Middle-through type contact detection sensor based on piezoelectric ceramics

Abstract

The invention relates to a contact detection sensor, in particular to a middle through type contact detection sensor based on piezoelectric ceramics. A middle-through type contact detection sensor based on piezoelectric ceramics comprises a shell which is provided with a through hole located in the center and a containing cavity surrounding the circumferential side of the through hole, and the through hole is not communicated with the containing cavity; the piezoelectric ceramic component is positioned in the accommodating cavity and comprises piezoelectric ceramic; the insulating component is arranged between the piezoelectric ceramic and the shell; the signal processing assembly comprises at least two charge amplifiers which are respectively connected with the corresponding piezoelectric ceramics; and the power supply assembly provides working voltage for the piezoelectric ceramic assembly and the signal processing assembly. The method has the advantages that the detection precision can be improved, normal use of the lens / tool bit is not affected, and wiring is facilitated.

Description

Technical Field

[0001] The present invention relates to a contact detection sensor, and more particularly to a central-through type contact detection sensor based on piezoelectric ceramics. Background Art

[0002] Ultra-precision technology is widely used in the manufacturing processes of optical free surfaces (lenses, mirrors, windows, laser components), micro-nano structure surfaces (microlens arrays, microprism arrays, compound eye micro-structure arrays), precision abrasives, etc. required for military weapons. When performing ultra-precision machining, a white light interferometer is usually used, and a contact sensor is provided on the lens side. When it is determined by the contact sensor that the lens is subjected to a small force, a signal is sent in real time to cause the actuator to drive the lens to deflect, thereby avoiding the lens from colliding. The above solutions have the following problems: the position of the contact sensor is far from the lens position, or it will be attached to the circumferential side of the lens, resulting in an increase in the volume of the lens. Generally, a strain type contact sensor is used, such as the pressure sensor with the application number 202180059986.8. The detection accuracy is low, the feedback response is slow, and the routing positions of the relevant lines are different, resulting in a complex structure and being not conducive to the use of ultra-precision machining equipment. Summary of the Invention

[0003] The object of the present invention is to provide a central-through type contact detection sensor based on piezoelectric ceramics that can improve the detection accuracy, does not affect the normal use of the lens / cutting tool, and is convenient for wiring.

[0004] To achieve the above object, the present invention adopts the following technical solution: A central-through type 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, the through hole and the receiving cavity being not communicated; a piezoelectric ceramic assembly located in the receiving cavity, including a piezoelectric ceramic, when a contact force is applied to the housing, the piezoelectric ceramic generates a charge signal due to the piezoelectric effect; an insulating assembly disposed between the piezoelectric ceramic and the housing for insulating the two and preventing the loss of the charge signal; a signal processing assembly including at least two charge amplifiers respectively connected to the corresponding piezoelectric ceramics for converting the charge signal generated by the piezoelectric ceramics into a measurable voltage signal and compensating for signal errors caused by factors such as environmental temperature drift by taking the difference between the signals of the two charge amplifiers; a power supply assembly for providing a working voltage for the piezoelectric ceramic assembly and the signal processing assembly to ensure the normal operation of the sensor.

[0005] The housing of the present invention adopts a central-through type structure, which is convenient for the layout of internal lines and optical paths, meets the requirements of ultra-precision machining equipment for space utilization, avoids messy lines, simplifies the equipment structure, and is conducive to use; the lens and the cutting tool can be directly fixed on the front side of the axial direction of the housing, and the detection sensor is closer to the force application point, not only with a faster response, but also can ensure the detection accuracy.

[0006] Among them, the insulating sheet prevents the loss of charge signals, ensures the accurate transmission of the charge signals generated by the piezoelectric ceramics to the signal processing component, and improves the detection accuracy. The piezoelectric ceramics are sensitive to tiny mechanical stresses and can accurately detect the weak contact forces acting on the outer shell, making them suitable for high-precision detection scenarios. In this invention, by reasonably arranging multiple piezoelectric ceramic components in the accommodation cavity, contact forces from different directions can be detected, providing comprehensive force information. Among them, two charge amplifiers are used to perform a difference operation on the signals, effectively compensating for signal errors caused by factors such as environmental temperature drift, and improving the detection accuracy and reliability.

[0007] Preferably, the outer shell includes a first outer shell and a second outer shell arranged in sequence along the axial direction of the through hole. Both the first outer shell and the second outer shell include an inner ring part, an outer ring part, and a connecting part connecting the inner ring part and the outer ring part. The inner cavity is formed between the connecting parts on both axial sides, the inner ring part on the circumferential inner side, and the outer ring part on the circumferential outer side; the piezoelectric ceramics are close to the first outer shell, and at least an insulating component is provided between the connecting part of the first outer shell and the piezoelectric ceramics. This facilitates the installation of the piezoelectric ceramic component, the signal processing component, and the power supply component, and can improve the assembly accuracy and efficiency.

[0008] Preferably, the chamber is provided with at least two piezoelectric ceramic components arranged at annular intervals. The annular interval layout helps to reduce errors and interference that may be caused by single-point detection. Even if a certain piezoelectric ceramic component is locally disturbed or damaged, other components can still work normally, thereby improving the stability and fault tolerance of the entire sensor system. Through the piezoelectric ceramic components arranged at intervals, combined with differential signal processing technology, signal errors caused by factors such as environmental temperature drift can be effectively compensated, further improving the detection accuracy and reducing the influence of environmental factors on the detection results.

[0009] Preferably, both the piezoelectric ceramics and the insulating sheet are annular and have through holes. The piezoelectric ceramics and the insulating sheet are fixed to the outer shell through the fasteners, and the fasteners are fitted at the through holes. The piezoelectric ceramics and the insulating sheet are annular and have through holes, which facilitate connection and fixation with the outer shell, ensure the stable operation of the piezoelectric ceramics, and prevent displacement or loosening from affecting the detection accuracy.

[0010] Preferably, there are at least two piezoelectric ceramics and at least two charge amplifiers, and the piezoelectric ceramics and the charge amplifiers correspond one by one. The difference between the signals of the two charge amplifiers can compensate for signal errors caused by environmental temperature drift, etc., and improve the minimum threshold of contact force perception.

[0011] Preferably, the piezoelectric ceramics are connected to the charge amplifiers through silver-plated signal wires with a diameter of 0.3 mm. Using silver-plated signal wires with a diameter of 0.3 mm to connect the piezoelectric ceramics and the charge amplifiers has low resistance and high conductivity, reduces signal transmission loss, and improves signal transmission efficiency and quality.

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

[0013] Preferably, the power supply component includes a voltage inverter and two linear voltage regulators. The input voltage is a DC voltage of 5-9V, and the output ±2.5V constant voltage supplies power to the charge amplifier. It is composed of a voltage inverter and a linear voltage regulator, which converts the 5-9V DC voltage into a ±2.5V constant voltage to provide a stable power supply for the charge amplifier, ensure its normal operation, and improve the system reliability.

[0014] Preferably, the voltage inverter includes an HT7660 chip and its peripheral circuit. Among the linear voltage regulators, the forward voltage linear voltage regulator includes a TPS7A4901 chip and its peripheral circuit, and the reverse voltage linear voltage regulator includes a TPS7A3001 chip and its peripheral circuit. The HT7660 chip is used to realize voltage inversion, and the TPS7A4901 and TPS7A3001 chips respectively form forward and reverse voltage linear voltage regulators, which have the advantages of high precision, low noise, and good stability, ensuring the output voltage accuracy and stability.

[0015] Preferably, the sensor output interface adopts an XH2.54-5P pluggable interface. The five wirings are respectively the power supply positive pole, the power supply ground pole, the charge amplifier signal, another charge amplifier signal, and the signal ground pole. The XH2.54-5P pluggable interface is adopted, and the five wirings respectively correspond to the power supply positive pole, the power supply ground pole, the charge amplifier signal, etc., which is convenient for connecting with other devices, realizes fast signal transmission, and improves the device compatibility and versatility.

[0016] The present invention has the advantages of improving the detection accuracy, not affecting the normal use of the lens / cutting tool, and being convenient for wiring. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is an exploded view of an embodiment of the present invention.

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

[0019] Figure 3 It is a schematic diagram of the implementation principle of the charge amplifier in the sensor of an embodiment of the present invention.

[0020] Figure 4 It is a schematic diagram of the implementation principle of the voltage inverter in the power supply module of the sensor of an embodiment of the present invention.

[0021] Figure 5 It is a schematic diagram of the implementation principle of the linear voltage regulator in the power supply module of the sensor of an embodiment of the present invention.

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

[0023] Figure 7 It is another schematic diagram of a test result of the sensor according to an embodiment of the present invention. Detailed implementation manners

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

[0025] As Figure 1 and Figure 2 shown, this embodiment discloses a middle-through contact detection sensor based on piezoelectric ceramics, which includes a housing made of stainless steel alloy, a piezoelectric ceramic component, an insulating component, a signal processing component, and a power supply component. Among them, the housing has a through hole located at the center for wire routing and a receiving cavity surrounding the circumferential side of the through hole, and the through hole is not communicated with the receiving cavity; the piezoelectric ceramic component is located in the receiving cavity and includes a piezoelectric ceramic 9. When a contact force is applied to the housing, the piezoelectric ceramic 9 generates a charge signal due to the piezoelectric effect; the insulating component is arranged between the piezoelectric ceramic 9 and the housing and includes a ceramic insulating sheet 8 for insulating between the piezoelectric ceramic 9 and the housing to prevent the loss of charge signals; the signal processing component includes two charge amplifiers 5, and the two charge amplifiers 5 are respectively connected to the corresponding piezoelectric ceramics for converting the charge signal generated by the piezoelectric ceramic 9 into a measurable voltage signal, and compensating for signal errors caused by factors such as environmental temperature drift through the difference of the signals of the two charge amplifiers 5; the power supply component 10 provides a working voltage for the piezoelectric ceramic component and the signal processing component to ensure the normal operation of the sensor.

[0026] The housing includes a first housing 3 and a second housing 4 arranged in sequence 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 a fastener 2. Both the first housing 3 and the second housing 4 include an inner ring part, an outer ring part, and a connecting part connecting the inner ring part and the outer ring part. The inner cavity is formed between the connecting parts on both axial sides, the inner ring part on the circumferential inner side, and the outer ring part on the circumferential outer side. The inner ring part of the first housing 3 protrudes forward, and the inner ring part of the second housing 4 protrudes backward. Thread structures are provided on the circumferential outer walls of the inner ring parts of the first housing 3 and the second housing 4 to facilitate connection with equipment and tool heads / lenses.

[0027] The chamber is provided with two piezoelectric ceramic components, which are symmetrically arranged. The piezoelectric ceramic 9 is close to the first housing 3, and ceramic insulating sheets 8 are provided between the connecting parts of the piezoelectric ceramic 9 and the first housing 3 and the connecting part of the second housing 4. Both the piezoelectric ceramic 9 and the insulating sheet 8 are annular and have through holes for the fastener 2 to pass through. The fastener 2 in this embodiment is not only used for the assembly of the housing, but also for fixing the piezoelectric ceramic 8 and the insulating sheet 9 to the housing. Among them, the power supply component 10 is fixed to the housing through the first bolt 7, and the charge amplifier 5 is stacked and placed in the housing through the stud 6. There are two piezoelectric ceramics 9 and two charge amplifiers 5, and the piezoelectric ceramics 9 correspond to the charge amplifiers 5 one by one. The piezoelectric ceramics 9 are connected to the charge amplifiers 5 through silver-plated signal lines with a diameter of 0.3 mm (not shown in the figure).

[0028] When a contact force acts on the housing, the piezoelectric ceramic 9 generates a charge signal due to the piezoelectric effect, and this signal is converted into a measurable voltage signal by the charge amplifier. The sensor output interface in this embodiment adopts an XH2.54-5P pluggable interface, and the five wirings are the positive power supply, the ground power supply, the signals of two charge amplifiers, the signal of another charge amplifier, and the signal ground. When the two piezoelectric ceramics 9 are connected to the charge amplifier 5, the wiring method of one piezoelectric ceramic is opposite to that of the other. In this way, when a contact force acts on the sensor, the two charge amplifiers 5 will output two signals with opposite polarities. And the interference such as temperature drift is of the same polarity for the charge amplifier 5. Therefore, the difference between the two signals can cancel the interference such as temperature drift and obtain a smaller contact force sensing threshold.

[0029] As Figure 3 shown, a charge amplification circuit is formed with the LMP7721 operational amplifier as the core. The low-temperature-drift 10 nF chip capacitor C1 and the low-temperature-drift 100 MΩ chip resistor R1 form the feedback loop of the amplification circuit, where the temperature coefficient of the capacitor is lower than 30 ppm / °C and the temperature coefficient of the resistor is lower than 10 ppm / °C. The amplification gain A is approximately

[0030] is the unit of gain (F is the unit of capacitance, farad), which means that the input charge signal is converted into a voltage signal and amplified by 10 9 times. Charge is input from the QIN input stage. R2 is the input stage protection resistor. R1 is used to discharge the charge stabilization system. The voltage signal obtained by charge conversion is output as V out after passing through R3. The positive input stage of the LMP7721 is grounded and connected to the voltage follower formed by the LMP7715 after passing through R5.

[0031] By Figure 4 and Figure 5As shown, the charge amplifier 5 uses a high-precision operational amplifier chip as the core to form an amplification circuit. The high-precision operational amplifier chip uses LMP7721. The LMP7715 precision operational amplifier chip and its peripheral circuit form a protection loop for the charge amplification circuit. R6 and C 10 are the feedback resistor and capacitor of the voltage follower. Its output signal is output to the input stage protection loop GUARD of LMP7721 after passing through R4. The two charge amplifiers are respectively compactly arranged on two PCB boards with an area of about 1.8 cm 2 . The PCB boards are stacked and arranged in the alloy housing to increase the space utilization rate. The PCB board adopts a 4-layer board structure. The components are concentrated on the first layer (at the frontmost axial position), and the filter capacitors (C2~C9) are arranged on the bottom layer.

[0032] The power supply module 10 is composed of a voltage inverter and two linear voltage regulators, and is arranged on a PCB board with an area of 2.8 cm 2 . The power supply module 10 is connected to the charge amplifier 5 through a silver-plated signal wire with a diameter of 0.3 mm. The input voltage of the power supply module is 5~9V DC voltage, and the output ±2.5V constant voltage supplies power to the charge amplifier. As Figure 4 shown, the voltage inverter is composed of the HT7660 chip and its peripheral circuit. After the input power supply V DD passes through the HT7660 chip, it is inverted and stepped down to V out =-V DD voltage output. In addition, a 10 μf tantalum capacitor is connected to both ends of the chip CAP+ and CAP-, and a 10 μf tantalum capacitor is connected to both ends of the chip V OUT and the ground. The LV and VSS pins of the chip are grounded, and the BOOST pin and the OSC pin are left floating.

[0033] Among the two linear voltage regulators, the positive voltage linear voltage regulator is composed of the TPS7A4901 chip and its peripheral circuit, and the negative voltage linear voltage regulator is composed of the TPS7A3001 chip and its peripheral circuit. The input voltage V DD is stepped down to +2.5V by the positive voltage linear voltage regulator, and -V DD is stepped up to -2.5V by the negative voltage linear voltage regulator. The output voltages of TPS7A4901 and TPS7A3001 are configured using feedback resistors, and the configuration schemes are the same. Figure 5 shows the schematic diagram of the feedback resistor configuration of TPS7A4901. The calculation relationship between the output voltage V out and the feedback resistors R1 and R2 is

[0034] Taking R2 = 3.24 KΩ, when V outWhen it is +2.5V, R1 = 3.6KΩ; C IN and C NR / SS and C FF and C OUT are surface mount ceramic capacitors encapsulated as C0603, and their capacitance values are given in the figure.

[0035] To verify the function of the present invention, the sensor of the present invention was tested using the 500mg numerical weight in the M1 weight. During the test, the sensor was vertically placed on the vibration isolation table, and a tray with an outer diameter larger than the middle hole of the sensor was placed on the top of the sensor to place the weight. The sensor was powered by the Zondy Atom numerical control power supply DP100, and the supply voltage was 5V. The NI USB-6210 type acquisition card was used for data acquisition. Figure 6 At about 4.5 s, the weight was placed on the tray. The sensor data is shown as the curve in the figure. Signal1 and Signal2 are the signals output by two charge amplifiers respectively, and their polarities are opposite. It should be noted that there is a drift error of about -50mV in the signal. In addition, there is also obvious superimposed periodic interference noise (the three signal humps shown in the figure, resulting from electromagnetic coupling interference), and the signal at 4.5 s is almost covered. Figure 7 The difference between the two signals is given. It can be seen that the signal noise and drift error are greatly reduced, and the contact signal at 4.5 s is enhanced. Taking the gravitational acceleration as 9.8 mm / s2, the experiment can prove that a through-type contact detection sensor based on piezoelectric ceramics involved in the present invention can effectively sense a contact force as low as 4.9 mN.

[0036] This embodiment has the advantages of improving the detection accuracy, not affecting the normal use of the lens / cutting tool, and being convenient for wire routing.

Claims

1. A central-through contact detection sensor based on piezoelectric ceramics, characterized in that Comprising: A housing having a through hole at the center and a receiving cavity surrounding the circumferential side of the through hole, the through hole being not in communication with the receiving cavity; A piezoelectric ceramic assembly located in the receiving cavity, including a piezoelectric ceramic, which generates a charge signal due to the piezoelectric effect when a contact force is applied to the housing; An insulating assembly disposed between the piezoelectric ceramic and the housing for insulating the two and preventing the loss of the charge signal; A signal processing assembly including at least two charge amplifiers respectively connected to corresponding piezoelectric ceramics, for converting the charge signal generated by the piezoelectric ceramics into a measurable voltage signal, and compensating for signal errors caused by factors such as environmental temperature drift by taking the difference between the signals of the two charge amplifiers; A power supply assembly for providing a working voltage for the piezoelectric ceramic assembly and the signal processing assembly to ensure the normal operation of the sensor.

2. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, wherein: The housing includes a first housing and a second housing arranged in sequence along the axial direction of the through hole. Both the first housing and the second housing include an inner ring portion, 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 portions on both axial sides, the inner ring portion on the circumferential inner side, and the outer ring portion on the circumferential outer side; the piezoelectric ceramic is close to the first housing, and the insulating assembly is provided at least between the connecting portion of the first housing and the piezoelectric ceramic.

3. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1, characterized in that: The chamber is provided with at least two of the piezoelectric ceramic assemblies spaced annularly.

4. The piezoelectric ceramic-based central-through contact detection sensor according to claim 1 or 2 or 3, characterized in that: The piezoelectric ceramic and the insulating sheet are both annular and have through holes. The piezoelectric ceramic and the insulating sheet are fixed to the housing through the fasteners, and the fasteners are fitted at the through holes.

5. The through-type contact detection sensor based on piezoelectric ceramics according to claim 3, wherein: Both the piezoelectric ceramic and the charge amplifier are at least two, and the piezoelectric ceramic and the charge amplifier are in one-to-one correspondence.

6. The in-line contact detection sensor based on piezoelectric ceramics according to claim 1 or 2 or 3, characterized in that: The piezoelectric ceramic is connected to the charge amplifier through a silver-plated signal wire with a diameter of 0.3 mm.

7. The in-line contact detection sensor based on piezoelectric ceramics according to claim 1 or 2 or 3, characterized in that: The charge amplifier uses a high-precision operational amplifier chip as the core to form an amplifier circuit, and is equipped with low-temperature-drift capacitors and resistors to form a feedback loop.

8. The piezoelectric ceramic-based central-through contact detection sensor according to claim 1 or 2 or 3, characterized in that: The power supply assembly includes a voltage inverter and two linear voltage regulators, with an input voltage of 5 - 9V DC voltage and an output of ±2.5V constant stable voltage to supply power to the charge amplifier.

9. The in-line contact detection sensor based on piezoelectric ceramics according to claim 8, wherein: The voltage inverter includes an HT7660 chip and its peripheral circuit. Among the linear voltage regulators, the positive voltage linear voltage regulator includes a TPS7A4901 chip and its peripheral circuit, and the negative voltage linear voltage regulator includes a TPS7A3001 chip and its peripheral circuit.

10. The through-type contact detection sensor based on piezoelectric ceramics according to claim 1 or 2 or 3, characterized in that: The sensor output interface uses an XH2.54 - 5P pluggable interface, and the five wirings are respectively the power supply positive pole, the power supply ground, the charge amplifier signal, the signal of another charge amplifier, and the signal ground.

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