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Title:
ELECTROMAGNETIC VIBRATION EXCITER FOR ENGINEERING STRUCTURES
Document Type and Number:
WIPO Patent Application WO/2016/108698
Kind Code:
A1
Abstract:
The electromagnetic vibration exciter for engineering structures characterized in that it contains a vibrating mass (5) consisting of the removable demountable steel plates (5) and a set of upper and bottom electromagnets (7, 14, 10, 13) as well as a set of neodymium permanent magnets (8, 11, 15), furthermore on a steel base (1) through the removable demountable spacer element (2) the guides (3) of the vibrating mass (5) consisting of a removable demountable steel parts allow to adjust the weight of the vibrating mass of the exciter to the required value of the dynamic force are mounted.

Inventors:
PAŃTAK, Marek (Os. Akademickie 7/3, 31-866 Kraków, PL)
KOSIERKIEWICZ, Konrad (ul. Płaszowska 36c/6, 30-713 Kraków, PL)
Application Number:
PL2014/000156
Publication Date:
July 07, 2016
Filing Date:
December 29, 2014
Export Citation:
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Assignee:
ESUITE.PL SP. Z O.O. (ul. Hubala 4/5, 26-200 Końskie, PL)
International Classes:
H02K33/16; B06B1/04; G01M7/00; E01D1/00; H02K7/02
Foreign References:
US2535788A1950-12-26
US0955522A1910-04-19
US5203172A1993-04-20
US7955050B12011-06-07
GB702901A1954-01-27
US20130286788A12013-10-31
US8807266B12014-08-19
US2434337A1948-01-13
Attorney, Agent or Firm:
JĘDRZEJEWSKI, Michał (Jarzynka i Wspólnicy, ul. Słomińskiego 19 lok. 522, 00-195 Warszawa, PL)
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Claims:
Patent claims

1. The electromagnetic vibration exciter for engineering structures characterized in that it contains a vibrating mass (5) consisting of the removable demountable steel plates (5) and a set of upper and bottom electromagnets (7, 14, 10, 13) as well as a set of neodymium permanent magnets (8, 11, 15), furthermore on a steel base (1) through the removable demountable spacer element (2) the guides (3) of the vibrating mass (5) consisting of a removable demountable steel parts allow to adjust the weight of the vibrating mass of the exciter to the required value of the dynamic force are mounted, moreover the vibrating mass of the exciter, except the steel plates (5), also includes aluminum cover (16) with built-in permanently the neodymium permanent magnets (15), and the vibrating mass of the exciter (5) cooperates with steel guides of the exciter (3) through the linear ball bearings (17), furthermore on the top and bottom of the steel guides (3) there are the aluminum plates (4, 6) forming, together with the steel guides (3), the bearing frame of the exciter, wherein the neodymium permanent magnets (15) placed in the aluminum covers (16) of the vibrating mass of the exciter (5) form, together with the electromagnets (7, 10, 13, 14) arranged on the surface of the aluminum plates (4, 6) and a steel cores (9, 12, 13, 14) cooperating with additional neodymium permanent magnets (8, 11), the system of unipolar, repelling magnets allow to stabilize the vibrating mass in the position of equilibrium.

2. The electromagnetic vibration exciter for engineering structures according to claim 1, characterized in that it contains the additional interchangeable elements forming the guides (3) of the vibrating mass (5) and a set of return springs or return rubber straps (22). 3. The electromagnetic vibration exciter for engineering structures according to claim 1 or 2, characterized in that it contains the additional permanent magnets (23) mounted on the side walls of the exciter vibrating mass (5) forming, together with additional electromagnet (25) placed on the additional peripheral beams (24), the excitation system or assist system inducing the movement of the vibrating mass (5).

Description:
Electromagnetic vibration exciter for engineering structures

The invention relates to an electromagnetic vibration exciters for the engineering structures, generating a large dynamic force of 0.5-15 kN in the range of low frequency vibrations 0,35-5,0 Hz. The exciter is designed to induce a vertical and horizontal vibrations during the dynamic field tests of the engineering structures in order to identify their mode shapes and determine their dynamic characteristics. Particularly preferably may be used during dynamic tests of the bridges (identification of the mode shapes, identification of the vibration damping parameters, investigation of the amplitudes of a resonant vibration). It can also be used during the dynamic test of the industrial buildings and structures, sports facilities and concert halls as well as the residential and public buildings. The waveform of the force generated by the exciter depends on the generated source function. Using a function generator with the appropriate characteristics of the output signal and the signal amplifier, it is possible to induce a sinusoidal, rectangular, triangular, random (stochastic) or pulse waveform of the force. The value of the force generated by the exciter depends on the vibration frequency, the vibration acceleration and the value of vibrating mass of the exciter.

The solution presented in the application has a vibrating mass varying in the range of 100-600 kg. Limitation of the maximum value of the vibrating mass up to 600 kg results from the need to ensure the possibility of transport of the exciter to the place of the use. The upper value of the vibrating mass can be increased to 800 kg. The minimum value of the vibrating mass of the exciter results from the specific destination of the exciter designed to use in the dynamic tests of building structures to generate increased value of dynamic force to excite the free vibrations of the structures with amplitudes that enable their correct measurement. In case of necessity of the excitation of the vibrations of lightweight and dynamically susceptible structures the minimum value of the vibrating mass of the exciter can be reduced.

The invention includes issues of electrical engineering and electronics, mechanical engineering and civil engineering.

There are known electrodynamic exciters operating in the range of high frequencies used on production lines, in industry in quality control laboratories, in research laboratories as well as for calibration of vibration sensors or fatigue tests of dynamically susceptible structures. They are characterized by the possibility of efficient excitation of high frequency vibrations / > 10.0 Hz to several kHz. This range far exceeds the basic ranges of natural frequencies of building structures (0,3-10,0 Hz). Previous developed electrodynamic vibration exciters, in the case of the possibility of excitation of frequencies in the range of 1.0-10.0 Hz are characterized by possibility of excitation of dynamic force of a low value. These two features of previous developed electrodynamic vibration exciters significantly limit their usefulness for the purpose of inducing of the vibrations of buildings and civil engineering structures which require the generation of the force of large values in frequency range of 0,3-10,0 Hz, with special regard to the frequency range of 0.3-5.0 Hz. The electromagnetic vibration exciter for engineering structures according to the invention is characterized in that it contains a vibrating mass consisting of the removable demountable steel plates and a set of upper and bottom electromagnets as well as a set of neodymium permanent magnets, furthermore on a steel base the guides of the vibrating mass consisting of a removable demountable steel parts allow to adjust the weight of the vibrating mass of the exciter to the required value of the dynamic force through the removable demountable spacer element are mounted, moreover the vibrating mass of the exciter, except the steel plates, also includes aluminum cover with built-in permanently the neodymium permanent magnets, and the vibrating mass of the exciter cooperates with steel guides of the exciter through the linear ball bearings, furthermore on the top and bottom of the steel guides there are the aluminum plates form, together with the steel guides of the vibrating mass of the exciter, the bearing frame of the exciter, wherein the neodymium permanent magnets placed in the aluminum covers of the vibrating mass of the exciter form, together with the electromagnets arranged on the surface of the aluminum plates belonging to the bearing frame of the exciter and a steel cores cooperating with additional neodymium permanent magnets, the system of unipolar, repelling magnets allow to stabilize the vibrating mass in the position of equilibrium.

Preferably, the vibration exciter contains additional interchangeable elements forming the guides of the vibrating mass and a set of the return springs or the return rubber straps.

Preferably, the vibration exciter contains the additional permanent magnets mounted on the side walls of the exciter vibrating mass forming, together with additional electromagnet placed on the additional peripheral beams, the excitation system or assist system inducing the movement of the vibrating mass. The exciter according to the invention generates the dynamic forces of large values in the range of low frequency vibration of buildings and civil engineering structures (0,35-5,0 Hz). This objective is reached by utilization of the set of strong industrial electromagnets with the ability to control the magnetic force, the permanent magnets and the set of steel plates suspended in a magnetic field and forming the vibrating mass of the exciter. The permanent magnets and a set of electromagnets stabilizes the vibrating mass of the exciter in the position of equilibrium. The vibrating mass of the exciter is made with a set of removable steel plates mounted on linear ball bearings allowing it to move along the steel guides. The two main electromagnets placed in the axis of the vibrating mass, controlled by a function generator with an amplifier, cause a changes in the magnetic force what leads to deflection of the vibrating mass from its equilibrium position and the generation of the dynamic force. The value of the force depends on the frequency of vibration, the weight of the vibrating mass and the acceleration of the vibrating mass.

The invention is illustrated in the embodiments in Figure, in which fig. 1 shows a cross section of the exciter, fig. 2 shows a longitudinal section of the exciter, fig. 3 shows a plan view of the exciter, fig. 4 - 9 show views and sections of the main components of the exciter, fig. 10 - 11 - show the second variant of the exciter, fig. 12 - 13 - shows the third variant of the exciter, fig. 14 - show the exciter set in a horizontal position, and fig 15 and 16 show examples of application of the exciter according to the invention.

In fig. 1-3 the following designations are used:

1 - steel base

2 - removable steel spacer element 3 - removable parts of the steel guides

4 - aluminum top cover

5 - steel plates 16 pes. (vibrating mass of the exciter)

6 - aluminum bottom plate

7 - induction coil with core (upper electromagnet)

8 - upper neodymium permanent magnet

9 - upper steel core

10 - induction coil with core (bottom electromagnet)

11 - bottom neodymium permanent magnet

12 - bottom steel core

13 - induction coil with core (set of bottom electromagnets)

14 - induction coil with core (set of upper electromagnets)

15 - neodymium permanent magnets in the vibrating mass

16 - upper and bottom aluminum cover of the vibrating mass

17 - linear ball bearings

18 - screws

19 - rubber bumpers

20 - permanent magnet casing

21 - power leads of electromagnets

In fig., 4 the following designations are used:

1 - steel base

2 - removable steel spacer element

1.1 - holes for the bottom neodymium magnets (11)

1.2 - holes for screws (18)

1.3 - holes for power leads of induction coils

2.1 - guides of the linear ball bearings (17) 2.2 - holes for screws

In fig. 5 the following designations are used:

2 - removable steel spacer element

3 - removable parts of the steel guides

2.1 - guides of the linear ball bearings (17)

2.2 - holes for screws (18)

3.1 - guides of the linear ball bearings (17)

3.2 - holes for screws (18)

In fig. 6 the following designations are used:

4 - aluminum top cover

2 - removable steel spacer element

4.1 - holes for the induction coils with core (7, 9, 14) 4.2 - holes for screws (18)

4.3 - holes for power leads of induction coils

2.1 - guides of the linear ball bearings

2.2 - holes for screws (18) In fig. 7 the following designations are used:

5 - steel plates (vibrating mass of the exciter)

5.1 - holes for guides of the linear ball bearings (17)

In fig. 8 the following designations are used:

6 - aluminum bottom plate

6.1 - holes for the induction coils with core (10, 12, 13)

6.2 - holes for guides on the element No. (2) In fig. 9 the following designations are used:

16 - upper and bottom aluminum cover of the vibrating mass

16.1 - holes for the neodymium magnets (15),

16.2 - holes for guides of the linear ball bearings (17).

The essential elements of the vibration exciter are the vibration mass (5) consisting of 16 removable steel plates (5) connected to the steel guides (3) by means of the linear ball bearings (17), the set of the upper and bottom electromagnets (7, 14, 10, 13) and the set of neodymium permanent magnets (8, 11, 15).

On the steel base (1) through the removable (demountable) steel spacer element (2) the guides of the vibrating mass (3) consisting of sixteen removable (demountable) steel plates enabling adjustment of the weight of the vibrating mass of the exciter to the required value of dynamic force are mounted. The division of the guides on the removable parts (3) allows to keep a constant stroke of the electromagnet during variable quantity of steel plates (5) forming the vibrating mass of the exciter. The vibrating mass of the exciter, except the steel plates (5), also includes aluminum cover (16) with built-in permanently the neodymium permanent magnet (15). The vibrating mass of the cooperates with steel guides of the exciter through the linear ball bearings (17).

The neodymium permanent magnets (15) form, together with the electromagnets (13, 14) arranged around the perimeter of the aluminum plates (16) and the permanent magnets (8, 11) cooperating with two steel cores (9, 12) the system of unipolar (repulsive) magnets allow to stabilize the vibrating mass in the position of equilibrium. This stabilization is possible by tuning the magnetic field generated by electromagnets (13, 14). The electromagnets (7, 10) supplied by the current with variable flow direction are responsible for the generation of magnetic field changes and inducing the movement of the vibrating mass. Additionally, they can be supported by electromagnets (13, 14). The changes in the polarity of the electromagnets allows to alternately attract and repulse the vibrating mass of the exciter. The application of the aluminum plates (4, 6) and the presence of a constant magnetic field generated by a set of neodymium permanent magnets protects the vibrating mass against total attraction by the electromagnets and before its immobilization.

In order to enable movement of the vibrating mass of the exciter (5) the coils (7, 10, 13, 14) have to be alternately supplied (by the current with variable flow direction) to obtain a variation of the poles of the electromagnets, and an effect of repulsion and attraction between the electromagnets (1, 10, 13, 14) and permanent magnets embedded in the vibrating mass of the exciter. During this the allowable relative duty cycle (allowable working time, allowable power-on time) of electromagnets (ED [%]) defined as the percentage ratio of the power-on time (working time) in the cycle to the cycle time, must be followed according to DIN VDE 0580:2011-11. The cycle time is the sum of working time (power-on time) and de-energized time. In accordance with the applicable regulations the maximum cycle time is 300 s. The need to comply with the allowable relative duty cycle of electromagnets is related to their protection against overheating and damage.

The duty cycle of electromagnets used in the exciter results from the frequency of the induced vibrations exert an influence on the frequency of lifting and falling of the vibrating mass which is related to the frequency of power supply to the electromagnets. During the movement of the vibrating mass of the exciter upward the bottom and upper electromagnets will be supplied with current causing respectively repulsion the bottom permanent magnets (15) by the electromagnets (10, 13) and the attraction of the upper permanent magnets (15) by the electromagnets (7, 14). During the movement of the vibrating mass of the exciter downwards the power supply of the electromagnets can be turned off by the part of the cycle. In order to obtain a smooth motion of the vibrating mass the relative duty cycle of electromagnets (ED [%]) will be of 60%, of which 50% is a power supply with flow causing appropriate polarity of the electromagnets (as described above) which leads to the repulsion of the bottom magnets and attraction of the upper magnets and 10% falls on a change of direction of the current flow. The de-energized break constitutes 40% of the cycle time.

Obtaining the variable current flow energizing the electromagnets (7, 10, 13, 14) requires the use of an external function generator and an amplifier of the function generator output signal.

In order to generate the dynamic force in the range of 0.5-15.0 kl\l it is necessary to ensure an empty space above and below the vibrating mass of the exciter allowing it to move freely over a distance of 130 mm. The empty space above and below the vibrating mass in the posit of the vibrating mass as in fig. 1 (position of equilibrium), sufficient to generate the force of 2.0-7.0 kN at vibration frequency of 1.5-5.0 Hz, is 65 mm.

The weight of the vibrating mass of the exciter and its vibration amplitude should be adjusted to the value of necessary to generate dynamic force in accordance with known relationships resulting from the second law of dynamics and equations of harmonic motion: F = m-o, a = ^ n 2 -f 2 -A-sin(2ntl (m - weight of the vibrating mass of the exciter, o - acceleration of the vibrating mass of the exciter, A - amplitude of the vibrating mass of the exciter, t - the time needed to travel a distance S = 2A equal to a period of vibration

t = T = l/f, f - vibration frequency, T - period of vibration). The total weight of the vibrating mass required to generate the dynamic force of 1-3 kN at low frequencies (0.3-1.0 Hz) is 800 kg. To generate the dynamic force of high value at low frequencies it is necessary to ensure a sufficiently large vibration amplitude of the vibrating mass (5). In the present exciter it can be achieved by the use of additional removable elements (3) forming the guides of the vibrating mass and by assisting of the movement of the vibrating mass by a set of return springs (22) or return rubber straps attached by one end to the vibrating mass of the exciter (5) and by the second end to the bearing frame of the exciter formed by the elements 1, 2, 3, 4, 16. The return springs or the return rubber straps should be connected to the top and bottom of the vibrating mass and on the both sides of the vibrating mass (left and right). Scheme of the set of the return springs with fastening system is presented in fig. 10 - 11.

In case of the demand for a very large value of the dynamic force at low frequencies, it is necessary to provide the possibility of large displacements of the vibrating mass of the exciter (5). In the present exciter it can be achieved by increasing the amount of height of the vibrating guides (2, 3) with simultaneous introduction of a set of additional permanent magnets in the side walls of the vibrating mass of the exciter and peripheral beams (24) containing induction coils with a core (25) forming the electromagnets which cause or assist the motion of the vibrating mass (5). 1 - steel base

2 - removable steel spacer element

3 - removable parts of the steel

guides

4 - aluminum top cover

5 - steel plates (vibrating mass of the

exciter)

6 - aluminum bottom plate

16 - upper and bottom aluminum cover of the vibrating mass

23 - neodymium permanent magnets

24 - peripheral steel beam

25 - induction coils with core (additional electromagnets)

26 - power leads for additional induction coils.

The electromagnets formed by the coil with core (25) powered by current with variable flow direction act on the permanent magnets (23) causing the movement of the vibrating mass (5). After reducing the distance of the permanent magnets (15) from the upper electromagnet (7, 14) or bottom electromagnets (10, 13) the power supply of electromagnets is activated and the attraction or repulsion of the vibrating mass occur accordingly.

In order to avoid collisions of the vibrating mass with the aluminum bottom plate (6) and aluminum top cover (4) a set of rubber bumpers (19) is used. Additional anti-collision protection, resulting from the use of aluminum plates (4, 6, 16), are the eddy currents generated when the magnets approaching to the aluminum plates and slowing down the movement of the falling mass.

By using the steel guides and the linear ball bearings the exciter can operate in a vertical position (fig. 1) - generation of the dynamic vertical force and in horizontal position when it is placed on the side faces of the guides (3) (fig. 14 ) - generation of the dynamic horizontal force.

In the case of excitation of the horizontal vibration allowable relative duty cycle of electromagnets (10, 13 and 7, 14) is 60% as in the case of vertical vibration. In order to ensure the de-energized break the movement of the vibrating mass must be supported by return springs or return rubber straps (22).

The invention in the example of application is illustrated in fig. IS and 16. Especially effectively the vibration exciters can be used to study the frequency and mode shapes of building structures, to determine the vibration damping parameters, to impact assessment of the vibration on the supporting elements and foundations of the structures and to impact assessment of the vibration on the fatigue effects.

An example of the application presents the dynamic tests of the footbridge performed to measure the vibration acceleration of the footbridge deck and to verify the requirements of the comfort of use criteria for footbridges.

A wider scope of application of the exciter includes: excitation of the vibrations of the high-rise buildings, generation of the vibrations of the large-span floors in industrial halls and public buildings, generation of the vibrations of the tribune in sports facilities, generation of the vibrations of roofs.