JPH03221813A - Azimuth detector with offset correcting function - Google Patents

Abstract

PURPOSE:To accurately detect the azimuth of a moving body by storing an offset value as the function value of an injection current into a semiconductor light source for an optical fiber gyro, and using the read value for correcting the offset. CONSTITUTION:The output data DELTAthetaG, thetaH of the optical fiber gyro 43 and an earth magnetism sensor 42 are inputted to a locator 1. In order to find out the offset of data DELTAthetaG of the gyro 43, an injection measuring circuit 45 reads out current. Then an offset value corresponding to the current is read out from an offset memory 21. The locator 1 subtracts the calculated offset value from the gyro data DELTAthetaG to correct the gyro data DELTAthetaG. The current azimuth thetaG is found out from the corrected data DELTAthetaG and compared with the data thetaH of the sensor 42 and the data having higher reliability are selected. Then, the current position of a vehicle is calculated from the obtained azimuth data and traveling distance data found from the output of a vehicle speed sensor 41.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to turning angular velocity sensors (for example, optical fiber gyros, mechanical gyros, vibration gyros, and cascade gyros), especially when an optical fiber gyro is used. The present invention relates to an orientation detection device having an offset correction function for correcting the offset.

<Prior Art> Conventionally, the description will be given based on vehicles traveling at any point on a road transportation network, aircraft navigating air routes, ships navigating sea routes, etc. (hereinafter referred to as "vehicles"). Vehicle's "
The turning angular velocity sensor performs the necessary processing on the output signals from the turning angular velocity sensor and the turning angular velocity sensor. It has been proposed to include a processing device and obtain current orientation data of the vehicle using the orientation change M (angular velocity) Δθ that occurs as the vehicle travels.

The method employed in this device is to calculate the current orientation θ of the vehicle as θ ← θ0 + Δ θ based on the angular velocity data Δθ. θO is the direction determined at the previous sampling point.

Based on this azimuth data θ and vehicle travel distance data Δ, which is obtained separately, the east-west direction component Δx of Δ
ΔJXcosθ) and north-south direction component Δy (=ΔJX
Sjno), the previous vehicle position (PX', Py
) by adding the current vehicle position data (P
x, Py), the above-mentioned direction detecting device is used for detecting the position of a vehicle.

Note that in reality, the output of the turning angular velocity sensor is a digital value, which is A/D converted by an A/D converter.
The turning angle is determined by feeding the signal to a computer and reading out the digital value by the computer. Furthermore, some systems use a geomagnetic azimuth sensor to determine the absolute azimuth, and compare it with azimuth data obtained from the output of the turning angular velocity sensor to obtain more reliable azimuth data.

However, with optical fiber gyros and other rotary angular velocity sensors, even when the sensor output should be 0 when traveling in a straight line, there is a tendency for some output (offset) to occur due to the effects of temperature and humidity. be. This offset output appears as an error in the sensor output and has the property of accumulating, so that a direction deviated from the actual running direction will be detected.

Therefore, it is necessary to always obtain accurate offset values and correct the detected orientation. Therefore, a method has been proposed that takes advantage of the fact that when a vehicle is stopped at a traffic light or the like, only the offset appears in the output of the turning angular velocity sensor, and subtracts the offset from the data while the vehicle is running. Various devices have been proposed for correcting the offset using the output of the turning angular velocity sensor while the vehicle is stopped (for example, see Japanese Patent Application No. 1983-245703 filed by the present applicant).

<Problem to be solved by the invention> However, the output of the optical fiber gyro is
It has the property of fluctuating (drifting) due to changes in temperature and humidity regardless of when driving. Therefore, the offset value measured while the vehicle is stopped changes due to drift after the vehicle starts, and as a result, an error occurs in the determined direction.

If the time between starting the vehicle and stopping at night is short, you can correct it again while the drift is small, but if the time between starting the vehicle and the next stop is long, there will be no opportunity to correct the offset, and the drift will be large. It becomes something.

An object of the present invention is to calculate the offset value of the optical fiber gyro used for direction detection in a direction detection device that takes in the output data of an optical fiber gyro and calculates the current direction of a moving body from the output data and the past detected direction. It is an object of the present invention to provide a direction detection device having an offset correction function that allows accurate correction even while the vehicle is running.

Means and operation for solving the above-mentioned problems> As shown in FIG. , a current measuring means 12 for measuring the injection current (2) of the semiconductor light source of the optical fiber gyro 1], and a memory 13 for storing the offset value of the optical fiber gyro as a function value 0(I) of the injection current 1. (ii) an offset correction means for reading a current from the current measurement means 12 and correcting the output of the optical fiber gyro 11 using an offset value corresponding to the current stored in the memory 13; and an output from the offset correction means 14. The angular velocity Δθ of the moving object is calculated from the output of the optical fiber gyro corrected by
and azimuth determining means 15 for determining the current estimated azimuth θ of the moving object based on this.

The azimuth θ of the moving object is expressed as follows, including the offset, where Δθ is the angular velocity data obtained from the output of the optical fiber gyro.

θ−θ0+Δθ→−o (T) Here, θ0 is the previously determined direction, and 0(T) is the offset value, which changes with temperature.

According to the offset calculation device of the present invention, the offset value o
(I) can be estimated based on the injection current (2) of the semiconductor light source of the optical fiber gyro 11. This is because offset is a turning angular velocity sensor that uses an optical fiber gyro 11, which generally uses a technology to control the injection current in order to keep the amount of light constant regardless of the ambient temperature. This is because by measuring , it is possible to estimate the ambient temperature and, by extension, the amount of offset.

The offset is stored as a function of the current I, and the offset value corresponding to the current of the semiconductor light source of the optical fiber gyro 11 determined by the current measuring means 12 is read out at any time regardless of whether the moving object is running or stopped, and the read value is The output of the optical fiber gyro is corrected by determining the offset using .

This corrected value is supplied to the azimuth determination means 15, and the azimuth of the moving object is calculated.

In this way, it is possible to perform correction including offset drift in real time, and therefore it is possible to detect the orientation of the moving object more accurately.

Further, as described in claim 2, the memory 3 stores the fluctuation rate of the offset of the optical fiber gyro 1 as a function α(I) of the current I, and the offset correction means 14
The current may be read from the current measuring means 12 and the output of the optical fiber gyro may be corrected based on the previous offset value and the fluctuation rate of the offset corresponding to the temperature stored in the memory 13.

According to this, the temperature fluctuation rate of the offset is stored as a function of the current I, and the offset fluctuation rate α(I) corresponding to the current determined by the temperature measurement means 2 is determined regardless of whether the moving object is running or stopped. The output of the optical fiber gyro can be corrected by reading the offset value at any time, calculating the variation of the offset using the read value, and adding it to the previously calculated offset value.

Further, as described in claim 3, the memory may set the offset of the optical fiber gyro to a function value o (I
), and a memory update means may be newly provided to obtain the offset value and the injection current at that time while the moving object is stopped, and update the 0 contents of the memory based on the offset value and the injection current at that time.

Thereby, the contents of the memory are updated based on the offset value while the movable body is stopped (therefore, it is possible to cope with changes over time in the offset characteristics of the optical fiber gyro.

Furthermore, as described in claim 4, the memory stores the temperature fluctuation rate of the offset of the optical fiber gyro as a function α(I) of the injection current I, and the offset correction means stores the previous offset value and the memory. The temperature fluctuation rate α (
I) may be used to correct the output of the optical fiber gyro.

In this case as well, the contents of the memory can be updated to always be in the latest state, as in the case of claim 3.

<Example> Embodiments will be described in detail below with reference to the accompanying drawings showing examples.

FIG. 2 is a block diagram showing an embodiment in which the orientation detection device of the present invention is applied to a vehicle position detection device. However, it should be noted in advance that the azimuth detecting device of the present invention is not necessarily used only for detecting the position of a vehicle, but can also be used for detecting the azimuth of an aircraft or a ship.

The vehicle position detection device includes: -Vehicle speed sensor 41 that detects the rotation speed of both left and right wheels (this sensor is used as a distance sensor) -Geomagnetic sensor 42 -Optical fiber gyro 43 -Injected current of semiconductor light source■ An injection current measurement circuit 45 that measures the road map data, - calculates the estimated heading of the vehicle based on the output data detected by the road map memory 2, the optical fiber gyro 43, and the geomagnetic sensor 42, and A locator that calculates the position output data of the vehicle along with the data of 41 and stores it in the buffer memory 3 ], - A navigation system that displays the read vehicle current position on the display 7 superimposed on the map and interfaces with the keyboard 8 2 controller 5.

The locator 1 obtains the number of wheel rotations by counting the number of output pulse signals from the vehicle speed sensor 41, and uses a multiplier to calculate the number of rotations per count for the count output data output from the counter. The mileage output per unit time is calculated by multiplying by a predetermined constant indicating the distance, and the relative change in vehicle direction is determined from the optical fiber gyro 43, and the vehicle direction is determined from this and the absolute direction output data from the geomagnetic sensor 42. This is to calculate the azimuth output data.

The internal structure of the optical fiber gyro 43 is shown in FIG. A laser diode 432 is connected to the output side of a light source drive circuit 431 including a semiconductor light source of an optical fiber gyro 43 via a reference resistor 433, and the irradiation light beam of the laser diode 432 passes through an optical fiber body 434 and is transmitted to a light receiving diode 435. is incident on the Light receiving diode 43
5 is connected to a processing circuit 436 that calculates the turning angular velocity as a phase change of the drying destination. Furthermore, in order to keep the light emitting output of the laser diode 432 constant, a second light receiving diode 437 provided in the light source drive circuit 431 monitors the amount of light. The voltage across the reference resistor 433 is measured by a voltage measuring means built into the injection current measuring circuit 45.

Returning to FIG. 2, the optical fiber gyro 43 is subjected to a temperature test in a constant temperature layer in advance, and the offset value of the optical fiber gyro 43 at that time is stored in the offset memory 21 in relation to the temperature. Furthermore, the above temperature is converted from the value of the injection current (2) measured by the injection current measurement circuit 45. This is because the output fluctuation factor of the laser diode 432 is mainly based on the ambient temperature, and the current I is controlled in the processing circuit 46 so that the output of the laser diode 432 is always constant. Therefore, the offset can be stored in a table in memory as a function o (I) of the injection current I, as shown in the table below.

4 Table 1 If the above table is used, the offset value can be determined by searching the table at any time while the vehicle is running, as will be described later.

The road map memory 2 stores road map data covering a predetermined range in advance, and includes a semiconductor memory,
Cassette tape, CI)-ROM.

IC memory, DAT, etc. can be used.

The display 7 uses a CRT, liquid crystal display, or the like to display a road map and the vehicle position while the vehicle is traveling.

The navigation controller 5 is composed of a graphic processing processor, an image processing memory, etc.
Scroll, display the current position of the vehicle, etc.

A procedure for detecting vehicle direction using the device configured as described above will be explained. While the vehicle is running, the position of the vehicle is displayed on the display 7 along with a map based on the output data of each sensor taken in by the locator 1, but even during the display, the output data of each sensor is displayed due to interruptions for a certain period of time. I am trying to import the data and update the vehicle position. FIG. 4 shows the vehicle direction detection flow at the time of this interruption. Note that this interruption may be performed every fixed distance traveled, which is determined based on the distance output data of the vehicle. The length of the above-mentioned fixed time or fixed traveling distance is appropriately set depending on the characteristics of the optical fiber gyro used, the performance of the geomagnetic sensor, and the like.

First, in step (2), the output data ΔθG of the optical fiber gyro 43 and the output data of the geomagnetic sensor 42 are set to θ
Take in H.

Next, the offset of the output data Δ6 θ0 of the optical fiber gyro 43 is determined. Therefore, the current is read using the injection current measuring circuit 45 (step ■).

Next, an offset value corresponding to the current is read from the offset memory 21 (step 2).

If the current measured in the injection current I, 11 constant circuit type circuit is not among the currents in the table above, the offset value can be interpolated according to the following equation.

k-1kl + o (lkl)...■
If you have enough memory, you can create a 2-note table for each smaller current, and you can directly obtain the offset value without using a straight line interpolation method like in equation (2). .

Further, if the offset changes with respect to temperature in a form close to a simple straight line, the number of temperatures in Table 1 may be further reduced to create a rough table. At this time, you can interpolate using the formula ■.

Furthermore, in order to obtain the offset more accurately, the offset value obtained as described above may be displaced based on the offset value when the vehicle is stopped.

To explain this method in detail, Fig. 5 shows the optical fiber gyro 4
This is a graph showing the instantaneous value of the output data of No. 3, and shows how the offset value is corrected from A to 0 from the time of stopping t2 to the next start ++, 7t3. After starting,
As shown by the broken line in the graph, the offset appears again and changes in response to temperature fluctuations.

Therefore, if you measure the current Io while stopped and use the offset value A at that time, you can calculate the off-set value Q' after starting.
(I) can be found as o' (I)=o (I) -o (Io)+A. Q(I0) is the value of the table.

If the offset value 0 (Io) at the current 1o is not in the table, it can be found by interpolation using the formula (2).

In this way, the offset value o(I
o) can be replaced by the actually measured offset value of 8 A. Thereby, even if there is a change over time in the output of the turning angular velocity sensor, accurate characteristics can be known.

If the current current I is a temperature not listed in the table, ■
Similar to the equation, Ik-1° can be used for interpolation.

The locator 1 uses the calculated offset value to correct the output data Δθ6 of the optical fiber gyro 43 by subtracting it from the output data Δθ6 of the optical fiber gyro 43 (step 2).

Then, the current orientation is determined using the corrected output data Δθ6 (step ■), the output data of the geomagnetic sensor 42 is compared with θH, and the more reliable data is selected.

To make this selection, for example, (I) JP-A-60-1.
As disclosed in Publication No. 22311, a geomagnetic sensor is normally used, and when the variation of the geomagnetic sensor within a specified time is greater than or equal to a set value, and the variation of the angular velocity sensor is less than or equal to the set value 9, the data of the angular velocity sensor is You may adopt
Alternatively, (2) the weighting may be averaged by calculating the dispersion values of the past output data of the optical fiber gyro 43 and the output data of the geomagnetic sensor 42, and applying a heavier coefficient to the pig with less variation.

Then, the current position of the vehicle is calculated from the azimuth data obtained as described above and the travel distance data obtained from the output of the vehicle speed sensor 41 (step (2)).

Of course, at this time, a map matching method may be adopted in which the estimated heading of the vehicle is corrected by comparing it with the road map data, evaluating the degree of correlation with the road map data, and setting the current heading of the vehicle on the road ( (Refer to Japanese Patent Application Laid-Open No. 63148115).

Next, a second example will be described. This example is
This corresponds to the invention set forth in claim 2. The orientation detection device of this embodiment is also applied to a position detection device for a vehicle, and its configuration is the same as that of the first embodiment, so a description thereof will be omitted.

In this embodiment, the fluctuation rate of the offset of the optical fiber gyro 430 is stored as a function α(I) of the current I, and the output of the optical fiber gyro is calculated from the previous offset value and the fluctuation rate of the offset corresponding to the stored current. We will explain how to correct this.

The offset drift amount of the optical fiber gyro 43 is
Varies with changes in ambient temperature.

Therefore, it is considered that the offset variation rate of the optical fiber gyro 43 is expressed by a function that depends on changes in temperature. In other words, if time is expressed as t, then dt
dt Here, α(T) is a coefficient (temperature fluctuation rate) that changes depending on the temperature, and the temperature T is determined by the temperature test of the optical fiber gyro 43 in advance. This can be converted into the current (2) measured by the injection current measuring circuit 45.

Therefore, it is stored in the offset memory 21 in the form of the table shown below.

1 Table 2 To obtain the fluctuation rate α(Ik), it may be calculated using the formula % Formula % using the offset O(lk) obtained in the same manner as in the first embodiment.

Since the output data Δθ6 of the optical fiber gyro 43 is obtained at regular intervals as described above,
Consider expressing the expression discretely.

Output data Δ of optical fiber gyro 43 imported this time
If the offset of θG is o (In), and the offset of the output data Δθ6 of the optical fiber gyro 43 taken last time is o (In-], ), then do (I)
/ d t →o (In) -o (In-1)d
I /dt −” (I n−I n−], ), so the formula (■) is O(ln)−o(In−1)+a(In)
-In-1) -... is expressed as ■. That is, the current offset value o (In) can be calculated using the previous offset value 0 (ln-1).

Therefore, using an accurate offset value when the vehicle is stopped as a reference, and using that value as an initial value, offset values can be successively determined using equation (2).

The exact offset value when stopped is, for example, the fifth
The correction value A shown in the figure may be used.

Thereafter, the locator 1 corrects the output data of the optical fiber gyro 43, uses the corrected output data to determine the current direction, and determines the current position of the vehicle, as in the first embodiment.

Next, a third embodiment corresponding to claim 3 will be described. In this embodiment, a 3 random access memory is used as the offset memory 21, and the offset value of the optical fiber gyro 43 is stored in a table in relation to the injection current. As will be described later, the memory 21 is preferably backed up by a battery so that it is updated each time the vehicle is run, resulting in a more accurate table. Table 3 shows the storage format of the table.

Table 3 One feature of this embodiment is that the contents of the above table are updated at any time based on the offset value while the moving body is stopped and the current injected into the optical fiber gyro 43 at that time.

This updating method will be explained in detail using FIG. The offset value is A between 4 o'clock t2 when stopping and ↑ 3 at the next start.
After starting, the offset o (I) appears again as shown by the broken line in the graph, and it changes over time according to the fluctuation of the temperature T, that is, the fluctuation of the current I injected into the optical fiber gyro 43. (.

Therefore, by measuring the injection current To during stoppage and using the offset value A at that time, the values in the table can be updated. Note that the initial value of the offset 0 (I) may be determined by performing a temperature test on the optical fiber gyro 43 in advance and using the injection current at that time and the off-cell l-11+11 constant value.

In this way, the offset value o(I
By replacing k) with the actually measured offset value A, even if the output of the optical fiber gyro 43 changes over time, the table can always correspond to the latest characteristics.

Next, an embodiment corresponding to claim 4 will be described.

In the first and third embodiments, the offset value of the optical fiber gyro 453 itself was stored in the table as a function of the injected current, but in this fourth embodiment, the optical fiber gyro 453 is stored as a function of the injected current. The temperature variation rate of the offset of 43 is stored as a function α(I) of the injection current I (see Table 4).

Furthermore, the temperature fluctuation rate α(I) calculated by the formula (2) in Table 4 is updated as needed based on the offset value while the moving object is stopped and the current injected into the optical fiber gyro 43 at that time.

In this way, α(lk) in Table 4 is updated as needed, so that the latest value can always be maintained regardless of changes in the optical fiber gyro 43 over time or aging.

Note that when updating α(Tk), if the previous value has already been written, for example, the average value with the previous value may be taken.

Further, as the initial value of α(Tk), for example, 0 may be given. If this is done, α(Tk) will remain 0 at a temperature that has not been experienced, and as long as the temperature remains at that temperature, the offset value will not change from the offset value A determined while the vehicle is stopped.

Although the orientation detection device having an offset correction function of the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the gist of the present invention. It is possible to apply

<Effects of the Invention> As described above, according to the invention described in claim 1, the offset value 0 (I) is stored and measured as a function value o (I) of the injection current I of the semiconductor light source of the optical fiber gyro. Read the offset value o (I) corresponding to the injection current at any time,
By using this read value to perform offset 71 correction, it is possible to perform correction including offset drift in real time.
A more accurate direction of the moving object can be determined.

Further, according to the second aspect of the invention, the rate of variation of the offset is stored as a function α(I) of the current I, the rate of temperature variation corresponding to the measured injection current is read out at any time, and the read value is used to By performing the offset correction, it is possible to perform correction including offset drift in real time, so as with the invention described in claim 1, it is possible to obtain a more accurate orientation of the moving object.

Further, according to the invention of claim 3, since the offset value stored as the function value o (I) of the injection current I of the semiconductor light source can be updated to the latest value, the optical fiber gyro Regardless of changes over time,
Accurate offset correction can be performed.

According to the invention set forth in claim 4, it is possible to maintain the fluctuation rate α(I) stored as a function of the injection current (I) at the latest value. Accurate offset correction can be performed regardless of changes in the gyro over time.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing a direction detection device having an offset correction function of the present invention, FIG. 2 is a block diagram showing the hardware configuration of a position detection device incorporating the direction detection device of the present invention, and FIG. FIG. 4 is a flowchart 1 showing the direction detection procedure, and FIG. 5 is a graph showing the instantaneous output of the optical fiber gyro. 1... Locator, 11... Optical fiber gyro, 1
2... Current measuring means, 13... Memory, 14...
Offset correction means, 15... Orientation determination means, 21.
...Offset memory, 43...Optical fiber gyro, 45...Two injection current measurement circuits

Claims (1)

[Claims] 1. An azimuth detection device that captures azimuth data obtained from the output of an optical fiber gyro and determines the current estimated azimuth of a moving body from those values and past estimated azimuths, comprising: a semiconductor for the optical fiber gyro; A current measuring means for measuring the injection current I of the light source, a memory storing the offset value of the optical fiber gyro as a function value o(I) of the injection current I, and reading the current from the current measuring means and storing it in the memory. an offset correction means for correcting the output of the optical fiber gyro using the stored offset value corresponding to the current; and an angular velocity Δθ of the moving body from the corrected output of the optical fiber gyro, and based on this, the current state of the moving body is determined. Estimated orientation θ
An azimuth detection device having an offset correction function, characterized in that it has an azimuth determination means for detecting. 2. The memory stores the fluctuation rate of the offset of the optical fiber gyro as a function α(I) of the current I, the offset correction means reads the current from the current measurement means,
2. The azimuth detection device having an offset correction function according to claim 1, wherein the output of the optical fiber gyro is corrected from the previous offset value and the fluctuation rate of the offset corresponding to the temperature stored in the memory. 3. In an azimuth detection device that captures azimuth data obtained from the output of an optical fiber gyro and calculates the current estimated azimuth of a moving object from those values and past estimated azimuths, the injection current I of the semiconductor light source of the optical fiber gyro is A current measuring means to be measured; a writeable and readable memory that stores the offset of the optical fiber gyro as a function value o(I) of the injection current I; and a memory that can read and write data to store the offset of the optical fiber gyro as a function value o(I) of the injection current I; memory updating means for updating the contents of the memory based on the current; offset correction means for reading the current from the current measuring means and correcting the output of the optical fiber gyro using an offset value corresponding to the current stored in the memory; The angular velocity Δθ of the moving object is determined from the corrected output of the optical fiber gyro, and based on this, the current estimated orientation θ of the moving object is determined.
An azimuth detection device having an offset correction function, characterized in that it has an azimuth determination means for detecting. 4. The memory stores the temperature variation rate of the offset of the optical fiber gyro as a function α(I) of the injection current I,
4. The azimuth detection device having an offset correction function according to claim 3, wherein the offset correction means corrects the output of the optical fiber gyro based on the previous offset value and the temperature fluctuation rate α(I) stored in the memory.