CN105424038A - Method for switching states of long-endurance inertial navigation system - Google Patents

Abstract

The invention provides a method for switching states of a long-endurance inertial navigation system. The method comprises steps as follows: step one, whether state switching should be performed on the inertial navigation system is judged according to the state switching evidence, and the state switching evidence is shown in the formula (6): the absolute value of the difference between Vx<c>(t) and Vx<c>(t-w) is larger than or equal to delta Vth (6), wherein Vx<c>(t) is a speed resolving value of the inertial navigation system at the current moment, w is the set window width, and delta Vth is the set threshold value; when the formula (6) is met, the inertial navigation system works in an undamped state, and otherwise, the inertial navigation system works in a damped state; step two, if state switching is required according to judgment in the step one, the inertial navigation system performs state switching, and dynamitic overshooting of the system is compensated. The state switching evidence is set according to the conclusion that the state overshooting error in the damped state is determined according to the speed variation, and judgment of the state switching is realized according to the set evidence. Wrong state switching can be effectively avoided, the dynamitic overshooting error after switching is remarkably reduced, and the performance of the inertial navigation system is improved.

Description

Method for switching states of long-endurance inertial navigation system

Technical Field

The invention relates to a method for switching states of an inertial navigation system during long-endurance, which is suitable for various inertial navigation systems and belongs to the technical field of inertial navigation.

Background

The inertial navigation system is a critical stable system, and is affected by an adder, a gyro error and the like, an oscillation error exists in the output of the inertial navigation system, and damping needs to be introduced into the inertial navigation system in order to suppress the oscillation error. And the introduction of the damping destroys the original relaxation tuning condition of the inertial navigation system, so that the acceleration of the carrier affects the misalignment angle. In order to avoid the adverse effect, the inertial navigation system needs to be switched between the undamped state and the damped state, when the carrier is in a static state, the inertial navigation system works in the damped state to suppress the oscillation error, and when the carrier is maneuvered, the inertial navigation system needs to be switched to the undamped state to avoid the error caused by the maneuver of the carrier.

When the inertial navigation system is switched to a damping state from undamped, an overshoot error can be generated, the performance of the inertial navigation system is reduced, and the overshoot error needs to be compensated in actual use.

Although the state switching overshoot can be compensated to some extent, it is not possible to achieve a fundamental elimination of the error. It is therefore still necessary to design a reasonable basis for the state switching to effectively control the various overshoot errors caused by damping. The traditional state switching basis is used for judging the state directly according to the acceleration of the carrier, the switching basis is lack of rationality and is easily influenced by external random interference signals, so that the inertial navigation system is frequently switched to the state, and a large overshoot error is caused.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for switching states of an inertial navigation system during long-term navigation.

The purpose of the invention is realized by the following technical scheme

A method for switching states of a long-endurance inertial navigation system comprises the following steps:

judging whether the inertial navigation system should carry out state switching according to a state switching basis, wherein the state switching basis is shown as a formula (6);

$|v_x^c\left(t\right)-v_x^c(t-w)|\&GreaterEqual;{\mathrm{\&Delta;v}}_{th}---\left(6\right)$

wherein,calculating a speed solution value of the inertial navigation system at the current moment, wherein w is a set window width, delta v_thSetting a threshold value, enabling the inertial navigation system to work in a non-damping state when the formula (6) is met, and otherwise enabling the inertial navigation system to work in a damping state;

step two, if the first step judges that the state switching is not needed, the operation of the first step is continued all the time; and if the first step judges that the state switching is needed, the inertial navigation system switches the state and compensates the dynamic overshoot of the system.

Has the advantages that:

the overshoot error is determined by the speed variation in the damping state, the set state switching basis is determined according to the result, and the judgment of state switching is realized according to the set basis.

Drawings

FIG. 1 is a flowchart illustrating a method for switching states of an inertial navigation system during long endurance according to the present invention;

FIG. 2 is a schematic diagram illustrating the effect of two switching criteria in a first maneuver according to an embodiment of the present invention;

FIG. 3 is a diagram illustrating a comparison of two switching criteria under a second scenario in accordance with an embodiment of the present invention;

FIG. 4 is a schematic diagram of a northbound loop state switching overshoot compensation scheme in an embodiment of the present invention;

FIG. 5 is a schematic diagram illustrating the effect of overshoot compensation by switching the north misalignment angle.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The basic principle of the invention is as follows: judging whether the inertial navigation system needs to switch states according to the carrier speed variation detected by the window, enabling the inertial navigation system to work in a non-damping state when the speed variation is larger than a set threshold, enabling the inertial navigation system to work in a damping state when the speed variation is smaller than the set threshold, and generating dynamic overshoot determined by a speed solution value at the switching moment when the inertial navigation system is switched from the non-damping state to the damping state, wherein the overshoot is compensated according to the scheme of the invention. In the embodiment of the invention, the zero offsets of three adding tables of the inertial navigation system are all 50 mug, and the standard deviation of random noise is 10 mug; the zero offset of the three gyroscopes is 0.1 degree/h, and the standard deviation of random noise is 0.01 degree/h.

The invention discloses a method for switching states of an inertial navigation system during long endurance, which comprises the following specific processes:

judging whether the inertial navigation system should carry out state switching according to a state switching basis, wherein the state switching basis is shown as a formula (6);

$|v_x^c\left(t\right)-v_x^c(t-w)|\&GreaterEqual;{\mathrm{\&Delta;v}}_{th}---\left(6\right)$

when the formula (6) is met, enabling the inertial navigation system to work in an undamped state, otherwise enabling the inertial navigation system to work in a damped state;

the state switching is as follows according to the design process:

in the damping state, the misalignment angle caused by the carrier maneuver is overshot by

$\frac{1}{s}\&lsqb;\left({\stackrel{\&CenterDot;}{v}}_x\right(s)-{\mathrm{\&phi;}}_y(s\left)\right)\frac{H_x\left(s\right)}{rs}-\frac{{\stackrel{\&CenterDot;}{v}}_x\left(s\right)}{rs}\&rsqb;={\mathrm{\&phi;}}_y\left(s\right)---\left(1\right)$

Is obtained from the formula (1)

${\mathrm{\&phi;}}_y\left(s\right)=\frac{H_x\left(s\right)-1}{{\mathrm{rs}}^2+{\mathrm{gH}}_x\left(s\right)}{\stackrel{\&CenterDot;}{v}}_x\left(s\right)---\left(2\right)$

Typically, the duration of the active maneuver of the vehicle is a small amount relative to the relaxation period of 84.4 minutes, so the acceleration input can be considered as a pulsed input signal, with

${\stackrel{\&CenterDot;}{v}}_x\left(s\right)=\mathrm{\&Delta;}v---\left(3\right)$

Wherein,

$\mathrm{\&Delta;}v={\&Integral;}_{t_1}^{t_2}{\stackrel{\&CenterDot;}{v}}_x\left(t\right)dt---\left(4\right)$

t₁，t₂respectively the starting time and the ending time of the carrier maneuver, then the delta v is the speed variation caused by the carrier maneuver, and the expression (4) is substituted into the expression (3) to obtain the speed variation

${\mathrm{\&phi;}}_y\left(s\right)=\frac{H_x\left(s\right)-1}{{\mathrm{rs}}^2+{\mathrm{gH}}_x\left(s\right)}\mathrm{\&Delta;}v---\left(5\right)$

(5) The formula shows that the instantaneous acceleration of the carrier is not the integral value of the acceleration in a period of time, namely the speed change amount, which determines the overshoot error magnitude in the damping state. Therefore, the traditional judging method taking the acceleration threshold value as the basis for state switching is not only lack of rationality, but also the traditional judgment method is easily influenced by random errors to cause state misjudgment, so that the inertial navigation frequently carries out state switching, and larger overshoot errors are caused.

According to the above theoretical analysis, the invention provides a carrier speed variation state switching basis based on window detection, which is described by a formula as follows:

$|v_x^c\left(t\right)-v_x^c(t-w)|\&GreaterEqual;{\mathrm{\&Delta;v}}_{th}---\left(6\right)$

and when the formula (6) is met, enabling the inertial navigation system to work in an undamped state, otherwise enabling the inertial navigation system to work in a damped state.

In the first embodiment, the state switching of the invention is verified according to the effect mainly under the condition of carrying out long-time weak maneuvering on the carrier. The initial speed of the carrier is 0, the inertial navigation system is kept in a damping state, and when 5 hours, the carrier starts to take 0.05m/s²The east acceleration of the carrier is maneuvered for 100s, and then the carrier keeps moving at a constant linear speed. A schematic diagram of the north misalignment angle curve when the conventional state switching criterion and the state switching criterion are adopted is shown in fig. 2, in which a black line is the north misalignment angle curve under the undamped condition, a blue line indicates the north misalignment angle curve when the conventional state switching criterion is adopted, and a green line is the north misalignment angle curve when the state switching criterion is adopted. Fig. 2 shows that when the carrier is in weak maneuvering for a long time, the conventional state switching method cannot make a correct judgment because the carrier does not feel a large acceleration, and the state switching method of the present invention can make a correct judgment.

The second embodiment of the invention mainly verifies the state switching effect under the condition that the carrier is subjected to temporary and strong maneuvering motion caused by external interference. The initial speed of the carrier is 0, the inertial navigation system is kept in a damping state, and when the speed is 5 hours, the carrier is at 0.2m/s²Is subjected to a short manoeuvre of 2s, while the carrier is then again subjected to a manoeuvre of 0.2m/s²The western acceleration of the vehicle performs a short maneuver of 2s, which roughly mimics the maneuver of the vehicle when subjected to transient disturbances. A schematic diagram of the north misalignment angle curve when the conventional state switching criterion and the state switching criterion of the present invention are used is shown in fig. 3, where the black line is the north misalignment angle curve under the undamped condition, the blue line indicates the north misalignment angle curve when the conventional state switching criterion is used, and the green line is the north misalignment angle curve when the conventional state switching criterion is used. Fig. 3 shows that when the carrier is subjected to a strong motion due to external disturbance, the conventional state switching method makes an erroneous judgment due to the large acceleration, while the state switching method of the present invention makes a correct judgment.

And step two, if the state switching is needed in the step one, the inertial navigation system switches the states and compensates the dynamic overshoot of the system.

The compensation scheme of the present invention is shown in fig. 4. Compared with the situation without compensation, the invention introduces-v at the point a_cx1The specific compensation principle is as follows:

before compensation, the overshoot process of the north misalignment angle is as follows:

$(\frac{{\mathrm{gH}}_x\left(s\right)}{{\mathrm{rs}}^2}+1){\mathrm{\&phi;}}_y\left(s\right)=\frac{H_x\left(s\right)}{{\mathrm{rs}}^2}{\&dtri;}_x\left(s\right)+\frac{H_x\left(s\right)-1}{rs}{v}_{cx1}\left(s\right)+\frac{1}{rs}{\mathrm{\&delta;v}}_{x1}\left(s\right)+\frac{{\mathrm{\&epsiv;}}_y\left(s\right)}{s}+{\mathrm{\&phi;}}_{y1}\left(s\right)---\left(7\right)$

after compensation, the overshoot process of the north misalignment angle is as follows:

$(\frac{{\mathrm{gH}}_x\left(s\right)}{{\mathrm{rs}}^2}+1){\mathrm{\&phi;}}_y\left(s\right)=\frac{H_x\left(s\right)}{{\mathrm{rs}}^2}{\&dtri;}_x\left(s\right)+\frac{1}{rs}{\mathrm{\&delta;v}}_{x1}\left(s\right)+\frac{{\mathrm{\&epsiv;}}_y\left(s\right)}{s}+{\mathrm{\&phi;}}_{y1}\left(s\right)---\left(8\right)$

comparing the formula (7) with the formula (8) shows that the method can compensate overshoot caused by the inertial navigation resolving speed at the switching moment. Three conditions that the carrier travels at a constant speed in the west direction at 0, 5m/s and 10m/s are respectively considered.

The third embodiment mainly tests the effect of the state switching overshoot compensation method designed by the present invention. The effect of the north misalignment angle state switching overshoot compensation is shown in FIG. 5, where the thin black solid line represents the north misalignment angle curve without damping; dot-dash lines, dotted lines and dashed lines represent north misalignment angle curves when the carrier velocity is 0, 5m/s and 10m/s, respectively, in the damped state; the results before compensation are shown in bold lines and the results after compensation are shown in thin lines for the same carrier speed. Since the curves are denser, in order to better show the compensation effect, a partial enlarged view is also given in fig. 5, in which no damping curve is drawn. Fig. 5 shows that the three thin lines are almost completely overlapped, which illustrates that the overshoot caused by the state switching is no longer related to the carrier speed after the compensation by the method of the present invention, and in addition, it can be seen from fig. 5 that the overshoot of the state switching can be compensated by the method of the present invention, and the compensation effect on the overshoot is more obvious when the carrier speed at the switching time is larger.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications may be made or equivalents may be substituted for some of the features thereof without departing from the scope of the present invention, and such modifications and substitutions should also be considered as the protection scope of the present invention.

Claims (1)

1. A method for switching states of an inertial navigation system during long endurance is characterized by comprising the following steps:

judging whether the inertial navigation system should carry out state switching according to a state switching basis, wherein the state switching basis is shown as a formula (6);

$|v_x^c\left(t\right)-v_x^c(t-w)|\&GreaterEqual;{\mathrm{\&Delta;v}}_{th}---\left(6\right)$

wherein,calculating a speed solution value of the inertial navigation system at the current moment, wherein w is a set window width, delta v_thSetting a threshold value, enabling the inertial navigation system to work in a non-damping state when the formula (6) is met, and otherwise enabling the inertial navigation system to work in a damping state;

and step two, if the state switching is needed in the step one, the inertial navigation system switches the states and compensates the dynamic overshoot of the system.