JP2019049576A - Determination device, determination method, determination program, and recording medium - Google Patents

Abstract

To allow for detecting change in tire outer diameter during town driving, where a vehicle makes many left and right turns and often travels at low speed.SOLUTION: A rotation amount acquisition unit acquires amounts of rotation of multiple driving wheels of a vehicle. An orientation change amount acquisition unit 103 acquires an amount of orientation change of the vehicle. A determination unit 105 determines that the shapes of the driving wheels have changed based on vehicle speed pulses and the amount of orientation change. A computation unit 104 computes, for example, an orientation change amount coefficient indicative of difference in the amount of rotation between the multiple driving wheels based on the amounts of rotation and the amount of change in orientation. The determination unit 105 determines the shapes of the driving wheels have changed based on the orientation change amount coefficient.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a determination apparatus, a determination method, a determination program, and a recording medium.

  BACKGROUND Conventionally, a navigation device mounted on a mobile body such as a vehicle is known. The navigation device detects, for example, the movement of the vehicle while traveling, and presents the current position of the vehicle based on the detected movement of the vehicle. Specifically, the navigation device includes a GPS (Global Positioning System) receiver, an arithmetic processing unit, a map storage unit, a display unit, and the like.

  The navigation device calculates the current position of the vehicle based on the detection results of the vehicle speed sensor and the gyro sensor mounted on the vehicle and the position information from the GPS receiver by the function of the arithmetic processing unit. Then, the navigation device reads the map information stored in the map storage unit, superimposes the calculated current position and the map information, and causes the display unit to display the superimposed information.

  When displaying the current position on the map screen, it is necessary to accurately grasp the moving distance of the vehicle. For example, the movement distance is calculated using an output value from the vehicle speed sensor and a predetermined distance coefficient. Specifically, the vehicle speed sensor outputs vehicle speed pulses at time intervals proportional to, for example, the rotation speed of the output shaft of the transmission or the driving wheel. The navigation device calculates the movement distance by multiplying the number of pulses of the vehicle speed pulse by a predetermined distance coefficient. For example, assuming that the number of pulses per tire rotation is one pulse, and the distance coefficient is assumed to be 2 m (one step per 2 pulses), the navigation device outputs 5 pulses x 2 m when 5 pulses are output from the vehicle speed sensor. Calculate the movement distance of 10 m.

  Here, when the outer diameter of the tire is changed due to the replacement of the tire which is the driving wheel, the change of air pressure, wear, etc., the vehicle speed pulse is output before and after the outer diameter of the tire changes. The number of pulses will be different, that is, the moving distance per pulse will be different. As a result, the actual movement distance and the calculated movement distance will differ.

  Therefore, if there is a difference between the distance obtained by the GPS receiver and the distance obtained by the number of pulses of the vehicle speed pulse or more, that is, if there is a change in the tire outer diameter, the distance coefficient is corrected The technique which was made to do is proposed (for example, following patent document 1).

JP 2003-322544

  However, in the above-mentioned prior art, since the information on the distance obtained by the GPS receiver is not detailed, an error is likely to occur at a short distance, and when detecting a change in the outer diameter of the moving wheel, for example, It is necessary to move the vehicle. Therefore, in the case of a so-called city riding where a large number of turns and turns are frequently performed at a low speed, there has been a problem that it is impossible to detect a change in the outer diameter of the movable wheel.

  In order to solve the problems described above and to achieve the object, a determination apparatus according to the invention of claim 1 comprises: rotation amount acquisition means for acquiring rotation amounts of each of a plurality of moving wheels of a moving body; It is characterized by comprising: azimuth change amount acquisition means for acquiring an amount; and determination means for determining that the shape of the moving wheel has changed based on the rotation amount and the azimuth change amount.

  The determination method according to the invention of claim 13 is a determination method of a determination device mounted on a moving body, wherein the determining device is configured to obtain the amount of rotation of each of the plurality of moving wheels of the moving body. A determination step of determining that the shape of the moving wheel has changed based on an acquisition step, a direction change amount acquisition step of obtaining the direction change amount of the moving body, and the rotation amount and the direction change amount; A computer executes the process including.

  The determination program according to the invention of claim 14 causes a computer to execute the determination method according to claim 13.

  According to a fifteenth aspect of the present invention, there is provided a recording medium in which the computer-readable determination program according to the fourteenth aspect is recorded.

It is a block diagram showing an example of functional composition of a distance measuring device concerning this embodiment. It is an explanatory view showing the state at the time of vehicles turning. It is a flowchart which shows an example of the distance correction process procedure of the distance measuring device concerning this Embodiment. It is a block diagram which shows an example of the hardware constitutions of the navigation apparatus concerning a present Example. It is explanatory drawing which shows an example of the memory content of direction change amount table. It is explanatory drawing which shows an example of the memory content of a distance information table. It is a flowchart which shows an example of the distance correction procedure at the time of using the difference in the amount of rotation of the tire on either side at the time of turning of a vehicle. It is a flow chart which shows an example of the distance amendment procedure at the time of going straight. It is explanatory drawing which shows an example of the plot of the azimuth | direction change amount coefficient before and behind distance correction | amendment processing. It is explanatory drawing which shows an example of the alerting | reporting that the tire was replaced | exchanged.

  Hereinafter, preferred embodiments of a determination apparatus, a determination method, a determination program, and a recording medium according to the present invention will be described in detail with reference to the accompanying drawings.

Embodiment
(Functional configuration of distance measuring device)
The functional configuration of the distance measuring device according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing an example of a functional configuration of the distance measuring device according to the present embodiment. The distance measuring device is realized by, for example, an electronic device such as a navigation device.

  The distance measuring device 100 is mounted on a moving body provided with a pair of moving wheels arranged in parallel in a direction orthogonal to the traveling direction, and measures the moving distance of the moving body. The moving body is, for example, a vehicle. The driving wheel is, for example, a tire. Specifically, "parallelly arranged in the direction orthogonal to the traveling direction" means that the left and right driving wheels are connected by an axle. The number of axles is, for example, two for a four-wheeled vehicle, three or more for a truck or the like, and one for an auto three-wheeled vehicle.

  In the present embodiment, the distance measuring device 100 is configured to be able to determine whether or not there is a change in the tire outer diameter, using the difference in the amount of rotation of the left and right tires when the vehicle is turning. It is assumed that a vehicle is equipped with a vehicle speed sensor that outputs vehicle speed pulses at time intervals proportional to the rotational speed of the output shaft of the transmission or the tire.

  In FIG. 1, the distance measuring device 100 includes a storage unit 101, a signal acquisition unit 102, an azimuth change amount acquisition unit 103, a calculation unit 104, a determination unit 105, a correction unit 106, and a distance information acquisition unit 107. have.

  The storage unit 101 stores a distance coefficient reference value and an azimuth change amount coefficient reference value. The distance factor reference value is a reference value for measuring the moving distance of the vehicle. The distance coefficient reference value is, for example, a value indicating the distance traveled per pulse of the vehicle speed pulse from the vehicle speed sensor. The travel distance of the vehicle is calculated by multiplying the distance coefficient reference value by the vehicle speed pulse. For example, assuming that one pulse is output for each rotation of the wheel, and the distance coefficient reference value is 2 m (the wheel advances 2 m per rotation), five pulses are output from the vehicle speed sensor. A movement distance of × 2 m = 10 m is calculated.

  The azimuth change amount coefficient reference value is a reference value for calculating the difference between the rotation amounts of the left and right tires at the time of turning of the vehicle, and the details will be described later. Is a value used for comparison with the direction variation coefficient. Although the distance coefficient reference value and the direction change amount coefficient reference value may be respectively predetermined fixed values, in the present embodiment, they are updated as described later.

  The signal acquisition unit 102 acquires a rotation signal indicating the amount of rotation of each of the tires generated as the vehicle moves. The rotation signal is, for example, a vehicle speed pulse from a vehicle speed sensor. The signal acquisition unit 102 acquires, for example, left and right rotation signals of the front wheels. The signal acquisition unit 102 may acquire the left and right rotation signals of the rear wheel without being limited thereto.

  The heading change amount acquisition unit 103 acquires information on the heading change amount at which the vehicle has turned. The azimuth change amount is an angle at which the vehicle turns, and is output from a gyro sensor that detects the azimuth angle of the vehicle. The azimuth change amount may be acquired from GPS information from a GPS (Global Positioning System) receiver, a geomagnetic sensor, or the like.

  The calculation unit 104 calculates an azimuth change amount coefficient that indicates the difference in the rotation amount between the left and right tires, based on the rotation signal and the information on the azimuth change amount. Here, calculation of the azimuth change amount coefficient will be described. FIG. 2 is an explanatory view showing a state when the vehicle turns. In FIG. 2, four tires 201 as driving wheels are mounted on the vehicle 200. For example, the signal acquisition unit 102 acquires the number of pulses of the vehicle speed pulse which is a rotation signal of the left and right tires 201a and 201b of the front wheels.

Here, the azimuth change amount θ is
θ = (number of pulses of left tire−number of right tire pulses) × direction variation coefficient • ··· (1) That is, the azimuth variation coefficient is
Direction variation coefficient = θ / (number of pulses of left tire-number of right tire pulses)
It can be expressed as

For example, assuming that the azimuth change amount θ is 90 °, the number of pulses in the left tire is 10, and the number of pulses in the right tire is 20, by substituting each value into equation (1),
Orientation variation coefficient = 90 / (10-20) =-9
Is calculated. That is, the calculation unit 104 calculates the azimuth change amount coefficient by dividing the azimuth change amount by the difference of each rotation signal.

  In the present embodiment, when the direction variation coefficient is minus, it indicates a left turn, and when it is a plus, it indicates a right turn. The direction variation coefficient may be expressed as an absolute value.

  Returning to FIG. 1, the determination unit 105 compares the direction change amount coefficient calculated by the calculation unit 104 with the direction change amount coefficient reference value stored in the storage unit 101, and It is determined whether the condition 1 is satisfied. The case where the first condition is satisfied specifically means that the outer diameter of the tire is considered to be changed. For example, the ratio or difference between the direction variation coefficient and the direction variation coefficient reference value Is equal to or greater than the threshold. The change in the outer diameter of the tire is, for example, a change when replaced with a new tire, but may be a change when the tire wears.

  If the determination unit 105 determines that the first condition is satisfied, the correction unit 106 corrects the azimuth change amount coefficient reference value and the distance coefficient reference value stored in the storage unit 101. The value to be corrected may be a preset setting value, or may be a value based on an azimuth change amount coefficient that is equal to or greater than a threshold, as described later.

  Further, in the present embodiment, the determination unit 105 determines that the difference between the direction change amount coefficient calculated by the calculation unit 104 and the direction change amount coefficient reference value stored in the storage unit 101 is a first predetermined number of times. If it becomes equal to or greater than the threshold value, it is determined that the azimuth change amount coefficient satisfies the first condition. In other words, even if the difference between the direction change amount coefficient and the direction change amount coefficient reference value becomes equal to or larger than the threshold, the determination unit 105 does not determine that the first condition is satisfied if the first predetermined number of times does not continue. . This may cause an error in the calculation of the above-mentioned change coefficient of direction change due to a step or slip at the time of turning, but prevents such a difference from determining that the outer diameter of the tire has changed. It is for.

  Furthermore, in the present embodiment, when determination section 105 determines that the first condition is satisfied, correction section 106 determines the azimuth change amount coefficient to be a value obtained by averaging the first predetermined number of the azimuth change amount coefficients. Correct the value. That is, the correction unit 106 corrects the azimuth change amount coefficient reference value to a value obtained by averaging the azimuth change amount coefficients for the first predetermined number of times exceeding the threshold. Thus, the azimuth change amount coefficient reference value can be made close to the azimuth change amount coefficient that has become equal to or greater than the actually calculated threshold value.

  Note that the value to be corrected is not limited to the value obtained by averaging the first predetermined number of direction variation coefficients, and a plurality of previously determined direction variation coefficients when it is determined that there is a tire outer diameter variation It may be an averaged value. Even with such a configuration, the azimuth change amount coefficient reference value can be made close to the azimuth change amount coefficient that is equal to or greater than the threshold before it is determined that there is a tire outer diameter change.

  Further, in the present embodiment, when the vehicle turns a predetermined angle or more, calculation unit 104 starts calculation of the azimuth change amount coefficient. The difference or ratio of the vehicle speed pulses may be used to determine whether the vehicle has turned a predetermined angle or more, or the direction change amount may be used. From the viewpoint that the difference between the vehicle speed pulses of both wheels becomes large, the calculation of the azimuth change amount coefficient is more accurate as the azimuth change amount is larger. As a result, it is possible to make it difficult to calculate a unique value of the azimuth change amount coefficient due to an error, and it is possible to determine with high accuracy whether the azimuth change amount coefficient satisfies the first condition.

  Further, the correction unit 106 updates the azimuth change amount coefficient reference value stored in the storage unit 101 using the azimuth change amount coefficient calculated by the calculation unit 104. To update is to average the azimuth variation coefficient reference value by adding the azimuth variation coefficient calculated by the calculation unit 104 to the azimuth variation coefficient reference value stored in the storage unit 101. . If the determination unit 105 determines that the first condition is not satisfied, the correction unit 106 updates the azimuth change amount coefficient reference value stored in the storage unit 101.

  Here, the calculation of the azimuth change amount coefficient reference value will be specifically described. The azimuth change amount coefficient reference value is obtained by averaging the azimuth change amount coefficient. The azimuth change amount coefficient reference value is updated as needed each time the azimuth change amount coefficient is calculated. The newly updated orientation variation coefficient reference value can be expressed by the following equation (2).

Assuming that the azimuth change coefficient reference value newly updated is α1, the azimuth change coefficient reference value already stored is α2, and the azimuth change coefficient calculated this time is β:
α 1 = α 2 + (α 2 -β) / number of calculations L (2) The number of times of calculation L is the number of times of calculation of the orientation change amount coefficient, and the ratio of β to α1 decreases as the number of times increases, that is, the value of β is more difficult to reflect on α1 as the number of times increases.

  The correction unit 106 does not add a unique value of the azimuth change coefficient due to an error to the azimuth change coefficient reference value, the ratio or difference between the azimuth change coefficient and the azimuth change coefficient reference value is If it is equal to or higher than the threshold (if the first condition is satisfied), the azimuth change amount coefficient reference value may not be updated using the azimuth change amount coefficient. Thus, the azimuth change amount coefficient reference value can be updated using only the azimuth change amount coefficient less than the threshold, and the azimuth change amount coefficient reference value can be made accurate.

  When the correction unit 106 corrects the azimuth change amount coefficient reference value and the distance coefficient reference value, the correction unit 106 also corrects the “number of calculations L” shown in equation (2) at the same time. Note that, as described above, as the number of calculations L increases, the ratio of “the newly calculated azimuth change coefficient coefficient β to the newly updated azimuth change coefficient reference value α1” decreases as the number of times increases, ie, As the number of times increases, the value of β is less likely to be reflected on α1. Therefore, by performing correction that reduces the number of calculations L as well, it is easy to reflect the direction change amount coefficient calculated later on the corrected direction change amount coefficient reference value.

  For example, the correction unit 106 may correct the number of calculations L to a first predetermined number. That is, in the correction of the azimuth change amount coefficient reference value, the calculation number L may be corrected to the same number of times as the azimuth change amount coefficient is actually calculated. The number of calculations L to be reduced by the correction unit 106 may be a predetermined number, or may be the smallest “1” from the viewpoint of making it easier to reflect the direction variation coefficient calculated later.

  Further, in the present embodiment, the distance measuring device 100 can detect that there is a change in the tire using the distance information and the rotation signal while traveling straight. Specifically, the distance information acquisition unit 107 acquires distance information indicating the travel distance of the vehicle. For example, the distance information acquisition unit 107 acquires distance information by the GPS receiver.

  The calculation unit 104 calculates a distance coefficient for measuring the moving distance of the vehicle when the vehicle goes straight, based on the rotation signal (vehicle speed pulse), the information of the azimuth change amount, and the distance information. Specifically, calculation unit 104 determines that the vehicle is going straight by using the information on the amount of change in direction, and if the vehicle is going straight, the distance based on the vehicle speed pulse and the distance based on the distance information The distance factor is calculated by comparing

Specifically, the distance factor can be expressed by the following equation (3).
Distance information = vehicle speed pulse × distance coefficient (3) That is, the distance coefficient is
It can be expressed as distance coefficient = distance information / vehicle speed pulse. For example, if the distance information advances 100 m and the rotation signal is 50 pulses, the distance coefficient is calculated as 2 m. In addition, what is necessary is just to use the vehicle speed pulse of at least one tire as a vehicle speed pulse in calculation of a distance coefficient.

  The determination unit 105 determines whether the distance coefficient satisfies the second condition by comparing the distance coefficient calculated by the calculation unit 104 with the distance coefficient reference value stored in the storage unit 101. . The case where the second condition is satisfied specifically means that the outer diameter of the tire is considered to have changed, for example, the ratio or difference between the distance factor and the distance factor reference value is equal to or more than the threshold value. Is the case.

  If the determination unit 105 determines that the second condition is satisfied, the correction unit 106 corrects the azimuth change amount coefficient reference value and the distance coefficient reference value stored in the storage unit 101. The value to be corrected may be a preset set value, or may be a value based on a distance factor which is equal to or greater than a threshold, as described later.

  Further, in the present embodiment, determination unit 105 determines that the difference between the distance coefficient calculated by calculation unit 104 and the distance coefficient reference value stored in storage unit 101 is continuously greater than or equal to the second predetermined number of times. If it does, it is determined that the distance factor satisfies the second condition. In other words, even if the difference between the distance factor and the distance factor reference value is equal to or greater than the threshold, the determining unit 105 does not determine that the second condition is satisfied if the second predetermined number of times does not occur. This is because an error may occur in the calculation of the distance coefficient due to a step or slip at the time of going straight, but in order to prevent determination that there is a change in the tire outer diameter due to such an error. is there.

  Furthermore, in the present embodiment, the correction unit 106 corrects the distance coefficient reference value to a value obtained by averaging the second predetermined number of distance coefficients when the determination unit 105 determines that the second condition is satisfied. That is, the correction unit 106 corrects the distance coefficient reference value to a value obtained by averaging the second predetermined number of distance coefficients exceeding the threshold value. Thus, the distance factor reference value can be made close to the value (distance factor) actually calculated.

  The value to be corrected is not limited to the value obtained by averaging the second predetermined number of distance coefficients, and is a value obtained by averaging a plurality of previously determined distance coefficients when it is determined that the tire outer diameter has changed. It may be Even with such a configuration, the distance coefficient reference value can be made close to the distance coefficient that is equal to or greater than the threshold before it is determined that there is a tire outer diameter change.

  Further, in the present embodiment, when the vehicle is traveling at a predetermined speed or more, calculation unit 104 starts calculation of the distance coefficient. For example, a vehicle speed pulse may be used to determine whether the vehicle is traveling at a predetermined speed or higher. In the calculation of the distance factor, the higher the distance information from the GPS receiver, the higher the accuracy. As a result, it is possible to make it difficult to calculate a unique value of the distance coefficient due to an error, and it is possible to determine with high accuracy whether the distance coefficient satisfies the second condition.

  If the determination unit 105 determines that the second condition is not satisfied, the correction unit 106 updates the distance coefficient reference value stored in the storage unit 101. To update is to average the distance factor reference value by adding the distance factor calculated by the calculation unit 104 to the distance factor reference value stored in the storage unit 101.

  Here, the calculation of the distance coefficient reference value will be specifically described. The distance factor reference value is obtained by averaging distance factors. The distance factor reference value is updated as needed each time the distance factor is calculated. The newly updated distance factor reference value can be expressed by the following equation (4).

Assuming that the newly stored distance factor reference value is γ1, the already stored distance factor reference value is γ2, and the distance factor currently calculated is δ.
γ 1 = γ 2 + (γ 2 −δ) / number of calculations M (4) The number of calculations M is the number of times the distance coefficient is calculated, and the ratio of δ to γ1 decreases as the number increases, that is, the value of δ is less likely to be reflected on γ1.

  If the ratio or difference between the distance factor and the distance factor reference value is greater than or equal to the threshold value (second value), the correction unit 106 does not add the unique value of the distance factor due to an error to the distance factor reference value. If the condition is satisfied), the distance factor reference value may not be updated using the distance factor. Thus, the distance factor reference value can be updated using only the distance factor less than the threshold value, and the distance factor reference value can be made accurate.

  When the correction unit 106 corrects the azimuth change amount coefficient reference value and the distance coefficient reference value, the correction unit 106 also corrects the “number of calculations M” shown in equation (4) at the same time. Note that, as described above, as the number of calculations M increases, the ratio of “the currently calculated distance factor δ to the newly updated distance factor reference value γ1” decreases as the number of times increases, that is, the number increases. The value of δ is less likely to be reflected with respect to γ1. Therefore, by performing correction that reduces the number of calculations L as well, it is easy to reflect the distance coefficient calculated later on the corrected distance coefficient reference value.

  For example, the correction unit 106 may correct the number of calculations M to a second predetermined number. That is, in the correction of the distance coefficient reference value, the number M of times of calculation may be corrected to the same number as the number of times the distance coefficient is actually calculated. Note that the calculation number M to be decreased by the correction unit 106 may be a predetermined number, or may be the smallest “1” from the viewpoint of making it easier to reflect the distance coefficient calculated later.

(Procedure of distance correction process of distance measuring device)
Next, the distance correction processing procedure of the distance measuring device 100 will be described using FIG. 3. FIG. 3 is a flowchart showing an example of the distance correction processing procedure of the distance measuring device 100 according to the present embodiment.

  In the flowchart of FIG. 3, the distance measuring device 100 determines whether the vehicle has turned based on the direction change amount, the difference between the vehicle speed pulses, and the like (step S301). The distance measuring device 100 stands by until the vehicle turns (step S301: No), and when the vehicle turns (step S301: Yes), calculates the azimuth change amount coefficient (step S302). The equation (1) described above is used to calculate the direction change amount coefficient.

  Then, the distance measuring device 100 determines whether the orientation change amount coefficient satisfies the first condition (step S303). The case where the first condition is satisfied means that the change in tire outer diameter is considered to be satisfied, for example, the difference between the direction change amount coefficient and the direction change amount coefficient reference value is equal to or more than the threshold value. In the case where the difference is equal to or more than the threshold value continuously a predetermined number of times.

  When the azimuth change amount coefficient does not satisfy the first condition (step S303: No), the distance measuring device 100 calculates an average value of the azimuth change amount coefficient reference values (step S304). The above equation (2) is used to calculate the average value of the azimuth change amount coefficient reference value. Then, the distance measurement device 100 updates the stored azimuth change amount coefficient reference value to the calculated azimuth change amount coefficient reference value (step S305), and shifts the process to step S301.

  In step S303, when the direction change amount coefficient satisfies the first condition (step S303: Yes), that is, when the condition that can be regarded as tire replacement is satisfied, the distance measuring device 100 stores The azimuth change amount coefficient reference value is corrected (step S306). Then, the distance measuring device 100 corrects the stored distance coefficient reference value (step S307), and ends the series of processing according to this flowchart.

  As described above, the distance measuring device 100 according to the present embodiment determines the change in the outer diameter of the tire using the difference in the amount of rotation of the left and right tires at the time of turning of the vehicle, Correct the value and distance factor reference value. As a result, it is possible to detect changes in the outer diameter of the tire and correct each reference value in so-called city riding where many left and right turns and frequent movement at low speed are performed. Therefore, various reference values can be corrected quickly, and accurate distances can be measured.

  In addition, when the vehicle turns a predetermined angle or more, the distance measuring device 100 according to the present embodiment starts detection of a change in tire outer diameter using a difference in the amount of rotation of the left and right tires. Therefore, it is possible to detect a change in the outer diameter of the tire after the difference between the vehicle speed pulses of both wheels reaches a predetermined value or more, and it is possible to improve the calculation accuracy of the direction change amount coefficient. Therefore, the change in tire outer diameter can be detected with high accuracy, and a more accurate distance can be measured.

  Furthermore, in the present embodiment, it is determined that the tire outer diameter has a change when the difference between the direction change amount coefficient and the direction change amount coefficient reference value becomes equal to or more than the threshold value continuously a predetermined number of times. did. As a result, when an error occurs in the calculation of the direction change amount coefficient due to a step or slip at the time of turning, it is possible to suppress the detection of the change in the tire outer diameter by such an error. Therefore, the change in tire outer diameter can be detected with high accuracy, and a more accurate distance can be measured.

  Further, in the present embodiment, when there is a change in the tire outer diameter, the direction change amount coefficient reference value is corrected to a value obtained by averaging a predetermined number of direction change amount coefficients. Thus, the azimuth change coefficient reference value can be made close to the azimuth change coefficient that is equal to or greater than the actually calculated threshold value, and subsequent changes in tire outer diameter can be detected with high accuracy. . Therefore, an accurate distance can be measured.

  Further, in the present embodiment, the azimuth change amount coefficient reference value is updated using the azimuth change amount coefficient calculated each time of turning. In this way, it is possible to generate an azimuth variation coefficient reference value that takes into account the wear of the tire that is gradually worn away. Therefore, the azimuth change amount coefficient reference value can be generated from the actual traveling, and the change of the tire outer diameter for each vehicle can be detected with high accuracy. When it is determined that the first condition is satisfied, if the azimuth change coefficient reference value is not updated, a unique value of the azimuth change coefficient due to an error is added to the azimuth change coefficient reference value. Can be avoided, and the azimuth variation coefficient reference value can be made accurate.

  Furthermore, the distance measuring device 100 according to the present embodiment uses the distance information and the rotation signal to determine the change in the outer diameter of the tire while the vehicle is traveling straight. As a result, even when moving straight, it is possible to detect changes in the outer diameter of the tire and correct each reference value. Therefore, various reference values can be corrected quickly, and accurate distances can be measured.

  Hereinafter, examples of the present invention will be described. A present Example demonstrates an example at the time of implementing the distance measuring device 100 comprised with a navigation apparatus.

(Hardware configuration of navigation device)
The hardware configuration of the navigation device 400 according to the present embodiment will be described using FIG. 4. FIG. 4 is a block diagram showing an example of the hardware configuration of the navigation device 400 according to the present embodiment.

  In FIG. 4, the navigation device 400 includes a CPU 401, a ROM 402, a RAM 403, a magnetic disk drive 404, a magnetic disk 405, an optical disk drive 406, an optical disk 407, an audio I / F (interface) 408, and a speaker 409. , An input device 410, an image I / F 411, a display 412, a communication I / F 413, a GPS unit 414, and various sensors 415. Each of the component units 401 to 415 is connected by a bus 420.

  The CPU 401 is in charge of overall control of the navigation device 400. The rewritable non-volatile memory such as the ROM 402 and the flash ROM stores various programs such as a boot program, a current point calculation program, a route search program, a route guidance program, a distance correction program, and a reference value update program. Further, the RAM 403 is used as a work area of the CPU 401.

  The current point calculation program is, for example, a program for calculating the current point of the vehicle (the current point of the navigation device 400) based on output information of a GPS unit 414 described later and a vehicle speed sensor that outputs a vehicle speed pulse.

  The route search program is a program for searching for an optimum route from the departure point to the destination point using map data, route calculation data, and the like recorded on the magnetic disk 405. The optimal route is, for example, the shortest (or fastest) route to the destination point or the route that most matches the conditions specified by the user. Also, not only the destination point but also a route to a stop point or a break point may be searched. The searched guidance route is output to the audio I / F 408 and the video I / F 411 via the CPU 401.

  The route guidance program includes guidance route information searched by executing the route search program, information of the current position of the vehicle calculated by executing the current position calculation program, and a map read from the magnetic disk 405 It is a program that generates real-time route guidance information based on data and the like. The generated route guidance information is output to the audio I / F 408 and the video I / F 411 via the CPU 401.

  The distance correction program detects that there is a change in the outer diameter of the tire using a vehicle speed sensor that outputs a vehicle speed pulse, a gyro sensor that outputs an azimuth change amount, GPS information of the GPS unit 414, etc. This is a program for correcting the variation coefficient reference value and the distance coefficient reference value. The reference value update program is a program for calculating an azimuth change amount coefficient or a distance coefficient and updating various reference values using each coefficient.

  The magnetic disk drive 404 controls the reading / writing of the data with respect to the magnetic disk 405 according to control of CPU401. The magnetic disk 405 records the data written under the control of the magnetic disk drive 404. As the magnetic disk 405, for example, an HD (hard disk) or an FD (flexible disk) can be used. On the magnetic disk 405, in addition to map data and route calculation data, for example, an azimuth variation coefficient reference value and a distance coefficient reference value are recorded. The storage unit 101 shown in FIG. 1 is realized by, for example, the magnetic disk 405.

  The optical disk drive 406 controls the reading / writing of the data with respect to the optical disk 407 according to control of CPU401. The optical disk 407 is a removable recording medium from which data can be read according to the control of the optical disk drive 406. The optical disc 407 can also use a writable recording medium. In addition to the optical disk 407, an MO, a memory card or the like may be used as the removable recording medium.

  The audio I / F 408 is connected to the speaker 409. Audio information is output from the speaker 409. The input device 410 may be a remote control provided with a plurality of keys for inputting characters, numerical values, and various instructions, a keyboard, a mouse, a touch panel, and the like. The input device 410 may be realized by any one of a remote control, a keyboard, a mouse and a touch panel, or may be realized by a plurality of modes.

  The video I / F 411 is connected to the display 412. Specifically, the video I / F 411 includes, for example, a graphic controller that controls the entire display 412, a buffer memory such as a VRAM (Video RAM) that temporarily records image information that can be displayed immediately, and a graphic controller It is comprised by control IC etc. which carry out display control of the display 412 based on the output image data.

  The display 412 displays icons, cursors, menus, windows, or various data such as characters and images. For example, a CRT, a TFT liquid crystal display, a plasma display, or the like can be adopted as the display 412.

  The communication I / F 413 is wirelessly connected to a communication network such as the Internet, and functions as an interface between the communication network and the CPU 401. The GPS unit 414 receives radio waves from GPS satellites and outputs information indicating the current position of the vehicle. The output information of the GPS unit 414 is used when the CPU 401 calculates the current position of the vehicle. The information indicating the current position is, for example, information specifying one point on the map data, such as latitude / longitude and altitude.

  The various sensors 415 output information that can determine the position and behavior of the vehicle, such as a vehicle speed sensor, an acceleration sensor, and a gyro sensor. The vehicle speed sensor outputs a vehicle speed pulse. The gyro sensor outputs an azimuth change amount. The output values of the various sensors 415 are used for calculation of the current position of the vehicle by the CPU 401, measurement of the amount of change in speed and direction, and the like.

  A signal acquisition unit 102, an azimuth change amount acquisition unit 103, a calculation unit 104, a determination unit 105, a correction unit 106, and a distance information acquisition unit included in the distance measurement device 100 according to the present embodiment shown in FIG. The function 107 is realized by causing the CPU 401 to execute various programs using programs and data recorded in the ROM 402, the magnetic disk 405, and the like in the navigation device 400 shown in FIG.

(An example of information stored in the navigation device 400)
Next, an example of information stored in the navigation device 400 will be described. The navigation device 400 stores an azimuth change amount table and a distance information table. These tables are realized by the magnetic disk 405 of the navigation device 400.

<Example of Memory Contents of Orientation Change Amount Table>
FIG. 5 is an explanatory diagram of an example of the storage content of the orientation change amount table. In FIG. 5, the azimuth change amount table 500 has an azimuth change amount coefficient field, an azimuth change amount coefficient reference value field, and a difference field. By setting information in each of these fields, the azimuth change amount table 500 includes azimuth change amount information 500-1 to 500-3, etc. for each combination of the azimuth change amount coefficient, the azimuth change amount coefficient reference value, and the difference. It is stored as a record.

  The orientation change amount coefficient is a value representing the difference in the amount of rotation between the left and right tires, and is a value calculated by the above-mentioned equation (1) when the vehicle turns (see the embodiment). The azimuth change amount coefficient reference value is a value obtained by averaging the azimuth change amount coefficients calculated as needed, and is a value calculated by the above-mentioned equation (2) (see the embodiment).

  In the direction change amount coefficient field, for example, information of the direction change amount coefficient calculated as needed is stored. Further, in the direction change amount coefficient reference value field, information of the direction change amount coefficient reference value calculated as needed is stored. In the difference field, difference information between the azimuth change amount coefficient reference value and the azimuth change amount coefficient is stored.

  For example, “α11” calculated using “β11” for the azimuth change amount coefficient field and “β11” for the azimuth change amount coefficient reference value field in the azimuth change amount information 500-1 and the difference field "H11" is stored. Here, “α12” is an average value obtained by adding “β11” and “β12”, and “α13” is an average value obtained by adding “β11”, “β12” and “β13”. The azimuth change coefficient reference value is such that as the calculated azimuth change coefficient increases, that is, as the number L of calculations of the azimuth change coefficient increases, the value of each azimuth change coefficient is less likely to be reflected. is there.

<Example of Memory Contents of Distance Information Table>
FIG. 6 is an explanatory diagram of an example of the storage content of the distance information table. In FIG. 6, the distance information table 600 has a distance factor field, a distance factor reference value field, and a difference field. By setting information in each of these fields, distance information 600-1 to 600-3 and the like for each combination of distance factor, distance factor reference value, and difference are stored in the distance information table 600 as a record.

  The distance coefficient is a value indicating the distance traveled per one pulse of the vehicle speed pulse from the vehicle speed sensor, and is a value calculated by the above-described equation (3) when the vehicle travels straight ahead (see the embodiment). ). The distance coefficient reference value is a value obtained by averaging the distance coefficients calculated as needed, and is a value calculated by the above-mentioned equation (4) (see the embodiment).

  In the distance coefficient field, for example, information on distance coefficients calculated at any time is stored. Further, in the distance factor reference value field, information of the distance factor reference value calculated at any time is stored. In the difference field, difference information between the distance factor reference value and the distance factor is stored. For example, in the distance information 600-1, “γ11” calculated using “δ11” in the distance factor field, “δ11” in the distance factor reference value field, and “I11” in the difference field are stored. ing.

  Note that “γ12” is an average value obtained by adding “δ11” and “δ12”, and “γ13” is an average value obtained by adding “δ11”, “δ12” and “δ13”. The distance factor reference value is such that the value of each distance factor is less likely to be reflected as the calculated distance factor increases, in other words, as the number of times M of calculating the distance factor increases.

(Procedure of distance correction processing of navigation device 400)
Next, the distance correction processing procedure of the navigation device 400 will be described using FIGS. 7 and 8. FIG. 7 is a flowchart showing an example of the distance correction procedure when using the difference in the amount of rotation of the left and right tires when the vehicle is turning.

  In the flowchart of FIG. 7, the navigation device 400 determines whether the vehicle has turned by a predetermined angle or more from the azimuth change amount, the difference between the vehicle speed pulses, and the like (step S701). The navigation device 400 stands by until the vehicle turns more than the predetermined angle (step S701: No), and when the vehicle turns more than the predetermined angle (step S701: Yes), the azimuth change amount coefficient is calculated (step S702). The above equation (1) is used to calculate the direction change amount coefficient (see the embodiment).

  Then, the navigation device 400 calculates a difference H obtained by subtracting the direction change amount coefficient from the direction change amount coefficient reference value (step S703). Then, the navigation device 400 determines whether the difference H is equal to or greater than a predetermined threshold value S (step S704). When the difference H is less than the threshold S (step S704: No), the navigation device 400 sets the count value K, which is counted when the difference H continuously exceeds the threshold S, to "0" (step S705). ).

  Then, the navigation device 400 calculates the azimuth change amount coefficient reference value using the azimuth change amount coefficient calculated in step S702 in order to update the azimuth change amount coefficient reference value (step S706). The above equation (2) is used to calculate the azimuth change amount coefficient reference value (see the embodiment). Then, the navigation device 400 stores the calculated azimuth change amount coefficient reference value (step S 707), and shifts to the process of step S 701.

  In step S704, when the difference H is equal to or larger than the threshold value S (step S704: Yes), the navigation device 400 adds “1” to the count value K (step S708). Then, it is determined whether the count value K has reached a preset threshold T (step S709). If the count value K is not equal to the threshold value T (step S709: No), that is, if the difference H is not equal to or more than the threshold value S continuously for T times, the navigation device 400 shifts the process to step S701.

  When the count value K becomes the threshold value T (step S709: Yes), that is, when the difference H becomes T value or more continuously in T times, the navigation device 400 corrects the azimuth change amount coefficient reference value ( Step S710). The value to be corrected here may be a preset set value, but the direction change amount averaged using only the direction change amount coefficient calculated T times in consideration of the value at the time of actual traveling, for example The coefficient reference value is used.

  In addition, although correction of the azimuth change amount coefficient reference value is performed when the difference H becomes T threshold value or more in succession in T times, this is, for example, when crossing over the step or when the tire is stuck This is in order not to use a unique change in direction coefficient in case of slipping or the like in the determination of the change in tire outer diameter. That is, it is for not judging that there is a change in the tire outer diameter by the unique direction change amount coefficient.

  Then, the navigation device 400 sets the number L of calculations of the orientation change amount coefficient of the above-mentioned equation (2) to T (step S711). Next, the navigation device 400 corrects the distance coefficient reference value (step S712). The value to be corrected here may be a preset set value, but in consideration of the value at the time of actual traveling, for example, a distance factor reference averaged using only the latest X times of the distance factor calculated. It will be a value. Note that X can be set arbitrarily.

  Then, the navigation device 400 sets the number of calculation times M of the distance coefficient of the above-mentioned equation (4) to X (step S713). Next, the navigation device 400 notifies the display 412 that the tire has been replaced (step S714), and ends the series of processing according to this flowchart. An example of notification that the tire has been replaced will be described later with reference to FIG.

  In the process described above, when the difference H becomes equal to or larger than the threshold value S, the azimuth change amount coefficient is not used to calculate the azimuth change amount coefficient reference value. This is because, for example, assuming that the tire has already been changed, the azimuth change coefficient reference value is not updated so as to approach the changed tire outer diameter before the correction of the azimuth change coefficient reference value. In order to In addition, a unique calculation result is not added to the azimuth variation coefficient reference value, and the azimuth variation coefficient reference value is made accurate.

  In addition, when the vehicle turns more than a predetermined angle, detection of the change in the tire outer diameter using the difference in the amount of rotation of the left and right tires is started, so that the change in the tire outer diameter is detected with high accuracy. Can measure the distance more accurately.

  Furthermore, when the difference between the azimuth change amount coefficient and the azimuth change amount coefficient reference value continuously exceeds the threshold a predetermined number of times, the change in the tire outer diameter is detected, so a step or slip at the time of turning, etc. Thus, when an error occurs in the calculation of the direction change amount coefficient, it is possible to suppress the detection of the change in the tire outer diameter by such an error. Therefore, the change in tire outer diameter can be detected with high accuracy, and a more accurate distance can be measured.

  In addition, when there is a change in the tire outer diameter, the azimuth change coefficient reference value is corrected to a value obtained by averaging the predetermined number of azimuth change coefficients, so the azimuth change coefficient reference value is actually calculated. It can be close to the azimuth variation coefficient that has become equal to or higher than the threshold value. Therefore, the subsequent change in tire outer diameter can be detected with high accuracy, and an accurate distance can be measured.

  Further, the azimuth change amount coefficient reference value is updated using the azimuth change amount coefficient calculated each time the vehicle turns. In this way, it is possible to generate an azimuth variation coefficient reference value that takes into account the wear of the tire that is gradually worn away. Therefore, the azimuth change amount coefficient reference value can be generated from the actual traveling, and the change of the tire outer diameter for each vehicle can be detected with high accuracy. Further, when the difference H becomes equal to or larger than the threshold value S, the azimuth change amount coefficient reference value is not updated. This is because, for example, if it is determined that the tire has already been changed before it is determined that there is a change in the tire outer diameter, the orientation change amount coefficient reference value is not updated to approach the changed tire outer diameter. It is to do so. Therefore, a unique calculation result can be avoided from being added to the azimuth variation coefficient reference value, and the azimuth variation coefficient reference value can be made accurate.

  Further, in the present embodiment, the navigation device 400 has the route searching function and the route guiding function, so before traveling, it is detected in advance which curve has a curvature radius at which place. Alternatively, the above process may be performed only on a predetermined curve suitable for the above process. Thus, for example, a portion where a level difference is assumed during turning, such as when entering a parking lot of a facility, or a portion where a sharp curve where a bank angle is provided may be excluded from the above processing. it can. That is, the optimum curve on the route suitable for the above process can be selected, and the above process can be performed on the selected curve. Therefore, the change of the tire outer diameter can be detected with high accuracy.

  Further, in such a configuration, the user is notified in advance or at the timing of performing the above processing that the determination as to whether or not there is a change in the tire outer diameter and that the user is urged to run along the curve. You may As a result, it is possible to suppress abrupt steering in a curve, meandering travel, and the like, and it is possible to detect a change in tire outer diameter with high accuracy.

  FIG. 8 is a flow chart showing an example of a distance correction procedure when going straight. In the flowchart of FIG. 8, the navigation device 400 determines whether the vehicle is traveling straight at a high speed or not based on the azimuth change amount, the vehicle speed pulse, and the like (step S801). High speed means that the speed is equal to or higher than a predetermined speed. The navigation device 400 stands by until the vehicle travels straight and traveling at high speed (step S801: No), and when the vehicle travels straight and traveling at high speed (step S801: Yes), the distance coefficient is calculated (step S801). Step S802). The distance factor is calculated, for example, by dividing the moving distance detected by the GPS unit 414 by the vehicle speed pulse.

  Then, the navigation device 400 calculates a difference I obtained by subtracting the distance factor from the distance factor reference value (step S803). Then, the navigation device 400 determines whether the difference I is equal to or greater than a predetermined threshold U (step S804). When the difference I is less than the threshold U (step S804: No), the navigation device 400 sets the count value J to be counted when the difference I becomes continuously greater than or equal to the threshold U (step S805). ).

  Then, in order to update the distance coefficient reference value, the navigation device 400 calculates the distance coefficient reference value using the distance coefficient calculated in step S802 (step S806). The equation (4) described above is used to calculate the average value of the distance factor reference values (see the embodiment). Then, the navigation device 400 stores the calculated distance coefficient reference value (step S807), and shifts to the processing of step S801.

  In step S804, when the difference I is equal to or greater than the threshold value U (step S804: Yes), the navigation device 400 adds “1” to the count value J (step S808). Then, it is determined whether the count value J has reached a preset threshold value V (step S809). If the count value J is not equal to the threshold value V (step S809: No), that is, if the difference I is not equal to or greater than the threshold value U continuously for V times, the navigation device 400 shifts the process to step S801.

  When the count value J becomes the threshold value V (step S809: Yes), that is, when the difference I becomes the threshold value U or more consecutively V times, the navigation device 400 corrects the azimuth change amount coefficient reference value ( Step S810). The value to be corrected here may be a preset set value, but in consideration of the value when actually traveling, for example, the azimuth averaged using only the latest Y-fold change amount coefficient of azimuth calculated Set as change coefficient reference value. Note that Y can be set arbitrarily.

  Then, the navigation device 400 sets the number of calculations L of the orientation change amount coefficient of the above-mentioned equation (2) to Y (step S811). Next, the navigation device 400 corrects the distance coefficient reference value (step S812). The value to be corrected here may be a preset set value, but in consideration of the value when actually traveling, for example, a distance factor reference value averaged using only the distance factor calculated V times and Do.

  Although correction of the distance coefficient reference value is performed when the difference I becomes equal to or more than the threshold value U continuously V times, this is, for example, when crossing over the step or when the tire is stuck or slipped. This is in order not to use a unique distance coefficient in cases such as when determining changes in the outer diameter of the tire. That is, it is for not judging that there is a change in the outer diameter of the tire due to the unique distance coefficient.

  Then, the navigation device 400 sets the number M of calculation of the distance coefficient of the above-mentioned equation (4) to V (step S813). Next, the navigation device 400 notifies the display 412 that the tire has been replaced (step S 814), and ends the series of processing according to this flowchart. An example of notification that the tire has been replaced will be described later with reference to FIG.

  According to the above-described processing, it is possible to detect a change in tire outer diameter using distance information and vehicle speed pulses while the vehicle is traveling straight. Therefore, even when moving straight, it is possible to detect changes in the outer diameter of the tire and correct each reference value. As a result, various reference values can be corrected quickly, and accurate distances can be measured.

  Further, when the vehicle is traveling at a predetermined speed or more, detection of a change in tire outer diameter using a distance coefficient is started, so distance information with high accuracy from the GPS receiver can be used. The change in tire outer diameter can be detected with high accuracy, and a more accurate distance can be measured.

  Furthermore, when the difference between the distance factor and the distance factor reference value continuously exceeds the threshold a predetermined number of times, the change in the tire outer diameter is detected, so the distance factor is not When an error occurs in the calculation, it is possible to suppress the detection of the change in the tire outer diameter by such an error. Therefore, the change in tire outer diameter can be detected with high accuracy, and a more accurate distance can be measured.

  In addition, since the distance factor reference value is corrected to a value obtained by averaging the predetermined number of distance factors when there is a change in the tire outer diameter, the distance factor reference value becomes equal to or more than the actually calculated threshold value. It can be close to the distance factor. Therefore, the subsequent change in tire outer diameter can be detected with high accuracy, and an accurate distance can be measured.

  In addition, the distance factor reference value is updated using the distance factor which is calculated each time the vehicle travels straight and at high speed. As a result, it is possible to generate a distance factor reference value that takes into account the tire wear that is gradually worn away, and to measure an accurate distance that takes into account the tire wear. Therefore, the distance factor reference value can be generated from actual travel, and changes in the tire outer diameter for each vehicle can be detected with high accuracy. Further, when the difference I becomes equal to or larger than the threshold U, the distance coefficient reference value is not updated. This is because, for example, if it is determined that the tire has already been changed before it is determined that there is a change in the outer diameter of the tire, the distance coefficient reference value is not updated to approach the changed outer diameter of the tire. In order to Therefore, the unique calculation result can be avoided from being added to the distance factor reference value, and the distance factor reference value can be made accurate.

  Further, in the present embodiment, since navigation device 400 is provided with a route search function and a route guidance function, it is detected in advance what level of a straight path exists in which place before traveling, The above process may be performed only on a straight path suitable for the process. Thereby, for example, a short straight path or the like which can not continue the high speed traveling can be excluded in advance. That is, an optimal straight path on the route suitable for the above process can be selected, and the above process can be performed on the selected straight path. Therefore, the change of the tire outer diameter can be detected with high accuracy.

  Further, in such a configuration, the user is notified in advance or at the timing when the above processing is performed that the determination of whether or not there is a change in the tire outer diameter is to be performed and that the user is urged to go straight ahead. Good. As a result, the user can keep in mind straight running and can detect changes in the outer diameter of the tire with high accuracy.

(An example of a plot of the amount of change in orientation before and after the distance correction process)
Next, an example of a plot of the azimuth change amount coefficient before and after the distance correction process will be described with reference to FIG. FIG. 9 is an explanatory drawing showing an example of a plot of the azimuth change amount coefficient before and after the distance correction processing. In addition, although the plot of the azimuth | direction change amount coefficient at the time of turning is demonstrated here, since it becomes substantially the same plot also about the plot of the distance coefficient at the time of straight advance, description is abbreviate | omitted.

  In FIG. 9, the vertical axis represents the difference between the azimuth change amount coefficient and the azimuth change amount coefficient reference value. The horizontal axis shows time. The difference between the azimuth change amount coefficient plot value 901 and the azimuth change amount coefficient reference value before the detection of the tire outer diameter change is small. For example, when the tire is replaced with a new tire, as indicated by the plot points 902 of the direction variation coefficient, the number of threshold values S or more is increased. If the direction variation coefficient becomes equal to or greater than the threshold value S continuously a predetermined number of times (for example, T times), it is detected that the tire outer diameter has changed.

  And, after detecting the change of the tire outer diameter, by correcting the reference value of the amount of change in direction, specifically, for example, the average of the amount of change in direction coefficient which has become equal to or greater than the threshold S continuously for T times. The azimuth change coefficient is used as the reference value. As a result, after the change of the tire outer diameter is detected, as shown by each plot point 903, the difference from the azimuth change amount coefficient reference value becomes small. The azimuth change amount coefficient reference value is a value that is accumulated by averaging the azimuth change amount coefficients calculated as needed, and therefore, for example, it gradually decreases as the tire wears out.

  In this embodiment, assuming that the tire is replaced with a new tire, it is possible to detect a change in the case where the outer diameter of the tire becomes large when the direction variation coefficient becomes a threshold S or more continuously a predetermined number of times. However, it is also possible to detect a change in the case where the outer diameter of the tire becomes smaller, such as when there is a sudden wear of the tire due to sudden braking or the like. In this case, the change in tire outer diameter may be detected when the direction change amount coefficient becomes equal to or less than the threshold value -S continuously a predetermined number of times. In this case, the azimuth change amount coefficient reference value may be an average of the azimuth change amount coefficients that are successively less than or equal to the threshold value -S for T times.

(An example of notification that the tire has been replaced)
Here, with reference to FIG. 10, an example of the notification indicating that the tire has been replaced shown in step S714 will be described. FIG. 10 is an explanatory view showing an example of notification that the tire has been replaced. In FIG. 10, the display 412 of the navigation device 400 displays information that the tire has been replaced. Further, the same information from the speaker 409 may be output as voice.

  Further, the display 412 displays information indicating that the distance at the time of movement is corrected according to the tire outer diameter, as well as information indicating that the tire has been replaced. Further, more detailed information to the effect that the azimuth change amount coefficient reference value or the distance coefficient reference value is corrected, or information that the distance can be accurately measured by the correction may be output. As a result, after replacing the tire, the user can recognize that the navigation device 400 recognizes the tire replacement and accurately measure the distance, and the reliability of the user to the navigation device 400 can be improved. .

  Furthermore, the display 412 may output information indicating that the difference between each coefficient and each coefficient reference value has continuously exceeded the threshold a predetermined number of times consecutively. This allows the user to know what procedure the navigation device 400 has taken to correct each coefficient reference value.

  As described above, according to the determination apparatus, the determination method, the determination program, and the recording medium of the present invention, a change in tire outer diameter is detected in so-called city riding where movement at low speed frequently occurs Each reference value can be corrected. As a result, various reference values can be corrected quickly, and accurate distances can be measured.

  The determination method described in the present embodiment can be realized by executing a prepared program on a computer such as a personal computer or a workstation. This program is recorded on a computer-readable recording medium such as a hard disk, a flexible disk, a CD-ROM, an MO, a DVD, a memory card, etc., and is executed by being read from the recording medium by a computer. Also, this program may be a transmission medium that can be distributed via a network such as the Internet.

Reference Signs List 100 distance measurement apparatus 101 storage unit 102 signal acquisition unit 103 azimuth change amount acquisition unit 104 calculation unit 105 determination unit 106 correction unit 107 distance information acquisition unit 400 navigation device 412 display 414 GPS unit 415 various sensors 500 azimuth change amount table 600 distance information table

Claims (1)

Rotation amount acquisition means for acquiring the rotation amount of each of the plurality of moving wheels of the moving body;
An azimuth change amount acquisition unit that acquires an azimuth change amount of the moving object;
A determination unit that determines that the shape of the driving wheel has changed based on the rotation amount and the azimuth change amount;
A determination apparatus comprising:

Images