A method for inverting ship ice forces based on motion response monitoring data

Abstract

This application discloses a method for inverting ice forces on a ship's hull based on motion response monitoring data, relating to the field of ship navigation performance prediction technology. The method includes: real-time acquisition of motion response data for each degree of freedom when a ship navigates in ice-covered areas, and determination of the motion response at the ship's center of gravity based on rigid body kinematics principles; construction of a six-degree-of-freedom kinematic model of the ship under ice-covered navigation conditions; and inversion of the ice forces acting on the hull using an inverse solution method based on the six-degree-of-freedom kinematic model and the motion response at the ship's center of gravity. This application rapidly inverts ice forces based on measured motion response data, enabling real-time assessment of the navigation status of ships in ice-covered areas under different ice conditions. This is of great significance for evaluating the energy consumption, design, and safe operation of ships in ice-covered areas.

Description

Technical Field

[0001] This application relates to the field of ship navigation performance prediction technology, and in particular to a method for inverting ship hull ice force based on motion response monitoring data. Background Technology

[0002] Ice forces are the most significant environmental load affecting the navigation safety and navigability of ships sailing in ice-covered areas. The resulting fuel consumption, navigational delay risks, and safety design redundancy are much higher than those for ships sailing in non-ice-covered areas. Therefore, real-time measurement of ice forces on the hull is of great importance to ensuring the safety and performance of ships.

[0003] Existing ice force measurements can be achieved by installing local sensors (such as pressure sensors), but this method is costly, complex to install, and difficult to cover the entire hull. Another method is to predict ice force through model tests or numerical simulations, but verification on actual ships is difficult, and it is hard to guarantee the accuracy of ice force prediction results. Summary of the Invention

[0004] This application addresses the aforementioned problems and technical requirements by proposing a method for inverting ship ice forces based on motion response monitoring data. The technical solution of this application is as follows:

[0005] A method for inverting ship ice forces based on motion response monitoring data includes the following steps: The motion response data of each degree of freedom of the ship when it is sailing in ice area are collected in real time by inertial measurement equipment deployed on the ship, and the motion response at the center of gravity of the ship is determined based on the principle of rigid body kinematics. A six-degree-of-freedom kinematic model of a ship is constructed under ice conditions. The six-degree-of-freedom kinematic model indicates the relationship between the ship's motion response in each degree of freedom and the ice forces it experiences. Based on a six-degree-of-freedom kinematic model and combined with the motion response at the ship's center of gravity, the ice forces acting on the hull are inverted using an inverse solution method.

[0006] Its further technical solution is that the expression of the six-degree-of-freedom kinematic model is:

[0007] in, It is a quality matrix. It is an additional mass matrix. It is the damping force coefficient matrix. It is the restoring force coefficient matrix. It is an acceleration vector. It is a velocity vector. It is a displacement vector. It is the ice force vector. These respectively represent the directions of swaying, rolling, heaving, pitching, rolling, and swaying.

[0008] A further technical solution involves using a reverse engineering method to invert the ice forces acting on the hull, including: Substituting the motion response at the ship's center of gravity into a six-degree-of-freedom kinematic model, the equivalent ice force vector acting at the ship's center of gravity is obtained. Based on the equivalent ice force vector at the ship's center of gravity Determine the ice forces acting on the hull.

[0009] A further technical solution is that the points of ice force application on the hull include the ship's center of gravity and the bow; Determine the ice force acting at the ship's center of gravity , Determine the ice force acting at the bow. , in, It is the equivalent ice force vector The component in the oscillation direction, It is the equivalent ice force vector The component in the sway direction, It is the equivalent ice force vector The component in the direction of heave. It is the equivalent ice force vector The component in the roll direction, It is the equivalent ice force vector The component in the bow roll direction, It is the distance between the point of application of ice force at the bow and the center of gravity of the ship.

[0010] A further technical solution involves placing the inertial measurement equipment at a location that meets the required distance from the ship's center of gravity; collecting motion response data for each degree of freedom at the installation location of the inertial measurement equipment in real time; and determining the motion response of each degree of freedom at the ship's center of gravity by combining the geometric relationship between the installation location and the ship's center of gravity.

[0011] The further technical solution involves determining the motion response of each degree of freedom at the ship's center of gravity, including: Real-time acquisition of acceleration data in the sway, roll, and heave directions, as well as velocity data in the pitch, roll, and yaw directions at the installation location; integration of the acceleration data at the installation location yields the velocity and displacement in the sway, roll, and heave directions at the installation location; differentiation of the velocity data at the installation location yields the acceleration in the pitch, roll, and yaw directions at the installation location; integration of the velocity data at the installation location yields the displacement in the pitch, roll, and yaw directions at the installation location. The velocities of each degree of freedom at the ship's center of gravity are equal to the velocities at the installation position; the accelerations of each degree of freedom at the ship's center of gravity are equal to the accelerations at the installation position; and the displacements of each degree of freedom at the ship's center of gravity are equal to the displacements at the installation position.

[0012] The further technical solution is to predetermine the parameters in the mass matrix, additional mass matrix, damping force coefficient matrix and restoring force coefficient matrix of the six-degree-of-freedom kinematic model based on potential flow theory or fluid dynamics simulation, and combined with ice water pool model test.

[0013] The further technical solution involves obtaining the parameters in the restoring force coefficient matrix through constrained model tests and CFD still water disturbance simulations in an ice-free water tank; conducting ship-ice collision tests in an ice-water tank to determine the parameters in the added mass matrix and damping force coefficient matrix under the ice-water mixed flow field; and verifying and fine-tuning the model coefficients online based on the actual ship's navigation data in ice-free calm water.

[0014] The beneficial technical effects of this application are: This application discloses a method for inverting ice forces on a ship based on motion response monitoring data. Based on the kinematic model of an ice-covered ship, it can efficiently and conveniently invert the ice forces experienced by the ship by using a portable inertial measurement equipment to monitor the actual ship data. It can assess the ice force situation during the ship's navigation in real time and determine the ship's navigation status. It can be used to evaluate the energy consumption, design, and safe operation of ice-covered ships, and helps to optimize the ship's hull shape, propulsion system, and navigation route.

[0015] Considering the localized effects of ice forces, this study analyzes the location of ice force application and, combined with the independent action of forces and moments in rigid body mechanics, models the ice forces on the ship's center of gravity and bow moment in ice-covered areas separately. This avoids cross-coupling calculations of forces and moments, reduces the dimensionality and complexity of the equations, and improves the efficiency of ice force calculations. Furthermore, since the reliability of the equations of motion has been verified through pool collision tests, the calculations of the separated forces and moments are still based on the validated theoretical framework, effectively ensuring the reliability of the results. Simultaneously, by decoupling the ice forces at the ship's center of gravity and bow, the translational resultant force is directly derived from the equations of motion when solving for the ice force at the center of gravity, meeting core requirements such as propulsion system matching and energy consumption analysis, with low computational load and high real-time performance. Only when analyzing hull attitude stability (such as roll risk) is the moment derived from the relative position of the bow application point to the ship's center of gravity, avoiding redundant calculations. This layered strategy of on-demand calculation significantly improves engineering practicality. Attached Figure Description

[0016] Figure 1 This is a flowchart of the ship hull ice force inversion method.

[0017] Figure 2 This is a schematic diagram showing the location of the ice force. Detailed Implementation

[0018] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0019] This application discloses a method for inverting ship ice forces based on motion response monitoring data. Please refer to [the relevant documentation / reference]. Figure 1 The flowchart shown illustrates the specific steps of this method as follows: Step 1: Use inertial measurement equipment installed on the ship to collect motion response data of each degree of freedom of the ship in real time when it is sailing in ice-covered areas.

[0020] Due to watertight layout and narrow equipment compartments, it is difficult to directly install inertial measurement equipment (INS) at the ship's center of gravity. The installation location of the INS directly determines the accuracy of the motion response at the ship's center of gravity; therefore, it is necessary to ensure that the installation location of the INS meets certain requirements. This application places the INS at a location that meets the required distance from the ship's center of gravity, specifically in the compartment closest to the center of gravity. The ship's center of gravity data can be confirmed by consulting hull drawings and conducting on-site surveys.

[0021] Step 2: Determine the motion response at the ship's center of gravity based on the principles of rigid body kinematics.

[0022] The motion response data of each degree of freedom at the installation location of the inertial measurement equipment are collected in real time, and the motion response of each degree of freedom at the ship's center of gravity is determined by combining the geometric relationship between the installation location and the ship's center of gravity.

[0023] Motion response data for each degree of freedom includes velocity, acceleration, and displacement. Specifically, determining the motion response of each degree of freedom at the ship's center of gravity includes: Real-time acceleration data in the longitudinal, lateral, and helical directions at the installation location are collected, respectively. , , And the speed data in the pitch, roll, and bow directions, respectively , , Integrating the acceleration data at the installation location yields the velocity and displacement in the longitudinal, transverse, and helical directions at the installation location. For example, at any given time... At a certain time interval (The value is typically taken as 0.1s) the velocity in the oscillation direction. and displacement We obtain the results from formulas (1) and (2) respectively: (1) (2) Differentiating the velocity data at the installation location yields the accelerations in the pitch, roll, and bow directions at that location. For example, the acceleration in the pitch direction... It can be calculated using formula (3): (3) Similarly, the velocity data at the installation location is integrated to obtain the displacement in the pitch, roll, and bow directions at the installation location; Since the ship's overall structure is a rigid body, elastic and plastic deformations are not considered. The velocity, acceleration, and angular displacement at the ship's center of gravity are consistent with those at the installation location of the inertial measurement equipment. Therefore, the velocities of each degree of freedom at the ship's center of gravity are equal to the velocities at the installation location, i.e. , It is the velocity of the installation position at degree of freedom i. It is the velocity of the ship's center of gravity at degree of freedom i; the acceleration of each degree of freedom at the ship's center of gravity is equal to the acceleration at the installation position, i.e. , It is the acceleration of the installation position at degree of freedom i. It is the acceleration of the ship's center of gravity at degree of freedom i; the displacement of each degree of freedom at the ship's center of gravity is equal to the displacement at the installation position, i.e. , It is the displacement of the installation position at degree of freedom i. It is the displacement of the ship's center of gravity at degree i.

[0024] Step 3: Construct a six-degree-of-freedom kinematic model of the ship under ice conditions. The six-degree-of-freedom kinematic model indicates the relationship between the ship's motion response in each degree of freedom and the ice forces it experiences.

[0025] Based on actual ship data, the ship's center of gravity was determined, and a ship-based coordinate system was established with the center of gravity as its origin. The positive x-axis of the ship-based coordinate system points towards the bow, the positive y-axis points towards the port side, and the positive z-axis points vertically upward. A six-degree-of-freedom kinematic model considering the ship's six degrees of freedom motion was established based on the potential flow method. The key coefficient matrix was obtained through kinematic analysis under typical sea states, and the reliability of the kinematic equations was verified through ice-water tank collision tests.

[0026] In one example, the construction process of a six-degree-of-freedom kinematic model can be as follows: First, a geometric model of the hull is established and discretized into a mesh. Then, based on typical operating conditions, the design calculation frequency and wave direction are determined. Based on potential flow theory or fluid dynamics simulation, and combined with ice-water tank model tests, the parameters in the mass matrix, additional mass matrix, damping force coefficient matrix, and restoring force coefficient matrix of the six-degree-of-freedom kinematic model are pre-determined. Specifically, constrained model tests and CFD still water disturbance simulations are conducted in an ice-free tank to obtain the parameters in the restoring force coefficient matrix. For example, frequency domain potential flow calculation software (such as AQWA) is used to calculate the radiation problem (the hull undergoes simple harmonic motion of unit amplitude) to obtain the additional mass matrix and damping force coefficient matrix, and to calculate the diffraction problem (fixed hull, wave incidence) to obtain the restoring force coefficient matrix. Ship-ice collision tests are conducted in an ice-water tank to determine the parameters in the additional mass matrix and damping force coefficient matrix under ice-water mixed flow fields. To further improve the adaptability of the constructed six-degree-of-freedom kinematic model to actual operating conditions, the model coefficients are verified and fine-tuned online based on the actual ship's navigation data in ice-free calm water. Pre-determining parameters through simulation and experimentation, and then verifying and adjusting them using actual ship data, can effectively improve the accuracy of ice force calculation results.

[0027] The expression for the six-degree-of-freedom kinematic model of the entire ship is as follows: (4) in, It is a quality matrix. It is an additional mass matrix. It is the damping force coefficient matrix. It is the restoring force coefficient matrix. It is an acceleration vector. It is a velocity vector. It is a displacement vector. It is the ice force vector. These respectively represent the directions of swaying, rolling, heaving, pitching, rolling, and swaying.

[0028] Step 4: Based on the six-degree-of-freedom kinematic model and combined with the motion response at the ship's center of gravity, the ice force acting on the hull is inverted using the inverse solution method.

[0029] Based on the motion responses of each degree of freedom obtained in step 2, the ice forces acting on the hull can be inferred from the six-degree-of-freedom motion model. In one embodiment, inverting the ice forces acting on the hull using the inverse solution method includes: Substituting the motion response at the ship's center of gravity into a six-degree-of-freedom kinematic model, the equivalent ice force vector acting at the ship's center of gravity is obtained. Based on the equivalent ice force vector at the ship's center of gravity Determine the ice forces acting on the hull.

[0030] Considering that the ship's center of gravity is the benchmark reference point for ship motion analysis, the ice force at the center of gravity is the basis for inverting the equivalent ice force vector. When a ship navigates in ice-covered areas, the bow is the primary point of direct collision with the ice layer. The compressive and impact forces exerted by the ice on the hull are mainly concentrated in the bow area, making it the core point of application of ice forces. Therefore, if... Figure 2 As shown, the points of application of ice forces on the hull include the ship's center of gravity and the bow: Determine the ice force acting at the ship's center of gravity. At this point, the ice force only produces a translational effect and has no additional torque (because the lever arm is 0), so it is only necessary to calculate the resultant force of the three translational degrees of freedom; For the bow, assuming the collision surface between the hull and sea ice is symmetrical along the xoz plane and the collision point is on the x-axis, determine the ice force acting at the bow. ; in, It is the equivalent ice force vector The component in the oscillation direction, It is the equivalent ice force vector The component in the sway direction, It is the equivalent ice force vector The component in the direction of heave. It is the equivalent ice force vector The component in the roll direction, It is the equivalent ice force vector The component in the bow roll direction, It is the distance between the point of application of ice force at the bow and the center of gravity of the ship.

[0031] Compared to traditional models that require simultaneous solution of forces and moments across six degrees of freedom, this application models the ice forces on the center of gravity and bow moment of a ship in ice-covered conditions separately. This avoids the cross-coupling of force and moment calculations, reduces the dimensionality and complexity of the equations, and helps improve the efficiency of ice force calculations. By simplifying the model to balance accuracy and computational efficiency, the bow (the main force-bearing area) and center of gravity (the motion reference point) are selected as key points of application. This simplifies the mapping relationship between ice forces and motion response while ensuring inversion accuracy, enabling real-time ice force monitoring during ship navigation, which is of great significance for practical engineering applications.

[0032] In addition, a single ice force can be explicitly analyzed according to the engineering analysis requirements, such as the ice force in the longitudinal direction. It is a key parameter for analyzing the effectiveness of ship propulsion systems, and the relevant data can support the analysis of ship navigation safety.

[0033] This application provides a non-invasive ice force measurement method that uses inertial sensors and motion equation inversion to avoid the need for a large number of pressure sensors, making it easier to implement on actual ships. Furthermore, it considers the influence of the location of ice force application, resulting in inversion results that are closer to reality. After implementation, it can effectively interpret the ice force characteristics during ship navigation in ice-covered areas, improving navigation safety and logistical support capabilities.

[0034] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.

Claims

1. A method for inverting ship ice forces based on motion response monitoring data, characterized in that, The ship hull ice force inversion method includes: The motion response data of each degree of freedom of the ship when it is sailing in ice area are collected in real time by inertial measurement equipment deployed on the ship, and the motion response at the center of gravity of the ship is determined based on the principle of rigid body kinematics. A six-degree-of-freedom kinematic model of a ship is constructed under ice conditions. The six-degree-of-freedom kinematic model indicates the relationship between the ship's motion response in each degree of freedom and the ice forces it experiences. Based on the aforementioned six-degree-of-freedom kinematic model and combined with the motion response at the ship's center of gravity, the ice forces acting on the hull are inverted using an inverse solution method.

2. The hull ice force inversion method according to claim 1, characterized in that, The expression for the six-degree-of-freedom kinematic model is: in, It is a quality matrix. It is an additional mass matrix. It is the damping force coefficient matrix. It is the restoring force coefficient matrix. It is an acceleration vector. It is a velocity vector. It is a displacement vector. It is the ice force vector. These respectively represent the directions of swaying, rolling, heaving, pitching, rolling, and swaying.

3. The hull ice force inversion method according to claim 1, characterized in that, The method of inverting the ice forces acting on the hull using the reverse solution method includes: Substituting the motion response at the ship's center of gravity into the six-degree-of-freedom kinematic model, the equivalent ice force vector acting at the ship's center of gravity is obtained. Based on the equivalent ice force vector at the ship's center of gravity Determine the ice forces acting on the hull.

4. The hull ice force inversion method according to claim 3, characterized in that, The points of ice force application on the hull include the ship's center of gravity and the bow; Determine the ice force acting at the ship's center of gravity , Determine the ice force acting at the bow. , in, It is the equivalent ice force vector The component in the oscillation direction, It is the equivalent ice force vector The component in the sway direction, It is the equivalent ice force vector The component in the heave direction, It is the equivalent ice force vector The component in the roll direction, It is the equivalent ice force vector The component in the bow roll direction, It is the distance between the point of application of ice force at the bow and the center of gravity of the ship.

5. The hull ice force inversion method according to claim 1, characterized in that, The inertial measurement equipment is installed at a location that meets the required distance from the ship's center of gravity; the motion response data of each degree of freedom at the installation location of the inertial measurement equipment are collected in real time, and the motion response of each degree of freedom at the ship's center of gravity is determined by combining the geometric relationship between the installation location and the ship's center of gravity.

6. The hull ice force inversion method according to claim 5, characterized in that, Determining the motion response of each degree of freedom at the ship's center of gravity includes: Real-time acquisition of acceleration data in the sway, roll, and heave directions, as well as velocity data in the pitch, roll, and yaw directions at the installation location; integration of the acceleration data at the installation location yields the velocity and displacement in the sway, roll, and heave directions at the installation location; differentiation of the velocity data at the installation location yields the acceleration in the pitch, roll, and yaw directions at the installation location; integration of the velocity data at the installation location yields the displacement in the pitch, roll, and yaw directions at the installation location. The velocities of each degree of freedom at the ship's center of gravity are equal to the velocities at the installation position; the accelerations of each degree of freedom at the ship's center of gravity are equal to the accelerations at the installation position; and the displacements of each degree of freedom at the ship's center of gravity are equal to the displacements at the installation position.

7. The hull ice force inversion method according to claim 1, characterized in that, Based on potential flow theory or fluid dynamics simulation, and combined with ice water pool model tests, the parameters in the mass matrix, additional mass matrix, damping force coefficient matrix, and restoring force coefficient matrix of the six-degree-of-freedom kinematic model are determined in advance.

8. The hull ice force inversion method according to claim 7, characterized in that, The parameters in the restoring force coefficient matrix were obtained by constrained model tests and CFD still water disturbance simulations in an ice-free water tank; ship-ice collision tests were conducted in an ice-water tank to determine the parameters in the added mass matrix and damping force coefficient matrix under the ice-water mixed flow field; and the model coefficients were verified and fine-tuned online based on the navigation data of the actual ship in ice-free calm water.

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