KR100278156B1 - Output of bow angle to angular velocity integrator - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bow angle output method of an angular velocity integrated gyro for detecting an instantaneous head azimuth angle of a vehicle for use in a vehicle, ship, aircraft, or the like. The present invention comprises the steps of receiving the azimuth azimuth data and the speed data from the GPS receiver; Storing the course azimuth data in a variable Hd [i] and storing speed data in a variable Sp [i]; Receiving angular velocity data from the FOG sensor; Integrating the angular velocity data and storing the relative rotation angle in a variable Rh [i]; If the value of the variable Sp [i] exceeds the minimum threshold speed, the variable Hd [i] value is output as heading [i]. If the value of the variable Sp [i] is less than the minimum threshold speed, the variable Heading [i- 1] and the value of Rh [i], and outputting a heading angle (Heading [i]). According to the present invention, the relative rotation angle is calculated by integrating the angular velocity output from the low-cost FOG sensor due to low resolution when the vehicle travels slowly, and by using this, the accurate heading angle of the vehicle can be obtained. It is possible to obtain an optical fiber gyro, and when applied to a vehicle geographic information system (GPS) or a speedboat navigation system, it is possible to obtain an affordable optical fiber gyro compass.

Description

Method of measuring instant heading angles of a rate integrating gyro

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bow angle output method of an angular velocity integrated gyro for detecting an instantaneous head azimuth angle of a vehicle for use in a vehicle, ship, aircraft, or the like.

In general, the technique of moving a vehicle from its starting point toward its intended destination is called navigation. Conventionally, the navigation method by observing the celestial body has been used. However, inertial navigation, which is capable of fully autonomous navigation, is widely used in modern times, which uses Newtonian dynamics to calculate the direction and distance of travel of the vehicle. It is.

In other words, the moving distance of the vehicle can be obtained by integrating the velocity according to Newtonian theory, and the velocity can be obtained by integrating the acceleration. Therefore, for inertial navigation, a "compass" for detecting the direction of the vehicle and an "accelerometer" for detecting the acceleration are essential.

Currently, compasses used in ships include magnetic compasses and gyro compasses. Magnetic compass uses the magnetic field of the earth and has the advantages of simple structure, no power supply, and no risk of failure.However, due to the difference between the magnetic axis of the earth and the magnetic axis forming the earth's magnetic field, it is caused by the different magnetic distribution in the region. There are drawbacks such as errors such as local magnetic, self-driving due to the iron of the ship.

Gyro compasses are widely used because they use the precession of the spinning top and are strong because of their strong north force and the ability to simply convert their bearings into electrical signals. However, the conventional gyro compass requires a high-speed rotating part, which has a disadvantage in that the structure is complicated, a failure is likely to occur, the starting time is long, and the price is expensive.

The optical fiber gyroscope used as a sensor of the optical fiber gyro compass is a kind of optical rotation sensor using the Sagnac effect. The sagnac effect refers to the effect of generating an optical path difference (ΔL) in proportion to the rotational angular velocity (Ω). When the phase difference is detected by using the optical interference phenomenon, the amount of rotated angular velocity can be known. These fiber optic gyroscopes can be divided into three classes according to their performance, which are listed in Table 1.

Item Grade 1 Grade 2 Grade 3 Dynamic range 0 to ± 30 ° / s 0 to ± 100 ° / s 0 to ± 100 ° / s Resolution ≤0.001。 / s ≤0.01。 / s ≤0.1。 / s Drift ≤0.1。 / h ≤10。 / h ≤20。 / h Scale Factor Linearity ≤0.5% ≤1% ≤1% Usage Aviation, Space, Geodetic Compass, etc. Auto guided vehicle, antenna control For vehicle navigation

Since the noise included in the angular velocity information output from the optical fiber gyroscope remains unremoved even after the signal processing, the noises cause distortion of the signal, thereby degrading the degree of the optical fiber gyroscope. Therefore, in order to increase the degree of the gyro compass described above, a time average should be made, and therefore, there is a problem in that instantaneous heading angles cannot be obtained with an optical fiber gyro compass.

Accordingly, the present invention has been made to solve the above problems, and provides a bow angle output method of the angular velocity integral gyro to obtain the instantaneous heading azimuth of the vehicle using an optical fiber gyroscope and a geographic information system (GPS). Its purpose is to.

The present invention for achieving the above object, the step of receiving the azimuth azimuth data and the speed data from the GPS receiver;

Storing the course azimuth data in a variable Hd [i] and storing speed data in a variable Sp [i];

Receiving angular velocity data from the FOG sensor;

If the value of the variable Sp [i] exceeds the minimum threshold speed, the value of the variable Hd [i] is output as heading [i]. If the value of the variable Sp [i] is less than or equal to the minimum threshold speed, the variable Hd [i− 1] and the value of Rh [i], and outputting a heading angle (Heading [i]).

1 is a view for explaining the sag effect,

2 is a view for explaining an operating characteristic of the FOG sensor;

3 is a view for explaining a true north measuring principle using a FOG sensor,

4 is an output waveform diagram of a FOG sensor configured as shown in FIG.

5 is a view for explaining the principle of measuring the orientation using the FOG sensor when the FOG sensor is located at any latitude,

6 is an output waveform diagram of a FOG sensor configured as shown in FIG.

7 is a configuration diagram of the angular velocity integration gyro according to the present invention,

8 is a flowchart illustrating a bow angle output method of the angular velocity integration gyro according to the present invention.

Explanation of symbols on the main parts of the drawings

71: GPS antenna 72: GPS receiver

73: FOG sensor 74: low pass filter

75: processor

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a typical FOG sensor is based on a sagnac effect that generates an optical path difference ΔL in proportion to the amount of rotation Ω, the radius R rotating at an angular velocity Ω about an axis perpendicular to the rotating plate. The optical path difference ΔL experienced by light rays traveling in opposite directions along the circumference when the rotating plate is present is represented by Equation 1 below.

(Where A is the area surrounded by the optical path, ie A = πR ² , and C _O is the luminous flux in vacuum).

With reference to Figure 1 will be described such a sag effect. At the starting point 1 on the circumference the same light travels along the circumference clockwise (CW) and counterclockwise (CCW). At this time, if the rotating plate is stopped (Ω = 0), the light traveling to the luminous flux Co will reach the starting point 1 after the same distance 2πR for the time t = 2πR / Co. On the other hand, when the rotating plate rotates at an angular velocity Ω, the light traveling in the counterclockwise direction (CCW) reaches point 2 after a shorter distance (Lccw) than the circumference 2πR as shown in Equation 2, and then clockwise (CW). The advanced light travels a longer distance (Lcw) than the circumference as shown in Equation 3.

L _CCW = 2πR-RΩt _CCW = c _CCW t _CCW Where R Ω is the tangential velocity of the ring, t _CCW is the time taken to advance the distance Lccw, and c _CCW in the vacuum is Co, the luminous flux.

L _CW = 2πR + RΩt _CW = c _CW t _CW (Where RΩ is the tangential velocity of the ring, t _CW is the time taken to advance the distance Lcw, and c _CW in the vacuum is Co, the luminous flux).

Using Equation 2 and Equation 3 as described above, the time difference between the clockwise direction and the counterclockwise direction can be obtained as shown in Equation 4.

Thus, time Δt The length of the light path ΔL Is equal to Equation 5, and the phase shift at this time is expressed as Equation 6.

(Where L is the length of the fiber, D is the diameter of the fiber coil, and λ is the wavelength of the light source running in vacuum).

Here, the operation characteristics of the general FOG sensor will be described with reference to FIG. 2. The inside of most FOG sensors contains optical fiber sensing coils symmetrically with the outer shape of the cylindrical structure.When the central axis of this sensing coil is placed on the z axis, the rotational angular velocity is detected when the z axis is rotated on the rotation axis. Output the voltage corresponding to If it is assumed that the output voltage at the stop is '0', the rotation angular velocities are opposite to each other when rotated clockwise and counterclockwise, respectively, so that output voltages having opposite polarities are obtained. However, the rotational angular velocity cannot be detected at all when the axis parallel to the sensing coil surface, that is, the x-axis or the y-axis is rotated. This is because the rotational angular velocity input does not affect the optical path difference in the optical fiber sensing coil due to the sag effect when rotation occurs along the axis parallel to the optical fiber sensing coil surface.

Referring to Figure 3 will be described the principle of detecting the earth rotation angular velocity for measuring true north by using the FOG sensor. If the FOG sensor is placed vertically with respect to the ground on the equator and placed in the position of ① in Fig. 3, the output voltage of the FOG sensor detects the maximum rotational angular velocity of the earth, so that the positive or negative voltage can be obtained. . It is assumed here that a positive maximum voltage is obtained, and the direction perpendicular to the optical fiber sensing coil plane is defined as the azimuth axis. That is, at the position ①, the azimuth axis points in the north direction and the output voltage gets the maximum value.

Next, turn the FOG sensor 90 ° clockwise and place it at the position ②. The azimuth axis points to the west and the output voltage is detected as '0'. Again, rotate it 90 ° clockwise and set it as ③. The azimuth axis points to the south side and the minimum value of the output voltage is detected. Rotate 90 ° clockwise once more and set as ④. The azimuth axis points to the east side and the output voltage is detected as '0'. Therefore, if the FOG sensor is rotated clockwise sequentially, the output waveform as shown in Fig. 4 can be obtained. If the FOG sensor is continuously rotated at constant speed, the output voltage of the sine wave can be obtained.

5 illustrates the principle of measuring orientation using a FOG sensor when the FOG sensor is located at any latitude rather than at the equator of the earth. At this time, when the FOG sensor is placed on the equator, the value corresponding to the orthogonal projection of the rotational angular velocity input value is input to the FOG sensor. In other words, if the output voltage when the FOG sensor is placed on the equator is V (t), in this case, when the latitude angle is Qe, the output voltage decreases slightly from the output value at the equator. V (t) cosQ _e 'Value is output. Therefore, if the FOG sensor is placed vertically on the earth at any latitude of the earth and continuously rotated at constant speed, an output signal of a sine wave is obtained as shown in FIG.

U _e = K _e sin (ω ₀ t + & _e )

here, K _e = kcosΘ _e : Output signal amplitude of FOG sensor,

ω ₀ = 2πf ₀ : Constant rotational angular velocity of FOG sensor

f ₀ : Constant speed of FOG sensor,

& _e : phase difference between true north direction and bow direction,

k: scale factor of the FOG sensor,

Θ _e : Indicates latitude.

Here, the scale factor denotes a voltage value output in proportion to an input rotational angular velocity. For example, when the scale factor of the FOG sensor is 210 mV / deg / sec, if the earth rotational angular velocity of 0.0042 deg / sec is input, the output signal of the FOG sensor becomes about 0.87 mV. In addition, when the latitude of the experiment site is about 35 degrees, the orthogonal projection component of the latitude of the earth's rotational angular velocity input to the FOG sensor is about 0.0034 deg / sec. The inherent noise characteristics of a FOG sensor include high frequency noise, random noise, and low frequency noise, drift noise. Here, random noise determines the resolution of the FOG sensor, and drift noise is the most important characteristic in the inertial navigation compass of a ship sailing for a long time.

If a gyro compass is manufactured using a high-resolution FOG sensor, it is possible to measure the earth's true north by detecting the rotational angular velocity of the earth. Therefore, the angular velocity integration gyro must be used in parallel to obtain the instant heading angle. The angular velocity integration gyro is a gyro that uses a low-sensitivity FOG that cannot detect earth rotation and detects and integrates rotational angular velocities to display the change in relative bow angle in degrees.

7 is a block diagram of the angular velocity integral gyro according to the present invention, Figure 8 is a flow chart for the bow angle output method of the angular velocity integral gyro according to the present invention.

Referring to FIG. 7, a GPS receiver 72 is configured to process a GPS signal input through the GPS antenna 71 to output path azimuth data and speed data of a vehicle, and a horizontal rotation angle is installed horizontally on the ground surface. FOG sensor 73 to output, a low pass filter 74 to block external noise included in the relative rotation angle output from the FOG sensor 73, and azimuth data input from the GPS receiver 72 And a processor 75 for processing the speed data and the relative angular velocity information input from the low pass filter 74 to output the heading azimuth of the vehicle.

Here, the above-described FOG sensor 73 uses an HGA-V model having good scale factor linearity. In general, when the vehicle travels at a speed exceeding the minimum critical speed (18 km / h), the azimuth data input from the GPS receiver 72 is output as a heading azimuth, but when the vehicle travels at a speed lower than the minimum critical speed, The rotation angle is detected by integrating the relative angular velocity of the FOG sensor 73 to output the heading azimuth.

Referring to FIG. 8, looking at the bow angle output method of the angular velocity integration gyro, step 81 is a step of initializing various variables such as Hd [i], Sp [i], Rh [i], and step 82. In this step, the azimuth azimuth data and the speed data are received from the GPS receiver 72.

In general, GPS satellites periodically detect a moving state of a vehicle and connect it to output a GPS signal including data such as the route, latitude, longitude, speed, and altitude of the vehicle. When the GPS signal is input to the GPS receiver 72 through the GPS antenna 71, the GPS receiver 72 processes the GPS signal and outputs the course azimuth data and the speed data. At this time, the path azimuth angle and the heading azimuth angle are the same in a car, but in a ship or a plane, the azimuth angle and the heading azimuth angle do not coincide with wind and sea current.

In step 83 the processor 75 stores the course azimuth data in the variable Hd [i] and stores the speed data in the variable Sp [i]. In step 84, the angular velocity data is input from the FOG sensor 73. In step 85, the processor 75 integrates the angular velocity data and stores the relative rotation angle in the variable Rh [i].

Step 86 detects whether the value of the variable Sp [i] is greater than 18 km / h. If the value of the variable Sp [i] exceeds the minimum critical speed (18 km / h), the flow proceeds to step 87 to output the heading angle. When the value of the variable Sp [i] is lower than the minimum threshold speed (18 Km / h), the flow proceeds to step 88 to output the heading azimuth angle.

In general, a heading azimuth, which is a course azimuth, can be obtained through a GPS signal as described above. When a vehicle is stationary or traveling at a speed lower than the minimum threshold speed, an error between a course azimuth provided by a GPS satellite and an actual heading azimuth Because of its large size, it is impossible to obtain a reliable gyro.

Therefore, in the present invention, when the vehicle travels at a speed faster than the minimum threshold speed, in step 87, the azimuth angle stored in the variable Hd [i] is stored in the variable Heading [i] indicating the heading angle, and then the heading azimuth angle is stored in step 89. Output On the other hand, when the vehicle travels at a slower speed than the minimum critical speed, the heading angle heading [i-1] and the relative rotation angle Rh [i] immediately before the step 88 are stored in the heading angle heading [i], and then in step 89 Output heading azimuth.

As described above, by outputting the course azimuth angle output from the GPS receiver as the heading azimuth angle and correcting it by using the relative rotation angle output from the FOG sensor, it is possible to always obtain a high heading azimuth angle even if the traveling speed of the vehicle is variable.

As described above, the present invention calculates the relative rotation angle by integrating the angular velocity output from the low-cost FOG sensor due to low resolution when the vehicle travels slowly, and uses the same to obtain an accurate heading angle of the vehicle. A high optical fiber gyro can be obtained, and when applied to a vehicle geographic information system (GPS) or a speedboat navigation system, a low cost navigation optical fiber gyro compass can be obtained.

Claims (1)

Receiving path azimuth data and speed data from a GPS receiver; Storing the course azimuth data in a variable Hd [i] and storing speed data in a variable Sp [i]; Receiving angular velocity data from an optical fiber gyroscope (FOG) sensor; Integrating the angular velocity data and storing the relative rotation angle in a variable Rh [i]; And If the value of the variable Sp [i] exceeds the minimum continuation, the variable Hd [i] is output as heading [i]. If the value of the variable Sp [i] is less than the minimum continuation, the previous heading angle Heading [ i-1] and the variable Rh [i] value by adding the heading angle (Heading [i]) outputting the bow angle output method of the angular velocity integrated gyro, characterized in that consisting of.