JP6699355B2 - Angular velocity sensor correction device and angular velocity sensor correction method - Google Patents

Description

  The present invention relates to an angular velocity sensor correction technique, and more particularly to an angular velocity sensor correction device and an angular velocity sensor correction method for correcting an output of an angular velocity sensor.

In a vehicle 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 last measured position based on the speed pulse indicating the speed of the vehicle and the turning angular velocity of the vehicle measured by the angular velocity sensor. According to the navigation device of such a system, it is possible to derive the vehicle position by autonomous navigation even in a tunnel where it is difficult to receive radio waves from GPS satellites, an underground parking lot, or a valley of a high-rise building. The angular velocity ω due to the turning of the vehicle is derived by the following equation.
ω=(Vout−Voffset)/S (1)
Here, Vout is an output voltage of the angular velocity sensor, Voffset is an offset value of the angular velocity sensor, and S (mV/deg/sec) is a sensitivity coefficient of the angular velocity sensor (for example, Patent Document 1).

JP, 2010-101810, A

  In order to accurately obtain the angular velocity, it is necessary to accurately obtain the offset value of the angular velocity sensor and the sensitivity coefficient. The sensitivity coefficient of the angular velocity sensor generally differs depending on the individual difference of the angular velocity sensor and the mounting angle of the angular velocity sensor on the vehicle. Further, the offset value may change due to the temperature change. That is, the offset value is affected by the temperature change due to heat generation of the board or the like used in the vehicular navigation device or heat generation of the vehicle engine or the like when the vehicular navigation device is mounted on the dashboard or the like of the vehicle. When the offset value changes in this way, the offset value should be obtained so as to follow it. However, when the offset value changes abruptly within the normal change range, it may take time to follow the true offset value. For example, the output of the angular velocity sensor includes white noise, but other than that, there is an irregular stepwise shift.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique for suppressing a decrease in the derivation accuracy of the angular velocity even when the offset value of the angular velocity sensor changes rapidly.

In order to solve the above problems, an angular velocity sensor correction device according to an aspect of the present invention provides positioning data of an object that is located based on a signal from a GPS satellite, and angular velocity of the object that is output from the angular velocity sensor. An offset value deriving unit that sequentially derives a temporary offset value of the angular velocity sensor by using the positioning data and the angular velocity acquired by the obtaining unit, and the angular velocity sensor sequentially derived by the offset value deriving unit. And an offset value filter processing unit for deriving an offset value of the angular velocity sensor for correcting the angular velocity output from the angular velocity sensor by executing statistical processing on the temporary offset value. The offset value filter processing unit sets, for statistical processing, a forgetting factor that increases as the slope of the change in the temporary offset value of the angular velocity sensor with time increases , and the offset value filter processing unit determines the angular velocity with respect to time elapsed. When the absolute value of the change in the temporary offset value of the angular velocity sensor is equal to or greater than the threshold value in the second period shorter than the first period for deriving the slope of the change in the temporary offset value of the sensor, the forgetting factor To zero.

Another aspect of the present invention is an angular velocity sensor correction method. This method uses a step of acquiring positioning data of an object positioned based on a signal from a GPS satellite and an angular velocity of the object output from an angular velocity sensor, and the acquired positioning data and the angular velocity. The step of sequentially deriving a temporary offset value of the angular velocity sensor, and a statistical process for sequentially deriving the temporary offset value of the angular velocity sensor to correct the angular velocity output from the angular velocity sensor. Deriving an offset value of the angular velocity sensor. In the step of deriving the offset value of the angular velocity sensor, the forgetting coefficient that becomes larger as the slope of the change in the temporary offset value of the angular velocity sensor with time elapses is set for statistical processing, and the offset value of the angular velocity sensor is derived. In the second period, which is shorter than the first period for deriving the slope of the change in the temporary offset value of the angular velocity sensor over time, the absolute value of the change in the temporary offset value of the angular velocity sensor is a threshold value. If this is the case, the forgetting factor is set to zero .

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

  According to the present invention, even if the offset value of the angular velocity sensor changes abruptly, it is possible to suppress a decrease in the accuracy of deriving the angular velocity.

It is a figure which shows an example of the output signal from the angular velocity sensor which concerns on the Example of this invention. It is a figure which shows the structure of the angular velocity calculation apparatus which concerns on the Example of this invention. It is a figure which shows the structure of the offset value calculation part of FIG. It is a figure which shows the structure of the offset value correction|amendment part of FIG. It is a figure which shows the structure of the offset value filter process part of FIG. It is a figure which shows the data structure of the table memorize|stored in the forgetting factor control part of FIG. It is a figure which shows the outline of a process by the offset value correction|amendment part of FIG. 3 is a flowchart showing a procedure of deriving an offset value by the angular velocity calculation device of FIG.

  Before specifically explaining the present invention, an outline will be given. The embodiment of the present invention relates to an angular velocity calculation device which is mounted on a vehicle or the like and derives an angular velocity due to turning of the vehicle. The angular velocity calculation device derives the angular velocity using the offset value and the sensitivity coefficient for the output voltage from the angular velocity sensor. As described above, the offset value of the angular velocity sensor is affected by the temperature fluctuation. Further, the error of the offset value affects the calculation accuracy of the sensitivity coefficient. Conventionally, the offset value of the angular velocity sensor is corrected using the output voltage from the angular velocity sensor when the vehicle is stopped or the vehicle travels straight when the angular velocity is “0”. The running state of the vehicle is determined from the combination of the output values of the vehicle speed sensor, the acceleration sensor, and the angular velocity sensor, but it may be difficult to accurately determine the running state. For example, when the vehicle is moving at a slow speed, the output of the vehicle speed sensor during the predetermined period is “0”, and the output changes of the acceleration sensor and the angular velocity sensor are very small, so it may be determined that the vehicle is stopped. When the offset value of the angular velocity sensor is corrected, a correction error may be included.

  As described above, when the offset value changes abruptly within the normal change range, it may take time to follow the true offset value. For example, although the output of the angular velocity sensor contains white noise, there may be other irregular stepwise shifts. If the output value changes in steps, it becomes difficult to follow the true offset value by averaging processing or the like, and it takes time to correct the value. In order to improve the derivation accuracy of the angular velocity even in a situation where there is an irregular stepwise shift, it is required to derive the offset value of the angular velocity sensor with high accuracy in a short period of time. In order to deal with this, the angular velocity calculation device according to the present embodiment executes the following processing.

  The angular velocity calculation device inputs an output voltage from an angular velocity sensor mounted on the vehicle and inputs positioning data from a GPS receiver mounted on the vehicle. Here, the output voltage from the angular velocity sensor corresponds to the angular velocity of the vehicle. Further, the positioning data includes the direction of the vehicle, the speed of the vehicle, the altitude of the vehicle, and the like. The angular velocity calculation device estimates the traveling state of the vehicle based on the positioning data and the output voltage. As the traveling state, for example, any one of a stopped state, a straight traveling state, and a non-straight traveling state is specified. Further, the angular velocity calculation device sequentially derives the temporary offset value by a derivation method according to the traveling state. Further, the angular velocity calculation device performs a filtering process using a low-pass filter on the temporary offset values that are sequentially derived. Here, the angular velocity calculation device controls the forgetting factor such that the influence of the current provisional offset value increases as the inclination of the change in the provisional offset value over time increases. As a result, the filtering process is executed so as to follow the stepwise change of the temporary offset value. The result of the filtering process is the offset value.

  FIG. 1 shows an example of an output signal from an angular velocity sensor according to an embodiment of the present invention. The horizontal axis represents time and the vertical axis represents the offset value of the angular velocity sensor. As a whole from 0 [sec] to 200 [sec], the offset value gradually increases under the influence of temperature change. However, a step-like shift occurs in the offset value from around 80 [sec] to around 130 [sec].

  FIG. 2 shows the configuration of the angular velocity calculation device 100 according to the embodiment of the present invention. The angular velocity calculation device 100 includes a measurement unit 10, a parameter calculation unit 12, an angular velocity conversion unit 14, and a control unit 16. Further, the measurement unit 10 includes a GPS positioning unit 20, a validity determination unit 22, and an angular velocity sensor 24, and the parameter calculation unit 12 includes an offset value calculation unit 26 and a sensitivity coefficient calculation unit 28. Furthermore, the GPS positioning data 200, the output signal 202, the offset value 204, and the sensitivity coefficient 206 are included as signals.

  The GPS positioning unit 20 receives signals from GPS satellites (not shown) and calculates GPS positioning data 200. The GPS positioning data 200 includes latitude and longitude, GPS altitude that is the altitude of the vehicle, GPS speed that is the moving speed, GPS direction that is the direction of the vehicle, PDOP (Position Dilution 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 position of the receiving point, and corresponds to the positioning error. The GPS positioning data 200 may include values other than these. Further, the calculation of the GPS positioning data 200 may be performed by a known technique, and thus the description thereof is omitted here. Further, 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 determining 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 PDOP value is less than or equal to the first threshold value and the GPS speed is greater than or equal to the second threshold value, the validity determination unit 22 determines that the GPS azimuth corresponding to them is valid. judge. Further, the validity determining unit 22 determines that the corresponding GPS bearing is invalid when the above conditions are not satisfied. This is because, generally, when the value of PDOP is large or the GPS speed is low, the accuracy of the GPS bearing tends to be low. More specifically, when the PDOP value is 6 or less and the GPS speed is 20 km/h or more, the validity determination unit 22 represents the validity of the GPS bearing by a flag.

  Further, the validity determination unit 22 determines that the GPS speed is valid when the GPS speed is equal to or higher than the third threshold value. Here, the third threshold may be the same as the second threshold. As a result of such processing, the validity determination unit 22 adds a flag indicating validity or invalidity to each value such as the GPS direction 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 offset value calculation unit 26 and the sensitivity coefficient calculation unit 28.

  The angular velocity sensor 24 corresponds to, for example, a gyro device such as a vibration gyro, and detects a change in the traveling direction of the vehicle as a relative angle change of the vehicle. That is, the angular velocity sensor 24 detects the turning angular velocity of the vehicle. The detected angular velocity is output as an analog signal of 0V to 5V, for example. At that time, the positive angular velocity corresponding to the clockwise turning is output as a deviation voltage from 2.5V to the 5V side, and the negative angular velocity corresponding to the counterclockwise turning is output from the 2.5V to the 0V side. It is output as a deviation voltage. Further, 2.5V is an offset value of the angular velocity, that is, a zero point, and drifts under the influence of temperature and the like.

  The sensitivity coefficient (mV/deg/sec), which is the deviation of the angular velocity from 2.5 V, is set as a predetermined value that falls within the allowable error in the horizontal state. The cause of this allowable error is the individual difference of the gyro device, the secular change, the influence of temperature, and the like. The voltage value of the gyro device is AD-converted by an AD (Analog to Digital) converter (not shown) at a sampling interval of 100 msec, for example, and the resulting digital signal is output. The digital signal corresponds to the aforementioned output voltage, and in the following the term output signal 202 will be used. Note that a known technique may be used as the gyro device, and a description thereof will be omitted here. The angular velocity sensor 24 outputs the output signal 202 to the angular velocity converter 14, the offset value calculator 26, and the sensitivity coefficient calculator 28. This output signal 202 corresponds to the angular velocity acquired at the offset value 204. Here, since the offset value calculation unit 26 and the sensitivity coefficient calculation unit 28 acquire the GPS positioning data 200 from the validity determination unit 22 and the output signal 202 from the angular velocity sensor 24, these are “acquisition unit”. It can be said that there is.

  The offset value calculator 26 receives the GPS positioning data 200 from the validity determiner 22 and the output signal 202 from the angular velocity sensor 24. The offset value calculator 26 also receives the sensitivity coefficient 206 from the sensitivity coefficient calculator 28. The offset value calculator 26 calculates an offset value of the angular velocity sensor 24 (hereinafter referred to as “offset value 204”) based on the GPS positioning data 200, the output signal 202, and the sensitivity coefficient 206. The details of the processing in the offset value calculator 26 will be described later. The offset value calculation unit 26 outputs the offset value 204 to the sensitivity coefficient calculation unit 28 and the angular velocity conversion unit 14.

  The sensitivity coefficient calculation unit 28 inputs the GPS positioning data 200 from the validity determination unit 22 and the output signal 202 from the angular velocity sensor 24. The sensitivity coefficient calculation unit 28 also receives the offset value 204 from the offset value calculation unit 26. The sensitivity coefficient calculation unit 28 uses the GPS positioning data 200, the output signal 202, and the offset value 204 input over a predetermined period of time, for example, 10 seconds, to detect the sensitivity coefficient of the angular velocity sensor 24 (hereinafter, the “sensitivity coefficient 206” described above ")) is calculated. Note that a publicly known technique may be used to calculate the sensitivity coefficient, and thus the description thereof is omitted here. The sensitivity coefficient calculation unit 28 outputs the sensitivity coefficient 206 to the offset value calculation unit 26 and the angular velocity conversion unit 14.

  The angular velocity conversion unit 14 inputs the output signal 202 from the angular velocity sensor 24, the offset value 204 from the offset value calculation unit 26, and the sensitivity coefficient 206 from the sensitivity coefficient calculation unit 28. The angular velocity conversion unit 14 calculates the angular velocity ω of the vehicle by calculating the above equation (1) based on the output signal 202, the offset value 204, and the sensitivity coefficient 206. The angular velocity conversion unit 14 outputs the angular velocity ω. The control unit 16 controls the overall operation of the angular velocity calculation device 100.

  In terms of hardware, this configuration can be realized by a CPU, memory, or other LSI of an arbitrary computer, and in terms of software, it can be realized by a program loaded in the memory, but here, it is realized by the cooperation thereof. It depicts the functional blocks that will be used. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by only hardware, only software, or a combination thereof.

  FIG. 3 shows the configuration of the offset value calculator 26. The offset value calculation unit 26 includes a state estimation unit 30, a state-based offset value derivation unit 32, and an offset value correction unit 34. The state estimating unit 30 includes a stop estimating unit 40, a straight traveling estimating unit 42, and a non-straight traveling estimating unit 44. The state-based offset value deriving unit 32 includes a stop offset value deriving unit 46 and a straight traveling offset value. A derivation unit 48 and a non-straight running offset value derivation unit 50 are included. Further, a temporary offset value 210 is included as a signal.

  The state estimation unit 30 inputs the GPS positioning data 200 and the output signal 202. The state estimating unit 30 estimates the traveling state of the vehicle in the stop estimating unit 40, the straight traveling estimating unit 42, and the non-straight traveling estimating unit 44. Here, as the traveling state of the vehicle, it is estimated whether the vehicle is in a stopped or straight traveling state or the remaining state, that is, a non-straight traveling state.

  The stop estimation unit 40 acquires the GPS positioning data 200 determined to be valid by the validity determination unit 22 (not shown). In addition, the stop estimation unit 40 extracts the GPS speed from the GPS positioning data 200 and confirms whether the GPS speed is “0”. On the other hand, the stop estimation unit 40 calculates the variance value of the output signal 202 within the predetermined period and compares the variance value with the fourth threshold value. The stop estimating unit 40 determines that the vehicle is in the stop state when the GPS speed is 0 and the variance value is smaller than the fourth threshold value. As described above, when the GPS speed is low, the accuracy tends to be low, but the stop estimating unit 40 determines to stop by using the variance value of the output signal 202 together. Here, the predetermined period is, for example, 1 sec which is a sampling interval of GPS speed. When the variance value of the output signal 202 is small in a predetermined period, it is estimated that the vehicle is in a stable state without shaking. When it is determined that the vehicle is not in the stopped state, the stop estimation unit 40 outputs a message to that effect to the non-straight running estimation unit 44.

  The straight-ahead traveling estimation unit 42 acquires the GPS positioning data 200 that is determined to be valid by the validity determination unit 22 (not shown). Further, the straight traveling estimation unit 42 extracts the GPS azimuth from the GPS positioning data 200 and derives a change in the GPS azimuth over a predetermined period (hereinafter, referred to as “GPS azimuth change”). Further, the straight-ahead traveling estimation unit 42 confirms whether the GPS azimuth change is “0”. Further, the straight traveling estimation unit 42 calculates the variance value of the output signal 202 in the predetermined period and compares the variance value with the fifth threshold value. The fifth threshold value may be the same as the fourth threshold value. Here, the predetermined period is set to, for example, a period in which the change in GPS azimuth is continuously zero.

  The straight-ahead traveling estimation unit 42 determines that the vehicle is in a straight-ahead traveling state when the change in the GPS bearing is 0 and the variance value is smaller than the fifth threshold value. When the variance value of the output signal 202 is small in a predetermined period, it is estimated that the vehicle is in a straight traveling state in which there is no influence such as subtle meandering. Although it depends on the driving situation of the driver and the shape of the road, for example, in a city area or the like, the detection frequency of the straight traveling state is generally lower than the determination of the stopped state by the stop estimation unit 40, and the period is about several seconds. is there. When the straight traveling estimation unit 42 determines that the vehicle is not in the straight traveling state, it outputs a message to that effect to the non-straight traveling estimation unit 44. When the non-straight running estimation unit 44 inputs from the stop estimation unit 40 that the vehicle is not in the stopped state and the straight traveling estimation unit 42 inputs that the vehicle is not in the straight traveling state, the vehicle is in the non-straight traveling state. To determine.

  The state-based offset value derivation unit 32 inputs the GPS positioning data 200, the output signal 202, and the sensitivity coefficient 206. The state-specific offset value derivation unit 32 sequentially derives the temporary offset value 210 of the angular velocity sensor 24 according to the running state of the vehicle estimated by the state estimation unit 30. Here, when the stop estimation unit 40 determines that the vehicle is in the stopped state, the stop-time offset value derivation unit 46 sequentially derives the temporary offset value 210 based on the output signal 202. Further, when the straight running estimation unit 42 determines that the vehicle is in the straight running state, the straight running offset value deriving unit 48 sequentially derives the temporary offset value 210 based on the output signal 202.

  When the straight running offset value deriving unit 48 determines that the vehicle is in the non-straight running state, the non-straight running offset value deriving unit 50 uses the temporary positioning value based on the GPS positioning data 200, the output signal 202, and the sensitivity coefficient 206. 210 is sequentially derived. That is, the stop offset value derivation unit 46 to the non-straight running travel offset value derivation unit 50 change the combination of the GPS positioning data 200, the output signal 202, and the sensitivity coefficient 206 according to the traveling state of the vehicle while changing the temporary offset value. 210 is derived. Therefore, it can be said that the state-based offset value derivation unit 32 including the stop-time offset value derivation unit 46, the straight traveling travel offset value derivation unit 48, and the non-straight travel traveling offset value derivation unit 50 is an offset value derivation unit.

  When it is determined that the vehicle is in the stopped state, the stop-time offset value derivation unit 46 sequentially derives the temporary offset value 210 of the angular velocity sensor 24 based on the output signal 202. Specifically, the stop offset value derivation unit 46 calculates that the average value of the output signal 202 is the temporary offset value 210 by utilizing the fact that the turning angular velocity of the vehicle becomes “0” at the stop. When it is determined that the vehicle is in a straight traveling state, the straight traveling offset value deriving unit 48 sequentially derives the temporary offset value 210 of the angular velocity sensor 24 based on the output signal 202. More specifically, since the turning angular velocity of the vehicle is 0, the straight traveling traveling offset value derivation unit 48 calculates the average value of the output signal 202 as the temporary offset value 210.

When it is determined that the vehicle is in a non-straight running state, the non-straight running offset value deriving unit 50 uses, for example, the GPS azimuth based on the GPS azimuth, the output signal 202, and the sensitivity coefficient 206 in the GPS positioning data 200. The temporary offset value 210 in the sampling interval of is sequentially derived. The temporary offset value 210 is derived as follows.
Goffset=1/n·ΣGout−Δθ·Gsensitivity (2)
Here, n is the number of samples of the output signal 202 in the GPS azimuth sampling interval, and ΣGout (mV) is the total value of the output signal 202 in the GPS azimuth sampling interval. Further, Δθ(deg) is the GPS azimuth change amount, and Gsensitivity (mV/deg/sec) is the sensitivity coefficient 206.

  The sensitivity coefficient 206 is normally input from a sensitivity coefficient calculation unit 28 (not shown), but it is possible that the sensitivity coefficient 206 has not been calculated in a state immediately after the angular velocity calculation device 100 is started. In such a case, the non-straight running offset value derivation unit 50 uses the sensitivity coefficient 206 determined by the specifications of a gyro device (not shown) as an initial value. The non-straight running offset value derivation unit 50 may store the sensitivity coefficient 206 from the sensitivity coefficient calculation unit 28 at the end of the previous travel and use it as an initial value.

  The offset value correction unit 34 receives the temporary offset value 210 sequentially derived by the state-based offset value derivation unit 32. The offset value correcting unit 34 derives the offset value 204 of the angular velocity sensor 24 by detecting a change in the temporary offset value 210 with respect to time and performing statistical processing based on the detection result. Hereinafter, the processing in the offset value correction unit 34 will be described with reference to FIG.

  FIG. 4 shows the configuration of the offset value correction unit 34. The offset value correction unit 34 includes an average value calculation unit 60, a difference absolute value calculation unit 62, a tilt absolute value calculation unit 64, and an offset value filter processing unit 66. Further, the signal includes a difference absolute value 212 and a slope absolute value 214.

  The average value calculation unit 60 inputs the temporary offset value 210. The average value calculation unit 60 calculates an average value of the temporary offset values 210 by calculating a moving average for the input temporary offset values 210 in the period Ta. The period Ta is, for example, 5 [seconds] or the like, and a period in which the change in the temperature in the angular velocity calculation device 100 attached to the vehicle is not large and the variation in the offset of the angular velocity sensor 24 due to the temperature is minute. Is set. The average value calculation unit 60 sequentially outputs the calculated average value Va [V] to the absolute difference value calculation unit 62.

  The absolute difference value calculation unit 62 sequentially inputs the average value Va [V] from the average value calculation unit 60. The difference absolute value calculation unit 62 calculates the absolute value of the difference between the sequentially input average values Va [V]. Specifically, the difference absolute value calculation unit 62 holds the average value for at least the period Ta and calculates the absolute value of the difference between the input average value and the average value input before the period Ta. The difference absolute value calculation unit 62 sequentially outputs the calculated absolute value |Va′−Va|[V] (hereinafter, also referred to as “difference absolute value 212”) to the offset value filter processing unit 66. Note that Va' indicates the previous average value.

  The absolute tilt value calculation unit 64 inputs the temporary offset value 210. Further, the absolute tilt value calculation unit 64 associates the input provisional offset value 210 with the elapsed time after activation acquired from the timing function provided in a microcomputer or the like (not shown), and stores it in the ring buffer or the like for a period Ts. Remember. The period Ts is a value larger than the period Ta and is, for example, 10 seconds. The slope absolute value calculation unit 64 performs a function approximation to the time and the temporary offset value 210 to calculate the slope of the temporary offset value 210. The gradient absolute value calculation unit 64 approximates a linear function using the least squares method, for example, with time on the X axis and the temporary offset value on the Y axis. Applying the method of least squares, the slope γn (V/sec) of the temporary offset value 210 is calculated as follows.

ここで、ｍは仮オフセット値２１０のサンプル数、ｔ［ｓｅｃ］は時間、Ｏｆｓ［Ｖ］は仮オフセット値２１０である。傾き絶対値算出部６４は、算出した仮オフセット値２１０の傾きの絶対値｜γｎ｜（Ｖ／ｓｅｃ）（以下、「差分絶対値２１２」ともいう）をオフセット値フィルタ処理部６６へ逐次出力する。

Here, m is the number of samples of the temporary offset value 210, t [sec] is time, and Ofs [V] is the temporary offset value 210. The gradient absolute value calculation unit 64 sequentially outputs the calculated absolute value |γn| (V/sec) of the gradient of the temporary offset value 210 (hereinafter, also referred to as “difference absolute value 212”) to the offset value filter processing unit 66. .

  The offset value filter processing unit 66 inputs the temporary offset value 210, the absolute difference value 212, and the absolute tilt value 214. The offset value filter processing unit 66 derives an offset value 204 for correcting the angular velocity output from the angular velocity sensor 24 by performing statistical processing on the temporary offset value 210. At that time, the offset value filter processing unit 66 derives the forgetting factor used in the statistical processing based on the absolute difference value 212 and the absolute slope value 214. FIG. 5 is used here to explain the configuration of the offset value filter processing unit 66.

  FIG. 5 shows the configuration of the offset value filter processing unit 66. The offset value filter processing unit 66 includes an αi multiplication unit 70, an addition unit 72, a 1-αi multiplication unit 74, and a forgetting factor control unit 76. As illustrated, the offset value filter processing unit 66 is configured to include an IIR (Infinite Impulse Response) filter, and the IIR filter configures a low-pass filter. The αi multiplication unit 70 multiplies the temporary offset value 210 by the forgetting factor “αi”. Here, “i” is 1 or 2. Therefore, the forgetting factor “αi” is a generic term for α1 and α2. Note that α1 and α2 will be described later. The αi multiplication unit 70 outputs the multiplication result to the addition unit 72.

  The addition unit 72 sequentially adds the multiplication result from the αi multiplication unit 70 and the multiplication result from the 1-αi multiplication unit 74. The addition unit 72 sequentially outputs the addition result as the offset value 204. The 1-αi multiplication unit 74 multiplies the offset value 204 by the coefficient “1-αi”. Note that “αi” of the coefficients “1−αi” is the same as αi in the αi multiplication unit 70, and thus the description thereof is omitted here. The 1-αi multiplication unit 74 feeds back the multiplication result to the addition unit 72.

  The forgetting factor control unit 76 inputs the difference absolute value 212 from the difference absolute value calculation unit 62 and the slope absolute value 214 from the slope absolute value calculation unit 64. Further, the forgetting factor control unit 76 determines the value of the forgetting factor “αi” according to the absolute difference value 212 and the absolute gradient value 214. Further, the forgetting factor control unit 76 sets the determined forgetting factor “αi” in the αi multiplying unit 70 and the 1-αi multiplying unit 74. Here, the process for determining the value of the forgetting factor “αi” will be described in detail. The forgetting factor control unit 76 holds a table, and determines the value of the forgetting factor “αi” by referring to the table.

  FIG. 6 shows a data structure of a table stored in the forgetting factor control unit 76. As illustrated, an absolute value condition column 500, a slope condition column 502, and a forgetting factor column 504 are included. In the absolute value condition column 500, “Vth or more” and “less than Vth” are shown as conditions for the absolute difference value 212 for determining the forgetting factor. Here, “Vth” is a threshold value for the absolute difference value 212, and a value equal to or larger than the fluctuation range due to noise included in the temporary offset value 210 is set for this. Further, in the tilt condition column 502, “greater than or equal to γth” and “less than γth” are shown as conditions for the absolute tilt value 214 for determining the forgetting factor. Here, “γth” is a threshold value with respect to the absolute slope value 214, and for example, the absolute value of the slope of the temporary offset value 210 with respect to the temperature fluctuation measured for several seconds after the angular velocity calculation device 100 is activated is measured. The above values are set. The forgetting factor column 504 stores the forgetting factor “αi” corresponding to each condition. “Α1>α2”. When the condition for the absolute difference value 212 is “Vth or more”, the forgetting factor is set to “zero”. Returning to FIG.

  In this way, the forgetting factor control unit 76 sets, for statistical processing, a forgetting factor that increases as the absolute value of inclination 214, which is the gradient of the change in the temporary offset value 210 of the angular velocity sensor 24 over time, increases. In particular, the forgetting factor control unit 76 selects the forgetting factor “α1” or “α2” with reference to the table. Also, the forgetting factor control unit 76, in the second period Ta shorter than the first period Ts for deriving the absolute tilt value 214, the absolute difference value 212 that is the absolute value of the change in the temporary offset value 210 of the angular velocity sensor 24. If is greater than or equal to the threshold, the forgetting factor is set to zero.

  The absolute value of the difference and the absolute value of the slope with respect to the temporary offset value 210 input to the offset value correction unit 34 will be described with reference to FIG. 7. FIG. 7 shows an outline of processing by the offset value correction unit 34. As shown in the figure, a stepwise shift occurs in the temporary offset value 210 input to the offset value correction unit 34. Here, the temporary offset value is shifted stepwise near time A [seconds]. The average value calculation unit 60 calculates the average value V1 and the average value V2 of the temporary offset value 210 in the period Ta before and after the time A [second]. Further, the difference absolute value calculation unit 62 calculates the absolute value |V1-V2|. Further, the absolute tilt value calculation unit 64 calculates the inclination of the temporary offset value 210 in the period Ts. When the absolute value |V1-V2| is less than “Vth” and the absolute value of the inclination is “γth” or more, the offset value correction unit 34 detects the stepwise shift that has occurred in the temporary offset value 210. To do. At this time, the forgetting factor control unit 76 selects the forgetting factor “α1” and increases the weight of the current temporary offset value 210, so that it can follow the true offset value after the shift.

  The operation of the angular velocity calculation device 100 having the above configuration will be described. FIG. 8 is a flowchart showing a procedure for deriving an offset value by the angular velocity calculation device 100. When the absolute difference value 212 is smaller than Vth (Y in S10) and the absolute tilt value 214 is γth or more (Y in S12), the forgetting factor control unit 76 sets the forgetting factor to α1 (S14). When the absolute tilt value 214 is not greater than or equal to γth (N in S12), the forgetting factor control unit 76 sets the forgetting factor to α2 (S16). When the absolute difference value 212 is not smaller than Vth (N in S10), the forgetting factor control unit 76 sets the forgetting factor to zero (S18).

  According to the embodiment of the present invention, the forgetting coefficient that increases as the gradient of change in the temporary offset value of the angular velocity sensor increases is set for the statistical processing. Therefore, when the gradient of change in the temporary offset value is large. Therefore, the influence of the current temporary offset value can be increased. Further, when the slope of change in the temporary offset value is large, the influence of the current temporary offset value becomes large, so that it is possible to follow the variation in the offset value. Further, since the variation of the offset value is followed, even if the offset value of the angular velocity sensor changes abruptly, it is possible to suppress deterioration of the derivation accuracy of the angular velocity.

  Further, since the forgetting coefficient that becomes larger as the inclination of the change in the temporary offset value of the angular velocity sensor becomes larger is set for the statistical processing, if the inclination of the change in the temporary offset value is small, the past temporary offset value is set. The effect of can be increased. Further, when the inclination of change in the temporary offset value is small, the influence of the past temporary offset value becomes large, so that the influence of noise can be reduced. Moreover, since the influence of noise is reduced, it is possible to suppress a decrease in the derivation accuracy of the angular velocity.

  In addition, since the forgetting factor is changed, it is possible to realize the filter processing adapted to the fluctuation of the angular velocity sensor. Further, since the filtering process adapted to the variation of the angular velocity sensor is realized, the derivation accuracy of the angular velocity can be improved. Further, when the absolute value of the change in the temporary offset value for a short period of time is equal to or greater than the threshold value, the forgetting factor is set to zero, so that an unexpected change can be ignored. Further, since unexpected changes are ignored, it is possible to suppress a decrease in the accuracy of deriving the angular velocity.

  The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that this embodiment is an exemplification, and that various modifications can be made to the combinations of the respective constituent elements and the respective processing processes, and that such modifications are within the scope of the present invention. ..

  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, not limited to this, for example, the effectiveness determination unit 22 may use GDOP (Geometric Dilution Of Precision), HDOP (Horizontal Dilution Of Precision), or the like, or a combination thereof. According to this modification, various parameters can be used for determination.

  In the embodiment of the present invention, the offset value filter processing unit 66 is formed to include an IIR filter. However, not limited to this, for example, the offset value filter processing unit 66 may be formed to include an FIR (Finite Impulse Response) filter. At that time, the forgetting factor is set as the tap factor. According to this modification, the degree of freedom in the filter configuration can be improved.

  In the embodiment of the present invention, the forgetting factor control unit 76 sets two kinds of values other than zero as the forgetting factor. However, without being limited to this, for example, the forgetting factor control unit 76 may set three or more types of values other than zero as the forgetting factor. According to this modification, the degree of freedom in the configuration can be improved.

  10 measurement unit, 12 parameter calculation unit, 14 angular velocity conversion unit, 16 control unit, 20 GPS positioning unit, 22 effectiveness determination unit, 24 angular velocity sensor, 26 offset value calculation unit, 28 sensitivity coefficient calculation unit, 30 state estimation unit, 32 state-specific offset value deriving unit, 34 offset value correcting unit, 40 stop estimating unit, 42 straight traveling estimating unit, 44 non-straight traveling estimating unit, 46 stop offset value deriving unit, 48 straight traveling offset value deriving unit, 50 Non-straight running offset value derivation unit, 60 average value calculation unit, 62 difference absolute value calculation unit, 64 inclination absolute value calculation unit, 66 offset value filter processing unit, 70 αi multiplication unit, 72 addition unit, 74 1-αi multiplication Part, 76 forgetting factor control part, 100 angular velocity calculation device.

Claims (2)

An acquisition unit that acquires the positioning data of the object that is positioned based on the signals from the GPS satellites and the angular velocity of the object that is output from the angular velocity sensor;
An offset value derivation unit that sequentially derives a temporary offset value of the angular velocity sensor by using the positioning data and the angular velocity acquired by the acquisition unit,
By performing statistical processing on the temporary offset value of the angular velocity sensor sequentially derived by the offset value deriving unit, the offset value of the angular velocity sensor for correcting the angular velocity output from the angular velocity sensor is derived. An offset value filter processing unit is provided,
The offset value filter processing unit sets, for statistical processing, a forgetting coefficient that becomes larger as the slope of change in the temporary offset value of the angular velocity sensor with time increases ,
The offset value filter processing unit changes the temporary offset value of the angular velocity sensor during a second period that is shorter than the first period for deriving the slope of the change in the temporary offset value of the angular velocity sensor over time. An angular velocity sensor correction device , wherein the forgetting factor is set to zero when the absolute value is equal to or greater than a threshold value . Acquiring positioning data of an object positioned based on signals from GPS satellites and angular velocity of the object output from the angular velocity sensor;
Using the acquired positioning data and the angular velocity, successively deriving a temporary offset value of the angular velocity sensor,
By performing statistical processing on the provisional offset value of the angular velocity sensor sequentially derived, the step of deriving an offset value of the angular velocity sensor for correcting the angular velocity output from the angular velocity sensor,
In the step of deriving the offset value of the angular velocity sensor, a forgetting coefficient is set for statistical processing such that the inclination of the change in the provisional offset value of the angular velocity sensor with respect to the lapse of time becomes larger ,
The step of deriving the offset value of the angular velocity sensor includes the temporary offset of the angular velocity sensor in a second period shorter than the first period for deriving a slope of change of the temporary offset value of the angular velocity sensor with respect to time. A method for correcting an angular velocity sensor, characterized in that the forgetting factor is set to zero when the absolute value of the change in value is equal to or greater than a threshold value .

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