A piezoelectric ceramic-based through-contact detection sensor

Abstract

The application relates to a contact detection sensor, in particular to a piezoelectric ceramic-based through-contact detection sensor. The piezoelectric ceramic-based through-contact detection sensor comprises a shell with a through hole in the center and a containing cavity surrounding the lateral side of the through hole, the through hole is not communicated with the containing cavity; a piezoelectric ceramic assembly is located in the containing cavity and comprises a piezoelectric ceramic; an insulation assembly is arranged between the piezoelectric ceramic and the shell; a signal processing assembly comprises at least two charge amplifiers which are connected with corresponding piezoelectric ceramics respectively; and a power supply assembly provides working voltage for the piezoelectric ceramic assembly and the signal processing assembly. The application has the advantages of improving detection precision, not affecting normal use of a lens / bit head and facilitating wiring.

Description

Technical Field

[0001] This invention relates to a contact detection sensor, specifically a through-type contact detection sensor based on piezoelectric ceramics. Background Technology

[0002] Ultra-precision technology is widely used in the manufacturing processes of optical free surfaces (lenses, mirrors, windows, laser elements), micro / nano structured surfaces (microlens arrays, microprism arrays, compound eye microstructure arrays), and precision molds required for military weapons. In ultra-precision machining, white light interferometers are typically used, with contact sensors mounted on the lens side. When the contact sensor detects a small force on the lens, it sends a signal in real time to cause the actuator to deflect the lens, thus preventing collisions. However, this approach has several drawbacks: the contact sensor is positioned too far from the lens, or it may be placed against the circumference of the lens, increasing its size. Strain gauge contact sensors, such as the pressure sensor described in application number 202180059986.8, are generally used, but they have lower detection accuracy, slower feedback response, and the varying wiring positions lead to complex structures, which are detrimental to the use of ultra-precision machining equipment. Summary of the Invention

[0003] The purpose of this invention is to provide a piezoelectric ceramic-based through-hole contact detection sensor that can improve detection accuracy, does not affect the normal use of the lens / blade head, and facilitates wiring.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a through-hole contact detection sensor based on piezoelectric ceramics, comprising: a housing having a through hole at the center and a receiving cavity surrounding the circumferential side of the through hole, wherein the through hole and the receiving cavity are not connected; a piezoelectric ceramic assembly located within the receiving cavity, comprising piezoelectric ceramics, wherein when a contact force is applied to the housing, the piezoelectric ceramics generate a charge signal due to the piezoelectric effect; an insulation component disposed between the piezoelectric ceramics and the housing, used to achieve insulation between the two and prevent loss of charge signal; a signal processing component comprising at least two charge amplifiers, respectively connected to the corresponding piezoelectric ceramics, used to convert the charge signal generated by the piezoelectric ceramics into a measurable voltage signal, and to compensate for signal errors caused by environmental temperature drift and other factors by subtracting the signals from the two charge amplifiers; and a power supply component providing operating voltage to the piezoelectric ceramic assembly and the signal processing component to ensure the normal operation of the sensor.

[0005] The housing of this invention adopts a central through-type structure, which facilitates the layout of internal circuits and optical paths, meets the space utilization requirements of ultra-precision machining equipment, avoids messy circuits, simplifies the equipment structure, and is easy to use; the lens and the cutting head can be directly fixed on the axial front side of the housing, and the detection sensor is closer to the force point, which not only results in a faster response but also ensures detection accuracy.

[0006] The insulating sheet prevents the loss of charge signals, ensuring accurate transmission of the charge signals generated by the piezoelectric ceramics to the signal processing components and improving detection accuracy. Piezoelectric ceramics are sensitive to minute mechanical stresses and can accurately detect weak contact forces acting on the outer shell, making them suitable for high-precision detection scenarios. This invention, by rationally arranging multiple piezoelectric ceramic components within the receiving cavity, can detect contact forces from different directions, providing comprehensive force information. Furthermore, the use of two charge amplifiers to perform differential signal processing effectively compensates for signal errors caused by environmental temperature drift and other factors, improving detection accuracy and reliability.

[0007] Preferably, the housing includes a first housing and a second housing arranged sequentially along the axial direction of the through hole. Both the first and second housings include an inner ring portion and an outer ring portion, with a connecting portion connecting the inner and outer ring portions. The inner cavity is formed between the connecting portions on both axial sides, the inner ring portion on the inner side of the circumference, and the outer ring portion on the outer side of the circumference. The piezoelectric ceramic is located close to the first housing, and the insulating component is provided between at least the connecting portion of the first housing and the piezoelectric ceramic. This facilitates the installation of the piezoelectric ceramic assembly, signal processing assembly, and power supply assembly, improving assembly accuracy and efficiency.

[0008] Preferably, the chamber is provided with at least two piezoelectric ceramic components arranged in a ring-shaped interval. This ring-shaped interval layout helps reduce errors and interference that may arise from single-point detection. Even if one piezoelectric ceramic component is subject to localized interference or damage, the other components can still function normally, thereby improving the stability and fault tolerance of the entire sensor system. By using spaced piezoelectric ceramic components in conjunction with differential signal processing technology, signal errors caused by environmental factors such as temperature drift can be effectively compensated, further improving detection accuracy and reducing the impact of environmental factors on the detection results.

[0009] Preferably, both the piezoelectric ceramic and the insulating sheet are annular and have through holes. The piezoelectric ceramic and the insulating sheet are fixed to the housing by fasteners, which fit into the through holes. The annular shape of the piezoelectric ceramic and the insulating sheet with through holes facilitates connection and fixation to the housing, ensures stable operation of the piezoelectric ceramic, and prevents displacement or loosening from affecting the accuracy of detection.

[0010] Preferably, there are at least two piezoelectric ceramics and at least two charge amplifiers, with a one-to-one correspondence between the piezoelectric ceramics and the charge amplifiers. The difference between the signals of the two charge amplifiers can compensate for signal errors caused by environmental temperature drift, thereby improving the minimum threshold for contact force sensing.

[0011] Preferably, the piezoelectric ceramic is connected to the charge amplifier via a silver-plated signal line with a diameter of 0.3 mm. Using a 0.3 mm diameter silver-plated signal line to connect the piezoelectric ceramic and the charge amplifier results in low resistance, high conductivity, reduced signal transmission loss, and improved signal transmission efficiency and quality.

[0012] Preferably, the charge amplifier uses a high-precision operational amplifier chip as the core to form the amplification circuit, and is equipped with low-temperature drift capacitors and resistors to form a feedback loop to improve signal amplification accuracy and stability.

[0013] Preferably, the power supply assembly includes a voltage inverter and two linear regulators, with an input voltage of 5~9V DC and an output constant voltage of ±2.5V to power the charge amplifier. The voltage inverter and linear regulators convert the 5~9V DC voltage to a constant voltage of ±2.5V, providing a stable power supply to the charge amplifier, ensuring its normal operation, and improving system reliability.

[0014] Preferably, the voltage inverter includes an HT7660 chip and its peripheral circuitry, and the linear regulator includes a TPS7A4901 chip and its peripheral circuitry for forward voltage regulation, and a TPS7A3001 chip and its peripheral circuitry for reverse voltage regulation. Using the HT7660 chip for voltage inversion, and the TPS7A4901 and TPS7A3001 chips forming the forward and reverse voltage linear regulators respectively, offers advantages such as high precision, low noise, and good stability, ensuring output voltage accuracy and stability.

[0015] Preferably, the sensor output interface adopts an XH2.54-5P pluggable interface, with five wires corresponding to the positive power supply, ground power supply, charge amplifier signal, another charge amplifier signal, and signal ground. Using the XH2.54-5P pluggable interface, with five wires corresponding to the positive power supply, ground power supply, and charge amplifier signal, facilitates connection with other devices, enables rapid signal transmission, and improves device compatibility and versatility.

[0016] This invention has the advantages of improving detection accuracy, not affecting the normal use of the lens / blade head, and facilitating wiring. Attached Figure Description

[0017] Figure 1 This is an exploded view diagram according to an embodiment of the present invention.

[0018] Figure 2 This is a cross-sectional view of an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram illustrating the implementation principle of the charge amplifier in the sensor of this invention.

[0020] Figure 4 This is a schematic diagram illustrating the implementation principle of the voltage inverter in the power supply module of the sensor in this embodiment of the invention.

[0021] Figure 5 This is a schematic diagram illustrating the implementation principle of the linear regulator in the power supply module of the sensor in this embodiment of the invention.

[0022] Figure 6 This is a schematic diagram of a test result of a sensor according to an embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of another test result of the sensor in an embodiment of the present invention. Detailed Implementation

[0024] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0025] Depend on Figure 1 and Figure 2 As shown, this embodiment discloses a through-hole contact detection sensor based on piezoelectric ceramics, including a housing made of stainless steel alloy, a piezoelectric ceramic assembly, an insulating assembly, a signal processing assembly, and a power supply assembly. The housing has a centrally located through-hole for wiring and a surrounding cavity on the circumferential side of the through-hole; the through-hole and the cavity are not connected. The piezoelectric ceramic assembly, located within the cavity, includes a piezoelectric ceramic 9. When contact force is applied to the housing, the piezoelectric ceramic 9 generates a charge signal due to the piezoelectric effect. The insulating assembly, located between the piezoelectric ceramic 9 and the housing, includes a ceramic insulating sheet 8 to insulate the piezoelectric ceramic 9 from the housing, preventing charge signal loss. The signal processing assembly includes two charge amplifiers 5, each connected to a corresponding piezoelectric ceramic, to convert the charge signal generated by the piezoelectric ceramic 9 into a measurable voltage signal. The difference between the signals from the two charge amplifiers 5 compensates for signal errors caused by environmental temperature drift and other factors. The power supply assembly 10 provides operating voltage to the piezoelectric ceramic assembly and the signal processing assembly, ensuring the normal operation of the sensor.

[0026] The housing includes a first housing 3 and a second housing 4 arranged sequentially along the axial direction of the through hole. The first housing 3 is located in front of the second housing 4 and is fixed by fasteners 2. Both the first housing 3 and the second housing 4 include an inner ring portion and an outer ring portion, and a connecting portion connecting the inner ring portion and the outer ring portion. The inner cavity is formed between the connecting portion on both sides of the axial direction, the inner ring portion on the inner side of the circumference and the outer ring portion on the outer side of the circumference. The inner ring portion of the first housing 3 protrudes forward, and the inner ring portion of the second housing 4 protrudes backward. The outer circumferential wall of the inner ring portion of the first housing 3 and the outer circumferential wall of the inner ring portion of the second housing 4 are provided with threaded structures to facilitate connection with equipment and cutter head / lens.

[0027] The chamber contains two piezoelectric ceramic assemblies, which are symmetrically arranged. The piezoelectric ceramic 9 is located close to the first outer shell 3, and ceramic insulating sheets 8 are provided between the connection points of the piezoelectric ceramic 9 and the first outer shell 3 and the second outer shell 4. Both the piezoelectric ceramic 9 and the insulating sheets 8 are annular and have through holes for the fastener 2 to pass through. In this embodiment, the fastener 2 is used not only for assembling the outer shell but also for fixing the piezoelectric ceramic 8 and the insulating sheets 9 to the outer shell. The power supply assembly 10 is fixed to the outer shell by the first bolt 7, and the charge amplifier 5 is stacked inside the outer shell by studs 6. There are two piezoelectric ceramics 9 and two charge amplifiers 5, and each piezoelectric ceramic 9 corresponds to one charge amplifier 5. The piezoelectric ceramic 9 is connected to the charge amplifier 5 via a silver-plated signal wire (not shown in the figure) with a diameter of 0.3 mm.

[0028] When contact force is applied to the outer casing, the piezoelectric ceramic 9 generates a charge signal due to the piezoelectric effect. This signal is then converted into a measurable voltage signal by a charge amplifier. In this embodiment, the sensor output interface uses an XH2.54-5P pluggable interface. The five wires are for the positive power supply, the ground power supply, the two charge amplifier signals, the other charge amplifier signal, and the signal ground. When the two piezoelectric ceramics 9 are connected to the charge amplifier 5, the wiring of one piezoelectric ceramic is reversed compared to the other. Thus, when contact force is applied to the sensor, the two charge amplifiers 5 will output two signals with opposite polarities. Since temperature drift and other interferences are of the same polarity for the charge amplifier 5, the difference between the two signals can cancel out these interferences, resulting in a smaller contact force sensing threshold.

[0029] like Figure 3 As shown, a charge amplifier circuit is constructed with an LMP7721 operational amplifier as its core. A 10nF surface-mount capacitor C1 with low temperature drift and a 100MΩ surface-mount resistor R1 with low temperature drift form the feedback loop of the amplifier circuit. The temperature coefficient of the capacitor is less than 30ppm / ℃, and the temperature coefficient of the resistor is less than 10ppm / ℃. The amplification gain A is approximately...

[0030]

[0031] It is the unit of gain (F is the unit of capacitance, Farad), which represents the input charge signal being converted into a voltage signal and amplified by 10. 9 The charge is input from the QIN input stage. R2 is the input stage protection resistor, and R1 is used to unload the charge and stabilize the system. The voltage signal obtained from the charge conversion is output as V after passing through R3. out The LMP7721's non-inverting input stage is grounded and connected to a voltage follower formed by the LMP7715 via R5.

[0032] Depend on Figure 4 and Figure 5As shown, charge amplifier 5 uses a high-precision operational amplifier chip as the core to form the amplification circuit. The high-precision operational amplifier chip is LMP7721. The LMP7715 precision operational amplifier chip and its peripheral circuits form the protection loop of the charge amplifier circuit. R6 and C 10 These are the feedback resistor and capacitor of the voltage follower. Their output signal passes through R4 and is then output to the input stage protection loop (GUARD) of the LMP7721. The two charge amplifiers are compactly arranged on two chips with an area of ​​approximately 1.8 cm². 2 On the PCB board, the PCB boards are stacked in an alloy casing to increase space utilization. The PCB board adopts a 4-layer board structure, with the components concentrated on the first layer (located at the frontmost side of the axis), and the bottom layer containing filter capacitors (C2~C9).

[0033] The power supply assembly 10 consists of a voltage inverter and two linear regulators, arranged in an area of ​​2.8 cm². 2 On the PCB board, the power supply assembly 10 is connected to the charge amplifier 5 via a 0.3mm diameter silver-plated signal line. The power supply module has an input voltage of 5~9V DC and an output ±2.5V constant voltage to power the charge amplifier. Figure 4 As shown, the voltage inverter is composed of an HT7660 chip and its peripheral circuitry, with an input power supply V. DD After passing through the HT7660 chip, the voltage is inverted and stepped down to V. out =-V DD Voltage output. Additionally, a 10μF tantalum capacitor is connected to the CAP+ and CAP- terminals of the chip, and another 10μF tantalum capacitor is connected to the V- terminal of the chip. OUT The chip's LV and VSS pins are grounded, while the BOOST and OSC pins are left floating.

[0034] Of the two linear regulators, the forward voltage linear regulator is composed of a TPS7A4901 chip and its peripheral circuitry, while the reverse voltage linear regulator is composed of a TPS7A3001 chip and its peripheral circuitry. Input voltage V DD The voltage is stepped down to +2.5V and -V via a forward voltage linear regulator. DD The voltage is boosted to -2.5V via a reverse voltage linear regulator. The output voltages of the TPS7A4901 and TPS7A3001 are configured using feedback resistors, and the configuration scheme is the same. Figure 5 A schematic diagram of the TPS7A4901 feedback resistor configuration is provided. Output voltage V. out The relationship between the feedback resistors R1 and R2 is calculated as follows:

[0035]

[0036] Take R2 = 3.24 kΩ, when V outWhen the voltage is +2.5V, R1 = 3.6KΩ; C IN C NR / SS C FF C OUT It is a surface-mount ceramic capacitor packaged as C0603, and its capacitance value is given in the figure.

[0037] To verify the functionality of this invention, the sensor was tested using a 500mg weight from the M1 weight set. During testing, the sensor was placed vertically on a vibration isolation platform, with a tray larger than the sensor's central hole placed on top to hold the weight. The sensor was powered by a DP100 CNC power supply from Zhengdian Atom, with a supply voltage of 5V. Data acquisition was performed using an NIUSB-6210 data acquisition card. Figure 6 At approximately 4.5 seconds, the weight was placed on the tray. The sensor data is shown in the curve in the figure. Signal1 and Signal2 are the signals output by two charge amplifiers, with opposite polarities. It is worth noting that the signal contains a drift error of about -50mV, and there is also significant superimposed stage-by-stage interference noise (the three signal peaks shown in the figure originate from electromagnetic coupling interference), which almost completely obscures the signal at 4.5 seconds. Figure 7 The difference between the two signals is given, showing a significant reduction in signal noise and drift error, and an enhanced contact signal at 4.5 s. Using a gravitational acceleration of 9.8 mm / s², experiments demonstrate that the through-hole contact sensor based on piezoelectric ceramics described in this invention can effectively sense contact forces as low as 4.9 mN.

[0038] This embodiment has the advantages of improving detection accuracy, not affecting the normal use of the lens / blade, and facilitating wiring.

Claims

1. A through-type contact detection sensor based on piezoelectric ceramics, characterized in that... include: The outer casing has a through hole located at the center and a receiving cavity surrounding the circumferential side of the through hole, wherein the through hole and the receiving cavity are not in communication; A piezoelectric ceramic assembly, located within the receiving cavity, comprises a piezoelectric ceramic that generates an electric charge signal due to the piezoelectric effect when a contact force is applied to the housing; the receiving cavity is provided with at least two of the piezoelectric ceramic assemblies arranged in a ring-shaped interval. An insulating component is placed between the piezoelectric ceramic and the housing to achieve insulation between the two and prevent the loss of charge signal; The signal processing component includes at least two charge amplifiers, each connected to a corresponding piezoelectric ceramic, for converting the charge signal generated by the piezoelectric ceramic into a measurable voltage signal, and for compensating for signal errors caused by factors such as environmental temperature drift by subtracting the signals from the two charge amplifiers. The power supply unit provides operating voltage to the piezoelectric ceramic components and signal processing components, ensuring the normal operation of the sensor; The housing includes a first housing and a second housing arranged sequentially along the axial direction of the through hole. Both the first housing and the second housing include an inner ring portion and an outer ring portion, and a connecting portion connecting the inner ring portion and the outer ring portion. The receiving cavity is formed between the connecting portions on both sides of the axial direction, the inner ring portion on the inner side of the circumferential direction, and the outer ring portion on the outer side of the circumferential direction. The piezoelectric ceramic is close to the first housing, and the insulating component is provided between at least the connecting portion of the first housing and the piezoelectric ceramic.

2. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: Both the piezoelectric ceramic and the insulating sheet are annular and have through holes. The piezoelectric ceramic and the insulating sheet are fixed to the outer shell by fasteners, which fit into the through holes.

3. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: There are at least two piezoelectric ceramics and charge amplifiers, and there is a one-to-one correspondence between the piezoelectric ceramics and the charge amplifiers.

4. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: The piezoelectric ceramic is connected to the charge amplifier via a silver-plated signal line with a diameter of 0.3 mm.

5. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: The charge amplifier uses a high-precision operational amplifier chip as the core to form an amplification circuit, and is equipped with low-temperature drift capacitors and resistors to form a feedback loop.

6. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: The power supply assembly includes a voltage inverter and two linear regulators, with an input voltage of 5~9V DC and an output ±2.5V constant voltage to power the charge amplifier.

7. The through-type contact detection sensor based on piezoelectric ceramics according to claim 6, characterized in that: The voltage inverter includes an HT7660 chip and its peripheral circuitry. In the linear regulator, the forward voltage linear regulator includes a TPS7A4901 chip and its peripheral circuitry, and the reverse voltage linear regulator includes a TPS7A3001 chip and its peripheral circuitry.

8. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: The sensor output interface adopts an XH2.54-5P pluggable interface, with five wires for power supply positive, power supply ground, charge amplifier signal, another charge amplifier signal and signal ground.

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