Broadband dynamic force sensing device

Abstract

The utility model discloses a broadband dynamic force sensing device, which comprises a main body assembly, and the main body assembly comprises a base, a rubber ring, a spring, a metal sheet, a piezoelectric ceramic sheet and a strain gauge. According to the utility model, the piezoelectric ceramic piece is adopted to sense the high-frequency-band dynamic force, the strain gauge is adopted to sense the low-frequency-band dynamic force, the piezoelectric ceramic piece and the strain gauge cooperate to acquire signals, the signals are processed by the signal fusion module to realize the coverage of the full-frequency-band dynamic force, and the frequency band limitation of a single sensing element is avoided; the shell and the inner shielding layer form a double-layer structure to suppress electromagnetic interference, the temperature sensor monitors in real time and compensates temperature influence through a circuit, the rubber ring absorbs external vibration through elastic deformation, interference caused by electromagnetism, temperature and vibration is reduced in a multi-dimensional mode, and signal stability is improved; an optimized elastic body structure is formed through the four beam arms on the outer side of the center column, stress distribution is more linear through design, cross interference between force / torque of all dimensions is reduced in combination with a signal processing algorithm, and the multi-dimensional measurement precision is improved.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, specifically a broadband dynamic force sensing device. Background Technology

[0002] Dynamic force sensors, as core devices for measuring dynamic loads, have wide applications in aerospace, industrial automation, medical surgery, robotics, and other fields. For example, in wind tunnel testing of aircraft, it is necessary to monitor high-frequency changes in aerodynamic loads in real time; in industrial stamping presses, it is necessary to capture instantaneous impact forces; and in remote surgery, it is necessary to accurately feed back the operating forces of instruments.

[0003] Existing dynamic force sensors suffer from several technical bottlenecks, including insufficient bandwidth coverage, poor low-frequency response but high-frequency distortion, high-frequency coverage but low-frequency leakage, multi-field interference coupling (electromagnetic, temperature, and mechanical vibration leading to decreased signal-to-noise ratio), lag in dynamic response (millisecond-level response makes it difficult to capture sub-millisecond transient forces), and difficulties in multi-dimensional decoupling (traditional elastomer design suffers from severe cross-interference). To address these issues, a broadband dynamic force sensing device is proposed. Utility Model Content

[0004] The purpose of this invention is to provide a broadband dynamic force sensing device to solve one of the problems mentioned in the background art.

[0005] This utility model is implemented by the following technical solution: a broadband dynamic force sensing device, including a main component, the main component including a base, a rubber ring, a spring, a metal sheet, a piezoelectric ceramic sheet, a central column, a screw hole, a bolt, a beam arm and a strain gauge;

[0006] A rubber ring is fixedly connected to the outer side of the center of the upper surface of the base. A spring is attached to the upper surface of the rubber ring. A metal sheet is attached to the top of the spring. A piezoelectric ceramic sheet is attached to the upper surface of the metal sheet. A central column is fixedly connected to the upper surface of the piezoelectric ceramic sheet. A screw hole is opened at the center of the lower surface of the central column. A bolt passes through the center of the bottom of the base. The rubber ring and spring are sleeved on the lower part of the outer wall of the bolt. The top of the bolt passes through the center of the bottom of the metal sheet and the piezoelectric ceramic sheet. The top of the outer wall of the bolt is threaded to the inner wall of the screw hole. Four beam arms are fixedly connected to the middle of the outer wall of the central column. Strain gauges are fixedly connected to the upper surface of the four beam arms near the central column.

[0007] As a further preferred embodiment of this technical solution: a mounting groove is provided on one side of the upper surface of the base, a circuit board is provided inside the mounting groove, a signal fusion module is provided in the middle of the upper surface of the circuit board, and the piezoelectric ceramic sheet and strain gauge are both electrically connected to the signal fusion module.

[0008] As a further preferred embodiment of this technical solution: a temperature sensor is fixedly connected to the outer side wall of the central column near the upper part of the piezoelectric ceramic sheet, and the temperature sensor is electrically connected to the circuit board.

[0009] As a further preferred embodiment of this technical solution: an external threaded connecting ring is welded to the outer side of the upper surface of the base, and a shell is threaded to the outer side wall of the external threaded connecting ring. A force-loaded connector is fixedly connected to the top of the central column, and the top of the force-loaded connector penetrates through the center of the inner top wall of the shell.

[0010] As a further preferred embodiment of this technical solution, a shielding layer is fixedly connected to the inner wall of the outer shell.

[0011] As a further preferred embodiment of this technical solution: a sealing ring is attached to the upper surface of the base near the outer side of the external threaded connecting ring, and the upper surface of the sealing ring is attached to the lower surface of the outer shell.

[0012] As a further preferred embodiment of this technical solution: an RS interface and an Ethernet interface are provided on one side of the middle portion of the outer side wall of the housing.

[0013] As a further preferred embodiment of this technical solution: multiple mounting feet are welded to the bottom of the outer side wall of the base, and mounting holes are opened at the center of the upper surface of each of the multiple mounting feet.

[0014] Advantages of this utility model:

[0015] 1. This utility model uses a piezoelectric ceramic sheet to sense high-frequency dynamic force and a strain gauge to sense low-frequency dynamic force. The two work together to collect signals, which are then processed by a signal fusion module to achieve full-frequency dynamic force coverage, thus avoiding the bandwidth limitations of a single sensing element.

[0016] 2. This utility model suppresses electromagnetic interference by forming a double-layer structure with the outer shell and the inner shielding layer. The temperature sensor monitors in real time and compensates for the temperature effect through the circuit. The rubber ring absorbs external vibration through elastic deformation. It reduces the interference caused by electromagnetic, temperature and vibration in multiple dimensions and improves the signal stability.

[0017] 3. This utility model forms an optimized elastic body structure through four beam arms on the outside of the central column. The design makes the stress distribution more linear, and combined with signal processing algorithms, it reduces the cross interference between forces / torques in various dimensions, thereby improving the accuracy of multi-dimensional measurements. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0020] Figure 2 This is a schematic diagram of the overall cross-sectional structure of this utility model;

[0021] Figure 3 This is a schematic diagram of the base and central column structure of this utility model;

[0022] Figure 4 This is a schematic diagram of the beam arm and piezoelectric ceramic sheet structure of this utility model.

[0023] In the diagram: 1. Main component; 11. Base; 12. Rubber ring; 13. Spring; 14. Metal sheet; 15. Piezoelectric ceramic sheet; 16. Central column; 17. Screw hole; 18. Bolt; 19. Beam arm; 20. Strain gauge; 21. Mounting groove; 22. Circuit board; 23. Signal fusion module; 24. Temperature sensor; 25. External threaded connecting ring; 26. Housing; 27. Force loading connector; 28. Shielding layer; 29. ​​Sealing ring; 30. RS485 interface; 31. Ethernet interface; 32. Mounting foot; 33. Mounting hole. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] Example

[0026] Please see Figures 1-4 This utility model provides a technical solution: a broadband dynamic force sensing device, including a main component 1, which includes a base 11, a rubber ring 12, a spring 13, a metal sheet 14, a piezoelectric ceramic sheet 15, a central column 16, a screw hole 17, a bolt 18, a beam arm 19, and a strain gauge 20.

[0027] A rubber ring 12 is fixedly connected to the outer side of the center of the upper surface of the base 11. A spring 13 is attached to the upper surface of the rubber ring 12. A metal sheet 14 is attached to the top of the spring 13. A piezoelectric ceramic sheet 15 is attached to the upper surface of the metal sheet 14. A central column 16 is fixedly connected to the upper surface of the piezoelectric ceramic sheet 15. A screw hole 17 is opened at the center of the lower surface of the central column 16. A bolt 18 passes through the center of the bottom of the base 11. The rubber ring 12 and the spring 13 are sleeved on the lower part of the outer wall of the bolt 18. The top of the bolt 18 passes through the center of the bottom of the metal sheet 14 and the piezoelectric ceramic sheet 15. The top of the outer wall of the bolt 18 is threaded to the inner wall of the screw hole 17. The outer wall of the central column 16... The unit is fixedly connected to four beam arms 19, and strain gauges 20 are fixedly connected to the upper surface of the four beam arms 19 near the central column 16. A pre-tightening structure is formed by bolts 18, springs 13, metal plates 14 and piezoelectric ceramic plates 15. When the bolts 18 are tightened, the springs 13 are compressed, and an upward pre-pressure is generated through elastic deformation. This pre-pressure is evenly transmitted to the piezoelectric ceramic plates 15 through the metal plates 14, so that the piezoelectric ceramic plates 15 are tightly clamped between the metal plates 14 and the central column 16, forming a stable rigid contact. This ensures that there is no gap or loosening during the transmission of high-frequency dynamic force, avoiding signal distortion. At the same time, the pre-pressure (adjusted by the bolt tightening degree, usually set to 50N) can optimize the linear response characteristics of the piezoelectric ceramic plates 15.

[0028] Among them, the rubber ring 12 is a three-layer superimposed EPDM rubber pad;

[0029] The piezoelectric ceramic sheet 15 is used to sense dynamic forces in the high-frequency range (100Hz-20kHz). When an external high-frequency dynamic force is transmitted to the piezoelectric ceramic sheet 15 through the central column 16, it generates an electric charge signal due to the piezoelectric effect (the direct conversion characteristic of mechanical energy to electrical energy), converting the mechanical energy of the high-frequency dynamic force into a measurable electrical signal. This, combined with the pre-tightening structure (the 50N pre-pressure applied by the spring 13 and the metal sheet 14 through the bolt 18), ensures rigid contact and avoids high-frequency signal distortion.

[0030] The strain gauge 20 is used to sense dynamic forces in the low-frequency range (0.01Hz-5kHz). When the external low-frequency dynamic force is transmitted to the four beam arms 19 through the central column 16, the root of the beam arm 19 undergoes a small bending deformation (strain). The strain gauge 20 generates a change in resistance with the deformation. The strain (mechanical energy) is converted into a voltage signal through the full-bridge circuit, accurately capturing the small deformation of the low-frequency dynamic force and providing low-frequency signal support for broadband dynamic force measurement.

[0031] The two work together to cover the perception of dynamic forces across the entire frequency band from 0.01Hz to 20kHz, providing raw sensing data for the broadband signal reconstruction of the subsequent signal fusion module 23.

[0032] In this embodiment, specifically: a mounting groove 21 is provided on one side of the upper surface of the base 11, a circuit board 22 is provided inside the mounting groove 21, a signal fusion module 23 is provided in the middle of the upper surface of the circuit board 22, and the piezoelectric ceramic sheet 15 and the strain gauge 20 are both electrically connected to the signal fusion module 23.

[0033] The signal fusion module 23 is used to perform collaborative processing on the high-frequency dynamic force signal (100Hz-20kHz) collected by the piezoelectric ceramic sheet 15 and the low-frequency dynamic force signal (0.01Hz-5kHz) collected by the strain gauge 20, and realizes the reconstruction and optimization of the broadband force signal through the algorithm.

[0034] In this embodiment, specifically: a temperature sensor 24 is fixedly connected to the outer wall of the central column 16 near the upper part of the piezoelectric ceramic sheet 15. The temperature sensor 24 is electrically connected to the circuit board 22. The temperature sensor 24 facilitates the detection of the ambient temperature around the piezoelectric ceramic sheet 15 and the real-time temperature of the central column 16, providing core data support for temperature compensation for broadband dynamic force measurement.

[0035] In this embodiment, specifically: an external threaded connecting ring 25 is welded to the outer side of the upper surface of the base 11, and a housing 26 is threaded to the outer side wall of the external threaded connecting ring 25. A force-loaded connector 27 is fixedly connected to the top of the central column 16. The top of the force-loaded connector 27 penetrates through the center of the inner top wall of the housing 26. The housing 26 facilitates the protection of internal components and shields interference signals.

[0036] In this embodiment, specifically: a shielding layer 28 is fixedly connected to the inner sidewall of the outer shell 26, and the shielding layer 28 further shields interference signals.

[0037] In this embodiment, specifically: a sealing ring 29 is attached to the outer side of the upper surface of the base 11 near the external threaded connecting ring 25. The upper surface of the sealing ring 29 is attached to the lower surface of the outer shell 26. The sealing ring 29 seals the connection between the base 11 and the outer shell 26, thereby preventing moisture and dust from entering the interior and causing damage.

[0038] In this embodiment, specifically: an RS485 interface 30 and an Ethernet interface 31 are provided on one side of the middle of the outer wall of the outer casing 26. The broadband dynamic force data (including six-dimensional force / torque, temperature compensation value, etc.) processed by the signal fusion module 23 can be transmitted to the host computer or control system in real time through the RS485 interface 30 and the Ethernet interface 31. Among them, the RS485 interface 30 is based on the MODBUS-RTU protocol and the default baud rate is 115200bps; the Ethernet interface 31 is based on the TCP / IP protocol and supports 10 / 100Mbps adaptive.

[0039] In this embodiment, specifically: multiple mounting feet 32 ​​are welded to the bottom of the outer side wall of the base 11, and mounting holes 33 are opened at the center of the upper surface of the multiple mounting feet 32, so that the base 11 can be installed through the mounting holes 33 on the mounting feet 32.

[0040] In terms of working principle or structural principle, during use, external dynamic force is transmitted to the central column 16 through the force loading connector 27, and then splits into two paths:

[0041] Low-frequency force (0.01Hz-5kHz) is transmitted to the four beam arms 19 through the central column 16, causing a small bending deformation (strain) at the root of the beam arm 19. The strain gauge 20 attached here senses the deformation and converts it into an electrical signal.

[0042] The high-frequency force (100Hz-20kHz) is transmitted to the piezoelectric ceramic sheet 15 (PZT-5H) through the bottom of the central column 16. The piezoelectric ceramic sheet 15 generates an electric charge signal due to the piezoelectric effect. The pre-tightening structure (spring 13 and metal sheet 14 apply a 50N pre-pressure through bolt 18) ensures rigid contact and avoids signal distortion.

[0043] The specific circuit connection and signal conversion process are as follows:

[0044] Strain gauge circuit (low-frequency acquisition): 4 strain gauges (20) form a full-bridge circuit, with a power supply voltage of 5V. The strain gauge output voltage formula is:

[0045] ;

[0046] Where K = 2.1 (strain gauge sensitivity coefficient), ε is the strain value (ε = ΔL / L, proportional to force); the signal is input to the ADC interface of circuit board 22 after passing through an instrumentation amplifier (AD620, gain 1000 times) and a second-order RC low-pass filter (cutoff frequency 5kHz);

[0047] The formula for the charge signal generated by the piezoelectric ceramic sheet 15 is:

[0048] Q=d 33 ×F;

[0049] Where, d 33 =593pC / N (piezoelectric coefficient), F is the high-frequency dynamic force; the charge is converted into a voltage signal by a charge amplifier (AD549):

[0050] ;

[0051] Among them, C f =1000pF is the feedback capacitor, with a gain of 1000pF / V, and then it is input to the ADC after impedance matching by a high-speed comparator (LM311);

[0052] Meanwhile, the temperature sensor 24 is attached to the central post near the piezoelectric ceramic plate 15, and outputs a voltage signal (U). T =0.5V+10mV / ℃) is amplified by PGA (AD8253) and then synchronously input to FPGA with the force signal;

[0053] For the thermal expansion of elastomers (temperature coefficient 23.6 ppm / ℃) and the temperature drift of piezoelectric materials (-0.02% / ℃), dynamic correction is achieved through a PID algorithm:

[0054] ;

[0055] Among them, K p The proportionality coefficient (obtained through calibration) is used, with T0=25℃ as the reference temperature, and the temperature error after compensation is <0.5%FS;

[0056] After temperature compensation, the strain and piezoelectric signals are input to a 16-bit ADC (ADS127L01, sampling rate 1MHz) to complete analog-to-digital conversion. The converted data is then filtered in real time by an FPGA.

[0057] The filtering calculation uses a 5th-order Butterworth bandpass filter, with the transfer function as follows:

[0058] ;

[0059] Where H(s) is the complex frequency domain transfer function of the filter, used to describe the frequency domain response relationship between the output and input of the input signal after passing through the filter; ω c The cutoff angular frequency is the boundary angular frequency that divides the filter into the "passband" and "stopband", determining the frequency range that the signal is allowed to pass through; a4, a3, a2, and a1 are the fixed coefficients of the 5th order Butterworth polynomial, determined by the filter order n=5, reflecting the core characteristic of the Butterworth filter that "has the flattest passband amplitude-frequency response".

[0060] The cutoff frequency is 20kHz to ensure no signal attenuation within 20kHz and a signal delay of <1μs.

[0061] The two digital signals output from the FPGA are fed into the signal fusion module 23 (based on CNN), and fusion is achieved through a 12-layer residual network.

[0062] The weighting of low-frequency signals (strain) and high-frequency signals (piezoelectric) is determined by the following formula:

[0063] ;

[0064] Wherein, α is the frequency adaptive weight (α≈1 when 0.01Hz-100Hz, α≈0 when 10kHz-20kHz, and dynamically adjusted in the intermediate frequency band), the fusion error is <0.5%FS, and the 0.01Hz-20kHz full frequency band signal is finally reconstructed;

[0065] The stress distribution and six-dimensional force (F) of the cross-beam-column elastic body were optimized using the finite element method. x ,F y ,F z M x M y M z There exists a linear mapping relationship, which can be addressed using a decoupling matrix algorithm:

[0066] ;

[0067] Where K is the calibration matrix (obtained by loading a six-dimensional force standard machine), U1-U6 are the characteristic values ​​of the strain gauge and the piezoelectric signal, and the crosstalk after decoupling is <0.5%FS;

[0068] The outer shell 26 and the shielding layer 28 form a double-layer shield. Combined with multi-point grounding (grounding resistance < 1Ω), the electromagnetic interference suppression ratio is > 80dB. Calculation formula:

[0069] ;

[0070] The three-layer rubber ring has an elastic modulus of 5 MPa and absorbs over 90% of external vibrations through deformation. Vibration transmission rate:

[0071] ;

[0072] Where f0 is the resonant frequency of the rubber pad, and ξ is the damping ratio;

[0073] The processed six-dimensional force data is output via RS485 interface 30 or Ethernet interface 31 at a baud rate of 115200bps. The data frame format is as follows:

[0074] .

[0075] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A broadband dynamic force sensing device, characterized in that, Includes a main component (1), which includes a base (11), a rubber ring (12), a spring (13), a metal sheet (14), a piezoelectric ceramic sheet (15), a central column (16), a screw hole (17), a bolt (18), a beam arm (19), and a strain gauge (20). A rubber ring (12) is fixedly connected to the outer side of the center of the upper surface of the base (11). A spring (13) is attached to the upper surface of the rubber ring (12). A metal sheet (14) is attached to the top of the spring (13). A piezoelectric ceramic sheet (15) is attached to the upper surface of the metal sheet (14). A central column (16) is fixedly connected to the upper surface of the piezoelectric ceramic sheet (15). A screw hole (17) is opened at the center of the lower surface of the central column (16). The bottom center of the base (11) is penetrated through the screw hole (17). There is a bolt (18), the rubber ring (12) and the spring (13) are sleeved on the lower part of the outer side wall of the bolt (18), the top of the bolt (18) passes through the center of the bottom of the metal sheet (14) and the piezoelectric ceramic sheet (15), the top of the outer side wall of the bolt (18) is threaded to the inner side wall of the screw hole (17), and four beam arms (19) are fixedly connected to the middle of the outer side wall of the central column (16). Strain gauges (20) are fixedly connected to the upper surface of the four beam arms (19) on the side near the central column (16).

2. The broadband dynamic force sensing device according to claim 1, characterized in that, The base (11) has an installation groove (21) on one side of its upper surface. A circuit board (22) is installed inside the installation groove (21). A signal fusion module (23) is installed in the middle of the upper surface of the circuit board (22). The piezoelectric ceramic sheet (15) and the strain gauge (20) are both electrically connected to the signal fusion module (23).

3. The broadband dynamic force sensing device according to claim 2, characterized in that, A temperature sensor (24) is fixedly connected to the outer wall of the central column (16) near the upper part of the piezoelectric ceramic sheet (15), and the temperature sensor (24) is electrically connected to the circuit board (22).

4. The broadband dynamic force sensing device according to claim 1, characterized in that, The outer side of the upper surface of the base (11) is welded with an external threaded connecting ring (25), and the outer side wall of the external threaded connecting ring (25) is threadedly connected to the outer shell (26). The top of the central column (16) is fixedly connected to a force-loaded connector (27), and the top of the force-loaded connector (27) penetrates through the center of the inner top wall of the outer shell (26).

5. A broadband dynamic force sensing device according to claim 4, characterized in that, The inner wall of the outer shell (26) is fixedly connected with a shielding layer (28).

6. The broadband dynamic force sensing device according to claim 4, characterized in that, A sealing ring (29) is attached to the upper surface of the base (11) near the outer side of the external threaded connecting ring (25), and the upper surface of the sealing ring (29) is attached to the lower surface of the outer shell (26).

7. A broadband dynamic force sensing device according to claim 4, characterized in that, An RS485 interface (30) and an Ethernet interface (31) are provided on one side of the middle of the outer wall of the outer casing (26).

8. A broadband dynamic force sensing device according to claim 1, characterized in that, The bottom of the outer side wall of the base (11) is welded with a plurality of mounting feet (32), and mounting holes (33) are provided at the center of the upper surface of the plurality of mounting feet (32).

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