JP4376738B2 - Apparatus and method for detecting zero point error of angular velocity sensor - Google Patents

Description

  The present invention relates to a zero point error detection apparatus and method for an angular velocity sensor, and more particularly to a technique for detecting a zero point error when the angular velocity sensor is not stationary.

  In general, in-vehicle navigation devices detect the current position of a vehicle using a self-contained navigation sensor, a GPS (Global Positioning System) receiver, or the like, and read map data in the vicinity from the recording medium and display it on a screen. Then, the vehicle position mark indicating the vehicle position is superimposed and displayed at a predetermined location on the screen, so that it can be seen at a glance where the vehicle is currently traveling.

  The self-contained navigation sensor includes a vehicle speed sensor (distance sensor) that outputs a single pulse for each predetermined travel distance to detect the travel distance of the vehicle, and an angular velocity sensor such as a vibration gyro that detects the rotation angle (movement direction) of the vehicle. (Relative angular velocity sensor). The self-contained navigation sensor detects the relative position and relative direction of the vehicle by using these vehicle speed sensor and angular velocity sensor.

  In general, an angular velocity sensor is a zero point in which an output voltage when a vehicle on which the vehicle is mounted is stationary (when the output of the vehicle speed sensor is 0) is regarded as a reference voltage, and an angular velocity is obtained from a deviation from the reference voltage. A correction method called correction is adopted. However, the output voltage value of the angular velocity sensor varies greatly due to the influence of the ambient temperature. For this reason, if the angular velocity sensor is affected by the ambient temperature while the vehicle cannot perform zero point correction, the reference voltage value acquired at the time of the previous stop will deviate significantly from the true voltage value of the zero point. Point error is generated.

  When a zero point error occurs, the vehicle direction signal obtained using the angular velocity sensor includes many errors. This is because the self-contained navigation sensor using the angular velocity sensor has a mechanism in which the angular velocity output from the angular velocity sensor is integrated to obtain the azimuth, so that the zero point error is accumulated as the azimuth error. Therefore, in order to make the azimuth error detected by the angular velocity sensor as small as possible, it is desirable to make the zero point error as small as possible while the vehicle is traveling.

In view of such problems, conventionally, there has been proposed an apparatus aimed at minimizing a zero point error during traveling of a vehicle (see, for example, Patent Document 1). In the technique described in Patent Document 1, a predetermined number (for example, 60 sets) of pairs of the azimuth change amount by the angular velocity sensor and the azimuth change amount by the GPS receiver is captured while the vehicle is traveling. Then, each set of data is plotted on coordinates with the azimuth change by the GPS receiver as the x-axis and the azimuth change by the angular velocity sensor as the y-axis, and a straight line fitted from each plotted point by the least square method “Y = ax + b” is calculated. The y coordinate value b of the intersection of the straight line with the y axis is obtained as a zero point error, and zero point correction is performed.
JP-A-10-206177

  However, in the prior art described in Patent Document 1, all sets of the azimuth change data obtained by the angular velocity sensor and the azimuth change data obtained by the GPS receiver are used without any consideration, and the minimum A straight line representing the relationship between the azimuth change amount by the angular velocity sensor and the azimuth change amount by the GPS receiver is estimated by a simple process called multiplication. For this reason, there is a problem that the estimated straight line includes many errors and the zero point error cannot be calculated accurately.

  The present invention has been made to solve such a problem, and an object thereof is to improve the calculation accuracy of the zero point error.

In order to solve the above-described problem, in the present invention, the first azimuth signal output from the azimuth sensor at regular time intervals and the second azimuth signal output from the GPS receiver at regular time intervals are 1 predetermined conditions (the speed of the vehicle equipped with the angular velocity sensor is equal to or higher than a threshold, the autonomous navigation travel distance of a section obtained by the autonomous navigation sensor, and the certain section obtained by the GPS receiver) All that the difference between the GPS positioning points in the corresponding section is less than the threshold value, and that the amount of change in the first azimuth signal obtained by the azimuth sensor in the past certain period is less than the threshold value) Only the combination of the azimuth signals output when satisfying the condition is selectively extracted, and the zero point error of the angular velocity sensor is calculated using the extracted set of azimuth signals.

  In another aspect of the present invention, the first azimuth change angle representing the difference between the first azimuth signals and the second azimuth change representing the difference between the second azimuth signals when calculating the zero point error. Only a sample satisfying the second predetermined condition is selectively extracted from a plurality of zero point error samples calculated from the correspondence with the angle, and statistical processing is performed using the extracted zero point error samples. Like to do.

  According to the present invention configured as described above, an azimuth signal or zero point error that is likely to contain an error is discarded without satisfying a predetermined condition, and an azimuth signal or zero point error that is less likely to contain an error. Since the zero point error of the angular velocity sensor is calculated by selectively using only the sample, the zero point error with high accuracy can be calculated.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a zero point error detection device for an angular velocity sensor according to the present embodiment. As shown in FIG. 1, the zero point error detection device of the present embodiment includes a self-contained navigation sensor 1, a position / orientation calculation unit 2, a GPS receiver 3, a memory controller 4, a RAM (running history storage unit) 5, and a processor 6. It is configured with. The zero point error detection device is mounted on, for example, a navigation device that provides vehicle travel guidance.

  The self-contained navigation sensor 1 is for measuring the current position of the vehicle, and includes a distance sensor (vehicle speed sensor) 1a and an angular velocity sensor (relative direction sensor) 1b such as a vibration gyro. The distance sensor 1a detects a moving distance of the vehicle by outputting one pulse at regular time intervals. The angular velocity sensor 1b detects an angular velocity that changes as the vehicle travels, integrates the detected angular velocity, and outputs a rotation angle (moving direction) of the vehicle at regular intervals. The self-contained navigation sensor 1 detects the relative position and relative direction of the vehicle at regular intervals by the distance sensor 1a and the angular velocity sensor 1b, and sequentially outputs the information.

  The position / orientation calculation unit 2 calculates an absolute vehicle position (estimated vehicle position) and vehicle direction based on information on the relative position and relative direction of the vehicle output from the self-contained navigation sensor 1, and at regular intervals. Output. The absolute azimuth signal output from the position / azimuth calculation unit 2 corresponds to the first azimuth signal of the present invention. Hereinafter, the absolute position and the absolute direction calculated based on the output of the self-contained navigation sensor 1 are referred to as a gyro position and a gyro direction, respectively. The angular velocity sensor 1b and the position / orientation calculation unit 2 constitute the azimuth sensor of the present invention.

  The GPS receiver 3 is also for measuring the current position of the vehicle, and receives radio waves transmitted from a plurality of GPS satellites (not shown) by a GPS antenna (not shown) and performs a three-dimensional positioning process or a two-dimensional positioning process. The absolute position and the absolute direction of the vehicle are calculated at the same fixed time as the angular velocity sensor 1b (the vehicle direction is calculated based on the current vehicle position and the current vehicle position one sampling time ΔT before). Then, the calculated absolute position and absolute direction information of the vehicle is sequentially output together with the positioning time. The absolute azimuth signal output from the GPS receiver 3 corresponds to the second azimuth signal of the present invention. Hereinafter, the absolute position and the absolute direction calculated based on the output of the GPS receiver 3 are referred to as a GPS position and a GPS direction, respectively.

  The memory controller 4 sequentially stores the gyro position and gyro direction obtained by the position / orientation calculation unit 2 in the RAM 5 as data of a travel history by the self-contained navigation sensor 1. Further, the GPS position and the GPS direction obtained by the GPS receiver 3 are sequentially stored in the RAM 5 as data of a travel history by the GPS receiver 3. The memory controller 4 also reads travel history data from the RAM 5 and supplies it to the processor 6 in response to a request from the processor 6.

2 is an image diagram showing an example of travel history data stored in the RAM 5, FIG. 2 (a) shows a travel history by the GPS receiver 3, and FIG. 2 (b) shows a travel history by the self-contained navigation sensor 1. ing. In FIG. 2A, black circles indicate GPS positions output at regular intervals (for example, every second), and arrows indicate GPS directions output at regular intervals (for example, every other second). The GPS azimuth is also represented by a symbol of θ _gps n (n is 1, 2,... N, N is an arbitrary integer). In this example, θ _gps N is the current GPS azimuth that was output most recently, and for example, θ _gps 1 is the past GPS azimuth output N seconds before.

In FIG. 2B, white circles indicate the gyro positions output at regular time intervals (for example, every second), and arrows indicate the gyro orientations output at regular time intervals (for example, every other second). The gyro direction is also represented by the symbol θ _gyr n (n is 1, 2,... N, N is an arbitrary integer). In this example, θ _gyr N is the current gyro azimuth output most recently, and for example, θ _gyr 1 is the past gyro azimuth output N seconds before.

  FIG. 2 shows that the GPS heading shows a relatively accurate value when the vehicle is traveling on a straight road, whereas the gyro heading shifts with time (the zero point error increases). Show)

  The processor 6 includes a primary sampling unit 6a, a zero point error sample calculation unit 6b, a secondary sampling unit 6c, and a statistical processing unit 6d as functional configurations. The zero point error sample calculation unit 6b and the statistical processing unit 6d constitute the zero point error calculation means of the present invention.

The primary sampling unit 6a has a first gyro direction θ _gyr n (first direction signal) and a GPS direction θ _gps n (second direction signal) stored in the RAM 5 at regular time intervals. Only the azimuth signal output when the predetermined condition is satisfied is selectively extracted. The first predetermined condition is at least one of the following three conditions (1) to (3). The primary sampling may be performed under any one condition, but the primary sampling is preferably performed under two and more preferably three AND conditions.

(1) The speed of the vehicle on which the angular velocity sensor 1b is mounted is not less than a threshold value (for example, 10 [km / h]). This is because when the vehicle speed is low, the GPS heading error often increases. The vehicle speed can be obtained from the output of the distance sensor 1a. That is, it can be obtained by dividing the distance between successive gyro positions stored as a travel history in the RAM 5 by the time (1 second) between them. Of course, it is also possible to determine by dividing the distance between successive GPS positions by the time (1 second) between them. In addition to the position and direction information, the vehicle speed information may be stored in advance in the RAM 5 as travel history data.

(2) The reliability of GPS is high. This is because when the GPS reliability is low, the GPS heading error often increases. As a method for determining whether the GPS reliability is high or low, for example, the technologies of Japanese Patent Application Nos. 2002-10235 and 2002-179486, which have already been filed by the present applicant, can be applied. According to this technology, the travel distance of a certain section obtained by the self-contained navigation sensor 1 (self-contained navigation travel distance), and the distance of the section corresponding to the certain section obtained by the GPS receiver 3 (the distance between GPS positioning points) When the difference is equal to or less than the threshold value, it can be determined that the GPS reliability is high. In addition, although the example which applies the technique of Japanese Patent Application 2002-10235 and Japanese Patent Application 2002-179486 is demonstrated here, the determination method of GPS reliability is not limited to this.

(3) The curvature (or direction change rate) is low. This is because when the curvature (direction change rate) is high, the GPS azimuth error often increases. Regarding the curvature, for example, the condition is that the amount of change in the gyro azimuth obtained by the angular velocity sensor 1 in the past fixed period (for example, the past 30 m) is not more than a threshold value (for example, 5 degrees corresponding to R344). Regarding the azimuth change rate, for example, the amount of change in the gyro azimuth obtained by the angular velocity sensor 1 in the past fixed period (for example, the past 5 seconds) is below a threshold (for example, 30 degrees (6 [deg / s])). It must be a condition.

The data extracted according to the above conditions is hereinafter referred to as “primary sample”.
Here, the gyro azimuth obtained at regular intervals by the position / azimuth calculation unit 2 and the GPS azimuth obtained at regular intervals by the GPS receiver 3 are all temporarily stored in the RAM 5, and the condition is met from among them. Although the example which extracts is demonstrated, it is not limited to this. For example, primary sampling may be performed when the gyro direction and the GPS direction are stored in the RAM 5, and only those that meet the conditions may be selectively stored in the RAM 5.

  The zero point error sample calculation unit 6b is extracted by a first azimuth change angle (hereinafter referred to as a gyro change angle) representing a difference between gyro azimuths extracted by the primary sampling unit 6a and the primary sampling unit 6a. A plurality of zero point error samples are calculated from a correspondence relationship with a second azimuth change angle (hereinafter referred to as a GPS change angle) representing a difference between GPS azimuths. The contents of this calculation will be described with reference to FIG.

The gyro change angle is obtained by the following (Equation 1).
Gyro change angle = θ _gyr N−θ _gyr i (i is N−1, N−2,..., And the time from the current primary sample N to the target primary sample i is a threshold value (for example, 60 (Second) or less) (Equation 1)
Further, the GPS change angle is obtained by the following (Equation 2).
GPS change angle = θ _gps N−θ _gps i (i is N−1, N−2,..., And the time from the current primary sample N to the target primary sample i is a threshold value (for example, 60 (Second) or less) (Equation 2)

  The threshold value is provided for the value of i in consideration of the followability of zero point correction. That is, by providing a threshold value for the value of i, it is possible to obtain a zero point error of the angular velocity sensor 1b at regular intervals and perform zero point correction.

Further, the zero point error sample is obtained by the following (Equation 3).
Zero point error sample = (Gyro change angle−GPS change angle) / Time difference of primary sample (Equation 3)
Here, a plurality of gyro change angles and GPS change angles are obtained, and a plurality of zero point error samples are obtained by calculating (Equation 3) for each.

  FIG. 3 is a diagram for explaining the meaning of (Expression 3). In FIG. 3, the dotted line indicated by reference numeral 31 is the output voltage value at the nearest zero point obtained when the vehicle was last stationary. On the other hand, the solid line indicated by reference numeral 32 is the true voltage value at the zero point at which the angular velocity sensor 1 changes due to the influence of the ambient temperature while the vehicle is traveling. In the present embodiment, since the primary sampling is performed according to the above conditions (1) to (3), the GPS change angle indicates an almost accurate value, and in terms of the angular velocity sensor 1b, the zero point does not change. This corresponds to 31. On the other hand, when the output of the angular velocity sensor 1b changes under the influence of the ambient temperature, the zero point changes, so that the gyro change angle corresponds to the solid line 32. Therefore, the instantaneous value of the zero point error can be obtained by taking the difference between the gyro change angle and the GPS change angle and dividing by the time difference of the primary sample as shown in (Equation 3). This is the zero point error sample.

  The secondary sampling unit 6c selectively extracts only those satisfying the second predetermined condition described below from the plurality of zero point error samples calculated by the zero point error sample calculating unit 6b. The second predetermined condition is at least one of the following two conditions (4) to (5). Secondary sampling may be performed under any one condition, but preferably secondary sampling is performed under two AND conditions.

(4) The GPS change angle between the current primary sample N and the target primary sample i is not more than a threshold value (for example, 45 [deg]). This is because the sensitivity error of the angular velocity sensor 1b often increases when the GPS change angle is large. The sensitivity error represents a change in the output of the angular velocity sensor 1b due to the mounting angle of the angular velocity sensor 1b and the inclination of the vehicle.

(5) The calculated zero point error sample is not more than a threshold value (for example, 1 [deg / s]). This is because when the value of the zero point error sample is extremely large as compared with others, it is highly likely that the value is an abnormal value, and if the zero point error is calculated including this, the accuracy may be deteriorated.

  The data extracted according to the above conditions is hereinafter referred to as “secondary sample”. The statistical processing unit 6d calculates the zero point error of the angular velocity sensor 1b by statistically processing a plurality of zero point error samples (secondary samples) extracted by the secondary sampling unit 6c. For example, a plurality of zero point error samples extracted as secondary samples are subjected to a moving average (for example, the latest 1000 averages are performed when 500 secondary samples are obtained). Note that it is possible to improve the calculation accuracy by excluding secondary samples having a large difference from the average value (for example, secondary samples having a difference of 15% or more) and calculating the average value again.

  Next, the operation of the zero point error detection apparatus configured as described above will be described. FIG. 4 is a flowchart showing the zero point error detection method of the angular velocity sensor according to the present embodiment. In FIG. 4, first, the angular velocity is detected by the angular velocity sensor 1, the detected angular velocity is integrated, and information on the relative position and relative orientation is output to the position / orientation calculation unit 2 at regular intervals. The position / azimuth calculation unit 2 obtains the gyro position and the gyro direction based on the information on the relative position and the relative direction, and outputs the gyro position and the gyro direction to the memory controller 4. The memory controller 4 sequentially stores the gyro position and gyro direction obtained at regular intervals in the RAM 5 (step S1).

  Further, the GPS receiver 3 receives the radio wave from the GPS satellite and performs the positioning process, thereby obtaining the GPS position and the GPS azimuth at the same fixed time as the angular velocity sensor 1 and outputting it to the memory controller 4. The memory controller 4 sequentially stores the GPS position and GPS azimuth obtained at regular intervals in the RAM 5 (step S2). Note that the processing in step S1 and the processing in step S2 are actually performed simultaneously.

  Next, the primary sampling unit 6a of the processor 6 obtains the first predetermined conditions (1) to (3) described above from the gyro azimuth and GPS azimuth stored in the RAM 5 at regular intervals. A set of the gyro azimuth and GPS azimuth that has been selected is selectively extracted (step S3). At the time of this condition determination, the gyro position and the GPS position stored in the RAM 5 at regular intervals are used. That is, the calculation of the vehicle speed in the condition (1) and the calculation of the autonomous navigation travel distance and the distance between GPS positioning points in the condition (2) are performed using the gyro position and the GPS position.

  When the primary sample is obtained in this way, the zero point error sample calculation unit 6b calculates a plurality of zero point error samples using the gyro azimuth and the GPS azimuth extracted as the primary sample (step S4). That is, from the correspondence relationship between the gyro change angle representing the difference between the gyro azimuths extracted by the primary sampling unit 6a and the GPS change angle representing the difference between the GPS azimuths extracted by the primary sampling unit 6a, (Equation 1) A plurality of zero point error samples are calculated based on (Equation 3).

  Further, the secondary sampling unit 6c selectively extracts those satisfying the second predetermined conditions (4) to (5) described above from the plurality of zero point error samples calculated in step S4 ( Step S5). Then, the statistical processing unit 6d calculates the zero point error of the angular velocity sensor 1b by statistically processing the plurality of zero point error samples extracted by the secondary sampling unit 6c (step S6).

  As described in detail above, according to the present embodiment, the first gyro direction obtained from the output of the angular velocity sensor 1 at regular intervals and the GPS direction obtained at regular intervals from the output of the GPS receiver 3 are Only the combination of the gyro azimuth and GPS azimuth output when the predetermined condition is satisfied is extracted, and the zero point error of the angular velocity sensor 1 is calculated using only the extracted azimuth information.

  Furthermore, in the present embodiment, only those satisfying the second predetermined condition are selectively extracted and extracted from a plurality of zero point error samples calculated from the correspondence relationship between the gyro change angle and the GPS change angle. Only the zero point error sample is used to calculate the zero point error of the angular velocity sensor 1b.

  As a result, azimuth signals and zero-point error samples that are likely to contain errors are discarded without satisfying the predetermined conditions, and only the azimuth signals and zero-point error samples that are less likely to contain errors are selectively used for angular velocity. The zero point error of the sensor 1 can be calculated, and the calculation accuracy of the zero point error can be improved.

  Further, in this embodiment, since the azimuth change angle is obtained between the current sample N and a plurality of past samples i (i = N−1, N−2,...), One Currently, a lot of direction change information is condensed with respect to the sample N. That is, compared to the prior art of Patent Document 1 in which the azimuth change amount is simply obtained between consecutive samples, the zero point error can be obtained using a significantly larger number of samples even within the same sampling time. The calculation accuracy can be further improved.

  As described above, the zero point error of the angular velocity sensor 1b can be accurately corrected even while the vehicle is traveling, and the direction detection accuracy by the self-contained navigation sensor 1 can be improved. Thereby, the measurement precision of the own vehicle position in the whole navigation apparatus improves.

  In the above embodiment, an example in which both primary sampling and secondary sampling are performed has been described, but an example in which only one of the samplings is performed is also included in the present invention. Even if only one of the samplings is performed, it is possible to calculate a zero point error with higher accuracy than the conventional technique of Patent Document 1.

  In addition, each of the above-described embodiments is merely an example of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. In other words, the present invention can be implemented in various forms without departing from the spirit or main features thereof.

  INDUSTRIAL APPLICABILITY The present invention is useful for a zero point error detection apparatus and method that can determine a zero point error even when the angular velocity sensor is not stationary.

It is a block diagram which shows the structural example of the zero point error detection apparatus of the angular velocity sensor by this embodiment. It is an image figure which shows the example of the travel history data stored in RAM. It is a figure for demonstrating the meaning of (Formula 3) which calculates | requires a zero point error sample. It is a flowchart which shows the zero point error detection method of the angular velocity sensor by this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Self-contained navigation sensor 1a Distance sensor 1b Angular velocity sensor 2 Position / azimuth calculating part 3 GPS receiver 4 Memory controller 5 RAM (travel history storage part)
6 processor 6a primary sampling unit 6b zero point error sample calculation unit 6c secondary sampling unit 6d statistical processing unit

Claims (6)

An angular velocity sensor that detects an angular velocity, integrates the detected angular velocity and outputs a relative bearing signal, and obtains a first bearing signal from the relative bearing signal and outputs the first bearing signal at fixed intervals;
A GPS receiver that outputs a second azimuth signal at the same fixed time as the azimuth sensor by receiving a radio wave from a GPS satellite and performing a positioning process;
Of the first azimuth signal and the second azimuth signal output at regular intervals, as a first predetermined condition, the speed of the vehicle equipped with the angular velocity sensor is equal to or higher than a threshold value. The difference between the autonomous navigation travel distance of a section obtained by the autonomous navigation sensor and the distance between GPS positioning points of the section corresponding to the certain section obtained by the GPS receiver is equal to or less than a threshold value; And the first azimuth signal and the second azimuth signal that are output when the amount of change of the first azimuth signal obtained by the azimuth sensor in the past certain period is less than or equal to a threshold value. Primary sampling means for selectively extracting
An angular velocity comprising: zero point error calculating means for calculating a zero point error of the angular velocity sensor using the first azimuth signal and the second azimuth signal extracted by the primary sampling means. Sensor zero point error detection device. The zero point error calculating means includes a first azimuth change angle representing a difference between the first azimuth signals extracted by the primary sampling means and a difference between the second azimuth signals extracted by the primary sampling means. A plurality of zero point error samples, which are instantaneous values of the zero point error, are calculated from the corresponding relationship with the second azimuth change angle representing the above, and the zero point error is calculated by statistically processing the plurality of zero point error samples. The zero point error detecting device for an angular velocity sensor according to claim 1. Secondary sampling means for selectively extracting a plurality of zero point error samples calculated by the zero point error calculation means from those satisfying a second predetermined condition;
3. The zero point error detecting device of an angular velocity sensor according to claim 2 , wherein the zero point error calculating means performs the statistical processing using a plurality of zero point error samples extracted by the secondary sampling means. . 4. The zero point error detecting device for an angular velocity sensor according to claim 3 , wherein the second predetermined condition is that the second azimuth change angle is not more than a threshold value. 4. The angular velocity sensor zero point error detecting device according to claim 3 , wherein the second predetermined condition is that a value of the zero point error sample is equal to or less than a threshold value. The second predetermined condition is at least one of the second azimuth change angle being a threshold value or less and the zero point error sample value being a threshold value or less. The zero point error detecting device for an angular velocity sensor according to claim 3 .

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