Load adaptive electromagnetic quasi-zero stiffness vibration isolation device and method

Abstract

The application discloses a load self-adaptive electromagnetic quasi-zero stiffness vibration isolation device and method, which comprises a vibration isolator frame, a linear motion assembly arranged in the vibration isolator frame, a negative stiffness structure assembly, a positive stiffness structure assembly and a circuit control module connected with the linear motion assembly, the negative stiffness structure assembly and the positive stiffness structure assembly respectively, wherein the linear motion assembly is arranged in the central axis direction of the vibration isolator frame, the negative stiffness structure assembly without a bistable state characteristic is sequentially connected with the positive stiffness structure assembly with a nonlinear gradual hardening characteristic and connected with the linear motion assembly. The quasi-zero stiffness characteristic is realized by modulating the negative stiffness with the nonlinear gradual hardening positive stiffness. The electromagnetic negative stiffness coil and the electromagnetic positive stiffness coil are connected in series, and the rated load of the vibration isolator can be changed without the quasi-zero stiffness characteristic only by adjusting the current of the coil. The rated load self-adaptation and real-time adjustment of the quasi-zero stiffness vibration isolator are realized by cooperating with a sensor and a microprocessor.

Description

Technical Field

[0001] This invention relates to a technology in the field of vibration isolation, specifically a load-adaptive electromagnetic quasi-zero stiffness vibration isolation device and method. Background Technology

[0002] Traditional passive vibration isolators are linear systems, constrained by the contradictory relationship between load-bearing capacity and natural frequency, making them difficult to effectively isolate low-frequency vibrations. Quasi-zero stiffness isolators are a typical nonlinear stiffness isolation system. Based on the idea of ​​negative stiffness offsetting positive stiffness, they can achieve high static stiffness and near-zero dynamic stiffness characteristics, possessing a low natural frequency near the equilibrium position, thus exhibiting excellent low-frequency vibration isolation performance. While the nonlinearity of stiffness endows quasi-zero stiffness isolators with excellent low-frequency vibration isolation performance, it also creates a coupling relationship between stiffness and displacement, making them extremely sensitive to load. Specifically, when the load on the isolator changes, the static equilibrium position shifts accordingly, causing the quasi-zero stiffness isolator to lose its near-zero dynamic stiffness characteristics, resulting in a deterioration in its vibration isolation performance. Traditional methods for achieving quasi-zero stiffness involve connecting a bistable negative stiffness structure in parallel with a linear spring. The bistable negative stiffness neutralizes the linear positive stiffness, and the load is borne by the linear spring. The rated load of the quasi-zero stiffness isolator can be changed by adjusting the compression of the linear spring. This rated load adjustment method requires manual adjustment or mechanical linear feed structure drive, which is complex, has poor real-time performance, and requires a high-power linear feed structure when the load is large, resulting in high cost. Improved technologies also achieve rated load adjustment of the quasi-zero stiffness isolator by adjusting the positive stiffness of the airbag and the negative stiffness of the electromagnetic coil. However, the airbag pressure and the electromagnetic coil current need to be controlled separately, which is complex and difficult to implement.

[0003] Existing technologies for quasi-zero stiffness vibration isolation or stiffness adjustment using permanent magnets mostly rely on bistable negative stiffness structures and strictly linear positive stiffness structures. Bistable negative stiffness structures and strictly linear positive stiffness structures are difficult to design and also limit the application of non-bistable and nonlinear stiffness structures. They cannot adapt to unknown loads and have a small or no range of positive and negative stiffness adjustment, which greatly limits their application scenarios. Summary of the Invention

[0004] This invention addresses the problems of existing quasi-zero stiffness vibration isolators being sensitive to rated load, and the complex structure, difficulty in self-adaptation, and poor real-time performance of rated load adjustment. It proposes a load-adaptive electromagnetic quasi-zero stiffness vibration isolator and method. By using different configurations of coils and permanent magnets, electromagnetic negative stiffness and electromagnetic gradually hardening positive stiffness are achieved. The negative stiffness is modulated using nonlinear gradually hardening positive stiffness to achieve quasi-zero stiffness characteristics. The electromagnetic negative stiffness coil and electromagnetic positive stiffness coil are connected in series; adjusting the coil current changes the rated load of the isolator without affecting the quasi-zero stiffness characteristics. Combined with sensors and a microprocessor, the rated load of the quasi-zero stiffness vibration isolator can be adaptively and in real-time adjusted.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a load-adaptive electromagnetic quasi-zero stiffness vibration isolation device, comprising: a vibration isolator frame, a linear motion component, a negative stiffness structural component, a positive stiffness structural component disposed therein, and a circuit control module connected to the linear motion component, the negative stiffness structural component, and the positive stiffness structural component respectively, wherein: the linear motion component is disposed in the direction of the central axis of the vibration isolator frame, and the negative stiffness structural component without bistable characteristics and the positive stiffness structural component with nonlinear gradually hardening characteristics are sequentially connected and connected to the linear motion component.

[0007] This invention relates to a load-adaptive electromagnetic quasi-zero stiffness vibration isolation method based on the above-mentioned device. The absolute displacement of the load is detected by a displacement sensor. After the tracking error is calculated by the sliding mode adaptive control unit in the circuit control module, the estimated load and corresponding output force are adaptively calculated based on the tracking error. Then, a current adjustment command is sent to the quasi-zero stiffness vibration isolation device to adjust the electromagnetic force of the positive and negative stiffness components.

[0008] The tracking error e = z1 - z d Where: z1 is the measured displacement, z d The desired displacement.

[0009] The estimated load Where: s is the sliding mode variable, g is the gravitational acceleration, and γ and μ are known positive constants; The desired acceleration.

[0010] The output force Where: N h N w N m and N h For the current wire method parameters, d m Where I is the diameter of the current wire, I1 is the coil current, and B is the current-carrying current. r For the remanence of a permanent magnet, r j r s and r t Let z be the radius of the current wire. s z t and z i k is the height of the current wire. t and k s These are the parameters for the elliptic integral.

[0011] The aforementioned current regulation command refers to: calculating and updating the current value and performing negative feedback control, specifically: Among them: I t0 Based on the base current, F c0 Based on current I t0The calculated electromagnetic restoring force.

[0012] The aforementioned sliding mode adaptive control unit, based on the sliding mode control law and according to the deviation of the state variables, estimates the system disturbance and gradually converges the system state trajectory to the sliding surface, and moves towards the origin of the coordinates along the sliding surface to achieve system stability; it adopts, but is not limited to, the technology described by Drakunov, S., & Utkin, V. (1992) in “Sliding mode control in dynamic systems” (International Journal of Control, 55(4), 1029–1037. doi:10.1080 / 00207179208934270).

[0013] The aforementioned sliding mode control law refers to:

[0014] Where μ, D, ε and p are controller parameters, all of which are positive constants; To track the rate of change of error; f(z1,z2) is the sum of elastic restoring force and damping force; σ is the desired acceleration; sat(s) is the saturation function; sgn(v) is the sign function; v is the theoretical output force; u max This represents the maximum output force.

[0015] Technical effect

[0016] This invention utilizes a coaxial nested configuration of conical coils and permanent magnets to achieve greater negative stiffness and electromagnetic force. It employs a nonlinear, gradually hardening positive stiffness structure to modulate a non-bistable negative stiffness structural component, achieving quasi-zero stiffness with small static deformation characteristics. This avoids the stringent requirements of traditional quasi-zero stiffness isolator designs regarding bistable negative stiffness and linear positive stiffness. The electromagnetic negative stiffness coil and electromagnetic positive stiffness coil can be connected in series. By adjusting the coil current, the rated load of the isolator can be changed without losing its quasi-zero stiffness characteristics. Combined with sensors and a microprocessor, adaptive and real-time adjustment of the rated load of the quasi-zero stiffness isolator can be achieved. This solves the problems of existing quasi-zero stiffness isolators, such as load sensitivity, complex structures for rated load adjustment, difficulty in adaptive adjustment, and poor real-time performance. Attached Figure Description

[0017] Figure 1 and Figure 2 This is a cross-sectional view of the present invention;

[0018] Figure 3 Diagram showing the axial nesting configuration of the conical coil and the permanent magnet;

[0019] Figure 4 Force-displacement curves for quasi-zero stiffness vibration isolation devices, positive stiffness components, and negative stiffness components;

[0020] Figure 5 Force-displacement relationship diagram of quasi-zero stiffness vibration isolation device under different energizing currents;

[0021] Figure 6 Force-displacement diagrams for axially nested configurations of conical coils and cylindrical coils with permanent magnets;

[0022] Figure 7 A comparison of static deformation between quasi-zero stiffness vibration isolation devices and traditional quasi-zero stiffness realization methods;

[0023] Figure 8 Here is the flowchart for load adaptive control;

[0024] In the diagram: 1. Base, 2. First bolt, 3. Lower frame, 4. Cylindrical coil, 5. First permanent magnet, 6. Guide rod, 7. Middle frame, 8. Second bolt, 9. Upper frame, 10. Third bolt, 11. End cap, 12. First linear bearing, 13. Load mass, 14. First nut, 15. Fourth bolt, 16. Conical coil, 17. Second permanent magnet, 18. Second nut, 19. Fifth bolt, 20. Second linear bearing, 21. Third nut, 22. Sleeve, 23. Fourth nut, 24. Sixth bolt. Detailed Implementation

[0025] like Figure 1 and Figure 2 As shown, this embodiment relates to a load-adaptive electromagnetic quasi-zero stiffness vibration isolation device, which includes: a vibration isolator frame, a linear motion component, a negative stiffness structural component, a positive stiffness structural component disposed therein, and a circuit control module connected to the linear motion component, the negative stiffness structural component, and the positive stiffness structural component respectively. The linear motion component is disposed in the direction of the central axis of the vibration isolator frame. The negative stiffness structural component, which does not have bistable characteristics, and the positive stiffness structural component, which has nonlinear gradually stiffening characteristics, are sequentially connected and connected to the linear motion component.

[0026] The vibration isolator frame includes: a base 1, a hollow lower, middle and upper frame 9 and an end cap 11, which are fixedly connected in sequence, wherein: the base 1 is sleeved with the lower frame 3, and the end cap 11 is sleeved with the upper frame 9 inside.

[0027] The base 1 is provided with a boss, and a circular notch is provided on the side of the lower frame 3.

[0028] The middle frame 7 is provided with a boss and a central hole, which fits into the lower frame 3 and is connected by bolts. The upper frame 9 is provided with grooves at both ends and a tapered hole inside, which fits into the middle frame 7 and is fixedly connected by bolts.

[0029] The end cap 11 has protrusions at both ends and a central hole inside, which fits into the upper frame 9 and is fixedly connected by bolts.

[0030] The linear motion assembly includes: a guide rod 6 and a first linear bearing 12 and a second linear bearing 20 respectively disposed thereon, wherein: the first linear bearing 12 fits into the center hole of the end cap 11 and is fixed to the protrusion of the end cap 11 by bolts; the second linear bearing 20 fits into the center hole of the middle frame 7 and is connected to the middle frame 7 by bolts; the first linear bearing 12 and the second linear bearing 20 are respectively fitted into the two ends of the guide rod 6 and are clearance-fitted with the linear bearings.

[0031] The positive stiffness component includes: a cylindrical coil 4, a first permanent magnet 5, and a sleeve 22, wherein: the first permanent magnet 5 is directly opposite the cylindrical coil 4; the bottom surface of the cylindrical coil 4 is attached to the surface of the base 1; the sleeve 22 is embedded in the central hole of the permanent magnet; the sleeve 22 is threaded and screwed onto the guide rod 6; upper and lower limit nuts are screwed onto the guide rod 6; the position of the first permanent magnet 5 is determined by the position of the upper and lower limit nuts.

[0032] like Figure 3 As shown, the negative stiffness component includes a conical coil 16 and a second permanent magnet 17, wherein the second permanent magnet 17 and the conical coil 16 are coaxially nested; the conical coil 16 is fitted with the upper frame 9, the center hole of the second permanent magnet 17 is fitted with the guide rod 6, one side is in contact with the shoulder of the guide rod 6, and the other side is pressed by a nut.

[0033] Except for the permanent magnet, all components of the vibration isolator frame, the linear motion component, the negative stiffness structural component, and the positive stiffness structural component are preferably made of low magnetic permeability materials.

[0034] The circuit control module includes a sliding mode adaptive control unit and a displacement sensor, a current sensor, and a power amplifier connected thereto. The displacement sensor detects the position of the load 13 of the vibration isolation device, the current sensor detects the current in the coil, and the power amplifier is connected to the signal output port of the sliding mode adaptive control unit. After the sliding mode adaptive control unit adaptively calculates the estimated load and corresponding output force based on the tracking error, it sends a current adjustment command to the power amplifier. The current in the coil is adjusted online in real time according to the position change of the load 13, so that the load position of the quasi-zero stiffness vibration isolator does not change due to the load change, the vibration isolator still maintains high static stiffness and low dynamic stiffness characteristics, and the low-frequency vibration isolation performance does not deteriorate with the load change.

[0035] like Figure 4As shown, when the coil is energized, an electromagnetic force is generated between the first permanent magnet 5 and the cylindrical coil 4. The force-displacement relationship exhibits nonlinear gradually hardening stiffness characteristics. According to Ampere's law, positive stiffness is proportional to current. When the coil is energized, an electromagnetic force is generated between the second permanent magnet 17 and the conical coil 16. The force-displacement relationship exhibits non-bistable negative stiffness characteristics. According to Ampere's law, negative stiffness is proportional to current. By changing the positions of the third nut 21 and the fourth nut 23 to adjust the position of the first permanent magnet 5, and by modulating the negative stiffness using nonlinear gradually hardening positive stiffness, the vibration isolation device of this invention can achieve quasi-zero stiffness characteristics, thereby having a low natural frequency and exhibiting excellent low-frequency vibration isolation performance.

[0036] like Figure 5 As shown, when the cylindrical coil 4 and the conical coil 16 are connected in series, according to Ampere's law, the rated load of the quasi-zero stiffness vibration isolation device of the present invention is proportional to the current. By changing the current flowing through the coil, the rated load of the quasi-zero stiffness vibration isolation device can be adjusted without losing its quasi-zero stiffness characteristics.

[0037] like Figure 6 As shown, compared to the conventional coaxial nesting configuration of cylindrical coil and permanent magnet, the coaxial nesting configuration of the conical coil 16 and the second permanent magnet 17 can generate greater negative stiffness and electromagnetic force with the same coil volume.

[0038] like Figure 7 As shown, compared with the traditional quasi-zero stiffness vibration isolator designed by connecting a bistable negative stiffness structure and a linear spring in parallel, the vibration isolation device of this invention uses a nonlinear gradually hardening positive stiffness structure to modulate a non-bistable negative stiffness structure to achieve quasi-zero stiffness, which has the advantage of small static deformation.

[0039] like Figure 8 As shown, the quasi-zero stiffness vibration isolation device of the present invention, in conjunction with sensors and microprocessors, can achieve real-time adaptive adjustment of the load of the vibration isolation device without losing its quasi-zero stiffness characteristics.

[0040] Compared with existing technologies, this invention utilizes a coaxial nested configuration of a conical coil and a permanent magnet to enhance the negative stiffness and electromagnetic force generated by the traditional cylindrical coil and permanent magnet configuration. It employs a nonlinear gradually hardening positive stiffness structure to modulate a non-bistable negative stiffness structure, achieving quasi-zero stiffness. This offers the advantage of small static deformation compared to traditional methods, eliminating the dependence of traditional quasi-zero stiffness isolator designs on bistable negative stiffness and linear positive stiffness. The rated load of the quasi-zero stiffness isolator is proportional to the current; by simply adjusting the coil current, the rated load of the isolator can be changed without losing its quasi-zero stiffness characteristics. Combined with sensors and a microprocessor, the quasi-zero stiffness isolator can achieve adaptive and real-time load adjustment. This solves the problems of existing quasi-zero stiffness isolators being sensitive to load, having complex structures for rated load adjustment, being difficult to adapt, and having poor real-time performance.

[0041] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A load-adaptive electromagnetic quasi-zero stiffness vibration isolation device, characterized in that, include: The vibration isolator frame, a linear motion component, a negative stiffness structural component, a positive stiffness structural component, and a circuit control module connected to the linear motion component, the negative stiffness structural component, and the positive stiffness structural component respectively, wherein: the linear motion component is located in the direction of the central axis of the vibration isolator frame, and the negative stiffness structural component without bistable characteristics and the positive stiffness structural component with nonlinear gradually hardening characteristics are connected in sequence and connected to the linear motion component. The linear motion assembly includes: a guide rod and a first linear bearing and a second linear bearing respectively disposed thereon, wherein: the first linear bearing is fitted with the center hole of the end cap and fixed to the end cap protrusion by bolts; the second linear bearing is fitted with the center hole of the middle frame and connected to the middle frame by bolts; the first linear bearing and the second linear bearing are respectively fitted into the two ends of the guide rod and are clearance-fitted with the linear bearings. The positive stiffness structure component includes: a cylindrical coil, a first permanent magnet, and a sleeve, wherein: the first permanent magnet is directly opposite the cylindrical coil; the bottom surface of the cylindrical coil is attached to the surface of the base; the sleeve is embedded in the central hole of the permanent magnet; the sleeve is threaded and screwed onto the guide rod; upper and lower limit nuts are screwed onto the guide rod; the position of the first permanent magnet is determined by the position of the upper and lower limit nuts. The negative stiffness structure component includes: a conical coil and a second permanent magnet, wherein: the second permanent magnet and the conical coil are coaxially nested; the conical coil is fitted with the upper frame, the central hole of the second permanent magnet is fitted with the guide rod, one side is in contact with the shoulder of the guide rod, and the other side is pressed by a nut; When the coil is energized, an electromagnetic force is generated between the first permanent magnet and the cylindrical coil. The force-displacement relationship exhibits nonlinear gradually hardening stiffness characteristics. According to Ampere's law, positive stiffness is proportional to current. When the coil is energized, an electromagnetic force is generated between the second permanent magnet and the conical coil. The force-displacement relationship exhibits non-bistable negative stiffness characteristics. According to Ampere's law, negative stiffness is proportional to current. By changing the positions of the upper and lower limit nuts, the position of the first permanent magnet can be adjusted, and the negative stiffness can be modulated using nonlinear gradually hardening positive stiffness. When the cylindrical coil and the conical coil are connected in series, according to Ampere's law, the rated load is proportional to the current. By changing the current flowing through the coil, the rated load of the quasi-zero stiffness vibration isolation device can be adjusted without losing its quasi-zero stiffness characteristics. Compared to the traditional coaxial nested configuration of cylindrical coil and permanent magnet, the coaxial nested configuration of the conical coil and the second permanent magnet can generate greater negative stiffness and electromagnetic force with the same coil volume; The aforementioned load-adaptive electromagnetic quasi-zero stiffness vibration isolation refers to: detecting the absolute displacement of the load through a displacement sensor, calculating the tracking error through a sliding mode adaptive control unit in the circuit control module, adaptively calculating the estimated load and corresponding output force based on the tracking error, and then sending a current adjustment command to the quasi-zero stiffness vibration isolation device to adjust the electromagnetic force of the positive and negative stiffness structural components. The aforementioned tracking error ,in: To measure displacement, The desired displacement; The estimated load ,in: For sliding mode variables, It is the acceleration due to gravity. and Given positive constants; For the desired acceleration; The output force ,in: , and These are the parameters for the current wire method. The diameter of the current wire. The current flowing through the coil, For the remanence of permanent magnets, , and Where is the radius of the current wire. , and The height of the current wire; and These are the parameters for the elliptic integral; The sliding mode adaptive control unit estimates system disturbances based on the sliding mode control law and the deviation of state variables, and gradually converges the system state trajectory to the sliding surface and moves towards the origin along the sliding surface, thereby achieving system stability. The aforementioned sliding mode control law refers to: ,in: , , and These are controller parameters, all of which are normal values; To track the rate of change of error; It is the sum of elastic restoring force and damping force; For the desired acceleration; It is a saturation function; It is a symbolic function; The theoretical output force; This is the maximum output force; The aforementioned current regulation command refers to: calculating and updating the current value and performing negative feedback control, specifically: ,in: Based on the base current, base current The calculated electromagnetic restoring force.

2. The load-adaptive electromagnetic quasi-zero stiffness vibration isolation device according to claim 1, characterized in that, The vibration isolator frame includes: a base, a hollow lower, middle, and upper frame, and an end cap that are fixedly connected in sequence, wherein: the base is sleeved with the lower frame, and the end cap is sleeved with the upper frame inside.

3. The load-adaptive electromagnetic quasi-zero stiffness vibration isolation device according to claim 1, characterized in that, The circuit control module includes a sliding mode adaptive control unit and a displacement sensor, a current sensor, and a power amplifier connected thereto. The displacement sensor detects the position of the load on the vibration isolation device, the current sensor detects the current in the coil, and the power amplifier is connected to the signal output port of the sliding mode adaptive control unit. After the sliding mode adaptive control unit adaptively calculates the estimated load and corresponding output force based on the tracking error, it sends a current adjustment command to the power amplifier. The current in the coil is adjusted online in real time according to the change in the position of the load, so that the load position of the quasi-zero stiffness vibration isolator does not change due to the change in load, the vibration isolator still maintains high static stiffness and low dynamic stiffness characteristics, and the low-frequency vibration isolation performance does not deteriorate with the change in load.

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