Gnss receiver, tilt measuring device and calibration method

Abstract

The application discloses a kind of GNSS receiver, tilt measuring device and calibration method, the tilt measuring device includes GNSS-IMU combination module, gimbaling mechanism and measuring rod, the bottom of GNSS-IMU combination module is connected with the measuring rod by gimbaling mechanism, and the calibration method includes: obtaining the locking angle of gimbaling mechanism;Measurement data is obtained by using tilt measuring device in a measurement window to measure;The installation angle deviation to be calibrated is calculated using locking angle and measurement data.This application keeps GNSS antenna horizontal to the sky through gimbaling structure, ensures the best signal receiving condition, adjusts the Z-axis direction of body using gimbaling restraint, facilitates to obtain better signal receiving effect, improves attitude measurement accuracy, uses the mechanical restraint of gimbaling, reduces the initial value uncertainty of calibration parameter, accelerates calibration convergence speed, and improves calibration accuracy.

Description

Technical Field

[0001] This invention relates to a GNSS receiver, a tilt measurement device, and a calibration method. Background Technology

[0002] Traditional GNSS pole-mounted measurement systems typically employ a fixed connection method, rigidly linking the GNSS receiver, IMU (Inertial Measurement Unit), and pole. During measurement, the operator holds the pole, aligning the pole tip with the point to be measured. The antenna position is obtained via GNSS, and the attitude angles (roll, pitch, yaw) measured by the IMU, along with the known pole length, are used to calculate the three-dimensional coordinates of the pole tip.

[0003] Existing rod-type measurement systems have the following problems:

[0004] When the measuring rod tilts, the GNSS antenna tilts accordingly. When the measuring rod tilts at a large angle (e.g., tilt angle > 20°), the Z-axis accelerometer of the IMU deviates from the direction of gravity, and the horizontal attitude (roll and pitch) measurement accuracy is significantly reduced, resulting in an increase in the error of the rod tip position calculation. The antenna gain pattern deviates from the zenith direction, leading to a decrease in signal strength, an increase in multipath effect, and affecting positioning accuracy.

[0005] It is necessary to calibrate three installation angle deviations (Δroll, Δpitch, Δyaw) and three lever deviations (bx, by, bz) simultaneously, for a total of 6 parameters. The initial values ​​are difficult to determine, and the calibration convergence speed is slow.

[0006] In mountainous or steep slope environments, operators need to maintain their balance on sloping ground while controlling the posture of the measuring rod, which makes the operation difficult and the measurement efficiency low. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the defects of poor signal strength, low positioning accuracy, high operation difficulty and low measurement efficiency in the prior art, and to provide a GNSS receiver, tilt measurement device and calibration method that improves attitude measurement accuracy, utilizes the mechanical constraint of the universal joint, reduces the uncertainty of the initial value of calibration parameters, speeds up the calibration convergence speed and improves the calibration accuracy.

[0008] The present invention solves the above-mentioned technical problems through the following technical solution:

[0009] A calibration method for an inclination measuring device, characterized in that the inclination measuring device includes a GNSS-IMU assembly module, a universal joint mechanism, and a measuring rod; the bottom of the GNSS-IMU assembly module is connected to the measuring rod via the universal joint mechanism; and the calibration method includes:

[0010] Obtain the locking angle of the universal joint mechanism;

[0011] Measurement data are obtained by using an inclined measuring device within a measuring window;

[0012] The installation angle deviation to be calibrated is calculated using the locking angle and measurement data.

[0013] Preferably, the step of calculating the installation angle deviation to be calibrated using the locking angle and measurement data includes:

[0014] The residual between the measurement data and the tilt measurement device model data is calculated using the locking angle and the measurement data.

[0015] Based on the residual, iterative optimization is performed to determine the installation angle deviation to be calibrated.

[0016] Preferably, the residual is based on Obtain, among which, To determine the location using GNSS, For the location of control points, The pole arm vector from the antenna of the GNSS-IMU module to the center of the fuselage. Let the vector of the measuring rod be the vector within the fuselage system. Let be the rotation matrix from the fuselage coordinate system to the navigation coordinate system. , , The installation angle deviation to be calibrated. , The heading and pitch angles measured by the IMU.

[0017] Preferably, the rotation matrix is ,in , , For the IMU, the heading angle, pitch angle, and roll angle are measured. , , The installation angle deviation to be calibrated. , , This is the rotation matrix for the z, y, and x axes of the navigation coordinate system.

[0018] Preferably, the position of the control point is determined by... Obtain To determine the position of the probe tip within the navigation system, The position of the GNSS antenna in the navigation system. The lever arm vector from the GNSS antenna to the center of the fuselage. Let the vector of the measuring rod be the vector within the fuselage system. The calibration method includes: (The rotation matrix is ​​given by the model number, which is the rotation matrix from the fuselage coordinate system to the navigation coordinate system.)

[0019] Keep the rod tip precisely aligned with the control point to acquire measurement data from the measurement window.

[0020] Preferably, the pass Obtain, among which For gimbal rotation matrix, , For the locking angle of the universal joint, The length of the measuring rod.

[0021] Preferably, the residual is used to obtain the optimization objective equation for the installation angle deviation to be calibrated. The calculation of the installation angle deviation to be calibrated using the locking angle and measurement data includes:

[0022] The calibrated value of the installation angle deviation is obtained by solving the optimization objective equation using an iterative optimization algorithm.

[0023] Preferably, the calibration method includes:

[0024] The target area is tilted using the calibrated quantity and the locking angle.

[0025] The present invention also provides an inclination measuring device, characterized in that the inclination measuring device is used to implement the calibration method described above.

[0026] The present invention also provides a GNSS receiver, characterized in that the GNSS receiver is used in the tilt measurement device as described above.

[0027] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0028] The positive and progressive effects of this invention are as follows:

[0029] The GNSS antenna is kept horizontally upwards by using a gimbal structure to ensure optimal signal reception conditions.

[0030] By using a universal joint constraint to keep the fuselage Z-axis always pointing upwards, the Z-axis of the accelerometer is stably aligned with the direction of gravity, thus improving the accuracy of attitude measurement.

[0031] By utilizing the mechanical constraints of the universal joint, the uncertainty of the initial values ​​of calibration parameters is reduced, the calibration convergence speed is accelerated, and the calibration accuracy is improved.

[0032] The three-dimensional attitude measurement is simplified into a two-dimensional operation (azimuth angle + tilt angle), reducing the difficulty of operation.

[0033] Improve the system's adaptability and operational efficiency in complex terrains (mountains, steep slopes, uneven ground). Attached Figure Description

[0034] Figure 1 This is a flowchart of the calibration method of Embodiment 1 of the present invention. Detailed Implementation

[0035] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0036] Example 1

[0037] This embodiment provides an inclination measurement device, which includes a GNSS-IMU combination module, a universal joint mechanism, and a measuring rod.

[0038] The GNSS-IMU combined module is a GNSS receiver.

[0039] Specifically, the tilt measuring device includes:

[0040] Measuring rod: A carbon fiber or aluminum alloy rod with a length of L (typically 1.2-3.0 meters), with a centering device at the tip;

[0041] Adjustable universal joint mechanism: including outer ring and inner ring, adopting a two-axis structure (pitch axis and roll axis), equipped with an angle scale and locking device, allowing users to lock the body at any tilt angle relative to the measuring rod (such as continuously adjustable from 0° to 45°), and read the locking angle value through the scale. The adjustable universal joint mechanism is equipped with an angle indicator device, and the scale marks the universal joint locking angle with an accuracy of ≤0.5°, which is convenient for users to read and input calibration programs.

[0042] GNSS-IMU combined module: fixed on the inner ring of the gimbal, including GNSS antenna, GNSS receiver and IMU sensor (IMU is installed inside the receiver), with the Z-axis of the fuselage coordinate system facing upward;

[0043] The working principle of this embodiment is as follows:

[0044] Users can manually adjust the universal joint to lock at the locking angle α (read via the dial) according to the slope of the terrain, so that the fuselage relative to the measuring rod produces a preset tilt angle, thereby compensating for the antenna attitude when the rod is tilted and optimizing the GNSS signal reception quality.

[0045] After the universal joint is locked, the body and the measuring rod form a fixed geometric relationship, and the Z-axis of the body is tilted by an angle α relative to the rod axis;

[0046] The operator uses a tilting probe to take measurements, and the IMU measures the fuselage's heading angle ψ, pitch angle θ, and roll angle φ.

[0047] The calibration algorithm receives the gimbal angle α input by the user as a known parameter, and combines it with the IMU measurement value to accurately calculate the installation angle deviation.

[0048] Specifically, the coordinate system is defined in this embodiment as follows:

[0049] Navigation coordinate system (n-frame): Northeast-Sky (ENU) coordinate system, with the X-axis pointing east, the Y-axis pointing north, and the Z-axis pointing skyward.

[0050] The fuselage coordinate system (b-frame) is fixed to the GNSS-IMU module. Under the constraint of the gimbal, the Z-axis always points upward and is parallel or approximately parallel to the Z-axis of the navigation system.

[0051] P-frame coordinate system: fixed to the measuring rod, with the Z-axis pointing downwards along the rod towards the rod tip.

[0052] Rotation matrix from fuselage coordinate system to navigation coordinate system: .

[0053] in: , , For IMU measurements: heading angle, pitch angle, and roll angle (in radians); gimbal constraints: (Set to 0); , , The installation angle deviation to be calibrated is denoted as , where The initial value is 0.

[0054] The control point location is obtained through Obtain, among which The position of the pole tip in the navigation system; : The position of the GNSS antenna in the navigation system (GNSS measurement); : The arm vector from the antenna to the center of the fuselage (known, represented in fuselage system); The representation of the stick vector in the fuselage system includes the stick length and stick arm deviation:

[0055] Considering the gimbal locking angle α (user input), the vector of the rod in the fuselage system is: .

[0056] in For gimbal rotation matrix (e.g., tilt in the pitch direction): .

[0057] Expanded to: .

[0058] in, Lock the angle for the universal joint (user reads the scale and inputs it); The pole length (accurately measured and entered by the user).

[0059] Set at least one high-precision control point (accuracy ≤ 5mm) within the measurement area, and the coordinates of this point shall be... Known.

[0060] Use the following steps to collect location data:

[0061] Set the universal joint angle. The user adjusts the universal joint locking angle α (e.g., 25°) according to the working terrain, reads the dial value, and enters the calibration program to lock the universal joint fixing device.

[0062] Perform a 360° conical motion around the tip of the rod with different tilt angles.

[0063] At a single control point, keep the pole tip precisely aligned with the control point (alignment accuracy ≤ 2mm), and collect data for different postures sequentially (or perform 360° conical motions around the pole tip with different postures):

[0064] Record the GNSS position for each attitude. IMU attitude angle Universal joint angle (All postures are the same).

[0065] The universal joint angle α remains constant throughout the calibration process and is used as a known geometric parameter in the calibration calculation.

[0066] Establish the observation window equation system in real time. For the first... The residual for the first measurement is: .

[0067] Construct the optimization objective function: .

[0068] The above objective function is solved using an iterative optimization algorithm, with the initial parameter values ​​set to... ,in Approximately zero values ​​under gimbal constraints facilitate rapid convergence. Suitable optimization algorithms include, but are not limited to, nonlinear optimization methods such as least squares, Levenberg-Marquardt algorithm, Gauss-Newton method, and gradient descent.

[0069] See Figure 1 Using the aforementioned tilt measuring device, this embodiment also provides a calibration method, including:

[0070] Step 100: Obtain the locking angle of the universal joint mechanism;

[0071] Step 101: Use an inclinometer to perform measurements within a measurement window to obtain measurement data;

[0072] Step 102: Calculate the installation angle deviation to be calibrated using the locking angle and measurement data.

[0073] The calculation of the installation angle deviation to be calibrated using the locking angle and measurement data includes:

[0074] The residual between the measurement data and the tilt measurement device model data is calculated using the locking angle and the measurement data.

[0075] Based on the residual, iterative optimization is performed to determine the installation angle deviation to be calibrated.

[0076] The residual is based on Obtain, among which, To determine the location using GNSS, For the location of control points, The pole arm vector from the antenna of the GNSS-IMU module to the center of the fuselage. Let the vector of the measuring rod be the vector within the fuselage system. Let be the rotation matrix from the fuselage coordinate system to the navigation coordinate system. , , The installation angle deviation to be calibrated. , The heading and pitch angles measured by the IMU.

[0077] The rotation matrix is: ,in , , For the IMU, the heading angle, pitch angle, and roll angle are measured. , , The installation angle deviation to be calibrated. , , This is the rotation matrix for the z, y, and x axes of the navigation coordinate system.

[0078] The control point location is obtained through Obtain To determine the position of the probe tip within the navigation system, The position of the GNSS antenna in the navigation system. The lever arm vector from the GNSS antenna to the center of the fuselage. Let the vector of the measuring rod be the vector within the fuselage system. The calibration method includes: (The rotation matrix is ​​given by the model number, which is the rotation matrix from the fuselage coordinate system to the navigation coordinate system.)

[0079] Keep the rod tip precisely aligned with the control point to acquire measurement data from the measurement window.

[0080] The pass Obtain, among which For gimbal rotation matrix, , For the locking angle of the universal joint, The length of the measuring rod.

[0081] The objective equation for obtaining the installation angle deviation to be calibrated is obtained using the residual. The calculation of the installation angle deviation to be calibrated using the locking angle and measurement data includes:

[0082] The calibrated value of the installation angle deviation is obtained by solving the optimization objective equation using an iterative optimization algorithm.

[0083] The calibration method further includes:

[0084] Step 103: Use the calibration quantity and locking angle to perform tilt measurement on the target area.

[0085] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A calibration method for an inclination measuring device, characterized in that, The tilt measurement device includes a GNSS-IMU module, a universal joint mechanism, and a measuring rod. The bottom of the GNSS-IMU module is connected to the measuring rod via the universal joint mechanism. The calibration method includes: Obtain the locking angle of the universal joint mechanism; Measurement data are obtained by using an inclined measuring device within a measuring window; The installation angle deviation to be calibrated is calculated using the locking angle and measurement data.

2. The calibration method for the tilt measuring device as described in claim 1, characterized in that, The calculation of the installation angle deviation to be calibrated using the locking angle and measurement data includes: The residual between the measurement data and the tilt measurement device model data is calculated using the locking angle and the measurement data. Based on the residual, iterative optimization is performed to determine the installation angle deviation to be calibrated.

3. The calibration method for the tilt measuring device as described in claim 2, characterized in that, The residual is based on Obtain, among which, To determine the location using GNSS, For the location of control points, The pole arm vector from the antenna of the GNSS-IMU module to the center of the fuselage. Let the vector of the measuring rod be the vector within the fuselage system. Let be the rotation matrix from the fuselage coordinate system to the navigation coordinate system. , , The installation angle deviation to be calibrated. , The heading and pitch angles measured by the IMU.

4. The calibration method for the tilt measuring device as described in claim 3, characterized in that, The rotation matrix is: ,in , , For the IMU, the heading angle, pitch angle, and roll angle are measured. , , The installation angle deviation to be calibrated. , , This is the rotation matrix for the z, y, and x axes of the navigation coordinate system.

5. The calibration method for the tilt measuring device as described in claim 3, characterized in that, The control point location is obtained through Obtain To determine the position of the probe tip within the navigation system, The position of the GNSS antenna in the navigation system. The lever arm vector from the GNSS antenna to the center of the fuselage. Let the vector of the measuring rod be the vector within the fuselage system. The calibration method includes: (The rotation matrix is ​​defined as the rotation matrix from the fuselage coordinate system to the navigation coordinate system.) Keep the rod tip precisely aligned with the control point to acquire measurement data from the measurement window.

6. The calibration method for the tilt measuring device as described in claim 4 or 5, characterized in that, The pass Obtain, among which For gimbal rotation matrix, , For the locking angle of the universal joint, The length of the measuring rod.

7. The calibration method for the tilt measuring device as described in claim 6, characterized in that, The objective equation for obtaining the installation angle deviation to be calibrated is obtained using the residual. The calculation of the installation angle deviation to be calibrated using the locking angle and measurement data includes: The calibrated value of the installation angle deviation is obtained by solving the optimization objective equation using an iterative optimization algorithm.

8. The calibration method for the tilt measuring device as described in claim 7, characterized in that, The calibration method includes: The target area is tilted using the calibrated quantity and the locking angle.

9. A tilt measuring device, characterized in that, The tilt measuring device is used to implement the calibration method as described in any one of claims 1 to 8.

10. A GNSS receiver, characterized in that, The GNSS receiver is used in the tilt measurement device as described in claim 9.

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