Dynamical modeling method of new fatigue loading device considering wind turbine blade action

Abstract

The application provides a new fatigue loading device dynamics modeling method considering the action of a wind power blade, and aims to solve the problem of insufficient modeling accuracy caused by ignoring the coupling action of a large flexible wind power blade and a loading device in the prior art. The new fatigue loading device is based on a 2-DOF 5R parallel robot, and a dynamics model is constructed by using the Lagrange method, and the specific steps include: analyzing the stress condition of the new fatigue loading device, selecting generalized coordinates; calculating the kinetic energy, potential energy and dissipation energy of the system, deducing the generalized force corresponding to the generalized coordinates, substituting the energy parameters and the generalized force into the Lagrange equation, and simplifying to obtain the dynamics model. The model includes the mass, stiffness and damping parameters of the blade, can accurately reflect the dynamic behavior of the new fatigue loading device under actual fatigue test working conditions, can be used for evaluating the performance of the loading system, can provide a basis for device structure optimization and control strategy design, and is suitable for the field of large flexible wind power blade fatigue testing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dynamic modeling, in particular to a dynamic modeling method of a new fatigue loading device considering the action of a wind turbine blade, and more particularly to a modeling method of a wind turbine blade new fatigue loading device based on a 2-DOF 5R parallel robot under the consideration of the coupling action between the blade and the loading device, which is suitable for the field of fatigue performance testing of large flexible wind turbine blades. BACKGROUND

[0002] As one of the core mechanical structures in a wind turbine generator, a wind turbine blade mainly bears aerodynamic load, wind wheel rotation centrifugal force load, blade gravity load, etc., and is subjected to fatigue damage due to the influence of complex loads. Therefore, in order to evaluate the working efficiency and service life of the blade under actual working conditions, it is necessary to strictly test the fatigue performance thereof.

[0003] However, with the development of large-scale wind turbine blades, the length of the blades is increased and the flexibility of the blades is enhanced, so that the traditional fatigue loading device (vibration exciter loading) is difficult to excite vibration, and forcibly vibrating the blade will cause the weight of the vibration exciter to be greatly increased, which in turn will have a more serious impact on the blade structure in the test.

[0004] In view of the above problems, a new fatigue loading device based on a 2-DOF 5R parallel robot is proposed in the industry, which is more suitable for the loading requirements of large-scale blades in structure. However, due to the characteristics of large-scale and flexibility of the blades, the mass, stiffness, damping and other properties of the blades will have a non-negligible influence on the dynamic behavior of the loading device, that is, there is a significant coupling action between the blade and the loading device. In the prior art, when establishing the dynamic model of the new fatigue loading device, the coupling action is often not fully considered, so that the model cannot accurately reflect the stress and motion state of the loading device under actual test conditions, the modeling precision is insufficient, and the accuracy of the performance evaluation of the loading system is affected, which makes it difficult to ensure the reliability of the fatigue test results.

[0005] Therefore, there is an urgent need for a new fatigue loading device dynamic modeling method that can consider the influence of the blade and accurately reflect the coupling action between the blade and the new loading device, in order to solve the problem of insufficient modeling precision in the prior art. SUMMARY

[0006] The present application aims to provide a new fatigue loading device dynamic modeling method considering the action of a wind turbine blade, which introduces the coupling action between the wind turbine blade and the new fatigue loading device in the modeling process, establishes a high-precision dynamic model based on the Lagrange method, solves the problem of insufficient modeling precision caused by neglecting the coupling action of the blade in the prior art, and provides reliable model support for the performance evaluation and optimization of the new fatigue loading device.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0008] A novel fatigue loading device dynamics modeling method considering the action of wind turbine blades is a coupled system composed of a large wind turbine blade and a novel fatigue loading device based on a 2-DOF 5R parallel robot as the research object of dynamics modeling, a dynamics model is established based on the Lagrange method, and specifically includes the following steps:

[0009] S1: analyze the stress condition of the novel fatigue loading device in the loading process;

[0010] S2: select appropriate generalized coordinates to represent the motion state of the system;

[0011] S3: calculate the kinetic energy of the system, and express the kinetic energy as a function of generalized coordinates and generalized velocities;

[0012] S4: calculate the potential energy of the system, and express the potential energy as a function of generalized coordinates;

[0013] S5: calculate the dissipation energy of the system, which is represented by the damping force in the system;

[0014] S6: calculate the generalized force corresponding to the generalized coordinate;

[0015] S7: substitute the calculated kinetic energy, potential energy, dissipation energy and generalized force into the Lagrange equation, and arrange and simplify the obtained equation to obtain the dynamics model of the novel fatigue loading device considering the action of the blade.

[0016] Further, in step S1, the novel fatigue loading device is composed of two active links AB and ED with a length of L1, two passive links BC and CD with a length of L2, a fixed link AE with a length of L0, and five rotary joints A, B, C, D and E, wherein A and E are active joints, B, D and C are passive joints, two active joints A and E are connected with input actuators respectively, and the angles formed by active links AB and ED with the horizontal plane are and Passive joint B connects active link AB and passive link BC, passive joint D connects active link ED and passive link CD, rotary joint C is connected with the end effector; passive links BC and CD form angles with the horizontal axis, respectively and The end effector is connected with the wind turbine blade through a clamp, and point C is the output connected with the clamp.

[0017] Further, in step S2, the angular displacement of active joints A and E is selected as the generalized coordinate to represent the motion state of the system, and the expression is: , q1 is the generalized coordinate of active joint A, and q2 is the generalized coordinate of active joint E.

[0018] Furthermore, in step S3, the formula for calculating the system's kinetic energy is:

[0019] ;

[0020] ;

[0021] ;

[0022] Where E is the total kinetic energy of the system. E l E is the total kinetic energy of the four moving links. i Let m be the kinetic energy of the moving link i. i For the mass of moving member i, I i Let i be the moment of inertia of the moving link i. Let be the velocity of the center of mass of the moving link i in the x-direction. Let be the velocity of the center of mass of the moving link i in the y-direction. (k=a1, a2, p1, p2) represent the rotational angular velocities at joints A, E, B, and D, respectively. g For the kinetic energy of the end effector, v is the mass of the blade acting on the end effector of the mechanism. x v y These represent the velocities of the blade in the x and y directions, respectively.

[0023] Furthermore, in step S4, the formula for calculating the system's potential energy V is:

[0024] Where m1, m2, m3, and m4 are the masses of the active link AB, passive link BC, passive link CD, and active link ED, respectively; g is the acceleration due to gravity; s1, s2, s3, and s4 are the positions of the centers of mass of the active link AB, passive link BC, passive link CD, and active link ED, respectively; and L1 is the length of the active link AB. and These are the stiffness coefficients of the blade in the x and y directions. and represents the initial position of the end effector in the x and y directions, where x and y represent the real-time positions of the end effector in the x and y directions, respectively.

[0025] Furthermore, in step S5, the formula for calculating the system's dissipated energy is:

[0026] ;

[0027] ;

[0028] ;

[0029] wherein, and are damping coefficients of the blade in x and y directions, D x , D y are dissipation energies of the blade in x and y directions, D g is total dissipation energy of the blade, v x , v y are velocities of the blade in x and y directions.

[0030] Further, in step S6, the calculation formula of the generalized force of the system is:

[0031] ; wherein, F is a vector of the generalized force, and respectively represent input torques of the active link AB and the active link ED, T is a transpose.

[0032] Further, in step S7, the calculation formula of the Lagrange equation of the system is:

[0033] ; wherein, t is a loading time, represents a vector of the generalized coordinate, T is a transpose, and F is a vector of the generalized force;

[0034] The kinetic energy E, the potential energy V, the dissipation energy Dg and the generalized force F of the system are substituted to obtain:

[0035] ; ;

[0036] ;

[0037] ;

[0038] wherein,

[0039] , ,

[0040] wherein,

[0041] , ,

[0042] wherein, t is a loading time, M l is an inertia matrix, C l is a damping matrix, Mg is a generalized mass matrix, C g is a generalized damping matrix, is the equivalent moment of inertia of the active link AB, passive link BC and passive link CD, is the equivalent moment of inertia of the passive link BC and passive link CD, is the equivalent moment of inertia of the active link ED, passive link BC and passive link CD, N1 is the coefficient of kinetic energy term related to θ a1 , N2 is the coefficient of kinetic energy term related to θ a1 and θa2, N3 is the coefficient of kinetic energy term related to θ a2 , C1 is the coefficient of potential energy term related to θ a1 , C2 is the coefficient of potential energy term related to θ a1 and θ a2 , C3 is the coefficient of potential energy term related to θ a2 ;

[0043] By transformation, replacement and simplification, the dynamics equation of the novel fatigue loading device is:

[0044] ; in the formula, , is a symmetric positive definite inertia matrix; , is a centrifugal force and Coriolis force matrix, is a gravity matrix.

[0045] Further, it further includes the step of establishing a dynamics model based on the established dynamics model, and the simulation content includes the waving direction loading of the novel fatigue loading device.

[0046] Compared with the prior art, the beneficial technical effects of the present application are:

[0047] (1) In the process of dynamics modeling, the influence of the mass, stiffness, damping and other properties of the large wind turbine blade on the dynamic behavior of the loading device is fully considered, the coupling effect of the blade and the loading device is taken into account in the model, and the problem of insufficient modeling accuracy caused by ignoring the coupling effect in the prior art is solved, which can more truly reflect the actual fatigue test working condition;

[0048] (2) The dynamics model established by the present application contains the key parameters of the blade, which can be directly used to evaluate the stress and motion state of the loading system in actual test, and to judge whether the loading system meets the fatigue test performance requirements of different specifications of large blades, providing reliable basis for the structure optimization and control strategy design of the loading device;

[0049] (3) The model is constructed based on the Lagrange method, can be popularized and applied to dynamic modeling of other similar parallel robot loading devices, and is especially suitable for scenarios where flexible loads (such as large blades and long rod components) are coupled. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 A loading schematic diagram of the novel fatigue loading device in the application.

[0051] Figure 2 A diagram of the novel fatigue loading device in the application considering the influence of blade action.

[0052] Figure 3 A device end trajectory diagram when the novel fatigue loading device in the application loads in the flapwise direction.

[0053] Figure 4 A two-active-joint angular displacement diagram when the novel fatigue loading device in the application realizes a flapwise direction loading trajectory.

[0054] Figure 5 A two-active-joint driving torque diagram when the novel fatigue loading device in the application loads in the flapwise direction.

[0055] Figure 6 A two-active-joint driving power diagram when the novel fatigue loading device in the application loads in the flapwise direction. DETAILED DESCRIPTION

[0056] The application will be described in detail below with reference to the accompanying drawings.

[0057] A novel fatigue loading device dynamics modeling method considering wind power blade action, which takes a coupled system composed of a large wind power blade and a novel fatigue loading device as a research object of dynamics modeling, establishes a dynamics model based on the Lagrange method, and specifically includes the following steps:

[0058] S1: analyzing the stress condition of the novel fatigue loading device in the loading process;

[0059] S2: selecting appropriate generalized coordinates for representing the motion state of the system;

[0060] S3: calculating the kinetic energy of the system and representing the kinetic energy as a function form of generalized coordinates and generalized velocities;

[0061] S4: calculating the potential energy of the system and representing the potential energy as a function form of generalized coordinates;

[0062] S5: calculating the dissipation energy of the system, which is represented by the damping force in the system;

[0063] S6: calculating the generalized force corresponding to the generalized coordinates;

[0064] S7: Substitute the calculated kinetic energy, potential energy, dissipated energy and generalized force into the Lagrange equation, arrange and simplify the resulting equation to obtain the dynamics model of the new fatigue loading device considering the action of the blade.

[0065] As shown in Figure 1 , the new fatigue loading device in this embodiment is a wind turbine blade fatigue loading device based on a 2-DOF 5R parallel robot. The loading device is connected to the blade through a clamp.

[0066] As shown in Figure 2 , the new fatigue loading device in this embodiment is composed of two active links AB and ED with length L1, two passive links BC and CD with length L2, a fixed link AE with length L0, and five rotary joints A, B, C, D, and E. Among them, A and E are active joints, B, D, and C are passive joints. Among the five rotary joints, two active joints A and E are connected to the input actuators, and the active links AB and ED form angles of and with the horizontal plane, respectively. Passive joint B connects active link AB and passive link BC, passive joint D connects active link ED and passive link CD, and rotary joint C is connected to the end effector. Passive links BC and CD form angles of and with the horizontal axis, respectively, which are called passive joint angles. The end effector is connected to the wind turbine blade through a clamp, and point C is the output connected to the clamp. The reference frame AXY is located at active joint A. Among the five links of the device, the external torques at active joints A and E are and , respectively. The mass center positions of active link AB, passive link BC, passive link CD, and active link ED are , , and . The wind turbine blade is simplified as a spring-mass-damper system at the end of the device, with an equivalent mass of , equivalent stiffness in x and y directions of the loading point of and , and a blade damping coefficient of and . The wind turbine blade is simplified as a spring-mass-damper system.

[0067] In this embodiment, the set parameters of the new fatigue loading device and the wind turbine blade are shown in Table 1 and Table 2.

[0068] Table 1 Set parameters of the new fatigue loading device

[0069]

[0070] Table 2. Set parameters of the blade

[0071]

[0072] In step S1, when the new fatigue loading device loads in the flapwise direction, the force transmission path is: input torque of the active joint → active link → passive link → end effector → wind turbine blade, and the blade generates a reaction force on the end effector. The force condition is: the active joints A and E need to provide driving torque to drive the active links AB and ED to rotate, and the passive joints B and D generate a reaction force to transmit motion and torque to the end effector; there is an interaction force between the end effector and the blade, including the elastic force and damping force of the blade, and at the same time, the gravity of the blade is transmitted to the end effector through the excitation point. This analysis provides a basis for understanding the dynamic behavior of the system and establishing an accurate dynamic model.

[0073] In step S2, the new fatigue loading device has 2 degrees of freedom, and the angular displacement of the active joints A and E is selected as the generalized coordinates to represent the motion state of the system, and the expression is: , q1 is the generalized coordinate of the active joint A, and q2 is the generalized coordinate of the active joint E; this coordinate set reflects the degree of freedom characteristics of the system and is the basis for establishing the Lagrange motion equation, which is of great significance for subsequent kinematics, dynamics modeling and solving.

[0074] In step S3, the kinetic energy of the system needs to consider the contribution of the new fatigue loading device itself (four movable links, end effector) and the blade, and the specific calculation process is as follows:

[0075] (1) Displacement analysis

[0076] The new fatigue loading device forms a closed pentagon in the plane, from which the relationship between the displacements of the links can be obtained, and thus the function expression of the displacements of the links with respect to the generalized coordinates and is obtained:

[0077] (1)

[0078] Taking the partial derivative of equation (1) with respect to , we get:

[0079] (2)

[0080] Solving the equation set shown in equation (2) gives:

[0081] (3)

[0082] (4)

[0083] Similarly, the partial derivative of (1) with respect to t is:

[0084] (5)

[0085] (6)

[0086] (2) Velocity analysis

[0087] The derivatives of and with respect to t are:

[0088] (7)

[0089] The expressions of and can be obtained by combining (5) and (6):

[0090] In the new fatigue loading device, all the links are homogeneous, so the mass center of each link is at the geometric center of the link. The mass center positions of the four moving links are:

[0091] (8)

[0092] (9)

[0093] (10)

[0094] (11)

[0095] where x1 and y1 are the mass center positions of the active link AB in the x-axis and y-axis directions, respectively, x2 and y2 are the mass center positions of the passive link BC in the x-axis and y-axis directions, respectively, x3 and y3 are the mass center positions of the passive link CD in the x-axis and y-axis directions, respectively, and x4 and y4 are the mass center positions of the active link ED in the x-axis and y-axis directions, respectively.

[0096] The derivatives of the above four equations with respect to t are:

[0097] (12)

[0098] (13)​​​​​​​

[0099] (14)

[0100] (15)

[0101] The moments of inertia of the four moving links are:

[0102] (16)

[0103] Among them, I i Let m be the moment of inertia of the moving link i. i For the mass of moving member i, L i Let i be the length of the movable member.

[0104] Since the new fatigue loading device needs to consider the effect of the blades, the velocity of the end effector is written as:

[0105] (17)

[0106] in, , These represent the velocities of the end effector in the x-axis and y-axis directions, respectively.

[0107] The kinetic energy of the four moving links is:

[0108] (18)

[0109] Among them, E l Let Ei be the total kinetic energy of the four moving links, Ei be the kinetic energy of moving link i, and mi be the mass of moving link i. Let be the velocity of the center of mass of the moving link i in the x-direction. Let be the velocity of the center of mass of the moving link i in the y-direction. (k=a1, a2, p1, p2) represents the rotational angular velocity at the rotary joints A, E, B, and D.

[0110] From equations (12) to (17), we can obtain the expressions for the kinetic energy of the four moving links. We can extract the coefficients of like terms in the expressions and define the equivalent moment of inertia. , and ,Right now:

[0111] (19)

[0112] (20)

[0113] (twenty one)

[0114] in, I1, I2, I3, I4 are the moment of inertia of the active link AB, passive link BC, passive link CD, active link ED, respectively, m1, m2, m3, m4 are the mass of the active link AB, passive link BC, passive link CD, active link ED, respectively, L1 is the length of the active link AB. I1, I2, I3, I4 are the moment of inertia of the active link AB, passive link BC, passive link CD, active link ED, respectively, m1, m2, m3, m4 are the mass of the active link AB, passive link BC, passive link CD, active link ED, respectively, L1 is the length of the active link AB. I1, I2, I3, I4 are the moment of inertia of the active link AB, passive link BC, passive link CD, active link ED, respectively, m1, m2, m3, m4 are the mass of the active link AB, passive link BC, passive link CD, active link ED, respectively, L1 is the length of the active link AB.

[0115] The total kinetic energy expression of the four moving links is:

[0116] (22)

[0117] When the blade acts on the new fatigue loading device, the kinetic energy of the end effector is:

[0118] (23)

[0119] wherein is the mass of the blade acting on the mechanism end effector, E g is the kinetic energy of the end effector;

[0120] The expression of the kinetic energy of the end effector can be obtained from equation (18), the coefficients of the same type items in the expression are extracted, and , and are defined, that is:

[0121] (24)

[0122] (25)

[0123] (26)

[0124] wherein N1 is the coefficient of the kinetic energy term related to θ a1 , N2 is the coefficient of the interaction term related to θ a1 and θ a2 , and N3 is the coefficient of the kinetic energy term related to θ a2 .

[0125] The kinetic energy expression of the end effector is:

[0126] (27)

[0127] The total kinetic energy expression of the system is:

[0128] (28)

[0129] where E is the total kinetic energy of the system.

[0130] In step S4, the system potential energy is calculated as follows:

[0131] The potential energy of each movable link is:

[0132] (29)

[0133] where V is the total potential energy of the four movable links, V is the potential energy of movable link i, m is the mass of movable link i, g is the acceleration of gravity, y is the center of mass position of movable link i in the y-axis direction. l i i i

[0134] The potential energy expression of each movable link is respectively:

[0135] (30)

[0136] The potential energy of the end effector is:

[0137] (31)

[0138] where V1, V2, V3, V4 are the potential energies of the active link AB, passive link BC, passive link CD, and active link ED, respectively, V5 is the potential energy of the end effector, V6, V7 are the potential energies of the blade in the x and y directions, respectively, and are the stiffness coefficients of the blade in the x and y directions, and are the initial positions of the end effector.

[0139] The total potential energy expression of the system is:

[0140] (32)

[0141] In step 5, the system dissipation energy is calculated as follows:

[0142] The dissipation energy in the x direction is:

[0143] (33)

[0144] The dissipation energy in the y direction is:

[0145] (34)​​​​

[0146] The total dissipation energy of the system is:

[0147] (35)

[0148] where, and are the damping coefficients of the blade in the x and y directions, respectively, and D x , D y are the dissipation energies of the blade in the x and y directions, respectively, and D g is the total dissipation energy of the blade. v x 、v y are the velocities of the blade in the x and y directions, respectively.

[0149] Extracting like terms in the expression and defining , and , we have:

[0150] (36)

[0151] (37)

[0152] (38)

[0153] where C1 is the coefficient of the potential energy term related to θa1, C2 is the coefficient of the potential energy term related to the interaction term of θa1 and θa2, and C3 is the coefficient of the potential energy term related to θa2.

[0154] The dissipation energy expression of the system is:

[0155] (39)

[0156] In step S6, in addition to the potential force, the new fatigue loading device also receives the action of non-potential force and , and the generalized force is represented as:

[0157]

[0158] In step 7, the calculated kinetic energy, potential energy, dissipation energy, and generalized force are substituted into the Lagrange equation, and the dynamics equation of the system is:

[0159] (40)

[0160] where t is the loading time, represents the vector of generalized coordinates, is the vector of generalized forces corresponding to the generalized coordinates, and Tin and Tied represent the input torques of the master links AB and ED, respectively, and T is the transpose.

[0161] Instead of equations (18)-(39) to equation (40), we can obtain:

[0162] (41)

[0163] (42)

[0164] where,

[0165] ,

[0166] (43)

[0167] where,

[0168] ,

[0169] (44)

[0170] where t is the loading time, M l is the inertia matrix, C l is the damping matrix, M g is the generalized mass matrix, C g is the generalized damping matrix.

[0171] By transformation, substitution and simplification, the dynamics equation of the new fatigue loading device is:

[0172] (45)

[0173] where, , is a symmetric positive definite inertia matrix; , is a centrifugal and Coriolis force matrix, is a gravity matrix.

[0174] After the dynamics model is established, take the flapwise loading as an example to carry out dynamics simulation, Figure 3 is the end trajectory of the new fatigue loading device when loading in the flapwise direction, Figure 4 is the angular displacement of the master joints A and E of the new fatigue loading device when completing the trajectory. Figure 5 is the driving torque of the master joints A and E of the new fatigue loading device when loading in the flapwise direction, Figure 6The driving power of the active joints A and E, and the change of the driving moment and the driving power of the active joints with the vanes can be seen from the figure.

[0175] The above is an exemplary embodiment of the present application. It should be understood that the scope of protection of the present application is defined by the appended claims and their equivalents. It will be understood by those skilled in the art that the present application is not limited to the embodiments described above. The embodiments and the descriptions in the specification are only for the purpose of illustrating the principles of the present application, and various modifications or equivalent replacements made without departing from the spirit and essence of the present application should be considered as falling within the scope of protection of the present application. The scope of protection claimed by the present application is subject to the appended claims and their equivalent modifications.

Claims

1. A novel fatigue loading device dynamics modeling method considering the effect of wind turbine blades, characterized in that, The coupled system of a large wind turbine blade and a new fatigue loading device based on a 2-DOF 5R parallel robot is taken as the research object of the dynamic modeling, and a dynamic model is established based on the Lagrange method, specifically including the following steps: S1: analyzing the stress condition of the new fatigue loading device in the loading process; The novel fatigue loading device is composed of two active connecting rods AB and ED with a length of L1, two passive connecting rods BC and CD with a length of L2, a fixed connecting rod AE with a length of L0, and five rotary joints A, B, C, D and E, wherein A and E are active joints, B, D and C are passive joints, two active joints A and E are respectively connected with input actuators, and the angles formed by the active connecting rods AB and ED with the horizontal plane are and The passive joint B connects the active connecting rod AB and the passive connecting rod BC, the passive joint D connects the active connecting rod ED and the passive connecting rod CD, and the rotary joint C is connected with the end effector; the angles formed by the passive connecting rods BC and CD with the horizontal axis are and The end effector is connected with the wind power blade through a clamp, and the point C is the output connected with the clamp. S2: selecting generalized coordinates for representing the motion state of the system; The angular displacement of active joints A and E is selected as the generalized coordinates for representing the motion state of the system, and the expression is: , q1 is the generalized coordinate of active joint A, and q2 is the generalized coordinate of active joint E. S3: calculating the kinetic energy of the system and representing the kinetic energy as a function of the generalized coordinates and generalized velocities; the calculation formula of the kinetic energy of the system is: ； ； ； where E is the total kinetic energy of the system, El is the total kinetic energy of the four moving links, Ei is the kinetic energy of the moving link i, mi is the mass of the moving link i, Ii is the moment of inertia of the moving link i, is the center of mass velocity of the moving link i in the x direction, is the center of mass velocity of the moving link i in the y direction, (k = a1, a2, p1, p2) are the angular velocities of the rotational joints A, E, B, D, respectively, Eg is the kinetic energy of the end effector, is the mass of the blade acting on the end effector of the mechanism, vx, vy are the velocities of the blade in the x direction and the y direction, respectively; S4: calculating the potential energy of the system and representing the potential energy as a function of the generalized coordinates; the calculation formula of the potential energy V of the system is: ; wherein m1, m2, m3, m4 are the masses of the active link AB, passive link BC, passive link CD, and active link ED, respectively, g is the acceleration of gravity, s1, s2, s3, s4 are the center of mass positions of the active link AB, passive link BC, passive link CD, and active link ED, respectively, L1 is the length of the active link AB, and are the stiffness coefficients of the blade in the x and y directions, and are the initial positions of the end effector in the x and y directions, x, y are the real-time positions of the end effector in the x and y directions. S5: calculating the dissipation energy of the system by using the damping force in the system; the calculation formula of the dissipation energy of the system is: ； ； ； wherein, and are the damping coefficients in the x and y directions of the blade, Dx, Dy are the dissipation energies in the x and y directions of the blade, respectively, Dg is the total dissipation energy of the blade, vx, vy are the velocities in the x and y directions of the blade, respectively; S6: calculating the generalized force corresponding to the generalized coordinates; the calculation formula of the generalized force of the system is: ; where F is a vector of generalized forces, and T denote the input torque of the active link AB, ED, respectively, T is the transpose. S7: substituting the calculated kinetic energy, potential energy, dissipation energy and generalized force into the Lagrange equation, and arranging and simplifying the obtained equation to obtain the dynamic model of the new fatigue loading device considering the action of the blade; the calculation formula of the Lagrange equation of the system is: where t is the loading time, where x is the vector of generalized coordinates, T is the transpose, and F is the vector of generalized forces; substituting the kinetic energy E, potential energy V, dissipation energy Dg and generalized force F of the system to obtain: ； ； ； ； wherein, ， ， wherein, ， ， where t is the loading time, Ml is the inertia matrix, Cl is the damping matrix, Mg is the generalized mass matrix, Cg is the generalized damping matrix, Jl is the equivalent moment of inertia of the active link AB, passive link BC, and passive link CD, J2 is the equivalent moment of inertia of the passive link BC and passive link CD, J3 is the equivalent moment of inertia of the active link ED, passive link BC, and passive link CD, N1 is the coefficient of the kinetic energy term related to θal, N2 is the coefficient related to the interaction term of θal and θa2, N3 is the coefficient of the kinetic energy term related to θa2, C1 is the coefficient of the potential energy term related to θal, C2 is the coefficient of the potential energy term related to the interaction term of θal and θa2, C3 is the coefficient of the potential energy term related to θa2; by transformation, replacement and simplification, the dynamic equation of the new fatigue loading device is: ; where , is a symmetric positive definite matrix of inertia; , is a centrifugal and Coriolis force matrix, is a gravitational force matrix.

2. The method of claim 1, wherein the method is characterized by: and further including the step of performing dynamic simulation based on the established dynamic model, and the simulation content includes the waving direction loading of the new fatigue loading device.

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