Design method of ultra-large ship anti-pitching controller considering severe sea conditions

Abstract

The invention provides a design method of an ultra-large ship anti-pitching controller considering severe sea conditions, and the method comprises the steps: designing a simple robust controller through employing a first-order closed-loop gain shaping algorithm; a dual nonlinear feedback control algorithm is introduced, a control law is designed by using cosine and tangent functions, and the problem of large output energy of the controller is solved; and a positive feedback link is introduced to solve the problem of delay in instruction response of the controller. The controller designed by the invention combines a cosine and tangent function dual nonlinear positive feedback control algorithm and a simplified closed-loop gain forming algorithm, so that the problem of response delay of the controller caused by the characteristics of long time lag and large inertia of an ultra-large ship is effectively solved while the design difficulty of the controller is reduced; and the pitching amplitude and frequency of the ship are reduced. Meanwhile, in consideration of external interference of severe sea conditions on the controller, original error feedback is replaced by double nonlinear positive feedback, and an expected control effect is achieved on the premise of ensuring that the controller outputs less energy.

Description

Technical Field

[0001] The present invention relates to the technical field of application of automatic anti-pitch equipment for ultra-large ships, and in particular to a design method for an anti-pitch controller for ultra-large ships taking into account severe sea conditions. Background Art

[0002] With the continuous development of global trade and the extensive use of marine resources, the shipping industry has made significant progress and development in recent decades. When a ship is sailing on the sea, it is easily disturbed by external interference and produces pitch motion. Therefore, studying the problem of pitch reduction control of ships has become a difficult problem that needs to be solved urgently.

[0003] The pitch reduction controller designed using the closed-loop gain shaping algorithm is flexible and intuitive, so it is widely used. This technology directly uses four parameters with engineering significance to construct the closed-loop transfer system transfer function, and then infers the robust controller. The following is an introduction to this technology, taking the American PCH hydrofoil boat as the research object.

[0004] First, take the state vector as:

[0005]

[0006] In order to observe the anti-rolling effect more intuitively, let h be the heave displacement of the hydrofoil boat and θ be the pitch angle of the hydrofoil boat. Then the longitudinal motion state space mathematical model of the hydrofoil boat is:

[0007]

[0008] In the formula, the control vector U T = [FM], which are the external forces and moments for controlling the heave and pitch of the ship. Using the various parameters of the hydrofoil boat, the coefficient matrices in the ship model can be obtained as follows:

[0009]

[0010]

[0011] If the output is h and θ, the transfer function mathematical model G is:

[0012]

[0013] Then, the closed-loop transfer function is constructed using these four parameters, and the robust controller is derived from it. K :

[0014]

[0015] At present, the research on ship pitch reduction is mainly focused on merchant ships and hydrofoil boats. Due to the large inertia, long time delay and strong coupling of ultra-large ships, the difficulty of controller design also increases. When ultra-large ships sail in severe sea conditions, they are more unstable due to external interference, so the research on intelligent technology for ultra-large ships is imminent.

[0016] Based on the above analysis, the traditional pitch reduction control technology has the following two defects:

[0017] 1) The existing algorithms are no longer suitable for the large inertia and long time delay of ultra-large ships. The mass and inertia of ultra-large ships will cause a long delay in the system's response to control commands. At the same time, the control commands generated by the algorithm cannot accurately match the scale and dynamic characteristics of ultra-large ships, resulting in poor control effects;

[0018] 2) The existing algorithm has the problem of excessive output energy under severe sea conditions, resulting in poor ship pitch reduction effect, which in turn affects the stability and safety of the entire control system. Summary of the invention

[0019] According to the above technical problems that the pitch reduction controller design coefficient is high and the pitch reduction effect is poor when the super-large ship is sailing in severe sea conditions, a design method for the super-large ship pitch reduction controller considering severe sea conditions is provided. The present invention is designed based on a first-order closed-loop gain shaping algorithm, which reduces the difficulty of controller design; and adopts a dual nonlinear positive feedback control algorithm to improve the control effect, ensuring that the energy output of the controller is reduced while achieving pitch reduction.

[0020] The technical means adopted by the present invention are as follows:

[0021] A design method for a super-large ship pitch reduction controller considering severe sea conditions includes:

[0022] S1. Design a simple and robust controller using a first-order closed-loop gain shaping algorithm;

[0023] S2, introduce the dual nonlinear feedback control algorithm, use the cosine and tangent functions to design a control law for a simple robust controller to solve the problem of large controller output energy;

[0024] S3. Introduce positive feedback to solve the problem of delay in controller response to instructions.

[0025] Furthermore, step S1 specifically includes:

[0026] S11, set u to represent the controller output signal, and y to represent the system output value;

[0027] S12. Since a ship will produce pitch and heave motion under the action of waves during actual navigation, white noise is used to simulate the wave interference input r;

[0028] S13. When designing the controller K, set the diagonal elements of the controller to 0 and simplify the controller as follows:

[0029]

[0030] Where C represents the design parameters of the controller; D represents the design parameters of the controller; A, B are the steady-state output values ​​G′ of the generalized controlled object after being excited by the unit step signal; T 11 , T 22 All represent controller parameters; s represents the Laplace operator;

[0031] S14, a closed-loop transfer function is formed by a simple integral link and the steady-state output value G′ after the unstable system is formed, as follows:

[0032]

[0033] Among them, K represents the controller; P represents the generalized controlled object;

[0034] S15. Simplify the closed-loop transfer function to obtain:

[0035]

[0036] The above formula is the mathematical expression of the first-order closed-loop gain shaping algorithm.

[0037] Further, step S2 specifically includes:

[0038] S21. Use cosine and tangent functions to design a control law u for a simple robust controller as follows:

[0039] u=f(e)·g(e)

[0040] Among them, g(e) represents the nonlinear function of the feedback error e, which ensures that the controller can obtain slightly better control results while outputting less energy; f(e) represents the control law in the original control system;

[0041] S22, introduce a double nonlinear function as follows:

[0042] g(e)=f(u)1·f(u′)2=cos(a·e)·tan(b·e′)

[0043] In the above formula, a=0.1, b=0.25.

[0044] Furthermore, step S3 specifically includes:

[0045] S31. The transfer function of the negative feedback closed-loop system is expressed as:

[0046] K′G / (1+K′G)

[0047] Among them, K′ represents the control algorithm after adding nonlinear feedback;

[0048] S32. The transfer function of the positive feedback closed-loop system is expressed as:

[0049]

[0050] Among them, positive feedback is to change the feedback signal in the loop from negative feedback to positive feedback, multiply the original negative feedback controller by -1 to become a positive feedback controller, that is, -K′, and finally multiply the system as a whole by -1.

[0051] Compared with the prior art, the present invention has the following advantages:

[0052] 1. The present invention provides a design method for a super-large ship pitch reduction controller considering severe sea conditions, and designs a pitch reduction controller suitable for super-large ships in severe sea conditions. The controller combines the cosine and tangent function dual nonlinear positive feedback control algorithm with a simplified closed-loop gain shaping algorithm, which effectively solves the problem of controller response delay caused by the long time lag and large inertia of super-large ships while reducing the difficulty of controller design, and further reduces the amplitude and frequency of the ship's pitch.

[0053] 2. The present invention provides a design method for a super-large ship pitch reduction controller considering severe sea conditions. Considering that the controller may be disturbed by the severe sea conditions, the double nonlinear positive feedback is used to replace the original error feedback to ensure that the controller achieves the expected control effect under the premise of low output energy, so that it can be better applied to practical engineering. It provides technical support for super-large ships at home and abroad to sail in severe sea conditions, and at the same time promotes the development of super-large ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0055] Figure 1 The figure is a flow chart of the method of the present invention.

[0056] Figure 2The framework diagram of the simple and robust controller design of the present invention is shown.

[0057] Figure 3 This is a structural diagram of the dual nonlinear positive feedback control of the present invention.

[0058] Figure 4 Linear feedback of 7 levels of sea conditions provided by the embodiment of the present invention.

[0059] Figure 5 The embodiment of the present invention provides dual nonlinear feedback for 7 levels of sea conditions.

[0060] Figure 6 Linear feedback of 8 levels of sea conditions provided by the embodiment of the present invention.

[0061] Figure 7 The embodiment of the present invention provides dual nonlinear feedback for 8 levels of sea conditions. DETAILED DESCRIPTION

[0062] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0063] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0064] like Figure 1 As shown, the present invention provides a design method for a super-large ship pitch reduction controller considering severe sea conditions, comprising:

[0065] S1. Design a simple and robust controller using a first-order closed-loop gain shaping algorithm;

[0066] S2, introduce the dual nonlinear feedback control algorithm, use the cosine and tangent functions to design a control law for a simple robust controller to solve the problem of large controller output energy;

[0067] S3. Introduce positive feedback to solve the problem of delay in controller response to instructions.

[0068] In specific implementation, as a preferred embodiment of the present invention, step S1 specifically includes:

[0069] S11, set u to represent the controller output signal, and y to represent the system output value;

[0070] S12. Since a ship will produce pitch and heave motion under the action of waves during actual navigation, white noise is used to simulate the wave interference input r;

[0071] S13. When designing the controller K, set the diagonal elements of the controller to 0 and simplify the controller as follows:

[0072]

[0073] Where C represents the design parameters of the controller; D represents the design parameters of the controller; A, B are the steady-state output values ​​G′ of the generalized controlled object after being excited by the unit step signal; T 11 , T 22 All represent controller parameters; s represents the Laplace operator;

[0074] S14, a closed-loop transfer function is formed by a simple integral link and the steady-state output value G′ after the unstable system is formed, as follows:

[0075]

[0076] Among them, K represents the controller; P represents the generalized controlled object;

[0077] S15. Simplify the closed-loop transfer function to obtain:

[0078]

[0079] The above formula is a mathematical expression of a first-order closed-loop gain shaping algorithm, which is a simple robust control technology that can reduce the complexity of robust controller design.

[0080] In specific implementation, as a preferred embodiment of the present invention, step S2 specifically includes:

[0081] S21. Use cosine and tangent functions to design a control law u for a simple robust controller as follows:

[0082] u=f(e)·g(e)

[0083] Among them, g(e) represents the nonlinear function of the feedback error e, which ensures that the controller can obtain slightly better control results while outputting less energy; f(e) represents the control law in the original control system;

[0084] S22, introduce a double nonlinear function as follows:

[0085] g(e)=f(u)1·f(u′)2=cos(a·e)·tan(b·e′)

[0086] In the above formula, a=0.1, b=0.25.

[0087] In specific implementation, as a preferred embodiment of the present invention, step S3 specifically includes:

[0088] S31. The transfer function of the negative feedback closed-loop system is expressed as:

[0089] K′G / (1+K′G)

[0090] Among them, K′ represents the control algorithm after adding nonlinear feedback;

[0091] S32. The transfer function of the positive feedback closed-loop system is expressed as:

[0092]

[0093] Among them, positive feedback is to change the feedback signal in the loop from negative feedback to positive feedback, multiply the original negative feedback controller by -1 to become a positive feedback controller, that is, -K′, and finally multiply the system as a whole by -1.

[0094] Example

[0095] The present invention takes the super large "KVLCC2" oil tanker as the object to establish the mathematical model of ship pitch motion. Table 1 shows the relevant parameters of the oil tanker.

[0096] Table 1 Basic parameters of KVLCC2 tanker

[0097]

[0098]

[0099] When a ship is sailing on the sea, waves are the main cause of the ship's pitching motion. Therefore, when verifying the present invention, external interference modeling is first performed, and the second-order transfer function driven by white noise is used to simulate the wave interference. The principle is that the ITTC single-parameter spectrum is linearly approximated as y(s)=h(s)·ω(s), ω(s) represents a zero-mean Gaussian white noise process, and the power spectrum is 1.0. h(s) represents the second-order wave transfer function, as shown in the following formula.

[0100]

[0101] In the formula, is a constant representing the wave strength; ξ represents the damping coefficient; ω n =4.85 / T ω Indicates the wave frequency; T ω Represents the wave period.

[0102] The present invention will be verified under sea conditions of level 7 and level 8, and the second-order wave transfer function corresponding to each wind condition is calculated according to the second-order wave transfer function, as shown in Table 2 below.

[0103] Table 2 Second-order wave transfer functions under different wind force levels

[0104]

[0105] The simulation experiment was carried out using Simulink simulation software, and the time was set to 300s. It can be seen from the experimental result graph that the present invention reduces the heave displacement output value to 0.087m and the pitch angle output value to 0.058° under sea condition level 7, which is 44% and 40% higher than that of linear feedback heave displacement and pitch angle, respectively. Figure 6 and Figure 7 It can be seen that the present invention greatly reduces the pitch angle and frequency of the ship model under sea condition level 8 compared with linear feedback, making the ship sail more safely and smoothly under sea condition level 8.

[0106] Table 3 Performance parameters under changing sea conditions

[0107]

[0108] From the above results, it can be seen that the controller designed by the method of the present invention combines the cosine and tangent function dual nonlinear positive feedback control algorithm with the simplified closed-loop gain shaping algorithm, which effectively solves the problem of controller response delay caused by the long time lag and large inertia characteristics of super-large ships while reducing the difficulty of controller design, and further reduces the amplitude and frequency of ship pitching. At the same time, the present invention takes into account that the controller will be disturbed by the harsh sea conditions, and uses dual nonlinear positive feedback instead of the original error feedback to ensure that the controller achieves the expected control effect under the premise of low output energy.

[0109] 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for a super-large ship pitch reduction controller considering severe sea conditions, characterized in that: include: S1. Design a simple and robust controller using a first-order closed-loop gain shaping algorithm; S2, introduce the dual nonlinear feedback control algorithm, use the cosine and tangent functions to design a control law for a simple robust controller to solve the problem of large controller output energy; S3. Introduce positive feedback to solve the problem of delay in controller response to instructions.

2. The design method of a super-large ship pitch reduction controller considering severe sea conditions according to claim 1 is characterized in that: Step S1 specifically includes: S11, set u to represent the controller output signal, and y to represent the system output value; S12. Since a ship will produce pitch and heave motion under the action of waves during actual navigation, white noise is used to simulate the wave interference input r; S13. When designing the controller K, set the diagonal elements of the controller to 0 and simplify the controller as follows: Where C represents the design parameters of the controller; D represents the design parameters of the controller; A, B are the steady-state output values ​​G′ of the generalized controlled object after being excited by the unit step signal; T 11 , T 22 All represent controller parameters; s represents the Laplace operator; S14, a closed-loop transfer function is formed by a simple integral link and the steady-state output value G′ after the unstable system is formed, as follows: Among them, K represents the controller; P represents the generalized controlled object; S15. Simplify the closed-loop transfer function to obtain: The above formula is the mathematical expression of the first-order closed-loop gain shaping algorithm.

3. The design method of a super-large ship pitch reduction controller considering severe sea conditions according to claim 1 is characterized in that: Step S2 specifically includes: S21. Use cosine and tangent functions to design a control law u for a simple robust controller as follows: u=f(e)·g(e) Among them, g(e) represents the nonlinear function of the feedback error e, which ensures that the controller can obtain slightly better control results while outputting less energy; f(e) represents the control law in the original control system; S22, introduce a double nonlinear function as follows: g(e)=f(u)1·f(u′)2=cos(a·e)·tan(b·e′) In the above formula, a=0.1, b=0.

25.

4. The design method of a super-large ship pitch reduction controller considering severe sea conditions according to claim 1 is characterized in that: Step S3 specifically includes: S31. The transfer function of the negative feedback closed-loop system is expressed as: K′G / (1+K′G) Among them, K′ represents the control algorithm after adding nonlinear feedback; S32. The transfer function of the positive feedback closed-loop system is expressed as: Among them, positive feedback is to change the feedback signal in the loop from negative feedback to positive feedback, multiply the original negative feedback controller by -1 to become a positive feedback controller, that is, -K′, and finally multiply the system as a whole by -1.

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