Road surface gradient calculation device, road surface gradient calculation method, and road surface gradient calculation program

Abstract

This invention provides a road surface gradient calculation device, a road surface gradient calculation method, and a road surface gradient calculation program that can improve the accuracy of gradient calculation. [Solution] The road surface gradient calculation device 1 includes a pressure sensor 10, an acceleration sensor 20, a first gradient calculation unit 41 that calculates a first gradient value indicating the road surface gradient based on the pressure detected by the pressure sensor 10, a second gradient calculation unit 42 that calculates a second gradient value indicating the road surface gradient based on the acceleration detected by the acceleration sensor 20, a difference determination unit 43 that determines whether the difference between the first gradient value calculated by the first gradient calculation unit 41 and the second gradient value calculated by the second gradient calculation unit 42 is greater than or equal to a predetermined value, and a gradient determination unit 44 that determines the first gradient value as the road surface gradient if the difference determined by the difference determination unit 43 is less than a predetermined value, and determines the second gradient value as the road surface gradient if the difference determined by the difference determination unit 43 is greater than or equal to a predetermined value.

Description

Technical Field

[0001] The present invention relates to a road surface gradient calculation device, a road surface gradient calculation method, and a road surface gradient calculation program.

Background Art

[0002] Conventionally, a slope detection device has been proposed that mounts both an acceleration sensor and an air pressure sensor and determines the gradient using both sensors (see, for example, Patent Document 1). This slope detection device determines that it is going uphill or downhill when both the acceleration and the altitude value satisfy the conditions. For example, even in a situation where the slope detection device can determine that it is going uphill based on the acceleration, if it cannot determine that it is going uphill based on the altitude value, it does not determine that it is going uphill, aiming to improve the accuracy.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There are an acceleration sensor method and an air pressure sensor method for the gradient calculation method. Here, the inventors of the present case have intensively studied each method and found that the air pressure sensor method is basically more accurate in gradient calculation than the acceleration sensor method. This is because the acceleration sensor method is easily affected by vehicle vibrations due to road surface irregularities and inclination of the vehicle due to loading, etc., and the gradient calculation becomes inaccurate.

[0005] On the other hand, the inventors of the present case have also found that although the air pressure sensor method is basically more accurate than the acceleration sensor method, the error becomes larger than that of the acceleration sensor method in specific situations such as opening and closing of windows and entrances and exits of tunnels.

[0006] The present invention was made to solve these problems, and its objective is to provide a road surface gradient calculation device, a road surface gradient calculation method, and a road surface gradient calculation program that can improve the accuracy of gradient calculation. [Means for solving the problem]

[0007] The road surface gradient calculation device according to the present invention is a road surface gradient calculation device for calculating the gradient of a road surface on which a vehicle travels, and comprises: a pressure sensor for detecting atmospheric pressure; an acceleration sensor for detecting acceleration in the direction of travel of the vehicle; a first gradient calculation means for calculating a first gradient value indicating the gradient of the road surface based on the atmospheric pressure detected by the pressure sensor; a second gradient calculation means for calculating a second gradient value indicating the gradient of the road surface based on the acceleration detected by the acceleration sensor; a difference determination means for determining whether the difference between the first gradient value calculated by the first gradient calculation means and the second gradient value calculated by the second gradient calculation means is greater than or equal to a predetermined value; and a gradient determination means for determining the first gradient value as the gradient of the road surface if the difference determined by the difference determination means is less than the predetermined value, and determining the second gradient value as the gradient of the road surface if the difference determined by the difference determination means is greater than or equal to the predetermined value.

[0008] The road surface gradient calculation method for a road surface gradient calculation device according to the present invention comprises a pressure sensor for detecting atmospheric pressure and an acceleration sensor for detecting acceleration in the direction of travel of a vehicle, and is a road surface gradient calculation method for a road surface gradient on which a vehicle travels, comprising: a first gradient calculation step of calculating a first gradient value indicating the gradient of the road surface based on the atmospheric pressure detected by the pressure sensor; a second gradient calculation step of calculating a second gradient value indicating the gradient of the road surface based on the acceleration detected by the acceleration sensor; a difference determination step of determining whether the difference between the first gradient value calculated in the first gradient calculation step and the second gradient value calculated by the second gradient calculation means is greater than or equal to a predetermined value; and a gradient determination step of determining the first gradient value as the gradient of the road surface if the difference determined in the difference determination step is less than the predetermined value, and determining the second gradient value as the gradient of the road surface if the difference determined in the difference determination step is greater than or equal to the predetermined value.

[0009] The road surface gradient calculation program according to the present invention is a road surface gradient calculation program that causes a computer to function as the road surface gradient calculation device described above. [Effects of the Invention]

[0010] According to the present invention, the accuracy of gradient calculation can be improved. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic block diagram of the road surface gradient calculation device according to this embodiment. [Figure 2] This graph shows the time evolution of the first and second gradient values. [Figure 3] This flowchart shows the road surface gradient calculation method of the road surface gradient calculation device according to this embodiment. [Figure 4] This is a conceptual diagram showing an example of a road surface gradient calculation method for the road surface gradient calculation device according to this embodiment, where (a) shows the vehicle driving state and (b) shows various values ​​at each driving point. [Modes for carrying out the invention]

[0012] The present invention will be described below in accordance with preferred embodiments. It should be noted that the present invention is not limited to the embodiments shown below, and can be modified as appropriate without departing from the spirit of the invention. Furthermore, in the embodiments shown below, some illustrations and descriptions of certain components are omitted. It goes without saying that, regarding the details of the omitted technologies, publicly known or well-known technologies are applied as appropriate, to the extent that they do not contradict the content described below.

[0013] Figure 1 is a schematic block diagram of the road surface gradient calculation device according to this embodiment. The road surface gradient calculation device 1 shown in Figure 1 is installed as a function of a device (e.g., a drive recorder) that evaluates the driver's driving behavior while the vehicle is in motion. The evaluation process of the driving behavior should change depending on whether the vehicle is traveling on an incline or not. For example, when the vehicle is traveling downhill, even if the engine is running at an over-revving speed, the vehicle is using engine braking, so the evaluation device suppresses the creation of events and the generation of warnings related to over-revving speed. In this way, the road surface gradient calculation device 1 according to this embodiment is installed in a device that performs driving evaluation, for example, and contributes to improving the accuracy of the driving evaluation. Note that the road surface gradient calculation device 1 does not have to be a function of a device that performs driving evaluation.

[0014] Such a road surface gradient calculation device 1 includes a pressure sensor 10, an acceleration sensor 20, a vehicle speed sensor 30, and a control unit 40.

[0015] The pressure sensor 10 detects the atmospheric pressure P around a moving vehicle. The pressure sensor 10 transmits the detected atmospheric pressure P information to the control unit 40. The control unit 40 sequentially stores the atmospheric pressure P information received from the pressure sensor 10 in the work area. The pressure sensor 10 detects atmospheric pressure P at predetermined time intervals.

[0016] The acceleration sensor 20 detects the acceleration G applied in the traveling direction of the vehicle. The acceleration sensor 20 transmits the information on the detected acceleration G to the control unit 40. The control unit 40 sequentially stores the information on the acceleration G received from the acceleration sensor 20 in the work area. The acceleration sensor 20 also detects the acceleration G at a predetermined time interval, similar to the pressure sensor 10.

[0017] The vehicle speed sensor 30 is for detecting the vehicle speed of the vehicle. The vehicle speed sensor 30 outputs, for example, a vehicle speed pulse corresponding to the rotation speed of the wheels. The arithmetic unit (not shown) can calculate the vehicle speed by measuring the number of vehicle speed pulses per unit time. The arithmetic unit may be provided as one function of the vehicle speed sensor 30, or may be provided outside the vehicle speed sensor 30. Therefore, the vehicle speed sensor 30 transmits the vehicle speed pulse or the information on the calculated vehicle speed to the control unit 40 as a speed signal.

[0018] The control unit 40 calculates the gradient of the road surface on which the vehicle travels. This control unit 40 is constituted by, for example, a CPU (Central Processing Unit), and stores a road surface gradient calculation program for functioning as the road surface gradient calculation device 1.

[0019] When the road surface gradient calculation program is executed, the control unit 40 causes the first gradient calculation unit (first gradient calculation means) 41, the second gradient calculation unit (second gradient calculation means) 42, the difference determination unit (difference determination means) 43, and the gradient determination unit (gradient determination means) 44 to function.

[0020] The first gradient calculation unit 41 calculates a first gradient value indicating the gradient of the road surface based on the atmospheric pressure P detected by the pressure sensor 10. When calculating the first gradient value, the first gradient calculation unit 41 first calculates the altitude value H from the atmospheric pressure P. The altitude value H is obtained by the formula shown below. The atmospheric pressure P used when calculating the altitude value H is preferably a representative value such as an average value of several times, a median value, or an average value excluding abnormal values. Altitude value H = [{(1013.25 / Atmospheric pressure P) 1 / 5.257-1}×(T + 273.15)] / 0.0065 In the above formula, T is the air temperature (degrees Celsius). Therefore, it is preferable that the road surface gradient calculation device 1 includes means for acquiring temperature information such as a temperature sensor.

[0021] Furthermore, the first gradient calculation unit 41 obtains the altitude value H for each unit distance. The first gradient calculation unit 41 calculates the first gradient value based on the difference in the altitude value H before and after traveling a unit distance and the unit distance. For example, if the unit distance is 50 m and the difference in the altitude value H is 1.5 m, the first gradient calculation unit 41 will calculate the first gradient value as 3%.

[0022] The second gradient calculation unit 42 calculates a second gradient value indicating the road surface gradient based on the acceleration G detected by the acceleration sensor 20. Here, the acceleration sensor 20 detects the acceleration G in the traveling direction. For this reason, when the road surface gradient is 0%, the acceleration G detected by the acceleration sensor 20 should match the calculated acceleration G' obtained from the change in the vehicle speed detected by the vehicle speed sensor 30. However, if the acceleration G detected by the acceleration sensor 20 does not match the calculated acceleration G', it can be said that it is affected by the road surface gradient. The second gradient calculation unit 42 calculates the second gradient value from the component affected by such a road surface gradient.

[0023] The difference determination unit 43 determines whether the difference between the first gradient value calculated by the first gradient calculation unit 41 and the second gradient value calculated by the second gradient calculation unit 42 is greater than or equal to a predetermined value.

[0024] The gradient determination unit 44 determines either the first gradient value calculated by the first gradient calculation unit 41 or the second gradient value calculated by the second gradient calculation unit 42 as the road surface gradient. The gradient determination unit 44 makes the determination based on the determination result of the difference determination unit 43.

[0025] If the difference determination unit 43 determines that the difference is less than a predetermined value, the gradient determination unit 44 determines the first gradient value as the road surface gradient. On the other hand, if the difference determination unit 43 determines that the difference is greater than or equal to a predetermined value, the gradient determination unit 44 determines the second gradient value as the road surface gradient.

[0026] Here, if the difference between the two is small, it can be said that both the first gradient value and the second gradient value are calculated with a certain degree of accuracy. For this reason, when the difference is small, the road surface gradient calculation device 1 improves accuracy by adopting the first gradient value based on the more accurate pressure sensor 10. On the other hand, when the difference between the two is large, it can be assumed that the detection by the pressure sensor 10 is inaccurate. For this reason, the road surface gradient calculation device 1 can improve accuracy by adopting the second gradient value based on the acceleration sensor 20.

[0027] To explain in more detail, the inventors of this case have found the following: The second gradient value based on the acceleration sensor 20 is prone to instability due to the influence of road surface irregularities. However, when comparing the case where the gradient calculation based on the acceleration sensor 20 becomes unstable with the case where the gradient calculation based on the pressure sensor 10 becomes unstable, such as when opening and closing windows or entering and exiting tunnels, the former is more accurate. Therefore, when the difference becomes large, it basically means that the pressure sensor 10 is unstable, and in such cases, accuracy can be improved by adopting the second gradient value based on the acceleration sensor 20.

[0028] Furthermore, even if the difference determined by the difference determination unit 43 is less than a predetermined value, if the amount of change in the first gradient value is greater than a specified value, it is preferable for the gradient determination unit 44 to determine the second gradient value as the road surface gradient instead of the first gradient value. This is because, in situations where the gradient calculation based on the pressure sensor 10 becomes unstable, the second gradient value based on the acceleration sensor 20 can be adopted if the difference happens to become small instantaneously. Note that the past first gradient value used to determine the amount of change can be any value that suits the vehicle environment, etc.

[0029] Next, with reference to Figure 2, an overview of the road surface gradient calculation method of the road surface gradient calculation device 1 according to this embodiment will be described. Figure 2 is a graph showing the time change of the first gradient value and the second gradient value. In Figure 2, the vertical axis represents the gradient value (%), the horizontal axis represents time, and the predetermined value is 5%. The first gradient value is shown as a square on the graph, and the second gradient value is shown as a circle on the graph. Of the first and second gradient values, the one that has been determined is shown in black, and the one that has not been determined is shown in white. In addition, the difference between the two is shown as a triangle in Figure 2. Furthermore, a dotted-dotted square frame indicates the time when the difference is greater than or equal to a predetermined value, and a double-dotted-dotted square frame indicates the time when the amount of change in the first gradient value is greater than or equal to a specified value.

[0030] First, at times t1 to t3, the absolute value of the difference between the first gradient value and the second gradient value is less than a predetermined value. Therefore, the gradient determination unit 44 determines the first gradient value as the road surface gradient. Next, at times t4 and t5, suppose the first gradient value based on the pressure sensor 10 becomes unstable, such as when the vehicle is traveling through the entrance and exit of a tunnel. In this case, for example, the first gradient value shown in Figure 2 shows a value close to 10%. At this point, the absolute value of the difference between the two becomes large and exceeds the predetermined value. Therefore, the gradient determination unit 44 determines the second gradient value as the road surface gradient.

[0031] Subsequently, between times t6 and t8, the absolute value of the difference between the first gradient value and the second gradient value became less than a predetermined value, so the gradient determination unit 44 determined the first gradient value as the road surface gradient. Next, between times t9 and t11, the absolute value of the difference between the first gradient value and the second gradient value became greater than or equal to a predetermined value. For this reason, the gradient determination unit 44 determined the second gradient value as the road surface gradient.

[0032] Next, let's assume that at times t12 to t15, the absolute value of the difference between the first gradient value and the second gradient value falls below a predetermined value, but the amount of change in the first gradient value exceeds a specified value. In this case, the gradient determination unit 44 does not determine the first gradient value as the road surface gradient, but determines the second gradient value as the road surface gradient. Subsequently, at times t16 to t18, the absolute value of the difference between the first gradient value and the second gradient value falls below a predetermined value, so the gradient determination unit 44 determines the first gradient value as the road surface gradient.

[0033] Although the process is omitted in Figure 2, it is preferable that the gradient determination unit 44, after determining the second gradient value as the road surface gradient, prohibits determining the first gradient value as the road surface gradient until the difference in the difference determination unit 43 remains below the second predetermined value for a predetermined number of consecutive times. This is because, once the second gradient value based on the acceleration sensor 20 is adopted, the first gradient value based on the pressure sensor 10 will not be adopted until it is determined that the pressure sensor 10 has stabilized. In particular, tunnels and the opening and closing of windows often occur frequently within a certain period, and determining the stability of the pressure sensor 10 in this way can further improve the accuracy of gradient calculation.

[0034] Figure 3 is a flowchart showing the road surface gradient calculation method of the road surface gradient calculation device 1 according to this embodiment. As shown in Figure 3, the control unit 40 performs speed signal input processing (S1). In this processing, the control unit 40 inputs, for example, a vehicle speed pulse as a speed signal from the vehicle speed sensor 30.

[0035] Next, the control unit 40 performs a time measurement process (S2). In this process, the control unit 40 measures the time it takes to count the vehicle speed pulse a predetermined number of times. This makes it possible to determine the vehicle speed. The predetermined number of counts is, for example, the number of minutes corresponding to a predetermined unit distance traveled. The unit distance is, for example, 50m.

[0036] Next, the control unit 40 performs pressure information input processing (S3). In this process, the control unit 40 receives pressure P information from the pressure sensor 10.

[0037] Subsequently, the control unit 40 performs altitude calculation processing (S4). In this process, the control unit 40 calculates the altitude value H based on the atmospheric pressure P information input in step S3.

[0038] Next, the control unit 40 performs acceleration calculation processing (S5). In this process, the control unit 40 receives acceleration G information from the acceleration sensor 20. Furthermore, the control unit 40 calculates the vehicle speed from a predetermined unit distance and the time measured in step S2, and calculates the calculated acceleration G' from the change between the current vehicle speed and the previous vehicle speed.

[0039] Subsequently, the first and second gradient calculation units 41 and 42 perform gradient determination processing (S6: first gradient calculation step, second gradient calculation step). In this process, the first gradient calculation unit 41 calculates a first gradient value from the difference between the current altitude value H calculated in step S4 and the previous altitude value H stored, and a predetermined unit distance. Furthermore, the second gradient calculation unit 42 calculates a second gradient value from the acceleration G information input in step S5 and the calculated acceleration G' calculated in step S5.

[0040] Subsequently, the difference determination unit 43 determines whether the difference between the first gradient value and the second gradient value is greater than or equal to a predetermined value (S7: difference determination step). If the difference is greater than or equal to the predetermined value (S7: YES), the gradient determination unit 44 determines that the atmospheric pressure P detected by the atmospheric pressure sensor 10 is unstable and determines the second gradient value as the road surface gradient (S8: gradient determination step). After that, the process moves on to step S13.

[0041] On the other hand, if the difference is not greater than or equal to a predetermined value (S7:NO), that is, if the difference is less than a predetermined value, the gradient determination unit 44 determines whether the amount of change in the first gradient value calculated in step S6 is greater than a specified value (S9). In this process, the gradient determination unit 44 determines the amount of change from the first gradient value before the predetermined section and the first gradient value calculated in step S6. The predetermined section is, for example, 200m.

[0042] If the change in the first gradient value is greater than the specified value (S9: YES), the gradient determination unit 44 determines that the atmospheric pressure P detected by the atmospheric pressure sensor 10 cannot be said to be stable, and determines the second gradient value as the road surface gradient (S8). The process then proceeds to step S13.

[0043] On the other hand, if the amount of change in the first gradient value is not greater than the specified value (S9:NO), the gradient determination unit 44 determines whether the second gradient value was determined as the road surface gradient in the previous process (S10).

[0044] If the second gradient value was determined as the road surface gradient in the previous processing (S10: YES), the difference determination unit 43 determines whether the state in which the difference determined is less than or equal to the second predetermined value has occurred for a predetermined number of consecutive times (S11).

[0045] If the difference is less than or equal to the second predetermined value for a predetermined number of consecutive times (S11:NO), the gradient determination unit 44 determines that the atmospheric pressure P detected by the atmospheric pressure sensor 10 cannot be said to be stable and determines the second gradient value as the road surface gradient (S8). After that, the process moves to step S13.

[0046] Furthermore, if the second gradient value was not determined as the road surface gradient in the previous processing (S10: NO), that is, if the first gradient value was determined as the road surface gradient in the previous processing, the process proceeds to step S12. In addition, if the difference determined by the difference determination unit 43 is less than or equal to the second predetermined value for a predetermined number of consecutive times (S11: YES), the process proceeds to step S12.

[0047] In step S12, the gradient determination unit 44 determines the first gradient value as the gradient of the road surface (S12: gradient determination process). After that, the process proceeds to step S13.

[0048] In step S13, the control unit 40 performs a slope determination process (S13). In this process, the control unit 40 determines whether it is going uphill or downhill based on the gradient of the road surface determined in step S8 or step S12, for example, and determines that it is traveling uphill or downhill if it has been going uphill or downhill a specified number of times consecutively.

[0049] Subsequently, the control unit 40 performs recording processing (S14). In this process, the control unit 40 records information such as the atmospheric pressure P and acceleration G input in steps S3 and S5, the altitude value H calculated in step S4, and the speed, first gradient value, and second gradient value calculated in step S6, in chronological order. After that, the process shown in Figure 3 is completed.

[0050] Figure 4 is a conceptual diagram showing an example of the road surface gradient calculation method of the road surface gradient calculation device 1 according to this embodiment, where (a) shows the vehicle driving state and (b) shows various values ​​at each driving point. In the example shown in Figure 4, the predetermined value, specified value, and second predetermined value are each assumed to be 5%. Also, in the example shown in Figure 4, the unit distance is assumed to be 100m.

[0051] First, as shown in Figure 4(a), let's assume the vehicle travels from -300m through 0m to +300m. Here, let's assume that at -300m, the first gradient calculation unit 41 calculates the first gradient as +11%, and the second gradient calculation unit 42 calculates the second gradient as +2.5%.

[0052] In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as 8.5% and determines that the absolute value of the difference is greater than or equal to a predetermined value. Therefore, the gradient determination unit 44 determines that the second gradient value, +2.5%, is the road surface gradient because the difference is large and the measurement by the pressure sensor 10 becomes unstable. In this case, the process proceeds to step S8 after determining "YES" at step S7 of the flowchart shown in Figure 3.

[0053] Next, suppose that at the -200m point, the first gradient calculation unit 41 calculates the first gradient value as +7%, and the second gradient calculation unit 42 calculates the second gradient value as +3%. In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as 4%, and determines that the absolute value of the difference is less than a predetermined value.

[0054] However, if the first gradient value at the -400m point before the predetermined section was +12%, the gradient determination unit 44 determines that the absolute value of the change in the first gradient value (-5%) compared to before the predetermined section is greater than or equal to the specified value. Therefore, the gradient determination unit 44 determines that the second gradient value, +3%, is the road surface gradient because, although the difference is small, it cannot be said with certainty that the atmospheric pressure P detected by the atmospheric pressure sensor 10 has stabilized. In this case, the process proceeds from step S7 in the flowchart shown in Figure 3, where it is determined to be "NO", to step S9, where it is determined to be "YES", and then to step S8.

[0055] Next, at the -100m point, the first gradient calculation unit 41 calculates the first gradient value as +2%, and the second gradient calculation unit 42 calculates the second gradient value as +2%. In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as 0%, and determines that the absolute value of the difference is less than a predetermined value.

[0056] However, since the first gradient value at the -300m point before the predetermined section is +11%, the gradient determination unit 44 determines that the absolute value of the change in the first gradient value (-9%) compared to before the predetermined section is greater than or equal to the specified value. Therefore, the gradient determination unit 44 determines that the second gradient value, +2%, is the road surface gradient because, although the difference is small, it cannot be said with certainty that the atmospheric pressure P detected by the atmospheric pressure sensor 10 has stabilized. In this case, the process proceeds to step S8, with a "YES" determination in step S9, as described above.

[0057] Next, let's assume that at point 0m, the first gradient calculation unit 41 calculates the first gradient value as +1.5%, and the second gradient calculation unit 42 calculates the second gradient value as -2.5%. In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as 4%, and determines that the absolute value of the difference is less than a predetermined value.

[0058] However, since the first gradient value at the -200m point before the predetermined section is +7%, the gradient determination unit 44 determines that the absolute value of the change in the first gradient value (-5.5%) compared to before the predetermined section is greater than or equal to the specified value. Therefore, the gradient determination unit 44 determines that the second gradient value, -2.5%, is the road surface gradient because, although the difference is small, it cannot be said with certainty that the atmospheric pressure P detected by the atmospheric pressure sensor 10 has stabilized. In this case, the process proceeds to step S8, with a "YES" determination in step S9, as described above.

[0059] Next, at the +100m point, the first gradient calculation unit 41 calculates the first gradient value as -5%, and the second gradient calculation unit 42 calculates the second gradient value as -4%. In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as -1%, and determines that the absolute value of the difference is less than a predetermined value.

[0060] However, since the first gradient value at the -100m point before the predetermined section is +2%, the gradient determination unit 44 determines that the absolute value of the change in the first gradient value (-7%) compared to before the predetermined section is greater than or equal to the specified value. Therefore, the gradient determination unit 44 determines that the second gradient value, -2.5%, is the road surface gradient because, although the difference is small, it cannot be said with certainty that the atmospheric pressure P detected by the atmospheric pressure sensor 10 has stabilized. In this case, the process proceeds to step S8, with a "YES" determination in step S9, as described above.

[0061] Next, let's assume that at the +200m point, the first gradient calculation unit 41 calculates the first gradient value as -3%, and the second gradient calculation unit 42 calculates the second gradient value as -3%. In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as 0%, and determines that the absolute value of the difference is less than a predetermined value.

[0062] Furthermore, since the first gradient value at point 0m before the predetermined section is +1.5%, the gradient determination unit 44 determines that the absolute value of the change in the first gradient value (4.5%) relative to the point before the predetermined section is less than the specified value. In addition, for the past three times (an example of the predetermined number of times), the absolute value of the difference between the first gradient value and the second gradient value has been less than or equal to the second predetermined value. Therefore, the gradient determination unit 44 determines the first gradient value, -3%, as the gradient of the road surface. In this case, the process is judged as "NO" in step S9, judged as "YES" in steps S10 and S11, and proceeds to step S12.

[0063] Next, suppose that at the +300m point, the first gradient calculation unit 41 calculates the first gradient value as -4%, and the second gradient calculation unit 42 calculates the second gradient value as -3.5%. In this case, the difference determination unit 43 calculates the difference between the first gradient value and the second gradient value as -0.5%, and determines that the absolute value of the difference is less than a predetermined value.

[0064] Furthermore, since the first gradient value at the +100m point, which is before the predetermined section, is -5%, the gradient determination unit 44 determines that the absolute value of the change in the first gradient value (-1%) compared to before the predetermined section is less than the specified value. In addition, at the previous point, +200m, the gradient determination unit 44 determined the first gradient value as the road surface gradient. Therefore, the gradient determination unit 44 determines the first gradient value, -4%, as the road surface gradient. In this case, the process is judged as "NO" in step S10 and proceeds to step S12.

[0065] In this way, according to the road surface gradient calculation device 1, road surface gradient calculation method, and road surface gradient calculation program of this embodiment, a first gradient value is determined as the road surface gradient when the difference is less than a predetermined value, and a second gradient value is determined as the road surface gradient when the difference is greater than or equal to the predetermined value. Here, a small difference means that both sensors 10 and 20 can detect the road surface with a certain degree of accuracy. For this reason, accuracy can be improved by adopting the first gradient value based on the more accurate barometric pressure sensor 10. On the other hand, a large difference means that the detection by the barometric pressure sensor 10 is inaccurate. For this reason, accuracy can be improved by adopting the second gradient value from the acceleration sensor 20. Thus, the accuracy of gradient calculation can be improved.

[0066] Furthermore, the road surface gradient calculation device 1, etc., determines the second gradient value as the road surface gradient if the amount of change in the first gradient value is greater than the specified value, even if the difference is less than a predetermined value. Therefore, in situations where gradient calculation based on the pressure sensor 10 becomes unstable, the road surface gradient calculation device 1, etc., can adopt the second gradient value based on the acceleration sensor 20 if the difference happens to become small instantaneously. Thus, the accuracy of gradient calculation can be further improved.

[0067] Furthermore, after the road surface gradient calculation device 1 determines the second gradient value as the road surface gradient, it prohibits determining the first gradient value as the road surface gradient until the difference is less than or equal to the second predetermined value for a predetermined number of consecutive times. For this reason, once the second gradient value based on the acceleration sensor 20 is adopted, the first gradient value based on the pressure sensor 10 will not be adopted until it is determined that the pressure sensor 10 has stabilized reliably. In particular, tunnels and the opening and closing of windows are often relatively continuous, and by determining the reliable stability of the pressure sensor 10 in this way, the accuracy of gradient calculation can be further improved.

[0068] Although the present invention has been described above based on embodiments, the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the invention, and other technologies may be combined as appropriate to the extent possible. Furthermore, publicly known or well-known technologies may be combined as appropriate to the extent possible.

[0069] For example, the various numerical values ​​shown in the above embodiment are not limited to those described above, and can be adjusted as appropriate. They do not have to be fixed values; they may be variable values. Also, any of the processes in steps S9 to S11 in the flowchart above may be omitted. [Explanation of Symbols]

[0070] 1: Road surface gradient calculation device 10: Barometric pressure sensor 20: Accelerometer 41: First gradient calculation unit (first gradient calculation means) 42: Second gradient calculation unit (second gradient calculation means) 43: Difference judgment unit (difference judgment means) 44: Gradient determination unit (gradient determination means)

Claims

1. A road surface gradient calculation device that calculates the gradient of the road surface on which a vehicle travels, A pressure sensor for detecting atmospheric pressure, An acceleration sensor for detecting acceleration in the direction of vehicle movement, A first gradient calculation means calculates a first gradient value indicating the gradient of the road surface based on the atmospheric pressure detected by the pressure sensor, A second gradient calculation means calculates a second gradient value indicating the gradient of the road surface based on the acceleration detected by the acceleration sensor, A difference determination means for determining whether the difference between the first gradient value calculated by the first gradient calculation means and the second gradient value calculated by the second gradient calculation means is greater than or equal to a predetermined value, A gradient determining means which determines the first gradient value as the gradient of the road surface when the difference determined by the difference determination means is less than the predetermined value, and determines the second gradient value as the gradient of the road surface when the difference determined by the difference determination means is equal to or greater than the predetermined value, A road surface gradient calculation device characterized by comprising the following features.

2. The gradient determination means determines the second gradient value as the road surface gradient when the difference determined by the difference determination means is less than the predetermined value, and the amount of change in the first gradient value calculated by the first gradient calculation means is greater than the specified value. The road surface gradient calculation device according to feature 1.

3. The gradient determination means, after determining the second gradient value as the gradient of the road surface, prohibits determining the first gradient value as the gradient of the road surface until the difference determined by the difference determination means remains below a second predetermined value for a predetermined number of consecutive times. The road surface gradient calculation device according to feature 1.

4. A road surface gradient calculation device comprising a pressure sensor for detecting atmospheric pressure and an acceleration sensor for detecting acceleration in the direction of vehicle travel, and a method for calculating the gradient of the road surface on which a vehicle travels, A first gradient calculation step, which calculates a first gradient value indicating the gradient of the road surface based on the atmospheric pressure detected by the pressure sensor, A second gradient calculation step, which calculates a second gradient value indicating the gradient of the road surface based on the acceleration detected by the acceleration sensor, A difference determination step that determines whether the difference between the first gradient value calculated in the first gradient calculation step and the second gradient value calculated in the second gradient calculation step is greater than or equal to a predetermined value, A gradient determination step in which, if the difference determined in the difference determination step is less than the predetermined value, the first gradient value is determined as the gradient of the road surface, and if the difference determined in the difference determination step is equal to or greater than the predetermined value, the second gradient value is determined as the gradient of the road surface, A road surface gradient calculation method for a road surface gradient calculation device, characterized by comprising the above.

5. A road surface gradient calculation program for causing a computer to function as a road surface gradient calculation device as described in claim 1.

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