Method for improving inertial navigation / satellite integrated positioning precision

Abstract

The invention relates to a method for improving inertial navigation / satellite integrated positioning precision, which comprises the following steps of: 1, measuring a relative distance between satellite navigation and inertial navigation, and transmitting the relative distance to equipment for storage; 2, measuring the relative distance between the inertial navigation and the measurement point, and transmitting to equipment for storage; 3, accessing a synchronization signal PPS to ensure that the type of the synchronization signal is effective; 4, latching the longitude, latitude and height of the current inertial navigation when the inertial navigation software receives the PPS signal; 5, after inertial navigation software receives the PPS signal, a first frame of satellite navigation positioning message is received, the current satellite navigation position is stored, satellite navigation rod arm compensation is carried out to the inertial navigation installation position, and then the inertial navigation positions in the step 4 are used for jointly calculating the quantity measurement of the Kalman filtering algorithm; 6, updating the Kalman filtering algorithm after the measurement is updated; 7, after the step 6 is carried out for a certain time, when inertial navigation outputs the position outwards, measuring point rod arm compensation is carried out, a compensation process is completed, and the step 4 to the step 7 are executed repeatedly in the follow-up process. The method can improve the precision of the measurement point position output by the inertial navigation / satellite combination algorithm.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace system technology - space vehicle technology - navigation, guidance and control technology, and mainly relates to algorithms and technical applications such as inertial navigation / satellite combined navigation positioning, data synchronization, delay compensation, and lever arm compensation, and specifically relates to a method for improving the accuracy of inertial navigation / satellite combined positioning. Background Art

[0002] Strapdown inertial navigation equipment is small in size and has a wide range of accuracy, and has been widely used in all aspects of military and national life. However, according to the actual application scenario, in order to prevent its accuracy from diverging too quickly, engineering often introduces external reference information (such as speed, position, etc.) into the strapdown inertial navigation equipment, adds appearance measurement to the algorithm, and uses the common estimation algorithm (Kalman filter estimation algorithm) to estimate the error, and then compensates it to the strapdown inertial navigation equipment, so as to achieve the purpose of using the strapdown inertial navigation equipment for a long time and with high accuracy.

[0003] Combined with the application of the combined positioning solution of inertial navigation and satellite navigation commonly used in engineering, it does not compensate for the arm between the inertial navigation and the satellite navigation or ignores the arm (assuming that the inertial navigation and the satellite navigation are installed at the same mathematical coordinate point) or only compensates for the arm between the inertial navigation and the satellite navigation, and ignores the measuring point arm between the inertial navigation and the measuring point, that is, the satellite navigation position used for inertial navigation for combined navigation is not compensated to the inertial navigation installation position or the position of the inertial navigation real-time output is not compensated to the measuring point, and the position of the inertial navigation output is the installation position of the inertial navigation itself. Therefore, there is an installation error in the reference position of the inertial navigation used for combined navigation, and there is a mathematical error that is artificially ignored between the position coordinates of the inertial navigation real-time output and the measuring point. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention proposes a method for improving the positioning accuracy of an inertial navigation / satellite combination.

[0005] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0006] A method for improving the positioning accuracy of an inertial navigation / satellite combination, characterized in that it comprises the following steps:

[0007] Step 1: Measure the relative distance between the satellite navigation and the inertial navigation, which is defined as the satellite navigation arm, and transmit it to the device for storage;

[0008] Step 2: Measure the relative distance between the inertial navigation and the measuring point. The relative distance is defined as the measuring point arm and is transmitted to the device for storage.

[0009] Step 3: Access the synchronization signal PPS to ensure that the synchronization signal type is valid;

[0010] Step 4: When the INS software receives the PPS signal, it locks the current INS longitude, latitude and altitude;

[0011] Step 5: After receiving the PPS signal, the inertial navigation software receives the first frame of satellite navigation positioning message, saves the current satellite navigation position, and performs satellite navigation arm compensation to the inertial navigation installation position, and then uses the inertial navigation position in step 4 to jointly calculate the quantity measurement of the Kalman filter algorithm;

[0012] Step 6: After the measurement is updated, the Kalman filter algorithm is updated.

[0013] After a certain period of time in step 7 and step 6, when the inertial navigation outputs the position to the outside, the measuring point arm compensation is performed to complete a compensation process, and steps 4 to 7 are repeated subsequently.

[0014] Moreover, in step 1 and step 2, the transverse lever arm is represented by X, the longitudinal lever arm is represented by Y, and the vertical lever arm is represented by H, forming a three-dimensional vector [X, Y, H].

[0015] Moreover, the synchronization signal in step three is a 1 Hz synchronization signal.

[0016] Furthermore, the strict restrictions on satellite navigation positioning effectiveness set in step 5 are:

[0017] 5) The positioning of the satellite guide itself is effective;

[0018] 6) The number of satellite positioning satellites is greater than 6;

[0019] 7) The satellite positioning PDOP value is less than 4;

[0020] 8) The position difference between the front and rear frames of the satellite navigation system itself is within 500 meters;

[0021] 5) The difference between the satellite navigation positioning position and the inertial navigation positioning position is within 500 meters

[0022] Moreover, in step five, the satellite navigation lever arm compensation is performed to the inertial navigation installation position using a multi-stage lever arm compensation method with a unified reference point.

[0023] Moreover, in step 5, the synchronous signal mechanism is used to calculate the position of the inertial navigation and satellite navigation at the same time. The formula is as follows:

[0024]

[0025]

[0026] Among them, the front inertial navigation position is [B ins ,L ins ,H ins ] T , the first frame of satellite positioning message is [Bsat ,,L sat ,H sat ] T , the quantity is Z P

[0027] Among them, X k represents the state vector of the system at time K, X k-1 represents the state vector of the system at time K-1, Z k represents the observation vector at time K, H k represents the state transfer matrix, V represents the observation noise, K k Represents the filter gain.

[0028] Moreover, in step 5, when the synchronization signal PPS is not available, an inertial navigation position buffer array is established to save the inertial navigation position of each solution cycle {[B ins ,L ins ,H ins ] T}1. . . n, the first frame of satellite navigation positioning message received after receiving the PPS synchronization signal sent by the satellite navigation [B sat ,L sat ,H sat ] T , then calculate the quantity Z P When , one of the cached inertial navigation positions 1...n is selected.

[0029] The advantages and positive effects of the present invention are:

[0030] The present invention describes a method for further improving the inertial navigation / satellite combined positioning. First, when an external position is introduced as a reference for measurement, satellite navigation lever arm compensation is added, and the measurement point of the satellite navigation is moved to the inertial navigation installation position by adding a lever arm compensation algorithm, which is equivalent to introducing the measurement point of the satellite navigation to the inertial navigation installation position; second, a synchronization signal is used to unify the position data of the satellite navigation and the real-time position of the inertial navigation at the same time, so that the accuracy of the measurement value calculated by the filtering estimation algorithm can be guaranteed, and a software compensation method when there is no synchronization signal is also proposed; third, when the inertial navigation outputs the measurement point position, an algorithm is used to compensate the lever arm from the inertial navigation to the measurement point, which is equivalent to moving the position measured by the inertial navigation to the measurement point; fourth, a set of limiting conditions for whether the satellite navigation is effective in actual engineering is added and confirmed through a large number of experiments, which can effectively prevent the problem that the wild value of the satellite navigation positioning is used as a reference and causes the abnormal slow convergence of the filtering algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the installation of the inertial navigation, satellite navigation and measurement points of the present invention;

[0032] Figure 2This is a principle block diagram of the strapdown inertial navigation Kalman filter of the present invention;

[0033] Figure 3 is a filtered estimation curve diagram of the azimuth angle according to an embodiment of the present invention;

[0034] Figure 4 It is a filtered estimation curve diagram of the azimuth angle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The structure of the present invention is further described below with reference to the accompanying drawings and by way of examples. It should be noted that the present examples are descriptive rather than restrictive.

[0036] A method to improve the positioning accuracy of inertial navigation / satellite combination, see Figure 1-Figure 4 , the invention point is: comprising the following steps:

[0037] Step 1: Measure the relative distance between the satellite navigation system and the inertial navigation system. The relative distance is defined as the satellite navigation arm and transmitted to the device for storage.

[0038] Step 2: Measure the relative distance between the inertial navigation and the measuring point. The relative distance is defined as the measuring point arm and transmitted to the device for storage.

[0039] Corresponding to the above steps 1 and 2, on the same carrier, due to the various devices used, their installation is planned in advance following certain rules. However, since there is data flow and coupling relationship between most of the devices, the installation error between the devices cannot be ignored. The following definitions are introduced: inertial navigation measurement point (i.e. inertial navigation installation position), satellite navigation measurement point (i.e. satellite navigation installation position) and measurement point (i.e. design or assessment position point). The three generally have an installation distance, such as Figure 1 shown.

[0040] The arm is used to describe the horizontal, vertical and vertical distances between two positions in the field of navigation and guidance. Its size is closely related to the vehicle. The arm on a vehicle is generally within a few meters, while the arm value on a large ship can generally reach tens of meters or even hundreds of meters. The horizontal arm is represented by X, the longitudinal arm is represented by Y, and the vertical arm is represented by H, forming a three-dimensional vector [X, Y, H].

[0041] Step 3: Connect the synchronization signal PPS and ensure that the synchronization signal type is valid, such as differential or TTL signal.

[0042] The synchronization signal is used to unify the data between two or more devices. It is a signal mark indicating the data at the same time. In satellite navigation applications, the commonly used one is 1PPS, that is, a 1Hz synchronization signal. It means that the synchronization signal is generated first, and then the positioning message at that moment is sent.

[0043] Step 4: When the INS software receives the PPS signal, it locks the current INS longitude, latitude and altitude.

[0044] Step 5. After receiving the PPS signal, the inertial navigation software receives the first frame of the satellite navigation positioning message, saves the current satellite navigation position, and compensates the satellite navigation arm to the inertial navigation installation position, and then uses the inertial navigation position in step 4 to jointly calculate the measurement of the Kalman filter algorithm.

[0045] The strict restrictions on the effectiveness of the above satellite positioning are:

[0046] In actual projects, we often encounter various obstructions such as bridges and buildings or electromagnetic environment influences, which result in satellite navigation positioning showing effectiveness but low positioning accuracy. In this case, its positioning precision factor even indicates that the defined accuracy is very high. Therefore, after verification by multiple actual engineering projects, the effective conditions for satellite navigation positioning that ensure fast convergence of the inertial navigation / satellite combination algorithm and do not affect the algorithm divergence are as follows, which can effectively detect whether the satellite navigation jumps to a large number and is unavailable.

[0047] 9) The positioning of the satellite guide itself is effective;

[0048] 10) The number of satellite positioning satellites is greater than 6;

[0049] 11) The satellite positioning PDOP value is less than 4;

[0050] 12) The position difference between the front and rear frames of the satellite navigation system itself is within 500 meters;

[0051] 5) The difference between the satellite navigation positioning position and the inertial navigation positioning position is within 500 meters

[0052] In order to prevent confusion in the concepts and operations of lever arm compensation for multiple devices, the present invention proposes a lever arm compensation method using inertial navigation as the reference point for all devices. That is, whether there are three devices or more devices, the lever arm itself is the relevant distance between two position points, but it is easy to cause confusion in actual use. Referring to the present invention, using the core inertial navigation as the reference point for all devices to measure the lever arms between multiple devices and the inertial navigation (such as the lever arm between the satellite navigation and the inertial navigation is referred to as the satellite navigation lever arm, the lever arm between the altimeter and the inertial navigation is referred to as the altimeter inertial arm, the lever arm between the odometer and the inertial navigation is referred to as the odometer lever arm, and the lever arm between the measurement point and the inertial navigation is referred to as the measurement point lever arm), and then the lever arm compensation is performed through multi-stage conversion with inertial navigation as the core. For details, see the following "Multi-stage lever arm compensation method with unified reference point"

[0053] Multi-level lever arm compensation method with unified reference point:

[0054] The latitude and longitude version of the arm compensation algorithm between two points is shown below, taking the arm compensation between the inertial navigation and the satellite navigation as an example. [X, Y, H] is the lateral distance, longitudinal distance and vertical distance from the satellite navigation to the inertial navigation in the B-frame system. is the current direction cosine matrix of the inertial navigation, [dX, dY, dH] is the distance difference in the northeast celestial coordinate system of the n-system navigation system. B is the latitude, L is the longitude, and H is the altitude. Rm is the radius of the earth's meridian circle, and Rn is the radius of the earth's meridian circle. When converting from the outside to the inertial navigation, subtraction compensation is used, and when converting from the inertial navigation to the outside, addition compensation is used.

[0055]

[0056] The lever arm measurement method with inertial navigation as the core described in the present invention is adopted, assuming that there are four devices and one measurement point, namely inertial navigation, satellite navigation, odometer, altimeter and measurement point, a total of five points. For example, to calculate the lever arm between the satellite navigation and the odometer, the lateral, longitudinal and vertical distances between the satellite navigation and the odometer are not directly measured, but the lever arm between the satellite navigation and the inertial navigation is measured, and the lever arm between the inertial navigation and the odometer is measured, and then after conversion, the lever arm compensation can be performed. The method is as follows:

[0057]

[0058] After the above two-level calculation, the satellite navigation position compensation can be transferred to the odometer position. This multi-level compensation method can effectively sort out the position conversion relationship between multiple devices and prevent the arm compensation confusion. This method is not limited to the algorithm of the present invention, and can also be used on large-scale carrier systems such as whole ships and whole vehicles. The present invention involves the satellite navigation positioning position arm compensation to the inertial navigation installation position, and the inertial navigation output position compensation measurement point arm to the measurement point position.

[0059] Kalman filter technology is a commonly used estimation algorithm for initial alignment, integrated navigation and combined calibration of strapdown inertial navigation systems. Its most basic purpose is to estimate the misalignment angle, velocity error and position error, and use it to correct the quaternion, solution velocity and solution position of the strapdown inertial navigation system, so that the calculated navigation coordinate system and the real navigation coordinate system are as close as possible. Figure 2 Shown

[0060] The inertial navigation / satellite combined Kalman filter algorithm of the present invention optimizes measurement calculation:

[0061] In the Kalman filter algorithm, the most important filter update involves the calculation of the external reference information measurement, and its accuracy will affect the rapidity of the filter estimate convergence and may even cause the filter estimate to diverge. To solve this problem, the present invention uses a synchronization signal mechanism to use the inertial navigation and satellite navigation position calculation measurement at the same time. As shown in the following formula, when the inertial navigation receives the PPS synchronization signal sent by the satellite navigation, it saves the current inertial navigation position [B ins ,,L ins ,H ins ] T , and then after receiving the PPS synchronization signal sent by the satellite navigation, the first frame of the satellite navigation positioning message [B sat ,,L sat ,H sat ] T , then calculate the quantity measurement Z P The Kalman filter update calculation is performed instead of the INS's own timing. That is, the external synchronization signal PPS control is used to compensate for the satellite navigation delay, thereby ensuring the accuracy of the INS / satellite combined Kalman filter algorithm measurement.

[0062]

[0063] Among them, X k represents the state vector of the system at time K, X k-1 represents the state vector of the system at time K-1, Z k represents the observation vector at time K, H k represents the state transfer matrix, V represents the observation noise, K k Represents the filter gain.

[0064] Inertial navigation / satellite combined Kalman filter algorithm measurement software processing method when there is no synchronization signal:

[0065] In actual engineering, when there is no synchronization signal PPS, the present invention proposes to establish an inertial navigation position cache array, save the inertial navigation position {[Bins, Lins, Hins] T} 1... n of each solution cycle, and receive the first frame of satellite navigation positioning message [Bsat, Lsat, Hsat] T received after receiving the PPS synchronization signal sent by the satellite navigation, and then select one of the cached inertial navigation positions 1... n for calculation when calculating the quantity measurement ZP. The simplest method is to directly use the inertial navigation position at the moment n-1 to participate in the calculation of the quantity measurement. In addition, according to the actual situation, the satellite navigation positioning delay is relatively fixed, so the position in 1... n can be tried to measure the effect to confirm the satellite navigation delay, or the satellite navigation manufacturer can be asked to confirm how many milliseconds the position delay represented by its positioning message is, so as to deduce the inertial navigation position at a certain moment in {[Bins, Lins, Hins] T} 1... n for Kalman filter update calculation, which can achieve the same effect as having a synchronization signal PPS.

[0066] Step 6: After the measurement is updated, the Kalman filter algorithm is updated.

[0067] After a certain period of time (such as 10 minutes or 15 minutes) in step 7 and step 6, when the inertial navigation outputs the position, the measuring point arm compensation is performed to complete a compensation process, and steps 4 to 7 are subsequently repeated.

[0068] In summary, the main innovative features of the present invention are as follows:

[0069] 1. The present invention proposes a lever arm compensation algorithm that uses inertial navigation as the reference point for all devices to prevent confusion in the concept and operation of lever arm compensation for multiple devices.

[0070] 2. In the inertial navigation / satellite combined Kalman filter estimation algorithm, the present invention utilizes the synchronous signal mechanism during its measurement and calculation, and uses the inertial navigation and satellite navigation positions at the same time to calculate the measurement, thereby improving the accuracy of the algorithm's external reference, thereby improving the rapidity of the combined algorithm's convergence, and avoiding the problem of abnormal bulge divergence and slow convergence of the filter curve. If the actual situation is not satisfied with the synchronous signal, the present invention proposes a software method: establish an inertial navigation position buffer array, and when the inertial navigation receives the satellite navigation positioning message, use a certain inertial navigation position in the buffer array to calculate the current inertial navigation and satellite navigation position calculation Kalman filter measurement. This method is much more accurate than using the inertial navigation itself to calculate the measurement at 1Hz, and can also improve the accuracy of the measurement to a certain extent.

[0071] 3. The present invention proposes the concept of introducing a measuring point (assessment point). When the inertial navigation system outputs position information externally, the lever arm compensation from the measuring point to the inertial navigation system position is added, which can further improve the position accuracy of the inertial navigation system output of the measuring point / assessment point.

[0072] 4. The present invention provides a set of effective restriction conditions for satellite navigation positioning, which can avoid the situation in the inertial navigation / satellite combined Kalman filter algorithm where the number of satellite navigation positioning hops has wild values ​​due to poor satellite navigation signals or other reasons, thereby causing abnormal bulges, divergence and poor convergence of the combined algorithm filter estimation, and can further improve the convergence speed of the combined algorithm.

[0073] The invention has been preliminarily applied in actual engineering projects, which has verified the effectiveness of the invention content. It can effectively reduce the convergence time of the inertial navigation / satellite combination algorithm in actual engineering and further improve the accuracy of the measurement point position output by the inertial navigation / satellite combination algorithm.

[0074] For the algorithm in the invention, a physical comparison test was conducted using real satellite navigation and inertial navigation in actual projects as follows:

[0075] Figure 3 and Figure 4 In the figure, the horizontal axis is in seconds and the vertical axis is in arc minutes. It is the azimuth error estimate in the inertial / satellite integrated navigation algorithm.

[0076] The left figure is the filtered estimation curve of the azimuth angle when synchronization and lever arm compensation are not used. The filter estimation stabilization time is about 910 seconds, about 15 minutes, and the subsequent estimation value has a tendency of slightly tilting instability due to the influence of reference position asynchronization and lever arm. The right figure shows the use of the lever arm compensation algorithm, the synchronous external reference position and the strict restrictions on the effective conditions of satellite guidance in the present invention. The azimuth filter estimation stabilization time is about 580 seconds, about 10 minutes, and the subsequent estimation value is also relatively stable due to the influence of the lever arm compensation algorithm and the synchronous external reference position in the present invention and the strict restrictions on the effective conditions of satellite guidance, and can be well applied in actual engineering projects.

[0077] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for improving the positioning accuracy of inertial navigation / satellite combination, characterized in that: The steps include: Step 1: Measure the relative distance between the satellite navigation and the inertial navigation, which is defined as the satellite navigation arm, and transmit it to the device for storage; Step 2: Measure the relative distance between the inertial navigation and the measuring point. The relative distance is defined as the measuring point arm and is transmitted to the device for storage. Step 3: Access the synchronization signal PPS to ensure that the synchronization signal type is valid; Step 4: When the INS software receives the PPS signal, it locks the current INS longitude, latitude and altitude; Step 5: After receiving the PPS signal, the inertial navigation software receives the first frame of satellite navigation positioning message, saves the current satellite navigation position, and performs satellite navigation arm compensation to the inertial navigation installation position, and then uses the inertial navigation position in step 4 to jointly calculate the quantity measurement of the Kalman filter algorithm; Step 6: After the measurement is updated, the Kalman filter algorithm is updated; After a certain period of time in step 7 and step 6, when the inertial navigation outputs the position to the outside, the measuring point arm compensation is performed to complete a compensation process, and steps 4 to 7 are repeated subsequently.

2. The method for improving the positioning accuracy of inertial navigation / satellite combination according to claim 1, characterized in that: In step 1 and step 2, the transverse lever arm is represented by X, the longitudinal lever arm is represented by Y, and the vertical lever arm is represented by H, forming a three-dimensional vector [X, Y, H].

3. The method for improving the positioning accuracy of the inertial navigation / satellite combination according to claim 1, characterized in that: The synchronization signal in step 3 is a 1 Hz synchronization signal.

4. The method for improving the positioning accuracy of the inertial navigation / satellite combination according to claim 1, characterized in that: The strict restrictions on satellite positioning effectiveness set in step 5 are: 1) The positioning of the satellite guide itself is effective; 2) The number of satellite positioning satellites is greater than 6; 3) The satellite positioning PDOP value is less than 4; 4) The position difference between the front and rear frames of the satellite navigation system itself is within 500 meters; 5) The satellite navigation positioning position and the inertial navigation positioning position are within 500 meters.

5. The method for improving the positioning accuracy of inertial navigation / satellite combination according to claim 1, characterized in that: In step 5, the satellite navigation arm compensation is performed to the inertial navigation installation position using a multi-stage arm compensation method with a unified reference point.

6. The method for improving the positioning accuracy of the inertial navigation / satellite combination according to claim 1, characterized in that: In step 5, the synchronous signal mechanism is used to calculate the position of the inertial navigation and satellite navigation at the same time. The formula is as follows: Among them, the front inertial navigation position is [B ins ,L ins ,H ins ] T , the first frame of satellite positioning message is [B sat ,,L sat ,H sat ] T , the quantity is Z P .

7. The method for improving the positioning accuracy of inertial navigation / satellite combination according to claim 1, characterized in that: In step 5, when there is no synchronization signal PPS, an inertial navigation position cache array is established to save the inertial navigation position of each solution cycle {[B ins ,L ins ,H ins ] T }1. . . n, the first frame of satellite navigation positioning message received after receiving the PPS synchronization signal sent by the satellite navigation [B sat ,L sat ,H sat ] T , then calculate the quantity Z P When , one of the cached inertial navigation positions 1...n is selected.

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