JP2010249578A - Device and method for deriving conversion factor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to derive a distance conversion factor according to a situation. <P>SOLUTION: A pre-processing part 40 sequentially averages GPS speeds contained in obtained positioning data for a predetermined period of time and sequentially measures the obtained number of pulses for the period. A temporary conversion factor deriving part 42 sequentially derives temporary factors for the conversion factor from the number of pulses to a moving distance based on the averaged GPS speed and the measured number of pulses. A filter processing part 46 sequentially performs statistical processing on the derived temporary factors. A correction control part 44 outputs the statistically processed temporary factor or the derived temporary factor as the conversion factor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a conversion coefficient derivation technique, and more particularly to a conversion coefficient derivation device and a conversion coefficient derivation method for deriving a conversion coefficient used when calculating a distance from an output signal of a speed sensor.

In a vehicular navigation device, generally, an optimum position is estimated by combining a position calculated from autonomous navigation and a position calculated from GPS (Global Positioning System). In autonomous navigation, the current position is calculated by updating the previous positioning position based on the speed pulse indicating the speed of the vehicle and the turning angular speed of the vehicle measured by the angular speed sensor. According to such a type of navigation device, the position of the vehicle can be derived by autonomous navigation even in tunnels, underground parking lots and valleys of high-rise buildings where it is difficult to receive radio waves from GPS satellites. The moving distance d [m] of the vehicle is derived by the following equation.
d = K · ΣP (1)
Here, K [m / pulse] is a distance conversion coefficient, and ΣP [pulse] is an integrated value of velocity pulses in the distance derivation period.

In order to accurately determine the moving distance, it is necessary to accurately determine the distance conversion coefficient. The distance conversion coefficient generally varies depending on a change in the weight of the vehicle and a change in the tire air pressure. Therefore, the distance conversion coefficient K is derived from the integrated value of the speed pulse and the distance measured by the GPS or the like by the following equation obtained by modifying the equation (1).
K = d / ΣP (2)
Or when deriving distance from the speed measured in GPS etc., Formula (2) is shown as follows.
K = v · Δt / ΣP (3)
Here, v [m / sec] is a speed measured from GPS or the like, and Δt [sec] is a sampling period of GPS or the like.

  For example, a method for correcting a distance correction coefficient related to a distance conversion coefficient based on a speed measured by GPS based on the Doppler effect has been proposed. Since the speed output from the GPS, that is, the moving distance per unit time is used, the distance conversion coefficient can be easily calculated by combining the unit time and the time width for counting the speed pulses (for example, Patent Document 1). . However, the accuracy of the speed output from the GPS varies depending on conditions such as the reception status of radio waves from GPS satellites and the traveling state including the traveling speed. Therefore, there is a possibility that the corrected distance conversion coefficient includes an error. is there. In order to solve this, a technique has been proposed in which a distance conversion coefficient is calculated only when the speed measured by GPS is equal to or greater than a certain value, and filtering such as averaging is performed on the distance conversion coefficient that has been calculated once. Yes. There, a plurality of averaging filters with different time constants are used to correct the distance conversion coefficient. At the initial stage of correction, a follower is improved by using a filter having a small time constant, and after follow, a filter having a large time constant is used to improve stability (for example, Patent Document 2).

Japanese Patent Laid-Open No. 5-18777 JP-A-8-14928

  Under such circumstances, when calculating the velocity v [m / sec] of the equation (3) from the velocity output from the GPS, the accuracy changes depending on the reception status of the radio wave from the GPS satellite. Even if the speed value is the same, the accuracy may be different. Generally, the higher the moving speed, the higher the accuracy of the speed measured by GPS. Therefore, in order to obtain sufficient accuracy, it is necessary to increase the speed lower limit value, which is a correction condition for the distance conversion coefficient, but the opportunity for correction decreases. On the other hand, if the speed lower limit value is decreased to increase the correction opportunity, sufficient accuracy cannot be obtained. In particular, in the initial stage of correction, if an averaging filter or the like having good followability is used for the calculated distance conversion coefficient, it becomes difficult to correct the distance conversion coefficient accurately. In order to improve the derivation accuracy of the movement distance, it is required to derive a distance conversion coefficient corresponding to the situation.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique for deriving a distance conversion coefficient corresponding to the situation.

  In order to solve the above-described problems, a conversion coefficient deriving device according to an aspect of the present invention sequentially acquires positioning data of an object positioned based on a signal from a GPS satellite and a pulse output from a speed sensor. A first derivation unit that sequentially averages the GPS speed included in the positioning data acquired by the acquisition unit over a predetermined period and sequentially measures the number of pulses acquired by the acquisition unit over a predetermined period; A second deriving unit that sequentially derives a temporary coefficient corresponding to a conversion coefficient from the number of pulses to a moving distance based on the GPS speed averaged in the first deriving unit and the number of pulses measured in the first deriving unit; A filter unit that statistically processes the temporary coefficient derived in the second deriving unit, and a follow-up stage that follows the initial stage, using the temporary coefficient derived in the second deriving unit as a transform coefficient in the initial stage. In, and a control unit for outputting a provisional coefficient of statistical processing in the filter section as a conversion coefficient. When the ratio between the temporary coefficient derived in the second deriving unit and the temporary coefficient derived in the past satisfies the condition depending on the GPS speed averaged in the first deriving unit, the control unit shifts from the initial stage to the following stage. To switch.

  According to this aspect, if the ratio between the derived temporary coefficient and the previously derived temporary coefficient does not satisfy the condition depending on the GPS speed, the statistical process is not performed, and if the condition is satisfied, the statistical process is performed. A distance conversion coefficient corresponding to the situation can be derived.

  The first derivation unit may set the predetermined period in the follow-up stage to be shorter than the predetermined period in the initial stage. In this case, since the predetermined period in the follow-up stage is shorter than the predetermined period in the initial stage, the influence of errors in the initial stage can be reduced, and the chance of correction in the follow-up stage can be increased.

  The control unit includes a measuring unit that measures the number of times that the ratio of the temporary coefficient derived by the second deriving unit and the temporary coefficient derived in the past is included in a predetermined range, and the number of times measured by the measuring unit is a predetermined number of times. And a determination unit that determines switching from the initial stage to the follow-up stage when it becomes larger. The determination unit may decrease the predetermined number of times as the average GPS speed in the first deriving unit increases. In this case, as the GPS speed increases, the predetermined number of times for determining switching from the initial stage to the follow-up stage is decreased, so that early switching can be performed.

  The measurement unit may narrow the predetermined range as the GPS speed averaged in the first deriving unit increases. In this case, since the predetermined range is narrowed as the GPS speed increases, the switching determination accuracy can be improved.

  In the initial stage, when the GPS speed newly averaged by the first deriving section becomes higher than the GPS speed averaged in the past, the second deriving section is a temporary unit corresponding to the newly averaged GPS speed. The conversion coefficient may be updated with the coefficient. In this case, if the newly averaged GPS speed is higher than the previously averaged GPS speed, the conversion coefficient is updated with a temporary coefficient corresponding to the newly averaged GPS speed. Can be improved.

  A filter part is good also considering the temporary coefficient in case the GPS speed averaged in the 1st deriving part is higher than a predetermined speed as an object of statistical processing. In this case, since the temporary coefficient when the averaged GPS speed is higher than the predetermined speed is the target of statistical processing, the accuracy of the temporary coefficient subjected to statistical processing can be improved.

  Another aspect of the present invention is a transform coefficient derivation method. This method includes an acquisition step of sequentially acquiring positioning data of an object measured based on a signal from a GPS satellite and a pulse output from a speed sensor, and a GPS speed included in the acquired positioning data. From the number of pulses to the travel distance based on the measurement step of sequentially averaging over a predetermined period and measuring the number of acquired pulses sequentially over a predetermined period, the averaged GPS speed, and the number of measured pulses A derivation step for sequentially deriving the temporary coefficient corresponding to the conversion coefficient, a statistical processing step for statistically processing the derived temporary coefficient, and a follow-up stage following the initial stage, with the temporary coefficient derived in the derivation step as the conversion coefficient in the initial stage. And an output step of outputting the temporary coefficient statistically processed in the statistical processing step as a conversion coefficient. The output step determines switching from the initial stage to the follow-up stage when the ratio between the derived temporary coefficient and the previously derived temporary coefficient satisfies the condition depending on the averaged GPS speed.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, a distance conversion coefficient according to the situation can be derived.

It is a figure which shows the structure of the autonomous navigation distance calculation apparatus which concerns on the Example of this invention. It is a figure which shows the structure of the distance conversion coefficient calculating part of FIG. It is a figure which shows the data structure of the table memorize | stored in the determination part of FIG. It is a flowchart which shows the derivation | leading-out procedure of the autonomous navigation distance by the autonomous navigation distance calculation apparatus of FIG.

  Before describing the present invention specifically, an outline will be given first. An embodiment of the present invention relates to an autonomous navigation distance calculation device that is mounted on a vehicle or the like and derives the travel distance of the vehicle by autonomous navigation. The autonomous navigation distance calculation device derives the movement distance using the distance conversion coefficient for the speed pulse from the speed sensor. As described above, in order to improve the derivation accuracy of the movement distance, it is necessary to improve the accuracy of the distance conversion coefficient. Therefore, it is required to derive a distance conversion coefficient with high accuracy even in a short time after startup, to derive a highly stable distance conversion coefficient, and to derive a distance conversion coefficient according to environmental changes. Is done. In order to cope with these, the autonomous navigation distance calculation apparatus according to the present embodiment executes the following processing.

  The autonomous navigation distance calculation device sets two types of periods, an initial stage after activation and a follow-up stage following the initial stage, and derives a distance conversion coefficient corresponding to each period. In the initial stage, the autonomous navigation distance calculation device derives a temporary distance conversion coefficient (hereinafter referred to as “provisional conversion coefficient”) using a GPS speed with high measurement accuracy. The autonomous navigation distance calculation device shortens the period until the distance conversion coefficient is derived by outputting the temporary conversion coefficient as the distance conversion coefficient. In addition, when the autonomous navigation distance calculation device derives a temporary conversion coefficient using a GPS speed with higher measurement accuracy, the distance calculation coefficient is updated by updating the distance conversion coefficient with the temporary conversion coefficient. Improve. On the other hand, at the following stage, the autonomous navigation distance calculation device derives a distance conversion coefficient by statistically processing a temporary conversion coefficient with high measurement accuracy, thereby obtaining a highly stable distance conversion coefficient while responding to environmental changes. To derive.

  Here, the switching timing from the initial stage to the follow-up stage differs depending on the reception status of signals from GPS satellites. That is, when the accuracy of the GPS speed is high and the variation of the temporary conversion coefficient is small, the accuracy of the distance conversion coefficient is improved by moving to the tracking stage early. On the other hand, if the variation of the temporary conversion coefficient is not so small, the distance conversion coefficient corresponding to the environmental change is derived by continuing the initial stage. The autonomous navigation distance calculation device sequentially derives the ratio between the temporary conversion coefficient and the past temporary conversion coefficient, and determines the completion of the initial stage when the ratio is included in a predetermined range over a predetermined number of times. Here, since the conditions such as the predetermined number of times are set according to the GPS speed, the above situation is reflected.

  FIG. 1 shows a configuration of an autonomous navigation distance calculation apparatus 100 according to an embodiment of the present invention. The autonomous navigation distance calculation device 100 includes a measurement unit 10, a distance conversion coefficient calculation unit 12, and an autonomous navigation distance conversion unit 14. The measurement unit 10 includes a GPS positioning unit 20, an effectiveness determination unit 22, and a speed pulse detection unit 24. Further, GPS positioning data 200, speed pulse signal 202, and distance conversion coefficient 204 are included as signals.

  The GPS positioning unit 20 receives a signal from a GPS satellite (not shown) and calculates GPS positioning data 200. The GPS positioning data 200 includes longitude and latitude, a GPS speed that is a moving speed of the vehicle, a GPS azimuth that is the azimuth of the vehicle, a GPS altitude that is the altitude of the vehicle, a PDOP (Position Division Precision), the number of captured satellites, and the like. Here, PDOP is an index of how the error of the GPS satellite position in the GPS positioning data 200 is reflected in the reception point position, and corresponds to the satellite error. Note that the GPS positioning data 200 may include values other than these. Further, since the GPS positioning data 200 may be calculated by a known technique, description thereof is omitted here. The GPS positioning unit 20 calculates the GPS positioning data 200 at every sampling interval, that is, periodically. The GPS positioning unit 20 sequentially outputs the GPS positioning data 200 to the validity determination unit 22.

  The validity determination unit 22 sequentially inputs the GPS positioning data 200 from the GPS positioning unit 20. The validity determination unit 22 determines the validity of each GPS positioning data 200 from the GPS positioning data 200. For example, when the value of PDOP is equal to or less than the threshold value, the validity determination unit 22 determines that the GPS speed corresponding to the value is effective. The validity determination unit 22 determines that the corresponding GPS speed is invalid when the above condition is not satisfied. More specifically, when the value of PDOP is 6 or less, the validity determination unit 22 represents the validity of the GPS speed with a flag. As a result of such processing, the validity determination unit 22 adds a flag indicating validity or invalidity to each value such as GPS speed included in the GPS positioning data 200 (hereinafter, the flag is added). The GPS positioning data 200 is also referred to as “GPS positioning data 200”). The validity determination unit 22 sequentially outputs the GPS positioning data 200 to the distance conversion coefficient calculation unit 12.

  The speed pulse detection unit 24 is connected to a speed sensor (not shown). The speed sensor is installed in the middle of the speedometer cable that rotates in response to the rotation of the drive shaft, and outputs a pulse signal that accompanies the rotation of the drive shaft. Output. The speed pulse detection unit 24 periodically detects the speed pulse signal 202 by counting the pulse signal output as the vehicle moves every predetermined period. The speed pulse detection unit 24 sequentially outputs the speed pulse signal 202 to the distance conversion coefficient calculation unit 12 and the autonomous navigation distance conversion unit 14.

  The distance conversion coefficient calculation unit 12 receives the GPS positioning data 200 from the validity determination unit 22 and the speed pulse signal 202 from the speed pulse detection unit 24. The distance conversion coefficient calculation unit 12 calculates a distance conversion coefficient 204 based on the GPS positioning data 200 and the speed pulse signal 202. Details of processing in the distance conversion coefficient calculation unit 12 will be described later. The distance conversion coefficient calculation unit 12 outputs the distance conversion coefficient 204 to the autonomous navigation distance conversion unit 14. The autonomous navigation distance converter 14 receives the speed pulse signal 202 from the speed pulse detector 24 and the distance conversion coefficient 204 from the distance conversion coefficient calculator 12. The autonomous navigation distance conversion unit 14 calculates the moving distance d of the vehicle by calculating the above-described equation (1) based on the speed pulse signal 202 and the distance conversion coefficient 204. Here, the autonomous navigation distance conversion unit 14 holds the input distance conversion coefficient 204.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 2 shows the configuration of the distance conversion coefficient calculation unit 12. The distance conversion coefficient calculation unit 12 includes a preprocessing unit 40, a temporary conversion coefficient derivation unit 42, a correction control unit 44, a filter processing unit 46, and a period management unit 50. The correction control unit 44 includes a temporary conversion coefficient comparison unit 52, a determination unit 54, and a temporary conversion coefficient storage unit 56. Further, a temporary conversion coefficient 210, an initial stage completion flag 212, and a derivation period signal 214 are included as signals.

  The pre-processing unit 40 includes GPS positioning data 200 output from the validity determination unit 22 (not shown), a speed pulse signal 202 output from the speed pulse detection unit 24 (not shown), and a derived period signal 214 output from the period management unit 50. Enter. The preprocessing unit 40 extracts the GPS speed from the GPS positioning data 200 determined to be valid by the validity determination unit 22 and integrates the GPS speed over the period indicated by the derivation period signal 214. The GPS speed average value (hereinafter referred to as “GPS speed average value”) is sequentially calculated. Here, in order to identify the GPS positioning data 200 determined to be valid by the validity determination unit 22, the flag added by the validity determination unit 22 is used. Further, the preprocessing unit 40 integrates the speed pulse signal 202 corresponding to a period in which the GPS positioning data 200 is valid. This corresponds to sequentially measuring the number of velocity pulses over the period indicated by the derived period signal 214. The preprocessing unit 40 outputs the GPS speed average value and the integrated value of the speed pulse signal 202 (hereinafter referred to as “integrated value”) to the temporary conversion coefficient deriving unit 42.

  The temporary conversion coefficient deriving unit 42 inputs the GPS speed average value and the integrated value from the preprocessing unit 40. When there is an integrated value of the speed pulse signal 202 in the period indicated by the derived period signal 214, the temporary conversion coefficient deriving unit 42 uses the above-described formula (3) based on the GPS speed average value and the integrated value. ) To derive temporary conversion coefficients 210 sequentially. Here, the GPS speed average value is substituted for v in Equation (3), and the integrated value is substituted for ΣP in Equation (3). The temporary conversion coefficient 210 corresponds to a temporary coefficient for the distance conversion coefficient from the integrated value to the moving distance, and is derived in the same manner as the distance conversion coefficient. Further, the provisional conversion coefficient deriving unit 42 assumes that the provisional conversion coefficient 210 is valid, and represents the validity by a flag.

  On the other hand, when the integrated value is 0, the temporary conversion coefficient deriving unit 42 does not derive the temporary conversion coefficient 210 and sets the validity flag to invalid. The temporary conversion coefficient deriving unit 42 adds the GPS speed average value and the validity flag to the derived temporary conversion coefficient 210 (hereinafter, the temporary conversion coefficient 210 to which these are added is also referred to as “temporary conversion coefficient 210”). The temporary conversion coefficient deriving unit 42 sequentially outputs the temporary conversion coefficient 210 to the correction control unit 44.

  The correction control unit 44 sequentially inputs the temporary conversion coefficient 210 from the temporary conversion coefficient deriving unit 42. The correction control unit 44 controls the entire distance conversion coefficient calculation unit 12 based on the processing results of the temporary conversion coefficient comparison unit 52 and the determination unit 54 or the processing result of the temporary conversion coefficient storage unit 56. In the initial stage, the correction control unit 44 outputs the temporary conversion coefficient 210 derived by the temporary conversion coefficient deriving unit 42 and stored in the temporary conversion coefficient storage unit 56 to the filter processing unit 46. On the other hand, the correction control unit 44 outputs the temporary conversion coefficient 210 derived by the temporary conversion coefficient deriving unit 42 to the filter processing unit 46 in the following stage following the initial stage. Although details will be described later, the filter processing unit 46 statistically processes the provisional conversion coefficient 210 having a GPS speed average value of a predetermined value or more, for example, 20 km / h or more.

The temporary conversion coefficient comparison unit 52 calculates a ratio between the temporary conversion coefficient 210 from the temporary conversion coefficient deriving unit 42 and the temporary conversion coefficient 210 input in the past in an initial stage. For example, the input temporary conversion coefficient 210 is indicated as K (n), and the temporary conversion coefficient 210 input in the past is indicated as K (n−1). When K (n) and K (n−1) are valid, the temporary conversion coefficient comparison unit 52 calculates the ratio R (n) by the following equation.
R (n) = K (n) / K (n-1) (4)
If K (n) or K (n−1) is invalid, the temporary conversion coefficient comparison unit 52 does not calculate the ratio R (n).

  The determination unit 54 inputs the ratio R (n) from the temporary conversion coefficient comparison unit 52. Further, the determination unit 54 stores a switching condition from the initial stage to the follow-up stage as a table. The determination unit 54 determines the switching from the initial stage to the follow-up stage when the ratio satisfies the switching condition. FIG. 3 shows the data structure of the table stored in the determination unit 54. As shown in the figure, a GPS speed average value column 300, a range condition column 302, and a frequency condition column 304 are included. The GPS speed average value column 300 indicates the GPS speed average value corresponding to the temporary conversion coefficient 210, and the range condition column 302 and the number of times condition column 304 indicate conditions for determining completion of the initial stage. Has been. The larger the GPS speed average value shown in the GPS speed average value field 300, the higher the accuracy of the temporary conversion coefficient 210. Therefore, the predetermined range in the range condition field 302 is narrowed. Further, as the GPS speed average value shown in the GPS speed average value column 300 increases, the predetermined number of times in the number of times condition column 304 is decreased. Returning to FIG.

  The determination unit 54 specifies the range in the range condition column 302 corresponding to the GPS speed average value column 300 and the number of times in the number condition column 304 from the GPS velocity average value of the temporary conversion coefficient 210. The determination unit 54 measures the number of times that the ratio R (n) is included in the predetermined range. Further, the determination unit 54 determines switching from the initial stage to the follow-up stage when the measured number of times becomes greater than the predetermined number. For example, when the GPS speed average value is 25 km / h and the ratio R (n) is in the range of 1−α2 to 1 + α2 for four consecutive times, the determination unit 54 determines the completion of the initial stage. The determination unit 54 notifies the filter processing unit 46 of the initial stage or the follow-up stage. Further, the determination unit 54 represents completion of the initial stage with a flag, and outputs it to the period management unit 50 as the initial stage completion flag 212. That is, the determination unit 54 determines switching from the initial stage to the follow-up stage when the ratio R (n) satisfies the condition depending on the GPS speed average value.

  The temporary conversion coefficient storage unit 56 compares the average GPS speed when the temporary conversion coefficient deriving unit 42 derives the temporary conversion coefficient 210 in the initial stage, and the new average GPS speed value is compared with the past GPS speed average value. If it becomes higher, a new GPS speed average value is stored. As described above, generally, the higher the moving speed, the higher the accuracy of the GPS speed, and the higher the accuracy of the provisional conversion coefficient 210. The temporary conversion coefficient storage unit 56 updates the temporary conversion coefficient 210 by storing the temporary conversion coefficient 210 when a new GPS speed average value is stored. Further, the temporary conversion coefficient storage unit 56 sequentially outputs the stored temporary conversion coefficients 210 in the initial stage.

  The period management unit 50 inputs the initial stage completion flag 212 from the determination unit 54. The period management unit 50 determines the integration period in the preprocessing unit 40 according to whether or not the initial stage completion flag 212 is input. The integration period is set so that the period in the follow-up stage is shorter than the period in the initial stage. This is to improve the calculation accuracy of Equation (3) in the initial stage, and to increase the chance of correction in the tracking stage to improve the tracking performance. For example, the integration period is set to 5 seconds in the initial stage, and the integration period is set to 3 seconds in the following stage. The period management unit 50 outputs the determined integration period to the preprocessing unit 40 as the derived period signal 214.

  The filter processing unit 46 receives the temporary conversion coefficient 210 from the correction control unit 44. Further, the filter processing unit 46 is notified of the initial stage or the follow-up stage from the determination unit 54. When notified of the initial stage, the filter processing unit 46 outputs the input temporary conversion coefficient 210 as it is as the distance conversion coefficient 204. On the other hand, when notified of the follow-up stage, the filter processing unit 46 sequentially executes statistical processing on the temporary conversion coefficient 210. The filter processing unit 46 is configured to include, for example, an IIR (Infinite Impulse Response) filter, and the IIR filter constitutes a low-pass filter. As a result, the GPS speed error in equation (3) is absorbed. The filter processing unit 46 outputs the statistically processed temporary conversion coefficient 210 as the distance conversion coefficient 204. This is because the correction control unit 44 uses the temporary conversion coefficient 210 derived by the temporary conversion coefficient deriving unit 42 as the distance conversion coefficient 204 in the initial stage, and the temporary conversion coefficient 210 statistically processed by the filter processing unit 46 in the following stage. Is equivalent to the distance conversion coefficient 204. Note that the filter processing unit 46 may use the temporary conversion coefficient 210 when the GPS speed average value is higher than a predetermined speed as a target for statistical processing.

  The operation of the autonomous navigation distance calculation apparatus 100 having the above configuration will be described. FIG. 4 is a flowchart showing a procedure for deriving the autonomous navigation distance by the autonomous navigation distance calculation device 100. The autonomous navigation distance calculation device 100 derives the autonomous navigation distance at the timing when the speed pulse detection unit 24 outputs the speed pulse signal 202. When the GPS positioning data 200 measured by the GPS positioning unit 20 is input, the validity determining unit 22 determines the validity (S10). If the GPS positioning data 200 is not input or if the GPS positioning data 200 is not valid (N in S10), the process skips to step 32. When the GPS positioning data 200 is valid (Y in S10), the provisional conversion coefficient deriving unit 42 calculates the GPS speed average value validated in the derivation period indicated in the derivation period signal 214 determined by the period management unit 50, and The temporary conversion coefficient 210 is derived from the corresponding velocity pulse signal 202 (S12).

  If the temporary conversion coefficient 210 is not valid (N in S14), the process skips to step 32. In the correction control unit 44, if the temporary conversion coefficient 210 is valid (Y in S14) and in the initial stage (Y in S16), the GPS speed average value of the input temporary conversion coefficient 210 and the temporary conversion coefficient storage unit 56 Is compared with the maximum GPS speed average value stored in (S18). If the input GPS speed average value is larger than the maximum GPS speed average value stored in the temporary conversion coefficient storage unit 56 (Y in S18), the temporary conversion coefficient storage unit 56 sets the maximum GPS speed average value. Update (S20). Further, the correction control unit 44 outputs the input temporary conversion coefficient 210 (S22). Furthermore, the autonomous navigation distance conversion unit 14 updates the stored distance conversion coefficient 204 to the input distance conversion coefficient 204.

  If the input GPS speed average value is not larger than the maximum GPS speed average value stored in the temporary conversion coefficient storage unit 56 (N in S18), Step 20 and Step 22 are skipped. If the processing result of the temporary conversion coefficient comparison unit 52 satisfies the initial stage completion condition (Y in S24), the correction control unit 44 determines the completion of the initial stage (S26) and enables the initial stage completion flag 212. To the period management unit 50. If the initial stage completion condition is not satisfied (N in S24), the process skips to step 32.

  If the GPS speed average value of the input temporary conversion coefficient 210 is not less than a predetermined value (Y in S28), the correction control unit 44 is not in the initial stage (N in S16), that is, in the following stage, that is, the temporary conversion coefficient 210. Is output to the filter processing unit 46. The filter processing unit 46 performs a filtering process on the input temporary conversion coefficient 210 (S30), and outputs the filtered temporary conversion coefficient 210. The autonomous navigation distance conversion unit 14 updates the stored distance conversion coefficient 204 to the input distance conversion coefficient 204. If the average GPS speed value of the input temporary conversion coefficient 210 is not greater than the predetermined value (N in S28), the correction control unit 44 is skipped to step 32. The autonomous navigation distance conversion unit 14 converts the speed pulse signal 202 input from the speed pulse detection unit 24 into an autonomous navigation distance using the stored distance conversion coefficient 204 (S32).

  According to the embodiment of the present invention, statistical processing is not executed unless the ratio between the temporary conversion coefficient and the temporary conversion coefficient derived in the past satisfies a condition depending on the GPS speed, and statistical processing is performed if the condition is satisfied. Since it is executed, the presence or absence of statistical processing can be determined according to whether or not the temporary conversion coefficient is stable. If statistical processing is not executed, the distance conversion coefficient derivation period can be shortened. In addition, if the statistical process is executed, the accuracy of the distance conversion coefficient can be improved. In addition, since the switching from the state in which the statistical processing is not performed to the state in which the statistical processing is performed is performed, a distance conversion coefficient corresponding to the situation can be derived. In addition, since the integration period in the follow-up stage is shorter than the integration period in the initial stage, the influence of errors in the initial stage can be reduced, and the chances of correction in the follow-up stage can be increased.

  Further, in the initial stage, if the GPS positioning data is valid and 0 or more, the distance conversion coefficient is always updated based on the GPS speed average value during the provisional conversion coefficient derivation period, so the correction opportunities can be increased. In addition, since the correction opportunities are increased, the followability can be improved. Moreover, since the predetermined number of times for determining switching from the initial stage to the follow-up stage decreases as the GPS speed average value increases, early switching can be performed. In addition, the higher the GPS speed average value, the narrower the predetermined range, so that the processing accuracy can be improved. Further, the GPS speed is more accurate as the moving speed is higher, and the distance conversion coefficient is updated with a temporary conversion coefficient having a larger GPS speed average value in the derivation period, so that the accuracy can be improved. Also, if the new GPS speed average value becomes higher than the past GPS speed average value, the distance conversion coefficient is updated with the temporary conversion coefficient corresponding to the new GPS speed average value, so the accuracy of the distance conversion coefficient is improved. it can.

  In addition, since the initial stage completion condition corresponding to the GPS speed average value in the derivation period of the temporary conversion coefficient is provided, an accurate initial value can be given in the follow-up stage filter processing. In addition, since an accurate initial value is given in the filtering process at the follow-up stage, the accuracy of deriving the distance conversion coefficient can be improved. In addition, since the temporary conversion coefficient when the GPS speed average value is higher than the predetermined speed is the target of statistical processing, the accuracy of the statistically processed temporary conversion coefficient can be improved.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the determination unit 54 stores in advance conditions such that the predetermined range in the range condition column 302 becomes narrower as the GPS velocity average value in the GPS velocity average value column 300 becomes higher. However, the present invention is not limited to this. For example, even if the GPS speed average value in the GPS speed average value column 300 is high, the predetermined range in the range condition column 302 may be constant. At that time, the predetermined number of times in the number-of-times condition column 304 changes depending on the GPS speed average value. That is, it is only necessary to define a relationship such that the higher the GPS speed average value, the easier the switching from the initial stage to the following stage. According to this modification, switching can be performed earlier.

  In the embodiment of the present invention, the validity determination unit 22 uses PDOP to determine the validity of the GPS positioning data 200. However, the present invention is not limited to this. For example, the validity determination unit 22 may use GDOP (Geometric Dilution Of Precision), HDOP (Horizontal Division Of Precision), or a combination thereof. According to this modification, various parameters can be used for determination.

  In the embodiment of the present invention, the filter processing unit 46 is formed to include an IIR filter. However, the present invention is not limited to this. For example, the filter processing unit 46 may be formed to include an FIR (Finite Impulse Response) filter. According to this modification, the degree of freedom of the filter configuration can be improved.

  DESCRIPTION OF SYMBOLS 10 Measurement part, 12 Distance conversion coefficient calculation part, 14 Autonomous navigation distance conversion part, 20 GPS positioning part, 22 Effectiveness determination part, 24 Speed pulse detection part, 40 Pre-processing part, 42 Temporary conversion coefficient derivation part, 44 Correction control Unit, 46 filter processing unit, 50 period management unit, 52 temporary conversion coefficient comparison unit, 54 determination unit, 56 temporary conversion coefficient storage unit, 100 autonomous navigation distance calculation device.

Claims (7)

An acquisition unit for sequentially acquiring positioning data of an object measured based on a signal from a GPS satellite and a pulse output from a speed sensor;
A first deriving unit that sequentially averages the GPS speed included in the positioning data acquired in the acquisition unit over a predetermined period, and sequentially measures the number of pulses acquired in the acquisition unit over the predetermined period;
A second deriving unit that sequentially derives a temporary coefficient corresponding to a conversion coefficient from the number of pulses to a moving distance based on the GPS speed averaged in the first deriving unit and the number of pulses measured in the first deriving unit. When,
A filter unit for statistically processing the temporary coefficient derived in the second deriving unit;
A control unit that outputs the temporary coefficient derived in the second derivation unit as a conversion coefficient in the initial stage, and outputs the temporary coefficient statistically processed in the filter unit in the follow-up stage following the initial stage;
The control unit starts from the initial stage when the ratio of the temporary coefficient derived in the second deriving unit and the temporary coefficient derived in the past satisfies a condition depending on the GPS speed averaged in the first deriving unit. A conversion coefficient deriving device characterized by determining switching to a follow-up stage.   2. The transform coefficient deriving device according to claim 1, wherein the first derivation unit sets the predetermined period in the follow-up stage to be shorter than the predetermined period in the initial stage. The controller is
A measurement unit that measures the number of times that the ratio between the temporary coefficient derived in the second deriving unit and the temporary coefficient derived in the past is included in a predetermined range;
A determination unit that determines switching from the initial stage to the follow-up stage when the number of times measured in the measurement unit is greater than a predetermined number of times,
The conversion coefficient deriving device according to claim 1, wherein the determining unit decreases the predetermined number of times as the GPS speed averaged in the first deriving unit increases.   The conversion coefficient deriving device according to claim 3, wherein the measurement unit narrows the predetermined range as the GPS speed averaged in the first deriving unit increases.   The second deriving unit corresponds to the newly averaged GPS speed when the GPS speed newly averaged by the first deriving unit is higher than the previously averaged GPS speed in the initial stage. 5. The conversion coefficient deriving device according to claim 1, wherein the conversion coefficient is updated with the provisional coefficient.   5. The conversion according to claim 1, wherein the filter unit uses a temporary coefficient when the GPS speed averaged in the first deriving unit is higher than a predetermined speed as a target of statistical processing. 6. Coefficient derivation device. An acquisition step of sequentially acquiring positioning data of an object measured based on a signal from a GPS satellite and a pulse output from a speed sensor;
A measurement step of sequentially averaging the GPS speed included in the acquired positioning data over a predetermined period and sequentially measuring the number of acquired pulses over the predetermined period;
A derivation step for sequentially deriving a temporary coefficient corresponding to a conversion coefficient from the number of pulses to a moving distance based on the averaged GPS speed and the number of measured pulses;
A statistical processing step for statistically processing the derived temporary coefficient;
In the initial stage, the provisional coefficient derived in the derivation step is used as a conversion coefficient, and in the follow-up stage following the initial stage, an output step is provided that outputs the temporary coefficient statistically processed in the statistical processing step as a conversion coefficient,
In the output step, when the ratio of the derived temporary coefficient and the previously derived temporary coefficient satisfies a condition depending on the averaged GPS speed, the switching from the initial stage to the tracking stage is determined. Conversion coefficient derivation method.

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