Control method for centrifuge dynamic and static coupling integrated loading and supergravity load active compensation

Abstract

The application provides a control method for centrifuge dynamic and static coupling integrated loading and supergravity load active compensation, comprising the following steps: designing a load time curve according to engineering working condition design load and determining the loading position of the load; converting all loads outside all loading points into concentrated load time curves at the loading points and transforming into discrete time curves, and performing linear superposition to obtain a target load curve; then inputting a loading control program, starting a loading device, collecting loading pressure and loading point displacement data; adjusting the output load according to the load difference, so that the load difference converges to a preset error range; simultaneously calculating the displacement rate of the loading point to judge the motion state of the loading point; executing the pre-active load compensation according to the motion state of the loading point and the change of the motion direction of the loading point; and repeatedly executing the above steps to continuously execute the load active compensation, so that the coincidence degree of the test working condition and the engineering practice is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, specifically to a control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads. Background Technology

[0002] Centrifuge model testing, with its core advantage of reproducing the in-situ stress state and physical-mechanical evolution process of soil and rock under hypergravity, is one of the most reliable testing methods in geotechnical engineering. In centrifuge model tests involving complex conditions such as offshore wind power foundations, subway vibration, and adjacent underground structures, it is necessary to accurately apply various complex combinations of dynamic and static loads to the model within a confined model chamber to realistically reproduce the actual situation. Under the hypergravity environment of a centrifuge, the mechanical friction resistance inside the loading device amplifies with increasing hypergravity, creating additional hypergravity loads on the loading equipment. Since the loading equipment needs to overcome the hypergravity load to apply external loads, the actual loading pressure output according to the preset target load curve deviates significantly from the target load, directly causing data distortion and seriously affecting the accuracy and reliability of the test results.

[0003] Existing centrifuge loading control technology still suffers from the following intractable technical defects:

[0004] 1. Due to the limited space in the model box, most existing technologies can only install one loading device to meet the needs of complex working conditions and design loading schemes for single static or dynamic loads. They cannot simultaneously apply static loads such as constant equipment loads and building structure loads with dynamic environmental loads such as wind and wave loads and traffic loads. Therefore, they cannot accurately simulate the impact of the coupling effect of static and dynamic loads on the model, resulting in a large deviation between the test results and the actual engineering situation.

[0005] 2. Regarding the problem of hypergravity load caused by huge mechanical friction under hypergravity field, existing technologies mostly adopt materials and mechanical structures that minimize deformation, thereby reducing mechanical friction and passively weakening hypergravity load. However, they cannot actively adjust the operation of the equipment according to the real-time changes in the actual pressure and the direction and state of motion of the loading point of the test model during the loading process. Summary of the Invention

[0006] This invention is made to solve the above-mentioned problems, and aims to provide a control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads.

[0007] This invention provides a control method for integrated static and dynamic loading of centrifuges and active compensation of hypergravity loads, characterized by the following steps: Step S1, designing load time history curves and determining the loading locations based on the engineering conditions to be simulated; Step S2, converting all loads outside the loading points into equivalent concentrated load time history curves at the loading points; Step S3, converting the load time history curves into discretized time history curves, and linearly superimposing the discretized time history curves to obtain the target load curve; Step S4, during the centrifuge model test, inputting the target load curve into the loading control program, starting the loading device, and collecting real-time data on the loading pressure and displacement of the loading points; Step S5, adjusting the output load of the loading device based on the load difference between the loading pressure and the target load at the current moment, so that the load difference converges to a preset error range. The load difference is used as the load compensation value; Step S6: Simultaneously, the displacement rate of the loading point is calculated based on the displacement data of the loading point, and the motion state of the loading point is determined based on the displacement rate and the preset motion state threshold; Step S7: Based on the changes in the motion state and direction of the loading point, pre-active load compensation is performed; If neither the motion state nor the direction of the loading point changes, the target load curve and the load compensation value are superimposed and input into the loading control program; If the direction of the loading point changes but the motion state of the loading point does not change, the target load curve and the opposite of the load compensation value are superimposed and input into the loading control program; If the motion state of the loading point changes, the process returns to step S5; Step S8: Steps S5 to S7 are repeated, and the centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load are continuously completed according to the loading control program.

[0008] The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity load provided by the present invention may also have the following features: wherein the load includes dynamic load and static load, the dynamic load includes at least one of wind load, wave load, and traffic load; the static load includes at least one of structural self-weight load, equipment dead load, and pressure / push / pull load for bearing capacity testing.

[0009] The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity load provided by the present invention may also have the following features: in step S3, when converting the load time history curve into a discretized time history curve, for a simple harmonic vibration load, after generating the corresponding simple harmonic continuous time history curve based on the vibration frequency and amplitude, it is discretized at equal intervals.

[0010] The control method for centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load provided by the present invention may also have the following features: in step S3, when converting the load time history curve into a discretized time history curve, for random cyclic loads, the harmonic superposition method or random phase method is used to convert the power spectral density function in the frequency domain into a continuous random load time history curve in the time domain and then discretize it at equal intervals.

[0011] The control method for centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load provided by the present invention may also have the following feature: wherein, in step S5, the preset error range is 5% of the target load.

[0012] The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity load provided by the present invention may also have the following features: wherein the direction of motion includes positive and negative directions, and the motion state includes quasi-static and dynamic states.

[0013] The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity load provided by the present invention may also have the following features: wherein, in step S6, determining the motion state of the loading point based on the displacement rate and the preset motion state threshold specifically includes: comparing the displacement rate of the loading point with the preset motion state threshold; when the displacement rate of the loading point is less than the preset motion state threshold, determining that the current motion state of the loading point is quasi-static; when the displacement rate of the loading point is greater than or equal to the preset motion state threshold, determining that the current motion state of the loading point is dynamic.

[0014] The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity load provided by the present invention may also have the following feature: wherein the preset motion state threshold is 0.1 mm / s.

[0015] The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity load provided by the present invention may also have the following feature: in step S2, when all loads other than the loading points are equivalently converted into the concentrated load time history curves at the loading points, the translation theorem of force is followed.

[0016] The role and effect of invention

[0017] The control method for integrated static-dynamic loading and active compensation of hypergravity loads in centrifuges according to the present invention includes the following steps: Step S1, designing load time history curves and determining the loading positions of the loads based on the engineering conditions to be simulated; Step S2, converting all loads other than the loading points into equivalent concentrated load time history curves at the loading points; Step S3, converting the load time history curves into discretized time history curves, and linearly superimposing the discretized time history curves to obtain the target load curve; Step S4, during the centrifuge model test, inputting the target load curve into the loading control program, starting the loading device, and collecting the loading pressure and displacement data of the loading points in real time; Step S5, adjusting the output load of the loading device according to the load difference between the loading pressure and the target load at the current moment, so that the load difference converges to a preset error range, and using the load difference as the load compensation value; Step S6, simultaneously calculating the displacement rate of the loading points based on the displacement data of the loading points, and judging the motion state of the loading points based on the displacement rate and a preset motion state threshold; Step S7, according to... The changes in the motion state and direction of the loading point are analyzed, and pre-active load compensation is performed. If neither the motion state nor the direction of the loading point changes, the target load curve and the load compensation value are superimposed and input into the loading control program. If the direction of the loading point changes but the motion state remains unchanged, the target load curve and the opposite of the load compensation value are superimposed and input into the loading control program. If the motion state of the loading point changes, the process returns to step S5. In step S8, steps S5 to S7 are repeated, and the centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load are continuously completed according to the loading control program. Therefore, the control method of the present invention for centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load achieves synchronous coupling application of multiple types of static and dynamic loads in the narrow space of the centrifugal model box by using a single loading device through load equivalent conversion, discretization and superposition. It can completely restore the dynamic-static coupling composite stress condition of the engineering structure in actual service, and greatly improve the fit between the test condition and the actual engineering. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a centrifugal model test structure based on the horizontal force load test of a single pile foundation for an offshore wind turbine, as described in an embodiment of the present invention. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the control method of this invention for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads.

[0021] Example

[0022] Figure 1 This is a flowchart illustrating the control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of a centrifugal model test structure based on a horizontal force load test of a monopile foundation for an offshore wind turbine, as described in an embodiment of the present invention. Figure 2 (a) in the diagram represents the actual location where each load is applied. Figure 2 (b) represents the equivalent concentrated load and equivalent moment applied in the test after all loads have been equivalently converted.

[0024] like Figure 1 , Figure 2 As shown, this embodiment provides a control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads. A centrifugal model test is conducted based on a horizontal force load test of a monopile foundation for an offshore wind turbine. In this embodiment, the model pile diameter D = 120 mm, the soil penetration depth L = 600 mm, and the horizontal force loading point is set at the top of the model pile, 100 mm above the mud surface, which is also equal to the water depth. The specific implementation steps of the method include:

[0025] Step S1: Based on the engineering conditions of the offshore wind farm to be simulated, design the load time history curve and determine the actual loading locations of the loads. The engineering conditions to be simulated specifically include various different loads.

[0026] The loads include dynamic loads and static loads. Dynamic loads include at least one of wind loads, wave loads, and traffic loads. Static loads include at least one of structural self-weight loads, equipment dead loads, and compression / push / pull loads used for bearing capacity testing.

[0027] In this embodiment, wind load This is a concentrated load acting at the actual wind turbine location, 500 mm from the top of the pile. Wave load This refers to the distributed load acting on the underwater portion of the actual monopile foundation. , in the above formula For time, the unit is Static loads include the horizontal loads applied during the horizontal force load test of the offshore wind turbine. This refers to the concentrated load acting on the top of the actual single pile foundation. .

[0028] Step S2 involves converting all loads outside the loading points into equivalent time history curves of concentrated loads at the loading points. During this equivalent conversion, the moment balance and force translation theorems are followed to ensure that the moment generated by the equivalent concentrated load at the loading point is equal to the total moment of all original distributed loads on the rotation center of the model structure.

[0029] Among them, the rotation center of the model structure Determined by the dimensions of the model pile: when L / D < 6 = 0.7L, L / D>10 = 0.3L, when 6≤L / D≤10, = (-0.1L / D+1.3)⋅L, In this embodiment, =0.7L=420 mm.

[0030] The specific method for equivalent load conversion is as follows: For concentrated loads, let the loading point of a concentrated load F be point A, and the loading point of the model structure be point B. Apply a force and an additional moment M with the same magnitude and direction as F at point B, the magnitude of which is r × F, where r is the displacement vector from point A to point B, and × represents the vector cross product. For distributed loads, let the infinitesimal load at any infinitesimal element within its distribution region be dF, the point of application be point P, and the loading point of the model structure be point B. Apply an equivalent resultant force and an additional equivalent moment at point B. The equivalent resultant force is the vector integral of all infinitesimal loads, and the additional equivalent moment is the vector integral of the corresponding additional moments of all infinitesimal loads. The additional moment corresponding to a single infinitesimal load is r. P ×dF, where r is the displacement vector from point P to point B, and × represents the vector cross product. According to the above method, in this embodiment, It applies to the loading point and requires no conversion. The equivalent moment applied at a point 500mm from the top of the pile, converted to the equivalent moment at the loading point. Wave load The equivalent concentrated force converted to the loading point is: Equivalent Moment .

[0031] Step S3: Convert the load time history curve into a discretized time history curve, and then linearly superimpose the discretized time history curves to obtain the target load curve.

[0032] In step S3, when converting the load time history curve into a discretized time history curve, both wind load and wave load are simple harmonic vibration loads. After generating the corresponding simple harmonic continuous time history curve based on the vibration frequency and amplitude, the curves are discretized at equal intervals. The equivalent wind load and wave load time history curves are discretized with a step size of 0.01 s to obtain the discrete load values ​​at each time. Then, the static load and the discrete time histories of the two types of dynamic loads are linearly superimposed to obtain the target load curve.

[0033] The equivalent total concentrated force in this embodiment Total torque .

[0034] Step S4: During the centrifugal model test, the target load curve is input into the loading control program, the loading device is started, and the loading pressure and displacement data of the loading point are collected in real time.

[0035] In this embodiment, after the centrifuge is running stably, the loading control program reads the target load value in 0.01s increments and outputs control commands; the force sensor collects the actual loading pressure acting on the model pile in real time, and the laser displacement sensor collects the horizontal displacement data of the loading point simultaneously. The two sets of data are synchronously transmitted back to the control program as the basis for load compensation and state judgment.

[0036] Step S5: Based on the load difference between the loading pressure and the target load at the current moment, adjust the output load of the loading device so that the load difference converges to the preset error range, and use the load difference as the load compensation value.

[0037] In step S5, the preset error range is 5% of the target load.

[0038] In this embodiment, after the experiment begins, at time t=100 s, the target load... =500 N, = 0 (N⋅mm), at this time the loading pressure collected by the force sensor in real time is 460 N, then the load difference between the loading pressure and the target load at the current moment is 40N, which exceeds the preset error range (500N⋅5% = 25 N). This is caused by the mechanical friction resistance inside the loading device causing an additional super gravity load to the loading device. Therefore, the output load of the loading device is increased by 40N until the loading pressure collected in real time is 500N.

[0039] Step S6: Simultaneously calculate the displacement rate of the loading point based on the displacement data of the loading point, and determine the motion state of the loading point based on the displacement rate and the preset motion state threshold.

[0040] Specifically, in step S6, determining the motion state of the loading point based on the displacement rate and the preset motion state threshold includes:

[0041] The displacement rate of the loading point is compared with a preset motion state threshold. When the displacement rate of the loading point is less than the preset motion state threshold, the current motion state of the loading point is determined to be quasi-static; when the displacement rate of the loading point is greater than or equal to the preset motion state threshold, the current motion state of the loading point is determined to be dynamic.

[0042] In this embodiment, the preset motion state threshold is 0.1 mm / s.

[0043] In this embodiment, based on the horizontal displacement data of the loading point synchronously collected by the laser displacement sensor, it is determined that the loading point is moving to the right at this time, with a displacement rate of 0.01 mm / s, which is less than the preset motion state threshold. Therefore, the current motion state of the loading point is determined to be quasi-static. The load (40 N) added or decreased by the loading device is recorded as the load compensation value. At the same time, the motion state (quasi-static) and the motion direction (to the right) of the loading point are recorded.

[0044] Step S7: Perform pre-active load compensation based on the changes in the motion state and direction of the loading point. The motion direction includes positive and negative directions, and the motion state includes quasi-static and dynamic states.

[0045] If the motion state and direction of the loading point remain unchanged, the target load curve and the load compensation value are superimposed and input into the loading control program. In this embodiment, the target load value + 40N is used as the loading value. If the motion direction of the loading point changes but the motion state of the loading point remains unchanged, the target load curve and the opposite of the load compensation value are superimposed and input into the loading control program. In this embodiment, the target load value - 40N is used as the loading value. If the motion state of the loading point changes, the process returns to step S5.

[0046] Step S8: Repeat steps S5 to S7 to continuously complete the integrated dynamic-static coupling loading and active compensation of the hypergravity load in the centrifuge according to the loading control program. Performing dynamic-static coupling loading and hypergravity load compensation during the centrifuge model test can maximize the accuracy of applying dynamic-static coupling loads in the hypergravity field of the centrifuge.

[0047] The role and effect of the embodiments

[0048] The control method for integrated static-dynamic loading and active compensation of hypergravity loads in centrifuges, as described in this embodiment, includes the following steps: Step S1, designing load time history curves and determining the loading positions based on the engineering conditions to be simulated; Step S2, converting all loads outside the loading points into equivalent concentrated load time history curves at the loading points; Step S3, converting the load time history curves into discretized time history curves, and linearly superimposing the discretized time history curves to obtain the target load curve; Step S4, during the centrifuge model test, inputting the target load curve into the loading control program, starting the loading device, and collecting the loading pressure and displacement data of the loading points in real time; Step S5, adjusting the output load of the loading device based on the load difference between the loading pressure and the target load at the current moment, so that the load difference converges to a preset error range, and using the load difference as the load compensation value; Step S6, simultaneously calculating the displacement rate of the loading points based on the displacement data of the loading points, and judging the motion state of the loading points based on the displacement rate and a preset motion state threshold; Step S7, according to the loading... The changes in the motion state and direction of the loading point are analyzed, and pre-active load compensation is performed. If neither the motion state nor the direction of the loading point changes, the target load curve and the load compensation value are superimposed and input into the loading control program. If the direction of the loading point changes but the motion state remains unchanged, the target load curve and the opposite of the load compensation value are superimposed and input into the loading control program. If the motion state of the loading point changes, the process returns to step S5. In step S8, steps S5 to S7 are repeated, and the centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load are continuously completed according to the loading control program. Therefore, the control method of the present invention for centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load achieves synchronous coupling application of multiple types of static and dynamic loads in the narrow space of the centrifugal model box by using a single loading device through load equivalent conversion, discretization and superposition. It can completely restore the dynamic-static coupling composite stress condition of the engineering structure in actual service, and greatly improve the fit between the test condition and the actual engineering.

[0049] This embodiment also dynamically adjusts the output load of the loading device by comparing the difference between the actual loading pressure and the target load in real time, compensating for hypergravity loads and solving the problem of loading distortion caused by amplified frictional resistance under hypergravity fields.

[0050] This embodiment also introduces a two-dimensional discrimination mechanism for the direction and state of motion of the loading point. The positive and negative values ​​of the compensation value are adaptively and actively adjusted according to the direction of motion of the loading point. At the same time, the compensation values ​​are calibrated separately for quasi-static and dynamic loading conditions, which adapts to the differences in the amplitude and characteristics of frictional resistance under different motion conditions, and realizes active compensation in the full range of dynamic and static coupling.

[0051] This embodiment constructs a full-process adaptive closed-loop control system, which performs state discrimination and compensation optimization cyclically throughout the entire test process. It eliminates the need for repeated calibration before the test and manual intervention during the test, greatly improving the automation level, test efficiency and result repeatability of centrifugation model tests, and adapting to the test requirements of long-term, multi-condition continuous loading.

[0052] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A control method for integrated static-dynamic coupling loading of centrifuges and active compensation of hypergravity loads, characterized in that, include: Step S1: Based on the engineering conditions to be simulated, design the load time history curve and determine the load loading location. Step S2: Convert all loads other than the loading points into equivalent time history curves of concentrated loads at the loading points. Step S3: Convert the load time history curve into a discretized time history curve, and linearly superimpose the discretized time history curves to obtain the target load curve. Step S4: During the centrifugal model test, the target load curve is input into the loading control program, the loading device is started, and the loading pressure and displacement data of the loading point are collected in real time. Step S5: Based on the load difference between the loading pressure and the target load at the current moment, adjust the output load of the loading device so that the load difference converges to a preset error range, and use the load difference as the load compensation value. Step S6: Simultaneously calculate the displacement rate of the loading point based on the displacement data of the loading point, and determine the motion state of the loading point based on the displacement rate and the preset motion state threshold. Step S7: Perform pre-active load compensation based on the changes in the motion state and direction of the loading point; if neither the motion state nor the direction of the loading point changes, then superimpose the target load curve with the load compensation value and input it into the loading control program. If the direction of motion of the loading point changes but the state of motion of the loading point does not change, then the target load curve and the opposite number of the load compensation value are superimposed and input into the loading control program. If the motion state of the loading point changes, return to step S5; Step S8: Repeat steps S5 to S7 to continuously complete the centrifugal dynamic-static coupling integrated loading and active compensation of hypergravity load according to the loading control program.

2. The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads according to claim 1, characterized in that: in, The loads include dynamic loads and static loads. The dynamic loads include at least one of wind loads, wave loads, and traffic loads. The static loads include at least one of structural self-weight loads, equipment dead loads, and compression / push / pull loads used for bearing capacity testing.

3. The control method for integrated dynamic and static coupling loading of centrifuges and active compensation of hypergravity loads according to claim 1, characterized in that: in, In step S3, when converting the load time history curve into a discretized time history curve, for a simple harmonic vibration load, after generating the corresponding simple harmonic continuous time history curve based on the vibration frequency and amplitude, it is discretized at equal intervals.

4. The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads according to claim 1, characterized in that: in, In step S3, when converting the load time history curve into a discretized time history curve, for random cyclic loads, the harmonic superposition method or random phase method is used to convert the power spectral density function in the frequency domain into a continuous random load time history curve in the time domain, and then discretize it at equal intervals.

5. The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads according to claim 1, characterized in that: in, In step S5, the preset error range is 5% of the target load.

6. The control method for integrated dynamic and static coupling loading of centrifuges and active compensation of hypergravity loads according to claim 1, characterized in that: in, The direction of motion includes positive and negative directions, and the state of motion includes quasi-static and dynamic states.

7. The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads according to claim 1, Its features are: Specifically, in step S6, determining the motion state of the loading point based on the displacement rate and the preset motion state threshold includes: The displacement rate of the loading point is compared with the preset motion state threshold. When the displacement rate of the loading point is less than the preset motion state threshold, the current motion state of the loading point is determined to be quasi-static; when the displacement rate of the loading point is greater than or equal to the preset motion state threshold, the current motion state of the loading point is determined to be dynamic.

8. The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads according to claim 1, characterized in that: in, The preset motion state threshold is 0.1 mm / s.

9. The control method for integrated centrifugal dynamic-static coupling loading and active compensation of hypergravity loads according to claim 1, characterized in that: in, In step S2, when all loads other than the loading points are equivalently converted into the concentrated load time history curves at the loading points, the force translation theorem is followed.

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