A magnetorheological vibration isolator with negative stiffness characteristics

Abstract

This invention discloses a magnetorheological vibration isolator with negative stiffness characteristics, comprising a magnetorheological elastomer (MRE), an iron sheet, a circular magnet, a cylindrical central shaft, an electromagnetic coil, upper and lower base plates, an outer sleeve, and a bar magnet. The MRE, iron sheet, and circular magnet form a multi-layered MRE structure, with the circular magnet providing a portion of the initial magnetic field to the MRE. The electromagnetic coil, located between the multi-layered MRE structure and the outer sleeve, can control the magnetic field strength acting on the MRE in real time, thereby controlling the stiffness and damping of the MRE isolator. The bar magnet and magnet brackets form a negative stiffness generating unit, respectively installed on both symmetrical sides of the isolator. This invention introduces negative stiffness characteristics into a semi-active vibration isolator, improving the vibration reduction effect of semi-active control to the level of active control, while also offering good stability and low system cost. This invention can be applied to lateral vibration control in high-speed trains, improving stability and safety during high-speed operation, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of lateral vibration control technology for high-speed trains and regular trains, and specifically to a magnetorheological vibration isolator with negative stiffness characteristics. Background Technology

[0002] As train speeds continue to increase, higher demands are placed on the stability and safety of high-speed trains. During high-speed travel or acceleration, lateral vibrations can rapidly disperse, leading to train instability and severely impacting operational safety. The most fundamental solution is to develop effective new lateral vibration control methods while simultaneously increasing high-speed rail speeds, ensuring both transport efficiency and high-speed stability. However, with further development of high-speed rail technology and increased operating speeds, existing passive bogie suspensions are increasingly inadequate. Currently, active control and semi-active control are two typical methods superior to passive control and suitable for improving the vibration reduction performance of high-speed rail bogies. Active control offers good vibration reduction, but its complexity, poor stability, high power consumption, and high cost significantly limit its widespread use. Semi-active control, with its superior performance, low power consumption, low hardware cost, and better vibration reduction effect than passive control, has received considerable attention in recent years. However, compared to active control, the vibration reduction effect of semi-active control still has significant limitations.

[0003] Research has revealed that the force-displacement relationship curve of an active vibration damping system exhibits significant negative stiffness characteristics during vibration reduction. To further improve the vibration damping performance of semi-active high-speed rail bogies, this invention introduces these negative stiffness characteristics into a magnetorheological vibration isolator, aiming to elevate the vibration damping performance of the semi-active high-speed rail bogie to the level of active vibration damping. The introduction of negative stiffness characteristics saves energy required for active control, reducing system costs. Furthermore, this invention achieves the vibration damping effect of active control while maintaining the advantages of a semi-active system, including high stability, low cost, low power consumption, and high reliability. Summary of the Invention

[0004] The technical problem solved by this invention is to disclose a magnetorheological vibration isolator with negative stiffness characteristics, which solves the following technical problems: First, the introduction of negative stiffness characteristics can generate a "negative stiffness force" that is effective in the full frequency range. This "negative stiffness force" can overcome the limitation of traditional semi-active vibration reduction systems that only have a significant vibration reduction effect near the resonant frequency. Second, this invention can achieve an active control vibration reduction effect, avoiding the shortcomings of active control systems while retaining the advantages of semi-active systems such as high stability, low cost, low power consumption, and high reliability.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A magnetorheological vibration isolator with negative stiffness characteristics includes an upper base plate, an outer sleeve, an upper base plate magnet fixing component, a bar magnet, a cylindrical central shaft, a magnetorheological elastomer, an iron sheet, a circular magnet, a linear slide rail, an L-shaped corner bracket, a lower base plate, a magnet bracket, and an electromagnetic coil. The magnetorheological vibration isolator is characterized by the following: the magnetorheological elastomer, the iron sheet, the circular magnet, and the cylindrical central shaft together form the central shaft portion of the magnetorheological vibration isolator; the electromagnetic coil is located on the periphery of the central shaft portion, providing an electromagnetic field to the magnetorheological elastomer; the magnetorheological vibration isolator uses the central shaft portion, the upper base plate, the outer sleeve, and the lower base plate as a medium to form a loop in the magnetic field generated by the electromagnetic coil; the linear slide rail is used to ensure that the upper and lower base plates can only move laterally; and the bar magnet is used to provide the negative stiffness characteristic of the magnetorheological vibration isolator.

[0007] Furthermore, the two cylindrical central shafts are respectively connected and fixed to the upper and lower base plates. A multi-layer magnetorheological elastomer structure is provided between the two cylindrical central shafts. This multi-layer magnetorheological elastomer structure is composed of 10 layers of magnetorheological elastomer, 10 iron sheets and 2 circular magnets sandwiched together. This multi-layer structure can not only expand the lateral deformation capacity of the single-layer magnetorheological elastomer (MRE) but also improve its longitudinal support capacity.

[0008] Furthermore, circular magnets can provide a permanent magnetic field for the magnetorheological elastomer, giving the resulting multilayer magnetorheological elastomer structure a larger initial stiffness, thereby improving its initial longitudinal support capacity.

[0009] Furthermore, the magnetic field strength acting on the multilayer magnetorheological elastomer structure is the superposition of the permanent magnetic field strength generated by the circular magnet and the electromagnetic field strength generated by the electromagnetic coil. The strength and direction of the electromagnetic field generated by the electromagnetic coil can be controlled by changing the magnitude and direction of the current. When the electromagnetic field generated by the electromagnetic coil is in the same direction as the permanent magnetic field generated by the circular magnet, the current is defined as a positive current. The larger the current, the greater the total magnetic field strength acting on the multilayer magnetorheological elastomer structure, and the greater the stiffness of the magnetorheological vibration isolator. Conversely, when the electromagnetic field generated by the electromagnetic coil is in the opposite direction to the permanent magnetic field generated by the circular magnet, the current is defined as a reverse current. Increasing the current will decrease the total magnetic field strength acting on the multilayer magnetorheological elastomer structure, and the stiffness of the magnetorheological vibration isolator will decrease. Thus, the stiffness of the magnetorheological vibration isolator can be controlled. Furthermore, the negative stiffness characteristic of the magnetorheological vibration isolator is achieved by 12 bar magnets. Due to different application environments, the number of bar magnets in the magnetorheological vibration isolator can also be adjusted according to different needs or design requirements, but the number of bar magnets installed vertically and horizontally must be symmetrical.

[0010] Furthermore, the guide rail of the linear slide rail is connected to the outer sleeve through an L-shaped corner bracket, while the slider of the linear slide rail is connected to the upper base plate, so that the upper and lower base plates can only produce lateral relative displacement.

[0011] Furthermore, the bar magnets are divided into two groups, left and right, with six magnets in each group. These are mounted on symmetrical sides parallel to the lateral movement direction of the upper and lower base plates of the magnetorheological isolator using magnet fixing components on the upper base plate and magnet supports. In other words, the bar magnets are installed on both sides of the lateral movement direction of the magnetorheological isolator. The twelve bar magnets are further divided into upper and lower sections, with six magnets in the upper section and six in the lower section. The upper section of magnets is connected and fixed to the upper base plate using magnet fixing components, while the lower section of magnets is fixed to the outer sleeve using magnet supports. A certain gap is maintained between the upper and lower sections of bar magnets. The magnetic pole directions are parallel to the relative movement direction of the upper and lower base plates of the magnetorheological isolator, and the magnetic pole directions of the upper and lower sections of bar magnets are the same. When the magnetorheological isolator is in the intermediate equilibrium position, the magnetic pole surfaces of the upper and lower sections of bar magnets are on the same plane.

[0012] Furthermore, the device exhibits positive stiffness characteristics when it generates a force opposite to the displacement direction, and negative stiffness characteristics when it generates a force in the same direction as the displacement. The magnetic poles of the upper and lower bar magnets are in the same direction. When the magnetorheological isolator is in its equilibrium position, the magnetic pole surfaces of the upper and lower bar magnets are on the same plane. If the magnetorheological isolator moves laterally to the left, the two sets of magnets, due to their identical magnetic pole directions, will generate a repulsive force to the left. If the magnetorheological isolator moves laterally to the right, the two sets of magnets will generate a repulsive force to the right, thus exhibiting negative stiffness characteristics.

[0013] According to the above technical solution, the dynamic working process of the present invention is as follows: The lower base plate of the magnetorheological isolator is connected and fixed to the component that generates the vibration signal, and the upper base plate is connected and fixed to the component that needs to be isolated. When a lateral vibration excitation signal is transmitted to the lower base plate of the magnetorheological isolator, the upper and lower base plates of the magnetorheological isolator undergo lateral displacement. At this time, the magnetorheological elastomer generates a force opposite to the lateral displacement direction due to its positive stiffness characteristics, and the bar magnet that provides negative stiffness characteristics generates a force in the same direction as the lateral displacement. The force exhibited by the magnetorheological isolator is the resultant force of the magnetorheological elastomer and the bar magnet that provides negative stiffness characteristics. However, since the stiffness of the magnetorheological elastomer can be controlled by changing the current of the electromagnetic coil, the force exhibited by the magnetorheological elastomer when the upper and lower base plates undergo lateral displacement is controllable. That is, the force of the magnetorheological isolator can be controlled in real time by controlling the current of the electromagnetic coil, thereby achieving the effect of vibration isolation.

[0014] The beneficial effects of this invention are:

[0015] (1) This invention is based on magnetorheological semi-active technology, which has strong stability, high reliability, simple structure, low maintenance cost, and can provide controllable damping force without requiring large energy consumption and expensive hardware facilities, thus greatly reducing development costs.

[0016] (2) The combination of the negative stiffness component and the semi-active vibration reduction system achieves the synergistic effect of "negative stiffness force" and controllable damping force. The "negative stiffness force" is equivalent to the active driving force in the active control system, and is effective across the entire frequency range. Combined with the controllable damping force, the vibration reduction performance of this invention can be greatly improved. In addition, the negative stiffness component is composed of permanent magnets, which does not consume any energy and is environmentally friendly and economical.

[0017] (3) By controlling the current supplied to the electromagnetic coil, the present invention can achieve real-time controllable stiffness, which helps to improve the vibration reduction performance of the vibration isolator.

[0018] (4) The vibration reduction effect of the present invention can reach the level of active control, overcoming the limitation of traditional semi-active vibration reduction systems that only have a significant vibration reduction effect near the resonant frequency, and breaking through the technical bottleneck of traditional semi-active vibration reduction systems. At the same time, it avoids the disadvantages of active control systems such as high energy consumption, high cost, and complex structure.

[0019] (5) A circular magnet can provide an initial magnetic field to a magnetorheological elastomer without consuming any energy, which gives the invention a fail-safe characteristic and ensures the stability of the train even when the vibration isolator is de-energized, thus improving the safety of the train. Attached Figure Description

[0020] Figure 1 This is a structural cross-sectional view of an embodiment of the present invention;

[0021] Among them, 1-upper base plate, 2-outer sleeve, 3-upper base plate magnet fixing piece, 4-bar magnet, 5-cylindrical central shaft, 6-magnetorheological elastomer, 7-iron sheet, 8-circular magnet, 9-linear slide rail, 10-L-shaped corner bracket, 11-lower base plate, 12-magnet bracket, 13-electromagnetic coil.

[0022] Figure 2 This is a force-displacement curve of a magnetorheological vibration isolator without a negative stiffness unit and with different currents flowing through the electromagnetic coil.

[0023] Figure 3 Force-displacement curves of a magnetorheological vibration isolator under the condition of adding a negative stiffness unit and when different currents are applied to the electromagnetic coil.

[0024] Figure 4 This is a front view of a 1 / 4 section of the magnetorheological vibration isolator. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0026] like Figure 1 As shown, the magnetorheological vibration isolator with negative stiffness characteristics of the present invention includes an upper base plate 1, an outer sleeve 2, an upper base plate magnet fixing component 3, a bar magnet 4, a cylindrical central shaft 5, a magnetorheological elastomer 6, an iron sheet 7, a circular magnet 8, a linear slide rail 9, an L-shaped corner bracket 10, a lower base plate 11, a magnet bracket 12, an electromagnetic coil 13, etc. The central shaft of the vibration isolator consists of 10 layers of 1mm thick magnetorheological elastomer 6, 13 layers of 1mm thick iron sheet 7, 2 2mm thick circular magnets 8, and 2 cylindrical central shafts 5. This central shaft is located at the very center of the vibration isolator and has a diameter of 35mm. An electromagnetic coil 13 is located on the periphery of this central shaft and has an inner diameter of 55mm. It provides a magnetic field for the magnetorheological elastomer 6. The magnetorheological vibration isolator has an axisymmetric structure. The central shaft, upper base plate 1, outer sleeve 2, and lower base plate 11 serve as the medium, allowing the magnetic field generated by the electromagnetic coil 13 to form a loop. The linear slide rail 9 ensures that the upper and lower base plates can only move laterally. The bar magnet 4 achieves the negative stiffness characteristic of the vibration isolator.

[0027] The principle of variable stiffness in vibration isolators lies in the fact that the magnetic field strength acting on the magnetorheological elastic body 6 is jointly determined by the magnetic field strength generated by the circular magnet 8 and the electromagnetic coil 13. The direction of the superimposed magnetic field is perpendicular to the cylindrical base of the magnetorheological elastic body 6. The magnetic field strength and direction of the electromagnetic coil 13 are controlled by the magnitude and direction of the current flowing through it. When the magnetic field generated by the electromagnetic coil 13 is in the same direction as the magnetic field generated by the circular magnet 8, increasing the current increases the total magnetic field acting on the magnetorheological elastic body 6. Conversely, when the magnetic field generated by the electromagnetic coil 13 is in the opposite direction to the magnetic field generated by the circular magnet 8, increasing the current decreases the total magnetic field acting on the magnetorheological elastic body 6. By controlling the magnitude and direction of the current flowing through the electromagnetic coil 13, the variable stiffness characteristic of the vibration isolator is achieved.

[0028] To ensure good magnetic conductivity, the upper base plate 1, outer sleeve 2, cylindrical central shaft 5, iron sheet 7, and lower base plate 11 of the vibration isolator are all made of low carbon steel. The two cylindrical central shafts are connected to the upper base plate 1 and the lower base plate 11 respectively by screws. A 3mm gap is left between the outer sleeve 2 and the upper base plate 1 to ensure the relative movement of the upper and lower base plates. The diameter of the central shaft part composed of the cylindrical central shaft, magnetorheological elastomer 6, iron sheet 7, and circular magnet 8 is 35mm, the inner diameter of the electromagnetic coil 13 is 55mm, and the maximum relative displacement of the left and right sides of the upper and lower base plates is 10mm. The electromagnetic coil 13 is coaxial with the central shaft part and is fixed to the lower base plate 11.

[0029] The electromagnetic coil 13 is a ring-shaped coil made of copper enameled wire with a diameter of 0.5 mm. It is used to generate a controllable axial magnetic field. By changing the magnitude and direction of the current, the stiffness of the vibration isolator can be controlled.

[0030] The magnetorheological elastomer 6 is formed by mixing iron powder, silicone and silicone oil in a certain proportion and then curing. The magnetorheological elastomer used in this invention is a circular sheet with a diameter of 35 mm and a thickness of 1 mm. The magnetorheological elastomer 6 and the iron sheet 7 are bonded together with silicone, and two circular magnets 8 are added in the middle to provide a certain initial magnetic field for the magnetorheological elastomer 6, so that the vibration isolator has a large initial stiffness even when no current is applied.

[0031] The negative stiffness characteristic of the vibration isolator is achieved by multiple bar magnets 4. Half of the magnets are connected and fixed to the upper base plate 1 via the upper base plate magnet fixing member 3, and the other half of the magnets are fixed to the outer sleeve 2 via the magnet bracket 12. Preferably, the bar magnets providing the negative stiffness characteristic are divided into two groups (a total of 12 magnets), which are installed on the left and right sides of the magnetorheological vibration isolator, respectively, and the two groups of magnets are symmetrically distributed. Each group of bar magnets is further divided into upper and lower parts (6 magnets per group, 3 magnets in the upper part and 3 magnets in the lower part). Half of the magnets, namely the upper part of the two groups of magnets (a total of 6 magnets), are connected and fixed to the upper base plate 1 via the upper base plate magnet fixing member 3, and the other half of the magnets, namely the lower part of the two groups of magnets (a total of 6 magnets), are fixed to the outer sleeve 2 via the magnet bracket 12. A certain gap is maintained between the upper and lower magnets, and the magnetic poles are in the same direction. In order to avoid the magnetic field generated by the bar magnet 4 that provides negative stiffness and the magnetic field generated by the electromagnetic coil 13 from interfering with each other, the materials of the upper base plate magnet fixing part 3 and the magnet bracket 12 are both made of non-magnetic aluminum.

[0032] The linear slide rail 9 of the vibration isolator consists of two parts: a slider and a guide rail. The guide rail is connected to the outer sleeve 2 through an L-shaped corner bracket 10, while the slider of the linear slide rail is connected to the upper base plate 1, so that the upper and lower base plates can only produce lateral relative displacement.

[0033] In this invention, the bar magnet 4, the linear guide rail 9, and the magnet support 12 constitute a negative stiffness generating unit, as shown in the attached diagram. Figure 4 As shown, they are installed symmetrically on both sides of the vibration isolator. This invention introduces negative stiffness characteristics into the semi-active vibration isolator, which can improve the vibration reduction effect of semi-active control to the level of active control, and has good stability and low system cost.

[0034] Without adding a negative stiffness element, different currents are applied to the electromagnetic coil 13 of the magnetorheological isolator. The force-displacement curves of the magnetorheological isolator are shown below. Figure 2 As shown, it can be seen that as the applied positive current gradually increases, the slope of the force-displacement curve also gradually increases. Therefore, the stiffness of the magnetorheological isolator can be controlled by adjusting the magnitude and direction of the current applied to the electromagnetic coil 13. With a negative stiffness unit, different currents are applied to the electromagnetic coil 13 of the magnetorheological isolator, and the force-displacement curves of the isolator are shown below. Figure 3 As shown, similar to the case without negative stiffness, the variable stiffness characteristic of the MRE isolator can be achieved by controlling the magnitude and direction of the applied electromagnetic coil current. However, the difference is that when there is no relative displacement between the upper and lower base plates of the MRE isolator, the negative stiffness provided by the two sets of bar magnets 4 reaches its maximum value. As the relative displacement between the upper and lower base plates of the MRE isolator increases, the negative stiffness provided by the bar magnets 4 decreases until the interaction between the bar magnets disappears, and the negative stiffness also disappears. However, due to the existence of negative stiffness, the total stiffness of the MRE isolator is reduced, making it as close to zero stiffness as possible, thereby increasing the adjustable stiffness range and improving the vibration control effect, making its control effect comparable to active control.

[0035] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A magnetorheological vibration isolator with negative stiffness characteristics, comprising an upper base plate (1), an outer sleeve (2), an upper base plate magnet fixing component (3), a bar magnet (4), a cylindrical central shaft (5), a magnetorheological elastomer (6), an iron sheet (7), a circular magnet (8), a linear slide rail (9), an L-shaped corner bracket (10), a lower base plate (11), a magnet bracket (12), and an electromagnetic coil (13), characterized in that: The magnetorheological elastomer (6), iron sheet (7), circular magnet (8), and cylindrical central shaft (5) together form the central shaft part of the magnetorheological vibration isolator. The electromagnetic coil (13) is located on the periphery of the central shaft part and provides an electromagnetic field for the magnetorheological elastomer (6). The magnetorheological vibration isolator uses the central shaft part, upper base plate (1), outer sleeve (2), and lower base plate (11) as a medium to form a loop in the magnetic field generated by the electromagnetic coil (13). The linear slide rail (9) is used to ensure that the upper and lower base plates can only move laterally. The bar magnet (4) is used to provide the negative stiffness characteristics of the magnetorheological vibration isolator. The bar magnet (4) is divided into upper and lower parts, with a gap between the upper and lower parts of the bar magnet (4). The magnetic pole direction is parallel to the relative motion direction of the upper and lower base plates of the magnetorheological vibration isolator, and the magnetic pole directions of the upper and lower parts of the bar magnet (4) are the same. When the magnetorheological vibration isolator is in the middle equilibrium position, the magnetic pole surface of the upper part of the bar magnet (4) and the magnetic pole surface of the lower part of the bar magnet (4) are on the same plane. The two cylindrical central shafts (5) are respectively connected and fixed to the upper and lower base plates, and a multilayer magnetorheological elastomer structure is provided between the two cylindrical central shafts (5).

2. A magnetorheological vibration isolator with negative stiffness characteristics according to claim 1, characterized in that: The multilayer magnetorheological elastomer structure is composed of 10 layers of magnetorheological elastomer (6), 10 layers of iron sheet (7) and 2 circular magnets (8) sandwiched together.

3. A magnetorheological vibration isolator with negative stiffness characteristics according to claim 1, characterized in that: A circular magnet (8) is used to provide a permanent magnetic field for the magnetorheological elastomer (6).

4. A magnetorheological vibration isolator with negative stiffness characteristics according to claim 2, characterized in that: The magnetic field strength acting on the multilayer magnetorheological elastomer structure is the superposition of the permanent magnetic field strength generated by the circular magnet (8) and the electromagnetic field strength generated by the electromagnetic coil (13). The strength and direction of the electromagnetic field generated by the electromagnetic coil (13) can be controlled by changing the magnitude and direction of the current. When the electromagnetic field generated by the electromagnetic coil (13) is in the same direction as the permanent magnetic field generated by the circular magnet (8), the current is defined as the positive current. The larger the current, the greater the total magnetic field strength acting on the multilayer magnetorheological elastomer structure, and the greater the stiffness of the magnetorheological vibration isolator. Conversely, when the electromagnetic field generated by the electromagnetic coil (13) is in the opposite direction to the permanent magnetic field generated by the circular magnet (8), the current is defined as the reverse current. Increasing the current will decrease the total magnetic field strength acting on the multilayer magnetorheological elastomer structure, and the stiffness of the magnetorheological vibration isolator will decrease.

5. A magnetorheological vibration isolator with negative stiffness characteristics according to claim 1, characterized in that: The negative stiffness characteristic of the magnetorheological vibration isolator is achieved by 12 bar magnets (4); the number of bar magnets installed on the top, bottom, left and right sides is symmetrical.

6. A magnetorheological vibration isolator with negative stiffness characteristics according to claim 1, characterized in that: The guide rail of the linear slide rail (9) is connected to the outer sleeve (2) through the L-shaped corner bracket (10), and the slider of the linear slide rail (9) is connected to the upper base plate (1), so that the upper and lower base plates can only produce lateral relative displacement.

7. A magnetorheological vibration isolator with negative stiffness characteristics according to claim 1, characterized in that: There are 12 bar magnets (4) in total, divided into two groups of 6 each. They are installed on the symmetrical sides parallel to the lateral movement direction of the upper and lower base plates of the magnetorheological vibration isolator by means of the upper base plate magnet fixing part (3) and the magnet bracket (12). That is, the bar magnets (4) are installed on both sides of the lateral movement direction of the magnetorheological vibration isolator. The 12 bar magnets (4) are divided into an upper part of 6 magnets and a lower part of 6 magnets. The upper part of the magnets is connected and fixed to the upper base plate (1) by the upper base plate magnet fixing part (3), and the lower part of the magnets is fixed to the outer sleeve (2) by the magnet bracket (12).

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