A precision active vibration isolation platform and a multi-degree-of-freedom decoupling control method thereof

Abstract

The application discloses a kind of precision active vibration isolation platform and multi-degree-of-freedom decoupling control method thereof, and relates to the field of active vibration control technology.The platform includes top plate, bottom plate, vibration isolator unit, wherein the vibration isolator unit contains base platform, bionic bird leg mechanism, helical spring assembly, load platform, speed sensor, Lorentz motor and control system.Bionic bird leg mechanism realizes nonlinear negative stiffness characteristic using link geometry buckling effect, helical spring provides vertical positive stiffness restoring force, and the vertical negative stiffness effect of bionic bird leg mechanism is superimposed, to form quasi-zero stiffness characteristic with vertical dynamic stiffness close to zero near rated load, speed sensor is arranged below top plate, Lorentz motor adopts redundant drive configuration, and control system realizes six-degree-of-freedom decoupling control through sensor conversion matrix and actuator conversion matrix, to implement absolute speed feedback control.The application has good vibration isolation effect, high multi-degree-of-freedom decoupling precision and strong robustness.

Description

Technical Field

[0001] This invention relates to the field of active vibration control technology, and in particular to a precision active vibration isolation platform and its multi-degree-of-freedom decoupling control method. Background Technology

[0002] In the fields of precision machining and high-end measurement equipment, environmental vibration is a key factor affecting the machining accuracy and measurement performance of equipment. Active vibration isolation technology reduces or eliminates the impact of vibration interference on the accuracy and performance of precision equipment by isolating and suppressing environmental micro-vibrations. Precision active vibration isolation systems not only need stronger vibration suppression capabilities but also need to attenuate vibrations over a wider frequency range. To achieve vibration attenuation over a wider frequency range, current mainstream precision vibration isolation systems combine passive vibration isolation with active control to fully leverage the advantages of both active vibration isolation at low frequencies and passive vibration isolation at high frequencies. In existing multi-degree-of-freedom active vibration isolation platforms, the configuration of sensors and actuators causes mutual interference between the vibration control of each degree of freedom direction in each sensor-actuator group.

[0003] In existing technologies, coordinate transformation is typically used to decouple the various degrees of freedom, and then individual degrees of freedom are controlled. This multi-degree-of-freedom decoupling control places high demands on the accuracy of the vibration isolation system's dynamic model and the configuration of sensors and actuators. For active vibration control in a single degree of freedom after decoupling, feedback control and feedforward control methods are commonly employed. Feedback control always lags behind the vibration of the isolated object, exhibiting an inherent time delay; while feedforward control can offset some of the influence of environmental vibrations, it requires strict accuracy in the disturbance transmission model. Therefore, for those skilled in the art, effectively suppressing environmental micro-vibrations and achieving six-degree-of-freedom motion coupling control is a pressing problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a precision active vibration isolation platform and its multi-degree-of-freedom decoupling control method to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following solution: On one hand, a precision active vibration isolation platform is provided, comprising a top plate, a bottom plate, and multiple vibration isolator units, wherein the vibration isolator units are connected to the top plate and the bottom plate; each vibration isolator unit includes a base platform, a helical spring assembly, a bionic bird leg mechanism, a speed sensor, a Lorentz motor, a load platform, and a control system; both ends of the helical spring assembly are connected to the base platform and the load platform respectively, both ends of the bionic bird leg mechanism are connected to the base platform and the load platform respectively, and the speed sensor is mounted below the load platform via a clamp.

[0006] Preferably, each leg of the bionic bird leg mechanism includes an upper link, a lower link, a connector, a fixing pin, and a hook spring. The upper link and the lower link are hinged together by the connector to form a flexible linkage mechanism. One end of the hook spring is connected to the fixing pin, and the other end is fixed to the connecting pin of the load platform or the base platform to provide lateral preload for the linkage mechanism.

[0007] By adopting the above technical solution, the following beneficial technical effects are achieved: The bionic bird leg mechanism utilizes the geometric buckling effect of the connecting rod to achieve nonlinear negative stiffness characteristics, forming a quasi-zero stiffness passive vibration isolation system in parallel with the hook spring and support spring. The bionic bird leg mechanism utilizes geometric nonlinearity to achieve vertical negative stiffness, working in conjunction with the positive stiffness helical spring assembly to achieve quasi-zero stiffness characteristics, effectively reducing the system's natural frequency and broadening the low-frequency vibration isolation bandwidth. The connection method of the hook spring effectively prevents lateral deformation of the connecting rod, ensuring high axial and radial stiffness of the bionic bird leg mechanism. The connection position of the hook spring and connecting rod in the bionic bird leg mechanism is adjustable. By adjusting the position of the fixed pin connected to the hole on the connecting rod, the position of the hook spring in the quasi-zero stiffness mechanism is adjustable, achieving nonlinear changes in negative stiffness force, thereby altering the system's natural frequency and providing adaptive adjustment capability for different load masses.

[0008] Preferably, the helical spring assembly is provided in multiple sets, and each set of the helical spring assembly includes a shim block, a clamping plate and a helical spring; wherein, the shim block is a cylindrical metal block with a circular groove on the upper end surface, bolt holes at both ends of the groove for fixing the clamping plate, and the bottom end is fixedly connected to the base platform; the upper end of the helical spring is embedded in the spring mounting seat at the bottom of the load platform, and the lower end is fixed to the shim block by the clamping plate.

[0009] By adopting the above technical solution, the following beneficial technical effects are achieved: The helical spring provides a vertical positive stiffness restoring force, which, combined with the vertical negative stiffness effect of the bionic bird leg mechanism, creates a quasi-zero stiffness characteristic with near-zero vertical dynamic stiffness near the rated load. This quasi-zero stiffness characteristic effectively reduces the vertical natural frequency of the passive vibration isolation system, thereby significantly widening the low-frequency bandwidth of passive vibration isolation. By selecting support springs of different strength specifications, different load masses can be accommodated, effectively improving the load-bearing capacity of the vibration damper. The function of the shim block is to reduce the natural length of the support spring, increase its tangential stiffness, and enhance the lateral stability of the system.

[0010] Preferably, the speed sensor includes a horizontal speed sensor and a vertical speed sensor. The horizontal speed sensor is used to measure the horizontal speed signal of the load platform, and the vertical speed sensor is used to measure the vertical speed signal of the load platform. The Lorentz motor includes a vertical Lorentz motor and a horizontal Lorentz motor. The coil and magnet are respectively mounted on the base platform and the load platform to achieve active vibration control.

[0011] Preferably, it also includes a fixing device, which includes a limiting post, a limiting lock ring, a bolt, and a limiting lock post; the load platform is fastened to the limiting post by bolts; the base plate is fixedly connected to the limiting lock post by bolts, the bottom end of the limiting post is fitted with the bolt, and the limiting lock ring is arranged on the lower side of the limiting lock post and fitted with the bolt.

[0012] Preferably, the control system includes a signal conditioning circuit, a main control unit, and a motor drive circuit.

[0013] Preferably, the signal conditioning circuit includes a differential amplifier unit, a first-order hysteresis compensation unit, a second-order hysteresis compensation unit, a high-pass filter unit, and an anti-aliasing filter unit cascaded in sequence; the differential amplifier unit is used to amplify the weak differential voltage signal output by the sensor and convert it into a single-ended signal; the first-order hysteresis compensation unit and the second-order hysteresis compensation unit use an extended filtering method to perform low-frequency extension on the speed sensor; the high-pass filter unit is used to eliminate the DC bias generated by the integration of low-frequency noise; the anti-aliasing filter unit is a second-order low-pass filter used to prevent frequency aliasing during signal sampling.

[0014] By adopting the above technical solution, the following beneficial technical effects are achieved: The speed sensor is extended to a lower frequency range using an extended filtering method. Through a two-stage first-order hysteresis compensation circuit, the effective measurement frequency band of the sensor is extended downwards, amplifying the low-frequency signal while maintaining the gain of the mid-to-high frequency signals. This enables the sensor to accurately acquire the low-frequency components of vibration, providing a high-quality low-frequency reference signal for control.

[0015] On the other hand, a multi-degree-of-freedom decoupling control method for a precision active vibration isolation platform is provided, the specific steps of which include the following:

[0016] The absolute vibration velocity signals of the load platform on each physical axis are obtained by a velocity sensor;

[0017] Using sensor conversion matrix The absolute vibration velocity signal is converted into a logic axis signal, and the logic axis signal corresponds to the vibration components in the six degrees of freedom directions respectively;

[0018] In the logical axis coordinate system, feedback controllers are designed independently for each degree of freedom direction, and the required control force for each degree of freedom direction is calculated.

[0019] Transformation matrix via actuator The control force is converted and distributed to the Lorentz motors of each physical axis, thereby achieving independent active control of each degree of freedom.

[0020] Preferably, the sensor conversion matrix The method for obtaining the data is as follows: Based on the geometric arrangement of the velocity sensors, a linear mapping relationship is established between the velocity measured by each sensor and the six-degree-of-freedom velocity vector of the top plate's center of mass under micro-vibration conditions.

[0021] ;

[0022] in, For measuring signal vectors from multiple sensors, The velocity vector has six degrees of freedom. , This is the sensor transformation matrix, whose coefficients are determined by the geometric distance parameter of the sensor installation position relative to the centroid.

[0023] Preferably, the actuator transformation matrix The method for obtaining the data is as follows: Based on the geometric arrangement of the Lorentz motors on the base platform, a force analysis is performed on the load platform to establish a linear mapping relationship between the output force vector F of each motor and the six-degree-of-freedom generalized force vector W acting on the center of mass of the load platform. The actuator transformation matrix is ​​obtained by solving under additional constraints. .

[0024] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0025] (1) It solves the problem of environmental micro-vibration and six-degree-of-freedom motion coupling faced by precision manufacturing and measurement equipment under actual working conditions. The sensor measurement signal of the physical axis is converted into the coordinate signal of the logical axis through the sensor conversion matrix. After the absolute velocity feedback control of each degree of freedom is implemented independently, the control force of the logical axis is distributed to the Lorentz motor of each physical axis through the actuator conversion matrix, so as to realize the six-degree-of-freedom decoupled control.

[0026] (2) A helical spring assembly and a biomimetic bird leg mechanism are used as the core components for passive load bearing and vibration isolation. The helical spring provides vertical positive stiffness restoring force, which is superimposed with the vertical negative stiffness effect of the biomimetic bird leg mechanism to form a quasi-zero stiffness characteristic with vertical dynamic stiffness close to zero near the rated load. The quasi-zero stiffness characteristic effectively reduces the vertical natural frequency of the passive vibration isolation system, thereby significantly widening the low-frequency bandwidth of the passive vibration isolation.

[0027] (3) Six-degree-of-freedom decoupled control is achieved through sensor conversion matrix and actuator conversion matrix, decoupling each degree of freedom into six independent ones, which can control the motion in each direction of the degree of freedom individually. The decoupling method establishes a linear mapping relationship based on the geometric arrangement of the sensors and the spatial installation position of the motor, which has a clear physical meaning and is easy to implement in engineering.

[0028] (4) This platform integrates multiple functions such as bionic bird leg mechanism, quasi-zero stiffness passive vibration isolation, multi-degree-of-freedom decoupling control, absolute speed feedback control, sensor low-frequency extension conditioning, motor precision drive, leveling, transportation locking, etc. It takes into account wide-band vibration isolation performance, multi-degree-of-freedom decoupling accuracy and engineering practicality, and its comprehensive performance and working condition adaptability are greatly improved. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a three-dimensional structural diagram of a precision active vibration isolation platform according to an embodiment of the present invention;

[0031] Figure 2 This is a front view of a precision active vibration isolation platform according to an embodiment of the present invention;

[0032] Figure 3 This is a three-dimensional structural diagram of the vibration isolator unit according to an embodiment of the present invention;

[0033] Figure 4 This is a front view of the vibration isolator unit according to an embodiment of the present invention;

[0034] Figure 5 This is an exploded view of a vibration isolator unit according to an embodiment of the present invention;

[0035] Figure 6 This is a three-dimensional structural diagram of the biomimetic bird leg mechanism in the vibration isolator unit of this invention.

[0036] Figure 7 This is a three-dimensional structural diagram of the helical spring assembly in the vibration isolator unit according to an embodiment of the present invention;

[0037] Figure 8(a) is a structural diagram of the fixing device according to an embodiment of the present invention;

[0038] Figure 8(b) is a three-dimensional structural diagram of the fixing device in the locked state according to an embodiment of the present invention;

[0039] Figure 8(c) is a three-dimensional structural diagram of the fixing device in the limiting state according to an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of the height adjustment structure according to an embodiment of the present invention;

[0041] Figure 10(a) is a simplified diagram of the horizontal sensor arrangement according to an embodiment of the present invention;

[0042] Figure 10(b) is a simplified diagram of the vertical sensor arrangement according to an embodiment of the present invention;

[0043] Figure 11(a) is a simplified diagram of the horizontal Lorentz motor arrangement according to an embodiment of the present invention;

[0044] Figure 11(b) is a simplified diagram of the vertical Lorentz motor arrangement according to an embodiment of the present invention;

[0045] Figure 12 This is a schematic diagram of a multi-degree-of-freedom decoupling control method according to an embodiment of the present invention;

[0046] Figure 13 This is a block diagram of the absolute speed sensor feedback control according to an embodiment of the present invention;

[0047] Figure 14(a) is a schematic diagram of the absolute speed sensor structure according to an embodiment of the present invention;

[0048] Figure 14(b) is a mechanical model diagram of the absolute velocity sensor according to an embodiment of the present invention;

[0049] Figure 15 is a block diagram of the components of the conditioning circuit according to an embodiment of the present invention;

[0050] Figure 16 This is a block diagram of the motor driver circuit according to an embodiment of the present invention;

[0051] Figure 17 This is a comparison diagram of the effects of the active vibration isolation platform of this invention relying solely on passive control versus introducing feedback control.

[0052] Explanation of reference numerals in the attached drawings: 1. Top plate; 2. Bottom plate; 3. Vibration isolator unit; 31. Load platform; 32. Base platform; 321. Upper plate of base platform; 322. Lower plate of base platform; 323. Double-ended screw; 33. Bionic bird leg mechanism; 331. Upper bearing support; 332. Lower bearing support; 333. Upper connecting rod; 334. Lower connecting rod; 335. Connecting piece; 336. Upper hook spring; 337. Lower hook spring; 34. Helical spring assembly; 341. Helical spring; 342. Clamping plate; 343. Elevating block; 35. Horizontal Lorentz motor; 351. Lorentz motor 352. First horizontal Lorentz motor clamp; 353. Second horizontal Lorentz motor clamp; 36. Vertical Lorentz motor; 361. Lorentz motor; 362. First vertical Lorentz motor clamp; 363. Second vertical Lorentz motor clamp; 37. Horizontal speed sensor; 371. Horizontal speed sensor clamp; 372. Speed ​​sensor; 38. Vertical speed sensor; 381. Vertical speed sensor clamp; 382. Speed ​​sensor; 39. Fixing device; 391. Limiting post; 392. Limiting lock ring; 393. Bolt; 394. Limiting lock post. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1

[0055] Embodiment 1 of this invention provides a precision active vibration isolation platform to address the problems of insufficient multi-degree-of-freedom motion coupling and broadband vibration attenuation capabilities in existing precision vibration isolation platforms. This invention employs a biomimetic bird leg mechanism and a helical spring assembly as the core components for passive vibration isolation and support. The biomimetic bird leg mechanism utilizes the geometric buckling of the connecting rod to achieve negative stiffness characteristics, while the helical spring provides vertical positive stiffness restoring force. These effects, combined with the vertical negative stiffness of the biomimetic bird leg mechanism, create a quasi-zero stiffness characteristic with near-zero vertical dynamic stiffness near the rated load. A Lorentz motor is used as the active actuator, and a speed sensor as the measuring element. Six-degree-of-freedom decoupled control is achieved through sensor conversion matrices and actuator conversion matrices. Absolute speed feedback control is used to increase system damping.

[0056] like Figure 1~Figure 2 As shown in 1(b), the precision active vibration isolation platform provided by the present invention includes a top plate 1, a bottom plate 2, and four vibration isolator units 3. The vibration isolator units 3 are arranged in a certain layout at the four corners of the platform and connected to the top plate 1 and the bottom plate 2. Each vibration isolator unit 3 includes a load platform 31, a base platform 32, a bionic bird leg mechanism 33, a helical spring assembly 34, a horizontal Lorentz motor 35, a vertical Lorentz motor 36, a horizontal velocity sensor 37, a vertical velocity sensor 38, a fixing device 39, and a control system.

[0057] In this specific embodiment, the base platform 32 consists of an upper plate 321, a lower plate 322, and a double-ended screw 323. Both the upper plate 321 and the lower plate 322 are rectangular parallelepipeds with mounting holes at their four corners. The two ends of the double-ended screw 323 are connected to the upper plate 321 and the lower plate 322 respectively via threaded holes. Countersunk holes are provided on the short sides of the upper plate 321, which are fixedly connected to the corresponding threaded holes on the lower plate 322 via fastening bolts. By rotating the double-ended screw 323 and the fastening bolts, the height of the base platform 32 can be adjusted, while ensuring that the base plane remains horizontal. When four vibration isolator units 3 are used together, the height of each unit can be adjusted uniformly, achieving coordinated control of the overall height and levelness of the platform.

[0058] The biomimetic bird leg mechanism 33 is the core passive vibration isolation element of the vibration isolator unit 3, including an upper connecting rod 333, a lower connecting rod 334, a connecting piece 335, an upper hook spring 336, a lower hook spring 337, an upper bearing support 331, and a lower bearing support 332. The upper end of the upper connecting rod 333 of each leg of the biomimetic bird leg mechanism is hinged to the load platform 31 via the upper bearing support 331, and the lower end of the lower connecting rod 334 is hinged to the base platform 32 via the lower bearing support 332. The upper connecting rod 333 and the lower connecting rod 334 are hinged together via the connecting piece 335 to form a bendable linkage mechanism. The biomimetic bird leg mechanism has four legs in total, and eight hook springs in total (two hook springs for each leg, i.e., four upper hook springs 336 and four lower hook springs 337). One end of the hook spring is connected to a fixing pin on the connecting rod, and the other end is fixed to a connecting pin on the load platform 31 or the base platform 32. This provides lateral preload to the linkage mechanism, preventing lateral instability deformation of the upper connecting rod 333 and the lower connecting rod 334 during buckling, thus ensuring the structural stability of the linkage mechanism under vertical load. When the load platform 31 bears a vertical load, the upper connecting rod 333 and the lower connecting rod 334 rotate relative to each other around the connecting member 335. During large geometric deformation, the linkage mechanism generates a nonlinear buckling effect, resulting in a negative vertical stiffness characteristic. By adjusting the mounting hole position of the fixing pin on the connecting rod, the lever arm of the hook spring on the connecting member 335 can be changed, thereby altering the buckling critical load and the magnitude of the negative stiffness characteristic of the linkage mechanism, providing adaptive adjustment capability for different load masses.

[0059] The helical spring assembly 34 consists of four groups, each comprising a shim block 343, a clamping plate 342, and a helical spring 341. The shim block 343 is a cylindrical metal block with a circular groove on its upper surface. Bolt holes at both ends of the groove are used to fix the clamping plate 342, and its bottom end is fixedly connected to the base platform 32. The helical spring 341 is a cylindrical helical compression spring. Its upper end is embedded in a spring mounting seat at the bottom of the load platform 31, and its lower end is fixed to the shim block 343 via the clamping plate 342. The helical spring 341 provides a vertical positive stiffness restoring force, which, combined with the vertical negative stiffness effect of the bionic bird leg mechanism 33, creates a quasi-zero stiffness characteristic with near-zero vertical dynamic stiffness near the rated load. This quasi-zero stiffness characteristic effectively reduces the vertical natural frequency of the passive vibration isolation system, thereby significantly widening the low-frequency bandwidth of the passive vibration isolation. By selecting support springs of different strength specifications, different load masses can be accommodated, effectively improving the load-bearing capacity of the vibration damper. The function of the shim block 343 is to reduce the natural length of the support spring, increase its tangential stiffness, and enhance the lateral stability of the system.

[0060] Eight speed sensors are arranged below the load platform 31, implemented by clamps fixed below the load platform 31. Four vertical speed sensors 38 (including clamps 381 and sensor 382) and four horizontal speed sensors 37 (including clamps 371 and sensor 372) are arranged, respectively used to measure the horizontal and vertical speed signals of the load platform 31. Speed ​​sensors 372 and 382 are selected as magnetoelectric absolute speed sensors (ground sound sensors), whose mechanical model can be simplified to a second-order system consisting of mass-spring-damping. The speed sensors utilize Faraday's law of electromagnetic induction to convert the relative velocity between the mass block wound with a coil and the permanent magnet fixed to the outer shell into a voltage signal output.

[0061] Eight Lorentz motors are arranged in total, including four vertical Lorentz motors 36 and four horizontal Lorentz motors 35, which are used to output control forces in the horizontal and vertical directions to achieve active vibration control. The vertical Lorentz motors 36 include a Lorentz motor 361, a first vertical Lorentz motor clamp 362, and a second vertical Lorentz motor clamp 363; the horizontal Lorentz motors 35 include a Lorentz motor 351, a first horizontal Lorentz motor clamp 352, and a second horizontal Lorentz motor clamp 353. The coils and magnets are mounted on the base platform 32 and the load platform 31, respectively, and are mechanically separated. The magnitude of the Lorentz force generated by the Lorentz motor is proportional to the coil current; the thrust generated by the motor can be adjusted by changing the input current of the coil. The horizontal motors adopt a push-pull opposing mounting method, eliminating the additional torque introduced by a single motor applying force.

[0062] In each vibration isolator unit 3, the speed sensor and the Lorentz motor are arranged in the same way. In the precision active vibration isolation platform provided by the present invention, four identical vibration isolator units 3 are used in common, placed clockwise in a certain layout, and installed between the top plate 1 and the bottom plate 2.

[0063] As shown in Figure 8(a), the fixing device 39 includes a limiting post 391, a limiting lock ring 392, a bolt 393, and a limiting lock post 394. The load platform 31 is fastened to the limiting post 391 by bolts; the base plate 2 is also fastened to the limiting lock post 394 by bolts. The bottom end of the limiting post 391 is fitted with the bolt 393, and the limiting lock ring 392 is arranged on the lower side of the limiting lock post 394 and is fitted with the bolt 393. When the limiting lock ring 392 and the bolt 393 are installed, adjusting the bolt 393 can put the shock absorber in a pre-tightened state (locked state, as shown in Figure 8(b)), thereby reducing the wear on the stiffness elements in the shock absorber during transportation and mitigating the impact of the load being in place. When the limit lock ring 392 and bolt 393 are not installed, the limit pin 391 passes through the limit lock pin 394 (limited state, as shown in Figure 8(c)), fixing the horizontal position of the shock absorber, thereby realizing the horizontal limit function and ensuring the horizontal stability of the shock absorber when it is in operation.

[0064] Example 2

[0065] Embodiment 2 of the present invention provides a multi-degree-of-freedom decoupling control method for a precision active vibration isolation platform, which is applied to the control system of the aforementioned precision active vibration isolation platform, such as... Figure 12 As shown, it includes the following steps:

[0066] S1. Obtain the absolute vibration velocity signals of the load plane on each physical axis through a velocity sensor;

[0067] S2. Use the sensor conversion matrix to convert the measured physical axis absolute velocity signal into a logical axis signal. The logical axis signals correspond to the vibration components in the six degrees of freedom (three translational components and three rotational components).

[0068] S3. In the logical axis coordinate system, design feedback controllers independently for each degree of freedom direction and calculate the control force required for each degree of freedom direction.

[0069] S4. The control force of each logical axis is converted and distributed to the Lorentz motor of each physical axis through the actuator conversion matrix, so as to realize independent active control of each degree of freedom.

[0070] Sensor conversion matrix The solution method is as follows: Based on the geometric relationship of the velocity sensor arrangement, a linear mapping relationship is established between the velocity measured by each sensor and the six-degree-of-freedom velocity vector of the top plate's center of mass under micro-vibration conditions:

[0071] ;

[0072] in, For measuring signal vectors from multiple sensors, The velocity vector has six degrees of freedom. , This is the sensor transformation matrix, whose coefficients are determined by the geometric distance parameter of the sensor's mounting position relative to the centroid. The sensor transformation matrix depends only on the platform's geometric dimensions, does not contain frequency-dependent terms, has low computational complexity, and is suitable for embedded real-time control.

[0073] Actuator Transition Matrix The solution method is as follows: Based on the geometric arrangement of the eight Lorentz motors on the base platform 32, a force analysis is performed on the load platform 31, establishing a linear mapping relationship between the output force vector F (8×1) of each motor and the six-degree-of-freedom generalized force vector W (6×1) acting on the center of mass of the load platform 31. Since the eight motors provide redundant drive for the six degrees of freedom, to ensure the uniqueness of the solution, an additional constraint is added: the sum of the output forces of the vertical actuators arranged at the two diagonals is equal. And the sum of the output forces of the horizontal actuators are equal. The actuator transformation matrix is ​​obtained by solving under additional constraints. (8×6), satisfying Sensor conversion matrix By forming a dual relationship with the motor force distribution matrix, geometric decoupling from sensor signals to motor force commands can be directly achieved without introducing complex dynamic decoupling algorithms, thus simplifying controller design.

[0074] like Figure 13 As shown, the feedback controller employs an absolute velocity feedback control method, where the actuator generates an active damping force proportional to the absolute vibration velocity of the load platform 31. The feedback controller consists of a cascaded high-pass filter, a leadlag filter, a PID filter, a note filter, and a low-pass filter. The high-pass filter has a cutoff frequency of approximately 0.1 Hz and is used to attenuate ultra-low frequency noise; the leadlag filter reduces low-frequency phase lead to increase the upper limit of the control gain; the note filter attenuates gain spikes at specific frequencies caused by load dynamics to ensure system amplitude margin; and the low-pass filter has a cutoff frequency of approximately 150 Hz and is used to limit the active control bandwidth. In designing the feedback controller, the theoretical system model was modified by superimposing the dynamic characteristics of the sensors and the inherent delay of the control system (control period approximately 0.5 ms) onto the theoretical second-order system model. Absolute velocity feedback control increases system damping and suppresses resonance peaks while maintaining a good high-frequency vibration attenuation rate.

[0075] Figure 14(a) shows a schematic diagram of the selected velocity sensor structure. As a device for measuring absolute velocity, this sensor is a magnetoelectric velocity sensor. Its principle is to use Ferrari's law of electromagnetic induction to convert the relative velocity between a mass block with a coil wound around it and a permanent magnet fixed to the outer shell into a voltage signal output. Because it is often used to measure ground vibrations, it is also called a ground sound sensor. As shown in Figure 14(b), the mechanical model of the selected velocity sensor can be simplified to a second-order system consisting of a spring-mass-damping system (mass m, stiffness k, and damping coefficient c).

[0076] As shown in Figure 15, the signal conditioning circuit includes a differential amplifier, a first-order hysteresis compensation stage, a second-order hysteresis compensation stage, a high-pass filter, and an anti-aliasing filter, all cascaded together. The differential amplifier amplifies the weak differential voltage signal output from the sensor and converts it into a single-ended signal. The first and second-order hysteresis compensation stages use extended filtering to extend the low-frequency band of the speed sensor, extending the sensor system's natural frequency downwards while maintaining signal gain in the mid-to-high frequency range. The high-pass filter eliminates the DC bias generated by low-frequency noise integration. The anti-aliasing filter is a second-order low-pass filter used to prevent frequency aliasing during signal sampling. By extending the effective measurement frequency band of the sensor downwards through two stages of first-order hysteresis compensation, and amplifying the low-frequency signal while maintaining mid-to-high frequency signal gain, the sensor can accurately acquire the low-frequency components of vibration, providing a high-quality low-frequency reference signal for control.

[0077] like Figure 16 As shown, the motor drive circuit includes a PI control circuit, a drive circuit, and a current detection circuit. The drive circuit adopts a linear differential drive method, using an audio power operational amplifier as the driver chip, with differential output amplification factors of ±21 times for the positive and negative terminals, respectively. The current detection circuit connects precision sampling resistors in series at the positive and negative terminals of the motor. After amplification by the differential operational amplifier and conversion from dual-ended to single-ended, the current feedback signal is sent back to the PI control circuit. The PI control circuit adjusts the drive signal input based on the deviation between the current detection signal and the control signal, forming a current closed-loop control to improve the control accuracy of the output current. The drive bandwidth and current accuracy meet the vibration isolation control requirements.

[0078] The main control unit uses an NI PXI-8106 embedded controller, running the LabVIEW-RT real-time operating system for multitasking. The signal acquisition module uses an NI PXI-6123 data acquisition card, featuring 8 independent channels, 16-bit A / D conversion, and a sampling rate of 500 kS / s. The signal output module uses an NI PXI-6733 analog output card, with 8 channels, a conversion rate of 1 MS / s, and 16-bit output resolution. The host computer and main control unit are connected via Ethernet. The main control unit sends the real-time status of the vibration isolation system to the host computer for display, and the host computer can also modify the controller's control parameters in real time.

[0079] Figure 17 The vibration transmissibility curve is obtained by comparing the platform vibration signal with the foundation vibration signal (i.e., response and excitation). Figure 17 In the diagram, the black curve represents the vibration transmissibility curve without feedback control, where only the passive vibration isolation structure is in effect; the gray curve represents the vibration transmissibility curve after feedback control is introduced. Figure 17 As shown, the control bandwidth of this vibration isolation platform is 1~100Hz, the vibration transmissibility curve crosses zero around 1Hz, the vibration attenuation is -5 to -10dB at 2Hz, and the vibration attenuation is -30dB at 20Hz and above. A quasi-zero stiffness passive vibration isolation system, formed by the parallel connection of a biomimetic bird leg mechanism 33 and a helical spring assembly 34, achieves near-zero stiffness characteristics with a vertical dynamic stiffness close to zero near the rated load, effectively broadening the low-frequency bandwidth of passive vibration isolation. Through a Lorentz motor and absolute velocity feedback control, efficient active vibration attenuation is achieved within the 1~100Hz frequency range. The spatial geometric decoupling layout of the sensors and motors reduces the cross-coupling between degrees of freedom at the physical structure level. Three non-collinearly arranged vertical sensors and two opposing horizontal sensors are sufficient to achieve real-time calculation of all six degrees of freedom vibration states.

[0080] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A precision active vibration isolation platform, characterized in that, The system includes a top plate, a bottom plate, and multiple vibration isolator units, which are connected to the top plate and the bottom plate. Each vibration isolator unit includes a base platform, a helical spring assembly, a bionic bird leg mechanism, a speed sensor, a Lorentz motor, a load platform, and a control system. The two ends of the helical spring assembly are connected to the base platform and the load platform, respectively. The two ends of the bionic bird leg mechanism are connected to the base platform and the load platform, respectively. The speed sensor is mounted below the load platform via a clamp.

2. The precision active vibration isolation platform according to claim 1, characterized in that, The biomimetic bird leg mechanism includes an upper link, a lower link, a connector, a fixing pin, and a hook spring. The upper link and the lower link are hinged together by the connector to form a flexible linkage mechanism. One end of the hook spring is connected to the fixing pin, and the other end is fixed to the connecting pin of the load platform or the base platform to provide lateral preload for the linkage mechanism.

3. The precision active vibration isolation platform according to claim 1, characterized in that, The helical spring assembly is provided in multiple sets, and each set of the helical spring assembly includes a shim block, a clamping plate and a helical spring; wherein, the shim block is a cylindrical metal block with a circular groove on the upper end surface, bolt holes at both ends of the groove for fixing the clamping plate, and the bottom end is fixedly connected to the base platform; the upper end of the helical spring is embedded in the spring mounting seat at the bottom of the load platform, and the lower end is fixed to the shim block by the clamping plate.

4. The precision active vibration isolation platform according to claim 1, characterized in that, The speed sensor includes a horizontal speed sensor and a vertical speed sensor. The horizontal speed sensor is used to measure the horizontal speed signal of the load platform, and the vertical speed sensor is used to measure the vertical speed signal of the load platform. The Lorentz motor includes a vertical Lorentz motor and a horizontal Lorentz motor. The coil and magnet are respectively mounted on the base platform and the load platform to achieve active vibration control.

5. A precision active vibration isolation platform according to claim 1, characterized in that, It also includes a fixing device, which includes a limiting post, a limiting lock ring, a bolt, and a limiting lock post; the load platform is fastened to the limiting post by bolts; the base plate is fixedly connected to the limiting lock post by bolts, the bottom end of the limiting post is fitted with the bolt, and the limiting lock ring is arranged on the lower side of the limiting lock post and fitted with the bolt.

6. The precision active vibration isolation platform according to claim 1, characterized in that, The control system includes a signal conditioning circuit, a main control unit, and a motor drive circuit.

7. A precision active vibration isolation platform according to claim 6, characterized in that, The signal conditioning circuit includes a differential amplifier unit, a first-order hysteresis compensation unit, a second-order hysteresis compensation unit, a high-pass filter unit, and an anti-aliasing filter unit cascaded in sequence. The differential amplifier unit amplifies the weak differential voltage signal output by the sensor and converts it into a single-ended signal. The first-order hysteresis compensation unit and the second-order hysteresis compensation unit use an extended filtering method to perform low-frequency extension on the speed sensor. The high-pass filter unit is used to eliminate the DC bias generated by the integration of low-frequency noise. The anti-aliasing filter unit is a second-order low-pass filter used to prevent frequency aliasing during signal sampling.

8. A multi-degree-of-freedom decoupling control method for a precision active vibration isolation platform, characterized in that, The specific steps include the following: The absolute vibration velocity signals of the load platform on each physical axis are obtained by a velocity sensor; Using sensor conversion matrix The absolute vibration velocity signal is converted into a logic axis signal, and the logic axis signal corresponds to the vibration components in the six degrees of freedom directions respectively; In the logical axis coordinate system, feedback controllers are designed independently for each degree of freedom direction, and the required control force for each degree of freedom direction is calculated. Transformation matrix via actuator The control force is converted and distributed to the Lorentz motors of each physical axis, thereby achieving independent active control of each degree of freedom.

9. The multi-degree-of-freedom decoupling control method for a precision active vibration isolation platform according to claim 8, characterized in that, The sensor conversion matrix The method for obtaining the data is as follows: Based on the geometric arrangement of the velocity sensors, a linear mapping relationship is established between the velocity measured by each sensor and the six-degree-of-freedom velocity vector of the top plate's center of mass under micro-vibration conditions. ； in, For measuring signal vectors from multiple sensors, The velocity vector has six degrees of freedom. , This is the sensor transformation matrix, whose coefficients are determined by the geometric distance parameter of the sensor installation position relative to the centroid.

10. The multi-degree-of-freedom decoupling control method for a precision active vibration isolation platform according to claim 8, characterized in that, The actuator transformation matrix The method for obtaining the data is as follows: Based on the geometric arrangement of the Lorentz motors on the base platform, a force analysis is performed on the load platform to establish a linear mapping relationship between the output force vector F of each motor and the six-degree-of-freedom generalized force vector W acting on the center of mass of the load platform. ; The actuator transformation matrix is ​​obtained by solving under additional constraints. .

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