CN113513559B - Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect - Google Patents
Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect Download PDFInfo
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- CN113513559B CN113513559B CN202110522241.2A CN202110522241A CN113513559B CN 113513559 B CN113513559 B CN 113513559B CN 202110522241 A CN202110522241 A CN 202110522241A CN 113513559 B CN113513559 B CN 113513559B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
- F16F15/002—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion characterised by the control method or circuitry
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
- F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
- F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
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Abstract
The invention discloses a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect, which comprises a load upper platform and a foundation lower platform, wherein three angular positions of the load upper platform are respectively and fixedly connected with an upper rotating joint, three angular positions of the foundation lower platform are respectively connected with a lower rotating joint, and six single-leg vibration isolation units are connected between the three upper rotating joints and the three lower rotating joints; each supporting beam of the upper loading platform is provided with three pairs of MFC piezoelectric fiber patches, each pair of MFC piezoelectric fiber patches comprises an MFC sensor and an MFC actuator, the MFC sensors and the MFC actuators in each pair of MFC piezoelectric fiber patches can be exchanged in roles, and the MFC sensors and the MFC actuators are respectively and electrically connected with a controller through wires. The invention combines a plurality of MFC sensors and MFC actuators with a controller, can realize active control vibration reduction, adopts active and passive composite vibration reduction technology, can reduce resonance peak value, simultaneously ensures high-frequency attenuation rate, and realizes better vibration isolation effect.
Description
Technical Field
The invention relates to the technical field of precise vibration isolation, in particular to a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect.
Background
In recent years, as the use of precision equipment has increased, the performance requirements have increased, and the vibration isolation requirements for precision equipment have also increased. Among a plurality of vibration isolators, the vibration isolation platform based on the Stewart platform is one of the most concerned vibration isolation methods due to the characteristics of easy decoupling, large bearing capacity and the like. Common vibration isolation techniques are classified into passive vibration isolation and active vibration isolation, wherein the active vibration isolation is widely studied for its good performance.
The vibration isolation performance of active vibration isolation is mainly determined by actuators, and common actuators include piezoelectric type, electromagnetic type, hydraulic type and the like, wherein the piezoelectric type actuator has the advantages of low power consumption, high response, high precision and the like. Common piezoelectric actuators include a stacked type, a ceramic sheet, an MFC (piezoelectric fiber composite material) and the like, and the MFC has the characteristics of light weight, small volume, quick response, high precision, large actuating power, low rigidity and the like, can be used as a sensor and an actuator at the same time, and is flexible to use.
Chinese patent document CN108593246a provides an active vibration suppression device for a wind tunnel model based on piezoelectric ceramics. The device uses a proper amount of piezoelectric ceramics as actuators, and is arranged in a plurality of stepped grooves on a tail boom support rod, and the characteristics of quick dynamic response and large actuating power of the piezoelectric ceramics are utilized to effectively inhibit the pitching and yawing vibration of the model. But the detection of vibration interference signals and active vibration isolation control have not been studied.
Chinese patent document CN111458013A provides a piezoelectric fiber composite (MFC) sensing device for platform vibration isolation. The device is prepared from a piezoelectric ceramic fiber composite material, and by utilizing the characteristics of high precision, quick response and the like, the device captures vibration energy in all directions and converts the vibration energy into an electric signal, so that the effect of the sensor is realized. However, the effect is single, and the effect of the actuator is not considered.
Disclosure of Invention
The invention aims to provide a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect, which solves the problems in the prior art, adopts active and passive composite vibration attenuation technology, can reduce resonance peak value, ensures high frequency attenuation rate, realizes better vibration isolation effect, and has sensitive response, safety and reliability.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect, which comprises a load upper platform and a base lower platform which are respectively in a triangular structure, wherein the vertical projections of three angles after the load upper platform horizontally rotates by 120 degrees are superposed with the vertical projections of three angles of the base lower platform, three angular positions of the load upper platform are respectively and fixedly connected with an upper rotary joint, three angular positions of the base lower platform are respectively connected with a lower rotary joint, six single-leg vibration isolation units are connected between the three upper rotary joints and the three lower rotary joints, adjacent single-leg vibration isolation units are mutually vertical, opposite single-leg vibration isolation units are mutually parallel, the whole body is in a cubic configuration, and decoupling is convenient; each supporting beam of the load upper platform is provided with three pairs of MFC piezoelectric fiber patches, each pair of MFC piezoelectric fiber patches comprise an MFC sensor and an MFC actuator, the piezoelectric positive and negative effects are utilized, each MFC in each pair of MFC piezoelectric fiber patches can perform role switching of the sensor and the actuator according to actual requirements, and switching can be performed in a control loop only according to the piezoelectric positive and negative effects. Each pair of MFC piezoelectric fiber patches can be used as an MFC sensor and an MFC actuator, the roles of the MFC sensor and the actuator are exchanged, the MFC sensor and the MFC actuator are respectively and electrically connected with a controller through leads, and the plurality of MFC sensors and the MFC actuators are combined with the controller, so that active control on vibration reduction can be realized.
Optionally, the six single-leg vibration isolation units have the same structure; each single-leg vibration isolation unit comprises an upper end cover, a middle retainer and a lower end cover which are fixedly connected in sequence; the upper end cover is internally provided with a pressure spring type negative stiffness structure, the top end of the pressure spring type negative stiffness structure penetrates through the upper end cover and then is connected with an upper end flexible hinge, and the bottom of the lower end cover is fixedly connected with a lower end flexible hinge.
Optionally, two connecting flanges are fixedly arranged on the inner wall of the upper end cover; the pressure spring formula burden rigidity structure includes the three-way adapter, the both ends that the three-way adapter is located the below respectively through the pressure spring with connecting flange fixed connection on the upper end cover inner wall, the one end that the three-way adapter is located the top passes through pressure spring fixedly connected with bracing piece, the bracing piece runs through behind the upper end cover top with upper end flexible hinge fixed connection.
Optionally, a connecting block is arranged on one side of the top of the upper rotating joint, two first connecting holes arranged in parallel are formed in the connecting block, two symmetrical inclined planes are formed on one side, close to the connecting block, of the upper rotating joint, two second connecting holes arranged vertically are formed in the two inclined planes, and the upper rotating joint is the same as the lower rotating joint in structure; the first connecting hole of the upper rotary joint is fixedly connected with the load upper platform through a screw, and the first connecting hole of the lower rotary joint is fixedly connected with the foundation lower platform through a screw.
Optionally, the three upper adapters are respectively a first upper adapter, a second upper adapter and a third upper adapter, and the three lower adapters are respectively a first lower adapter, a second lower adapter and a third lower adapter; the six single-leg vibration isolation units are respectively a first single-leg vibration isolation unit, a second single-leg vibration isolation unit, a third single-leg vibration isolation unit, a fourth single-leg vibration isolation unit, a fifth single-leg vibration isolation unit and a sixth single-leg vibration isolation unit; the two second connecting holes of the first upper rotary joint are fixedly connected with the upper end flexible hinges of the first single-leg vibration isolation unit and the sixth single-leg vibration isolation unit respectively, the two second connecting holes of the second upper rotary joint are fixedly connected with the upper end flexible hinges of the second single-leg vibration isolation unit and the third single-leg vibration isolation unit respectively, and the two second connecting holes of the third upper rotary joint are fixedly connected with the upper end flexible hinges of the fourth single-leg vibration isolation unit and the fifth single-leg vibration isolation unit respectively; two second connecting holes of first adapter down respectively with the flexible hinge fixed connection of the lower extreme of first single leg vibration isolation unit and second single leg vibration isolation unit, two second connecting holes of second lower adapter down respectively with the flexible hinge fixed connection of the lower extreme of third single leg vibration isolation unit and fourth single leg vibration isolation unit, two second connecting holes of third lower adapter down respectively with the flexible hinge fixed connection of the lower extreme of fifth single leg vibration isolation unit and sixth single leg vibration isolation unit.
Optionally, the three MFC sensors arranged on each support beam of the load upper platform are respectively a first MFC sensor, a second MFC sensor and a third MFC sensor, and the three MFC actuators are respectively a first MFC actuator, a second MFC actuator and a third MFC actuator; the first MFC sensor and the first MFC actuator are symmetrically arranged on the upper surface and the lower surface of the supporting beam of the upper platform of the load, the second MFC sensor and the second MFC actuator are symmetrically embedded in the cross section of the upper platform of the load, and the third MFC sensor and the third MFC actuator are symmetrically arranged on the upper surface and the lower surface of the supporting beam of the upper platform of the load; the second MFC sensor and second MFC actuator are located at a position between the first MFC sensor and third MFC sensor. The pair of the upper platform supports are embedded on the transverse cross section of the upper platform support, so that the upper platform support can generate transverse micro-displacement; and the other two pairs of the upper platform supports are embedded on the surface of the upper platform support, so that the upper platform support can generate vertical micro-displacement. The sensor perception external vibration signal, give the controller with vibration signal transmission through the wire, the controller passes through the wire with control signal and gives the actuator, and real time control actuator produces the displacement in order to offset external vibration.
Optionally, symmetrical connecting threaded holes are formed in the end faces of the upper end cover, the middle retainer and the lower end cover respectively, long bolts penetrate through the connecting threaded holes, and the upper end cover, the middle retainer and the lower end cover are fixedly connected through the long bolts.
Optionally, the load upper platform is of an isosceles triangle structure, horizontal connection end faces are arranged at positions outside three corners of the load upper platform, the upper rotary joint is fixedly arranged at the horizontal connection end faces, three reinforcing rods are arranged in the load upper platform, one ends of the three reinforcing rods are respectively connected with one corner of the load upper platform and located on an bisector of the corner, and the other ends of the three reinforcing rods are fixedly connected at a position of a circle center of a circumscribed circle of the load upper platform; the base lower platform is of an isosceles triangle structure, a horizontal connection end face is arranged at the position of the outer side of three corners of the base lower platform, a lower rotary joint is fixedly arranged at the position of the horizontal connection end face, three reinforcing rods are arranged in the base lower platform, one end of each reinforcing rod is connected with one corner of the base lower platform and located on an equal dividing line of the corner, and the other end of each reinforcing rod is fixedly connected with the position of the circle center of an outer circle of the base lower platform.
Optionally, the width of the reinforcing rod of the upper loading platform is smaller than that of the supporting beam of the upper loading platform; so that the function of MFC piezoelectric fiber sheeting plays a major role. The width of the reinforcing rod of the platform under the foundation is larger than that of the supporting beam of the platform under the foundation, so that the bearing capacity of the platform under the foundation is improved. Three angles of the upper load platform and the lower base platform are provided with threaded holes, and the threaded holes are used for being connected with an upper rotating joint or a lower rotating joint.
In the active vibration isolation unit, an MFC sensor is used for receiving a vibration interference signal of a load platform and transmitting the vibration interference signal to a controller through a lead; the controller selects a control algorithm to carry out real-time control on the vibration interference signal to obtain a real-time control signal, and the real-time control signal is transmitted to the MFC actuator through a lead; the real-time control signal drives the MFC actuator to generate corresponding actuating power, and the actuating power is offset from the vibration interference signal, so that the vibration of the load platform is reduced, and the vibration active control is realized.
The vibration isolation platform is based on a Stewart configuration, adopts an active control method, and specifically comprises the following steps:
(1) Sensor receiving vibration interference signal
The MFC sensor is used for receiving a vibration signal of the load platform under vibration interference, when the load platform generates vibration deformation, the MFC sensor can generate corresponding electric charge, and the generated electric charge is in direct proportion to the deformation of the load platform. Vibration disturbance signal p received by MFC sensor i (i = 1.. 9.) is communicated to the controller via a wire.
(2) The controller calculates the vibration interference signal
The vibration interference signal transmitted from the MFC sensor to the controller is calculated through a control algorithm, and the calculated output signal is the control signal of the actuator. Control signals calculated by the controller are transmitted to the MFC actuators via wires.
(3) Actuator output actuating power
The control signal transmitted to the MFC actuator from the controller can drive the MFC actuator to generate corresponding actuating force, and the generated actuating force can be offset with the vibration interference signal so as to restore the load platform to the original state, thereby realizing the active control of the Stewart vibration isolation platform.
In the step of calculating the vibration interference signal by the controller, the used control algorithm can be PID control, an adaptive RLS algorithm, an adaptive LMS algorithm and the like.
The PI integral force control is from the classical control algorithm PID control, see bibliography automatic regulating system analysis and PID tuning, bai Zhigang, beijing, chemical industry Press, 2012.
The adaptive RLS algorithm or the adaptive LMS algorithm is from adaptive control Chai Tianyou, yue Heng, beijing, qinghua university Press 2016.
Compared with the prior art, the invention has the following technical effects:
the MFC adopted by the vibration isolation platform has the characteristics of light weight, small volume, quick response, high precision, large actuating power, low rigidity and the like, is easy to be adhered to various structures, and is convenient to install. The active control vibration reduction of the Stewart-configuration vibration isolation platform can be realized by using a plurality of MFCs, the adopted sensors and actuators are MFCs, the role switching of each MFC can be realized according to actual requirements, the MFC can be used as an MFC sensor or an MFC actuator, the original structure and position of the MFC actuator are not required to be changed, the role exchange of the MFC can be realized only by switching in a control loop according to the positive and negative effects of piezoelectricity, and the MFC actuator can be used as an MFC sensor or an MFC actuator. The six single-leg vibration isolation units comprise compression spring type negative stiffness structures, so that the six single-leg vibration isolation units are guaranteed to be low in stiffness, and the function of the MFC actuator is dominant.
The vibration isolation platform is divided into a passive vibration isolation unit and an active vibration isolation unit, and the passive vibration isolation unit is formed by the upper load platform, the lower foundation platform, the single-leg unit and the adapter. A closed-loop control loop formed by the MFC sensor, the controller, the MFC actuator and the lead is an active control unit. The passive vibration isolation unit ensures the reliability of vibration isolation performance, and when the active vibration isolation unit fails, the vibration isolation platform still has a certain vibration isolation effect. The active vibration isolation unit improves the vibration isolation performance, so that the vibration isolation platform has good vibration isolation performance at low-frequency resonance and high-frequency resonance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of the general structure of a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effects;
FIG. 2 is a schematic structural diagram of a single-leg vibration isolation unit of the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect;
FIG. 3 is a structural schematic diagram of a compression spring type negative stiffness of the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect;
FIG. 4 is a schematic diagram of a flexible hinge structure of a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect;
FIG. 5 is a schematic structural diagram of an upper end cover of a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effects;
FIG. 6 is a structural schematic diagram of a middle retainer of a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect;
FIG. 7 is a schematic structural diagram of a lower end cover of a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect;
FIG. 8 is a schematic structural diagram of a loading platform of the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect;
FIG. 9 is a schematic structural diagram of a basic platform of the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect;
fig. 10 is a schematic structural diagram of an adapter of the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect;
FIG. 11 is a schematic diagram of the geometrical principle of a Stewart configuration in a Stewart vibration isolation platform based on MFC positive and reverse piezoelectric effects;
FIG. 12 (a) is a schematic diagram of the action mechanism of a conventional passive vibration isolation platform;
FIG. 12 (b) is a schematic diagram of the action mechanism and the control principle of the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect in the invention;
FIG. 13 is a graph comparing transmittance curves for a conventional vibration isolation platform, passive vibration isolation according to the present invention, and active control according to the present invention;
description of the reference numerals: the Stewart vibration isolation platform based on the MFC positive and negative piezoelectric effect comprises a Stewart vibration isolation platform 100, a load upper platform 1, an upper joint 2, a first upper joint 2a, a second upper joint 2b, a third upper joint 2c, a single-leg vibration isolation unit 3, a first single-leg vibration isolation unit 3a, a second single-leg vibration isolation unit 3b, a third single-leg vibration isolation unit 3c, a fourth single-leg vibration isolation unit 3d, a fifth single-leg vibration isolation unit 3e, a sixth single-leg vibration isolation unit 3f, an upper end flexible hinge 31a, a lower end flexible hinge 31b, an upper end cover 32, a connecting flange 321, an intermediate retainer 33, a lower end cover 34, a supporting rod 35, a pressure spring 36, a three-way adapter 37, a lower adapter 4, a first lower adapter 4a, a second lower adapter 4b, a third lower adapter 4c, a base lower platform 5, a controller 11, a first MFC sensor 12, a first MFC actuator 13, a second MFC sensor 14, a second MFC actuator 15, a third MFC sensor 16 and a third MFC 17.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect, which solves the problems in the prior art, adopts active and passive composite vibration attenuation technology, can reduce resonance peak value, ensures high frequency attenuation rate, realizes better vibration isolation effect, and has sensitive response, safety and reliability.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to the attached drawings 1-11, the invention provides a Stewart vibration isolation platform 100 based on MFC positive and negative piezoelectric effect, which comprises a load upper platform 1 and a base lower platform 5 which are in a triangular structure respectively, wherein the vertical projections of three angles after the load upper platform 1 rotates horizontally by 120 degrees are superposed with the vertical projections of three angles of the base lower platform 5, three angular positions of the load upper platform 1 are fixedly connected with an upper adapter 2 respectively, three angular positions of the base lower platform 5 are connected with a lower adapter 4 respectively, six single-leg vibration isolation units 3 are connected between the three upper adapters 2 and the three lower adapters 4, adjacent single-leg vibration isolation units 3 are perpendicular to each other, the opposite single-leg vibration isolation units 3 are parallel to each other, and the whole body is in a cubic configuration, so that decoupling is convenient; every supporting beam of load upper platform 1 all is provided with three pairs of MFC piezoelectric fiber paster, every MFC piezoelectric fiber paster all includes an MFC sensor and an MFC actuator, utilizes piezoelectric positive and negative effect, and every MFC in every MFC piezoelectric fiber paster can all carry out the role conversion of sensor and actuator according to actual demand, only need according to piezoelectric positive and negative effect, switch at control loop can. Each pair of MFC piezoelectric fiber patches can be used as an MFC sensor and an MFC actuator, the same material/device can be realized, roles of the MFC sensor and the actuator are exchanged, the MFC sensor and the MFC actuator are respectively and electrically connected with a controller through wires, and the plurality of MFC sensors and the MFC actuators are combined with the controller, so that active control vibration reduction of the Stewart-configuration vibration isolation platform can be realized.
Specifically, the six single-leg vibration isolation 3 units have the same structure; each single-leg vibration isolation unit 3 comprises an upper end cover 32, a middle retainer 33 and a lower end cover 34 which are fixedly connected in sequence, symmetrical connecting threaded holes are respectively formed in the end surfaces of the upper end cover 32, the middle retainer 33 and the lower end cover 34, long bolts are arranged in the connecting threaded holes in a penetrating mode, and the upper end cover 32, the middle retainer 33 and the lower end cover 34 are fixedly connected through the long bolts; a pressure spring type negative stiffness structure is arranged in the upper end cover 32, the top end of the pressure spring type negative stiffness structure penetrates through the upper end cover 32 and then is connected with an upper end flexible hinge 31a, and the bottom of the lower end cover 34 is fixedly connected with a lower end flexible hinge 31b. Due to the existence of the compression spring type negative stiffness structure, each single-leg vibration isolation unit 3 presents negative stiffness in a certain stroke, so that the overall stiffness is soft, and the actuation power of the MFC actuator can play a larger role.
Two connecting flanges 321 are fixedly arranged on the inner wall of the upper end cover 32; the compression spring type negative stiffness structure comprises a three-way adapter 37, two ends of the lower side of the three-way adapter 37 are fixedly connected with a connecting flange 321 on the inner wall of the upper end cover 32 through compression springs 36 respectively, one end of the three-way adapter 37 located above is fixedly connected with a support rod 35 through the compression springs 36, and the support rod 35 penetrates through the top of the upper end cover 32 and then is fixedly connected with an upper end flexible hinge 31 a. The upper end flexible hinge 31a is connected with the support rod 35 through a threaded rod and a threaded hole of the support rod, penetrates through the upper end cover 32 after being connected, and a certain gap is reserved to ensure the axial freedom degree of the single-leg vibration isolation unit. The lower end cover 34 and the lower end flexible hinge 31b are connected by their own threaded rods and threaded holes without leaving a gap. When external vibration interference is transmitted to the single-leg vibration isolation unit 3 through the lower foundation platform 5, the compression spring type negative stiffness structure consumes a part of energy due to the negative stiffness principle, transmits a vibration interference signal to the upper load platform 1, and offsets the vibration interference signal with actuating force generated by an MFC actuator after the vibration interference signal is received by the MFC sensor and an output control signal is processed by the controller 11, so that vibration of the upper load platform 1 is restrained.
A connecting block is arranged on one side of the top of the upper rotating joint 2, two first connecting holes which are arranged in parallel are formed in the connecting block, two symmetrical inclined planes are formed on one side, close to the connecting block, of the upper rotating joint 2, two second connecting holes which are arranged vertically are formed in the two inclined planes, and the upper rotating joint 2 and the lower rotating joint 4 are identical in structure; the first connecting hole of the upper rotary joint 2 is fixedly connected with the upper load platform through a screw, and the first connecting hole of the lower rotary joint 4 is fixedly connected with the lower base platform 5 through a screw. The three upper rotary joints 2 are respectively a first upper rotary joint 2a, a second upper rotary joint 2b and a third upper rotary joint 2c, and the three lower rotary joints 4 are respectively a first lower rotary joint 4a, a second lower rotary joint 4b and a third lower rotary joint 4c; the six single-leg vibration isolation units 3 are respectively a first single-leg vibration isolation unit 3a, a second single-leg vibration isolation unit 3b, a third single-leg vibration isolation unit 3c, a fourth single-leg vibration isolation unit 3d, a fifth single-leg vibration isolation unit 3e and a sixth single-leg vibration isolation unit 3f; two second connecting holes of the first upper rotating joint 2a are fixedly connected with upper end flexible hinges of the first single-leg vibration isolation unit 3a and the sixth single-leg vibration isolation unit 3f respectively, two second connecting holes of the second upper rotating joint 2b are fixedly connected with upper end flexible hinges of the second single-leg vibration isolation unit 3b and the third single-leg vibration isolation unit 3c respectively, and two second connecting holes of the third upper rotating joint 2c are fixedly connected with upper end flexible hinges of the fourth single-leg vibration isolation unit 3d and the fifth single-leg vibration isolation unit 3e respectively; two second connecting holes of the first lower adapter 4a are fixedly connected with lower end flexible hinges of the first single-leg vibration isolation unit 3a and the second single-leg vibration isolation unit 3b respectively, two second connecting holes of the second lower adapter 4b are fixedly connected with lower end flexible hinges of the third single-leg vibration isolation unit 3c and the fourth single-leg vibration isolation unit 3d respectively, and two second connecting holes of the third lower adapter 4c are fixedly connected with lower end flexible hinges of the fifth single-leg vibration isolation unit 3e and the sixth single-leg vibration isolation unit 3f respectively.
The three MFC sensors arranged on each supporting beam of the upper loading platform 1 are respectively a first MFC sensor 12, a second MFC sensor 14 and a third MFC sensor 16, and the three MFC actuators are respectively a first MFC actuator 13, a second MFC actuator 15 and a third MFC actuator 17; a first MFC sensor 12 and a first MFC actuator 13 are symmetrically arranged on the upper surface and the lower surface of a supporting beam of the load upper platform 1, a second MFC sensor 14 and a second MFC actuator 15 are symmetrically embedded in the cross section of the supporting beam of the load upper platform 1, and a third MFC sensor 16 and a third MFC actuator 17 are symmetrically arranged on the upper surface and the lower surface of the supporting beam of the load upper platform 1; a second MFC sensor 14 and a second MFC actuator 15 are located at a position between the first MFC sensor 12 and the third MFC sensor 16. The first MFC sensor 12 and the third MFC sensor 16 are configured to receive vibration interference signals in the longitudinal direction of the beam, the second MFC sensor 14 is configured to receive vibration interference signals in the axial direction of the beam, and the vibration interference signals received by the 9 sensors on the three beams jointly form the vibration condition of the load platform 1. The first MFC actuator 13 and the third MFC actuator 17 are used for providing the actuation force in the longitudinal direction of the beam, the second MFC actuator 15 is used for providing the actuation force in the axial direction of the beam, the actuation forces provided by the 9 actuators on the three beams act together to cancel out an external vibration interference signal, and therefore the vibration amplitude of the load platform 1 is reduced.
Preferably, the load upper platform 1 is in an isosceles triangle structure, horizontal connecting end faces are arranged at the outer sides of three corners of the load upper platform 1, the upper rotating joint 2 is fixedly arranged at the horizontal connecting end faces, three reinforcing rods are arranged in the load upper platform 1, one ends of the three reinforcing rods are respectively connected with one corner of the load upper platform 1 and located on an equal dividing line of the corner, and the other ends of the three reinforcing rods are fixedly connected at the position of the circle center of a circumscribed circle of the load upper platform 1; platform 5 is isosceles triangle structure under the basis, and the horizontal connection terminal surface has been seted up to platform 5's three angle outside position department under the basis, and lower adapter 4 is fixed to be set up in horizontal connection terminal surface department, is provided with three stiffener in the platform 5 under the basis, and three stiffener one end is connected with platform 5's under the basis angle respectively to be located the partition line at place angle, the centre of a circle position department fixed connection of platform 5 circumcircle under the basis of the three stiffener other end. The width of the reinforcing rod of the upper loading platform 1 is less than that of the supporting beam of the upper loading platform 1; the width of the reinforcing rods of the foundation lower platform 5 is larger than the width of the supporting beams of the foundation lower platform 5.
Three MFC sensors, a controller 11 and three MFC actuators on each beam form a closed loop, and the closed loop plays a role in actively controlling vibration isolation. The passive vibration isolation unit is composed of a load upper platform 1, a foundation lower platform 5, a single-leg vibration isolation unit 3, an upper rotary joint 2 and a lower rotary joint 4. When the active vibration isolation unit does not work, the vibration isolation platform is equivalent to passive vibration isolation.
When the vibration isolation platform works, external vibration interference signals are transmitted to the single-leg vibration isolation unit 3 from the foundation lower platform 5, and the compression spring type negative stiffness structure in the single-leg vibration isolation unit 3 has the effect of a negative stiffness spring and can consume a part of energy. The rest energy is transmitted to the load upper platform 1 through the single-leg vibration isolation unit, in the active control loop, the MFC sensor receives vibration interference signals of the load upper platform 1 and transmits the vibration interference signals to the controller 11 for processing, the controller 11 outputs real-time control signals to drive the MFC actuator to generate actuating force, and the actuating force is offset with the vibration interference signals of the load upper platform 1 to reduce the vibration of the load upper platform 1.
As shown in fig. 12 (a), the passive vibration isolation platform can be equivalent to a mass-spring-damper system, whose transfer function is:
the formula belongs to the complex field range, wherein X i For the displacement response of the platform on the load after being subjected to vibration interference signals, X 0 On the basis, the platform is subjected to excitation displacement of vibration interference signals, M is the mass of the platform on the load, C is the equivalent damping of the vibration isolation platform, and K is the equivalent rigidity of the vibration isolation platform.
As shown in fig. 12 (b), the vibration isolation platform of the present invention is based on passive vibration isolation, and an active control loop is added. In the active control loop, the MFC sensor receives the vibration interference signal, and after the vibration interference signal is processed by the controller 11, the output control signal drives the MFC actuator to generate a corresponding actuating force, so as to suppress the vibration of the platform 1 on the load.
The active control method comprises three steps of receiving a vibration interference signal by a sensor, calculating the vibration interference signal by a controller 11 and outputting actuating power by an actuator. In the step of receiving the vibration interference signal by the sensor, the MFC sensor receives a vibration deformation signal of the load platform, converts the vibration deformation signal into a charge signal and transmits the charge signal to the controller; in the step of calculating the vibration interference signal by the controller 11, the controller 11 processes the transmitted vibration deformation signal through a control algorithm to obtain a real-time control signal and transmits the real-time control signal to the MFC actuator; in the step of outputting the actuating power by the actuator, the real-time control signal drives the MFC actuator to generate corresponding actuating power to act on the load platform to inhibit the vibration of the load platform.
As shown in FIG. 13, the amplitude (db) is plotted on the vertical axis and the frequency (Hz) is plotted on the horizontal axis. As can be seen from the comparison graph of the transmission rate curves, compared with the traditional passive vibration isolation, the passive vibration isolation has the advantages that the resonance peak value is reduced, the resonance frequency moves forward, the high-frequency attenuation is improved, the vibration isolation bandwidth is widened, and the vibration isolation effect is improved; when the vibration isolation platform is added with the active control loop of the active vibration isolation, the vibration isolation effect is further improved, and the resonance peak value is obviously improved.
In the description of the present invention, it should be noted that the terms "center", "top", "bottom", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the foregoing, the description is not to be taken in a limiting sense.
Claims (7)
1. The utility model provides a Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect which characterized in that: the vibration isolation device comprises a load upper platform and a base lower platform which are respectively in a triangular structure, wherein vertical projections of three angles of the load upper platform after the load upper platform horizontally rotates 120 degrees are superposed with vertical projections of three angles of the base lower platform, an upper rotating joint is fixedly connected to each of the three angular positions of the load upper platform, a lower rotating joint is connected to each of the three angular positions of the base lower platform, and six single-leg vibration isolation units are connected between the three upper rotating joints and the three lower rotating joints; each supporting beam of the upper loading platform is provided with three pairs of MFC piezoelectric fiber patches, each pair of MFC piezoelectric fiber patches comprises an MFC sensor and an MFC actuator, the MFC sensors and the MFC actuators in each pair of MFC piezoelectric fiber patches can be exchanged in roles, the MFC sensors and the MFC actuators are respectively and electrically connected with a controller through wires, and the plurality of MFC sensors and the MFC actuators are combined with the controller to realize active control of vibration reduction; the six single-leg vibration isolation units have the same structure; each single-leg vibration isolation unit comprises an upper end cover, a middle retainer and a lower end cover which are fixedly connected in sequence; a pressure spring type negative stiffness structure is arranged in the upper end cover, the top end of the pressure spring type negative stiffness structure penetrates through the upper end cover and is connected with an upper end flexible hinge, and the bottom of the lower end cover is fixedly connected with a lower end flexible hinge; two connecting flanges are fixedly arranged on the inner wall of the upper end cover; the pressure spring formula burden rigidity structure includes the three-way adapter, the both ends that the three-way adapter is located the below respectively through the pressure spring with connecting flange fixed connection on the upper end cover inner wall, the one end that the three-way adapter is located the top passes through pressure spring fixedly connected with bracing piece, the bracing piece runs through behind the upper end cover top with upper end flexible hinge fixed connection.
2. A Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect in claim 1, wherein: a connecting block is arranged on one side of the top of the upper rotating joint, two first connecting holes which are arranged in parallel are formed in the connecting block, two symmetrical inclined planes are formed in one side, close to the connecting block, of the upper rotating joint, two second connecting holes which are vertically arranged are formed in the two inclined planes, and the upper rotating joint is identical to the lower rotating joint in structure; the first connecting hole of the upper rotary joint is fixedly connected with the load upper platform through a screw, and the first connecting hole of the lower rotary joint is fixedly connected with the foundation lower platform through a screw.
3. A Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect in claim 2, wherein: the three upper rotary joints are respectively a first upper rotary joint, a second upper rotary joint and a third upper rotary joint, and the three lower rotary joints are respectively a first lower rotary joint, a second lower rotary joint and a third lower rotary joint; the six single-leg vibration isolation units are respectively a first single-leg vibration isolation unit, a second single-leg vibration isolation unit, a third single-leg vibration isolation unit, a fourth single-leg vibration isolation unit, a fifth single-leg vibration isolation unit and a sixth single-leg vibration isolation unit; the two second connecting holes of the first upper rotary joint are fixedly connected with the upper end flexible hinges of the first single-leg vibration isolation unit and the sixth single-leg vibration isolation unit respectively, the two second connecting holes of the second upper rotary joint are fixedly connected with the upper end flexible hinges of the second single-leg vibration isolation unit and the third single-leg vibration isolation unit respectively, and the two second connecting holes of the third upper rotary joint are fixedly connected with the upper end flexible hinges of the fourth single-leg vibration isolation unit and the fifth single-leg vibration isolation unit respectively; the two second connecting holes of the first lower adapter are fixedly connected with lower end flexible hinges of the first single-leg vibration isolation unit and the second single-leg vibration isolation unit respectively, the two second connecting holes of the second lower adapter are fixedly connected with lower end flexible hinges of the third single-leg vibration isolation unit and the fourth single-leg vibration isolation unit respectively, and the two second connecting holes of the third lower adapter are fixedly connected with lower end flexible hinges of the fifth single-leg vibration isolation unit and the sixth single-leg vibration isolation unit respectively.
4. A Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect in claim 1, wherein: the three MFC sensors arranged on each supporting beam of the load upper platform are respectively a first MFC sensor, a second MFC sensor and a third MFC sensor, and the three MFC actuators are respectively a first MFC actuator, a second MFC actuator and a third MFC actuator; the first MFC sensor and the first MFC actuator are symmetrically arranged on the upper surface and the lower surface of the load upper platform support beam, the second MFC sensor and the second MFC actuator are symmetrically embedded in the cross section of the load upper platform, and the third MFC sensor and the third MFC actuator are symmetrically arranged on the upper surface and the lower surface of the load upper platform support beam; the second MFC sensor and second MFC actuator are located at a position between the first MFC sensor and third MFC sensor.
5. A Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect in claim 1, wherein: the end faces of the upper end cover, the middle retainer and the lower end cover are respectively provided with symmetrical connecting threaded holes, long bolts penetrate through the connecting threaded holes, and the upper end cover, the middle retainer and the lower end cover are fixedly connected through the long bolts.
6. The Stewart vibration isolation platform based on MFC positive and reverse piezoelectric effect of claim 1, characterized in that: the load upper platform is of an isosceles triangle structure, horizontal connecting end faces are arranged at the outer sides of three corners of the load upper platform, the upper rotating joint is fixedly arranged at the horizontal connecting end faces, three reinforcing rods are arranged in the load upper platform, one ends of the three reinforcing rods are respectively connected with one corner of the load upper platform and are positioned on an bisector of the corner, and the other ends of the three reinforcing rods are fixedly connected at the position of the circle center of a circumscribed circle of the load upper platform; the base lower platform is of an isosceles triangle structure, a horizontal connection end face is arranged at the position of the outer side of three corners of the base lower platform, a lower rotary joint is fixedly arranged at the position of the horizontal connection end face, three reinforcing rods are arranged in the base lower platform, one end of each reinforcing rod is connected with one corner of the base lower platform and located on an equal dividing line of the corner, and the other end of each reinforcing rod is fixedly connected with the position of the circle center of an outer circle of the base lower platform.
7. A Stewart vibration isolation platform based on MFC positive and negative piezoelectric effect in claim 6, characterized in that: the width of the reinforcing rod of the load upper platform is smaller than that of the supporting beam of the load upper platform; the width of the reinforcing rod of the lower platform of the foundation is larger than that of the supporting beam of the lower platform of the foundation.
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