Distance Estimation Device

Abstract

To provide a movement distance estimation device capable of estimating a movement distance of a vehicle with high accuracy regardless of a change in outer diameter of a tire.SOLUTION: A movement distance estimation device 10 includes: a rotation sensor 3 that detects a rotation number and a rotational speed of a tire 7; a GPS receiver 4 that acquires positional information of a vehicle 2; a reference distance calculation unit 12 that calculates a plurality of reference distances corresponding to the rotational speed of the tire 7 on the basis of the rotational speed of the tire 7 and the positional information of the vehicle 2; a prediction function generation unit 13 that generates a prediction function indicating a relation between the rotational speed of the tire 7 and the reference distance on the basis of the rotational speeds of the tire 7 and the reference distances at a plurality of points; a reference distance determination unit 14 that determines the reference distance according to the rotational speed of the tire 7; and a movement distance calculation unit 15 that calculates a movement distance of the vehicle 2 on the basis of the rotational number of the tire 7 and the determined reference distance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a moving distance estimation device.

Background Art

[0002] For example, Patent Document 1 stores a correction table describing the correction amount of the rotational speed for each direction displacement and rotational speed of a vehicle, calculates the rotational speed of a wheel and the rotational angle around the yaw axis of the vehicle body, extracts the correction amount specified by both the rotational speed and the rotational angle from the correction table, adds the correction amount to the rotational speed, and transmits the corrected rotational speed together with the rotational angle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When estimating the moving distance of a vehicle in autonomous navigation, for example, the moving distance is calculated based on the number of rotations of the tire and the reference distance of the vehicle (the traveling distance of the vehicle per one rotation of the tire). However, due to the outside air temperature, vehicle speed, physical individual differences of the tire (e.g., air pressure), etc., the outer diameter of the tire changes. When the outer diameter of the tire changes, the reference distance also fluctuates. Therefore, when a single correction table is used for the reference distance as in the above embodiment, the estimation accuracy of the moving distance is reduced due to the error of the reference distance. In the automatic driving of a vehicle, the reduction in the estimation accuracy of the moving distance leads to the reduction in the estimation accuracy of the vehicle's own position.

[0005] An object of the present invention is to provide a moving distance estimation device that can accurately estimate the moving distance of a vehicle regardless of the change in the outer diameter of the tire.

Means for Solving the Problems

[0006] One aspect of the present invention is a distance estimation device for estimating the distance traveled by a vehicle using a reference distance traveled per rotation of a tire, comprising: a rotation detection unit for detecting the number of rotations and rotational speed of a tire; a position information acquisition unit for acquiring vehicle position information; a reference distance calculation unit for calculating multiple reference distances corresponding to the tire rotational speed based on the tire rotational speed detected by the rotation detection unit and the vehicle position information detected by the position information acquisition unit; a prediction function generation unit for generating a prediction function representing the relationship between the tire rotational speed and the reference distance based on the tire rotational speed and reference distance at multiple points; a reference distance determination unit for determining a reference distance corresponding to the tire rotational speed detected by the rotation detection unit using the prediction function generated by the prediction function generation unit; and a distance estimation unit for calculating the distance traveled by a vehicle based on the number of rotations detected by the rotation detection unit and the reference distance determined by the reference distance determination unit.

[0007] In this type of distance estimation device, multiple reference distances corresponding to the tire rotation speed are calculated based on the tire rotation speed and the vehicle's position information. Based on the tire rotation speed and reference distances at these multiple points, a prediction function representing the relationship between the tire rotation speed and the reference distance is generated. Then, the reference distance corresponding to the tire rotation speed is determined using the prediction function. The vehicle's travel distance is then calculated based on the number of tire rotations and the determined reference distance. The reference distance changes depending on the tire's outer diameter. Even if such a change in tire outer diameter occurs, a prediction function representing the relationship between the tire rotation speed and the reference distance corresponding to the tire's outer diameter is generated again, and the reference distance corresponding to the tire rotation speed is determined using this new prediction function. As a result, the vehicle's travel distance is estimated with high accuracy regardless of changes in the tire's outer diameter. Furthermore, by determining the reference distance corresponding to the tire rotation speed using the prediction function, a correction table representing the relationship between the tire rotation speed and the reference distance becomes unnecessary, thus reducing the burden of creating the correction table.

[0008] The prediction function may be a function that approximates the solution curve of the logistic equation, which changes asymptotically with respect to the lower and upper limits of the reference distance. In such a configuration, an appropriate reference distance corresponding to the tire rotation speed can be obtained by generating a prediction function that approximates the solution curve of the logistic equation.

[0009] The distance estimation device further includes a temperature detection unit for detecting ambient temperature, and the reference distance calculation unit and the prediction function generation unit may be executed when the ambient temperature detected by the temperature detection unit has changed by a predetermined amount or more since the previous generation of the prediction function. In such a configuration, when the ambient temperature has changed by a predetermined amount or more since the previous generation of the prediction function, the calculation of the reference distance corresponding to the tire rotation speed and the generation of the prediction function are automatically executed.

[0010] The distance estimation device further includes an air pressure detection unit for detecting the air pressure of the tires. The reference distance calculation unit and the prediction function generation unit may be executed when the air pressure of the tires detected by the air pressure detection unit has changed by a predetermined amount or more since the previous generation of the prediction function. In this configuration, when the air pressure of the tires has changed by a predetermined amount or more since the previous generation of the prediction function, the calculation of the reference distance corresponding to the tire rotation speed and the generation of the prediction function are automatically executed. [Effects of the Invention]

[0011] According to the present invention, the distance traveled by a vehicle can be estimated with high accuracy regardless of changes in the outer diameter of the tire. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing the configuration of a self-position estimation device equipped with a distance estimation device according to one embodiment of the present invention. [Figure 2] This is a conceptual diagram illustrating how the outer diameter of a tire increases as the rotation speed increases. [Figure 3] This graph shows an example of the relationship between tire rotation speed and tire outer diameter. [Figure 4] This flowchart shows the steps of the function generation process executed by the arithmetic processing unit shown in Figure 1. [Figure 5] This graph shows how a fitting function, which represents the relationship between tire rotation speed and reference distance, is used to predict the reference distance from the tire rotation speed. [Figure 6] This flowchart shows the steps of the distance calculation process performed by the arithmetic processing unit shown in Figure 1. [Figure 7] This table shows an example of a correction table illustrating the relationship between vehicle speed and reference distance. [Figure 8] This is a conceptual diagram illustrating how the vehicle's travel distance is calculated from a reference distance. [Figure 9] This graph shows how the logistic curve of the fitting function changes depending on the ambient temperature. [Figure 10] This is a block diagram showing the configuration of a self-position estimation device equipped with a distance travel estimation device according to another embodiment of the present invention. [Figure 11] Figure 10 is a flowchart showing the steps of the function generation process executed by the arithmetic processing unit. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] Figure 1 is a block diagram showing the configuration of a self-position estimation device equipped with a distance estimation device according to one embodiment of the present invention. In Figure 1, the self-position estimation device 1 is mounted on a vehicle 2. The vehicle 2 is an automobile or an industrial vehicle such as a forklift. The self-position estimation device 1 is a device that estimates the self-position of the vehicle 2 when the vehicle 2 is operating autonomously.

[0015] The self-position estimation device 1 includes a rotation sensor 3, a GPS receiver 4, an input device 5, and an arithmetic processing unit 6.

[0016] The rotation sensor 3 is a rotation detection unit that detects the rotation speed and rotation rate of the tire 7 (see FIG. 2) of the vehicle 2. As the rotation sensor 3, for example, a rotary encoder or the like is used. The rotation sensor 3 outputs the detected value as an electrical signal value such as a current value.

[0017] The GPS receiver 4 receives radio wave signals from a plurality of GPS satellites and measures the current position of the vehicle 2 as position information. The GPS receiver 4 is a position information acquisition unit that acquires the position information of the vehicle 2.

[0018] The input device 5 is a device that inputs data related to the self-position estimation of the vehicle 2. As the input device 5, a car navigation or a dedicated touch panel or the like is used.

[0019] The arithmetic processing unit 6 is composed of a CPU, a RAM, a ROM, an input / output interface, and the like. The arithmetic processing unit 6 executes predetermined processing based on the rotation speed and rotation rate of the tire 7 detected by the rotation sensor 3 and the position information of the vehicle 2 measured by the GPS receiver 4, and estimates the self-position of the vehicle 2 by odometry.

[0020] Here, the distance that the vehicle 2 travels when the tire 7 makes one rotation is defined as the reference distance. The reference distance depends on the outer diameter of the tire 7. When the air pressure of the tire 7 changes, the outer diameter of the tire 7 physically changes. Also, even when the traveling speed of the vehicle 2 and the temperature of the tire 7 change, the outer diameter of the tire 7 physically changes.

[0021] For example, as shown in FIG. 2, when the traveling speed of the vehicle 2 is high (see FIG. 2(b)), compared with the case where the traveling speed of the vehicle 2 is low (see FIG. 2(a)), since the tire 7 rotates at a high speed, the tire 7 is likely to expand due to centrifugal force, and the outer diameter r of the tire 7 becomes large.

[0022] As shown in Figure 3, the outer diameter r of the tire 7 has a physical upper limit Lu and a lower limit Ll. The upper limit Lu of the outer diameter r of the tire 7 is the limit beyond which the tire 7 cannot expand. As the vehicle 2's speed increases, the outer diameter r of the tire 7 approaches the upper limit Lu. The lower limit Ll of the outer diameter r of the tire 7 is the limit beyond which the tire 7 cannot contract. When the vehicle 2 stops moving, the outer diameter r of the tire 7 is at the lower limit Ll.

[0023] As shown in Figure 3, the change in the outer diameter of tire 7 can be approximated and predicted using a solution curve P of the logistic equation, such as a sigmoid curve, with respect to the rotational speed of tire 7. In other words, the change in the outer diameter of tire 7 with respect to the rotational speed of tire 7 will asymptotically approach the upper limit Lu and lower limit Ll of the outer diameter of tire 7. Note that the rotational speed of tire 7 is the number of rotations of tire 7 per unit time and is proportional to the travel speed of vehicle 2.

[0024] Therefore, the arithmetic processing unit 6 determines the reference distance of vehicle 2 by predicting the outer diameter r of tire 7 during vehicle 2's movement based on the solution curve of the logistic equation, taking into account the vehicle 2's driving speed, ambient temperature, and the tire pressure of tire 7. Then, the arithmetic processing unit 6 uses this reference distance to calculate the distance traveled by vehicle 2 and estimates the vehicle 2's own position.

[0025] The arithmetic processing unit 6 includes a driving information acquisition unit 11, a reference distance calculation unit 12, a prediction function generation unit 13, a reference distance determination unit 14, a travel distance calculation unit 15, and a self-position estimation unit 16.

[0026] The driving information acquisition unit 11 acquires the rotational speed of the tires 7 detected by the rotation sensor 3 and the position information of the vehicle 2 measured by the GPS receiver 4, in response to the instruction input from the input device 5. The rotational speed of the tires 7 and the position information of the vehicle 2 constitute the driving information of the vehicle 2.

[0027] The reference distance calculation unit 12 calculates multiple reference distances corresponding to the rotation speed of the tire 7 based on the rotation speed of the tire 7 and the position information of the vehicle 2 obtained by the driving information acquisition unit 11.

[0028] The prediction function generation unit 13 calculates a prediction function that represents the relationship between the rotation speed of the tire 7 and the reference distance, based on the rotation speed of the tire 7 at multiple points and the reference distance. The reference distance corresponds to the outer diameter of the tire 7.

[0029] The reference distance determination unit 14 uses the prediction function generated by the prediction function generation unit 13 to determine a reference distance corresponding to the rotation speed of the tire 7.

[0030] The distance calculation unit 15 calculates the distance traveled by the vehicle 2 based on the number of rotations of the tire 7 detected by the rotation sensor 3 and the reference distance determined by the reference distance determination unit 14.

[0031] The self-position estimation unit 16 estimates the self-position of the vehicle 2 based on the distance traveled by the vehicle 2 calculated by the distance traveled calculation unit 15.

[0032] The rotation sensor 3, GPS receiver 4, input device 5, and the driving information acquisition unit 11, reference distance calculation unit 12, prediction function generation unit 13, reference distance determination unit 14, and travel distance calculation unit 15 of the arithmetic processing unit 6 constitute the travel distance estimation device 10 of this embodiment. The travel distance estimation device 10 estimates the travel distance of the vehicle 2 using the reference distance that the vehicle 2 travels per rotation of the tires 7.

[0033] Figure 4 is a flowchart showing the procedure for the function generation process performed by the arithmetic processing unit 6. The function generation process is performed by the driving information acquisition unit 11, the reference distance calculation unit 12, and the prediction function generation unit 13.

[0034] In Figure 4, the arithmetic processing unit 6 first determines whether a function generation instruction has been input via the input device 5 (procedure S101). If the arithmetic processing unit 6 determines that a function generation instruction has been input, it acquires the rotational speed of the tire 7 detected by the rotation sensor 3 and the position information of the vehicle 2 measured by the GPS receiver 4 (procedure S102).

[0035] Then, as shown in Figure 5, the arithmetic processing unit 6 calculates a reference distance corresponding to the rotation speed of the tire 7 based on the rotation speed of the tire 7 and the position information of the vehicle 2 (procedure S103). The reference distance is calculated from the history of the position information of the vehicle 2.

[0036] Next, the calculation unit 6 determines whether a specified number of reference distances corresponding to the rotational speed of the tire 7 have been calculated (procedure S104). The specified number of points is, for example, 3 points (see Figure 5). If the calculation unit 6 determines that a specified number of reference distances corresponding to the rotational speed of the tire 7 have not been calculated, it repeats the above procedures S102 and S103.

[0037] When the arithmetic processing unit 6 determines that a specified number of reference distances corresponding to the rotational speed of the tire 7 have been calculated, it uses the least squares method to fit the rotational speed of the tire 7 and the reference distance at the specified number of points to a logistic curve Q (solution curve) such as a sigmoid curve, as shown in Figure 5, and generates a fitting function (prediction function) (procedure S105). The logistic curve Q is set to pass through all of the specified points.

[0038] The fitting function is expressed by the following formula.

number

[0039] In the example shown in Figure 5, the reference distance when tire 7 rotates 10 times per unit time is 1.30 m, the reference distance when tire 7 rotates 60 times per unit time is 1.35 m, and the reference distance when tire 7 rotates 80 times per unit time is 1.36 m.

[0040] Here, the driving information acquisition unit 11 executes procedures S101 and S102. The reference distance calculation unit 12 executes procedure S103. The prediction function generation unit 13 executes procedures S104 and S105.

[0041] Figure 6 is a flowchart showing the procedure for the distance calculation process performed by the arithmetic processing unit 6. The distance calculation process is performed by the reference distance determination unit 14 and the travel distance calculation unit 15.

[0042] In Figure 6, the arithmetic processing unit 6 first obtains the rotation speed and rotational velocity of the tire 7 detected by the rotation sensor 3 (procedure S111). Next, the arithmetic processing unit 6 uses the fitting function shown in Figure 5 to determine a predicted value of the reference distance corresponding to the rotational velocity V of the tire 7 (procedure S112).

[0043] Next, the arithmetic processing unit 6 calculates the distance traveled by the vehicle 2 based on the rotation speed of the tires 7 and the predicted value of the reference distance (procedure S113). The distance traveled by the vehicle 2 is calculated by multiplying the predicted value of the reference distance by the rotation speed of the tires 7.

[0044] Here, the reference distance determination unit 14 executes procedures S111 and S112. The travel distance calculation unit 15 executes procedures S111 and S113.

[0045] Incidentally, conventionally, a correction table, as shown in Figure 7, was used to determine the reference distance according to the vehicle 2's speed. The correction table represents the relationship between the vehicle 2's speed and the reference distance and is prepared in advance. The vehicle 2's speed corresponds to the rotation speed of the tires 7.

[0046] However, if the outer diameter of tire 7 changes due to conditions such as the temperature of tire 7, the reference distance will change. For example, as shown in Figure 8, if the reference distance is 100 cm, then when tire 7 rotates 5 times, the distance traveled is 500 cm. If the outer diameter of tire 7 increases due to a rise in temperature, and the reference distance becomes 103 cm, then when tire 7 rotates 5 times, the distance traveled will be 515 cm. In other words, even just 5 rotations of tire 7 cause the distance traveled by vehicle 2 to shift by 15 cm, resulting in a 15 cm error in the vehicle 2's self-position estimation. Such a self-position estimation error is fatal for autonomous driving.

[0047] To suppress self-position estimation errors, one could consider using a correction table that shows the relationship between the vehicle's speed and the reference distance for each tire temperature of the tire 7. However, in that case, a correction table would be required for each tire temperature of the tire 7, which would increase the burden of creating the correction tables.

[0048] To address such challenges, in this embodiment, when reference distances corresponding to the rotational speed of the tire 7 are calculated at multiple points, a fitting function (prediction function) is generated based on the rotational speed of the tire 7 and the reference distance at those multiple points. At this time, even if the outer diameter of the tire 7 changes due to a change in the temperature of the tire 7, a fitting function suitable for the temperature of the tire 7 is generated. For example, as shown in Figure 9, when the temperature of the tire 7 is high (see Figure 9(b)), a fitting function is generated in which the upper limit Lu and lower limit Ll of the logistic curve Q are higher compared to when the temperature of the tire 7 is low (see Figure 9(a)). Therefore, the optimal reference distance can be obtained regardless of the temperature change of the tire 7.

[0049] As described above, according to this embodiment, based on the rotational speed of the tire 7 and the position information of the vehicle 2, reference distances corresponding to the rotational speed of the tire 7 are calculated at multiple points, and a prediction function representing the relationship between the rotational speed of the tire 7 and the reference distance is generated based on the rotational speed of the tire 7 and the reference distance at multiple points. Then, the reference distance corresponding to the rotational speed of the tire 7 is determined using the prediction function. Then, the travel distance of the vehicle 2 is calculated based on the rotational speed of the tire 7 and the said reference distance. The reference distance changes according to the outer diameter of the tire 7. Even if such a change in the outer diameter of the tire 7 occurs, a prediction function representing the relationship between the rotational speed of the tire 7 and the reference distance corresponding to the outer diameter of the tire 7 is generated again, and the reference distance corresponding to the rotational speed of the tire 7 is determined using this new prediction function. As a result, the travel distance of the vehicle 2 can be estimated with high accuracy regardless of the change in the outer diameter of the tire 7. As a result, the accuracy of estimating the self-position of the vehicle 2 can be improved. Furthermore, by determining the reference distance corresponding to the rotational speed of the tire 7 using the prediction function, a correction table representing the relationship between the rotational speed of the tire 7 and the reference distance becomes unnecessary, thus reducing the burden of creating the correction table.

[0050] Furthermore, in this embodiment, an appropriate reference distance corresponding to the rotational speed of the tire 7 can be obtained by generating a prediction function that is approximated by the solution curve of the logistic equation, which changes asymptotically with respect to the lower and upper limits of the reference distance.

[0051] Figure 10 is a block diagram showing the configuration of a self-position estimation device equipped with a distance estimation device according to another embodiment of the present invention. In Figure 10, the self-position estimation device 1A includes the rotation sensor 3, the GPS receiver 4, the temperature sensor 21, the air pressure sensor 22, and the arithmetic processing unit 6A.

[0052] The temperature sensor 21 is a temperature detection unit that detects the ambient temperature. When the ambient temperature rises, the temperature of the tire 7 rises. The air pressure sensor 22 is an air pressure detection unit that detects the air pressure of the tire 7.

[0053] The arithmetic processing unit 6A has a driving information acquisition unit 11A instead of the driving information acquisition unit 11 in the embodiment described above.

[0054] The driving information acquisition unit 11A acquires the rotation speed of the tire 7 detected by the rotation sensor 3 and the position information of the vehicle 2 measured by the GPS receiver 4, in accordance with the ambient temperature detected by the temperature sensor 21 and the air pressure of the tire 7 detected by the air pressure sensor 22.

[0055] The rotation sensor 3, GPS receiver 4, temperature sensor 21, air pressure sensor 22, and the driving information acquisition unit 11A, reference distance calculation unit 12, prediction function generation unit 13, reference distance determination unit 14, and travel distance calculation unit 15 of the calculation processing unit 6A constitute the travel distance estimation device 10A of this embodiment.

[0056] Figure 11 is a flowchart showing the procedure for the function generation process executed by the arithmetic processing unit 6A, and corresponds to Figure 4. The initial generation of the fitting function is performed, for example, when a function generation instruction is input via the input device 5 mentioned above.

[0057] In Figure 11, the arithmetic processing unit 6A first determines, based on the value detected by the temperature sensor 21, whether the change in ambient temperature since the previous generation of the fitting function is less than the specified temperature (procedure S107). The specified temperature is predetermined.

[0058] When the calculation processing unit 6A determines that the change in ambient temperature since the previous generation of the fitting function is less than the specified temperature, it determines, based on the value detected by the air pressure sensor 22, whether the change in tire pressure 7 since the previous generation of the fitting function is less than the specified pressure (procedure S108). The specified pressure is predetermined.

[0059] If the arithmetic processing unit 6A determines that the change in tire pressure 7 since the last generation of the fitting function is less than the specified pressure, it repeats the above procedure S107.

[0060] If the arithmetic processing unit 6A determines in step S107 that the change in ambient temperature since the previous generation of the fitting function is greater than or equal to a specified temperature amount, or if it determines in step S108 that the change in tire pressure since the previous generation of the fitting function is greater than or equal to a specified pressure amount, it executes steps S102 to S105 in the same manner as in the embodiment described above.

[0061] Here, the driving information acquisition unit 11A executes procedures S107, S108, and S102. For this reason, the reference distance calculation unit 12 and the prediction function generation unit 13 are executed when the ambient temperature detected by the temperature sensor 21 has changed by a predetermined temperature amount or more since the previous fitting function was generated, and when the air pressure of the tire 7 detected by the air pressure sensor 22 has changed by a predetermined pressure amount or more since the previous fitting function was generated.

[0062] In this embodiment, when the ambient temperature changes by more than a specified temperature amount compared to the time the prediction function was generated previously, the calculation of the reference distance corresponding to the rotation speed of the tire 7 and the generation of the prediction function are automatically executed.

[0063] Furthermore, in this embodiment, even when the air pressure of the tire 7 changes by more than a specified pressure amount compared to when the prediction function was generated previously, the calculation of the reference distance corresponding to the rotational speed of the tire 7 and the generation of the prediction function are automatically executed.

[0064] The present invention is not limited to the embodiments described above. For example, in the above embodiment, the rotation sensor 3 that detects the rotation speed and rotational speed of the tire 7 outputs the detected value as an electrical signal. However, the rotation sensor 3 is not particularly limited in form, and a rotary encoder or the like that outputs the detected value as a pulse signal may be used. In this case, the reference distance is the distance traveled per pulse of the rotation sensor 3.

[0065] Furthermore, in the above embodiment, the rotation speed and rotational velocity of the tire 7 are detected by the rotation sensor 3, but the configuration is not limited to this. The rotation sensor 3 may only detect the rotation speed of the tire 7, and the rotational velocity of the tire 7 may be calculated by the arithmetic processing units 6 and 6A. In this case, the rotation sensor 3 and some functions of the arithmetic processing units 6 and 6A constitute the rotation detection unit.

[0066] Furthermore, in the above embodiment, the location information of the vehicle 2 is acquired by a satellite positioning system (GNSS) using a GPS receiver 4. However, the method for acquiring the location information of the vehicle 2 is not limited to this form, and for example, a SLAM (simultaneous localization and mapping) method using LIDAR (light detection and ranging) may be employed.

[0067] Furthermore, in the above embodiment, the self-position of the vehicle 2 is estimated by odometry, but the present invention can also be applied when the self-position of the vehicle 2 is primarily estimated by GNSS or SLAM, and the self-position of the vehicle 2 is performed supplementarily by odometry.

[0068] Furthermore, in the above embodiment, the distance traveled by vehicle 2 is calculated and its own position is estimated when vehicle 2 is being driven automatically. However, the present invention can also be applied, for example, when calculating the distance traveled by vehicle 2 when vehicle 2 is being driven manually. [Explanation of symbols]

[0069] 2...Vehicle, 3...Rotation sensor (rotation detection unit), 4...GPS receiver (position information acquisition unit), 7...Tire, 10,10A...Travel distance estimation device, 11,11A...Driving information acquisition unit, 12...Reference distance calculation unit, 13...Prediction function generation unit, 14...Reference distance determination unit, 15...Travel distance calculation unit, 21...Temperature sensor (temperature detection unit), 22...Air pressure sensor (air pressure detection unit), Q...Logistic curve (solution curve).

Claims

1. A distance estimation device that estimates the distance traveled by a vehicle using a reference distance traveled per rotation of the vehicle's tires, A rotation detection unit for detecting the rotation speed and rotational speed of the aforementioned tire, A location information acquisition unit that acquires location information of the aforementioned vehicle, A reference distance calculation unit calculates multiple reference distances corresponding to the tire rotation speed based on the tire rotation speed detected by the rotation detection unit and the vehicle position information detected by the position information acquisition unit, A prediction function generation unit generates a prediction function that represents the relationship between the rotation speed of the tire and the reference distance based on the rotation speed of the tire and the reference distance at the aforementioned multiple points, A reference distance determination unit determines a reference distance corresponding to the tire rotation speed detected by the rotation detection unit, using the prediction function generated by the prediction function generation unit. A travel distance estimation device comprising: a travel distance calculation unit that calculates the travel distance of the vehicle based on the number of tire rotations detected by the rotation detection unit and the reference distance determined by the reference distance determination unit.

2. The travel distance estimation device according to claim 1, wherein the prediction function is a function that can be approximated by a solution curve of a logistic equation that changes asymptotically with respect to the lower and upper limits of the reference distance.

3. It further includes a temperature detection unit that detects the outside air temperature, The travel distance estimation device according to claim 1 or 2, wherein the reference distance calculation unit and the prediction function generation unit are executed when the ambient temperature detected by the temperature detection unit has changed by a predetermined amount or more compared to the time of the previous generation of the prediction function.

4. The system further includes an air pressure detection unit for detecting the air pressure of the aforementioned tire, The travel distance estimation device according to claim 1 or 2, wherein the reference distance calculation unit and the prediction function generation unit are executed when the tire pressure detected by the air pressure detection unit has changed by a predetermined amount or more compared to the time of the previous generation of the prediction function.

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