A solution method for the lift pressure of a full hovercraft

Abstract

The application relates to a solution method for the cushion pressure of a full-cushion hovercraft, and relates to the technical field of dynamic modeling of the full-cushion hovercraft. In order to solve the problem that the prior art cannot stably and accurately solve the cushion pressure values at different times, and is prone to accidents caused by uneven or out-of-control air cushion pressure, and is not conducive to the navigation safety of the hovercraft, the application comprises the following steps: step one, according to the gas input-output relationship between two cushion fans and four air chambers, six nonlinear equations are listed; step two, linearization is carried out at the balance point of the fan characteristic curve of the hovercraft; step three, the air passage characteristic curve of the hovercraft is smoothed, and the air passage curve is obtained; step four, the full-cushion hovercraft cushion pressure model is simplified at the balance position to obtain an initial cushion height; step five, an initial solution dynamic tracking method is adopted for iterative solution; and step six, the above steps are repeated to solve the cushion pressure until the equation set residual is smaller than a specified value. The application is used for underwater operation.

Description

TECHNICAL FIELD

[0001] The present application relates to a cushion pressure calculation method, in particular to a cushion pressure calculation method for full-cushion hovercraft, and belongs to the technical field of full-cushion hovercraft dynamics modeling. BACKGROUND

[0002] The full-cushion hovercraft forms a layer of air cushion between the hull and the running surface through the cushion system, effectively reducing the frictional resistance, thereby improving the speed and fuel efficiency of the ship. At the same time, the existence of the cushion system also enables the hovercraft to travel on various terrains (such as water surface, marsh, ice surface, snow, etc.), thereby greatly expanding its application range, especially in rescue and military tasks. The dynamics model research of the hovercraft cushion system is a basic work of the entire hovercraft dynamics and kinematics model research. Through in-depth research on the cushion system, the motion characteristics of the hovercraft can be better understood, thereby optimizing the design and improving the control performance and safety. However, the cushion system of the hovercraft has strong nonlinearity and non-analyticity, it involves multi-degree-of-freedom nonlinear dynamics, the interaction between the hull, skirt, air cushion and water surface is very complex, and these coupling effects increase the complexity of the model. This complex relationship makes it very difficult to calculate the cushion pressure, and more accurate numerical methods are needed to solve it.

[0003] At present, the research on the dynamics model of the hovercraft cushion system not only has important theoretical value, but also has significant practical significance. If accurate dynamics modeling is performed, the motion performance of the hovercraft under different working conditions can be predicted, and scientific basis can be provided for optimal design and safe operation. In addition, model research can also be used for the development of advanced control systems to improve the stability and reliability of the hovercraft and reduce the accident rate. Therefore, the research on the cushion pressure calculation method is of great significance.

[0004] However, due to the involvement of complex fluid mechanics and aerodynamics in the existing dynamics model, it has high nonlinearity, which leads to the inability to stably and accurately solve the cushion pressure values at different times, and thus cannot predict and avoid accidents caused by uneven or out-of-control air cushion pressure, which is not conducive to the safe navigation of the hovercraft. SUMMARY

[0005] The purpose of the present application is to solve the problem that the existing dynamics model of the hovercraft cushion system cannot stably and accurately solve the cushion pressure values at different times, and thus cannot predict and avoid accidents caused by uneven or out-of-control air cushion pressure, which is not conducive to the safe navigation of the hovercraft. A cushion pressure calculation method for full-cushion hovercraft is provided.

[0006] The technical scheme of the present application is: a cushion pressure calculation method for full-cushion hovercraft includes the following steps:

[0007] Step one: list six nonlinear equations according to the relationship between two air cushion fans and four air chambers;

[0008] Step two: linearize at the balance point of the air cushion fan characteristic curve;

[0009] Step three: smooth the air cushion fan characteristic curve and obtain the air passage curve;

[0010] Step four: simplify the cushion pressure model of the full-cushion air cushion craft at the balance position to obtain the initial cushion height;

[0011] Step five: use the initial solution dynamic tracking method for iterative solution;

[0012] Step six: repeat the above steps to solve the cushion pressure until the equation set residual is less than the specified value.

[0013] Further, the six nonlinear equations in step one are:

[0014]

[0015] where P i (i=1-6) is the internal air pressure of the four air chambers plus two air cushion fans, Q PUMPi (i=1-4) is the volume change rate of the four air chambers, and f represents the nonlinear relationship between the air chambers and the air cushion fan.

[0016] Further, the balance point in step two is: the cushion pressure of the full-cushion air cushion craft when the air cushion vertical and the ship body gravity are balanced, and the air cushion fan speed commonly used.

[0017] Further, the linearized fan characteristic curve in step two is:

[0018]

[0019] where P0 is the cushion pressure balanced with the ship body gravity, and n0 is the air cushion fan speed commonly used.

[0020] Further, the air passage curve between the air cushion fan and its adjacent air chamber after smoothing in step three is:

[0021]

[0022] where Q INCi represents the air flow into each air chamber from the air cushion fan, P INCi represents the air pressure into each air chamber from the air cushion fan, and i=1-4 represents the four air chambers.

[0023] Further, the process of simplifying the full hovercraft cushion pressure model at the equilibrium position in step four to obtain the initial cushion height is:

[0024] Step four one: linearization of the full hovercraft skirt flow model at the equilibrium point, after removing the constant term of the full hovercraft skirt flow function, the function is written as:

[0025]

[0026] Step four two: simplifying the cushion system equation set, in the equilibrium state, the four air chambers of the full hovercraft will no longer flow to each other; eliminate f 01 and f 02 terms, and due to the symmetry in the equilibrium state, the left and right sides of the full hovercraft cushion fan have equal flow to the two air chambers connected to them, that is:

[0027]

[0028] At this time, the hovercraft cushion pressure equation set can be written as:

[0029]

[0030] Preferably, the iterative solution process in step five is as follows:

[0031] The P1-P6 solved at the last time step are used as the initial solution of the cushion pressure solution at the next time step, that is:

[0032] P 0i (t)=P i (t-Δt)

[0033] Where P 0i represents the initial solution of the full hovercraft cushion pressure solved by Newton iteration method, P i represents the actual cushion pressure solved, t is the current time and Δt is the simulation step length.

[0034] Compared with the prior art, the present application has the following effects:

[0035] The present application is directed to the full cushion air cushion vehicle cushion system, through improving the model and the traditional Newton iteration method, when using, the full cushion air cushion vehicle cushion pressure model is partially linearized, the model is smoothed, the simulation initial height is determined and the dynamic tracking processing is carried out to the algorithm initial solution, through the above improvement, a method which can stably and accurately solve the ship body cushion pressure of each simulation step is proposed. Among them, the partial linearization and smoothing processing of the model reduce the oscillation and divergence phenomenon in the iteration process, and significantly improve the calculation stability; and the dynamic tracking processing of the Newton iteration method further improves the calculation accuracy. These improvements ensure the reliability and accuracy of the air cushion vehicle cushion system in complex environment. Whether in still water or in complex wave environment, good solving performance can be maintained, and the air cushion vehicle cushion pressure solving demand under different operating conditions can be adapted. Accurate prediction and avoidance of accidents caused by uneven or out-of-control air cushion pressure ensure the safety performance of air cushion vehicle navigation.

[0036] The method of the present application provides a new tool and method for the research and application of air cushion vehicle cushion system, promotes the development of related technology, and has important academic and engineering value. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a four-chamber model schematic diagram of the present application;

[0038] Figure 2 is a fan characteristic surface graph of the present application;

[0039] Figure 3 is a comparison graph of air passage characteristic curve processing before and after the present application;

[0040] Figure 4 is a Newton iteration method flow chart of the present application; DETAILED DESCRIPTION

[0041] Specific implementation method one: combined with Figures 1 to 4 The present embodiment includes the following steps:

[0042] Step one: according to the gas input and output relationship of two cushion fans and four air chambers, six nonlinear equations are listed;

[0043] Step two: linearization is carried out at the equilibrium point of the air cushion vehicle fan characteristic curve;

[0044] Step three: the air cushion vehicle air passage characteristic curve is smoothed, and the air passage curve is obtained;

[0045] Step four: the full cushion air cushion vehicle cushion pressure model is simplified at the equilibrium position to obtain the initial cushion height;

[0046] Step five: the initial solution dynamic tracking method is used for iteration solution;

[0047] Step six: repeat the above steps to solve the cushion pressure until the equation set residual is less than the specified value.

[0048] Specific implementation two: combined Figures 1 to 4 To illustrate this embodiment, the six nonlinear equations in step one of this embodiment are:

[0049]

[0050] Where P i (i=1-6) is the internal air pressure of the four air chambers plus two cushion air fans, Q PUMPi (i=1-4) is the air chamber volume change rate of the four air chambers, and f represents the nonlinear relationship between each air chamber and the cushion air fan.

[0051] In this way, subsequent improvements and optimizations of the model and the traditional Newton iteration method are facilitated. The other components and connection relationships are the same as in specific implementation one.

[0052] Specific implementation three: combined Figures 1 to 4 To illustrate this embodiment, the equilibrium point in step two of this embodiment is: the cushion pressure when the hovercraft is in vertical equilibrium with the air cushion and the ship body gravity, and the commonly used cushion fan speed of the hovercraft.

[0053] In this way, the stability, energy consumption optimization, response speed, control accuracy, and adaptability of the system can be significantly enhanced, while the model calculation is simplified. The other components and connection relationships are the same as in specific implementation two.

[0054] Specific implementation four: combined Figures 1 to 4 To illustrate this embodiment, the linearized fan characteristic curve in step two of this embodiment is:

[0055]

[0056] Where P0 is the cushion pressure in equilibrium with the ship body gravity, and n0 is the commonly used cushion fan speed of the hovercraft.

[0057] In this way, the complexity of the cushion pressure solving equation set is reduced while the model authenticity is hardly affected, and the solving stability and accuracy of the Newton iteration method are increased. The other components and connection relationships are the same as in specific implementation three.

[0058] Specific implementation five: combined Figures 1 to 4 To illustrate this embodiment, the air duct curve between the cushion fan and its adjacent air chamber after smoothing in step three of this embodiment is:

[0059]

[0060] where Q INCi represents the gas flow rate into each plenum by the cushion fan, P INCi represents the gas pressure into each plenum by the cushion fan, i = 1-4 represents the four plenums.

[0061] In this way, the requirement of Newton iteration method for the smoothness of the equations to be solved can be met, and the non-smoothness of the function can seriously affect the feasibility of the algorithm for solving the equations. The other components and connection relationships are the same as any one of the first to fourth embodiments.

[0062] Embodiment six: in combination with Figures 1 to 4 To illustrate this embodiment, the process of simplifying the full-cushion hovercraft cushion pressure model at the equilibrium position to obtain the initial cushion height in step four of this embodiment is as follows:

[0063] Step four one: linearization of the full-cushion hovercraft skirt discharge model at the equilibrium point, after removing the constant term from the full-cushion hovercraft skirt discharge function, the function is written as:

[0064]

[0065] Step four two: simplifying the cushion system equation set, in the equilibrium state, the four plenums of the full-cushion hovercraft will no longer discharge to each other; eliminate f 01 and f 02 terms, and due to the symmetry in the equilibrium state, the flow rates of the left and right cushion fans to the two plenums connected thereto are equal, i.e.:

[0066]

[0067] At this time, the hovercraft cushion pressure equation set can be written as:

[0068]

[0069] In this way, the computational complexity of Newton iteration method at the equilibrium point is greatly reduced. The other components and connection relationships are the same as any one of the first to fifth embodiments.

[0070] Embodiment seven: in combination with Figures 1 to 4 To illustrate this embodiment, the iteration solving process in step five of this embodiment is as follows:

[0071] The successfully solved P1-P6 at the last time step are used as the initial solution for the cushion pressure solving at the next time step, i.e.:

[0072] P 0i (t) = P i (t-Δt)

[0073] where P 0i represents the calculated cushion pressure, t is the current time, and Δt is the simulation step size. i represents the calculated cushion pressure, t is the current time, and Δt is the simulation step size.

[0074] In this way, a more optimal initial solution is reasonably selected, and the success rate of solving is greatly improved. The other components and connection relationships are the same as any one of the first to sixth embodiments.

[0075] Embodiment:

[0076] The application provides a calculation method for the cushion pressure of a full-cushion air cushion vehicle. The following is a detailed description of the application by taking a full-cushion air cushion vehicle equipped with four air chambers and two air fans as an example.

[0077] The application first establishes an air cushion vehicle cushion system model, lists a six-element nonlinear equation set according to the gas input-output relationship between the two cushion fans and the four air chambers. Then, the model and the traditional Newton iteration method are improved, the cushion fan and air duct characteristic curves are smoothed, the initial solution dynamic tracking method is used to quickly solve the equation set, and the steps are repeated until the equation set residual is less than a specified value.

[0078] The following is a detailed description of the specific implementation steps of the application: Figure 1 , Figure 2 , Figure 3 , Figure 4

[0079] Step 1: Establish a cushion system model according to the cushion fan model, skirt discharge flow, air chamber discharge flow, and gas volume change rate, and list a six-element nonlinear equation set according to the gas input-output relationship between the two cushion fans and the four air chambers.

[0080]

[0081] where P i (i=1-6) is the internal air pressure of the four air chambers plus two cushion fans, Q PUMPi (i=1-4) is the volume change rate of the four air chambers, and f represents the nonlinear relationship between the air chambers and the cushion fan.

[0082] Step 2: Linearize at the equilibrium point of the air cushion vehicle fan characteristic curve. The fan characteristic curve can be written as a two-variable function with the cushion fan speed n and the cushion fan head P as independent variables and the fan flow Q as the dependent variable. The linearization equilibrium point is selected at the full-cushion air cushion vehicle commonly used cushion fan speed and the air cushion vehicle cushion pressure when the air cushion vertical pressure and the ship body gravity are balanced. The linearized fan characteristic curve is

[0083] ​

[0084] Where P0 is the hover pressure when the ship is in equilibrium with the gravity, n0 is the normal speed of the hover fan.

[0085] Step 3: Smooth the air passage characteristic curve of the hovercraft, the air passage curve between the hover fan and its adjacent air chamber after smoothing is:

[0086]

[0087] Where Q INCi represents the air flow rate from the hover fan into each air chamber, P INCi represents the air pressure from the hover fan into each air chamber, i = 1-4 represents the four air chambers.

[0088] Step 4: Simplify the hover pressure model of the full hover hovercraft at the equilibrium position to obtain the initial hover height;

[0089] (1) Linearize the skirt discharge model of the full hover hovercraft at the equilibrium point, and after removing the constant term from the skirt discharge function of the full hover hovercraft, the function can be written as:

[0090]

[0091] (2) Simplify the hover system equation set, at the equilibrium state, the four air chambers of the full hover hovercraft will no longer discharge to each other. The f 01 and f 02 terms can be eliminated, and due to the symmetry at the equilibrium state, the flow rates of the left and right hover fans of the full hover hovercraft to the two air chambers connected thereto are equal, i.e.:

[0092]

[0093] At this time, the hover pressure equation set of the hovercraft can be written as:

[0094]

[0095] Step 5: Use the initial solution dynamic tracking method to solve iteratively;

[0096] The P1-P6 solved successfully at the previous time step are used as the initial solution for solving the hover pressure at the next time step, i.e.:

[0097] P 0i (t) = P i (t-Δt)

[0098] Where P 0i represents the hover pressure of the full hover hovercraft, and P iP represents the calculated actual cushion pressure, t is the current time, and Δt is the simulation step length.

[0099] Step 6: Repeat the above steps to solve the cushion pressure until the equation set residual is less than a specified value.

[0100] According to the fourth step, the initial cushion height is selected as the initial solution, and the nonlinear functions corresponding to the equation set are linearized at the initial solution. The linearized equation set is solved. Although this step cannot usually obtain an analytical solution of the original equation set, it can approach the analytical solution direction. The solution in the previous step is used as a new initial value to start repeating until the equation set residual is less than a specified value.

[0101] The present application provides a calculation method for the cushion pressure of a full-cushion hovercraft. First, six nonlinear equation sets are derived according to the gas input and output relationships of two cushion fans and four air chambers. Then, the model and the traditional Newton iteration method are improved. By smoothing the cushion fan and air duct characteristic curves and using the initial solution dynamic tracking method, the cushion pressure values at different times can be accurately and smoothly obtained. This method improves the calculation accuracy, ensures that the cushion pressure results at each simulation step length are accurate and reliable, reduces the oscillation and divergence phenomena in the iteration process, and enhances the calculation stability. Whether in still water or in a complex wave environment, this method can adapt to the cushion pressure calculation requirements of hovercrafts under different operating conditions and maintain good calculation performance. It provides a new tool for the research and application of hovercraft cushion systems and promotes the development of related technologies, which has important academic and engineering value.

[0102] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of solving for the pressure of a full cushion air cushion vehicle cushion, characterized by: It includes the following steps: Step one: According to the relationship between the two cushion air-lift fan and four air chamber gas input and output, list six nonlinear equations; The six nonlinear equations are: wherein, is the internal air pressure of the four-chambered air chamber plus two air cushion fan, is the volume change rate of the four-chambered air chamber, represents the non-linear relationship between each air chamber and the air cushion fan. Step two: Linearization at the equilibrium point of the air-cushion fan characteristic curve; The fan characteristic curve is: wherein, is the lift pressure for balancing the weight of the hull, is the usual rotational speed of the air cushion vehicle's air fan. Step three: Smooth processing of the air-cushion air passage characteristic curve, and get the air passage curve; The air passage curve between the cushion air-lift fan and its adjacent air chamber after smoothing processing is: wherein, Gpresents the gas flow rate into each plenum by the plenum fan, Gpresents the gas pressure into each plenum by the plenum fan, Gpresents the four plenums; Step four: Simplify the full cushion air-cushion cushion pressure model at the equilibrium position to obtain the initial cushion height; Step four one: Linearization of the full cushion air-cushion skirt discharge model at the equilibrium point, after removing the constant term of the full cushion air-cushion skirt discharge function, the function is written as: Step four two: the cushion system equation group is simplified, in the equilibrium state, the four air chambers of the full-cushion air cushion vehicle will no longer leak each other; eliminate with The item, and because of the symmetry in the equilibrium state, the left and right sides of the full-cushion air cushion vehicle cushion fan equal to the flow of the two air chambers connected to it, that is: At this time, the air-cushion cushion pressure equation set can be written as: ； Step five: Iterative solution by using the initial solution dynamic tracking method; The iterative solution process is as follows: The solution of the previous time step is successful The initial solution for the solution of the next time step cushion pressure, namely: wherein represents the full hovercraft lift pressure solved using Newton iteration method with the initial solution set, represents the actual lift pressure solved, is the current time is the simulation step; Step six: Repeat the above steps to solve the cushion pressure until the equation set residual is less than the specified value.

2. The method of claim 1, wherein: The equilibrium point in step two is: the cushion pressure of the full cushion air-cushion when the air cushion vertical and the ship body gravity are in balance, and the air-cushion commonly used cushion air-lift fan speed.

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