A Permanent Magnet Negative Stiffness Active Absolute Velocity Sensor and Its Control Method

Abstract

The present invention provides a permanent magnet negative stiffness active absolute velocity sensor and its control method, belonging to the field of velocity detection. The absolute velocity sensor includes: a housing, an actuator, a permanent magnet negative stiffness component, an elastic component, a shaft, a reference mass, a relative displacement sensor, and a control component. The housing is fixed to the object to be measured; the actuator and the permanent magnet negative stiffness component are arranged inside the housing; the shaft sequentially passes through the actuator, the permanent magnet negative stiffness component, the upper surface of the housing, and the elastic component from bottom to top; the relative displacement sensor measures the relative displacement between the housing and the shaft; the control component generates a feedback control signal according to the relative displacement, and the actuator suppresses the movement of the reference mass under the action of the feedback control signal, thereby converting the relative displacement signal into the absolute velocity signal of the object to be measured. The natural frequency of the absolute velocity sensor is reduced, the displacement of the reference mass is decreased, and the stability and low-frequency performance of the absolute velocity sensor are improved.

Description

Technical Field

[0001] The present invention relates to the field of speed detection, and in particular, to a permanent magnet negative stiffness active absolute speed sensor and a control method thereof. Background Art

[0002] A precision vibration isolation system is the fundamental guarantee for the stable operation of ultra-precision manufacturing and measuring equipment. As the equipment enters the nano / sub-nano accuracy range, the demand for high-performance vibration isolation becomes more urgent. Reducing the natural frequency of the vibration isolation system and introducing active vibration control have become the main means to improve the vibration isolation performance. Inertial sensors represented by acceleration and absolute speed measurement are the key devices for realizing active vibration isolation. However, applying active control in a vibration isolation system with a low natural frequency poses higher requirements for the low-frequency measurement ability of inertial sensors, especially absolute speed sensors.

[0003] Currently, small commercial absolute speed sensors mainly include a housing and a permanent magnet fixedly connected thereto, an inertial reference mass with a coil wrapped around and sleeved on the permanent magnet, and a metal spring that supports between the mass and the housing, etc. When the housing is affected by external vibration, relative movement occurs between the housing and the reference mass, and the induced coil cuts the magnetic field lines to generate a voltage proportional to the absolute speed of the housing within a certain bandwidth. The transfer function from the external speed input of the absolute speed sensor to the sensor voltage output exhibits a high-pass characteristic, and its cut-off frequency is determined by the internal mechanical spring and the inertial reference mass. By analyzing the structural composition characteristics of the absolute speed sensor, it can be seen that increasing the reference mass and reducing the stiffness of the metal spring can reduce the low-frequency cut-off frequency of the sensor, thereby enhancing its low-frequency performance. However, increasing the reference mass will significantly increase the volume of the sensor; according to the definition of stiffness, an increase in bearing capacity or a decrease in stiffness will cause a rapid increase in the deformation amount, which will also correspondingly increase the volume of the sensor, both of which will lead to difficulties in sensor design and integration. In addition, reducing the stiffness of the metal spring will reduce the system stability, narrow its linear displacement range, and cause the sensor to exhibit non-linear response.

[0004] In order to further improve the low-frequency performance of the absolute speed sensor and overcome the deficiencies of common metal springs, a concept of using a permanent magnet to construct a permanent magnet negative stiffness spring to replace the metal spring to reduce the stiffness and expand the low-frequency performance of the sensor has been proposed. However, since the spatial magnetic field strength is strongly non-linearly correlated with the relative position between the magnets forming the magnetic field, and the reference mass carried by the permanent magnet negative stiffness spring and the sensor housing continuously change with different vibration inputs, causing changes in the spatial magnetic field, resulting in non-linear changes in the negative stiffness magnetic force and the output of the induced coil, seriously affecting the measurement performance of the absolute speed sensor.

[0005] In addition, by using a configuration with a combination of a coil winding and a permanent magnet, negative stiffness can be generated, reducing the natural frequency of the system and improving the linearity of the stiffness range of the electromagnetic negative stiffness mechanism. However, such mechanisms require a continuous power supply. In particular, the coil winding needs to be driven by a constant current to generate stable negative stiffness, and the high heat generation of the coil winding is inevitable. The continuous heat generation will cause changes in the resistance characteristics of the coil winding itself, affecting the output accuracy of the electromagnetic force. At the same time, the heat generation causes the surrounding environment to heat up, which is not conducive to the control of the low-frequency thermal noise of the inertial sensor. Moreover, when there is a misalignment installation problem between the electromagnetic negative stiffness mechanism and the metal spring, the initial acting force of the negative stiffness mechanism will cause further drift of the reference mass. Summary of the Invention

[0006] The object of the present invention is to provide a permanent magnet negative stiffness active absolute velocity sensor and its control method, which can improve the stability and low-frequency performance of the absolute velocity sensor.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A permanent magnet negative stiffness active absolute velocity sensor for measuring the absolute velocity of a measured object, the permanent magnet negative stiffness active absolute velocity sensor comprising:

[0009] A housing, the lower surface of which is fixedly arranged on the measured object;

[0010] An actuator, arranged inside the housing;

[0011] A permanent magnet negative stiffness component, arranged inside the housing;

[0012] An elastic component, fixedly arranged on the upper surface of the housing;

[0013] A shaft, sequentially passing through the actuator, the permanent magnet negative stiffness component, the upper surface of the housing and the elastic component from bottom to top, and the bottom of the shaft is suspended inside the housing;

[0014] A reference mass block, fixedly arranged on the top of the shaft;

[0015] A relative displacement sensor, fixedly arranged on the upper surface of the housing, for measuring the relative displacement between the reference mass block and the upper surface of the housing to obtain a relative displacement signal;

[0016] A control component, connected to the relative displacement sensor and the actuator, for generating a feedback control signal according to the relative displacement signal;

[0017] The execution component is used to suppress the relative movement between the reference mass block and the housing under the action of the feedback control signal; the relative displacement signal is determined by feedback control to obtain the absolute velocity of the measured object.

[0018] Optionally, the execution component includes: a magnet and a coil;

[0019] The magnet is suspended inside the housing, fixed to the shaft, and has a groove formed in its lower part;

[0020] The coil is disposed in the groove of the magnet, fixedly connected to the bottom of the housing, and connected to the control component;

[0021] The feedback control signal is used to control the magnitude of the current applied to the coil.

[0022] Optionally, the execution component is a voice coil motor.

[0023] Optionally, the permanent magnet negative stiffness component includes a first permanent magnet ring, a second permanent magnet ring, a third permanent magnet ring, and a fourth permanent magnet ring;

[0024] The first permanent magnet ring, the second permanent magnet ring, the third permanent magnet ring, and the fourth permanent magnet ring have the same axis; the shaft passes through the axes of the first permanent magnet ring, the second permanent magnet ring, the third permanent magnet ring, and the fourth permanent magnet ring;

[0025] The first permanent magnet ring and the second permanent magnet ring have the same inner and outer diameters, the third permanent magnet ring and the fourth permanent magnet ring have the same inner and outer diameters, and the inner diameter of the third permanent magnet ring is greater than the outer diameter of the first permanent magnet ring;

[0026] The first permanent magnet ring and the second permanent magnet ring are fixed on the shaft, and the lower surface of the first permanent magnet ring is fixedly connected to the upper surface of the second permanent magnet ring;

[0027] The third permanent magnet ring and the fourth permanent magnet ring are both fixedly connected to the housing, and the third permanent magnet ring and the fourth permanent magnet ring are separated by a set axial gap.

[0028] Optionally, the first permanent magnet ring, the second permanent magnet ring, the third permanent magnet ring, and the fourth permanent magnet ring have the same axial height.

[0029] Optionally, the elastic component is a metal spring.

[0030] Optionally, the permanent magnet negative stiffness active absolute velocity sensor further includes an air bearing guide rail;

[0031] The air bearing guide rail is fixed inside the housing; the shaft passes through the air bearing guide rail; the air bearing guide rail is used to restrict the movement direction of the shaft.

[0032] Optionally, the permanent magnet negative stiffness active absolute velocity sensor further includes an axial adjusting nut;

[0033] The axial adjusting nut is arranged between the reference mass block and the elastic component; the shaft passes through the axial adjusting nut; the axial adjusting nut is used to adjust the initial position of the shaft.

[0034] To achieve the above object, the present invention also provides the following solution:

[0035] A control method for a permanent magnet negative stiffness active absolute velocity sensor, comprising:

[0036] Fix the lower surface of the housing on the object to be measured;

[0037] When the object to be measured moves, under the action of the shaft, the reference mass block is displaced, and the relative displacement between the reference mass block and the upper surface of the housing is collected by a relative displacement sensor to obtain a relative displacement signal;

[0038] Generate a feedback control signal according to the relative displacement signal, and control the actuator to suppress the relative movement between the reference mass block and the housing; the absolute velocity of the object to be measured is determined after the relative displacement signal is feedback-controlled.

[0039] Optionally, the actuator is a voice coil motor;

[0040] The generating a feedback control signal according to the relative displacement signal and controlling the actuator to suppress the relative movement between the reference mass block and the housing specifically includes:

[0041] Convert the relative displacement signal into a voltage signal according to the gain of the relative displacement sensor and the corner frequency of the relative displacement sensor;

[0042] Determine a control voltage signal according to the voltage signal by using a differential controller, a low-frequency stability filter, a differential intensity adjustment filter and a high-frequency dynamic suppression filter;

[0043] Determine a feedback control signal according to the thrust constant of the voice coil motor, the gain of the drive circuit, the corner frequency of the drive circuit and the control voltage signal; the feedback control signal is used to control the magnitude of the current applied to the voice coil motor; the voice coil motor suppresses the relative movement between the reference mass block and the housing under the action of the feedback control signal; the absolute velocity of the object to be measured is determined after the relative displacement signal is feedback-controlled.

[0044] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: The lower surface of the housing is fixed on the object to be measured. The actuating component and the permanent magnet negative stiffness component are both arranged inside the housing. The shaft sequentially passes through the actuating component, the permanent magnet negative stiffness component, the upper surface of the housing, and the elastic component from bottom to top, and the bottom of the shaft floats inside the housing. The reference mass block is arranged at the top of the shaft. The relative displacement between the reference mass block and the upper surface of the housing is measured by the relative displacement sensor, and the absolute velocity of the object to be measured is determined after feedback control. The design of the permanent magnet negative stiffness component reduces the natural frequency of the absolute velocity sensor and avoids the problem of constant current heating of the electromagnetic negative stiffness. The feedback control signal is generated by the control component to perform feedback control on the actuating component, reducing the displacement of the reference mass block, suppressing the problem of magnetic force nonlinearity, and improving the stability and low-frequency performance of the absolute velocity sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 It is the front view of the permanent magnet negative stiffness active absolute velocity sensor of the present invention;

[0047] Figure 2 It is the simplified sectional view of the permanent magnet negative stiffness active absolute velocity sensor of the present invention;

[0048] Figure 3 It is the schematic diagram of the magnetization direction of the permanent magnet ring in the permanent magnet negative stiffness component;

[0049] Figure 4 It is the schematic diagram of the control framework of the permanent magnet negative stiffness active absolute velocity sensor of the present invention;

[0050] Figure 5 It is the schematic diagram of the feedback control strategy;

[0051] Figure 6 It is the schematic diagram of the frequency response of the feedback control strategy;

[0052] Figure 7 It is the flowchart of the control method of the permanent magnet negative stiffness active absolute velocity sensor of the present invention.

[0053] Symbol Description:

[0054] Relative displacement sensor - 1, reference mass - 2, linear displacement guide - 3, shaft - 4, axial adjusting nut - 5, metal spring - 6, first air - bearing guide - 7, second air - bearing guide - 8, permanent - magnet negative - stiffness component - 9, voice - coil motor - 10, housing - 11, first permanent - magnet ring - 12, second permanent - magnet ring - 13, third permanent - magnet ring - 14, fourth permanent - magnet ring - 15, magnet - 16, coil - 17, object to be measured - 18. Detailed implementation mode

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] The purpose of the present invention is to provide a permanent - magnet negative - stiffness active absolute - velocity sensor and its control method. The permanent - magnet negative - stiffness component reduces the natural frequency of the absolute - velocity sensor and avoids the problem of constant - current heating of electromagnetic negative stiffness. By generating a feedback control signal through the control component to perform feedback control on the actuator, the displacement of the reference mass is reduced, the problem of magnetic - force non - linearity is suppressed, and the stability and low - frequency performance of the absolute - velocity sensor are improved.

[0057] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation modes.

[0058] As Figure 1 and Figure 2 shown, the permanent - magnet negative - stiffness active absolute - velocity sensor of the present invention includes: housing 11, actuator, permanent - magnet negative - stiffness component 9, elastic component, shaft 4, reference mass 2, relative displacement sensor 1, and control component.

[0059] Among them, the lower surface of the housing 11 is fixedly arranged on the object to be measured 18. In this embodiment, the housing 11 is fixed to the object to be measured 18 through screw holes, so that the motion states of the object to be measured 18 and the housing 11 are completely the same. The object to be measured 18 moves freely, and the present invention measures the velocity value of the object to be measured 18 in the axial direction of the sensor shaft 4.

[0060] The actuator and the permanent magnet negative stiffness component 9 are disposed inside the housing 11. In this embodiment, the actuator is a voice coil motor 10. The voice coil motor 10 serves as an actuator for active control. The actuator includes a magnet 16 and a coil 17. The magnet 16 is suspended inside the housing 11, fixed to the shaft 4, and has a groove formed in its lower part. The coil 17 is disposed in the groove of the magnet 16, fixedly connected to the bottom of the housing 11, and connected to the control component.

[0061] The elastic component is fixedly disposed on the upper surface of the housing 11. In this embodiment, the elastic component is a metal spring 6.

[0062] The shaft 4 passes through the actuator, the permanent magnet negative stiffness component 9, the upper surface of the housing 11, and the elastic component in sequence from bottom to top, and the bottom of the shaft 4 is suspended inside the housing 11.

[0063] The reference mass 2 is fixedly disposed on the top of the shaft 4.

[0064] The relative displacement sensor 1 is fixedly disposed on the upper surface of the housing 11. The relative displacement sensor 1 is used to measure the relative displacement between the reference mass 2 and the upper surface of the housing 11 to obtain a relative displacement signal.

[0065] The control component is connected to the relative displacement sensor 1 and the actuator. The control component is used to generate a feedback control signal according to the relative displacement signal. The actuator is used to suppress the relative movement between the reference mass 2 and the housing 11 under the action of the feedback control signal. The relative displacement signal is used to determine the absolute velocity of the measured object after feedback control. In this embodiment, the relative displacement signal is converted into an absolute velocity signal of the measured object through feedback control. Specifically, the feedback control signal is used to control the magnitude of the current applied to the voice coil motor coil.

[0066] Specifically, when the measured object moves axially, it drives the housing to move axially. The housing pushes the shaft to move axially through the spring. At this time, the movements of the housing and the shaft are not synchronous. The relative displacement sensor measures the relative displacement between the housing and the shaft and outputs a voltage signal proportional to the relative displacement. The control component obtains a feedback control signal according to the voltage signal, transmits it to the actuator to generate a feedback effect, and further affects the voltage signal output by the displacement sensor. After countless times of feedback control, when the voltage signal output by the displacement sensor is equal to the voltage signal generated by the combined action of the absolute velocity signal input by the measured object and the current displacement sensor output signal acting on the shaft, a steady state is reached. The relative displacement signal after reaching the steady state is proportional to the absolute velocity of the measured object within the determined frequency band, and thus the absolute velocity of the measured object is obtained.

[0067] Preferably, the permanent magnet negative stiffness component 9 includes a first permanent magnet ring 12, a second permanent magnet ring 13, a third permanent magnet ring 14, and a fourth permanent magnet ring 15.

[0068] The axes of the first permanent magnet ring 12, the second permanent magnet ring 13, the third permanent magnet ring 14, and the fourth permanent magnet ring 15 are the same. The shaft 4 passes through the axes of the first permanent magnet ring 12, the second permanent magnet ring 13, the third permanent magnet ring 14, and the fourth permanent magnet ring 15.

[0069] The inner and outer diameters of the first permanent magnet ring 12 and the second permanent magnet ring 13 are equal, the inner and outer diameters of the third permanent magnet ring 14 and the fourth permanent magnet ring 15 are equal, and the inner diameter of the third permanent magnet ring 14 is greater than the outer diameter of the first permanent magnet ring 12.

[0070] The first permanent magnet ring 12 and the second permanent magnet ring 13 are fixed on the shaft 4, and the lower surface of the first permanent magnet ring 12 is fixedly connected to the upper surface of the second permanent magnet ring 13.

[0071] Both the third permanent magnet ring 14 and the fourth permanent magnet ring 15 are fixedly connected to the housing 11, and a set axial gap is provided between the third permanent magnet ring 14 and the fourth permanent magnet ring 15. Specifically, the axial gap between the third permanent magnet ring 14 and the fourth permanent magnet ring 15 depends on the magnetic field characteristics of the four permanent magnet rings and the coupling degree between the first permanent magnet ring 12 and the second permanent magnet ring 13 and the third permanent magnet ring 14 and the fourth permanent magnet ring 15. In this embodiment, the axial gap between the third permanent magnet ring 14 and the fourth permanent magnet ring 15 = the axial height of the first permanent magnet ring 12, the second permanent magnet ring 13, the third permanent magnet ring 14, and the fourth permanent magnet ring 15 = 10 mm.

[0072] The axial heights of the first permanent magnet ring 12, the second permanent magnet ring 13, the third permanent magnet ring 14, and the fourth permanent magnet ring 15 are equal. By adjusting the axial gap between the third permanent magnet ring 14 and the fourth permanent magnet ring 15, the negative stiffness range and the acting strength of the permanent magnet negative stiffness component 9 can be adjusted. The magnetization direction of the permanent magnet ring is as Figure 3 shown, and the direction of the solid arrow in the figure represents the magnetization direction.

[0073] The permanent magnet negative stiffness component 9 of the present invention uses 4 permanent magnet rings, which has the characteristics of small volume and compact structure compared with other negative stiffness structures. By adjusting the axial gap between the third permanent magnet ring 14 and the fourth permanent magnet ring 15, and the distance between the third permanent magnet ring 14 and the fourth permanent magnet ring 15 and the first permanent magnet ring 12 and the second permanent magnet ring 13, the magnetic force and the negative stiffness strength can be flexibly configured.

[0074] The present invention solves the problems of insufficient low-frequency measurement bandwidth of traditional mechanical spring sensors and strong nonlinearity of magnetic springs, and improves the stability and low-frequency performance of the sensors. Through the mutual cooperation and structural optimization of permanent magnet rings, the natural frequency of the sensor is reduced, and the problem of constant-current heating caused by electromagnetic negative stiffness is avoided.

[0075] To restrict the movement direction of the shaft 4, the permanent magnet negative stiffness active absolute velocity sensor of the present invention further includes an air-bearing guide rail. The air-bearing guide rail is fixed inside the housing 11. The shaft passes through the air-bearing guide rail. In this embodiment, the number of air-bearing guide rails is two: the first air-bearing guide rail 7 and the second air-bearing guide rail 8. The permanent magnet negative stiffness component 9 is arranged between the first air-bearing guide rail 7 and the second air-bearing guide rail 8. That is, the shaft 4 passes through the actuator, the second air-bearing guide rail 8, the permanent magnet negative stiffness component 9, the first air-bearing guide rail 7, the upper surface of the housing 11 and the elastic component from bottom to top.

[0076] Furthermore, the permanent magnet negative stiffness active absolute velocity sensor of the present invention further includes an axial adjusting nut 5. The axial adjusting nut 5 is arranged between the reference mass block 2 and the metal spring 6. The shaft 4 passes through the axial adjusting nut 5. The axial adjusting nut 5 is used to adjust the initial position of the shaft 4.

[0077] To ensure that the relative displacement sensor 1 is within a suitable measurement range, the permanent magnet negative stiffness active absolute velocity sensor of the present invention further includes a linear displacement guide rail 3. The relative displacement sensor 1 is fixed on the upper surface of the housing 11 through the linear displacement guide rail 3. The initial relative position between the relative displacement sensor 1 and the reference mass block 2 is adjusted through the linear displacement guide rail 3 to ensure that the relative displacement sensor 1 is within a suitable measurement range. In this embodiment, the relative displacement sensor 1 is located above the reference mass block 2, and the change value of the distance between the lower surface of the relative displacement sensor 1 and the upper surface of the reference mass block 2, that is, the relative displacement, is measured to determine the relative displacement between the reference mass block 2 and the upper surface of the housing 11. After feedback control, the absolute velocity of the measured object 18 is determined. The relative displacement sensor 1 actively controls to provide a control input.

[0078] In this embodiment, it is defined that Figure 2 the center dash line is the Z direction, which is also Figure 1 the axial direction of the central axis, and the direction indicated by the arrow is the positive direction of the Z direction.

[0079] The first permanent magnet ring 12 and the second permanent magnet ring 13 in the permanent magnet negative stiffness component 9, the magnet 16 of the voice coil motor 10, the reference mass 2 and the axial adjusting nut 5 are connected together by the shaft 4 to form an inertial reference point. The shaft 4 passes through the metal spring 6 and two air bearing guide rails and can only move along the Z direction under the constraint of the air bearing guide rails. The inertial reference point is supported by the metal spring 6 and has no contact with the outer shell 11, forming a spring-mass oscillator that can move along the Z-axis direction. The spring-mass oscillator is jointly composed of the reference mass 2, the shaft 4, the axial adjusting nut 5, the first permanent magnet ring 12, the second permanent magnet ring 13 and the magnet 16 of the voice coil motor 10. The axial motion states of any point on the spring-mass oscillator are exactly the same, that is, the displacements of any point in the axial direction are exactly the same. That is to say, the relative displacements of any point from the lower surface of the relative displacement sensor 1 are exactly the same. Therefore, any point on the entire spring-mass oscillator can be regarded as an inertial reference point. Connect the outer shell 11 to the object under test 18. By measuring the relative displacement between the spring-mass oscillator and the outer shell 11 and through feedback control, the absolute velocity information of the object under test 18 is finally obtained.

[0080] Furthermore, as Figure 4 shown, the control component includes a signal conditioning module, a feedback control module and a drive module.

[0081] The signal conditioning module is connected to the relative displacement sensor 1. The signal conditioning module is used to convert the relative displacement signal into a voltage signal according to the gain of the relative displacement sensor 1 and the corner frequency of the relative displacement sensor 1. Specifically, the conditioning module converts the charge signal output by the relative displacement sensor 1 into a voltage signal proportional to the relative displacement.

[0082] The feedback control module is connected to the signal conditioning module. The feedback control module is used to determine the control voltage signal by using a differential controller, a low-frequency stability filter, a differential intensity adjustment filter and a high-frequency dynamic suppression filter.

[0083] The drive module is connected to the feedback control module and the actuator. The drive module is used to determine the feedback control signal according to the thrust constant of the voice coil motor and the control voltage signal. The feedback control signal is used to control the magnitude of the current applied to the voice coil motor. The voice coil motor suppresses the relative movement between the reference mass and the outer shell under the action of the feedback control signal. That is, the drive module converts the control voltage signal output by the feedback control module into force to suppress the movement of the reference mass, and further converts the relative displacement signal into the absolute velocity signal of the object under test.

[0084] In this embodiment, the drive module is the drive circuit of the voice coil motor.

[0085] Through the configuration design and parameter configuration of the permanent magnet negative stiffness component (axial spacing between the third permanent magnet ring and the fourth permanent magnet ring, axial spacing between the first permanent magnet ring and the second permanent magnet ring, radial clearance between the first and second permanent magnet rings and the third and fourth permanent magnet rings, and the sizes of the first, second, third, and fourth permanent magnet rings), taking advantage of the compact structure characteristics of the permanent magnet negative stiffness component, the stiffness of the active absolute velocity sensor is reduced, the low-frequency measurement bandwidth of the sensor is expanded with a small volume, and combined with the corresponding active control strategy, the movement of the reference mass block is suppressed, the relative displacement between the permanent magnet rings in the permanent magnet negative stiffness component is reduced, thereby improving the nonlinear problem of the sensor and suppressing the further drift trend caused by the installation error, and improving the low-frequency performance of the sensor.

[0086] To better understand the solution of the present invention, the active control strategy of the sensor of the present invention will be specifically described below.

[0087] As Figure 5 shown, in the figure represents the input velocity of the housing (m / s), that is, the velocity of the object to be measured, x-w represents the relative displacement (m) between the reference mass block and the housing output, u i represents the voltage signal (V) output by the signal conditioning module, u a represents the control voltage signal (V) output by the feedback control module, f a represents the force (N) exerted by the drive module on the spring mass oscillator.

[0088] P·R represents the transfer function from the housing velocity to the relative displacement between the reference mass block and the housing without the feedback channel. Where P=-ms is the forward channel, representing the transfer function of the inertial force that the housing velocity is transmitted to the mass oscillator through passive elements such as springs and dampers. is the controlled object, representing the transfer function from the force exerted on the mass oscillator to the relative displacement between the reference mass block and the housing. m represents the total mass of the spring mass oscillator, c represents the equivalent damping of the overall mechanical system, k represents the equivalent stiffness of the overall mechanical system, and s represents the Laplace operator.

[0089] G rd represents the transfer function from the relative displacement between the reference mass block and the housing to the output voltage of the signal conditioning module. Among them, A rd represents the gain of the relative displacement sensor, ω rd represents the corner frequency of the relative displacement sensor.

[0090] G m represents the transfer function from the output voltage of the feedback control module to the force exerted by the voice coil motor on the mass oscillator, A vcDenote the thrust constant of the voice coil motor; A ac Denote the gain of the drive circuit, ω ac Denote the corner frequency of the drive circuit. H vc G(s) represents the voice coil motor part of the actuator, H ac D(s) represents the drive circuit part of the actuator.

[0091] W represents the transfer function from the output voltage of the signal conditioning module to the output voltage of the feedback control module. The control strategy in the feedback controller module is expressed in the frequency domain as:

[0092]

[0093] u a = u i *W(s).

[0094] Among them, W(s) represents the feedback control strategy, which includes four parts: a differential controller, a low-frequency stability filter, a differential intensity adjustment filter, and a high-frequency dynamic suppression filter. Among them, the differential controller is used to convert the relative displacement between the housing and the reference mass block into relative velocity, A p is the differential control gain, which adjusts the control intensity; the low-frequency stability filter has two functions. Within the frequency range from DC frequency to ω in , combined with the differential controller, it attenuates the control input in this frequency band to avoid integral saturation; within the frequency range from ω in to ω c1 , it generates an integral effect to suppress the drift of the reference mass block. ω c1 is a key frequency point, which needs to balance the low-frequency bandwidth of the active absolute velocity sensor and the control intensity of drift suppression. The differential intensity adjustment filter is used to adjust the differential intensity corresponding to different frequency bands, so as to cancel the influence of the low-frequency stability filter between ω c1 and ω c2 , generate a stable differential effect, enhance the differential effect between ω c2 and ω bh , improve the tracking and response of the voice coil motor to high-frequency control signals, and enhance the ability to suppress the movement of the reference mass block; the high-frequency dynamic suppression filter attenuates the control input in the frequency range higher than ω bh , and suppresses the response of the feedback control module to high-frequency dynamics. The frequency response schematic diagram of W(s) is as Figure 6 shown.

[0095] Therefore, the overall working transfer function of the active absolute velocity sensor is:

[0096]

[0097] As Figure 7As shown in the figure, the control method of the permanent magnet negative stiffness active absolute velocity sensor of the present invention includes:

[0098] S1: Fix the lower surface of the housing on the object to be measured.

[0099] S2: When the object to be measured moves, under the action of the shaft, displace the reference mass block, and collect the relative displacement between the reference mass block and the upper surface of the housing through the relative displacement sensor to obtain a relative displacement signal.

[0100] S3: Generate a feedback control signal according to the relative displacement signal, and control the actuator to suppress the relative movement between the reference mass block and the housing, thereby converting the relative displacement signal into the absolute velocity signal of the object to be measured. That is, the absolute velocity of the object to be measured is obtained after the relative displacement signal is feedback-controlled.

[0101] Specifically, first convert the relative displacement signal into a voltage signal according to the gain of the relative displacement sensor and the corner frequency of the relative displacement sensor. In this embodiment, the following formula is used to convert the relative displacement signal into a voltage signal:

[0102]

[0103] where, u i is the voltage signal, A rd is the gain of the relative displacement sensor, ω rd is the corner frequency of the relative displacement sensor, s is the Laplace operator, and x - w is the relative displacement between the reference mass block and the housing.

[0104] Then, according to the voltage signal, use a differential controller, a low-frequency stability filter, a differential intensity adjustment filter, and a high-frequency dynamic suppression filter to determine the control voltage signal. The following formula is used to determine the control voltage signal:

[0105]

[0106] where, u a is the control voltage signal, u i is the voltage signal, A p is the differential control gain, s is the Laplace operator, ω in , ω c1 , ω c2 , ω bh are all frequency points.

[0107] Finally, determine the feedback control signal according to the thrust constant of the voice coil motor, the gain of the drive circuit, the corner frequency of the drive circuit, and the control voltage signal. The feedback control signal is used to control the magnitude of the current applied to the voice coil motor.

[0108] The voice coil motor suppresses the movement of the reference mass under the action of the feedback control signal. Since a force is generated when the coil of the voice coil motor is placed in a magnetic field, and the magnitude of the force is proportional to the current applied to the coil. Therefore, the force exerted by the voice coil motor on the spring mass oscillator can be determined according to the magnitude of the current applied to the coil. Specifically, the following formula is used to determine the force exerted by the voice coil motor on the spring mass oscillator:

[0109]

[0110] where f a is the force exerted by the voice coil motor on the spring mass oscillator, A vc is the thrust constant of the voice coil motor, A ac is the gain of the drive circuit, ω ac represents the corner frequency of the drive circuit.

[0111] The active control strategy implemented in the feedback control module of the present invention utilizes the measurement results of the relative displacement sensor, processes them through a control algorithm, and drives the voice coil motor to compensate for the control of the reference mass. A frequency band division design is adopted. When the frequency is higher than ω in , the algorithm exhibits an integral action to suppress the drift of the reference mass. At the same time, comprehensively considering the problem of integral saturation instability caused by the DC component of the relative displacement sensor in this frequency band, a low-frequency stability filter in the feedback control module is designed. Between ω c1 and ω bh frequency range, it shows differential control using relative displacement information, applying relative damping to the reference mass, effectively suppressing the relative movement between the reference mass and the housing, and expanding the low-frequency measurement bandwidth. At the same time, the cancellation problem of the integral control action on the differential control in this frequency band is comprehensively considered, and the high-frequency cut-off frequency of the differential action is determined according to the high-frequency dynamic characteristics and the effective dynamic range of the control system signal to suppress the high-frequency noise of the control system and improve stability. Specifically, it is manifested as the differential controller in the feedback control module, its differential intensity adjustment filter, and the high-frequency dynamic suppression filter.

[0112] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts between the various embodiments, reference can be made to each other.

[0113] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A permanent magnet negative stiffness active absolute velocity sensor for measuring the absolute velocity of a measured object, characterized in that, The permanent magnet negative stiffness active absolute velocity sensor includes: A housing, the lower surface of which is fixedly arranged on the object to be measured; An actuator, arranged inside the housing; A permanent magnet negative stiffness component, arranged inside the housing; An elastic component, fixedly arranged on the upper surface of the housing; A shaft, successively passing through the actuator, the permanent magnet negative stiffness component, the upper surface of the housing and the elastic component from bottom to top, and the bottom of the shaft is suspended inside the housing; A reference mass, fixedly arranged on the top of the shaft; A relative displacement sensor, fixedly arranged on the upper surface of the housing, used to measure the relative displacement between the reference mass and the upper surface of the housing to obtain a relative displacement signal; A control component, connected to the relative displacement sensor and the actuator, used to generate a feedback control signal according to the relative displacement signal; The actuator is used to suppress the relative movement between the reference mass and the housing under the action of the feedback control signal; the absolute velocity of the object to be measured is determined after the relative displacement signal is feedback-controlled; The actuator includes: a magnet and a coil; The magnet is suspended inside the housing, fixed to the shaft, and has a groove opened at the lower part; The coil is arranged in the groove of the magnet, fixedly connected to the bottom of the housing, and connected to the control component; The feedback control signal is used to control the magnitude of the current applied to the coil; The permanent magnet negative stiffness component includes a first permanent magnet ring, a second permanent magnet ring, a third permanent magnet ring and a fourth permanent magnet ring; The axes of the first permanent magnet ring, the second permanent magnet ring, the third permanent magnet ring and the fourth permanent magnet ring are the same; the shaft passes through the axes of the first permanent magnet ring, the second permanent magnet ring, the third permanent magnet ring and the fourth permanent magnet ring; The inner and outer diameters of the first permanent magnet ring and the second permanent magnet ring are equal, the inner and outer diameters of the third permanent magnet ring and the fourth permanent magnet ring are equal, and the inner diameter of the third permanent magnet ring is greater than the outer diameter of the first permanent magnet ring; The first permanent magnet ring and the second permanent magnet ring are fixed on the shaft, and the lower surface of the first permanent magnet ring is fixedly connected to the upper surface of the second permanent magnet ring; The third permanent magnet ring and the fourth permanent magnet ring are both fixedly connected to the housing, and the third permanent magnet ring and the fourth permanent magnet ring are separated by a set axial gap; 2. The permanent magnet negative stiffness active absolute velocity sensor according to claim 1, wherein The actuator is a voice coil motor; 3. The permanent magnet negative stiffness active absolute velocity sensor according to claim 1, characterized in that, The axial heights of the first permanent magnet ring, the second permanent magnet ring, the third permanent magnet ring and the fourth permanent magnet ring are equal; 4. The permanent magnet negative stiffness active absolute velocity sensor according to claim 1, characterized in that, The elastic component is a metal spring; 5. The permanent magnet negative stiffness active absolute velocity sensor according to claim 1, wherein The permanent magnet negative stiffness active absolute velocity sensor further includes an air bearing guide rail; The air bearing guide rail is fixed inside the housing; the shaft passes through the air bearing guide rail; the air bearing guide rail is used to constrain the movement direction of the shaft; 6. The permanent magnet negative stiffness active absolute velocity sensor according to claim 1, wherein The permanent magnet negative stiffness active absolute velocity sensor further includes an axial adjustment nut; The axial adjustment nut is arranged between the reference mass and the elastic component; the shaft passes through the axial adjustment nut; The axial adjustment nut is used to adjust the initial position of the shaft; 7. A control method for a permanent magnet negative stiffness active absolute velocity sensor, which is used to control the permanent magnet negative stiffness active absolute velocity sensor according to any one of claims 1-6, characterized in that, The control method of the permanent magnet negative stiffness active absolute velocity sensor includes: Fix the lower surface of the housing on the object to be measured; When the object to be measured moves, under the action of the shaft, displace the reference mass block, and collect the relative displacement between the reference mass block and the upper surface of the housing through the relative displacement sensor to obtain a relative displacement signal; Generate a feedback control signal according to the relative displacement signal, and control the actuator to suppress the relative movement between the reference mass block and the housing; the absolute velocity signal of the object to be measured is determined after the relative displacement signal is feedback-controlled.

8. The control method of the permanent magnet negative stiffness active absolute velocity sensor according to claim 7, characterized in that, The actuator is a voice coil motor; The generating a feedback control signal according to the relative displacement signal to control the actuator to suppress the relative movement between the reference mass block and the housing specifically includes: Convert the relative displacement signal into a voltage signal according to the gain of the relative displacement sensor and the corner frequency of the relative displacement sensor; Determine the control voltage signal according to the voltage signal by using a differential controller, a low-frequency stability filter, a differential intensity adjustment filter and a high-frequency dynamic suppression filter; Determine the feedback control signal according to the thrust constant of the voice coil motor, the gain of the drive circuit, the corner frequency of the drive circuit and the control voltage signal; the feedback control signal is used to control the magnitude of the current applied to the voice coil motor; the voice coil motor suppresses the movement of the reference mass block under the action of the feedback control signal.

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