Outer-level damping method of strap-down inertial navigation system based on adaptive complementation filtering

A technology of complementary filtering and strapdown inertial navigation, applied in the field of navigation strapdown inertial navigation, can solve the problems of sensitive covariance, inability to obtain accurate accelerometer error and gyro drift, and no basis for theoretical derivation, etc., to achieve high stability Effect

Inactive Publication Date: 2018-04-20
HARBIN ENG UNIV
2 Cites 16 Cited by

AI-Extracted Technical Summary

Problems solved by technology

The traditional external horizontal damping network can well damp the Schuler oscillation error, but it will produce overshoot error when the damping is switched, and the greater the external reference speed error, the greater the overshoot
In addition, its parameters are obtained through a step-by-step trial method, and there is no basis for theoretical derivation
Therefore, the document "Horizontal Damping Algorithm of Strapdown Inertial Navigation System Based on Kalman Filtering Technology" (Chinese Journal of Inertial Technology, 2013, 21(3): 285-288) based on modern control theory, proposes a horizontal damping algorithm based on Kalman filtering technology. algorithm, but the Kalman filter algorithm is very sensitive to the select...
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Method used

Embodiment: in the long-time navigation of warship, due to the existence of Schuler oscillation, undamped inertial navigation system can not satisfy demand, the existence of gyro random drift can cause the oscillation error accumulated over time, traditional outer level The damping network can eliminate the oscillatory error, but it will produce an overshoot phenomenon whe...
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Abstract

The invention discloses an outer-level damping method of a strap-down inertial navigation system based on adaptive complementation filtering, which belongs to the technical field of navigation strap-down inertial navigation. In the method, an adaptive complementation filtering technology is employed to reduce an initial error and an oscillation error. During a process of designing damping network,a complementation filtering technology is used to obtain the higher-order damping network; a relation between a damping parameter and an outer reference speed error is searched according to the outerreference speed error changed with time, and an relation expression formula is obtained; the damping parameter is substituted into the damping network, the damping network is introduced to a solutionloop of inertial navigation to obtain a new solution equation. The damping of adaptive complementation filtering damping network eliminates a Schuler oscillation error, an overshoot error due to damping switching and decentralization even divergency phenomenon due to change of the outer reference speed, so that the outer-level damping method has higher stability and practicality.

Application Domain

Navigational calculation instruments

Technology Topic

Self adaptiveInertial navigation system +3

Image

  • Outer-level damping method of strap-down inertial navigation system based on adaptive complementation filtering
  • Outer-level damping method of strap-down inertial navigation system based on adaptive complementation filtering
  • Outer-level damping method of strap-down inertial navigation system based on adaptive complementation filtering

Examples

  • Experimental program(3)

Example Embodiment

[0043] Example: In the long-term navigation of a ship, due to the existence of Schuler oscillation, the undamped inertial navigation system cannot meet the demand. The existence of the random drift of the gyro will cause the oscillation error accumulated over time. The traditional external horizontal damping network can Eliminate the oscillating error, but it will produce overshoot when the damping is switched, and the overshoot is proportional to the difference between the system speed and the external reference speed. The present invention selects the damping based on the time-varying external reference speed error Parameters to achieve higher stability, the implementation process is as attached figure 1 ,Specific steps are as follows:
[0044] Step 1: Analyze the amplitude-frequency characteristics of the constant-speed network and the phase lag-lead network, and complement and match the two networks;
[0045] As attached figure 2 Shown is the error block diagram of the strapdown inertial navigation system single horizontal channel. It can be seen that the main error source of the Schuler loop is the external reference speed error δv r , The accelerometer measurement error Δ and gyroscope drift error ε, the speed error and position error are obtained as:
[0046]
[0047]
[0048] Among them, Q(s) is the damping network. Due to the existence of the three major error sources of the Schuler loop and the high-frequency interference signal output by the inertial instrument, the external reference speed error contains high-frequency measurement noise and low-frequency ocean current pollution. The damping network should meet the following characteristics:
[0049] (1) The transfer function of the correction network provides a phase lead in the mid-frequency band to ensure that the characteristic root of the closed-loop characteristic equation of the Schuler damping loop has a negative real part, so that the system is asymptotically stable.
[0050] (2) Under static conditions, The contribution of the constant external reference velocity error to the inertial indication position error and velocity error is zero, while the low-frequency component of the accelerometer measurement error and gyroscope drift error remains unchanged from the undamped state.
[0051] (3) In order to improve the ability to resist high-frequency interference, require So that the Schuler damping circuit has a high-frequency attenuation characteristic above the second order, which can effectively filter the external reference speed and the high-frequency interference signal output by the inertial instrument.
[0052] (4) When encountering strong ocean currents and severe sea conditions, or when navigating the naval vessel, the damping ratio should be reduced in time or even switched to undamped operation to eliminate the adverse effects of excessive external reference speed errors on the inertial indicator parameters.
[0053] Since the constant speed network has the characteristics of suppressing the high-frequency reference speed error, and the phase lag-lead network has high-frequency attenuation characteristics for the gyroscope drift accelerometer error, the two are highly complementary, so consider combining the two networks into complementary Filter, constant speed network Q A (s) and phase lag-advance network Q B (s) is:
[0054]
[0055]
[0056] Complementary plan as attached image 3 As shown, the above-mentioned complementary filtering double Schuler loop combination system can be equivalent to a single Schuler loop damping network, that is, Q A (s), Q B (s) Substituted into the position error, the following formula is obtained:
[0057]
[0058]
[0059] Based on the complementarity of the two, the following calculations are made:
[0060] δr A (s)×(1-W(s))+δr B (s)×W(s)
[0061] Then get the equivalent series correction network transfer function:
[0062]
[0063] Among them, W(s) is the second-order low-pass filter, namely
[0064] The reference speed error δv of the constant speed network, the phase lag-lead network and the second-order matching damping network r Compared with the position error characteristics of the accelerometer error Δ, the gyro drift characteristics are similar to the accelerometer error, as shown in Table 1:
[0065] It can be seen from the table that the frequency characteristic of the combined second-order matching network to the high and low frequency reference speed error is not less than 40dB/10deg, and for the accelerometer error and gyro drift, the low frequency has almost no attenuation, that is, the earth periodic oscillation is still exist. However, high frequencies have attenuation characteristics above the second order, which has obvious advantages.
[0066] Step 2: Design an adaptive complementary filter damping network:
[0067] When the strapdown inertial navigation system is switched from the undamped state to the damped state, the overshoot is proportional to the difference δv between the system speed and the external reference speed. Therefore, the single-channel external horizontal damping adaptive control of the system designed in this paper The plan is attached Figure 4 As shown, the adaptive mechanism is added to the inertial navigation system. The difference between the external reference speed measured by the Doppler log and the speed of the inertial navigation system is the input of the adaptive mechanism, and the parameter of the damping network is the adaptive mechanism For output, the adaptive damping system adjusts the damping network parameters in real time according to the external speed error through the adaptive mechanism.
[0068] Step 3: Establish the relationship between the damping parameter and the external reference speed error;
[0069] In order to establish the damping parameters, select the speed error as the objective function of the adaptive mechanism, namely:
[0070]
[0071] Among them, δv x ,δv y They are the difference between the east and north system speed and the external reference speed. According to the propagation characteristics of strapdown inertial navigation system, the difference between the speed of the system and the external reference speed has a great influence on the damping parameters.
[0072] Because v INS =v+δv INS ,v r =v+δv r ,δv=v r -v INS , Where δv,δv r ,v r ,v INS ,v are the difference between system speed and external reference speed, external reference speed error, external reference speed, system speed and real speed. Since the external reference velocity error measured by the Doppler log is easily affected by the environment, the transmission of the external reference velocity error to the system error needs to pass 1-Q(s), so it can be equivalent to transforming the external reference velocity error to find The optimal damping coefficient method minimizes the objective function. Specific implementation plan: select gyroscope drift and accelerometer error as 0.01°/h, 10 -4 g, and fix one of the damping parameters η = 0.5, and take μ = 1/2η = 0.5, and select the external reference speed error δv according to the overshoot and adjustment time of the platform error angle r The corresponding relationship with the optimal damping ratio ξ is shown in Table 2.
[0073] The fitting curve of the external velocity error and the damping ratio is:
[0074]
[0075] Step 4: Substitute the adaptive mechanism and the matched high-order damping network into the loop of the inertial navigation system to obtain a new control equation for the inertial navigation solution.
[0076] The damping coefficient ξ is substituted into the damping network according to the above formula, and the size of the damping parameter is selected in real time according to the change of the external speed for adjustment. Get the position control equation (latitude, longitude) of the inertial navigation system:
[0077]
[0078]
[0079] Speed ​​control equation (east speed, north speed):
[0080]
[0081]
[0082] Platform control equation (x, y, z axis):
[0083]
[0084]
[0085]
[0086] Where Q(s) is a damping network containing a damping parameter with time-varying reference speed error, R M ,R N Is the radius of the earth's meridian circle and the radius of the unitary circle, and Ω is the angular velocity of the earth's rotation. According to the above-mentioned control equation, the inertial navigation solution can be used to eliminate the overshoot of Schuler oscillation and state switching in position error, velocity error and attitude angle error error.
[0087] Implementation process:

Example Embodiment

[0088] Example 1: Set at 45.7796°N, 126.6705°E, the carrier running speed is 5m/s, the damping coefficient ξ is substituted into the damping network, η=μ=0.5, the simulation parameter settings are shown in Table 3.
[0089] Set the external reference speed error according to the following formula, the simulation is as attached Figure 5 Shown:
[0090]
[0091] Since the ship's working mode is related to the accuracy of the external reference speed, when the external reference speed is not accurate, only the state of no damping is performed. Select the external reference speed error according to the above formula, at t=5h, switch from undamped state to damped state; t=12h switch from damped state back to undamped state; t=18h, switch from undamped state to damped state. Since the speed error of the inertial navigation system corresponding to different time points is different, in order to verify the algorithm, the damping switching process at different time points is realized, and the simulation is performed according to the above settings. The obtained speed error and horizontal attitude angle error are as attached. Image 6 with 7 Shown.

Example Embodiment

[0092] Embodiment two:
[0093] In order to verify that the adaptive network based on complementary filtering has engineering applicability, PHINS is connected with H/H HZ001 inertial navigation system, PHINS is used as a benchmark, and an experiment is carried out at a certain location (45.7796°N, 126.6705°E). The initial pitch angle , The roll angle and the heading angle are -0.016°, -0.398°, and 253.11°, respectively. The damping coefficient ξ is substituted in, and the external Doppler reference velocity error is as follows:
[0094] δv r =0.5×sin(2πt/18h)kn
[0095] The constant drift and noise of the gyroscope and accelerometer are shown in Table 3. The experimental data is analyzed and processed offline, and the state conversion is performed at 1 hour. The experimental results are obtained. The speed error and attitude angle error are as attached. Figure 8 with 9 Shown.
[0096] Implementation Effect:
[0097] Example A simulation data verifies the feasibility of the curve fitting. There is no overshoot in the speed error and the attitude angle error at the switch between 5 hours and 18 hours, and the Schuler oscillation is suppressed in the damping state. When the external reference speed error changes at any time, the optimal damping parameter can be selected for damping at any time, which verifies the feasibility of the algorithm to switch at different time points. Therefore, the damping network based on adaptive complementary filtering can be applied to strapdown inertial The simulation of the guidance system.
[0098] From the solution results of the second embodiment, it can be seen that the damping switch is performed at 1 hour, and the damping network based on adaptive complementary filtering proposed in this paper does not overshoot the error at the switch. The speed error graph shows that the method in this paper does not deviate from the original central value. Therefore, the adaptive complementary filtering mechanism can be applied in practical engineering applications, and it is practical compared with traditional damping methods and complementary filtering networks.
[0099] It is not difficult to see from the above embodiments that the damping network based on adaptive complementary filtering proposed by the present invention uses the change of the external reference speed error as the basis for selecting the damping coefficient on the basis of complementary filtering, and the optimal damping coefficient is selected in real time. Timely variable damping network. The feasibility of the algorithm is verified by simulation, and the overshoot error and phase deviation during Schuler periodic oscillation and state transition are effectively suppressed, and the dynamic performance of the inertial navigation system is significantly improved.

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