Method for calculating underwater transient impact response of stern structure in steering process

Abstract

The invention provides a stern structure underwater transient impact response calculation method in a steering process. The method comprises the following steps: establishing a kinetic model of an electro-hydraulic steering device based on Adams; the hydrodynamic torque of a rudder shaft of the electro-hydraulic steering device in the steering process, the hydraulic impact load in a hydraulic cylinder and the displacement of a piston rod serve as input of a dynamic model, dynamic analysis of the electro-hydraulic steering device under the steering working condition is conducted, and the impact load at the joint of the electro-hydraulic steering device and the stern structure is obtained; the impact load at the joint is loaded to the stern structure, an acoustic-solid coupling finite element method is adopted for solving, transient impact time-domain response of the stern structure is obtained, and the time-domain characteristic and the frequency-domain characteristic of the transient impact time-domain response are analyzed.

Description

Technical Field

[0001] The present invention relates to the technical field of ship impact vibration, and in particular to a method for calculating the underwater transient impact response of a stern structure during steering. Background Art

[0002] The steering system is one of the main sources of vibration and noise under stealth conditions. Since the steering device and the hull are typically rigidly connected, the structural vibration caused by the steering impact load is more easily transmitted to the hull, posing a significant threat to the ship's stealth. Therefore, studying the calculation method for the transient impact response of the stern structure under steering loads is of great significance for reducing vibration and noise in the steering system.

[0003] Electro-hydraulic steering systems offer the advantages of hydraulic systems with high load capacity, servo motor control efficiency, high energy recovery, and simple structure, making them increasingly popular on ships. Research on steering systems involves multiple disciplines, including steering servo systems, rudder blade hydrodynamic loads, steering mechanism dynamics, and structural impact vibration.

[0004] In terms of the electro-hydraulic steering servo system, the static and dynamic performance of the system can be improved by using a "notch filter + nonlinear PID + feedforward" controller. The exponential variable damping sliding mode control algorithm can also be used to effectively improve the system's tracking accuracy in the low-frequency band and significantly improve the system's speed.

[0005] To study the transient impact response and radiated noise caused by the steering gear during maneuvering, it is first necessary to determine the primary impact loads exerted by the steering gear on the hull structure. To address the hydrodynamic loads on the rudder blade during maneuvering, researchers have numerically simulated the hydrodynamic loads on different rudder blades and used circulating water tank maneuverability tests to obtain the hydrodynamic coefficients of a series of scaled-down rudder blade models. Other researchers have compared the partial hydrodynamic performance of cross-rudder and X-rudder submarines using CFD (Computational Fluid Dynamics) numerical methods, concluding that the X-rudder submarine has superior drag and lift performance compared to the cross-rudder submarine.

[0006] To address the hydraulic shock loads generated in ship steering hydraulic systems, some researchers have established mathematical models of electro-hydraulic servo valves and loaded hydraulic cylinders. To address the issue of external loads affecting the operational stability of electro-hydraulic load simulation hydraulic systems, a pilot-operated proportional pressure reducing valve was installed to reduce the pressure shock caused by external loads. Other researchers have established a mathematical model of an electro-hydraulic steering device and simulated and analyzed the hydraulic shock therein, systematically analyzing the effects of structural parameters, motor speed, and external loads on the hydraulic shock. To address the significant hydraulic shock caused by the frequent step-by-step switching of the reversing valve in the electro-hydraulic servo system, a control strategy has been proposed that actively controls the hydraulic pump pressure and sets a closed-loop booster cylinder position plus PID (proportional, integral, and differential) regulation to continuously control the reversing valve opening signal, significantly eliminating the hydraulic shock.

[0007] In the study of the kinematic and dynamic characteristics of steering gears, some researchers have established mechanical and hydraulic transmission systems in ADAMS, used MATLAB / Simulink to create a simulation model for the hydraulic steering gear control system, and completed a joint simulation of electromechanical and hydraulic integration. Others, focusing on the transmission mechanism of a two-degree-of-freedom steering gear, used ADAMS software to establish a mechanical dynamics simulation model based on multi-body contact theory, and obtained the speed and meshing force of each gear.

[0008] In the field of ship impact vibration, most studies use modal superposition analysis in the frequency domain. This method is primarily used to calculate steady-state vibration and noise. However, research on transient impact vibration of ship structures is relatively rare. To address the shortcomings of frequency-domain prediction methods for ship structural vibration and noise, such as the tendency to miss peaks, some have proposed time-domain prediction methods for ship structural vibration and noise, establishing a workflow for this method. One study developed a method for identifying the transmission path of transient noise excitation sources in ships, and using a full-scale ship as a test platform, accurately determined the primary transmission path from the transient excitation source vibration to radiated noise. One study addressed the transient vibration of cabins generated by ice floes on ships sailing in ice-covered areas by simplifying the ice floe impact load into a triangular wave time-domain curve and calculating the impact response of the ship structure under ice floe impact. Regarding the transient impact of aircraft landing, one study used the landing deck of a ship as a research object to investigate the influence of impact load parameters such as landing impulse, pulse width, and amplitude on the transient impact response.

[0009] The results of literature review show that there are many literatures that conduct independent research on the hydrodynamic load of rudder blades, the control algorithm of electro-hydraulic steering servo system and the hydraulic shock of steering device. However, there are relatively few studies that consider the entire steering system as a whole and study the impact load of the steering device on the hull and the vibration impact of the hull caused by the steering device.

[0010] Therefore, it is urgent to propose a new calculation method for the underwater transient impact response of the stern structure during steering. Summary of the Invention

[0011] In view of the problems existing in the prior art, an embodiment of the present invention provides a method for calculating the underwater transient impact response of a stern structure during steering.

[0012] The present invention provides a method for calculating the underwater transient impact response of a stern structure during steering, comprising:

[0013] Establish the dynamic model of electro-hydraulic steering device based on Adams;

[0014] Using the rudder shaft hydrodynamic torque, hydraulic impact load in the hydraulic cylinder, and piston rod displacement of the electro-hydraulic steering device during steering as inputs to the dynamic model, a dynamic analysis of the electro-hydraulic steering device under steering conditions is performed to obtain the impact load at the connection between the electro-hydraulic steering device and the stern structure;

[0015] The impact load at the connection is applied to the stern structure, and the acoustic-solid coupling finite element method is used to solve the transient impact time domain response of the stern structure. The FFT method is then used to analyze its frequency domain characteristics.

[0016] The present invention provides a method for calculating the underwater transient impact response of the stern structure during steering. The method aims to predict the transient impact response of the stern structure under steering loads. Based on a dynamic model of a steering device, combined with the hydrodynamic torque of the rudder shaft, the steering servo system, and the hydraulic impact load, the method obtains the impact load of the steering device on the stern structure under steering conditions through dynamic simulation of the steering device. The method also simulates and analyzes the transient impact response of the stern structure based on the transient finite element method, performs time domain analysis and frequency domain analysis, and has high calculation accuracy and a simple method. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 1 is a flow chart of a method for calculating the underwater transient impact response of a stern structure during steering provided by the present invention;

[0019] Figure 2 It is a schematic diagram of the rudder angle time history curve in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0020] Figure 3It is a schematic diagram of the steering device and the stern structure in the method for calculating the underwater transient impact response of the stern structure during steering provided by the present invention;

[0021] Figure 4 This is a schematic diagram of the steering device motion in the method for calculating the underwater transient impact response of the stern structure during steering provided by the present invention;

[0022] Figure 5 It is a schematic diagram of the dynamic model of the steering device in the calculation method of the underwater transient impact response of the stern structure during the steering process provided by the present invention;

[0023] Figure 6 It is a schematic diagram of the revolute pair in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0024] Figure 7 It is a schematic diagram of the background domain grid and boundary conditions in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0025] Figure 8 Schematic diagram of the stern grid in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0026] Figure 9 It is a steering schematic diagram in the method for calculating the underwater transient impact response of the stern structure during steering provided by the present invention;

[0027] Figure 10 It is a schematic diagram of the time history curve of the rudder shaft torque in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0028] Figure 11 It is a schematic diagram of the working principle of the electro-hydraulic servo actuation system in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0029] Figure 12 This is a closed-loop control block diagram of the electro-hydraulic steering servo system in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0030] Figure 13 It is a schematic diagram of a time history curve of a hydraulic shock load in the calculation method of the underwater transient shock response of the stern structure during steering provided by the present invention;

[0031] Figure 14 It is a schematic diagram of a pressure difference time history curve in the method for calculating the underwater transient impact response of the stern structure during steering provided by the present invention;

[0032] Figure 15 Schematic diagram of the time history curve of the impact load at ZC1 in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0033] Figure 16 It is a schematic diagram of the transient impact response prediction process in the method for calculating the underwater transient impact response of the stern structure during steering provided by the present invention;

[0034] Figure 17 It is a schematic diagram of the geometric model of the stern structure in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0035] Figure 18 It is a schematic diagram of the finite element model of the stern structure and the water area in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0036] Figure 19 It is a schematic diagram of the arrangement of vibration assessment points in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0037] Figure 20 Schematic diagram of the mean square vibration velocity time history curve of the stern shell in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0038] Figure 21 It is a schematic diagram of a vibration acceleration time history curve in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention;

[0039] Figure 22 It is a schematic diagram of the frequency domain curve of the vibration acceleration level in the calculation method of the underwater transient impact response of the stern structure during steering provided by the present invention. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0041] The following combination Figures 1 to 22 The present invention describes a method for calculating the underwater transient impact response of a stern structure during steering, comprising:

[0042] Step 101, establishing a dynamic model of the electro-hydraulic steering device based on Adams;

[0043] Step 102: Using the rudder shaft hydrodynamic torque, hydraulic impact load in the hydraulic cylinder, and piston rod displacement of the electro-hydraulic steering device during steering as inputs to the dynamic model, a dynamic analysis of the electro-hydraulic steering device under steering conditions is performed to obtain the impact load at the connection between the electro-hydraulic steering device and the stern structure.

[0044] Step 103 : applying the impact load at the connection to the stern structure, solving the problem using an acoustic-solid coupling finite element method to obtain a transient impact time-domain response of the stern structure, and analyzing its frequency-domain characteristics using an FFT method.

[0045] Typical steering conditions that can be selected in this embodiment are shown in Table 1:

[0046] Table 1 Steering conditions

[0047]

[0048] During steering, first accelerate to the target steering speed at a fixed steering acceleration, then maintain the fixed steering speed. Finally, decelerate at a fixed steering acceleration until the steering speed returns to zero. At this point, the rudder angle should be exactly at the target maximum rudder angle. Reverse steering is then performed, i.e., after deceleration, reverse acceleration is performed. This process is similar to forward steering, and finally, the rudder angle returns to 0°.

[0049] In this embodiment, the rudder angle time history curve of the steering condition is selected as follows: Figure 2 shown. Figure 2 The steering motion in the vehicle can be decomposed into: acceleration stage (0-1s), uniform speed stage (1-6s), deceleration and reverse acceleration stage (6-8s), uniform speed stage 2 (8-13s) and deceleration stage (13-14s).

[0050] The electro-hydraulic steering device mainly consists of three parts: the rudder blade part that realizes the adjustment of ship movement, the transmission device part that realizes the rotation of the rudder blade, and the electro-hydraulic system that drives the transmission device to move. Figure 3 shown.

[0051] The electro-hydraulic steering system works as follows: After the electro-hydraulic steering servo system inputs a steering command signal to the controller, the system drives the hydraulic pump through the motor. The pump then feeds high-pressure oil into the system. This oil then flows through the oil pipeline into the hydraulic cylinder, creating a pressure differential between the two chambers of the hydraulic cylinder. This pressure differential pushes the piston rod, ultimately rotating the rudder shaft and achieving steering. The rotation of the rudder blade generates a hydrodynamic torque on the rudder shaft. The pressure differential across the hydraulic cylinder changes with the external load, balancing the load on the piston rod transferred by the transmission rod.

[0052] The servo system controls the reciprocating motion of the piston rod by controlling the forward and reverse rotation of the motor; it controls the output flow of the hydraulic pump by controlling the output speed of the motor, thereby controlling the movement speed of the piston rod.

[0053] The load and drive input of the dynamic model of the electro-hydraulic steering device mainly include three parts, namely the hydrodynamic torque of the rudder shaft, the internal oil load of the hydraulic cylinder and the piston rod displacement drive.

[0054] Rudder shaft hydrodynamic torque: This refers to the time-varying torque exerted by the fluid on the rudder shaft during steering. This torque is related to factors such as ship speed, steering speed, steering acceleration, and maximum rudder angle.

[0055] Internal hydraulic cylinder fluid load: During steering, the hydraulic cylinder creates a pressure differential on both sides of the piston to propel it. This pressure differential creates a shock effect. The pressure differential overcomes the load inertia, damping, and external loads, representing the hydraulic shock load, which reflects the internal fluid shock effect.

[0056] Piston Rod Displacement Drive: This method drives the piston rod by applying a forced displacement. This displacement drive simulates both the actual piston rod motion and the pressure differential acting on the piston. The piston rod displacement time history is inversely calculated based on the rudder angle time history.

[0057] In summary, the loads applied are: hydrodynamic torque on the rudder shaft, pressure difference on the hydraulic cylinder, displacement drive on the piston rod and hydraulic impact load on the piston rod.

[0058] This embodiment aims to predict the transient impact response of the stern structure under steering loads. Based on the dynamic model of the steering device, combined with the hydrodynamic torque of the rudder shaft, the steering servo system, and the hydraulic impact load, the impact load of the steering device on the stern structure under steering conditions is obtained through dynamic simulation of the steering device. The transient impact response of the stern structure is simulated and analyzed based on the transient finite element method. The calculation has high accuracy and a simple method.

[0059] Based on the above embodiment, the dynamic model of the electro-hydraulic steering device in this embodiment includes a rudder blade for adjusting the ship's motion, a transmission device for rotating the rudder blade, and an electro-hydraulic system for driving the transmission device.

[0060] The rudder shaft of the electro-hydraulic steering device is connected to the stern structure at the upper part of the stabilizer wing through a connecting bearing, and the bearing is simulated by a revolute pair;

[0061] The piston rod and the transmission rod in the transmission device are hinged, and the hinge is simulated by a revolute pair;

[0062] The hydraulic cylinder in the electro-hydraulic system is connected to the base of the stern housing via a bearing, and the bearing is simulated by a revolute pair;

[0063] The hydraulic cylinder matches the movement of the piston rod by rotating, and contact is set between the piston rod and the hydraulic cylinder.

[0064] The steering gear dynamics model established in this embodiment mainly includes a hydraulic cylinder, a transmission device, and a rudder blade. The rudder shaft is constrained by a bearing above the stabilizer, and the piston rod and the transmission rod are hinged. The hydraulic cylinder is connected to the stern housing base through a bearing, and the hydraulic cylinder matches the movement of the piston rod by rotating at a small angle. The motion diagram of the steering gear is shown in the figure below. Figure 4 shown.

[0065] Steering gear dynamics model Figure 5 As shown, combined Figure 4 , define the Cartesian coordinate system of the electro-hydraulic steering device: the axial direction of the piston rod is the x-axis, the width direction of the hydraulic cylinder is the z-axis, and the axial direction of the transmission rod is the y-axis.

[0066] like Figure 6 As shown in the figure, the constraints between the steering gear and the stern structure are as follows: the bearing between the hydraulic cylinder and the stern housing base is simulated using a revolute joint; the connecting bearing between the rudder shaft and the stabilizer fin is simulated using a revolute joint. Internal constraints on the steering gear are as follows: the articulation between the piston rod and the transmission rod is simulated using a revolute joint; and contact is established between the piston, piston rod, and hydraulic cylinder.

[0067] Based on the above embodiment, this embodiment further includes, before using the rudder shaft hydrodynamic torque, hydraulic impact load in the hydraulic cylinder, and piston rod displacement of the electro-hydraulic steering device during steering as inputs to the dynamic model:

[0068] The hydrodynamic torque of the rudder shaft during steering is used as the load input of the dynamic model, and the time history curve of the hydrodynamic torque of the rudder shaft is obtained by monitoring the normal force on the rudder blade;

[0069] Reverse-calculating the time history curve of the rudder angle of the electro-hydraulic steering device to obtain the time history curve of the piston rod displacement;

[0070] The piston rod displacement and the rudder shaft hydrodynamic torque during the steering process are used as inputs of the dynamic model to obtain a time history curve of the force acting on the piston rod by the transmission rod;

[0071] According to the time history curve of the force acting on the piston rod by the transmission rod, the hydraulic impact load in the hydraulic cylinder is calculated based on the mathematical model of the electro-hydraulic steering servo system.

[0072] Based on the above embodiment, the calculation formula of the hydraulic impact load in the hydraulic cylinder in this embodiment is:

[0073] F cj =AP r -Fr -F I -F B

[0074] Among them, F cj is the hydraulic impact load in the hydraulic cylinder, P r is the hydraulic pressure difference on both sides of the hydraulic cylinder, F r is the force exerted on the piston rod by the transmission rod, A is the piston area, F I is the inertial force, F B is the damping force.

[0075] Based on the above embodiment, in this embodiment, the impact load at the connection is applied to the stern structure, and the finite element method of acoustic-solid coupling is used to solve the transient impact response of the stern structure, including:

[0076] The impact load at the connection is applied to the stern structure, and an acoustic-solid coupling finite element method is used to solve the problem based on an implicit dynamics solution method to obtain a transient impact time-domain response of the stern structure.

[0077] In this example, an acoustic-solid coupling finite element model of the stern structure was established in Abaqus. The external water area was simulated using acoustic units. The contact area between the external water area and the structure was connected by a tie constraint. To ensure that the sound waves are not reflected at the flow field cutoff, zero impedance was set at the external boundary of the flow field to achieve a non-reflective boundary. The finite element model of the stern structure and the water area is as follows: Figure 18 shown.

[0078] Based on the above embodiment, this embodiment further includes: after applying the impact load at the connection to the stern structure and solving the transient impact time domain response of the stern structure using the acoustic-solid coupling finite element method, the method further includes:

[0079] The mean square velocity of the stern shell and the normal acceleration of the hull near the base are selected from the transient impact time domain response of the stern structure as impact response evaluation features.

[0080] This embodiment aims to predict the transient impact response of the stern structure under steering loads. Based on the dynamic model of the steering device, combined with the hydrodynamic torque of the rudder shaft, the steering servo system, and the hydraulic impact load, the impact load of the steering device on the stern structure under steering conditions is obtained through dynamic simulation of the steering device. The transient impact response of the stern structure is simulated and analyzed based on the transient finite element method, and time domain analysis and frequency domain analysis are performed. The calculation has high accuracy and a simple method.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for calculating the underwater transient impact response of a stern structure during steering, characterized in that: include: Establish the dynamic model of electro-hydraulic steering device based on Adams; Using the rudder shaft hydrodynamic torque, hydraulic impact load in the hydraulic cylinder, and piston rod displacement of the electro-hydraulic steering device during steering as inputs to the dynamic model, a dynamic analysis of the electro-hydraulic steering device under steering conditions is performed to obtain the impact load at the connection between the electro-hydraulic steering device and the stern structure; The impact load at the connection is applied to the stern structure, and the acoustic-solid coupling finite element method is used to solve the problem to obtain the transient impact time domain response of the stern structure, and the frequency domain characteristics are analyzed using the FFT method.

2. The method for calculating the underwater transient impact response of the stern structure during steering according to claim 1 is characterized in that: The dynamic model of the electro-hydraulic steering device includes a rudder blade for adjusting the ship's motion, a transmission device for rotating the rudder blade, and an electro-hydraulic system for driving the transmission device. The rudder shaft of the electro-hydraulic steering device is connected to the stern structure through a bearing at the upper part of the stabilizer wing, and the bearing is simulated by a revolute pair; The piston rod and the transmission rod in the transmission device are hinged, and the hinge is simulated by a revolute pair; The hydraulic cylinder in the electro-hydraulic system is connected to the base of the stern housing via a bearing, and the bearing is simulated by a revolute pair; The hydraulic cylinder matches the movement of the piston rod by rotating, and contact is set between the piston rod and the hydraulic cylinder.

3. The method for calculating the underwater transient impact response of the stern structure during steering according to claim 1, characterized in that: Before using the rudder shaft hydrodynamic torque, hydraulic impact load in the hydraulic cylinder, and piston rod displacement of the electro-hydraulic steering device during steering as inputs to the dynamic model, the method further includes: The hydrodynamic torque of the rudder shaft during steering is used as the load input of the dynamic model, and the time history curve of the hydrodynamic torque of the rudder shaft is obtained by monitoring the normal force on the rudder blade; Reverse-calculating the time history curve of the rudder angle of the electro-hydraulic steering device to obtain the time history curve of the piston rod displacement; The piston rod displacement and the rudder shaft hydrodynamic torque during the steering process are used as inputs of the dynamic model to obtain a time history curve of the force acting on the piston rod by the transmission rod; According to the time history curve of the force acting on the piston rod by the transmission rod, the hydraulic impact load in the hydraulic cylinder is calculated based on the mathematical model of the electro-hydraulic steering servo system.

4. The method for calculating the underwater transient impact response of the stern structure during steering according to claim 3 is characterized in that: The calculation formula of the hydraulic impact load in the hydraulic cylinder is: F cj =AP r -F r -F I -F B Among them, F cj is the hydraulic impact load in the hydraulic cylinder, P r is the hydraulic pressure difference on both sides of the hydraulic cylinder, F r is the force exerted on the piston rod by the transmission rod, A is the piston area, F I is the inertial force, F B is the damping force.

5. The method for calculating the underwater transient impact response of the stern structure during steering according to claim 1, characterized in that: The impact load at the connection is applied to the stern structure, and an acoustic-solid coupling finite element method is used to solve the transient impact time domain response of the stern structure, including: The impact load at the connection is applied to the stern structure, and an acoustic-solid coupling finite element method is used to solve the problem based on an implicit dynamics solution method to obtain a transient impact time-domain response of the stern structure.

6. The method for calculating the underwater transient impact response of the stern structure during steering according to claim 1, characterized in that: After applying the impact load at the connection to the stern structure and solving the problem using an acoustic-solid coupling finite element method to obtain a transient impact time-domain response of the stern structure, the method further includes: The mean square velocity of the stern shell and the normal acceleration of the hull near the base are selected from the transient impact time domain response of the stern structure as impact response evaluation features.

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