Tilt Correction Method for Dynamic Measurement of Dual-Axis Scanning Sonar

Abstract

This invention belongs to the field of marine engineering surveying, and specifically relates to a tilt correction method for dynamic measurement using dual-axis scanning sonar. This invention employs a combination of dual-axis scanning sonar and dual-axis attitude sensors for measurement. While measuring the foundation elevation using this combined equipment, the measurement results are corrected in real time. This solves the problem of real-time and accurate measurement and dynamic tilt correction of the foundation elevation with minimal or no movement of the construction vessel, thereby improving construction efficiency and reducing the workload of personnel.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering surveying, and specifically relates to a tilt correction method for dynamic measurement using dual-axis scanning sonar. Background Technology

[0002] During underwater subgrade leveling and compaction, it is necessary to quickly measure the height of the subgrade after leveling or compaction. Existing technologies mainly fall into two categories: post-construction inspection and real-time inspection.

[0003] The post-construction inspection method involves moving the construction vessel to clear the work surface after initial leveling or compaction, and then using a specialized surveying vessel to measure the actual height of the underwater foundation. The measurement results are used to determine if the construction requirements are met. If not, the vessel may need to be moved back for re-leveling or compaction until the requirements are met. This method significantly impacts construction efficiency.

[0004] The real-time detection method involves installing sonar measuring equipment along the edge of the ship's hull near the construction facilities. This equipment can measure the subgrade cover simultaneously with the construction work. The sonar transducer needs to be installed along the hull of the construction vessel, close to the leveling or compaction work area (e.g., ...). Figure 1 The transducer needs to be lowered into the water below the ship's bottom using a measuring rod. The height difference between the deck of an offshore construction vessel and the sonar transducer typically exceeds 2 meters. Since the measuring rod is mounted on the side of the ship without reliable fixing, it bends under the impact of water flow, causing the transducer to tilt and affecting the measurement results (e.g., ...). Figure 2 ).

[0005] The impact of transducer tilt on the measurement of the substrate consists of two parts. First, due to the bending of the measuring rod, the transducer deviates from its initial (untilted) position. The amount of deviation is related to the distance between the transducer and the fixed point of the measuring rod (the length of the measuring rod) and the bending of the measuring rod. Second, the transducer tilt causes a deviation in the sonar scanning area. The amount of deviation is calculated based on the height difference and tilt angle of the substrate relative to the transducer. Sonar equipment transducers require a measuring rod extending from the ship's side below the water surface. Because the measuring rod is suspended outside the ship's side, it cannot be effectively reinforced. Under the impact of water flow, the measuring rod will tilt, causing the transducer to tilt as well. Typical sonar equipment does not have the capability to measure and correct for deviations caused by tilt in real time, which significantly affects the accuracy of the measurement results and limits the application and promotion of this method in actual construction.

[0006] In summary, in recent years, there has been an increase in high-precision leveling, compaction and other marine engineering projects, and the scale of these projects has been continuously expanding. At the same time as construction, there is an urgent need to develop technologies for efficiently and accurately measuring the height of the subgrade. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a tilt correction method for dynamic measurement using dual-axis scanning sonar, achieving a solution for high-efficiency and high-precision foundation elevation measurement without moving construction equipment or affecting the construction process.

[0008] A tilt correction method for dynamic measurements using dual-axis scanning sonar includes the following steps: S1. Install the dual-axis scanning sonar (DAS) on the edge of the deck of the construction vessel, close to the leveling or tamping construction equipment. The initial coordinate system O-xyz of the sonar transducer during installation is in the same direction as the coordinate axis of the ship's coordinate system. S2. Install a dual-axis attitude sensor on the sonar transducer. The dual-axis attitude sensor measures the real-time attitude of the transducer while the sonar measures the height of the bed. During construction, the sonar transducer is in an inclined state. At this time, the equipment coordinate system is O-uvw, which is called the real-time coordinate system of the sonar transducer. S3. Let the pitch angle p and roll angle r of the sonar transducer at this time be the angles between the coordinate axes u and v and the horizontal plane O-xy in the O-xyz coordinate system, respectively. S4. Both the real-time coordinate system O-uvw and the initial coordinate system O-xyz of the sonar transducer are spatial rectangular coordinate systems. Coordinate transformation between them can be achieved by rotating them around the x and y axes by angles α and β, respectively. The rotation matrix can be represented as follows: ; For the unit vectors on the x and y axes in the O-xyz coordinate system: (1 0 0) T and (0 1 0) T After coordinate rotation, we get: (ux vx wx) T and (uy vy wy) T ,Right now:

[0009] Unit vectors on the x and y axes (1 0 0) T and (0 1 0) T After conversion, they are located on the u and v axes respectively.

[0010] The p and r values ​​measured by the dual-axis attitude sensor are the angles between the u and v axes and the horizontal plane O-xy in the O-xyz coordinate system, respectively. Therefore: .

[0011] α and β are calculated using p and r, and R is calculated from these values; for any point Q on the base bed determined by sonar, the coordinate system of the measurement result in the equipment coordinate system is: (uvw) T In the ship's coordinate system, the coordinates are: (xyz) T Based on the above formula, we can obtain:

[0012] The above formula is the calculation formula for correcting the measurement results when the sonar transducer is tilted to the coordinates of the ship's hull coordinate system. When α and β are small angles, sinα=α, sinβ=β, cosα=1, cosβ=1, sinα·sinβ=0; at this time: α=r, β=p.

[0013] When calculating the position offset of the sonar transducer, the bending of the probe is ignored, and the tilt angle of the sonar transducer is directly taken as the tilt of the probe. Assuming the length of the probe is L, the pitch angle of the transducer is p, and the roll angle is r, the position offsets ΔX and ΔY caused by the tilt of the probe are: .

[0014] In underwater surveying, the measurement data from underwater measuring equipment such as sonar generally reside in the equipment coordinate system, which is typically established on the transducer. To convert the equipment coordinate system data to the construction coordinate system, a ship coordinate system is usually established on the construction vessel. GNSS RTK, attitude sensors, and other equipment are installed on the vessel, and a transformation relationship is established between the ship coordinate system and the construction coordinate system to achieve real-time conversion. When sonar equipment is installed on the vessel, its equipment coordinate system is aligned with the ship coordinate system; therefore, the sonar measurement results also belong to the ship coordinate system. Through the transformation relationship between the ship coordinate system and the construction coordinate system, the sonar measurement results can be converted to the construction coordinate system.

[0015] Since the tilt angle measured by the attitude sensor is inconsistent with the Euler angles defined in the spatial coordinate system, this invention derives a rigorous calculation formula based on the relationship between the tilt angle measured by the attitude sensor and the Euler angles defined in the spatial coordinate system, ensuring the accuracy of the transducer tilt correction calculation.

[0016] This invention employs a combination of dual-axis scanning sonar and dual-axis attitude sensors for measurement. While measuring the elevation of the subgrade using this combined equipment, the measurement results are corrected in real time. This enables real-time and accurate measurement and dynamic tilt correction of the subgrade elevation without moving or with minimal movement of construction facilities, thereby improving construction efficiency and reducing the workload of personnel. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the installation relationship of the device of the present invention; Figure 2 The effect of transducer tilt on the measurement of the substrate bed; Figure 3 A schematic diagram showing the coordinate system relationship of the dual-axis scanning sonar before and after tilting; In the diagram: 1. Construction vessel and working face; 2. Dual-axis scanning sonar; 3. Dual-axis attitude sensor; 4. GNSS RTK; 5. PC computer; 6. Measuring rod; 7. Foundation bed; 8. Construction equipment; 9. Measurement area. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0019] Example 1

[0020] A tilt correction method for dynamic measurements using dual-axis scanning sonar includes the following steps: S1. Install the dual-axis scanning sonar (DAS) on the edge of the deck of the construction vessel, close to the leveling or tamping construction equipment. The initial coordinate system O-xyz of the sonar transducer during installation is in the same direction as the coordinate axis of the ship's coordinate system. S2. Install a dual-axis attitude sensor on the sonar transducer. The dual-axis attitude sensor measures the real-time attitude of the transducer while the sonar measures the height of the bed. During construction, the sonar transducer is in an inclined state. At this time, the equipment coordinate system is O-uvw, which is called the real-time coordinate system of the sonar transducer. S3. Let the pitch angle p and roll angle r of the sonar transducer at this time be the angles between the coordinate axes u and v and the horizontal plane O-xy in the O-xyz coordinate system, respectively. S4. Both the real-time coordinate system O-uvw and the initial coordinate system O-xyz of the sonar transducer are spatial rectangular coordinate systems. Coordinate transformation between them can be achieved by rotating them around the x and y axes by angles α and β, respectively. The rotation matrix can be represented as follows: ; For the unit vectors on the x and y axes in the O-xyz coordinate system: (1 0 0) T and (0 1 0) T After coordinate rotation, we get: (u x v x w x ) T and (u y v y w y ) T ,Right now:

[0021] Unit vectors on the x and y axes (1 0 0) T and (0 1 0) T After conversion, they are located on the u and v axes respectively.

[0022] The p and r values ​​measured by the dual-axis attitude sensor are the angles between the u and v axes and the horizontal plane O-xy in the O-xyz coordinate system, respectively. Therefore:

[0023] α and β are calculated using p and r, and R is calculated from these values; for any point Q on the base bed determined by sonar, the coordinate system of the measurement result in the equipment coordinate system is: (uvw) T In the ship's coordinate system, the coordinates are: (xyz) T Based on the above formula, we can obtain: .

[0024] The above formula is the calculation formula for correcting the measurement results when the sonar transducer is tilted to the coordinates of the ship's hull coordinate system. When α and β are small angles, sinα=α, sinβ=β, cosα=1, cosβ=1, sinα·sinβ=0; at this time: α=r, β=p.

[0025] When calculating the position offset of the sonar transducer, the bending of the probe is ignored, and the tilt angle of the sonar transducer is directly taken as the tilt of the probe. Assuming the length of the probe is L, the pitch angle of the transducer is p, and the roll angle is r, the position offsets ΔX and ΔY caused by the tilt of the probe are: .

[0026] Example 2

[0027] This embodiment is applied to real-time elevation measurement of underwater foundation beds on a non-powered compaction and refilling construction vessel. A dual-axis scanning sonar is installed on the edge of the vessel's hull using a metal measuring rod of length L=5m. Two contact points are set 0.5m above the water surface, tightly secured against the hull, with a submersion depth of 4.5m. The dual-axis scanning sonar (DAS) is located at the bottom of the measuring rod, submerged at least 1m below the hull bottom. A dual-axis attitude sensor is installed at the same height as the dual-axis scanning sonar, with the positive P-axis pointing towards the u-axis direction of the dual-axis scanning sonar's coordinate system O-uvw. After installation, O-uvw is leveled so that the u-axis aligns with the x-axis direction of the vessel's coordinate system O-xyz, and the initial reading of the dual-axis attitude sensor is set to zero.

[0028] During construction, the metal measuring rod, submerged 4.5m underwater, bent due to the impact of the water flow, causing the dual-axis scanning sonar to tilt and resulting in an angular deviation between the equipment's real-time coordinate system O-uvw and the ship's coordinate system O-xyz. While the dual-axis scanning sonar measures the underwater foundation elevation, the dual-axis attitude sensor simultaneously acquires attitude data in real time, reading the tilt angles p and r of the u-axis and v-axis of O-uvw relative to the horizontal plane O-xy of the ship's coordinate system. Based on the mathematical method of this invention, the rotation angle α around the x-axis and the rotation angle β around the y-axis can be calculated.

Claims

1. A tilt correction method for dynamic measurement of dual-axis scanning sonar, characterized in that, Includes the following steps: S1. Install the dual-axis scanning sonar (DAS) on the edge of the deck of the construction vessel, close to the leveling or tamping construction equipment. The initial coordinate system O-xyz of the sonar transducer during installation is in the same direction as the coordinate axis of the ship's coordinate system. S2. Install a dual-axis attitude sensor on the sonar transducer. The dual-axis attitude sensor measures the real-time attitude of the transducer while the sonar measures the height of the bed. During construction, the sonar transducer is in an inclined state. At this time, the equipment coordinate system is O-uvw, which is called the real-time coordinate system of the sonar transducer. S3. Let the pitch angle p and roll angle r of the sonar transducer at this time be the angles between the coordinate axes u and v and the horizontal plane O-xy in the O-xyz coordinate system, respectively. S4. Both the real-time coordinate system O-uvw and the initial coordinate system O-xyz of the sonar transducer are spatial rectangular coordinate systems. Coordinate transformation between them can be achieved by rotating them around the x and y axes by angles α and β, respectively. The rotation matrix can be represented as follows: ； For the unit vectors on the x and y axes in the O-xyz coordinate system: (1 0 0) T and (0 1 0) T After coordinate rotation, we get: (u x v x w x ) T and (u y v y w y ) T ,Right now: ； Unit vectors on the x and y axes (1 0 0) T and (0 1 0) T After conversion, they are located on the u and v axes respectively.

2. The tilt correction method for dynamic measurement of dual-axis scanning sonar according to claim 1, characterized in that, The p and r values ​​measured by the dual-axis attitude sensor are the angles between the u and v axes and the horizontal plane O-xy in the O-xyz coordinate system, respectively. Therefore: 。 3. The tilt correction method for dynamic measurement of dual-axis scanning sonar according to claim 1, characterized in that, α and β are calculated using p and r, and R is calculated from these values. For any point Q on the base bed determined by sonar, the coordinate system of the measurement result in the equipment coordinate system is: (uvw). T In the ship's coordinate system, the coordinates are: (xyz) T Based on the above formula, we can obtain: The above formula is the calculation formula for correcting the measurement results when the sonar transducer is tilted to the coordinates of the ship's hull coordinate system. When α and β are small angles, sinα=α, sinβ=β, cosα=1, cosβ=1, sinα·sinβ=0; At this point: α = r, β = p.

4. The tilt correction method for dynamic measurement of dual-axis scanning sonar according to claim 1, characterized in that, in When calculating the position offset of the sonar transducer, the bending of the probe is ignored, and the tilt angle of the sonar transducer is directly taken as the tilt of the probe. Assuming the length of the probe is L, the pitch angle of the transducer is p, and the roll angle is r, the position offsets ΔX and ΔY caused by the tilt of the probe are: 。

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