A vibration frequency-based building safety detection device and method thereof

Abstract

The application relates to the technical field of building safety detection, in particular to a building safety detection device and method based on vibration frequency; the device comprises a propulsion module, a balance shell, a sensing coupling module containing a piezoelectric vibrator and a flexible film filled with silica particles, a negative pressure adjusting module and a control module; the device extracts the piezoelectric vibrator resonance drift amount to calculate the vibration coupling efficiency, and dispatches a miniature vacuum pump to control the negative pressure; the core is to offset the parasitic tensile stress of the piezoelectric vibrator through the shared negative pressure of two cavities, and to promote the blocking phase change of the silica particles to realize the variable stiffness adjustment; the application solves the problem that the rough surface contact compliance and the conduction efficiency are difficult to be considered, effectively reduces the high-frequency reflection loss and the flexible dissipation, and improves the collection quality of the micro-vibration signal.

Description

Technical Field

[0001] This invention relates to the field of building safety testing technology, specifically to a building safety testing device and method based on vibration frequency. Background Technology

[0002] In the current environment of building structural safety inspection, vibration frequency measurement is an important means of assessing the building condition. It requires the accurate acquisition of high-frequency micro-vibration signals from the building surface by piezoelectric sensitive elements. To obtain these vibration signals, existing testing equipment generally uses rigid probes or purely flexible pads as contact interfaces. Due to the roughness and slight undulations of building surfaces, rigid probes form local point contacts when in contact, resulting in air gap reflection loss of high-frequency vibration waves at the interface. Although purely flexible pads can conform to the surface morphology, the flexible material itself has a dissipative effect on high-frequency vibration components. In addition, to improve the fit of the interface, existing solutions often use mechanical pre-tightening or negative pressure adsorption. This process will transmit additional parasitic tensile stress to the piezoelectric sensitive elements, change the mechanical boundary conditions of the elements, and interfere with the high-frequency resonance characteristics and signal recognition accuracy of the sensor when passively receiving signals.

[0003] Therefore, how to balance the surface compliance of the detection interface with the high-frequency vibration transmission efficiency on rough building surfaces, while effectively counteracting the interference of prestress on the sensor's measurement characteristics, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a building safety detection device and method based on vibration frequency. Specifically, the technical solution of this invention is as follows:

[0005] A building safety detection device based on vibration frequency, comprising: A propulsion module mounted on a base and used to drive the linear movement of the balance housing; Installed at the propulsion end of the propulsion module, the internal structure is a balanced shell divided into a flattening rear cavity and a coupling front cavity via a middle partition. The sensing coupling module includes a piezoelectric vibrator suspended in the coupling front cavity, a conduction shaft coaxially connected to its front end, a reverse pull rod connected to its tail end through a middle partition to flatten the annular reverse piston in the rear cavity, and a flexible polymer elastic membrane filled with silica particles fixed in the opening of the coupling front cavity. The system includes a connecting air passage that opens into the balance shell to connect the two chambers and a negative pressure regulating module that connects the balance shell to provide synchronous negative pressure to the two chambers; a control module that is electrically connected to the piezoelectric vibrator and the micro vacuum pump and is configured to: extract the impedance resonant frequency drift of the piezoelectric vibrator and adjust the pulse width modulation duty cycle of the micro vacuum pump to regulate the negative pressure. The annular reverse piston is connected to the piezoelectric vibrator via the reverse pull rod; the piezoelectric vibrator is configured to switch to passive receiving mode after the vibration coupling efficiency reaches a preset range.

[0006] In some embodiments, the propulsion module includes: A linear stepper motor, a ball screw, a guide nut, and a hollow push rod; wherein the linear stepper motor is fixedly connected to the tail of the base; The ball screw is connected to the output spindle of the linear stepper motor; The guide nut is fitted onto the ball screw; The tail end of the hollow push rod is fixedly connected to the guide nut, the hollow push rod passes through the base, and the front end of the hollow push rod is connected to the balance shell.

[0007] In some embodiments, the base is a cylindrical aluminum alloy base, and the linear stepper motor is fixedly connected to the tail flange surface of the base by bolts; wherein, the output spindle of the linear stepper motor is connected to the ball screw through a plum blossom-shaped flexible coupling, and the hollow push rod is supported in the inner hole of the base by a linear sliding bearing.

[0008] In some embodiments, the outer circle of the annular reverse piston and the inner wall of the flattened cavity are fitted with a clearance; wherein, a polyurethane sealing ring is provided between the outer circle of the annular reverse piston and the inner wall of the flattened cavity to achieve a sliding seal.

[0009] In some embodiments, there are three reverse tie rods, which are made of carbon fiber and are evenly distributed; wherein, the middle partition plate has a guide hole for the reverse tie rods to pass through, and a dynamic sealing ring is provided at the guide hole.

[0010] In some embodiments, the conductive shaft is made of titanium alloy and extends forward to the opening end of the coupling front cavity; wherein, a closed space is formed between the flexible polymer elastic membrane and the front end face of the conductive shaft, and the silica particles are micron-sized high-hardness particles and fill the closed space.

[0011] In some embodiments, the side wall of the balancing housing is provided with a negative pressure air inlet; wherein the negative pressure air inlet is connected to a miniature vacuum pump via a pneumatic hose.

[0012] In some implementations, the control module has a preset nonlinear mapping relationship, which is characterized as a mapping relationship between the electrical impedance resonant frequency drift and the vibration coupling efficiency between silica particles and the building surface.

[0013] A control method for a building safety detection device based on vibration frequency includes the following steps: S1: Initialize the equipment and control the propulsion module to drive the balance shell to move towards the building surface, so that the flexible polymer elastic membrane and the internal silica particles come into contact with the building surface. S2: Input a wideband self-test excitation signal to the piezoelectric vibrator and extract the amount of impedance resonant frequency drift of the piezoelectric vibrator in the current state; S3: Based on the extracted impedance resonant frequency drift, the vibration coupling efficiency between the current silica particles and the building surface is calculated using a preset nonlinear mapping relationship. S4: Dynamically schedule the pulse width modulation duty cycle of the micro vacuum pump according to the vibration coupling efficiency, and control the negative pressure intensity in the coupling cavity to adjust the stiffness of the silica particles. S5: During the negative pressure regulation process, the negative pressure in the back cavity increases synchronously, driving the annular reverse piston to move backward. Through the reverse pull rod, a backward mechanical compensation pull force is applied to the piezoelectric vibrator to offset the parasitic tensile stress generated by the contraction of the flexible polymer elastic membrane. S6: After the negative pressure intensity stabilizes and a preset stabilization time has elapsed, the piezoelectric vibrator is controlled to stop sending self-test signals and switch to passive receiving mode. High-frequency micro-vibration signals inside the building are collected through silica particle media, and the building vibration frequency is obtained accordingly.

[0014] In some embodiments, step S4, the process of adjusting the stiffness of the silica particles by controlling the negative pressure intensity in the pre-coupling cavity, includes: adjusting or maintaining the pulse width modulation duty cycle of the micro vacuum pump control signal based on the deviation between the calculated vibration coupling efficiency and the preset range.

[0015] The present invention has the following beneficial effects: 1. This invention solves the problem of balancing contact compliance and conduction efficiency on rough surfaces by setting up a flexible polymer elastic membrane filled with silica particles and a negative pressure adjustment module. During detection, the flexible membrane first conforms to and fills the tiny unevenness of the building surface, and then a micro vacuum pump adjusts the negative pressure intensity of the coupling cavity, causing the particles to undergo a blocking phase transition and become a solid-like state. This variable stiffness adjustment effectively reduces the high-frequency reflection loss caused by the point contact of the rigid probe and the dissipation of vibration by the purely flexible material, dynamically adjusting the vibration coupling efficiency to a preset range and improving the acquisition quality of micro-vibration signals. 2. This invention employs a design that balances the shared synchronous negative pressure between the rear chamber and the front chamber of the coupling shell. Combined with an annular reverse piston and a reverse pull rod, it solves the problem of parasitic tensile stress being transmitted to the sensitive element during the process of negative pressure stiffness variation. During negative pressure adjustment, the negative pressure in the rear chamber increases synchronously, driving the piston to move backward. The pull rod applies a mechanical pulling force to the piezoelectric vibrator that is equal to and opposite to the parasitic tensile stress. This mechanism achieves dynamic adaptive cancellation of the force, enabling the piezoelectric vibrator to reach a steady state with zero prestress interference. This avoids pre-tightening force interfering with the high-frequency resonance characteristics and improves the frequency measurement accuracy during passive reception. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the device; Figure 2 This is a schematic diagram of the cross-sectional structure of the device's base; Figure 3 This is a schematic diagram of the device's sensing coupling module structure; Figure 4 This is a flowchart of the method of the present invention.

[0017] In the diagram: 1. Base; 2. Propulsion module; 3. Balancing shell; 4. Sensing coupling module; 5. Negative pressure regulation module; 6. Control module; 7. Intermediate partition; 8. Flattening rear cavity; 9. Coupling front cavity; 10. Piezoelectric vibrator; 11. Conducting shaft; 12. Reverse pull rod; 13. Annular reverse piston; 14. Flexible polymer elastic membrane; 15. Silica particles; 16. Miniature vacuum pump; 17. Connecting air passage; 18. Linear stepper motor; 19. Ball screw; 20. Guide nut; 21. Hollow push rod; 22. Output spindle; 23. Plum blossom-shaped flexible coupling; 24. Linear sliding bearing; 25. Polyurethane sealing ring; 26. Guide hole; 27. Dynamic sealing ring; 28. Enclosed space; 29. ​​Negative pressure air inlet; 30. Pneumatic hose. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Example 1: A building safety detection device based on vibration frequency, such as Figure 1 As shown, it includes: A propulsion module 2 mounted on a base 1 and used to drive the linear movement of the balance housing 3; Installed at the propulsion end of propulsion module 2, the internal structure of the balance shell 3 is divided into a smoothing rear cavity 8 and a coupling front cavity 9 via a middle partition 7; Sensing coupling module 4, such as Figure 3 As shown, it includes a piezoelectric vibrator 10 suspended in the coupling front cavity 9, a conduction shaft 11 coaxially connected to its front end, a reverse pull rod 12 connected to its tail end through the middle partition 7 and connected to the annular reverse piston 13 in the rear cavity 8, and a flexible polymer elastic membrane 14 fixed in the opening of the coupling front cavity 9 and filled with silica particles 15. The system includes a connecting air passage 17 that opens into the balance housing 3 to connect the two chambers and a negative pressure regulating module 5 that connects the balance housing 3 to provide synchronous negative pressure to the two chambers; and a control module 6 that is electrically connected to the piezoelectric vibrator 10 and the micro vacuum pump 16 and configured to: extract the impedance resonant frequency drift of the piezoelectric vibrator 10 and adjust the pulse width modulation duty cycle of the micro vacuum pump 16 to regulate the negative pressure. The annular reverse piston 13 is connected to the piezoelectric vibrator 10 via the reverse pull rod 12; the piezoelectric vibrator 10 is configured to switch to passive receiving mode after the vibration coupling efficiency reaches a preset range; In this embodiment, the base 1 serves as the installation and load-bearing component of the whole machine, and is used to provide axial support for the propulsion module 2, the balance shell 3 and related transmission components; the propulsion module 2 is used to drive the balance shell 3 to make linear displacement relative to the building surface in the approach or departure direction, so that the flexible polymer elastic membrane 14 establishes controlled contact with the building surface; The balance shell 3 is provided with a middle partition plate 7 to form a mutually separated flattening rear cavity 8 and coupling front cavity 9. The coupling front cavity 9 is used to accommodate the piezoelectric vibrator 10, the conduction shaft 11 and the particle coupling medium. The flattening rear cavity 8 is used to arrange the annular reverse piston 13 and establish a negative pressure compensation force space that changes synchronously with the coupling front cavity 9. The piezoelectric vibrator 10 is a sensitive element that converts mechanical vibration into electrical signals. Its front end is connected to the transmission shaft 11, and its rear end is connected to the annular reverse piston 13 via the reverse pull rod 12, so that the change in the coupling state of the front end and the change in the compensating force of the rear end form a mechanical correspondence. The flexible polymer elastic membrane 14 and the silica particles 15 together constitute a variable stiffness contact interface, wherein the flexible polymer elastic membrane 14 provides surface compliance, and the silica particles 15 provide adjustable transmission stiffness under negative pressure. The micro vacuum pump 16 in the negative pressure regulating module 5 acts simultaneously on the smoothing rear chamber 8 and the coupling front chamber 9 through the connecting air passage 17, so that the pressure changes in the two chambers are consistent. Thus, the particulate medium is transformed from a loose state to a dense blockage state in the coupling front chamber 9. In the smoothing rear chamber 8, the annular reverse piston 13 is driven to move and a reverse mechanical force is applied to the piezoelectric vibrator 10 through the reverse pull rod 12. The control module 6 applies a broadband self-test excitation signal to the piezoelectric vibrator 10 to obtain the impedance resonant frequency drift. The impedance resonant frequency drift refers to the change in the characteristic frequency of the impedance spectrum of the piezoelectric vibrator 10 relative to the reference state under different front-end contact stiffness conditions. This change reflects the actual vibration transmission state between the silica particles 15 and the building surface. The control module 6 substitutes this change into a preset nonlinear mapping relationship to obtain the vibration coupling efficiency. The vibration coupling efficiency is used to characterize the degree of energy transmission from the building surface vibration to the piezoelectric vibrator 10 via the flexible polymer elastic membrane 14, silica particles 15, and transmission shaft 11. The control module 6 adjusts the pulse width modulation duty cycle of the micro vacuum pump 16 according to the vibration coupling efficiency. When the vibration coupling efficiency is lower than the preset range, the negative pressure intensity is increased to improve the stiffness of the particle layer. When the vibration coupling efficiency is higher than the upper limit of the preset range, the negative pressure intensity is reduced to reduce the impedance mismatch caused by over-hardening. Since the flattening cavity 8 and the coupling cavity 9 share the negative pressure state, the parasitic tensile stress generated by the contraction of the flexible polymer elastic membrane 14 on the piezoelectric vibrator 10 can be offset by the corresponding reverse mechanical tension provided by the annular reverse piston 13 through the reverse tie rod 12, thereby reducing the additional structural noise introduced by the variable stiffness action. The technical principle is as follows: the effective aerodynamic force-bearing area of ​​the annular reverse piston 13 in the rear cavity 8 is configured to match the equivalent axial projection area of ​​the flexible polymer elastic membrane 14 when it contracts under negative pressure; because the two cavities share the same dynamic negative pressure source, under any negative pressure level, the axial mechanical pulling force generated by the rearward movement of the annular reverse piston 13 can dynamically and adaptively cancel out the parasitic tensile stress generated by the rearward contraction of the flexible polymer elastic membrane 14 pulling the transmission shaft 11 in numerical value and opposite direction, thereby achieving force balance on the installation boundary of the piezoelectric vibrator 10 and avoiding the interference of prestress on the high-frequency resonance characteristics; After the vibration coupling efficiency reaches the preset range, the control module 6 stops the self-test excitation of the piezoelectric vibrator 10, so that the piezoelectric vibrator 10 enters the passive receiving mode. The vibration signal of the building surface is transmitted to the piezoelectric vibrator 10 through the medium of the solidified silica particles 15 and outputs an electrical signal. Through the above structure and control relationship, the contact adhesion capability and high-frequency vibration transmission capability can be taken into account on the rough building surface, reducing the high-frequency reflection loss caused by the local point contact of the traditional rigid probe, as well as the dissipation effect of the simple flexible pad on the high-frequency components. The reference state is preferably defined as the calibration state in which the piezoelectric vibrator 10 is in a free boundary or in light contact with a standard flat reference surface, and the coupling front cavity 9 and the flattening rear cavity 8 are in a preset initial negative pressure or normal pressure condition. The control module 6 stores the characteristic frequency of the impedance spectrum in this state as a comparison reference during the device startup phase. The extraction process of the impedance resonant frequency drift can be executed according to the following logic: First, control the piezoelectric vibrator 10 to perform frequency sweep excitation in a preset frequency band and simultaneously collect voltage, current or equivalent impedance response; then identify the characteristic frequency corresponding to the impedance amplitude peak, phase change point or electromechanical coupling characteristic inflection point from the collection results; compare the current characteristic frequency with the corresponding characteristic frequency in the reference state to obtain the frequency difference, and use the frequency difference as the impedance resonant frequency drift input for subsequent mapping calculation. Vibration coupling efficiency is used as a control criterion in this embodiment. Its physical meaning is a quantitative characterization of the ability of the current contact interface to transmit vibration to the building surface. The higher the value, the higher the proportion of effective vibration components transmitted from the building surface to the piezoelectric vibrator 10. It can be represented by a normalized dimensionless index and converted from the nonlinear mapping relationship obtained by calibration. The preset range is the working range of coupling efficiency applicable to the surface roughness, material impedance and detection frequency band of the target building. For example, in this embodiment, the preset range can be set to between 0.75 and 0.85. The working range can be predetermined by prototype calibration, comparison with standard sensor results or repeatability test results. Its role in the control logic is to serve as the decision boundary for the micro vacuum pump 16 to pressurize, depressurize or maintain the current duty cycle. Parasitic tensile stress refers to the non-target pre-tightening stress added to the axial direction of the piezoelectric vibrator 10 through the particle layer, the conduction shaft 11, or the structural connection path during the negative pressure contraction and particle compaction process of the flexible polymer elastic membrane 14. This stress will change the boundary conditions of the piezoelectric vibrator 10 and interfere with the frequency response during passive reception. The control module 6 does not directly measure the stress value to compensate for the parasitic tensile stress, but uses the structural relationship of the rear cavity 8 and the coupling front cavity 9 being simultaneously subjected to negative pressure to make the annular reverse piston 13 output a reverse mechanical tensile force corresponding to the contraction trend of the front cavity, thereby reducing the pre-stress bias at the system level. The dynamic scheduling of the 16-pulse-width modulation duty cycle of the miniature vacuum pump can be performed in a step-by-step approximation manner: when the calculated vibration coupling efficiency is lower than the lower limit of the preset range, the duty cycle is increased by a preset increment, and the drift extraction and coupling efficiency calculation are re-executed after each adjustment; when the vibration coupling efficiency is within the preset range, the current duty cycle is maintained and short-term stability is confirmed; when the vibration coupling efficiency is higher than the upper limit of the preset range, the duty cycle is decreased by a preset reduction, and the above detection closed loop is repeated. Thus, a clear correspondence is formed between the input source, calculation process, criterion source, and action output in the control flow, making the vibration coupling efficiency, preset range, electrical impedance resonant frequency drift, and parasitic tensile stress compensation logic all have executable engineering meaning; to ensure the programmable implementation of the algorithm and software module and the clarity of data flow interaction, the control module 6 includes an analog-to-digital conversion unit and a microprocessor. In terms of data flow: the analog voltage and current response signals generated by the piezoelectric oscillator 10 under frequency sweep excitation are converted into discrete digital impedance signal sequences by the analog-to-digital conversion unit at a preset sampling rate and input to the microprocessor; the microprocessor performs extreme value search on the digital impedance signal sequence and extracts the digital characteristic frequency corresponding to the current impedance amplitude peak. The microprocessor calculates the difference between the characteristic frequency and the reference state frequency and stores it as a floating-point impedance resonant frequency drift. After calculating the vibration coupling efficiency based on the drift, the microprocessor outputs a square wave control signal with a corresponding pulse width modulation duty cycle to the drive circuit of the micro vacuum pump 16 through its timer peripheral, thereby completing the closed-loop data flow from front-end analog signal acquisition, mid-end digital feature extraction to back-end actuator control.

[0020] like Figure 2 As shown, the propulsion module 2 includes a linear stepper motor 18, a ball screw 19, a guide nut 20, and a hollow push rod 21; wherein, the linear stepper motor 18 is fixedly connected to the tail of the base 1; the ball screw 19 is connected to the output spindle 22 of the linear stepper motor 18; the guide nut 20 is fitted onto the ball screw 19; the tail end of the hollow push rod 21 is fixedly connected to the guide nut 20, the hollow push rod 21 passes through the base 1, and the front end of the hollow push rod 21 is connected to the balance housing 3; In this embodiment, the propulsion module 2 adopts a combination of a linear stepper motor 18, a ball screw 19, a guide nut 20, and a hollow push rod 21 to achieve controllable propulsion of the balance housing 3 along the detection direction. The linear stepper motor 18 is used to provide distinguishable angular displacement input, the ball screw 19 is used to convert angular displacement into axial linear displacement, the guide nut 20 is used to cooperate with the ball screw 19 and transmit the displacement to the hollow push rod 21, and the hollow push rod 21 is used to transmit propulsion force to the balance housing 3. The technical considerations for adopting this structure are that the roughness and local undulations of the building surface will change the contact compression of the flexible polymer elastic membrane 14. If the control precision of the advancing displacement is insufficient, insufficient contact or excessive compression may easily occur, affecting the morphology replication effect of the silica particles 15 filling interface and the sensitivity of subsequent variable stiffness adjustment. After the output spindle 22 of the linear stepper motor 18 drives the ball screw 19 to rotate, the guide nut 20 moves along the screw axis, driving the hollow push rod 21 fixedly connected to it to move synchronously. The hollow push rod 21 then pushes the balance shell 3 closer to the building surface, so that the flexible polymer elastic membrane 14 gradually adheres to the surface under the set contact conditions. The hollow push rod 21 adopts a hollow structure, which can reserve space for the piezoelectric vibrator 10 signal line, the micro vacuum pump 16 connecting pipe or auxiliary detection wire, thereby reducing the interference of external wires on the straightness of propulsion and load distribution; the displacement control of the propulsion module 2 can be executed according to the set step distance, and the change of contact pressure, displacement increment or vibration coupling efficiency change trend is used as the logical judgment condition for stopping propulsion, so that the flexible polymer elastic membrane 14 and the internal silica particles 15 are in a working state that can fully adhere to the surface without being over-compacted; Through the propulsion module 2, the sensing coupling module 4 can repeatedly establish initial contact boundaries that meet the preset contact area threshold at different building surface positions, providing a stable mechanical prerequisite for the control module 6 to subsequently adjust the negative pressure based on the amount of electrical impedance resonant frequency drift.

[0021] The base 1 is a cylindrical aluminum alloy base 1, and the linear stepper motor 18 is fixedly connected to the tail flange surface of the base 1 by bolts; wherein, the output spindle 22 of the linear stepper motor 18 is connected to the ball screw 19 through the plum blossom-shaped elastic coupling 23, and the hollow push rod 21 is supported in the inner hole of the base 1 through the linear sliding bearing 24. In this embodiment, the base 1 is set as a cylindrical aluminum alloy base 1; the aluminum alloy base 1 is used to reduce the overall weight of the machine while meeting the overall rigidity requirements, and to reduce the additional load when handheld or moving for detection; the cylindrical structure is conducive to forming a continuous axial mounting reference, so that the linear stepper motor 18, ball screw 19, hollow push rod 21 and balance housing 3 are kept coaxially arranged. The linear stepper motor 18 is fixedly connected to the tail flange of the base 1 by bolts. The bolt connection provides a detachable assembly relationship, which is convenient for maintenance and replacement of drive components, and the flange surface ensures the flatness and perpendicularity of the mounting end face. A plum blossom-shaped flexible coupling 23 is provided between the output spindle 22 of the linear stepper motor 18 and the ball screw 19. This coupling is used to compensate for the radial and angular deviations within the allowable range of form and position tolerances caused by machining errors or assembly errors between the motor output shaft and the axis of the ball screw 19. It reduces the radial additional load caused by rigid direct connection to be transmitted to the ball screw 19 and the hollow push rod 21, thereby reducing the vibration source input of the propulsion module 2. The hollow push rod 21 is supported in the inner hole of the base 1 by a linear sliding bearing 24. The linear sliding bearing 24 is used to limit the degree of freedom of the hollow push rod 21, so that it mainly performs axial linear motion and suppresses lateral sway. This structure can reduce the deflection of the balance shell 3 during the advancement process, so that when the flexible polymer elastic membrane 14 comes into contact with the building surface, a force distribution with a contact pressure variance less than a preset threshold is formed, avoiding local overpressure that causes strain concentration in the membrane or non-uniform pre-curing of the particulate medium. By combining a cylindrical aluminum alloy base 1, a tail flange installation, elastic coupling compensation, and a linear sliding bearing 24 for guidance, stable coaxial propulsion conditions can be provided for the variable stiffness coupling interface, reducing the influence of mechanical transmission errors on the resonance characteristic identification of the piezoelectric vibrator 10 and improving the corresponding stability between the impedance resonant frequency drift and the actual coupling state.

[0022] The outer circle of the annular reverse piston 13 and the inner wall of the flattened cavity 8 are fitted with a clearance; a polyurethane sealing ring 25 is provided between the outer circle of the annular reverse piston 13 and the inner wall of the flattened cavity 8 to achieve sliding sealing. In this embodiment, the annular reverse piston 13 is disposed in the flattening rear cavity 8, and its outer circle and the inner wall of the flattening rear cavity 8 are fitted with a clearance to ensure that the annular reverse piston 13 can generate a stable linear displacement under axial negative pressure drive. The clearance means that there is a clearance between the outer circle of the annular reverse piston 13 and the inner wall of the flattening rear cavity 8 for relative sliding. This fit relationship is used to balance the flexibility of movement and the feasibility of assembly. If the fit clearance is less than the preset lower limit, the piston movement resistance will increase, making it difficult to respond synchronously with the negative pressure change of the coupling front cavity 9. If the fit clearance is greater than the preset upper limit, the airtightness will be insufficient, affecting the synchronous negative pressure transmission effect. To maintain the airtightness of the rear chamber 8, a polyurethane sealing ring 25 is provided between the outer circle of the annular reverse piston 13 and the inner wall of the rear chamber 8. The polyurethane sealing ring 25 is used to provide an elastic fit seal during piston movement and allows the piston to maintain a sliding motion with a leakage rate lower than the preset standard value under axial negative pressure. The technical consideration for choosing polyurethane material is that it has the wear resistance, resilience and sealing stability required for the corresponding working environment, and can maintain a contact seal state with pressure fluctuation less than the preset allowable value during repeated negative pressure adjustment cycles. When the pressure in the rear chamber 8 decreases, the annular reverse piston 13 moves axially under the combined action of the pressure difference in the chamber and the tension of the structural connection, and applies a compensating mechanical tension to the piezoelectric vibrator 10 through the reverse tie rod 12; when the pressure in the rear chamber 8 rises again, the annular reverse piston 13 returns to its original position under the combined action of the decrease in pressure difference and the elastic recovery of the structure. The annular reverse piston 13 and its sliding sealing structure enable the negative pressure change in the rear cavity 8 to be converted into a stable and repeatable mechanical compensation output, reducing the superimposed effect of the parasitic tensile stress generated during the contraction of the flexible polymer elastic membrane 14 on the low-frequency response of the piezoelectric vibrator 10, and improving the recognizability of building vibration signals under passive reception.

[0023] There are three reverse tie rods 12. The three reverse tie rods 12 are made of carbon fiber and are evenly distributed. The middle partition plate 7 has a guide hole 26 for the reverse tie rods 12 to pass through, and a dynamic sealing ring 27 is provided at the guide hole 26. In this embodiment, there are three reverse pull rods 12. The three reverse pull rods 12 are made of carbon fiber and are evenly distributed around the axis of the piezoelectric vibrator 10. The three evenly distributed rods are used to form a relatively balanced circumferential force transmission relationship at the tail end of the piezoelectric vibrator 10, reduce the eccentric load that may be caused by unilateral or dual-point force, and make the compensating mechanical force output by the annular reverse piston 13 closer to the axis of the piezoelectric vibrator 10. The carbon fiber material used meets the preset lower limit of specific stiffness and upper limit of mass requirements, which can reduce the additional inertia and improve the response consistency of tensile force transmission, thereby reducing the influence of the compensation mechanism itself on the dynamic characteristics of the piezoelectric vibrator 10; the intermediate partition plate 7 is provided with a guide hole 26 for the reverse tie rod 12 to pass through. The guide hole 26 is used to limit the passage path of the reverse tie rod 12, so that the connection force between the flattened rear cavity 8 and the coupling front cavity 9 is transmitted in a predetermined direction, reducing lateral movement; A dynamic sealing ring 27 is provided at the guide hole 26 to maintain the airtight separation between the two chambers when the reverse tie rod 12 undergoes axial micro-displacement, and to avoid reducing the consistency of the synchronous negative pressure state due to leakage of the guide hole 26. In the technical implementation, one end of the three reverse tie rods 12 is connected to the tail end of the piezoelectric vibrator 10, and the other end is connected to the end face of the annular reverse piston 13. When the negative pressure in the rear chamber 8 increases after the smoothing, the axial displacement generated by the movement of the annular reverse piston 13 is synchronously transmitted to the tail end of the piezoelectric vibrator 10 through the three reverse tie rods 12, thereby forming a mechanical compensation force opposite to the direction of the parasitic tensile stress. Because the number, material, and distribution of the reverse tie rods 12 work in conjunction with the guiding structure of the intermediate partition 7, the bending component of the piezoelectric vibrator 10 during the transmission of the compensating force is reduced, which helps to maintain the coaxial transmission state of the transmission shaft 11 at the front end of the piezoelectric vibrator 10 and improves the repeatability of the control module 6 in measuring the drift of the resistive resonant frequency.

[0024] The conductive shaft 11 is made of titanium alloy and extends forward to the opening end of the coupling front cavity 9; wherein, a closed space 28 is formed between the flexible polymer elastic membrane 14 and the front end face of the conductive shaft 11, and the silica particles 15 are micron-sized high-hardness particles and are filled in the closed space 28. In this embodiment, the transmission shaft 11 is made of titanium alloy and is coaxially connected to the piezoelectric vibrator 10. The transmission shaft 11 extends towards the opening of the coupling cavity 9, so that its front end and the flexible polymer elastic membrane 14 form a closed space 28 for filling the silica particles 15. The transmission shaft 11 is used to carry the mechanical transmission of the vibration of the building surface from the particulate medium to the piezoelectric vibrator 10. The technical consideration for using titanium alloy is that the material has a specific strength that meets the preset threshold, mechanical transmission performance within the preset fluctuation range, and additional mass influence below the preset upper limit, which can reduce the interference of the bending vibration of the transmission shaft 11 itself on the measurement results of the piezoelectric vibrator 10. The closed space 28 formed between the flexible polymer elastic membrane 14 and the front end face of the transmission shaft 11 is used to accommodate silica particles 15. The flexible polymer elastic membrane 14 defines the outer boundary of the space and provides conformity to the shape of the building surface. The front end face of the transmission shaft 11 defines the inner force boundary of the space and receives the vibration load transmitted by the particulate medium. The silica particles 15 have a particle size range of 1μm to 100μm. The silica particles 15 are selected from micron-sized high-hardness particles to maintain the flow and gap-filling ability that meets the preset porosity in a loosely packed state, and to build and form an equivalent stiffness greater than the preset stiffness threshold through the interparticle contact network under negative pressure. Here, micron-sized means that the particle size is in the range that can fill the tiny unevenness of the building surface and form a multi-point contact force transmission chain after being compressed. Its technical function is to take into account both surface compliance and the ability to build high-frequency vibration transmission channels. During the testing process, after the flexible polymer elastic membrane 14 is attached to the building surface, the silica particles 15 in the enclosed space 28 can flow and rearrange in an initial low stiffness state to fill the uneven areas of the surface. After the negative pressure is enhanced, the flexible polymer elastic membrane 14 contracts inward and applies a compaction effect to the silica particles 15, increasing the number of contact points between particles and forming a continuous force transmission path from the building surface to the front end of the transmission shaft 11. This structure can reduce the air gap reflection caused by the local suspension of the traditional rigid probe and reduce the dissipation of high frequency vibration by the pure flexible pad, so that the piezoelectric vibrator 10 can obtain higher fidelity building vibration frequency information in passive receiving mode.

[0025] The side wall of the balance housing 3 is provided with a negative pressure air inlet 29; wherein, the negative pressure air inlet 29 is connected to the miniature vacuum pump 16 through a pneumatic hose 30; In this embodiment, a negative pressure air inlet 29 is provided on the side wall of the balance housing 3. The negative pressure air inlet 29 is connected to the micro vacuum pump 16 through a pneumatic hose 30. The negative pressure air inlet 29 is used to introduce an external negative pressure source into the interior of the balance housing 3, so that the flattened rear cavity 8 and the coupling front cavity 9 can jointly receive negative pressure regulation through the connecting air passage 17. The technical consideration of setting it on the side wall is that it can avoid interference between the air inlet and the axial movement path of the propulsion module 2, and it is beneficial to maintain the integrity of the coupling structure at the front end of the balance housing 3. The pneumatic hose 30 is used to establish a flexible air path connection between the miniature vacuum pump 16 and the balance housing 3. This flexible connection can adapt to the relative displacement when the propulsion module 2 drives the balance housing 3 to make linear movements, reducing the additional traction of the rigid pipeline on the attitude of the balance housing 3. After the miniature vacuum pump 16 outputs negative pressure, the negative pressure is transmitted to the negative pressure inlet 29 through the pneumatic hose 30, and then distributed by the internal air path of the balance housing 3 to the smoothing rear cavity 8 and the coupling front cavity 9. The control module 6 adjusts the equivalent suction capacity of the input gas path by changing the pulse width modulation duty cycle of the micro vacuum pump 16, thereby changing the pressure difference on the flexible polymer elastic membrane 14 in the coupling front chamber 9 and smoothing the pressure difference on the annular reverse piston 13 in the rear chamber 8. By using the side wall negative pressure air inlet 29 and the pneumatic hose 30 connection method, the micro vacuum pump 16 can also be arranged at a position away from the piezoelectric vibrator 10, reducing the possibility that the vibration of the micro vacuum pump is directly coupled to the sensing coupling module 4 through the rigid structure. Thus, the negative pressure adjustment module 5 can adjust the stiffness of the particulate medium while helping to maintain the mechanical background stability of the piezoelectric vibrator 10 in the passive receiving stage.

[0026] The control module 6 has a preset nonlinear mapping relationship, which is characterized by the mapping relationship between the electrical impedance resonant frequency drift and the vibration coupling efficiency between the silica particles 15 and the building surface. In this embodiment, the control module 6 presets a nonlinear mapping relationship to establish the correspondence between the electrical impedance resonant frequency drift and the vibration coupling efficiency between the silica particles 15 and the building surface. The purpose of this nonlinear mapping relationship is to accurately estimate the current mechanical conduction efficiency of the silica particle 15 layer by means of the electrical characteristics that are easily obtained by the piezoelectric oscillator 10, in the case that the minute vibration transmission state inside the particle layer cannot be directly measured. In terms of logical structure and data flow, the mapping relationship includes a feature input module, a state classification sub-model, and a numerical mapping sub-model: the feature input module receives the impedance resonant frequency drift as the main input and combines it with the negative pressure intensity of the current micro vacuum pump 16 as an auxiliary input; the state classification sub-model determines the phase transition stage of the current particle layer based on the input features; the numerical mapping sub-model, based on the classification results, calls the mapping rules of the corresponding interval to calculate and output continuous vibration coupling efficiency values; The state classification sub-model uses a preset threshold judgment logic: when the input impedance resonant frequency drift is lower than the first preset threshold, it is judged as a loose phase transition stage; when it is between the first preset threshold and the second preset threshold, it is judged as a transitional phase transition stage; when it is higher than the second preset threshold, it is judged as a blocked phase transition stage. The first and second preset thresholds are obtained by performing a gradient negative pressure compaction experiment on silica particles under a standard reference interface and extracting the nonlinear inflection point characteristics of the change in electrical impedance resonant frequency with negative pressure. The numerical mapping sub-model is a pre-calibrated polynomial interpolation function corresponding to each phase transition stage, which is stored in the controller. In terms of the physical relationship, the mapping relationship as a whole characterizes the nonlinear modulation effect of the changes in the overall equivalent stiffness and effective contact area of ​​the silica particles 15 under different compaction states on the mechanical impedance of the front end of the piezoelectric oscillator 10. That is, it simulates the physical influence of the nonlinear stiffness growth law in the phase transition process of the particle medium from loose to blocked on the transmission attenuation of high frequency vibration waves. The nonlinear mapping relationship can be obtained through pre-calibration. During the calibration process, the impedance resonant frequency drift of the piezoelectric vibrator 10 is collected under different contact states and different negative pressure conditions. At the same time, the corresponding standard reference vibration transmission results are collected to construct a corresponding dataset between the two. The control module 6 then stores the dataset as a lookup table relationship, a piecewise function relationship, or a matrix mapping relationship. During detection, the control module 6 collects the current impedance resonant frequency drift and retrieves or calculates the corresponding vibration coupling efficiency value in the preset correspondence. The technical significance of this implementation is that it transforms the contact vibration transmission state, which is difficult to measure directly, into an electrical characteristic quantity that can be obtained by the self-test of the piezoelectric vibrator 10, and further transforms it into a control criterion that can be used for negative pressure adjustment. This makes the negative pressure adjustment action not dependent on a single mechanical displacement or a single contact pressure, but controlled based on a comprehensive characterization quantity related to the actual vibration transmission effect, thereby improving the adaptability of the silica particle 15-layer variable stiffness adjustment to building vibration detection tasks. The process of establishing nonlinear mapping relationships can be carried out in the following steps: Select several representative building material samples or standard reference interfaces, and establish multiple sets of calibration conditions under different propulsion contact amounts, different negative pressure intensities, and different particle compaction states; Under each set of calibration conditions, the control module 6 drives the piezoelectric vibrator 10 to complete frequency sweep self-test and extract the corresponding impedance resonant frequency drift. Meanwhile, by using a standard reference sensor, a comparative accelerometer, or the output response under a known excitation input, the reference vibration transmission result under this working condition is obtained; the frequency drift of each working condition is stored in correspondence with the reference vibration transmission result to form an original calibration dataset; the original calibration dataset is segmented and organized so that different drift ranges correspond to different vibration coupling efficiency ranges, resulting in a nonlinear mapping relationship that can be called by the control module 6. The reference vibration transmission results are preferably characterized by a normalized transmission capacity index, which has the physical meaning of the relative proportion of vibration components input from the building surface and effectively received by the piezoelectric vibrator 10 under the same external excitation; the control module 6 can use this normalized index as the calibration target value of vibration coupling efficiency. The preferred processing logic during detection is as follows: first, read the current impedance resonant frequency drift; then determine which preset interval the drift falls into; if it falls into a single interval, directly output the vibration coupling efficiency corresponding to that interval; if it falls near the boundary of an adjacent interval, interpolate or weighted smooth the efficiency values ​​corresponding to the two adjacent intervals to avoid frequent fluctuations in the duty cycle of the miniature vacuum pump 16 due to boundary jumps during the control adjustment process. The interpolation process is implemented using a linear interpolation algorithm: when the current impedance resonant frequency drift falls within a preset threshold... The calibration point and the first Between the calibration points, among which, It is a positive integer; control module 6 extracts the first... The drift amount at each calibration point and the corresponding vibration coupling efficiency, and the... The drift amount at each calibration point and the corresponding vibration coupling efficiency are used to calculate the real-time vibration coupling efficiency corresponding to the current drift amount using a two-point linear equation; the specific formula is as follows:

[0027] In the formula, This represents the current real-time vibration coupling efficiency; This represents the current impedance resonant frequency drift, in Hz. and Representing the first The calibration point and the first The amount of electrical impedance resonant frequency drift at each calibration point; and Representing the first The calibration point and the first The vibration coupling efficiency corresponding to each calibration point; the calculation result is output in the form of a normalized dimensionless floating-point number between 0 and 1, which serves as the direct input parameter for the subsequent duty cycle adjustment program of the micro vacuum pump 16, thereby clarifying the input processing rules and output data format of the nonlinear mapping at the software bottom layer; In addition to generating the current vibration coupling efficiency, the output of the nonlinear mapping relationship can also synchronously output the coupling state category, which includes at least three categories: insufficient coupling, moderate coupling, and excessive coupling. Among them, insufficient coupling corresponds to the low stiffness of the particle layer or the discontinuous state of the force transmission chain, moderate coupling corresponds to the vibration coupling efficiency being within the preset working range, and excessive coupling corresponds to the over-hardening of the particle layer and the potential for impedance mismatch. Thus, the nonlinear mapping relationship not only provides numerical control input but also state-type criteria, enabling the control module 6 to perform subsequent negative pressure adjustment based on a clear data source, mapping steps, and output flow direction.

[0028] Example 2: like Figure 4 As shown, a control method for a building safety detection device based on vibration frequency includes the following steps: S1: Initialize the equipment and control the propulsion module 2 to drive the balance shell 3 to move towards the building surface, so that the flexible polymer elastic membrane 14 and the internal silica particles 15 come into contact with the building surface. S2: Input a wideband self-test excitation electrical signal to the piezoelectric vibrator 10 and extract the amount of impedance resonant frequency drift of the piezoelectric vibrator 10 in the current state; S3: Based on the extracted impedance resonant frequency drift, the vibration coupling efficiency between the current silica particles 15 and the building surface is calculated using a preset nonlinear mapping relationship. S4: The pulse width modulation duty cycle of the micro vacuum pump 16 is dynamically scheduled according to the vibration coupling efficiency, and the negative pressure intensity in the coupling pre-cavity 9 is controlled to adjust the stiffness of the silicon dioxide particles 15. S5: During the negative pressure adjustment process, the negative pressure in the back chamber 8 increases synchronously, driving the annular reverse piston 13 to move backward, and applying a backward mechanical compensation pull force to the piezoelectric vibrator 10 through the reverse pull rod 12 to offset the parasitic tensile stress generated by the contraction of the flexible polymer elastic membrane 14. S6: After the negative pressure intensity stabilizes and a preset stabilization time has elapsed, control the piezoelectric vibrator 10 to stop sending self-test signals and switch to passive receiving mode. Collect high-frequency micro-vibration signals inside the building through the silica particles 15 medium, and obtain the building vibration frequency accordingly. In this embodiment, the control method is used to coordinate the working relationship between the propulsion module 2, the sensing coupling module 4, the negative pressure adjustment module 5, and the control module 6. In step S1, the initialization of the equipment includes establishing the reference impedance spectrum of the piezoelectric oscillator 10, setting the initial duty cycle of the micro vacuum pump 16, setting the initial displacement state of the propulsion module 2, and clearing the relevant acquisition channels. The propulsion module 2 drives the balance shell 3 to move towards the building surface, so that the flexible polymer elastic membrane 14 and the internal silica particles 15 form an initial fit with the building surface, wherein the silica particles 15 are in a flowable rearrangement state to fill the small unevenness of the building surface. In step S2, the control module 6 inputs a wideband self-test excitation signal to the piezoelectric vibrator 10 and collects the corresponding voltage, current or equivalent impedance response, and extracts the impedance resonant frequency drift in the current state; this drift is defined relative to the initial reference state and is used to reflect the changes in contact interface stiffness and vibration transmission boundary. In step S3, the control module 6 converts the electrical impedance resonant frequency drift into the vibration coupling efficiency between the current silica particles 15 and the building surface based on the preset nonlinear mapping relationship, and uses this as the calculation input for subsequent negative pressure adjustment. In step S4, the control module 6 dynamically schedules the pulse width modulation duty cycle of the micro vacuum pump 16 according to the deviation between the vibration coupling efficiency and the preset range, so as to change the negative pressure intensity in the coupling pre-cavity 9 and drive the silica particles 15 from a lower stiffness state to a higher stiffness state or vice versa; when the vibration coupling efficiency enters the preset range, it indicates that the contact compliance and vibration transmission stiffness have reached a balance relationship adapted to the detection target. In step S5, as the negative pressure in the coupling front chamber 9 changes, the negative pressure in the rear chamber 8 changes synchronously, driving the annular reverse piston 13 to move, and applying a mechanical compensation tension to the piezoelectric vibrator 10 via the reverse pull rod 12, in order to reduce the prestress interference caused by the shrinkage of the flexible polymer elastic membrane 14 and the compaction of particles. In step S6, after the negative pressure intensity remains stable and the prestress interference of the piezoelectric vibrator 10 is canceled, the control module 6 stops applying self-test excitation to the piezoelectric vibrator 10, causing the piezoelectric vibrator 10 to enter the passive receiving mode. It receives high-frequency micro-vibration signals inside the building through the silica particles 15 medium and the transmission shaft 11, and outputs the corresponding electrical signal. The control module 6 can perform frequency analysis on the output signal to obtain the building vibration frequency information. This control method integrates contact establishment, state identification, variable stiffness adjustment, and stress compensation into a unified process, which can reduce the coupling inconsistency problem caused by changes in surface roughness in traditional detection methods and improve the extractability of high-frequency vibration signals related to minor building defects. The optimal definition of sufficient fit in step S1 is that the flexible polymer elastic membrane 14 has been in continuous contact with the building surface and the silica particles 15 can cover and fill the main surface irregularities of the target detection area. The judgment method can be at least one of the following: the displacement of the propulsion module 2 reaches the preset approach amount, the impedance drift change corresponding to the displacement increment tends to be gradual when the propulsion continues after contact, or the initial coupling efficiency reaches the minimum starting threshold. The purpose of the minimum starting threshold is to avoid directly entering the negative pressure adjustment stage in a state of obvious non-contact or partial suspension. Steps S2 to S4 preferably constitute an iterative closed-loop process, specifically as follows: after a frequency sweep self-test, the current impedance resonant frequency drift is obtained; the control module 6 calculates the current vibration coupling efficiency based on the drift by looking up a table or interpolation; then, the coupling efficiency is compared with a preset range, and control commands are generated to increase the duty cycle, decrease the duty cycle, or keep the duty cycle unchanged; after the micro vacuum pump 16 executes the corresponding action, the system waits for a preset stabilization time to allow the cavity pressure and particle state to reach a new relatively stable state; the frequency sweep self-test is executed again and the above process is repeated until the vibration coupling efficiency falls into the preset range at least twice consecutively; The preset stabilization time is used to ensure that the contraction of the flexible polymer elastic membrane 14, particle rearrangement, and compensation action of the annular reverse piston 13 are basically completed after the negative pressure adjustment. It can be determined in advance by the prototype experiment. The mechanical compensation tension applied backward in step S5 with parasitic tensile stress is controlled by making the compensation tension correspond to the trend of the negative pressure change in the front cavity through the synchronous negative pressure structure relationship, rather than having to measure the precise value of parasitic tensile stress separately in real time. The judgment basis can be the characteristics of the piezoelectric oscillator 10 resonance feature, such as the additional drift of the resonance feature in two consecutive adjustments tending to converge, the baseline noise before passive reception decreasing, or the prestress sensitivity feature weakening. The steady state of zero prestress interference in step S6 is preferably understood as the piezoelectric oscillator 10 being in a working state where the influence of additional prestress can be ignored, rather than an absolute mechanical zero stress state. This steady state can be determined by the following logic: the duty cycle of the micro vacuum pump 16 remains unchanged within the preset observation period, the fluctuation of the characteristic frequency of the continuously acquired impedance is lower than the preset allowable fluctuation range, and the output baseline before passive reception does not have continuous drift. After reaching the steady state, the control module 6 stops the self-test excitation and starts to collect vibration signals. The collected signals are filtered, time-domain truncation and spectrum analysis are performed to obtain the vibration frequency information of the target building location. Thus, the input source, judgment threshold, loop relationship, stability criterion and output destination of steps S1 to S6 are clearly defined, so that the control method has a reproducible engineering execution path.

[0029] In step S4, the process of adjusting the stiffness of the silica particles 15 by controlling the negative pressure intensity in the coupling pre-cavity 9 includes: adjusting or maintaining the pulse width modulation duty cycle of the micro vacuum pump 16 control signal based on the deviation between the calculated vibration coupling efficiency and the preset range. In this embodiment, the variable stiffness adjustment in step S4 adopts a conditional control method based on vibration coupling efficiency. When the vibration coupling efficiency is lower than the preset threshold, it indicates that although the flexible polymer elastic membrane 14 and the building surface have formed a bond, the equivalent stiffness of the silica particle 15 layer is insufficient. The vibration energy of the building surface is dissipated in the particle layer beyond the preset attenuation threshold. Accordingly, the control module 6 increases the pulse width modulation duty cycle of the micro vacuum pump 16 control signal to increase the negative pressure intensity in the coupling pre-cavity 9. The variable stiffness adjustment here follows a clear physical response logic: under the action of enhanced negative pressure, the flexible polymer elastic membrane 14 contracts inward, applying an isotropic compaction effect to the internal silica particles 15; as the normal positive pressure between particles increases, the particle contact network changes from a free and rearrangeable fluid state to a motion-restricted solid-like state, thereby triggering a blocking phase transition; affected by the blocking phase transition, the overall equivalent stiffness of the particle assembly increases nonlinearly, which increases the number of small force transmission paths between the building surface and the transmission shaft 11 and enhances their continuity, resulting in a significant improvement in vibration coupling efficiency; When the vibration coupling efficiency exceeds the upper limit of the preset range, it indicates that the stiffness of the silica particle 15 layer is too high, which may cause an increase in the impedance matching deviation with the building surface and a decrease in local adhesion compliance. Accordingly, the control module 6 reduces the pulse width modulation duty cycle of the micro vacuum pump 16 control signal, releases part of the negative pressure, reduces the degree of internal contraction of the flexible polymer elastic membrane 14, reduces the normal positive pressure between silica particles 15, reduces the equivalent stiffness of the particle layer, and the vibration coupling efficiency returns to the preset range. The technical significance of this adjustment process lies in the fact that instead of using a single maximum negative pressure as the control target, the vibration coupling efficiency range is used as the adjustment basis, so that the silica particle 15 layer can maintain a controllable balance between its surface compliance filling capacity and high-frequency vibration transmission capacity. At the same time, since the negative pressure changes of the rear cavity 8 and the coupling front cavity 9 are synchronized, the parasitic tensile stress caused during the negative pressure enhancement or release process can be compensated by the annular reverse piston 13 and the reverse pull rod 12, thereby maintaining coordination between the particle layer stiffness adjustment action and the stable receiving state of the piezoelectric vibrator 10. The control module 6 implements the specific scheduling logic of the pulse width modulation duty cycle of the micro vacuum pump 16 using a deviation-based proportional adjustment algorithm: the control module 6 calculates the absolute value of the deviation between the current vibration coupling efficiency and the target median value of the preset interval, and multiplies this absolute value by a preset proportional gain coefficient to obtain the duty cycle adjustment amount; the formula for calculating the duty cycle adjustment amount is:

[0030] In the formula, The adjustment amount of the pulse width modulation duty cycle of the miniature vacuum pump, expressed as a percentage (%). The proportional gain coefficient is a preset value; the proportional gain coefficient is obtained through experimental calibration based on the rated pumping speed of the micro vacuum pump and the effective volume of the coupling front cavity. This is the actual real-time vibration coupling efficiency calculated at present. The vibration coupling efficiency is the target midpoint of the preset interval; when the vibration coupling efficiency is lower than the preset threshold, the current duty cycle is added to the adjustment amount as the new duty cycle output; when the vibration coupling efficiency exceeds the upper limit of the preset interval, the current duty cycle is subtracted from the adjustment amount as the new duty cycle output. Through the above data processing logic, the adjustment range of the duty cycle is directly related to the degree to which the current coupling efficiency deviates from the target state, avoiding the response lag or negative pressure overshoot oscillation that may be caused by using fixed step size adjustment, and ensuring the programmability of the variable stiffness control logic and the stability of system execution.

[0031] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A building safety detection device based on vibration frequency, characterized in that, include: A propulsion module (2) mounted on a base (1) and used to drive the linear movement of the balance housing (3); Installed at the propulsion end of the propulsion module (2), the internal structure is a balance shell (3) divided into a flattening rear cavity (8) and a coupling front cavity (9) by a middle partition (7). The sensing coupling module (4) includes a piezoelectric vibrator (10) suspended in the coupling front cavity (9), a conduction shaft (11) coaxially connected to its front end, a reverse pull rod (12) connected to its tail end through the middle partition (7) and connected to the annular reverse piston (13) in the flattening rear cavity (8), and a flexible polymer elastic membrane (14) filled with silica particles (15) fixed in the opening of the coupling front cavity (9). The system includes a connecting air passage (17) that opens into the balance shell (3) to connect the two chambers and a negative pressure regulating module (5) that connects the balance shell (3) to provide synchronous negative pressure to the two chambers; and a control module (6) that is electrically connected to the piezoelectric vibrator (10) and the micro vacuum pump (16) and configured to: extract the impedance resonant frequency drift of the piezoelectric vibrator (10) and adjust the negative pressure by regulating the pulse width modulation duty cycle of the micro vacuum pump (16); The annular reverse piston (13) is connected to the piezoelectric vibrator (10) via the reverse pull rod (12); the piezoelectric vibrator (10) is configured to switch to passive receiving mode after the vibration coupling efficiency reaches a preset range.

2. The building safety detection device based on vibration frequency according to claim 1, characterized in that, The propulsion module (2) includes: a linear stepper motor (18), a ball screw (19), a guide nut (20), and a hollow push rod (21); wherein the linear stepper motor (18) is fixedly connected to the tail of the base (1); The ball screw (19) is connected to the output spindle (22) of the linear stepper motor (18); the guide nut (20) is fitted onto the ball screw (19); the tail end of the hollow push rod (21) is fixedly connected to the guide nut (20), the hollow push rod (21) is inserted into the base (1), and the front end of the hollow push rod (21) is connected to the balance housing (3).

3. The building safety detection device based on vibration frequency according to claim 2, characterized in that, The base (1) is a cylindrical aluminum alloy base (1), and the linear stepper motor (18) is fixedly connected to the tail flange surface of the base (1) by bolts; wherein, the output spindle (22) of the linear stepper motor (18) is connected to the ball screw (19) through the plum blossom-shaped elastic coupling (23), and the hollow push rod (21) is supported in the inner hole of the base (1) through the linear sliding bearing (24).

4. The building safety detection device based on vibration frequency according to claim 1, characterized in that, The outer circle of the annular reverse piston (13) and the inner wall of the flattened cavity (8) are fitted with a clearance; wherein, a polyurethane sealing ring (25) is provided between the outer circle of the annular reverse piston (13) and the inner wall of the flattened cavity (8) to achieve sliding sealing.

5. The building safety detection device based on vibration frequency according to claim 1, characterized in that, The number of the reverse tie rods (12) is three. The three reverse tie rods (12) are made of carbon fiber and are evenly distributed. The middle partition plate (7) is provided with a guide hole (26) for the reverse tie rods (12) to pass through, and a dynamic sealing ring (27) is provided at the guide hole (26).

6. The building safety detection device based on vibration frequency according to claim 1, characterized in that, The conductive shaft (11) is made of titanium alloy and extends forward to the opening end of the coupling front cavity (9); wherein, the flexible polymer elastic membrane (14) and the front end face of the conductive shaft (11) form a closed space (28), and the silica particles (15) are micron-sized high-hardness particles and fill the closed space (28).

7. The building safety detection device based on vibration frequency according to claim 1, characterized in that, The side wall of the balance housing (3) is provided with a negative pressure air inlet (29); wherein the negative pressure air inlet (29) is connected to a micro vacuum pump (16) through a pneumatic hose (30).

8. The building safety detection device based on vibration frequency according to claim 1, characterized in that, The control module (6) has a preset nonlinear mapping relationship, which is characterized as the corresponding mapping relationship between the electrical impedance resonant frequency drift and the vibration coupling efficiency between the silica particles (15) and the building surface.

9. A control method for a building safety detection device based on vibration frequency, applied to the building safety detection device based on vibration frequency as described in claim 8, characterized in that, Includes the following steps: S1: Initialize the equipment and control the propulsion module (2) to drive the balance shell (3) to move towards the building surface, so that the flexible polymer elastic membrane (14) and the internal silica particles (15) come into contact with the building surface; S2: Input a wideband self-test excitation signal to the piezoelectric vibrator (10) and extract the impedance resonant frequency drift of the piezoelectric vibrator (10) in the current state; S3: Based on the extracted impedance resonant frequency drift, the vibration coupling efficiency between the current silica particles (15) and the building surface is calculated using a preset nonlinear mapping relationship. S4: Based on the vibration coupling efficiency, dynamically schedule the pulse width modulation duty cycle of the micro vacuum pump (16) to control the negative pressure intensity in the coupling pre-cavity (9) to adjust the stiffness of the silica particles (15). S5: During the negative pressure adjustment process, the negative pressure in the flattened cavity (8) increases synchronously, driving the annular reverse piston (13) to move backward, and applying a backward mechanical compensation pull force to the piezoelectric vibrator (10) through the reverse pull rod (12) to offset the parasitic tensile stress generated by the contraction of the flexible polymer elastic membrane (14); S6: After the negative pressure intensity is stable and a preset stabilization time has elapsed, control the piezoelectric vibrator (10) to stop sending self-test signals and switch to passive receiving mode. Collect high-frequency micro-vibration signals inside the building through the silica particle (15) medium, and obtain the building vibration frequency accordingly.

10. The control method for the building safety detection device based on vibration frequency according to claim 9, characterized in that, In step S4, the process of adjusting the stiffness of the silica particles (15) by controlling the negative pressure intensity in the coupling cavity (9) includes: adjusting or maintaining the pulse width modulation duty cycle of the micro vacuum pump (16) control signal based on the deviation between the calculated vibration coupling efficiency and the preset range.

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