CN112903325B - Frequency-adjustable single-degree-of-freedom pitching motion test system - Google Patents

Frequency-adjustable single-degree-of-freedom pitching motion test system Download PDF

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CN112903325B
CN112903325B CN202110040956.4A CN202110040956A CN112903325B CN 112903325 B CN112903325 B CN 112903325B CN 202110040956 A CN202110040956 A CN 202110040956A CN 112903325 B CN112903325 B CN 112903325B
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upper frame
rotating shaft
rotating
platform
freedom
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CN112903325A (en
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王进廷
丁昊
潘坚文
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Tsinghua University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M99/00—Subject matter not provided for in other groups of this subclass
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    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
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Abstract

The invention relates to a frequency-adjustable single-degree-of-freedom pitching motion test system which comprises a support frame, a rotating platform and a rotating bearing, wherein the support frame is provided with a support frame; the rotary platform comprises a second upper frame and a hanging plate which are fixedly connected, the middle part of the first upper frame is sleeved on a rotating shaft, and the top end of the hanging plate is fixed on the rotating shaft and swings along with the rotation of the rotating shaft; the first upper frame and the second upper frame are connected between two side edges parallel to the rotating shaft through a plurality of symmetrically arranged springs; and the rotating stiffness, the moment of inertia and the natural vibration frequency of the rotating platform are adjusted by changing the number and the stiffness of the springs and/or the mass of the rotating platform. The test system has one degree of freedom of rotation, can conveniently and quickly adjust the rotational inertia and the natural vibration frequency of the rotating platform so as to meet the frequency requirement of the test on the structure, and is easy to install and maintain.

Description

Frequency-adjustable single-degree-of-freedom pitching motion test system
Technical Field
The invention belongs to the technical field of civil engineering structure dynamics tests, and particularly relates to a frequency-adjustable single-degree-of-freedom pitching motion test system.
Background
With the development of construction technology, structural vibration control has become an important research topic in civil engineering. Modern bridges are designed as large span, lightweight, flexible, elongated structures with low inherent damping, and therefore they exhibit high dynamic response sensitivity to wind loads. In order to ensure the safety of the bridge structure, a proper structure control device is needed to restrain the pitching motion of the bridge caused by wind load. Meanwhile, some offshore structures, such as Floating Wind Turbines (FWTs), also need to be studied for controlling pitch motion vibration. FWTs are characterized by high-rise, slender towers, long blades and large unit capacity. The natural environment of the FWTs has the characteristics of special geological conditions, complex and changeable operating conditions and the like. The operation of the generator set rotor and the rotation of the wind wheel blades can cause the vibration of the fan foundation and the tower drum, and the combined action of a plurality of loads such as wind load, wave load, ocean current load, ice load, earthquake load and the like makes the vibration characteristics of the fan foundation and the tower drum more complex. In general, pitching of FWTs can adversely affect overall wind turbine structure and generator performance. With the increasing interest in wind power and the development of FWTs, there is a need to study the characteristics of pitch motion and develop a practical vibration control device to suppress pitch motion.
At present, the following two types of test devices are mainly used for researching the pitching motion of the structure. (1) A large rotating platform test instrument based on a hydraulic cylinder and a crank; (2) a test instrument based on a large wave trough and a floating structure platform. The existing test device platform usually needs large and heavy complex instrument equipment in order to realize the simulation of the pitching motion of the structure, and meanwhile, needs precise instrument debugging and operation, and has high test cost and long preparation period.
Disclosure of Invention
The invention aims to provide a frequency-adjustable single-degree-of-freedom pitching motion test system, which is convenient and rapid to simulate the pitching motion characteristic of a specific structure, is easy to adjust the rotational inertia and the natural vibration frequency of a rotating platform so as to meet the frequency requirement of the test on the structure, and is easy to install and maintain.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a frequency-adjustable single-degree-of-freedom pitching motion test system which is characterized by comprising a support frame and a rotating platform; the rotary platform comprises a second upper frame and a hanging plate which are fixedly connected, the middle part of the first upper frame is sleeved on a rotating shaft, and the top end of the hanging plate is fixed on the rotating shaft and swings along with the rotation of the rotating shaft; the first upper frame and the second upper frame are connected between two side edges parallel to the rotating shaft through a plurality of symmetrically arranged springs; the adjustment of the rotating stiffness, the moment of inertia and the natural frequency of the rotating platform is realized by changing the number and the stiffness of the springs and/or the mass of the rotating platform;
n is respectively arranged between two sides of the first upper frame and the second upper frame parallel to the rotating shaftiEach tensile and compressive stiffness is KiOf the spring of (1), the rotational stiffness K of the rotary platformθEstimated according to the following formula:
Figure BDA0002895331200000021
Figure BDA0002895331200000022
wherein l is a half of the length of a side of the first upper frame perpendicular to the rotation axis; m is the spring types with different tensile and compression stiffness arranged on one side of the first upper frame and the second upper frame parallel to the rotating shaft;
moment of inertia J of the rotating platformθThe relationship between the mass of the material and the mass of the material satisfies the following requirement:
Figure BDA0002895331200000023
in the formula, msIs the mass of the hanger plate, rsThe distance from the bottom of the hanger plate to the rotation axis.
Further, the height of the support frame is 120% -300% of the distance from the bottom of the rotating platform to the rotating shaft; the initial length of each spring is 5% -95% of the vertical distance between the first upper frame and the second upper frame when the two frames are parallel; the length of the side edge of the first upper frame perpendicular to the rotating shaft is 2-10 times of the perpendicular distance between the first upper frame and the second upper frame when the first upper frame and the second upper frame are parallel.
Furthermore, the number N of the springs arranged between the two sides of the first upper frame and the second upper frame parallel to the rotating shaft is more than or equal to 0.
Compared with the prior art, the test system has one degree of freedom of rotation, can conveniently and quickly adjust the rotational inertia and the natural vibration frequency of the rotating platform to meet the frequency requirement of the test on the structure, and is easy to install and maintain. The concrete characteristics and beneficial effects are as follows:
1. according to the invention, the rotating rigidity of the rotating platform can be conveniently and rapidly adjusted by adjusting the number of the connecting springs or the types of the springs between the rotating platform and the support frame.
2. The invention realizes the effect of conveniently and quickly adjusting the rotary inertia of the rotary platform by adjusting the mass of the lower part of the rotary platform.
3. The system of the invention can quickly adjust the rigidity and the moment of inertia of the rotating platform, so the rotating natural frequency can be conveniently adjusted to a specified value.
4. The damper can be arranged on the rotary platform and used as a test system for testing the control efficiency of the damper on the pitching motion of the structure.
5. The invention can carry out the free damping motion test of the structure, and can also use an additional actuator to act on the rotating platform to carry out the pitching motion test of forced vibration.
Drawings
Fig. 1 is a schematic structural diagram of a frequency-adjustable single-degree-of-freedom pitching motion testing system according to an embodiment of the present invention.
FIG. 2 is a schematic structural view of a support frame in the testing system shown in FIG. 1.
FIG. 3 is a schematic structural view of a rotary platform in the testing system shown in FIG. 1.
Reference numbers in the figures:
1-a support frame; 11-a first upper frame; 12-a vertical support; 2-rotating the platform; 21-a second upper frame; 22-a hanger plate; 3-a rotating shaft; 4-spring.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.
As shown in fig. 1 to 3, the system for testing a single degree of freedom pitching motion with adjustable frequency according to the embodiment of the present invention includes a support frame 1 and a rotating platform 2, wherein the support frame 1 includes a first upper frame 11 and a vertical support 12 which are fixedly connected, and the rotating platform 2 includes a second upper frame 21 and a hanging plate 22 which are fixedly connected. The middle part of the first upper frame 11 of the support frame 1 is sleeved on a rotating shaft 3, and the top end of the hanging plate 22 of the rotating platform 2 is fixed on the rotating shaft 3. N springs 4 are symmetrically arranged between two sides of the first upper frame 11 and the second upper frame 21 parallel to the rotating shaft 3. In the test process, the support frame 1 is kept still all the time, the rotating platform 2 swings along with the rotation of the rotating shaft 3, and the springs 4 between the first upper frame 11 and the second upper frame 21 are stretched or compressed.
The specific implementation and functions of each component part of the embodiment of the invention are described as follows:
in the test system of this embodiment, the support frame 1, the rotary platform 2, the rotary shaft 3 and the spring 4 are all made of steel, and the support frame 1 and the rotary platform 2 may be an integrally formed structure or an assembled structure. The first upper frame 11 of the support frame 1 and the second upper frame 21 of the rotating platform 2 are rectangular frames, and the first upper frame 11 is positioned above the second upper frame 21 in parallel when the spring is in an initial state; the experimental system is arranged on the ground or other fixed platforms through the vertical supporting piece 12 of the supporting frame 1, the top of the vertical supporting piece 12 is provided with a hole for the rotating shaft 3 to pass through, so that the rotating shaft 3 is arranged on the top of the vertical supporting piece 12; the second upper frame 21 is fixed on the middle upper part of the hanging plate 22, the bottom of the hanging plate 22 is a flat plate, the hanging plate 22 can rotate along with the rotating shaft 3, namely the vertical length of the rotating platform 2 is smaller than the distance from the rotating shaft 3 to the ground; when the springs 4 arranged between the first upper frame 11 and the second upper frame 21 are in an initial state, the springs are perpendicular to the plane where the two upper frames are located, the rigidity of each spring 4 can be the same or different, and the rotating rigidity required by the test can be ensured to be combined, so that the adjustment of the natural vibration frequency of the rotating platform can be realized. The moment of inertia of the rotating platform 2 is adjusted by adjusting the weight of the bottom plate of the hanger plate 22 (in particular, different weights may be placed on the bottom plate of the hanger plate 22).
The principle of selecting the dimensions of the components in this embodiment is as follows: the height of the support frame 1 is 120-300% of the distance from the bottom of the rotating platform hanging plate 22 to the rotating shaft 3, so as to ensure that the bottom of the rotating platform hanging plate 22 does not generate friction collision with the ground in the moving process; the initial length of each spring 4 is 5% -95% of the vertical distance between the first upper frame 11 and the second upper frame 21 when the two frames are parallel, so as to ensure that each spring 4 has a certain space to be stretched or compressed; the length of the side edge of the first upper frame 11 perpendicular to the rotating shaft 3 is 2-10 times of the perpendicular distance between the first upper frame 11 and the second upper frame 21 when the two frames are parallel, so as to ensure that the spring can generate enough deformation when the rotating platform 2 moves.
The number of the springs 4 provided between the two side edges of the first upper frame 11 and the second upper frame 21 parallel to the rotation shaft 3 is N, N is equal to or greater than 0, the larger the number N of the springs 4 is, the higher the natural frequency of the rotary platform 2 is, and when the number N of the springs 4 is equal to 0, the lowest the natural frequency of the rotary platform 2 is, that is, the lowest natural frequency that the test system can provide. In this embodiment, 4 vertical springs 4 are uniformly distributed between two sides of the first upper frame 11 and the second upper frame 21 parallel to the rotation axis 3.
The working principle of the test system is as follows: when the rotary platform 2 rotates around the rotation axis 3, the springs 4 will be stretched periodically, thereby influencing the natural frequency of vibration of the rotary platform 2. The test system can conveniently and quickly adjust the moment of inertia of the rotary platform 2 by adjusting the mass of the flat plate at the bottom of the hanging plate 22 of the rotary platform and adjust the rotating rigidity (K) of the rotary platform 2 by adjusting the number of the springs 4 or the types of the springs 4 between the rotary platform 2 and the support frame 1θ[N·m/rad]) Thereby realizing the moment of inertia (J) of the rotary platform 2θ[kg·m2]) And natural frequency (ω)θ[rad/s]) The test requirement of pitching motion of a structure with single degree of freedom (namely the rotational degree of freedom of a rotating platform) is met by convenient adjustment, and the calculation formula is
Figure BDA0002895331200000041
Specifically, n is provided between both sides of the first upper frame 11 and the second upper frame 21 parallel to the rotation axis 3iEach tensile and compressive stiffness is Ki[N/m](i-1, 2, …, m) (i.e. one side containing both tensile and compressive stiffness K)iThe number of the springs is ni) Then rotational stiffness KθThe estimate can be approximated as follows:
Figure BDA0002895331200000042
Figure BDA0002895331200000043
in the formula, l is half of the length of the side edge of the first upper frame 11 perpendicular to the rotating shaft 3, namely the moment arm of each spring force; 57.3 is the number of degrees after converting 1rad to an angle; m is a kind of spring having different tensile and compressive rigidities provided on the first upper frame 11 and the second upper frame 21 in parallel to the side of the rotation shaft 3.
Moment of inertia J of rotating platformθThe relationship to its mass can be approximated as follows:
Figure BDA0002895331200000044
in the formula, ms[kg]For the mass of the bottom plate of the rotating platform hanger plate 22, rs[m]The distance from the bottom of the rotating platform hanger plate 22 to the axis of rotation 3.
Further, the present embodiment may install a damper on the rotating platform 2 as a test system for checking the efficiency of the damper in controlling the pitching motion of the structure. Specifically, after the frequency adjustment of the test system is completed, the damper is fixed to the rotary platform 2, and may be fixed by a G-clamp. The length and width of the damper should be smaller than the length and width of the rotary platform 2 and the height of the damper should be smaller than the length of the rotary platform 2 in the vertical direction. By fixing a sensor (e.g., an acceleration sensor) for monitoring the motion response of the rotary platform 2 to a flat plate at the bottom of the rotary platform hanger plate 22, the control efficiency of the damper can be quantitatively analyzed by comparing the monitoring signals with and without the damper.
Further, the present embodiment can perform a free damping motion test of the structure, and can also perform a pitch motion test of forced vibration by using an additional actuator to act on the rotating platform 2. In the case where only the support frame 1, the rotary platform 2, the rotary shaft 3 and the spring 4 in the present embodiment are used, the rotary platform 2 is given an initial angle deviating from the vertical equilibrium position, after which the rotary platform 2 will perform a free damping motion. When additional actuators are used to apply force to the rotating platform 2, the rotating platform 2 will undergo forced vibration. Additional actuators may apply a given control force to the bottom of the second upper frame 21 to influence the movement pattern of the rotating platform 2.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention and is not actually limited thereto. Therefore, if the person skilled in the art receives the teaching, it is within the scope of the present invention to design the similar manner and embodiments without departing from the spirit of the invention.

Claims (5)

1. A frequency-adjustable single-degree-of-freedom pitching motion test system is characterized by comprising a support frame (1) and a rotating platform (2); the supporting frame (1) comprises a first upper frame (11) and a vertical supporting piece (12) which are fixedly connected, the rotating platform (2) comprises a second upper frame (21) and a hanging plate (22) which are fixedly connected, the middle part of the first upper frame (11) is sleeved on a rotating shaft (3), and the top end of the hanging plate (22) is fixed on the rotating shaft (3) and swings along with the rotation of the rotating shaft (3); the first upper frame (11) and the second upper frame (21) are connected between two side edges parallel to the rotating shaft (3) through a plurality of symmetrically arranged springs (4); the adjustment of the rotating rigidity, the moment of inertia and the natural vibration frequency of the rotating platform (2) is realized by changing the number and the rigidity of the springs (4) and/or the mass of the rotating platform (2);
n is respectively arranged between two sides of the first upper frame (11) and the second upper frame (21) which are parallel to the rotating shaft (3)iEach tensile and compressive stiffness is KiOf the spring of (2), the rotational stiffness K of the rotary platform (2)θEstimated according to the following formula:
Figure FDA0003358849280000011
Figure FDA0003358849280000012
wherein l is a half of the length of the side of the first upper frame (11) perpendicular to the rotation axis (3); m is the number of spring types with different tensile and compression stiffness arranged on one side of the first upper frame (11) and the second upper frame (21) parallel to the rotating shaft (3);
moment of inertia J of the rotating platformθThe relationship between the mass of the material and the mass of the material satisfies the following requirement:
Figure FDA0003358849280000013
in the formula, msIs the mass of the hanger plate (22), rsThe distance from the bottom of the hanging plate (22) to the rotating shaft (3);
the height of the support frame (1) is 120-300% of the distance from the bottom of the rotary platform (2) to the rotary shaft (3); the initial length of each spring (4) is 5-95% of the vertical distance between the first upper frame (11) and the second upper frame (21) when the two frames are parallel; the length of the side edge of the first upper frame (11) perpendicular to the rotating shaft (3) is 2-10 times of the perpendicular distance between the first upper frame (11) and the second upper frame (21) when the two frames are parallel.
2. The single degree of freedom pitching motion testing system of claim 1, wherein said support frame (1), said rotating platform (2), said rotating shaft (3) and said spring (4) are made of steel.
3. The single-degree-of-freedom pitching motion testing system according to claim 1, wherein the number N of springs (4) disposed between two sides of the first upper frame (11) and the second upper frame (21) parallel to the rotating shaft (3) is not less than 0.
4. The single degree of freedom pitch motion test system of claim 1, wherein each spring (4) is vertically disposed between the first upper frame (11) and the second upper frame (21) in the initial state.
5. The single degree of freedom pitch motion test system of claim 1, wherein the first upper frame (11) and the second upper frame (21) are both rectangular frames.
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CN203499048U (en) * 2013-09-10 2014-03-26 隔而固(青岛)振动控制有限公司 Frequency regulating device for swinging type turning mass damper
CN105369932A (en) * 2015-11-24 2016-03-02 华北水利水电大学 Tuned mass damper frequency adjusting device and implementing method thereof

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CN1228618C (en) * 2003-12-09 2005-11-23 西北工业大学 Measuring method and device for moment of inertia and product of inertia
JP5532238B2 (en) * 2010-07-08 2014-06-25 国立大学法人東京工業大学 Rigid body characteristic identification device and rigid body characteristic identification method
CN101915638B (en) * 2010-07-26 2012-09-05 重庆大学 Measuring device and method of all-inertial parameter of rigid body
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Publication number Priority date Publication date Assignee Title
WO2011001447A2 (en) * 2009-06-16 2011-01-06 Zen Technologies Limited A motion platform system
CN203499048U (en) * 2013-09-10 2014-03-26 隔而固(青岛)振动控制有限公司 Frequency regulating device for swinging type turning mass damper
CN105369932A (en) * 2015-11-24 2016-03-02 华北水利水电大学 Tuned mass damper frequency adjusting device and implementing method thereof

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