JPH0611353A - Setting method of initial value of horizontal plane of coordinate system of inertia reference device - Google Patents

Abstract

PURPOSE:To attain a horizontal state of a platform highly precisely in a short time by a method wherein an output of an accelerometer at the time when a power source is made is detected, a tilt angle of the platform is determined as a computed estimated value by integrating the output, the detection output is lowered by correcting the tilt angle, and the detection output is reduced gradually by repeating this operation. CONSTITUTION:An output thetar of an accelerometer 18 is inputted to integrators 30 and 32. By integrating twice the output thetar of the accelerometer 18 at this time point, a computed value of a tilt angle around a roll axis R of a platform 12 is obtained as an output of the integrator 32. When an estimated value of the tilt angle of the platform 12 is computed by a tilt angle estimating computation means 34, an operation of decreasing the estimated tilt angle is executed by a corrective gyro 14. By repeating this process in a plurality of times, the horizontal plane of the platform 12 can be set as an initial set value. A similar process for setting the initial value of the horizontal plane is repeated also for the tilt angle around a pitch axis and, after all, the platform 12 of an apparatus can be set initially in the state of the horizontal plane in a time shortened sharply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting an initial value of a coordinate system horizontal plane of an inertial reference device provided in a moving body such as a ship or an aircraft. In particular, the moving body starts to move from an anchoring position or a starting position. The present invention relates to a method for setting an initial value of a horizontal plane of a coordinate system in which initial setting of a horizontal plane of a coordinate system of the inertial reference apparatus is completed within a short time after the inertial reference apparatus is powered on.

[0002]

2. Description of the Related Art An inertial reference device equipped on a moving body such as a ship or an aircraft is used at any stage of operation of the moving body.
Once powered up, it is necessary to be able to deliver the correct inertial reference signal immediately. That is, the inertial reference device not only sends the navigation signal of the moving body, but also functions as a reference device for supplying initial data for inertial navigation to the inertial reference device such as an aircraft mounted on a surface ship. In order to have, it is necessary to quickly set the correct initial value at the start point of navigation and send the correct inertial reference signal.

In this case, the inertial reference device has an accelerometer and a gyro mounted on a platform, and the platform is generally mounted near the center of gravity of the moving body via a roll gimbal and a pitch gimbal. At the beginning of the navigation, first, as the initial value setting of the inertial reference device, the platform, that is, the azimuth gimbal is viewed in the horizontal plane from the viewpoint of the departure attitude of the ship at the mooring position of the ship and the attitude of the aircraft at the starting point of the airfield. Is required to be set to.

Conventionally, in the initial setting of the horizontal plane state of the platform of the inertial reference device, especially when the moving body is a ship, the inertial reference device is swayed due to the influence of waves even at the anchoring position of the moving body. In order to extract only the DC component from the noise component in the output of the accelerometer on this platform and use it as the tilt angle component of the platform, the output of the accelerometer is arithmetically averaged over a long period of time, and the average value is the actual value of the platform. The method used as the tilt angle component has been adopted.

[0005]

However, according to the arithmetic averaging method described above, for example, as a typical example, a wave acting on a ship at the time of mooring a quay has a standard deviation of 2 mmG with a main component of 10 (SEC) / cycle. There is acceleration noise (G: gravitational acceleration), and from this, the horizontal plane accuracy that is generally required for a highly accurate inertial reference device is 1 / 10,000 rad, that is, G × 1 / 10,000 = 0.1 mm as the detection value of the accelerometer. The time required for the arithmetic averaging process for extracting the detection values of the G accuracy is the time required for initializing the horizontal plane of the platform. At this time, as is well known, if the number of measurements is n and the spatial variance of the data is σ ₀ , the variance σ _{M of the} average value from the average value theorem of random values is σ _M = σ ₀ / √n ... 1) Using this equation (1), when σ _M ≦ 0.033 [millimeter G], that is, n with a standard deviation of 1σ is calculated, n = (σ ₀ / σ _M ) ² ··· (2) Therefore, substituting σ ₀ = 2 and σ _M = 0.033 into this equation (2) gives n = 3,600.

Now, the main component of noise is 10 SEC (= 0.1
Hz), so 10SEC x 3,600 = 36,00
It takes 0 seconds, that is, 10 hours.
That is, it means that the power must be turned on and stand by from 10 hours before the departure. The need for such a long time for setting the initial value has a problem that it is not useful in a situation where the user has to depart urgently.

Therefore, the object of the present invention is to rock especially at the anchoring point at the navigation start time such as a ship which rocks around the roll axis, pitch axis and yaw axis due to the influence of waves on the water surface. It is intended to provide a method of obtaining a highly accurate horizontal plane state of a platform in a short time when setting an initial value of a coordinate system of an inertial reference device mounted on a moving body.

Another object of the present invention is to set the initial value of the inertial reference device, that is, the current coordinate position of the moving body, that is,
By correcting the latitude in the coordinate system of the inertial reference device for the current latitude, the correction error amount of the inertial reference device due to the rotation of the earth is reduced as quickly as possible, the angular velocity of the inertial reference device is reduced, and the horizontal plane is set. An object of the present invention is to provide a method for setting an initial value of a horizontal plane of a coordinate system in an inertial device of a moving body, which improves the estimation accuracy of a tilt angle in a process to obtain a highly accurate horizontal plane state.

[0009]

SUMMARY OF THE INVENTION The present invention eliminates the conventional averaging operation, detects the output from an accelerometer mounted on the platform when the power of the inertial reference device is turned on, and is capable of instantly starting operation. The value is integrated twice, and the platform tilt angle at that point is calculated as an estimated value.
In order to correct the estimated tilt angle, the gyro is operated to correct the horizontal plane state of the platform through the gimbal mechanism in the direction of decreasing the tilt angle, and the detection output of the accelerometer is reduced. Then again, repeat the steps above based on the reduced accelerometer output,
In this way, the output of the accelerometer is gradually reduced to obtain the initial setting of the horizontal plane of the coordinate system of the inertial reference device.

That is, according to the present invention, in the method of initializing the coordinate system of the inertial reference device for a moving body having a platform equipped with a gyro and an accelerometer to a horizontal state at the beginning of the movement of the moving body, When the power is turned on at the initial stage of the movement of the body, the detected forces from the accelerometer are taken out, and the detected forces of the accelerometer are integrated twice to obtain an estimated value of the inclination angle of the platform, and the platform is obtained. A correction input is applied to the gyro to correct the estimated value of the tilt angle of the gyro to correct the platform toward the horizontal orientation side, and the gyro outputs a correction output over a predetermined gyro operation time, According to the correction output, the platform is corrected in the correction direction of the tilt angle to extract the detected force, estimate the tilt angle, The initial value of the coordinate system horizontal plane of the inertia reference device is set so that the operation of the gyro for platform correction and the platform correction operation are repeated a predetermined number of times as a step, thereby regressing the horizontal plane of the coordinate system of the inertia reference device. A method is provided. Hereinafter, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings.

[0011]

1 is a block diagram showing the construction of an inertial reference device constructed so that an initial value setting method of a coordinate system horizontal plane of the inertial reference device according to the present invention can be implemented. FIG. 2 is a block diagram showing the inertial reference device. FIG. 3 is a schematic mechanism diagram showing the gimbal configuration of FIG. 3, and FIG. 3 is a flowchart showing a process of setting an initial value of the horizontal plane of the coordinate system.

First, referring to FIG. 2, a moving body, in particular,
Ship hull part 8 (hereinafter, reference numeral 8 is a moving body)
, The gimbal configuration of the inertial reference device 10 mounted near the center of gravity of the ship is shown, and the roll axis, pitch axis, yaw axis and azimuth axis of the moving body 8 are respectively shown. , R, P, U. The inertial reference device 10 includes a platform (stabilization platform) 12 forming an azimuth gimbal in the center thereof, and two gyros 14, 16 and three accelerometers 18, 20, 22 are mounted on the platform 12. ing. The platform 12 is pivotally attached to the roll gimbal 24 through vertical shafts 12a and 12b that are perpendicular to the mounting surface and coaxial with the azimuth axis U, and are rotatably held around the azimuth axis U.
Further, the roll gimbal 24 has a pitch gimbal 26 through trunnion shafts 24a and 24b coaxially arranged with the roll shaft R.
And the roll axis R with respect to the pitch gimbal 26
It is held so as to be rotatable around. Further, the pitch gimbal 26 is rotatably held around the pitch axis P via support shafts 26a and 26b. An azimuth axis system servo mechanism including a rotation drive motor M _U and a rotation angle detector D _U capable of rotating the platform 12 around the azimuth axis U is provided at the ends of the vertical shafts 12a and 12b of the platform 12. ing.

Similarly, at the ends of the trunnion shafts 24a and 24b of the roll gimbal 24, a roll shaft servo composed of a rotation drive motor M _R and a rotation angle detector D _R capable of operating the roll gimbal 24 around the roll shaft R. A mechanism is provided. Further, the support shafts 26a, 26b of the pitch gimbal 26
A pitch axis servomechanism including a rotation drive motor M _P and a rotation angle detector D _P that can move the pitch gimbal 26 around the pitch axis P is provided at the end of the.

The former of the two gyros 14 and 16 mounted on the platform 12 rotates when the platform 12 moves relative to the moving body 8 around the roll axis and the pitch axis. The latter is arranged as a two-axis gyro that outputs an output signal according to the angle, and the latter responds to the rotation angle when the platform 12 moves relative to the moving body 8 around the azimuth axis and the pitch axis. It is arranged as a two-axis gyro that outputs the output signal. Therefore, three uniaxial gyros are provided, and these three gyros are arranged so as to output output signals corresponding to the respective rotation angles of the roll axis R, the pitch axis P, and the azimuth axis U. It goes without saying that it is also possible to

Further, the three accelerometers 18, 20, 22 respectively have an acceleration in the roll axis direction, an acceleration in the pitch axis direction,
It is arranged so as to respond to the acceleration in the azimuth axis direction and output an output signal corresponding to the absolute value of the acceleration. INDUSTRIAL APPLICABILITY The present invention can be applied as a method of quickly and quickly setting an initial value on the horizontal plane of the platform 12 of the inertial reference device 10 having the above-described configuration.

Referring now to FIG. 1, a configuration for initializing the horizontal plane of the platform 12 of the inertial reference device 10 having the above-described configuration with respect to the roll axis R and the pitch axis P is representative of both axes. 1 illustrates a mechanism for initializing one shaft system. Therefore, in the following, a process of setting the initial value of the horizontal plane of the platform 12 with respect to the roll axis R will be described as a typical example in a short time. Just do it.

Now, the initial value setting process of the horizontal plane of the coordinate system of the inertial reference device 10 of the moving body 8 is started by the acceleration detection by the accelerometer 18 which detects the acceleration in the roll axis R direction. In this case, the force F acting on the mass body 18a of the accelerometer 18 is such that the inclination angle of the platform 12 around the roll axis R is generally a small inclination angle δθ when the ship is at the port or the like. The output θr of 18 is F≈G
-Has a value proportional to δθ. Output θr of accelerometer 18
Are sequentially input to the two integrators 30 and 32. That is, the integration process is performed twice. Therefore, the output of the integrator 32 at the subsequent stage is integrated by the output θr of the accelerometer 18 at that time point twice, so that the roll axis R of the platform 12 is
The calculated value of the inclination angle of the circumference is obtained. However, in reality, the accelerometer 18 includes not only the acceleration component in the direction of the roll axis R but also various noise factors and components in which the moving body 8 is affected by waves . Therefore, it is next examined whether the calculated value Dr of the tilt angle regarding the platform 12 can be estimated as the tilt angle of the platform 12 at that time.

First, the process of integrating the output of the accelerometer 18 twice can be defined by the following equation (3). Dr = ∬ (θr) dt dt (3) where θr = θ _tilt × G + n _ACC (t) + n (t) + n _GYRO
(t) × G (4) where n (t): acceleration of the moving body 8, θ _tilt : deviation angle of the platform 12 from the horizontal plane, G: gravitational acceleration as described above, n _ACC ( t): noise of the accelerometer 18, n _GYRO (t): tilt noise due to gyro drift,

However, in the current state of the art, in each term of the above equation (4), n _ACC (t), that is, accelerometer noise can be suppressed to, for example, 30 μG or less, and therefore, as a result of twice integration. Can be almost ignored.
Also, n _GYRO (t) can be suppressed to 1 arc seconds or less, and this can be ignored. Furthermore, n (t) also has a large wave cycle of about 10 seconds when the ship is at a berth, etc. as described above, so even if the instantaneous acceleration value itself cannot be ignored,
It is a negligible value as the amount of swing angle after the process of two times integration. Therefore, the above equation (3) can be expressed as Dr≈∬ (θ _tilt × G) dt dt (5).

That is, the value of the result of the two-degree integration calculation of the output θr of the accelerometer 18 can be estimated to be the inclination angle of the platform 12 from the horizontal plane. By the way, the inertial reference device 10 is equipped with 2
The two gyros 14 and 16 always perform error correction of the platform 12 due to the rotation of the earth at the current position of the mobile unit 8. Therefore, even in the initial value setting process of the present invention, it is important to always perform the horizontal plane initial value setting of the platform 12 while adding the error correction due to the rotation of the earth. That is, the gyro 14 detects the deviation of the orientation of the platform 12 of the inertial reference device 10,
This azimuth deviation is added to the gyro 16 sensitive to the azimuth axis to correct the azimuth deviation of the platform 12.

The error in correcting the rotation of the earth to the gyro 16 due to the misalignment of the gyro 16 uses a high-precision gyro that is commercially available for the gyros 14 and 16. Therefore, the azimuth error εφ is, for example, However, Ω: Earth's rotation angular velocity = 15 (° / h), λ: Latitude, θ _GYRO : Drift rate of gyro. Now, for example, in the vicinity of Tokyo with a latitude of 35 °, the gyro drift rate is Since it is 0.0005 (° / h), from equation (5), Therefore, the earth rotation correction error [θ _C of the gyro 14 is [θ _C = Ω sin λ × εφ = 6.11 × 10 ^-6 (deg / h) = 0.02 (sec / h). Accordingly, the inclination angular velocity of the platform 12 is sufficiently smaller than the target accuracy of 6 seconds (sec) in the process of setting the initial value of the horizontal plane, and the inclination angle θ _TILT can be regarded as constant by the correction.

Therefore, in this state, the horizontal plane of the platform 12 is estimated. If the estimated time is 10 minutes, Dr =
1/2 (θ _TILT × G) t ² + n ″ (t) ... (6) Here, from the mooring conditions of the ship, n ″ (t) _MAX ≦ 15 (cm) From this, the estimated error ε θ of θ _{TILT TILT} (max) is And the required accuracy is 10 ⁻⁴ / 3 (rad) or less.

As described above, it is understood that the result of the two-degree integration calculation of the output of the accelerometer 18 can be used as the estimated value of the tilt angle of the platform 12. The estimation calculation is performed by the inclination angle estimation calculation means 34. When the inclination angle of the platform 12 is estimated from the estimation result, a correction for reducing the estimated inclination angle is performed by the gyro 14.
Run by.

That is, in FIG. 1, the estimated platform
Return the tilt angle of the home 12 around the roll axis R to the horizontal state
In order to allow the gyro 14, the torquer circuit 14a of the gyro 14 is disconnected.
The input is supplied via the conversion means 36. As a result,
Iro 14 performs pre-session operation, and its output is beeping.
It is output from the cut-off circuit 14b. Therefore, this output θ _G
Amplifier 38, stabilization network 40, servo amplifier
The motor M of the roll gimbal 24 via 42_RFee
When you do a duck back, the platform 12
Corrective action is performed in the direction of reduction.

After the platform 12 performs the tilt angle correction operation, the switching means 36 is once cut off, and the output of the accelerometer 18 is detected again for the state after the tilt angle correction, and the above-described two-degree integration calculation process is performed. Repeat again. And again,
The tilt angle of the platform 12 is estimated, and the estimated tilt angle of the platform 12 is corrected by the gyro 14 to correct the platform 12 to a horizontal plane. By repeating such a process a plurality of times, the horizontal plane can be set as the initial setting value on the platform 12.

As described above, the same initial value setting process for the horizontal plane is repeated around the pitch axis so that the platform 12 of the inertial reference device 10 can be finally initialized in the horizontal plane state. After the initial value setting is completed, the mode is switched to the navigation mode and the moving body 8 starts moving.

FIG. 3 is a flow chart of the process of initializing the horizontal plane of the platform 12 of the inertial reference device 10 described above. In addition, the description of the above-described embodiment has been described with respect to an example in which the initial setting of the inertial reference device is quickly performed when the moving body is a ship that is moored and rocks due to waves. When the aircraft parked at the airfield is swinging under the influence of the wind, the same can be applied to the initial value setting of the inertial reference device mounted on the aircraft.

[0028]

As is apparent from the above description, the present invention eliminates the conventional averaging operation, outputs from the accelerometer that is mounted on the platform when the inertial reference device is powered on, and can be instantly started. Is detected, the detected value is integrated twice, and the platform tilt angle at that time is obtained as a calculated estimated value. To correct the estimated tilt angle, the gyro is operated and the horizontal plane state of the platform is adjusted via the gimbal mechanism. Is corrected so that the tilt angle decreases, and the detection output of the accelerometer is reduced. Next, after correcting the azimuth deviation of the platform to reduce the error due to the rotation of the earth, the inclination angle is corrected again by the 2 degree integration step as described above based on the output of the accelerometer on the platform. Since the initial setting of the horizontal plane of the coordinate system of the inertia reference device is obtained while gradually reducing the output of the accelerometer, there is no factor that requires a long time in the calculation process as in the conventional case, and The time required for the initial setting of the horizontal plane of the coordinate system of the inertial reference device can be greatly shortened compared to the conventional time.

In this way, if the initial setting of the horizontal plane of the coordinate system of the inertial reference device of the moving body can be performed in a short time, the output data of the inertial reference device can be used as the reference data for other aircraft such as an aircraft oscillated from the moving body. Since the reference data can be supplied to the inertial reference device of the moving body in a short time, an emergency can be dealt with quickly.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an inertial reference device configured so that an initial value setting method of a coordinate system horizontal plane of the inertial reference device according to the present invention can be implemented.

FIG. 2 is a schematic mechanism diagram showing a gimbal configuration of the inertial reference device.

FIG. 3 is a flowchart showing an initial value setting process of a horizontal plane of a coordinate system.

[Explanation of symbols]

 8 ... Moving body 10 ... Inertia reference device 12 ... Platform 14 ... Gyro 16 ... Gyro 18 ... Accelerometer 20 ... Accelerometer 22 ... Accelerometer 30 ... Integrator 32 ... Integrator 34 ... Inclination angle estimation calculation means 36 ... Switching means

Claims (3)

[Claims] 1. A method for initializing a coordinate system of an inertial reference device for a moving body having a platform equipped with a gyro and an accelerometer to a horizontal state at the beginning of the moving start of the moving body. When the power is turned on, the detected force from the accelerometer is taken out, and the detected force of the accelerometer is integrated twice to obtain an estimated value of the tilt angle of the platform, and an estimated value of the tilt angle of the platform. Is applied to apply correction input to the gyro in order to correct the platform toward the horizontal orientation side to output a correction output for a predetermined gyro operation time from the gyro, and in accordance with the correction output of the gyro, the correction output is output. For correcting the tilt angle in the correction direction of the platform, the detection force is extracted, the tilt angle is estimated, and the platform is corrected. Gyro operation, repeated a predetermined number of steps times the correction operation of the platform as a single step, or more Te, the coordinate system horizontal initial value setting method of the coordinate system inertial reference unit which is characterized in that to return the horizontal plane of the inertial reference unit. 2. The coordinate system horizontal plane of the inertial reference device according to claim 1, wherein the azimuth deviation of the platform with respect to the current position of the moving body is detected by the gyro at each end of the step, and the azimuth deviation is corrected. Initial value setting method. 3. The initial value setting method for a coordinate system horizontal plane of an inertial reference device according to claim 1, wherein the tilt angle is a tilt angle about a roll axis of the platform and a tilt angle about a pitch axis.