Active control particle impact damper based on magnetic fluid suspension properties

Abstract

Active control particle collision damper based on magnetic liquid suspension characteristics belongs to the field of vibration control. It successfully solves the problem that the existing particle collision damper cannot be applied to low-frequency vibration and weightless environment, and the active control effect is insufficient. The damper includes a sphere (1), a magnetic liquid (2), a lower magnetic field source (3), a shell (4), a left electromagnet (5), an upper magnetic field source (6) and a right electromagnet (7). When the external vibration occurs, the sphere (1) moves and collides in the shell (4), generating fluid viscous damping and collision damping to absorb energy. In addition, the left electromagnet (5) and the right electromagnet (7) can alternately excite the magnetic liquid (2) in the shell (4) according to the vibration condition, change the suspension force of the magnetic liquid (2), improve the response speed of the sphere (1) to the vibration, and achieve active control of the vibration.

Description

Technical Field

[0001] This invention belongs to the field of vibration control in mechanical engineering (including machines, mechanisms and various parts under gravity and weightlessness environments). Background Technology

[0002] Particle collision dampers are dampers that dissipate vibrational energy through collisions between particles under external vibration excitation. They are applicable to high vibration frequencies and have advantages such as simple structure and long lifespan. However, existing particle collision dampers are mostly passive damping with a narrow damping bandwidth, often only effective at specific frequencies. Furthermore, due to the high friction between solid particles, they cannot address low-to-mid-frequency vibrations. Their damping effect is poor for vibrations below 1000Hz, and for vibrations below 100Hz or even lower frequencies, existing particle collision dampers are essentially ineffective. In addition, current particle dampers rely on gravity to cause particles to accumulate in the shell and generate friction. In a weightless environment, the particles will be in a free-floating state, unable to generate effective collisions, leading to failure.

[0003] To improve the collision probability between particles and the vibration reduction efficiency of particle collision dampers, methods such as injecting a suitable amount of viscous liquid into the container or combining multiple particle collision dampers are commonly used. For example, in Reference 1 (patent application CN106930425 B), the particles are designed as a nested spherical structure connected by springs, and the viscous liquid is used to increase the collision probability between particles. However, the ratio of air to particles inside the nested sphere needs to be properly adjusted to ensure the sphere's suspension, increasing the manufacturing difficulty of the particle damper. Furthermore, the use of springs limits the damper's lifespan. In addition, this design results in the equivalent density of the entire nested sphere being the same as the density of the viscous liquid, making it impossible to generate effective relative motion between the nested sphere and the viscous liquid. Finally, this design is significantly affected by gravity. In space, due to the absence of gravity, the entire nested sphere and its internal particles are in a free-floating state, unable to undergo effective mutual collisions under vibration. In a ground-based environment, gravity causes the particles inside the nested spheres to completely accumulate together. Vibrational energy can only generate movement by overcoming the solid friction between the particles, thus resulting in poor vibration suppression for low and mid-frequency vibrations. However, as described in Reference 2 (patent application CN 114962514 B), the sphere is suspended in a cavity filled with magnetic fluid and equipped with an elastic cushion under the influence of an external magnetic field. This invention can solve the problem that traditional magnetic fluid dampers cannot be applied to vibration environments above 100Hz. However, this damper contains only one sphere, and collision damping only occurs between the copper sphere and the cushion inside the cavity, resulting in very limited damping force. As the vibration frequency increases, the damping force of this damper will be insufficient. Furthermore, the sphere in this damper is only constrained by the levitation force of the magnetic fluid, resulting in a fixed suspension height and no possibility of adjustment according to vibration conditions.

[0004] Another way is to introduce semi-active or active control mode in the particle damper, such as document 3 (patent application number CN107339356A), the particle damping material is filled into a vibration isolation device, and the magnetic field is generated by the external coil, and the eddy current is generated with the movement of the particles to increase the loss of vibration energy. Although this method introduces eddy current damping, it does not change the force of the particles, and the particles are still in the form of accumulation under the condition of gravity. Therefore, it cannot solve the problem that the particles float freely in the weightless environment and the friction between the particles is too large, resulting in low-frequency vibration insensitive. Document 4 (patent application number CN106402239A), a variable unit capable of changing the stiffness, such as magneto-rheological elastomer or spring, is added to the particle damper, and an electromagnet is used to excite the ferromagnetic particle damping to control the stiffness and damping. This method can attract particles by electromagnetic field and produce magnetic attraction force, which can avoid the failure caused by weightlessness to a certain extent. However, after the particles are attracted by the magnetic force, they will all collide and accumulate together, resulting in too large friction between the particles, which leads to the problem that the particles are not sensitive to low-frequency vibration.

[0005] Therefore, it is urgent to redesign and improve the structure of particle collision damping, and to make the particles respond quickly to external vibration through active control, so that they can not only be applied in high-frequency vibration occasions, but also have very good effect in low-frequency vibration occasions, and do not fail in weightless environment. SUMMARY

[0006] The technical problem this invention aims to solve is that particle collision dampers are ineffective for vibrations above 1000Hz due to the high friction between solid particles, and are even less suitable for low-to-medium frequency vibrations below 100Hz. Furthermore, in a weightless environment, the particles will be in a free-floating state, unable to generate effective collisions, and face failure. Even active or semi-active control methods cannot effectively solve this problem. This invention provides an active control particle collision damper based on the suspension characteristics of magnetic liquids. Utilizing the levitation force generated by the magnetic liquid under a non-uniform magnetic field, multiple spheres made of non-magnetic materials are suspended inside a shell, reducing the solid friction between the spheres and making the spheres highly sensitive to inertial forces. When vibration occurs, the spheres move and collide within the magnetic liquid, thereby generating liquid viscous damping and particle collision damping. This provides excellent vibration reduction performance for both low-frequency vibrations of only a few hertz and high-frequency vibrations of thousands of hertz. Moreover, the constraint of this levitation force on the spheres remains effective even in a weightless environment, preventing the problem of free-floating failure. Furthermore, when the energy dissipation rate of particle collisions or the sensitivity to inertial forces cannot meet the vibration reduction requirements, the electromagnet on the outside of the shell is activated to change the magnetic field inside the shell, thereby changing the levitation force of the magnetic liquid. This increases the levitation force in the direction of the external vibration displacement and decreases the levitation force in the opposite direction, forcing the spheres inside the shell to move and gather in the opposite direction of the vibration. In this process, liquid viscous damping and particle collision damping are generated, thereby reducing vibration.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] The damper includes: a sphere, a magnetic fluid, a lower magnetic field source, a housing, a left electromagnet, an upper magnetic field source, and a right electromagnet.

[0009] All spheres are inserted into the shell to form particle damping. The shell is then filled with a magnetic fluid and sealed. A lower magnetic field source is fixedly installed at the bottom of the outer side of the shell, and an upper magnetic field source is fixedly installed at the top of the outer side of the shell to form a confined magnetic field.

[0010] The spheres are made of non-magnetic metal with a density greater than that of the magnetic liquid. The spheres can be solid or hollow non-magnetic metal. However, if hollow, the equivalent density of the sphere must also be greater than that of the magnetic liquid. The outer diameter of the spheres is greater than or equal to 1 mm, and the volumetric filling rate within the shell is 10-90%. Depending on the external vibration conditions, the spheres can be the same or different. The number of spheres must be greater than one, i.e., at least two, to ensure that the spheres collide with each other after vibration occurs, generating particle collision damping.

[0011] The volume filling rate of the magnetic liquid in the shell is 10% to 90%. When applied in the gravity environment, the volume of the magnetic liquid and the spheres can completely fill the inner cavity of the shell or partially fill the inner cavity of the shell. In addition, in the gravity environment, when the total volume of the magnetic liquid and the spheres accounts for 40% to 60% of the volume of the inner cavity of the shell, with the generation of vibration and the change of the magnetic field, the liquid surface of the magnetic liquid will appear to be inclined, so that the movement between the spheres is more rapid and the collision is more violent. At this time, the active control effect reaches the maximum value. However, when applied in the weightless environment, the volume of the magnetic liquid and the spheres must completely fill the inner cavity of the shell and cannot have a cavity.

[0012] The shell is a non-magnetic metal and can be made of copper and non-magnetic steel. The shape of the shell can be a cylinder, a cuboid or a square.

[0013] The lower magnetic field source and the upper magnetic field source are both permanent magnets and can be made of neodymium iron boron or samarium cobalt permanent magnet materials according to the temperature environment. The permanent magnets can be spliced or can be a single piece. When applied on the ground, the upper magnetic field source can be removed and only the lower magnetic field source is selected. However, in the weightless environment, the lower magnetic field source and the upper magnetic field source must be installed. The outer dimensions of the lower magnetic field source and the upper magnetic field source must be greater than or equal to the inner cavity size of the shell. The upper and lower magnetic field sources are used to provide an initial non-uniform external magnetic field to generate a vertical gradient magnetic suspension force in the magnetic liquid, so that the spheres are suspended in the magnetic liquid. The vibration direction is parallel to the top and bottom planes of the shell. The magnetic poles of the lower magnetic field source and the upper magnetic field source adopt the same pole repulsion mode, and the magnetic pole direction is perpendicular to the plane where the vibration is located and parallel to the normal direction of the top and bottom of the shell. That is, the upper surface of the lower magnetic field source is N pole and the lower surface of the upper magnetic field source is also N pole; or the upper surface of the lower magnetic field source is S pole and the lower surface of the upper magnetic field source is also S pole.

[0014] The left electromagnet and the right electromagnet are the same in size and shape. The left electromagnet and the right electromagnet cannot be energized at the same time. After the direction of the vibration displacement changes, the electromagnet to which the vibration displacement vector points is energized and the electromagnet away from the vibration displacement vector is de-energized, so that the magnetic suspension forces of the magnetic liquid at both ends of the shell are different. After energization, the magnetic poles of the left electromagnet and the right electromagnet close to the shell wall surface adopt the opposite magnetic pole mode to the lower magnetic field source and the upper magnetic field source, attract each other, and the magnetization direction is parallel to the plane where the vibration is located and perpendicular to the normal direction of the shell side wall surface, so that the magnetic field gradient of the electromagnet in the shell part reaches the maximum value, and then the difference between the magnetic suspension forces of the magnetic liquid at both ends of the shell reaches the maximum value. Of course, the left electromagnet and the right electromagnet can also adopt the same magnetic pole mode of repulsion with the lower magnetic field source and the upper magnetic field source. Although the magnetic field gradient of the electromagnet in the shell part can still be increased, it cannot reach the maximum value.

[0015] The damper can only be applied to the case where the vibration direction of the outside world is parallel to the bottom surface of the shell. The left electromagnet and the right electromagnet are designed in the form of winding coils outside the magnetically conductive core.

[0016] The present application has the following advantages compared with the prior art: (1) the external magnetic field provided by the lower magnetic field source and the upper magnetic field source makes all the balls suspended in the magnetic liquid, reduces the friction between the balls, and the size of the balls can be different, and the suspension height is also different, making the balls more sensitive and diverse to external vibration, not only can be applied to vibration with frequency of several hundred or even thousands of hertz, but also can be applied to vibration with frequency below 100 Hz; (2) the balls are made of non-magnetic metal, so they are subjected to the magnetic suspension force of the magnetic liquid. By changing the size of the balls, the suspension position of the balls can be controlled at the beginning of the design according to the vibration form, and then the probability of collision between the balls and the size of the collision damping can be adjusted. In addition, it is no longer limited by gravity and can still be applied in a weightless environment; (3) the equivalent density of the balls is greater than the density of the magnetic liquid, when the external vibration occurs, the balls and the magnetic liquid will move relatively, thereby driving the magnetic liquid to flow and generating additional magnetic liquid damping to consume vibration energy, which is very beneficial to low-frequency vibration below 10 Hz; (4) the left electromagnet and the right electromagnet are energized to generate a magnetic field according to the external vibration. Since the magnetic pole direction of the left electromagnet and the right electromagnet after energization is opposite to that of the lower magnetic field source and the upper magnetic field source, it is in the attraction mode, which can make the suspension force inside the magnetic liquid at the corresponding position increase greatly after energization, so that the balls can quickly move and gather in the opposite direction of the vibration displacement, and consume vibration energy, achieving active control of vibration, and increasing the stiffness and damping of the vibration system. BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 Schematic diagram of the active control particle collision damper based on the suspension characteristics of the magnetic liquid;

[0018] Fig. 2 Schematic diagram of the active control particle collision damper based on the suspension characteristics of the magnetic liquid when the balls are hollow;

[0019] Fig. 3 Schematic diagram of the active control particle collision damper based on the suspension characteristics of the magnetic liquid when the magnetic liquid does not fill the shell;

[0020] In the figure: ball 1, magnetic liquid 2, lower magnetic field source 3, shell 4, left electromagnet 5, upper magnetic field source 6 and right electromagnet 7. DETAILED DESCRIPTION

[0021] The present application is further described with the drawings as the specific embodiment:

[0022] Active control particle collision damper based on magnetic fluid suspension characteristics, such as Figs. 1-3 The damper comprises a sphere 1, a magnetic fluid 2, a lower magnetic field source 3, a shell 4, a left electromagnet 5, an upper magnetic field source 6 and a right electromagnet 7.

[0023] The sphere 1 is entirely filled in the shell 4 to form a particle collision damper. The sphere 1 is made of non-magnetic metal and has a density greater than that of the magnetic fluid 2. Meanwhile, the sphere 1 can be solid non-magnetic metal or hollow non-magnetic metal. However, if it is hollow, the equivalent density of the sphere 1 must be greater than that of the magnetic fluid 2 and it can be welded in a split manner. The outer diameter of the sphere is greater than or equal to 1 mm and the volume filling rate in the shell is 10-90%. The number of spheres must be greater than 1, i.e. at least 2, to ensure that the spheres collide with each other after vibration and generate particle collision damping. The sizes of all spheres 1 can be the same or different. Large-sized spheres 1 are more sensitive to low-frequency vibration, while small-sized spheres 1 have greater damping force for high-frequency vibration. The selection is made according to the specific vibration condition. If the vibration frequency is relatively single, when the vibration frequency of the object to be damped is only several tens of hertz, the number of spheres 1 should be reduced and preferably controlled within 10, while the size of the sphere 1 is increased. If the vibration frequency is relatively single and greater than 100 Hz, the number of spheres 1 should be increased with the increase of the vibration frequency, while the size of the sphere 1 is reduced. If the vibration frequency range of the object to be damped is large, large-sized spheres 1 and small-sized spheres 1 can be mixed in a certain proportion according to the volume fraction.

[0024] The volume filling rate of the magnetic fluid 2 in the shell 4 is 10-90%. The volumes of the magnetic fluid 2 and the sphere 1 can completely fill the inner cavity of the shell 4 or partially fill the inner cavity of the shell 4, which is selected according to the external vibration condition. Therefore, there are two substances of the sphere 1 and the magnetic fluid 2 or three substances of the sphere 1, air and the magnetic fluid 2 in the shell 4. For example, when the filling rate of the sphere 1 in the shell 4 is 20% and the filling rate of the magnetic fluid 2 in the shell 4 is 70%, 10% of the volume in the shell 4 is air. In addition, under the gravity environment, when the total volume of the magnetic fluid 2 and the sphere 1 accounts for 40-60% of the inner cavity volume of the shell 4, with the generation of vibration and the change of the magnetic field, the liquid surface of the magnetic fluid 2 will tilt, making the movement of the spheres 1 more rapid and the collision more violent. At this time, the active control effect reaches the maximum. However, when applied in the weightless environment, the volumes of the magnetic fluid 2 and the sphere 1 must completely fill the inner cavity of the shell 4 and cannot have a cavity, otherwise the spheres 1 may gather at the cavity position and no longer move with the vibration.

[0025] The shell 4 is non-magnetic metal, which can be selected from copper and non-magnetic steel. The shape of the shell 4 can be cylindrical, cuboid or square.

[0026] The lower magnetic field source 3 and the upper magnetic field source 6 are both composed of permanent magnets. They can be spliced by multiple permanent magnets or single permanent magnet. In ground environment application, the upper magnetic field source 6 can be removed and only the lower magnetic field source 3 is selected. But in weightless environment, the lower magnetic field source 3 and the upper magnetic field source 6 must be installed. The external size of the lower magnetic field source 3 and the upper magnetic field source 6 must be greater than or equal to the internal cavity size of the shell 4. The upper and lower magnetic field sources are used to provide an initial non-uniform external magnetic field, so that the vertical gradient magnetic suspension force is generated inside the magnetic liquid 2, and the sphere 1 is suspended in the magnetic liquid 2. The vibration direction is parallel to the top and bottom planes of the shell 4. The magnetic poles of the lower magnetic field source 3 and the upper magnetic field source 6 adopt the same pole repulsion mode, and the magnetic pole direction is perpendicular to the plane where the vibration is located, and parallel to the normal direction of the top and bottom of the shell 4. The upper and lower magnetic field sources can also be designed by using magnetic metal for magnetic circuit design, or by arranging permanent magnets with different magnetization directions to generate a strong gradient magnetic field in the shell 4.

[0027] The left electromagnet 5 and the right electromagnet 6 are completely the same in size and shape. After energization, the left electromagnet 5 and the right electromagnet 6 adopt the same pole mode as the lower magnetic field source 3 and the upper magnetic field source 6, and the magnetization direction is parallel to the plane where the vibration is located, and perpendicular to the normal direction of the side wall of the shell 4. Therefore, the damper can only be applied to the case where the external vibration direction is parallel to the bottom surface of the shell 4. The design of the left electromagnet 5 and the right electromagnet 6 is preferably selected to be wound around the outside of the magnetic core.

[0028] After vibration occurs, because the density of sphere 1 is greater than that of magnetic fluid 2, all spheres 1 will move inside magnetic fluid 2 under the influence of its viscosity and inertial force, creating a displacement difference with the shell 4, and converging in the opposite direction of vibration. During this process, all spheres 1 not only generate viscous damping force with magnetic fluid 2, but also collide with each other and even with the wall of shell 4, generating particle collision damping. The effect of the viscous damping force of magnetic fluid 2 weakens with increasing vibration frequency, while the effect of particle collision damping increases with increasing vibration frequency. Therefore, at low frequencies, such as below 10Hz, energy consumption is mainly due to the fluid friction between magnetic fluid 2 and spheres 1. At vibrations below 100Hz, some collisions will occur between spheres 1, generating particle collision damping. At this time, the energy consumption of the damper is mainly due to the fluid friction between magnetic fluid 2 and spheres 1, and some particle collision friction between spheres 1. At frequencies of several hundred or even thousands of hertz, the fluid friction between the magnetic fluid 2 and the sphere 1 is very small, but the collisions between the spheres 1 will be very frequent, and the energy consumption will mainly be due to the damping of particle collisions between the spheres 1.

[0029] If the external vibration sensor detects insufficient vibration suppression by acquiring displacement or acceleration signals, the active system module will be activated. The controller will energize the left electromagnet 5 and the right electromagnet 6. When the magnetic fluid 2 fills the entire cavity of the housing 4, if the vibration displacement direction is towards the right electromagnet 6, the right electromagnet 6 will be activated and the left electromagnet 5 will be deactivated. This increases the magnetic fluid levitation force at the right end of the housing 4 and decreases it at the left end, thereby driving all the spheres 1 to move and converge towards the left end of the housing 4, reducing vibration energy. Conversely, if the vibration displacement direction is towards the left electromagnet 5, the left electromagnet 5 will be activated and the right electromagnet 6 will be deactivated. This increases the magnetic fluid levitation force at the left end of the housing 4 and decreases it at the right end, thereby driving all the spheres 1 to move and converge towards the right end of the housing 4, reducing vibration energy. The strength of the magnetic field generated by the left electromagnet 5 and the right electromagnet 6 can be adjusted by the applied current, which ranges from 0.5A to 5A.

[0030] If the magnetic liquid 2 inside the shell 4 does not completely fill the cavity, the movement of the sphere 1 depends more on the magnetic attraction generated by the left electromagnet 5 and the right electromagnet 6, causing the liquid surface of the magnetic liquid 2 to tilt, driving the sphere 1 to move and gather in the opposite direction of the vibration displacement. The starting and stopping sequence of the left electromagnet 5 and the right electromagnet 6 is the same as when the magnetic liquid 2 fills the shell 4.

[0031] Magnetic fluid 2 should be selected from kerosene-based, engine oil-based, and ester-based magnetic fluids, with a viscosity not exceeding 500 mPa·s. It should not be replaced by similar magnetic fluids, such as magnetorheological fluids.

[0032] The above is only one embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the active control particle collision damper based on the suspension characteristics of the magnetic liquid can be modified according to engineering conditions, including but not limited to the size of the damper, the volume of the ball, the shape of the shell, the selection of materials, the installation position, etc.

Claims

1. An actively controlled particle impact damper based on the suspension properties of a magnetic fluid, characterized by: The damper comprises a ball (1), a magnetic liquid (2), a lower magnetic field source (3), a shell (4), a left electromagnet (5), an upper magnetic field source (6) and a right electromagnet (7); The ball (1) is fully loaded into the shell (4) to form a particle collision damping; the magnetic liquid (2) is filled into the shell (4); the lower magnetic field source (3) is fixedly installed at the bottom of the shell (4), and the upper magnetic field source (6) is fixedly installed at the top of the shell (4) to form a constraint magnetic field; The left electromagnet (5) is fixedly installed at the left side wall of the shell (4), and the right electromagnet (7) is fixedly installed at the right side wall of the shell (4) to form an excitation magnetic field; The left electromagnet (5) and the right electromagnet (7) cannot be energized at the same time, after the direction of the vibration displacement changes, the electromagnet in the direction of the vibration displacement vector is energized, and the electromagnet away from the vibration displacement vector is de-energized; after energization, the left electromagnet (5) and the right electromagnet (7) are close to the magnetic poles of the side wall of the shell (4), adopt the magnetic pole mode opposite to the lower magnetic field source (3) and the upper magnetic field source (6), attract each other, and the magnetization direction is parallel to the plane where the vibration is located and perpendicular to the normal direction of the side wall of the shell (4).

2. The active control particle impact damper based on the magnetic liquid suspension characteristics according to claim 1, characterized in that: The number of the ball (1) is greater than 1, the material is a non-magnetic metal, and the density is greater than the density of the magnetic liquid (2).

3. The active control particle impact damper based on the magnetic liquid suspension characteristics according to claim 1, characterized in that: The shell (4) is a non-magnetic metal, the lower magnetic field source (3) and the upper magnetic field source (6) are the same in size and shape, and are made of permanent magnets; the magnetic poles of the lower magnetic field source (3) and the upper magnetic field source (6) adopt the same pole repulsion mode, and the magnetic pole direction is perpendicular to the plane where the vibration is located and parallel to the normal direction of the top and bottom of the shell (4); that is, the upper surface of the lower magnetic field source (3) is N-pole, and the lower surface of the upper magnetic field source (6) is also N-pole; or the upper surface of the lower magnetic field source (3) is S-pole, and the lower surface of the upper magnetic field source (6) is also S-pole.

4. The active control particle impact damper based on the magnetic fluid suspension characteristics according to claim 1, characterized in that: The left electromagnet (5) and the right electromagnet (7) are the same in size and shape.

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