A quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber

Abstract

The present invention discloses a quasi-zero stiffness vibration isolation device containing a mechanical frequency modulation type dynamic vibration absorber. The vibration isolation device is composed of a quasi-zero stiffness vibration isolation main system and a dynamic vibration absorber subsystem; it mainly includes a bearing platform, a negative stiffness mechanism, and a dynamic vibration absorber. Based on the traditional "spring - mass block" vibration absorber, the present invention proposes an adjustable frequency dynamic vibration absorber with a "spring strip - sliding mass block" structure, and adds 4 negative stiffness mechanisms to the traditional linear main system. The positive and negative stiffnesses are connected in parallel to form a quasi-zero stiffness vibration isolation main system, and a quasi-zero stiffness vibration isolation device containing a mechanical frequency modulation type dynamic vibration absorber is designed. The vibration isolation device can adjust the natural frequency of the dynamic vibration absorber by changing the effective length of the spring strip, break through the limitation that the traditional dynamic vibration absorption device is only applicable to a single excitation frequency, broaden the excitation frequency adaptation range, realize the self-adaptability of the excitation frequency, reduce the amplitude of the quasi-zero stiffness vibration isolation main system, and thus achieve the self-adaptive ultra-low frequency vibration isolation effect.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-low frequency vibration isolation, and particularly to a quasi-zero stiffness vibration isolation device including a mechanical frequency modulation type dynamic vibration absorber. Background Art

[0002] A dynamic vibration absorber is a spring-mass oscillator system composed of components such as mass, spring, and damper. It is connected to the main system through elastic elements and damping elements, so that all the energy of the external excitation acting on the main system is transferred to the dynamic vibration absorber, and the force exerted by the dynamic vibration absorber on the main system is equal in magnitude and opposite in direction to the force exerted by the external excitation on the main system, making the main system in a balanced state and reducing the vibration amplitude of the main system. Compared with other traditional vibration damping devices, the dynamic vibration absorber not only has a simple structure and is easy to manufacture, but also has good vibration damping effect.

[0003] Since in practical applications, the magnitude of the external excitation frequency is usually time-varying, and once the parameters of the traditional "spring-mass" structure dynamic vibration absorber are selected, its natural frequency is also determined. When the natural frequency of the dynamic vibration absorber is inconsistent with the excitation frequency, the amplitude of the main system will increase sharply, even causing resonance, and it cannot play a role in vibration damping. Therefore, it is necessary to select an appropriate natural frequency of the vibration absorber for different excitation frequencies to achieve the self-adaptability of the excitation load. The mechanical frequency modulation type dynamic vibration absorber can change its equivalent stiffness by changing its own structural parameters, and then change the natural frequency of the dynamic vibration absorber to adapt to the excitation force at different frequencies and improve the vibration isolation performance of the main system.

[0004] Common methods for changing the stiffness of mechanical frequency modulation type dynamic vibration absorbers include air springs, piezoelectric ceramics, shape memory alloys, etc. Although the air spring dynamic vibration absorber has the advantages of strong load-bearing capacity, good fatigue resistance, and durability, it uses an air pump as a variable stiffness driving device, which requires an additional large redundant mass, increasing the overall mass of the vibration isolation system. The piezoelectric ceramic dynamic vibration absorber has a large stiffness. Relatively speaking, a very heavy oscillator is required. At the same time, the piezoelectric ceramic cannot be stretched and is brittle, so that the amplitude of this dynamic vibration absorber will be very small, limiting the vibration absorption ability and may cause the system to be unstable. Due to the temperature hysteresis nonlinearity of the shape memory alloy variable stiffness dynamic vibration absorber, the stiffness of the dynamic vibration absorber can be adjusted. However, the temperature control of the shape memory alloy is very difficult, increasing the difficulty of stiffness adjustment; moreover, although the natural frequency of the shape memory alloy variable stiffness dynamic vibration absorber can be adjusted, it is discrete. Therefore, continuous change of stiffness cannot be achieved, and the adjustment range of its equivalent stiffness is also relatively narrow. Through the analysis of some of the above dynamic vibration absorbers, it is necessary to design a vibration isolation device that can not only increase the adjustment range of the natural frequency of the dynamic vibration absorber, but also reduce the initial vibration isolation frequency of the main system. Summary of the Invention

[0005] The object of the present invention is to provide a quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber, so as to solve the above-mentioned problems of how to effectively increase the adjustable range of the natural frequency of the dynamic vibration absorber and reduce the starting vibration isolation frequency of the main system. By introducing a negative stiffness structure on the basis of a linear stiffness main system and forming a quasi-zero stiffness vibration isolation main system based on the parallel principle of positive and negative stiffness, and then on the basis of the traditional "spring - mass block" structure, a "spring plate - sliding mass block" structure adaptive adjustable frequency dynamic vibration absorber is proposed to achieve the function of adjustable natural frequency of the dynamic vibration absorber and the effect of reducing the starting vibration isolation frequency of the main system.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber includes a quasi-zero stiffness vibration isolation main system and an adjustable frequency dynamic vibration absorber subsystem.

[0008] The quasi-zero stiffness vibration isolation main system includes a base, a negative stiffness mechanism, a hinged mechanism, a sliding column, an internal hexagonal bolt, a nut, a connecting piece, a damper, a bearing platform, a vertical spring, etc.; the negative stiffness mechanism includes a guide cylinder body, a compression spring and a piston column; the hinged mechanism consists of a fixed hinge, a movable hinge and a bolt; the dynamic vibration absorber subsystem consists of a spring plate, a sliding mass block, a stepping motor, a transmission lead screw, side columns, a sliding table and an acceleration sensor.

[0009] Furthermore, the upper ends of the vertical spring and the damper are connected to the bearing platform, and the lower ends are connected to the base; the vertical spring and the negative stiffness mechanism make the natural vibration frequency of the main system decrease through the parallel principle of positive and negative stiffness; the vertical spring bears the weight of the bearing platform and the dynamic vibration absorber and compresses freely; four symmetric hinged mechanisms are arranged at the bottom of the base; the hinged mechanism is connected to the lower end of the negative stiffness mechanism; the upper end of the negative stiffness mechanism is connected to the sliding column through the hinged mechanism; the hinged mechanism is fixedly connected to the sliding column by means of bolt and nut cooperation; the sliding column can slide on the bearing platform to adjust the starting angle of the negative stiffness structure; the sliding column is fixed to the bearing platform by bolts and connecting pieces.

[0010] Furthermore, the side columns are fixed on the bearing platform; one end of the spring plate is fixed on the side column, and the other end places the sliding mass block; the stepping motor is fixed on the bearing platform; the sliding table slides on the transmission lead screw to change the effective length of the spring plate, thereby changing the natural frequency of the dynamic vibration absorber; the acceleration sensor is attached to the spring plate to detect the natural frequency of the dynamic vibration absorber so as to adjust the output displacement of the stepping motor through a controller and realize the movement of the sliding table on the transmission lead screw.

[0011] A further solution is that the upper and lower ends of the negative stiffness mechanism are connected to the hinge mechanism by a threaded mating connection; the negative stiffness mechanism generates a force by compressing the compression spring inside through a piston rod.

[0012] A further solution is that a chute is provided on the bearing platform, and the sliding column is installed in the chute.

[0013] Compared with the existing technology, the present invention has the following advantages:

[0014] Based on the traditional "spring - mass" vibration absorber structure, the present invention proposes an adjustable - frequency dynamic vibration absorber with a "spring plate - sliding mass" structure. The natural frequency of the dynamic vibration absorber can be changed by adjusting the effective length of the spring plate, and the structure is simple and easy to implement. Moreover, the stiffness adjustment range of the dynamic vibration absorber is large, which can effectively increase the attenuation region of the main system. In addition, by adding four negative stiffness mechanisms to the traditional main system structure, the linear stiffness main system is changed into a quasi - zero stiffness main system, reducing the initial isolation frequency of the vibration isolation system and achieving an ultra - low - frequency vibration isolation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0016] Figure 2 is a schematic diagram of the structure of the negative stiffness mechanism of the present invention;

[0017] Figure 3 is a schematic diagram of the structure of the hinge mechanism of the present invention;

[0018] Figure 4 is a flowchart of the frequency modulation control of the present invention;

[0019] In the figure: 1 - base, 2 - negative stiffness mechanism, 21 - guiding cylinder body, 22 - compression spring, 23 - piston rod, 3 - hinge mechanism, 31 - fixed hinge, 32 - movable hinge, 4 - sliding column, 5 - hexagon socket head cap screw, 6 - nut, 7 - connecting piece, 8 - bolt, 9 - spring plate, 10 - sliding mass, 11 - damper, 12 - bearing platform, 13 - vertical spring, 14 - stepper motor, 15 - transmission lead screw, 16 - side column, 17 - slide table, 18 - acceleration sensor. DETAILED DESCRIPTION OF THE INVENTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] Figure 1As shown in the figure, it is a schematic diagram of the overall structure of a quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber. Specifically, it includes a base 1, a bearing platform 12, a damper 11 and a vertical spring 13 with the lower end connected to the base and the upper end connected to the bearing platform. The vertical spring 13 has a certain compression amount during installation and is used to bear the weight of the bearing platform 12 and freely compress. Four hinge mechanisms 3 are symmetrically arranged around the bottom of the base 1, and the hinge mechanisms 3 are threadedly connected to the lower end of the negative stiffness mechanism 2; the upper end of the negative stiffness mechanism 2 is threadedly connected to the hinge mechanism 3; the hinge mechanism 3 is fixedly connected to the sliding column 4 by means of an internal hexagon bolt 5 and a nut 6; the sliding column 4 can slide on the bearing platform 12 to adjust the starting angle of the negative stiffness structure 2; the sliding column 4 is fixed to the bearing platform 12 through a connecting piece 7 and a bolt 8.

[0022] The side column 16 is fixed on the bearing platform 12; one end of the spring plate 9 is fixed on the side column 16; the stepping motor 14 is fixed on the bearing platform 12; the sliding table 17 slides on the transmission lead screw 15 to change the effective length of the spring plate 9, thereby changing the natural frequency of the dynamic vibration absorber; the acceleration sensor 18 is attached to the spring plate 9 and is used to detect the natural frequency of the dynamic vibration absorber so as to adjust the output displacement of the stepping motor 14 through the controller and realize the movement of the sliding table 17 on the transmission lead screw 15.

[0023] The "spring plate - sliding mass block" structure dynamic vibration absorber is installed on the main system through the side column 16. When there is an external excitation, the external excitation is transmitted from the main system to the side column 16, and then the load is transmitted to the sliding mass block 10 through the spring plate 9. The dynamic force generated by the sliding mass block 10 cancels out the external excitation force acting on the main system, thereby suppressing the vibration response of the main system. The dynamic vibration absorber adjusts the stiffness of the spring plate 9 by changing the distance (i.e., the effective length) between the sliding mass block 10 and the sliding table 17, thereby realizing the adjustment of its own stiffness.

[0024] The working process of the present invention is as follows: As shown in the figure, when no vibration isolation object is placed on the bearing platform 12, the negative stiffness mechanism 2 is in an inclined state; when a vibration isolation object is placed on the bearing platform 12, both the vertical spring 13 and the compression spring 22 inside the negative stiffness mechanism 2 will be compressed, and the position of the sliding column 4 is adjusted to make the main system meet the zero stiffness condition; then the system parameters are adjusted in real time through the acceleration sensor 18 and the control system, so that the natural frequency of the dynamic vibration absorber tracks the frequency of the external load in real time, realizing the self-adaptability of the load, and its control flow chart is as Figure 4 shown.

[0025] The specific control process is as follows: the vibration signals of the main system and the dynamic vibration absorber system are collected in real time through the acceleration sensor 18, and the collected signals are subjected to Fourier transform to obtain the excitation frequency and the natural frequency of the dynamic vibration absorber. A threshold frequency is set, the purpose of which is to allow a certain measurement error in the system. Then, the relationship between the absolute difference between the excitation frequency and the natural frequency of the vibration absorber and the threshold is compared. Through the control system, the frequency signal is analyzed and processed to control the movement of the stepper motor 14, so that the sliding table 17 slides on the transmission lead screw 15 to change the effective length of the spring strip 9, thereby controlling the stiffness of the dynamic vibration absorber and realizing the adjustment of the natural frequency of the dynamic vibration absorber, so that the natural frequency of the dynamic vibration absorber tracks the excitation frequency and is adjusted in real time.

[0026] The above content is the preferred implementation mode of the present invention in combination with specific drawings. The specific implementation of the present invention is not limited by the above implementation mode. It should be noted that improvements or variations can be made without departing from the technical principle of the present invention, and these improvements or variations should be regarded as the protection scope of the present invention.

Claims

1. A quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber, characterized in that: It includes a quasi-zero stiffness vibration isolation main structure and a tunable frequency dynamic absorber; The quasi-zero stiffness vibration isolation main structure includes a base (1), a negative stiffness mechanism (2), a hinged mechanism (3), a sliding column (4), a damper (11), a bearing platform (12), and a vertical spring (13); the tunable frequency dynamic absorber is composed of a spring plate (9), a sliding mass block (10), a stepper motor (14), a transmission lead screw (15), side columns (16), a sliding table (17), and an acceleration sensor (18); The negative stiffness mechanism (2) includes a guide cylinder body (21), a compression spring (22), and a piston column (23); the hinged mechanism (3) is composed of a fixed hinge (31) and a movable hinge (32); four symmetric hinged mechanisms (3) are provided at the bottom of the base (1); the upper end of the negative stiffness mechanism (2) is connected to the sliding column (4) through the hinged mechanism (3), and the lower end is hinged to the base (1); The upper ends of the vertical spring (13) and the damper (11) are fixedly connected to the bearing platform (12), and the lower ends are fixedly connected to the base (1); the vertical spring (13) bears the weight of the bearing platform (12) and the dynamic absorber and compresses freely, and has a certain compression amount when installed; The side columns (16) are fixedly connected above the bearing platform (12); one end of the spring plate (9) is fixedly connected to the side column (16), and the other end places the sliding mass block (10); the acceleration sensor (18) is attached to the spring plate (9); the stepper motor (14) is fixedly connected above the bearing platform (12); the sliding table (17) is slidably connected to the transmission lead screw (15), and it slides along the transmission lead screw (15) to change the effective length of the spring plate (9), thereby realizing the adjustment of its own stiffness; the tunable frequency dynamic absorber further includes a control system that can control the movement of the stepper motor (14) and regulate the sliding of the sliding table (17) on the transmission lead screw (15).

2. The quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber according to claim 1, characterized in that: The sliding column (4) is fixedly connected to the bearing platform (12) below through a bolt (8) and a connecting piece (7); the hinged mechanism (3) is fixedly connected to the sliding column (4) by a combination of an internal hexagonal bolt (5) and a nut (6).

3. The quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber according to claim 1, characterized in that: One end of the compression spring (22) is fixedly connected to the inner bottom of the cylinder body (21), and the other end is fixedly connected to the piston column (23); the fixed hinge (31) and the movable hinge (32) are movably connected by a pin shaft.

4. A quasi-zero stiffness vibration isolation device with a mechanical frequency modulation type dynamic vibration absorber according to claim 1, characterized in that: There are four negative stiffness mechanisms (2), which are symmetrically arranged. Their lower ends are respectively hinged to the base (1) through four symmetric hinged mechanisms provided at the bottom of the base (1), and the upper ends are hinged to the sliding column (4); in view of the fact that the sliding column (4) is fixedly connected to the bearing platform (12), the negative stiffness mechanism (2) is connected in parallel with the vertical spring (13) providing positive stiffness.

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