CN-122021102-A - Floating parameter calculation method and system for stability analysis of seaplane

CN122021102ACN 122021102 ACN122021102 ACN 122021102ACN-122021102-A

Abstract

The invention provides a buoyancy parameter calculation method and a buoyancy parameter calculation system for stability analysis of a water plane, which are characterized in that a body coordinate system and a ground coordinate system are firstly established, a water plane model is established by modeling software, pitch angle, roll angle and yaw angle of the water plane model at a certain moment are obtained, a coordinate conversion matrix is further established, then vertical sub-coordinates of vector coordinates of each triangle surface element under the ground coordinate system and buoyancy moment of the water plane model at the moment are calculated by a specific calculation method, finally a buoyancy and buoyancy moment interpolation table is established based on the buoyancy and buoyancy moment of the water plane model at all moments, and a multidimensional interpolation algorithm is adopted, so that stability analysis of the water plane at different moments is realized, position and posture changes of the water plane relative to the ground can be accurately described, calculation accuracy of the buoyancy and the buoyancy moment is effectively improved, and variation trends of the buoyancy and the buoyancy moment under different flight states can be effectively captured.

Inventors

LIU GANG
JIANG JIAWEI
Ji Runjie
Mai Linrui
SHI SHENGZHE

Assignees

北京航空航天大学
中国特种飞行器研究所

Dates

Publication Date: 20260512
Application Date: 20251212

Claims (10)

1. A method of calculating buoyancy parameters for stability analysis of a seaplane, the buoyancy parameters including buoyancy and buoyancy torque, comprising the steps of: The method comprises the steps of establishing a coordinate system by taking an aircraft centroid as an origin, the aircraft nose direction of the aircraft as a longitudinal axis, the aircraft starboard direction as a transverse axis and the aircraft bottom direction as a vertical axis, and establishing a ground coordinate system by taking any point on a sea level as the origin, the initial motion direction of the aircraft as the longitudinal axis, the aircraft starboard direction parallel to the sea level as the transverse axis and the earth center as the vertical axis; The method comprises the steps of establishing a water plane model by using modeling software, obtaining pitch angle, roll angle and yaw angle of the water plane model based on a body coordinate system at a certain moment, establishing a coordinate conversion matrix based on the pitch angle, the roll angle and the yaw angle at the moment, dividing the water plane model into a plurality of triangular surface elements by adopting a finite element grid method at the body coordinate system, extracting normal vectors of each triangular surface element and coordinates of each vertex at the moment by using numerical calculation software, calculating the area of the triangular surface element and central coordinates positioned at the body coordinate system according to the coordinates of each vertex, and calculating the position vector of the center of each triangular surface element relative to the centroid according to the central coordinates; The method comprises the steps of coordinate conversion and buoyancy moment calculation, namely converting a central coordinate under a body coordinate system into a ground coordinate system according to a coordinate conversion matrix to obtain vector coordinates of each triangular surface element under the ground coordinate system, calculating pressure of each triangular surface element according to vertical sub-coordinates in the vector coordinates, calculating pressure of each triangular surface element according to the pressure and the area of the triangular surface element, calculating buoyancy of each triangular surface element according to the pressure and the normal direction, and calculating buoyancy moment of each triangular surface element according to the buoyancy and the position vector of the center of each triangular surface element relative to the centroid under the body coordinate system, and respectively calculating buoyancy and buoyancy moment of a water plane model at the moment according to the buoyancy and the buoyancy moment of each triangular surface element; And constructing an interpolation table and analyzing stability, namely constructing the buoyancy and buoyancy moment interpolation table based on the buoyancy and buoyancy moment of the water plane model at all moments by adopting a multidimensional interpolation algorithm, and inquiring the buoyancy and buoyancy moment of the water plane at corresponding moments in the buoyancy and buoyancy moment interpolation table according to the pitch angle, the roll angle, the yaw angle and the vertical coordinate in the vector coordinate in the body coordinate system at different moments so as to analyze the stability of the water plane at different moments.
2. The method for calculating buoyancy parameters for analysis of stability of a seaplane according to claim 1, wherein in the coordinate conversion and buoyancy moment calculation step, the calculation of buoyancy specifically includes: the method comprises the steps of firstly, respectively calculating a plurality of buoyancy components of each triangular surface element under a ground coordinate system according to pressure and normal vector, then converting each buoyancy component under the ground coordinate system into a body coordinate system according to a coordinate conversion matrix, and calculating the buoyancy of each triangular surface element according to each buoyancy component under the body coordinate system.
3. The method for calculating buoyancy parameters for analysis of stability of a water craft according to claim 1, wherein in the meshing and parameter calculating steps, an adaptive meshing refinement method is further adopted to perform fine meshing on a region where a wet surface of the water craft model is located, and at the same time, the mesh density of other regions except the region where the wet surface is located is kept within a preset density interval, so as to reduce the calculation amount.
4. The method for calculating buoyancy parameters for stability analysis of a seaplane according to claim 1, wherein in the meshing and parameter calculating steps, the modeling software comprises CAD software and 3D drawing software, and the numerical calculation software comprises MATLAB and finite element analysis software.
5. The method of calculating buoyancy parameters for analysis of stability of a seaplane according to claim 2, wherein the plurality of buoyancy components includes a buoyancy component of buoyancy in a longitudinal axis direction, a buoyancy component of buoyancy in a transverse axis direction, and a buoyancy component of buoyancy in a vertical axis direction.
6. A buoyancy parameter computing system for analyzing stability of a water plane is characterized by comprising a coordinate system building module, a grid division and parameter computing module, a coordinate conversion and buoyancy moment computing module and an interpolation table building and stability analyzing module which are connected in sequence, The system comprises a coordinate system establishing module, a ground coordinate system establishing module, a control module and a control module, wherein the coordinate system establishing module establishes a body coordinate system by taking an aircraft centroid as an origin, a aircraft nose direction as a longitudinal axis, a aircraft starboard direction as a transverse axis and a aircraft bottom direction as a vertical axis, and establishes a ground coordinate system by taking any point on a sea level as the origin, an aircraft initial motion direction as the longitudinal axis, a direction parallel to the sea level as the transverse axis and a geocenter as the vertical axis; The system comprises a grid dividing and parameter calculating module, a coordinate conversion matrix, a position vector calculating module and a position vector calculating module, wherein the grid dividing and parameter calculating module establishes a water plane model by using modeling software, acquires a pitch angle, a roll angle and a yaw angle of the water plane model based on a body coordinate system at a certain moment, constructs a coordinate conversion matrix based on the pitch angle, the roll angle and the yaw angle at the moment, divides the water plane model into a plurality of triangular surface elements by adopting a finite element grid method under the body coordinate system, and extracts the normal vector of each triangular surface element and the coordinates of each vertex at the moment through numerical calculation software; The system comprises a coordinate conversion and buoyancy moment calculation module, a vector coordinate calculation module, a pressure calculation module, a buoyancy calculation module and a buoyancy calculation module, wherein the coordinate conversion and buoyancy moment calculation module is used for converting a central coordinate under a body coordinate system into a ground coordinate system according to a coordinate conversion matrix to obtain a vector coordinate of each triangular surface element under the ground coordinate system, calculating the pressure of each triangular surface element according to a vertical sub-coordinate in the vector coordinate, calculating the pressure of each triangular surface element according to the pressure and the area of the triangular surface element, calculating the buoyancy of each triangular surface element according to the pressure and a normal vector, and calculating the buoyancy moment of each triangular surface element according to the buoyancy and the buoyancy moment of each triangular surface element, and calculating the buoyancy and the buoyancy moment of a water plane model at the moment according to the buoyancy and the buoyancy of each triangular surface element; the interpolation table construction and stability analysis module is used for constructing a buoyancy and buoyancy moment interpolation table based on buoyancy and buoyancy moment of the water plane model at all moments and adopting a multidimensional interpolation algorithm, and inquiring the buoyancy and buoyancy moment of the water plane at corresponding moments in the buoyancy and buoyancy moment interpolation table according to pitch angle, roll angle, yaw angle and vertical coordinate in vector coordinates in a body coordinate system at different moments, so as to realize stability analysis of the water plane at different moments.
7. The buoyancy parameter computing system for analysis of stability of a seaplane of claim 6, wherein the computing of buoyancy in the coordinate conversion and buoyancy moment computing module comprises: the method comprises the steps of firstly, respectively calculating a plurality of buoyancy components of each triangular surface element under a ground coordinate system according to pressure and normal vector, then converting each buoyancy component under the ground coordinate system into a body coordinate system according to a coordinate conversion matrix, and calculating the buoyancy of each triangular surface element according to each buoyancy component under the body coordinate system.
8. The floating parameter calculation system for analysis of stability of a water craft according to claim 6, wherein the meshing and parameter calculation module further adopts an adaptive meshing method to finely mesh the area of the wet surface of the water craft model, and simultaneously maintains the mesh density of the other areas except the area of the wet surface within a preset density interval, so as to reduce the calculation amount.
9. The buoyancy parameter computing system for use in a stability analysis of a seaplane according to claim 6, wherein the modeling software comprises CAD software and 3D cartography software, and the numerical computing software comprises MATLAB and finite element analysis software.
10. The buoyancy parameter computing system for use in analysis of stability of a water craft according to claim 7, wherein the plurality of buoyancy components includes a buoyancy component of buoyancy in a longitudinal axis direction, a buoyancy component of buoyancy in a transverse axis direction, and a buoyancy component of buoyancy in a vertical axis direction.

Description

Floating parameter calculation method and system for stability analysis of seaplane Technical Field The invention relates to the technical field of stability analysis of a water plane, in particular to a buoyancy parameter calculation method and a buoyancy parameter calculation system for stability analysis of the water plane. Background A water plane is an aircraft capable of taking off and landing on the water surface, and combines the characteristics of ships and planes. When a seaplane is taxiing on the surface or is ready to take off, its portion in contact with the water (typically the pontoon or hull) is subjected to various forces including gravity, engine thrust, aerodynamic forces, hydrodynamic forces, wave forces, and buoyancy. Where buoyancy is one of the main forces affecting the stability of the aircraft at low aircraft speeds. Buoyancy is the upward net force due to the pressure differential exerted by the liquid on the immersed object, which is equal to the weight of the displaced fluid according to archimedes' principle. For a water craft, buoyancy not only affects the resting state of the craft on the water surface, but also plays an important role in the process of accelerating the craft to obtain sufficient lift for takeoff. In addition, the buoyancy moment refers to a tendency to rotate about a certain axis due to uneven buoyancy distribution, which has a direct influence on the attitude stability of the aircraft. Conventional buoyancy and buoyancy torque calculation methods are generally based on theoretical models and empirical formulas, such as simplifying an aircraft into a series of geometric shapes to estimate its displacement, and predicting the buoyancy and its distribution from the characteristics of these shapes. However, this method has some limitations of 1) insufficient accuracy, that is, the theoretical model often assumes that the condition is ideal, ignoring the complex factors in actual operation, such as nonlinear flow effects, wave interference, etc., which may lead to inaccurate calculation results. 2) Real-time response is poor-conventional methods may employ simplified mathematical expressions in order to guarantee computational speed, but this makes it difficult to adapt to rapidly changing operating environments, such as the dynamic response of an aircraft at different speeds. 3) Inefficiency as seaplane designs become more complex, buoyancy analysis using traditional manual calculations or simple computer-aided tools becomes time consuming and error prone. Therefore, the calculation method for continuously improving the buoyancy and the buoyancy moment is still an important research direction in the field of design of the water plane. Disclosure of Invention Aiming at the problems of insufficient precision, poor real-time response, low efficiency and the like in the existing buoyancy and buoyancy moment calculation process, the invention provides a buoyancy parameter calculation method for analyzing the stability of a water plane, which can accurately describe the position and posture change of the water plane relative to the ground, improve the calculation precision of the buoyancy and the buoyancy moment, effectively capture the variation trend of the buoyancy and the buoyancy moment under different flight states and has remarkable rapidity, instantaneity and accuracy. The invention also relates to a buoyancy parameter calculation system for analyzing the stability of the water plane. The technical scheme of the invention is as follows: A method of calculating buoyancy parameters for stability analysis of a seaplane, the buoyancy parameters including buoyancy and buoyancy torque, comprising the steps of: The method comprises the steps of establishing a coordinate system by taking an aircraft centroid as an origin, the aircraft nose direction of the aircraft as a longitudinal axis, the aircraft starboard direction as a transverse axis and the aircraft bottom direction as a vertical axis, and establishing a ground coordinate system by taking any point on a sea level as the origin, the initial motion direction of the aircraft as the longitudinal axis, the aircraft starboard direction parallel to the sea level as the transverse axis and the earth center as the vertical axis; The method comprises the steps of establishing a water plane model by using modeling software, obtaining pitch angle, roll angle and yaw angle of the water plane model based on a body coordinate system at a certain moment, establishing a coordinate conversion matrix based on the pitch angle, the roll angle and the yaw angle at the moment, dividing the water plane model into a plurality of triangular surface elements by adopting a finite element grid method at the body coordinate system, extracting normal vectors of each triangular surface element and coordinates of each vertex at the moment by using numerical calculation software, calculating the area of the triangular surface element and cent