A method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver, an electronic device, and a storage medium

Abstract

The present invention provides a method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver, comprising the following steps: calculating the pitch angle and the roll angle, initializing the INS, updating the INS strapdown algorithm, calculating the velocity increment, and calculating the heading angle. The present invention relates to an electronic device and a storage medium for executing a method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver. The method provided by the present invention is simple and easy to implement in engineering. During the coarse alignment process, the heading angle can be calculated through the velocity increments provided by the IMU and the GNSS respectively, effectively reducing the errors brought by the INS velocity update and the observation noise of the GNSS, without involving complex filtering calculations and adjustment processing. The operation mode is flexible and simple, without requiring the forward direction of the carrier to be consistent with the longitudinal axis of the carrier, and at the same time, without requiring the carrier to provide a large maneuver, which is very suitable for the RTK measurement operation scenario.

Description

Technical Field

[0001] The present invention relates to the technical field of GNSS / MEMS-INS integrated positioning, and particularly relates to a method for obtaining an initial heading value of a handheld GNSS / MEMS-INS receiver, an electronic device, and a storage medium. Background Technique

[0002] The GNSS / MEMS-INS integrated positioning technology can determine the attitude and position of an RTK receiver. High-precision position information is generally obtained by RTK positioning technology, while attitude information needs to be obtained by GNSS / MEMS-INS integrated solution. Once high-precision attitude information is determined, high-precision RTK tilt measurement operations can be carried out. The GNSS / MEMS-INS integrated solution needs to complete the initial alignment work, that is, to determine the three Euler angles of the carrier attitude, including the heading angle ψ, the pitch angle θ, and the roll angle γ. In the present invention, the "north-east-up" geographic coordinate system is defined as the navigation coordinate system (n system), and the carrier coordinate system (b system) is defined with the horizontal axis pointing to the right, the longitudinal axis pointing forward, and the vertical axis pointing upward. Define the matrix indicating the direction cosine matrix of the carrier coordinate system (b system) relative to the navigation coordinate system (n system), and the matrix indicating the direction cosine matrix of the horizontal coordinate system (h system) relative to the navigation coordinate system (n system), and the matrix indicating the direction cosine matrix of the carrier coordinate system (b system) relative to the horizontal coordinate system (h system). Consists of and two parts, as shown in formula (1). The matrix is determined by the heading angle ψ, as shown in formula (2), and the matrix is determined by the pitch angle θ and the roll angle γ, as shown in formula (3).

[0003]

[0004]

[0005]

[0006] The initial alignment work includes two parts: horizontal attitude alignment and heading alignment. The horizontal attitude alignment determines the pitch angle θ and the roll angle γ, and the heading alignment determines the heading angle ψ. The horizontal attitude alignment is relatively simple and can be derived and calculated by an accelerometer based on the specific force equation when the vehicle is in a stationary state. It can also be achieved by filtering with an accelerometer and a gyroscope based on the AHRS (attitude heading reference system) algorithm at low speeds. The heading alignment is relatively complex, and the main methods are as follows: (1) Heading alignment based on geomagnetic measurement. After the horizontal attitude alignment is completed, the b-frame geomagnetic field vector measured by a three-axis magnetometer is reduced to the horizontal h-frame, and then it is matched with the n-frame geomagnetic vector calculated based on the geomagnetic model to solve for the azimuth angle and complete the heading alignment; (2) Heading alignment based on horizontal position matching. When the traveling direction of the vehicle is consistent with the longitudinal axis direction of the vehicle, the coordinates of each position point in the traveling direction of the vehicle are estimated using GNSS (Global Navigation Satellite System) positioning technology, and then the angle between the longitudinal axis of the vehicle and the geographic north direction can be determined, and further the heading angle of the vehicle can be determined; (3) Heading alignment based on horizontal velocity matching. When the traveling direction of the vehicle is consistent with the longitudinal axis direction of the vehicle, the three-dimensional velocity of the vehicle in the Earth-centered Earth-fixed system is estimated using GNSS (Global Navigation Satellite System) velocity measurement technology, and then the velocity vector in the vehicle navigation system (n-frame) can be obtained based on coordinate transformation, and the angle between the longitudinal axis direction of the vehicle and the geographic north direction can be determined, and further the heading angle of the vehicle can be determined; (4) Heading alignment based on horizontal acceleration matching. The three-dimensional velocity of the vehicle in the Earth-centered Earth-fixed system is obtained using GNSS (Global Navigation Satellite System) velocity measurement technology, and then the velocity vector in the vehicle navigation system (n-frame) is obtained based on coordinate transformation. The acceleration of the vehicle in the n-frame is calculated using the velocities of adjacent epochs. It is matched with the accelerometer observation value transformed to the h-frame through the horizontal attitude matrix to solve for the heading angle of the vehicle and complete the heading alignment work.

[0007] The principle of realizing heading alignment based on geomagnetic measurement is relatively simple and not complicated to implement. However, the intensity of the earth's magnetic field is generally small under normal circumstances, and geomagnetic measurement equipment is extremely vulnerable to environmental interference. It is necessary to calibrate the magnetometer before operation, and generally the ellipsoid calibration method is used to remove the influence of magnetic interference. However, in the actual operation process, the environment is complex and changeable, and the calibration parameters at point A are very likely not applicable at point B. The heading alignment based on geomagnetic measurement has the characteristic of unstable accuracy. The methods of realizing heading alignment based on horizontal position matching and based on horizontal velocity matching are simple and easy to implement. The principle is to determine the heading angle by using the vector projection of GNSS information in the navigation coordinate system. However, the prerequisite conditions both require that the traveling direction of the carrier is consistent with the longitudinal axis direction of the carrier coordinate system, which limits the operation mode of the GNSS receiver and results in poor user experience. In the conventional RTK operation, the GNSS receiver is generally installed on a centering rod. In actual operation, the RTK panel may face any direction, and the angle between the user's forward direction and the longitudinal axis of the carrier may change at any time. The heading angles obtained by using horizontal position matching and horizontal velocity matching are not the true carrier heading angles. The method based on horizontal acceleration matching does not require the traveling direction of the carrier to be consistent with the longitudinal axis direction of the carrier, but it requires the carrier to provide a large acceleration. The GNSS acceleration cannot be directly obtained, and there is a time delay in obtaining the acceleration by means of filtering. In addition, the acceleration time window of handheld devices is generally short, and the time matching between the IMU acceleration and the GNSS acceleration is a major difficulty. Therefore, it is difficult to implement the method of realizing rough alignment of the flight path based on horizontal acceleration matching. Summary of the Invention

[0008] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver, which is a method for rough alignment of the heading suitable for RTK tilt measurement, that is, to calculate the heading angle based on the velocity increment in different coordinate systems. This method is not affected by external magnetic field interference. During the initialization process, it does not require the traveling direction of the carrier to remain at a constant angle with the axis of the inertial module, and it is suitable for the operation mode of handheld RTK.

[0009] The present invention provides a method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver, including the following steps:

[0010] Calculate the pitch angle and roll angle, and solve the original data collected by the IMU in the stationary state to obtain the pitch angle and roll angle at each epoch;

[0011] INS initialization. At the starting moment of rough alignment of the heading, the position provided by RTK is used as the initial position of INS, the speed provided by RTK is used as the initial speed of INS, the pitch angle and roll angle at the corresponding epoch are used as the initial values of the pitch angle and roll angle in the INS strapdown solution, and the initial value of the heading angle in the INS strapdown solution is assigned as 0. At this time, it is considered that the y-axis in the IMU coordinate system points to the false north.

[0012] INS strapdown algorithm update. According to the attitude update, speed update, and position update formulas, the speed solved by the IMU at each epoch is obtained.

[0013] Calculate the speed increment. Select the initialization interval of rough alignment of the heading and calculate the GNSS speed increment and IMU speed increment in the interval.

[0014] Calculate the heading angle. Calculate the heading angle at the starting moment according to the GNSS speed increment and IMU speed increment at the starting and ending moments.

[0015] Furthermore, in the step of calculating the pitch angle and roll angle, the formula for resolving the original data collected by the IMU in a stationary state is:

[0016]

[0017]

[0018] where θ is the pitch angle and γ is the roll angle. represents the acceleration in the x direction in the b system. represents the acceleration in the y direction in the b system. represents the acceleration in the z direction in the b system.

[0019] Furthermore, in the step of INS strapdown algorithm update, the attitude differential equation:

[0020]

[0021] where is the constructed skew-symmetric matrix, and represents the angular velocity output by the gyroscope. represents the attitude transformation quaternion from the b system to the n system. represents the conjugate quaternion of

[0022] Within the sampling interval [k - 1, k], the attitude differential equation is solved by the Picard algorithm to obtain:

[0023]

[0024]

[0025] Among them, respectively represent the attitude transformation quaternions at times k and k - 1 in the local navigation system. Δθ k = |Δθ k |, represents the change in the attitude quaternion from time k - 1 to time k.

[0026] Furthermore, in the INS strapdown algorithm update step, the velocity differential equation:

[0027]

[0028] Among them, represents the specific force output by the accelerometer, v n , g n respectively represent the velocity vector and the gravity vector in the local navigation system;

[0029] The velocity differential equation is integrated within [k - 1, k] to obtain:

[0030]

[0031] Among them, respectively represent the velocities at times k - 1 and k in the local navigation system; represents the velocity increment generated by the specific force. Assuming that the acceleration is linearly varying between times k - 1 and k, the approximate expression for is obtained as:

[0032] is called the rotation effect compensation term, is called the paddling effect compensation term; is the velocity increment compensation term generated by the combined action of Coriolis acceleration, gravitational acceleration, and centripetal acceleration.

[0033] Furthermore, in the INS strapdown algorithm update step, the position differential equation:

[0034]

[0035] Among them, R N represents the radius of curvature of the prime vertical, R M represents the radius of curvature of the meridian;

[0036] Integrate the position differential equation within the sampling interval [k - 1, k] to obtain:

[0037]

[0038] wherein, respectively represent the positions at times k - 1 and k in the local navigation system.

[0039] Furthermore, in the step of calculating the velocity increment, the velocity increment Δv of the INS between two consecutive epochs is obtained according to the attitude update, velocity update, and position update formulas: IMU (t k-1 , t k ), and the velocity increment Δv of GNSS between two consecutive epochs is obtained by taking the difference between two consecutive epochs: GNSS (t k-1 , t k ).

[0040] Furthermore, in the step of calculating the heading angle, the formula for calculating the heading angle at the starting moment according to the GNSS velocity increment and IMU velocity increment at the starting and ending moments is:

[0041]

[0042] wherein, ψ0 represents the heading angle at time t0, Δv GNSS,E (t0, t1) represents the velocity increment of GNSS in the E direction from time t0 to t k moment, Δv GNSS,N (t0, t1) represents the velocity increment of GNSS in the N direction from time t0 to t k moment, Δv IMU,x (t0, t k ) represents the projection of the velocity increment resolved by the IMU from time t0 to t k moment on the X-axis of the horizontal coordinate system, and Δv IMU,y (t0, t k ) represents the projection of the velocity increment resolved by the IMU from time t0 to t k moment on the Y-axis of the horizontal coordinate system.

[0043] An electronic device, comprising: a processor;

[0044] a memory; and a program, wherein the program is stored in the memory and configured to be executed by the processor, and the program includes a method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver.

[0045] A computer-readable storage medium stores a computer program thereon, and the computer program is executed by a processor to implement a method for obtaining an initial heading value of a handheld GNSS / MEMS-INS receiver.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] The present invention proposes a method for obtaining an initial heading value of a GNSS / MEMS-INS receiver. This method solves the problem of rough heading alignment in the RTK scenario. The initial heading value obtained by this method has high accuracy. Based on this initial heading value, traditional heading filtering alignment can be performed to improve the efficiency and stability of heading alignment.

[0048] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it in accordance with the content of the specification, the following describes the preferred embodiments of the present invention in detail in conjunction with the accompanying drawings. The specific implementation manners of the present invention are given in detail by the following embodiments and their accompanying drawings. Description of the Drawings

[0049] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0050] Figure 1 is a method for obtaining an initial heading value of a handheld GNSS / MEMS-INS receiver according to the present invention;

[0051] Figure 2 is a schematic diagram of the conversion between the n-system and the b-system according to the present invention;

[0052] Figure 3 is a schematic diagram of the heading angle according to the present invention. Detailed Description of the Preferred Embodiments

[0053] Next, in combination with the accompanying drawings and specific implementation manners, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0054] A method for obtaining an initial heading value of a handheld GNSS / MEMS-INS receiver, as Figure 1 shown, includes the following steps:

[0055] Calculate the pitch angle and roll angle, and perform calculations on the original data collected by the IMU in the stationary state to obtain the pitch angle and roll angle at each epoch;

[0056] INS initialization. At the starting moment of rough alignment of the heading, the position provided by RTK is used as the initial position of INS, the speed provided by RTK is used as the initial speed of INS, the pitch angle and roll angle at the corresponding epoch are used as the initial values of the pitch angle and roll angle in the INS strapdown solution, and the initial value of the heading angle in the INS strapdown solution is assigned as 0. At this time, it is considered that the y-axis in the IMU coordinate system points to the false north.

[0057] INS strapdown algorithm update. According to the attitude update, speed update, and position update formulas, the position, speed, and attitude calculated by the IMU at each epoch are obtained. In this embodiment, the INS strapdown algorithm update includes three processes, namely attitude update, speed update, and position update. Attitude update is the prerequisite for speed update and position update. In this embodiment, the quaternion method is used to update the attitude. Attitude differential equation:

[0058]

[0059] Where, is the constructed skew-symmetric matrix, and represents the angular velocity output by the gyroscope, as Figure 2 shown, represents the attitude transformation quaternion from the b system to the n system, represents the conjugate quaternion of

[0060] Within the sampling interval [k - 1, k], the attitude differential equation is solved by the Picard algorithm to obtain:

[0061]

[0062]

[0063] Where, respectively represent the attitude transformation quaternions at times k and k - 1 in the local navigation system, Δθ k =|Δθ k |, represents the change in the attitude quaternion from time k - 1 to time k.

[0064] Speed differential equation:

[0065]

[0066] Where, Denote the specific force output by the accelerometer, v n , g n respectively denote the velocity vector and the gravity vector in the local navigation system;

[0067] Integrate the velocity differential equation within [k - 1, k] to obtain:

[0068]

[0069] where, respectively denote the velocities at times k - 1 and k in the local navigation system; Denote the velocity increment generated by the specific force. Assume that the acceleration is linearly varying between times k - 1 and k, and obtain The approximate expression of is:

[0070]

[0071] is called the rotation effect compensation term, is called the paddling effect compensation term; is the velocity increment compensation term generated by the combined action of Coriolis acceleration, gravitational acceleration, and centripetal acceleration;

[0072] Position differential equation:

[0073]

[0074] where, R N denotes the radius of curvature of the prime vertical, R M denotes the radius of curvature of the meridian;

[0075] Integrate the position differential equation within the sampling interval [k - 1, k] to obtain:

[0076]

[0077] where, respectively denote the positions at times k - 1 and k in the local navigation system.

[0078] In one embodiment, the specific force equation is expressed as follows:

[0079]

[0080] When the vehicle is stationary, i.e., and are both 0, the above equation can be simplified to:

[0081]

[0082] Among them, f b and f n respectively represent the accelerations in the b-frame and n-frame.

[0083] Substitute each term, and we get:

[0084]

[0085] Therefore:

[0086]

[0087]

[0088] Among them, θ is the pitch angle, γ is the roll angle, represents the acceleration in the x-direction in the b-frame, represents the acceleration in the y-direction in the b-frame, represents the acceleration in the z-direction in the b-frame.

[0089] In the steps of calculating the pitch angle and roll angle, in the static state, the original data collected by the IMU is resolved using Equation (14) and Equation (15).

[0090] In one embodiment, the heading angle initialization includes: In the actual RTK operation, the forward direction of holding the RTK is inconsistent with the longitudinal axis of the carrier coordinate system. Simply relying on the velocity information of GNSS cannot truly reflect the real heading information, and relevant IMU observables need to be used. The real heading angle is shown as Figure 3 . In Figure 3 , OA represents the forward direction of holding the RTK, the EON coordinate system represents the projection of the northeast celestial coordinate system on the horizontal plane, and the XOY coordinate system is defined as the projection of the IMU coordinate system on the horizontal plane at the initial moment, briefly denoted as the h0-frame. At this time, it is considered that the Y-axis points to the "false north". The angle ψ0 between the Y-axis and the N-axis at the initial moment is the initial heading angle. The calculation of the heading angle in the rough alignment can be determined by the difference between ψ1 and ψ2. In addition, let v GNSS represent the horizontal velocity vector provided by the GNSS receiver, and v IMU represent the velocity vector resolved by the IMU in the XOY coordinate system.

[0091] Due to the inherent integration characteristics in the INS strapdown navigation algorithm, with the accumulation of inertial device errors, the INS error diverges without bound over time. In a short period of time, the attitude angles and velocities updated using INS diverge slowly, and the position diverges quickly. Therefore, the velocity information is selected as the input quantity for calculating the heading angle. As Figure 3As shown, if OA is represented as a velocity vector, ψ2 can be calculated by using its projection in the EON coordinate system. That is:

[0092]

[0093] In the formula, V GNSS,E represents the velocity in the E direction provided by GNSS at time t, and V GNSS,N represents the velocity in the N direction provided by GNSS at time t.

[0094] Similarly, the projection of the OA velocity vector in the XOY coordinate system can be used to calculate ψ1, that is:

[0095]

[0096] In the formula, V IMU,x represents the projection of the velocity solved by the IMU at time t on the X-axis, and V IMU,y represents the projection of the velocity solved by the IMU at time t on the Y-axis.

[0097] Therefore, in the Figure 3 geometric relationship, the heading angle can be expressed as:

[0098]

[0099] In practical applications, the velocity provided by GNSS contains random noise. During the time period [t0, t1,..., t k , the GNSS velocities at each moment are expressed as:

[0100]

[0101] Among them, ε t0 , ε t1 , ε tk all represent the random noise amounts at each moment.

[0102] Similarly, when INS updates the velocity, considering error terms such as device error, model error, and omission error, during the time period [t0, t1,..., t k , the IMU velocities at each moment are expressed as:

[0103]

[0104] Among them, Δv IMU (t0, t1) represents the velocity increment from t0 to t1, and Δv IMU (t0, t k ) represents the velocity increment from t0 to t k moment, and Δv IMU (t0, t k ) = ΔvIMU (t0, t1) + Δv IMU (t1, t2) + … + Δv IMU (t k-1 , t k ), ξ t0 represents the error caused by the initial IMU velocity, η t0,tk represents the integration error from t0 to t k moment, η t0,tk = η t0,t1 + η t1,t2 + … + η tk-1,tk .

[0105] Under normal circumstances, the initial velocity required for INS strapdown calculation needs to be obtained through an external sensor (GNSS), so ξ t0 The error sources mainly come from two parts, namely the error contained in the velocity provided by GNSS and the attitude angle error between the navigation coordinate system and the IMU coordinate system at the initial moment. η t0,tk The error is generated during the integration process, and its error sources are mainly caused by the accelerometer zero bias, gyro zero bias, and attitude angle error. Therefore, considering each error term, at t k The actual calculated expressions of ψ1 and ψ2 at the moment are respectively:

[0106]

[0107]

[0108] Therefore

[0109]

[0110] Observing Equation (23), directly using the velocity to solve the heading angle has many error terms, which affects the accuracy. To further improve the heading angle accuracy, each error term is analyzed. The error brought by INS velocity update is mainly composed of ξ t0 and η t0,tk . If the error caused by the zero bias in η t0,tk is to be reduced, it is necessary to calibrate the zero bias of the gyroscope and accelerometer before the experiment to eliminate the influence of the constant zero bias; for the attitude angle error contained in η t0,tk , it is required that the initial velocity be as close to 0 as possible. The reason is that the attitude angle accuracy calculated in the stationary state is relatively high, which suppresses the accumulation of attitude angle error to a certain extent. In addition, an initial velocity of 0 can reduce the influence of the attitude angle error in the ξ t0 error term. Observing Equation (20), each moment contains ξ t0 error, and the ξ t0In view of this, the present invention proposes a method for solving the heading angle using the velocity increment, and the specific derivation is as follows.

[0111] According to the coordinate transformation principle, the velocity relationship at time t0 can be expressed as:

[0112]

[0113] Among them, Substituting each item, we can get:

[0114]

[0115] Similarly, the velocity relationship at time t1 can be expressed as:

[0116]

[0117] Subtracting Equation (25) from Equation (26), we can get:

[0118]

[0119] Similar to Equation (18), Equation (27) can be rewritten as:

[0120]

[0121] Similarly, at time t k it can be expressed as:

[0122]

[0123] Among them, Δv GNSS,E (t0, t k ) represents the velocity increment of GNSS in the E direction from time t0 to t k , Δv GNSS,N (t0, t k ) represents the velocity increment of GNSS in the N direction from time t0 to t k , Δv IMU,x (t0, t k ) represents the projection of the velocity increment solved by the IMU from time t0 to t k on the X-axis of the horizontal coordinate system, and Δv IMU,y (t0, t k ) represents the projection of the velocity increment solved by the IMU from time t0 to t k on the Y-axis of the horizontal coordinate system.

[0124] Perform error analysis on the heading angle obtained from Equation (29), and let

[0125] For Derivation gives:

[0126]

[0127] Therefore

[0128]

[0129]

[0130]

[0131] Generally, the nominal speed measurement accuracy of general measurement type boards reaches the cm / s level. The GNSS speed measurement accuracy has a strong correlation with the carrier dynamic conditions. In the low-dynamic scenario of RTK measurement operations, it can be assumed that the GNSS speed measurement accuracy is better than 0.1 m / s. The normal walking speed of an adult is about 1.2 m / s to 1.5 m / s. Based on formula (32), the direction finding error is deduced to be 5° - 7°.

[0132] Similarly

[0133]

[0134] It is necessary to analyze the speed error calculated by the IMU. Because

[0135]

[0136] For low-speed moving MEMS inertial navigation, ignoring the influence brought by the error term and ignoring the gravity error at the same time, formula (34) can be simplified to:

[0137]

[0138] Integrating the above formula gives:

[0139] δv n =(f n ×φ+δf n )Δt (36)

[0140] Expanding formula (36) gives:

[0141]

[0142] Observing formula (37), the speed error resolved by the IMU in the x direction is related to and the horizontal acceleration. When a person holds an RTK and walks normally, assuming only the existence of the pitch angle θ is considered, and there is an acceleration f h in the horizontal direction and no acceleration in the celestial direction. There is the following relationship:

[0143]

[0144] φ y It is mainly composed of the attitude error at the static moment and the integral of the remaining zero bias error of the IMU-Y axis gyroscope within Δt time, and is expressed as follows:

[0145]

[0146] φ z It is mainly composed of the integral of the remaining zero bias error of the IMU-Z axis gyroscope within Δt time, and is expressed as follows:

[0147]

[0148] Consider Substitute equations (38), (39), and (40) into equation (37), and after arrangement, we have:

[0149]

[0150] That is:

[0151]

[0152] Consider:

[0153] Attitude accuracy at the static moment |φ y (t0)| < 0.2°;

[0154] Remaining zero bias error of the gyro Y axis |δbg y | < 0.01 dps;

[0155] Remaining zero bias error of the gyro Z axis |δbg z | < 0.05 dps;

[0156] Remaining zero bias error of the accelerometer X axis |δba x | / g < 0.001.

[0157] After arrangement, we have:

[0158]

[0159] During the process of the handheld RTK moving forward, the pitch angle changes in the range of 0° to 60°. The normal walking speed of an adult is about 1.2 m / s to 1.5 m / s. It is discussed in the following situations:

[0160] 1) When the carrier takes 1 s to reach the normal adult walking speed of 1.2 m / s from rest, that is, Δt = 1 s, f h Δt = 1.2 m / s, equation (43) can be written as:

[0161]

[0162] Among them, when θ ≈ 13°, (0.21·cosθ + 0.05·sinθ) reaches the maximum value, and the maximum value is 0.22. Therefore:

[0163]

[0164] 2) When it takes 1 s for the carrier to accelerate from rest to the normal adult walking speed of 1.5 m / s, that is, Δt = 1 s, f h Δt = 1.5 m / s, Equation (43) can be written as:

[0165]

[0166] Among them, when θ ≈ 13°, (0.21·cosθ + 0.05·sinθ) reaches the maximum value, and the maximum value is 0.22. Therefore:

[0167]

[0168] 3) When it takes 2 s for the carrier to accelerate from rest to the normal adult walking speed of 1.2 m / s, that is, Δt = 2 s, f h Δt = 1.2 m / s, Equation (43) can be written as:

[0169]

[0170] Among them, when θ ≈ 24°, (0.22·cosθ + 0.1·sinθ) reaches the maximum value, and the maximum value is 0.24. Therefore:

[0171]

[0172] 4) When it takes 2 s for the carrier to accelerate from rest to the normal adult walking speed of 1.5 m / s, that is, Δt = 2 s, f h Δt = 1.5 m / s, Equation (43) can be written as:

[0173]

[0174] Among them, when θ ≈ 24°, (0.22·cosθ + 0.1·sinθ) reaches the maximum value, and the maximum value is 0.24. Therefore:

[0175]

[0176] 5) When it takes 3 s for the carrier to accelerate from rest to the normal adult walking speed of 1.2 m / s, that is, Δt = 3 s, f h Δt = 1.2 m / s, Equation (43) can be written as:

[0177]

[0178] Among them, when θ≈33°, (0.23·cosθ + 0.15·sinθ) reaches the maximum value, and the maximum value is 0.27. Therefore:

[0179]

[0180] 6) When the carrier takes 3 s to reach the normal adult walking speed of 1.5 m / s from rest, that is, Δt = 3 s, f h Δt = 1.5 m / s, Equation (43) can be written as:

[0181]

[0182] Among them, when θ≈33°, (0.23·cosθ + 0.15·sinθ) reaches the maximum value, and the maximum value is 0.27. Therefore:

[0183]

[0184] Comparing Equation (32) with Equation (33), the horizontal velocity increments of the two are the same. Combining Equation (45), Equation (47), Equation (49), Equation (51), Equation (53) and Equation (55), it can be known that:

[0185] When the normal adult walking speed is about 1.2 m / s to 1.5 m / s and it takes 1 s, the velocity component error is about 0.048 m / s, and the estimated direction finding error is 2.6° to 3.2°.

[0186] When the normal adult walking speed is about 1.2 m / s to 1.5 m / s and it takes 2 s, the velocity component error is about 0.104 m / s, and the estimated direction finding error is 5.6° to 7.0°.

[0187] When the normal adult walking speed is about 1.2 m / s to 1.5 m / s and it takes 3 s, the velocity component error is about 0.171 m / s, and the estimated direction finding error is 9.2° to 11.5°.

[0188] Considering ψ0 = ψ1 - ψ2, there is

[0189]

[0190] When the carrier takes 1 second to reach the normal adult walking speed of 1.2 m / s from rest, there is: degree.

[0191] When the carrier takes 2 seconds to reach the normal adult walking speed of 1.2 m / s from rest, there is: degree.

[0192] When the carrier takes 3 seconds to reach the normal adult walking speed of 1.2 m / s from rest, there is: Spend.

[0193] Comprehensive ψ1 and σ ψ2 According to the analysis, within 2 seconds, when the horizontal velocity increment reaches the normal adult walking speed of 1.2m / s or above, the final heading angle error Can be guaranteed within 10°.

[0194] An electronic device, comprising: a processor;

[0195] A memory; and a program, wherein the program is stored in the memory and is configured to be executed by the processor, the program including a method for executing a method for acquiring an initial heading value of a handheld GNSS / MEMS-INS receiver.

[0196] A computer-readable storage medium stores a computer program, and the computer program is executed by a processor to provide a method for obtaining an initial heading value of a handheld GNSS / MEMS-INS receiver.

[0197] In the process of rough alignment, the present invention uses the rotation relationship between the IMU coordinate system and the ENU coordinate system to obtain the relationship between the carrier's forward direction and the heading angle. At the same time, the speed increments of different sensors are quoted to solve the heading angle. The existing heading alignment schemes mainly include those based on geomagnetic measurement, horizontal position matching, horizontal velocity matching and horizontal acceleration matching. Among them, the geomagnetic measurement requires the use of a magnetometer, and is easily affected by the environment, and the magnetometer needs to be calibrated during operation; the traditional horizontal position matching and horizontal velocity matching are based on the premise that the carrier's forward direction is consistent with the longitudinal axis (Y axis) of the IMU coordinate system, and the heading angle is calculated by the position and velocity information provided by GNSS, without considering the problem that the carrier's forward direction is inconsistent with the longitudinal axis of the IMU coordinate system, and ignoring the position relationship between the IMU coordinate system and the ENU coordinate system. In view of the above problems, the present invention introduces a speed increment to solve the heading angle by means of IMU related observations, and at the same time takes into account the error accumulation in the INS strapdown solution and the random noise of GNSS. The solution based on horizontal acceleration matching requires the carrier to have a large acceleration, which is not applicable to handheld RTK receivers. However, the method proposed in the present invention does not require the carrier to provide a large acceleration, and the heading angle can be solved at a low speed.

[0198] The heading rough alignment method applicable to RTK tilt measurement in the present invention, that is, calculating the heading angle based on the velocity increment in different coordinate systems. This method is not affected by external magnetic field interference. During the initialization process, it does not require the carrier's traveling direction to remain at a constant angle with the inertial module's axis, and is suitable for the operation mode of handheld RTK. After completing the heading rough alignment based on this method, the output heading can be used as the initial value for subsequent GNSS / INS combined filtering to complete the fine alignment of the entire filter.

[0199] The method provided by the present invention is simple and easy to implement in engineering. During the rough alignment process, the heading angle can be calculated through the velocity increments provided by the IMU and GNSS respectively, effectively reducing the errors brought by INS velocity update and the observation noise of GNSS, and not involving complex filtering calculations and adjustment processes. The operation mode is flexible and simple, without requiring the carrier's forward direction to be consistent with the carrier's longitudinal axis, and at the same time, without requiring the carrier to provide a large maneuverability, and is very suitable for the RTK measurement operation scenario.

[0200] The above is only the preferred embodiment of the present invention, and does not impose any form of limitation on the present invention; any ordinary technician in the industry can smoothly implement the present invention as shown in the accompanying drawings of the specification and the above; however, any equivalent changes made by those skilled in the art within the scope of the technical solution of the present invention by using the technical content disclosed above for a little modification, decoration and evolution are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver, characterized in that, It includes the following steps: Calculate the pitch angle and roll angle, and resolve the original data collected by the IMU in the stationary state to obtain the pitch angle and roll angle at each epoch; INS initialization: At the starting moment of the rough heading alignment, use the position provided by the RTK as the initial position of the INS, use the speed provided by the RTK as the initial speed of the INS, use the pitch angle and roll angle at the corresponding epoch as the initial values of the pitch angle and roll angle in the INS strapdown solution, and assign the initial value of the heading angle in the INS strapdown solution to 0. At this time, it is considered that the y-axis direction in the IMU coordinate system points to the false north; INS strapdown algorithm update: Obtain the speed resolved by the IMU at each epoch according to the attitude update, speed update, and position update formulas; In the INS strapdown algorithm update step, the attitude differential equation: Among them, is the constructed skew-symmetric matrix, and represents the angular velocity output by the gyroscope, represents the attitude transformation quaternion for the rotation of the b system to the n system, represents the conjugate quaternion of Within the sampling interval [k - 1, k], solve the attitude differential equation through the Picard algorithm to obtain: Among them, respectively represent the attitude transformation quaternions at times k and k - 1 in the local navigation system, Δθ k = |Δθ k |, represents the change in the attitude quaternion from time k - 1 to time k; In the INS strapdown algorithm update step, the speed differential equation: wherein, represents the specific force output by the accelerometer, v n , g n respectively represent the velocity vector and the gravity vector in the local navigation system; Integrate the speed differential equation within [k - 1, k] to obtain: Among them, respectively represent the velocities at the (k - 1)-th and k-th moments in the local navigation system; represents the velocity increment generated by specific force. Assuming that the acceleration between the (k - 1)-th moment and the k-th moment changes linearly, we obtain The approximate expression of is: is called the rotational effect compensation term, is called the oar effect compensation; is the velocity increment compensation term generated by the combined action of Coriolis acceleration, gravitational acceleration and centripetal acceleration; In the INS strapdown algorithm update step, the position differential equation: Among them, R N represents the radius of curvature of the prime vertical, and R M represents the radius of curvature of the meridian; Within the sampling interval [k - 1, k], integrate the position differential equation to obtain: wherein, respectively represent the positions at the (k - 1)-th and k-th moments in the local navigation system; Calculate the speed increment, select the rough heading alignment initialization interval and calculate the GNSS speed increment and IMU speed increment within the interval; In the step of calculating the speed increment, according to the attitude update, speed update and position update formulas, the speed increment Δv of the INS between the previous and current epochs is obtained. IMU (t k-1 ,t k ), and the speed increment Δv of the GNSS between the previous and current epochs is obtained by taking the difference between the previous and current epochs. GNSS (t k-1 ,t k ); Calculate the heading angle, and calculate the heading angle at the starting moment according to the GNSS speed increment and IMU speed increment at the starting and ending moments; In the step of calculating the heading angle, the formula for calculating the heading angle at the starting moment according to the GNSS speed increment and IMU speed increment at the starting and ending moments is: Among them, ψ0 represents the heading angle at time t0, Δv GNSS,E (t0, t k ) represents the velocity increment of GNSS in the E direction from time t0 to t k moment, Δv GNSS,N (t0, t k ) represents the velocity increment of GNSS in the N direction from time t0 to t k moment, Δv IMU,x (t0, t k ) represents the projection of the velocity increment resolved by IMU from time t0 to t k moment on the X-axis of the horizontal coordinate system, Δv IMU,y (t0, t k ) represents the projection of the velocity increment resolved by IMU from time t0 to t k moment on the Y-axis of the horizontal coordinate system.

2. The method for obtaining the initial heading value of a handheld GNSS / MEMS-INS receiver according to claim 1, wherein: In the step of calculating the pitch angle and roll angle, the formula for resolving the original data collected by the IMU in the stationary state is: where θ is the pitch angle and γ is the roll angle, represents the acceleration in the x - direction in the b - frame, represents the acceleration in the y - direction in the b - frame, represents the acceleration in the z - direction in the b - frame.

3. An electronic device, characterized in that It includes: A processor; A memory; And a program, where the program is stored in the memory and is configured to be executed by the processor. The program includes instructions for performing the method according to any one of claims 1 - 2.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer program is executed by the processor to perform the method according to any one of claims 1 - 2.

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