the first vehicle speed from the ratio between the first vehicle speed and the second vehicle speed and the relationship between the first vehicle speed and the acceleration.

[0011] According to the vehicle speed estimation device of the third aspect, it is possible to provide a vehicle speed estimation device that can calculate the actual vehicle speed more accurately than when the error in the first vehicle speed is not corrected using the vehicle acceleration.

[0012] A vehicle speed estimation device according to a fourth aspect includes an acceleration calculation unit that calculates the acceleration of the vehicle using an acceleration sensor, and the scale factor estimation unit estimates a scale factor corresponding to the first vehicle speed and the acceleration from the ratio between the first vehicle speed and the second vehicle speed and the relationship between the first vehicle speed and the acceleration.

[0013] According to the vehicle speed estimation device of the fourth aspect, it is possible to provide a vehicle speed estimation device that can calculate the actual vehicle speed more accurately than when the error in the first vehicle speed is not corrected using the vehicle acceleration.

[0014] A vehicle speed estimation device according to a fifth aspect includes an acceleration calculation unit that calculates the acceleration of the vehicle using an acceleration sensor, and a speed change calculation unit that calculates a speed change amount, which is the amount of change in speed, by integrating the acceleration, and is characterized in that, when the acceleration is equal to or less than a threshold value, the scale factor estimation unit estimates a scale factor corresponding to the first vehicle speed from the relationship between the ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed, and when the acceleration is equal to or less than the threshold value, the vehicle speed estimation unit estimates the actual vehicle speed based on the scale factor corresponding to the first vehicle speed, and when the acceleration exceeds the threshold value, estimates the actual vehicle speed by adding the speed change amount based on the acceleration to the first vehicle speed.

[0015] According to the vehicle speed estimation device of the fifth aspect, it is possible to provide a vehicle speed estimation device that can calculate the actual vehicle speed with higher accuracy even when the acceleration is large.

[0016] A vehicle speed estimation device according to a sixth aspect includes an acceleration calculation unit that 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 from a difference between the first vehicle speed and the second vehicle speed corrected by a scale factor estimated by the scale factor estimation unit according to the first vehicle speed relative to the acceleration, wherein when the acceleration is equal to or less than a threshold value, the scale factor estimation unit estimates a scale factor according to the first vehicle speed from the relationship between the ratio between the first vehicle speed and the second vehicle speed and the first vehicle speed, and when the acceleration is equal to or less than the threshold value, the vehicle speed estimation unit estimates the actual vehicle speed based on the scale factor according to the first vehicle speed, and when the acceleration exceeds the threshold value, shifts the time at which the first vehicle speed is referenced by an amount corresponding to the time offset and outputs the actual vehicle speed.

[0017] According to the vehicle speed estimation device of the sixth aspect, it is possible to calculate the actual vehicle speed with higher accuracy regardless of the magnitude of the acceleration.

[0018] A position calculation device according to a seventh aspect is a position calculation device that includes a vehicle speed estimation device that estimates an actual vehicle speed of a vehicle, and a position calculation device that calculates the position of the vehicle from the actual vehicle speed estimated by the vehicle speed estimation device, wherein the 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 scale factor estimation unit that estimates a scale factor corresponding to the first vehicle speed from the 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 of the vehicle by multiplying the first vehicle speed by the scale factor.

[0019] According to the position calculation device of the seventh aspect, it is possible to provide a position calculation device that can calculate the position of a vehicle with high accuracy based on the vehicle speed with high accuracy.

[0020] A program according to an eighth aspect causes a computer to function as a first vehicle speed calculation unit that calculates a first vehicle speed of a 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 scale factor estimation unit that estimates a scale 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, and a vehicle speed estimation unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor.

[0021] According to the program of the eighth aspect, it is possible to provide a program that can calculate the actual vehicle speed with high accuracy by correcting the vehicle speed calculated using the wheel speed sensor. [Effects of the Invention]

[0022] The present invention has an effect of being able to calculate the actual vehicle speed with high accuracy by correcting the vehicle speed calculated using the wheel speed sensors. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a block diagram showing an example of the configuration of a vehicle speed estimation system according to a first embodiment. [Figure 2] 1 is a schematic block diagram of a vehicle speed estimation device according to a first embodiment. [Figure 3] FIG. 4 is an explanatory diagram showing the relationship between the actual vehicle speed and the scale factor for the wheel speed according to the first embodiment. [Figure 4] FIG. 2 is an explanatory diagram for explaining an example of the flow of operations of the vehicle speed estimation device according to the first embodiment. [Figure 5] FIG. 10 is an explanatory diagram for explaining an example of the flow of operations of the vehicle speed estimation device according to the second embodiment. [Figure 6] FIG. 10 is a block diagram showing an example of the configuration of a vehicle speed estimation system according to a third embodiment. [Figure 7] FIG. 11 is an explanatory diagram for explaining an example of the flow of operations of the vehicle speed estimation device according to the third embodiment. [Figure 8]FIG. 10 is a block diagram showing an example of the configuration of a vehicle speed estimation system according to a fourth embodiment. [Figure 9] FIG. 10 is a block diagram showing an example of the configuration of a vehicle speed estimation system according to a fifth embodiment. [Figure 10] FIG. 13 is a block diagram showing an example of the configuration of a vehicle speed estimation system according to a sixth embodiment. [Figure 11] FIG. 20 is an explanatory diagram for explaining a time difference according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] An example of this embodiment will be described in detail below with reference to the drawings.

[0025] [First embodiment] 1 is a block diagram showing an example of the system configuration of a vehicle speed estimation system 10 according to the first embodiment. As shown in FIG. 1, the vehicle speed estimation system 10 according to this 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.

[0026] 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. The detected number of pulses is then passed to the first vehicle speed calculation unit 110.

[0027] The GNSS receiver 60 receives signals from positioning satellites and passes the received signals to the second vehicle speed calculation unit 120.

[0028] The vehicle speed estimation device 100 is a device that estimates the speed of a vehicle. The vehicle speed estimation device 100 is mounted on a vehicle whose vehicle speed is to be estimated. Note that the entire configuration of the vehicle speed estimation device 100 is not limited to being mounted on the vehicle whose vehicle speed is to be estimated, and part of the configuration of the vehicle speed estimation device 100 may be provided in another device that is connected to the vehicle via a network (not shown).

[0029] The position calculation device 200 is a device that calculates the position of a vehicle based on the vehicle speed of the vehicle estimated by the vehicle speed estimation device 100. The position calculation device 200 is mounted on the vehicle whose position is to be calculated. The position calculation device 200 is not limited to being mounted on the vehicle, but may be provided in another device connected to the vehicle via a network (not shown). The position calculation device 200 is not limited to being provided as a device separate from the vehicle speed estimation device 100, but the vehicle speed estimation device 100 may have its functions.

[0030] 1 can be configured by a computer including a CPU, a RAM, and a ROM storing programs for executing each processing routine described below and various data. Since the vehicle speed estimation device 100 and the position calculation device 200 basically have a general computer configuration, the vehicle speed estimation device 100 will be described as a representative.

[0031] FIG. 2 is a block diagram showing the hardware configuration of the vehicle speed estimation device 100. As shown in FIG.

[0032] 2, 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. Each component is connected to each other via a bus 108 so as to be able to communicate with each other.

[0033] The CPU 101 is a central processing unit that executes various programs and controls each component. That is, the CPU 101 reads programs from the ROM 102 or storage 104 and executes the programs using the RAM 103 as a work area. The CPU 101 controls the above components and performs various arithmetic processing in accordance with the programs recorded in the ROM 102 or storage 104. In this embodiment, the programs are stored in the ROM 102 or storage 104.

[0034] The ROM 102 stores various programs and various data. The RAM 103 temporarily stores programs or data as a working area. The storage 104 is configured with an HDD (Hard Disk Drive) or an SSD (Solid State Drive) and stores various programs including an operating system and various data.

[0035] The input unit 105 includes a pointing device such as a mouse and a keyboard, and is used to perform various inputs.

[0036] The display unit 106 is, for example, a liquid crystal display. The display unit 106 displays various information under the control of the CPU 101. The display unit 106 may also function as the input unit 105 by employing a touch panel system.

[0037] The communication unit 107 is for communicating with the wheel speed sensor 50, the GNSS receiver 60, the position calculation device 200, and the like.

[0038] The vehicle speed estimation device 100 realizes various functions using the above hardware resources. The functional configuration realized by the vehicle speed estimation device 100 will be described with reference to Fig. 1. As shown in Fig. 1, the vehicle speed estimation device 100 functionally includes a first vehicle speed calculation unit 110, a second vehicle speed calculation unit 120, a scale factor estimation unit 130, and a vehicle speed estimation unit 140.

[0039] The first vehicle speed calculation unit 110 calculates a first vehicle speed (hereinafter also referred to as "wheel speed") of the vehicle from the number of pulses of the tire and the circumference of the tire detected by the wheel speed sensor 50. Then, the calculated wheel speed is passed to the scale factor estimation unit 130 and the vehicle speed estimation unit 140.

[0040] The second vehicle speed calculation unit 120 calculates a second vehicle speed (hereinafter also referred to as "GNSS speed") of the vehicle based on signals from positioning satellites received by the GNSS receiver 60. Then, the calculated GNSS speed is passed to the scale factor estimation unit 130. Here, the GNSS speed calculated based on signals from positioning satellites is more accurate than the wheel speed. That is, the GNSS speed calculated based on signals from positioning satellites is easily affected by the visibility of the positioning satellites from the vehicle and the surrounding environment of the vehicle, such as buildings, but the vehicle speed calculated from Doppler information is known to have a small offset component and high accuracy.

[0041] The scale factor estimation unit 130 estimates a scale factor corresponding to the wheel speed from 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 scale factor is estimated by calculating the ratio of the wheel speed to the GNSS speed and correcting the calculated ratio based on the relationship with the wheel speed shown in FIG. 3. FIG. 3 is an explanatory diagram showing the relationship between the actual vehicle speed and the scale factor for the wheel speed. The actual speed in FIG. 3 is the correct value of the vehicle speed measured by a measuring instrument. The points in FIG. 3 represent the wheel speed, and the straight line represents the estimated scale factor. FIG. 3 shows that the faster the actual vehicle speed, the larger the scale factor for the wheel speed. In other words, it can be seen that the faster the wheel speed, the larger the difference from the actual speed, and therefore the larger the scale factor must be. Here, the scale factor is estimated based on the relationship between the wheel speed and the actual vehicle speed calculated using the least squares method, but is not limited to this. Based on the straight line shown in Figure 3, a scale factor function is created by converting the slope and the tangent point with the axis into a linear equation. The scale factor is then estimated by inputting the wheel speed into this function. Note that the scale factor may also be estimated by correcting the wheel speed according to the wheel speed in consideration of changes in tire radius and then calculating the ratio between the wheel speed and the GNSS speed. The scale factor function is not limited to a linear equation.

[0042] Here, we will explain the cause of the error. Because tire radius varies depending on the tire type, air pressure, wear rate, etc., a scale factor is estimated from the condition of the tires mounted on the vehicle to calculate the vehicle's actual speed. However, it is known that tire radius changes depending on the speed of a traveling vehicle due to changes in centrifugal force and temperature (air pressure). Therefore, the error between the wheel speed and the actual vehicle speed increases as the speed increases. In other words, for example, if a scale factor designed for a low speed range is continuously used in a high speed range, vehicle position errors will continue to occur in the rear direction of the vehicle, increasing the position error. Therefore, by estimating a scale factor according to the speed of the traveling vehicle, it is possible to improve the accuracy of calculating the vehicle's actual speed.

[0043] The vehicle speed estimation unit 140 estimates the actual vehicle speed by multiplying the wheel speed by a scale factor.

[0044] A specific example of how to calculate the actual vehicle speed will be described. For example, if the wheel speed is 25 m / s and the GNSS speed is 26 m / s, the ratio between the wheel speed and the GNSS speed is 1.04. From the scale factor function, if the wheel speed scale factor at 25 m / s is, for example, 0.998, the ratio between the wheel speed and the GNSS speed is corrected with the wheel speed scale factor to obtain 1.04 × 0.998 = 1.03792. This value is the scale factor estimated by the scale factor estimation unit 130. Multiplying the wheel speed of 25 m / s by the scale factor yields 25 m / s × 1.07676 = 25.948. This value is the actual vehicle speed estimated by the vehicle speed estimation unit 140.

[0045] The position calculation device 200 calculates the position of the vehicle 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 position calculation device 200 calculates the vehicle's position along the road based on how far the vehicle has traveled at the wheel speed.

[0046] Next, the operation of the vehicle speed estimation device 100 will be described.

[0047] FIG. 4 is an explanatory diagram showing an example of the flow of operations performed by the CPU 101 of the vehicle speed estimation device 100 of the first embodiment.

[0048] First, in step S100, the first vehicle speed calculation unit 110 calculates the wheel speed of the vehicle from the tire pulse count and tire circumference received from the wheel speed sensor 50, and the second vehicle speed calculation unit 120 calculates the GNSS speed of the vehicle based on signals from positioning satellites received by the GNSS receiver 60. Then, the process proceeds to the next step S102.

[0049] In step S102, the second vehicle speed calculation unit 120 determines the validity of the GNSS speed. For example, the accuracy of the GNSS speed is determined from the DOP (Dilution Of Precision), residual error, etc. If it is determined that the GNSS speed is valid, the process proceeds to the next step S104. On the other hand, if it is not determined that the GNSS speed is valid, the process returns to step S100 described above.

[0050] In step S104, the first vehicle speed calculation unit 110 determines whether the wheel speed is valid. For example, it determines whether the acceleration is equal to or less than a threshold value or whether the wheel speed is equal to or greater than a threshold value. If the acceleration exceeds the threshold value or if the wheel speed is less than the threshold value, it does not determine that the wheel speed is valid. If it determines that the wheel speed is valid, it proceeds to the next step S106. On the other hand, if it does not determine that the wheel speed is valid, it returns to step S100 described above again.

[0051] In step S106, the ratio between the wheel speed and the GNSS speed and the scale factor function described above are estimated or updated, and the process then proceeds to the next step, S108.

[0052] In step S108, the scale factor is estimated from the wheel speed using a scale factor function, and the process then proceeds to the next step S110.

[0053] In step S110, the wheel speed is multiplied by a scale factor to estimate the actual vehicle speed, and this process is then repeated.

[0054] This process may be repeated continuously or may be initiated at various times.

[0055] As described above, according to this embodiment, the actual vehicle speed can be calculated with high accuracy by correcting the vehicle speed calculated using the wheel speed sensor 50. That is, the actual vehicle speed can be calculated with high accuracy by taking into account changes in tire radius, which vary depending on the vehicle speed. Then, the vehicle position can be calculated based on the calculated accurate actual vehicle speed.

[0056] [Second embodiment] Next, a second embodiment will be described with reference to FIG. In the first embodiment described above, the scale factor estimation unit 130 estimates a scale factor for each wheel speed, but in the second embodiment, the scale factor estimation unit 130 estimates a scale factor for each speed range, which is different. The following description will focus on the differences from the first embodiment described above, and descriptions of overlapping parts will be simplified or omitted.

[0057] The scale factor estimation unit 130 estimates scale factors for multiple divided speed ranges. For example, although not shown, the speed ranges are divided into three: a low speed range of 0 m / s or more and less than 10 m / s, a medium speed range of 10 m / s or more and less than 20 m / s, and a high speed range of 20 m / s or more. The scale factor estimation unit 130 then estimates a scale factor for one speed in each speed range. Here, one speed includes the center point of each speed range. The scale factors for each speed range are connected by an approximate line, and a scale factor function is created based on the approximate line. This makes it possible to estimate scale factors from various wheel speeds. Note that the speed range is not limited to being divided into three, and may be two or more.

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

[0059] FIG. 5 is an explanatory diagram showing an example of the flow of operations performed by the CPU 101 of the vehicle speed estimation device 100 of the second embodiment.

[0060] First, in step S200, the first vehicle speed calculation unit 110 calculates the wheel speed of the vehicle from the tire pulse count and tire circumference received from the wheel speed sensor 50, and the second vehicle speed calculation unit 120 calculates the GNSS speed of the vehicle based on signals from positioning satellites received by the GNSS receiver 60. Then, the process proceeds to the next step S202.

[0061] In step S202, the second vehicle speed calculation unit 120 determines the validity of the GNSS speed. For example, the accuracy of the GNSS speed is determined from the DOP (Dilution Of Precision), residual error, etc. If it is determined that the GNSS speed is valid, the process proceeds to the next step S204. On the other hand, if it is not determined that the GNSS speed is valid, the process returns to the above-mentioned step S200 again.

[0062] In step S204, the first vehicle speed calculation unit 110 determines whether the wheel speed is valid. For example, it determines whether the acceleration is equal to or less than a threshold value or whether the wheel speed is equal to or greater than a threshold value. If the acceleration exceeds the threshold value or the wheel speed is less than the threshold value, it does not determine that the wheel speed is valid. If it determines that the wheel speed is valid, it proceeds to the next step S206. On the other hand, if it does not determine that the wheel speed is valid, it returns to step S200 described above again.

[0063] In step S206, the process branches to low speed range, medium speed range, or high speed range for each wheel speed calculated in step S200, and then proceeds to step S208, step S210, or step S212, respectively.

[0064] In steps S208, S210, and S212, the ratio between the wheel speed and the GNSS speed is estimated or updated, and then the process proceeds to the next step, S214.

[0065] In step S214, the scale factor function is estimated or updated, and the process proceeds to the next step S216.

[0066] In step S216, the scale factor is estimated from the wheel speed using a scale factor function, and the process then proceeds to the next step S218.

[0067] In step S218, the wheel speed is multiplied by the scale factor to estimate the actual vehicle speed, and this process is then repeated.

[0068] In this embodiment, by configuring in this way, it is possible to simplify the process of estimating the scale factor compared to when the scale factor is estimated for each wheel speed.

[0069] [Third embodiment] Next, a third embodiment will be described with reference to FIGS.

[0070] In the first embodiment described above, the scale factor estimation unit 130 does not take into account the acceleration (longitudinal acceleration) of the vehicle when estimating the scale factor, but the third embodiment differs in that the scale factor estimation unit 130 estimates the scale factor taking the acceleration into account. Note that the following description will focus on the parts that are different from the first embodiment described above, and descriptions of overlapping parts will be simplified or omitted.

[0071] Functionally, the vehicle speed estimation device 100 includes an acceleration calculation unit 150 as shown in FIG.

[0072] The acceleration calculation unit 150 calculates the acceleration (longitudinal acceleration) from the wheel speed. The acceleration is calculated using known techniques. For example, the acceleration is calculated by estimating the gradient of the speed change from the time difference of the wheel speed or time series data.

[0073] The scale factor estimation unit 130 estimates a scale factor according to the wheel speed from the ratio of the wheel speed to the GNSS speed and the relationship between the wheel speed and acceleration. Here, the wheel speed error is proportional to the acceleration and has a negative correlation. That is, the error increases as the acceleration increases. The error also changes in proportion to the wheel speed. Therefore, the scale factor estimation unit 130 estimates the wheel speed error using the following formula. Then, the scale factor is estimated using the wheel speed after correcting the error caused by acceleration.

[0074]

number

number

[0075] where V1 is the vehicle speed pulse velocity before correction, x is the vehicle acceleration, α is a coefficient, e is an estimated value of the wheel speed error, and α E is the estimated value of coefficient α. Estimated value α E is estimated by applying the least squares method to equation (1), for example. By using the least squares method, the estimated value α E The processing time required to obtain the error can be shortened. The corrected wheel speed is calculated by subtracting the estimated error value from the wheel speed.

[0076] Here, we will explain the cause of errors that depend on acceleration. It is known that the tire radius fluctuates due to changes in tire load and slip ratio when a vehicle accelerates or decelerates. Therefore, a difference between the wheel speed and the actual vehicle speed occurs depending on the acceleration. Furthermore, even if the tire radius does not fluctuate, if there is a time difference between the wheel speed and the actual vehicle speed (in error estimation, the reference GNSS speed is considered to be the actual vehicle speed), the timing of the speed change will be shifted, resulting in an apparent speed error proportional to the acceleration. Therefore, it is possible to improve the accuracy of calculating the actual vehicle speed by using a scale factor estimated by taking acceleration into account rather than using a scale factor estimated without taking acceleration into account.

[0077] Next, the operation of the vehicle speed estimation device 100 will be described.

[0078] FIG. 7 is an explanatory diagram showing an example of the flow of operations of the vehicle speed estimation device 100 according to the third embodiment.

[0079] First, in step S300, the first vehicle speed calculation unit 110 calculates the wheel speed of the vehicle from the tire pulse count and tire circumference received from the wheel speed sensor 50, and the second vehicle speed calculation unit 120 calculates the GNSS speed of the vehicle based on signals from positioning satellites received by the GNSS receiver 60. Then, the process proceeds to the next step S302.

[0080] In step S302, the acceleration calculation unit 150 calculates the acceleration from the wheel speed, and the process then proceeds to the next step S304.

[0081] In step S304, the second vehicle speed calculation unit 120 determines the validity of the GNSS speed. For example, the accuracy of the GNSS speed is determined from the DOP (Dilution Of Precision), residual error, etc. If it is determined that the GNSS speed is valid, the process proceeds to the next step S306. On the other hand, if it is not determined that the GNSS speed is valid, the process returns to the above-mentioned step S300 again.

[0082] In step S306, the first vehicle speed calculation unit 110 determines whether the wheel speed is valid. For example, it determines whether the acceleration is equal to or less than a threshold value or whether the wheel speed is equal to or greater than a threshold value. If the acceleration exceeds the threshold value or the wheel speed is less than the threshold value, it does not determine that the wheel speed is valid. If it determines that the wheel speed is valid, it proceeds to the next step S308. On the other hand, if it does not determine that the wheel speed is valid, it returns to step S300 described above again.

[0083] In step S308, the ratio between the wheel speed and the GNSS speed and the scale factor function described above are estimated or updated, and the process then proceeds to the next step, S310.

[0084] In step S310, the scale factor is estimated from the wheel speed using a scale factor function, and the process then proceeds to step S312.

[0085] In step S312, the wheel speed is multiplied by a scale factor to estimate the actual vehicle speed, and this process is then repeated.

[0086] In this embodiment, the above-described configuration enables the actual vehicle speed to be calculated with higher accuracy. That is, it is known that an error occurs in the wheel speed based on the number of pulses from the wheel speed sensor 50 when the vehicle accelerates or decelerates, but by correcting the error and estimating the scale factor, the actual vehicle speed can be calculated with higher accuracy than when the error is not corrected.

[0087] [Fourth embodiment] Next, a fourth embodiment will be described with reference to FIG. In the third embodiment described above, the acceleration is estimated by the acceleration calculation unit 150, but in the fourth embodiment, the acceleration is calculated using an acceleration sensor, which is different. The following description will focus on the differences from the first embodiment described above, and descriptions of overlapping parts will be simplified or omitted.

[0088] The vehicle speed estimation system 10 further includes an acceleration sensor 70 .

[0089] The acceleration sensor 70 is mounted on the vehicle and detects the acceleration (longitudinal acceleration) of the vehicle. The detected acceleration is then passed to the acceleration calculation unit 150.

[0090] The acceleration calculation unit 150 acquires the acceleration (longitudinal acceleration) detected by the acceleration sensor 70.

[0091] As in the third embodiment described above, the scale factor estimation unit 130 estimates a scale factor according to the wheel speed from the ratio between the wheel speed and the GNSS speed and the relationship between the wheel speed and the acceleration.

[0092] [Fifth embodiment] Next, a fifth embodiment will be described with reference to FIG. In the third and fourth embodiments described above, the scale factor is estimated taking acceleration into consideration, but in the fifth embodiment, when acceleration is equal to or less than a threshold value, the scale factor is estimated to estimate the actual vehicle speed in the same way as in the first embodiment, but when acceleration exceeds the threshold value, the actual vehicle speed is estimated from the speed change due to acceleration without using the scale factor, which is different. Note that the following description will focus on the parts that are different from the above-described embodiments, and descriptions of overlapping parts will be simplified or omitted.

[0093] Functionally, the vehicle speed estimation device 100 includes a speed change calculation unit 160 as shown in FIG.

[0094] The velocity change calculation unit 160 calculates the velocity change amount, which is the amount by which the velocity has changed, by integrating the acceleration.

[0095] When the acceleration calculated by the acceleration calculation unit 150 is equal to or less than a threshold value, the scale factor estimation unit 130 estimates a scale factor according to the wheel speed from the relationship between the ratio of the wheel speed to the GNSS speed and the wheel speed, as in the first embodiment described above. That is, when the acceleration is small, the scale factor is estimated while ignoring the acceleration, and when the acceleration is large, the scale factor is not estimated. Here, it is desirable that the acceleration threshold value be a value small enough to be considered as approximately constant speed driving.

[0096] When the acceleration is equal to or less than a threshold value, the vehicle speed estimation unit 140 estimates the actual vehicle speed based on a scale factor corresponding to the wheel speed estimated by the scale factor estimation unit 130. In other words, when the acceleration is negligibly small, the actual vehicle speed is estimated using the scale factor, as in the first embodiment.

[0097] Furthermore, when the acceleration exceeds a threshold value, the vehicle speed estimation unit 140 estimates the actual vehicle speed by adding the speed change amount based on the acceleration to the wheel speed. That is, the actual vehicle speed estimated based on the scale factor when the acceleration exceeds the threshold value is used as the initial value, and the vehicle speed is estimated by adding the speed change amount.

[0098] In this embodiment, by configuring in this way, it is possible to calculate the actual vehicle speed with higher accuracy even when the acceleration is large.

[0099] [Sixth embodiment] Next, a sixth embodiment will be described with reference to FIGS. In the sixth embodiment, when the acceleration is equal to or less than a threshold value, the actual vehicle speed is estimated by estimating a scale factor taking the speed into consideration, as in the first embodiment, but when the acceleration exceeds the threshold value, the magnitude of the time difference between the wheel speed and the GNSS speed is estimated and the time at which the wheel speed is referenced is corrected, which is different. Note that the following description will focus on the differences from the above-mentioned embodiments, and descriptions of overlapping parts will be simplified or omitted.

[0100] Functionally, the vehicle speed estimation device 100 includes a time lag calculation unit 170 as shown in FIG.

[0101] The time offset calculation unit 170 calculates the amount of time offset between the wheel speed and the GNSS speed from the difference between the wheel speed and the GNSS speed corrected by a scale factor according to the speed with respect to the acceleration.

[0102] The scale factor estimation unit 130 is the same as that in the fifth embodiment.

[0103] The vehicle speed estimation unit 140 estimates the actual vehicle speed based on the scale factor corresponding to the wheel speed estimated by the scale factor estimation unit 130. As shown in Fig. 11 , the actual vehicle speed is output as the vehicle speed at time t0 by shifting the time at which the wheel speed is referenced by an amount corresponding to the amount of time lag estimated by the time lag calculation unit 170.

[0104] Here, we will explain the causes of time deviation. Even if the wheel speed and the GNSS speed are exactly the same speed with no error, a time deviation may occur between them due to processing delays within the wheel speed sensor 50 or the GNSS receiver 60. Generally, the GNSS speed is originally assigned highly accurate time information that GNSS possesses. However, the wheel speed sensor 50 and the acceleration sensor 70 are not assigned time information, so time information is assigned taking into account sensor delays for processing, etc. As a result, there is a possibility that a time deviation, albeit slight, may occur between them and the GNSS speed.

[0105] Figure 11 shows the relationship between the speed error and acceleration when there is a time offset between the wheel speed corrected by a speed-dependent scale factor and the GNSS speed. Figure 11(A) shows the case when the wheel speed is lagging, and Figure 11(B) shows the case when the wheel speed is leading. As shown in Figure 11, if the magnitude of the time offset is ΔT and ΔT is small enough that acceleration x can be considered a constant value, the speed error is ΔT·x. ΔT's sign changes depending on whether the time offset is leading or lagging, and the slope of the speed error is proportional to ΔT (see the solid lines in the right panels of Figures 11(A) and 11(B)). Here, the solid lines in the right panels of Figures 11(A) and 11(B) represent the "speed error with respect to acceleration" when there is a time offset. The dashed lines represent the "speed error with respect to acceleration" when using the wheel speed before or after ΔT. If the acceleration changes so much during ΔT that it cannot be considered a constant value, the speed error corresponds to the integral of the acceleration over the time interval ΔT, rather than ΔT·x.

[0106] The magnitude of the time difference ΔT can be calculated using the following procedure. First, as in the fifth embodiment described above, the scale factor estimation unit 130 estimates a scale factor corresponding to the speed only when the acceleration is equal to or less than a threshold value. Next, the time lag calculation unit 170 observes whether the speed error or scale factor changes to a positive or negative value when the acceleration exceeds the threshold value, and calculates the slope relative to the acceleration by applying the least squares method. This slope is the magnitude of the time lag ΔT. Furthermore, whether the slope is positive or negative corresponds to an advance or delay of the time lag.

[0107] If the error depending on the acceleration is directly reflected in the change in the scale factor to estimate the velocity, the result will be the same as in the third and fourth embodiments. On the other hand, the sixth embodiment differs in that the magnitude of the time difference ΔT is calculated and the time difference is corrected, thereby reducing the error depending on the acceleration.

[0108] In Figure 11, the time of the currently referenced GNSS speed is indicated as t0, and the wheel speed time is shifted by ΔT. In Figure 11(A), the wheel speed is delayed, so to obtain the speed at the same time as the GNSS speed at time t0, the wheel speed ΔT later can be referenced as the wheel speed at time t0. In Figure 11(B), the wheel speed is advanced, so the wheel speed ΔT earlier can be referenced as the wheel speed at time t0. Furthermore, if the acceleration is integrated in the time interval in which the reference time is shifted and added to the original wheel speed, the same effect as that obtained by shifting the reference time can be obtained.

[0109] In this embodiment, by configuring in this way, it is possible to calculate the actual vehicle speed with higher accuracy regardless of the magnitude of the acceleration.

[0110] Regarding the correction of the time difference, the time at which the wheel speed is referenced may be directly shifted, or the same effect may be obtained by estimating the vehicle speed by adding the speed change amount obtained by integrating the acceleration over the time interval of the time difference.

[0111] The vehicle speed estimation device 100 and the position calculation device 200 according to the embodiment have been described above as examples. The embodiment may be in the form of a program that causes a computer to execute the functions of each unit included in the vehicle speed estimation device 100 and the position calculation device 200. The embodiment may be in the form of a computer-readable non-transitory storage medium that stores the program.

[0112] The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention.

[0113] The processing flow of the program described in the above embodiment is also an example. Therefore, in the above embodiment, unnecessary steps may be deleted, new steps may be added, or the processing order may be rearranged, without departing from the spirit of the invention.

[0114] In the above embodiment, the processing according to the embodiment is realized by a software configuration using a computer by executing a program, but the present invention is not limited to this. The embodiment may be realized by, for example, a hardware configuration or a combination of a hardware configuration and a software configuration. [Explanation of symbols]

[0115] 10 Vehicle speed estimation system 50 Wheel speed sensor 60 GNSS receivers 100 Vehicle speed estimation device 110 1st vehicle speed calculation section 120 2nd vehicle speed calculation section 130 Scale factor estimation unit 140 Vehicle speed estimation section 200 Position calculation device 70 Acceleration Sensor 150 Acceleration calculation unit 160 Speed ​​change calculation unit 170 Time offset calculation unit

Claims

1. 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 scale factor estimation unit that estimates a scale factor according 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; a vehicle speed estimation unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor; an acceleration calculation unit that calculates the acceleration of the vehicle using an acceleration sensor; a speed change calculation unit that calculates a speed change amount, which is an amount of change in speed, by integrating the acceleration; Equipped with the scale factor estimation unit, when the acceleration is equal to or less than a threshold value, estimates a scale factor according to the first vehicle speed from a relationship between a ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; the vehicle speed estimation unit estimates the actual vehicle speed based on a scale factor corresponding to the first vehicle speed when the acceleration is equal to or less than a threshold value, and estimates the actual vehicle speed by adding the speed change based on the acceleration to the first vehicle speed when the acceleration exceeds the threshold value.

2. The vehicle speed estimation device according to claim 1 , wherein the scale factor estimation unit divides the speed range of the vehicle into a plurality of speed ranges and estimates the scale factor for each of the speed ranges.

3. 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 scale factor estimation unit that estimates a scale factor according 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; a vehicle speed estimation unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor; an acceleration calculation unit that calculates the acceleration of the vehicle using an acceleration sensor; a time lag calculation unit that calculates a time lag between the first vehicle speed and the second vehicle speed from a difference between the first vehicle speed and the second vehicle speed corrected by a scale factor estimated by the scale factor estimating unit according to the first vehicle speed with respect to the acceleration, the scale factor estimation unit, when the acceleration is equal to or less than a threshold value, estimates a scale factor according to the first vehicle speed from a relationship between a ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; the vehicle speed estimation unit estimates the actual vehicle speed based on a scale factor corresponding to the first vehicle speed when the acceleration is equal to or less than a threshold value, and when the acceleration exceeds the threshold value, shifts the time at which the first vehicle speed is referenced by an amount corresponding to the time offset and outputs the actual vehicle speed.

4. The vehicle speed estimation device according to claim 3 , wherein the scale factor estimation unit divides the speed range of the vehicle into a plurality of speed ranges and estimates the scale factor for each of the speed ranges.

5. a vehicle speed estimation device that estimates an actual vehicle speed of a vehicle; and a position calculation device that calculates a position of the vehicle from the actual vehicle speed estimated by the vehicle speed estimation device, The vehicle speed estimation device 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 scale factor estimation unit that estimates a scale factor according 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; a vehicle speed estimation unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor; an acceleration calculation unit that calculates the acceleration of the vehicle using an acceleration sensor; a speed change calculation unit that calculates a speed change amount, which is an amount of change in speed, by integrating the acceleration, the scale factor estimation unit, when the acceleration is equal to or less than a threshold value, estimates a scale factor according to the first vehicle speed from a relationship between a ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; the vehicle speed estimating unit estimates the actual vehicle speed based on a scale factor corresponding to the first vehicle speed when the acceleration is equal to or less than a threshold value, and estimates the actual vehicle speed by adding the speed change based on the acceleration to the first vehicle speed when the acceleration exceeds the threshold value. Position calculation device.

6. Computer, 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 scale factor estimation unit that estimates a scale factor according 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; a vehicle speed estimation unit that estimates an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor; an acceleration calculation unit that calculates the acceleration of the vehicle using an acceleration sensor; a speed change calculation unit that calculates a speed change amount, which is an amount of change in speed, by integrating the acceleration; and make it work, the scale factor estimation unit, when the acceleration is equal to or less than a threshold value, estimates a scale factor according to the first vehicle speed from a relationship between a ratio of the first vehicle speed to the second vehicle speed and the first vehicle speed; The vehicle speed estimation unit estimates the actual vehicle speed based on a scale factor corresponding to the first vehicle speed when the acceleration is equal to or less than a threshold value, and estimates the actual vehicle speed by adding the speed change based on the acceleration to the first vehicle speed when the acceleration exceeds the threshold value.

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