A micro-bridge circuit adjustable dynamic strain measurement system

Abstract

A kind of micro bridge adjustable dynamic strain measurement system, including bridge circuit, for switching bridge connection mode, by switching bridge, strain is converted into electric signal transmission to signal conditioning circuit, and bridge connection mode is transmitted to display module;Signal conditioning circuit, for processing electric signal, and the signal after processing is transmitted to analog-digital converter;Analog-digital converter for converting the signal after processing into digital signal, and digital signal is transmitted to MCU control module;MCU control module, for transmitting to display module and storage module after processing digital signal;Storage module, for storing the strain measurement data collected by system, and remaining capacity is transmitted to display module;Display module, for displaying received data;Power supply circuit, for powering bridge circuit module, MCU control module, LCD display module and signal conditioning circuit.The present application adopts dial switch to switch bridge connection mode, and it is convenient to apply.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of structural vibration dynamic strain measurement, and particularly relates to a micro-bridge adjustable dynamic strain measurement system. BACKGROUND

[0002] Structural vibration is a common problem in life. We usually evaluate the vibration intensity by measuring the strain of the structure, and then give the strategy to deal with the structural vibration. The bridge mode of the Wheatstone bridge used for strain measurement is divided into single-arm, half-bridge and full-bridge. However, most of the current strain measurement systems usually adopt the way of changing the wiring to switch the bridge, which is very inconvenient in practical application. At the same time, the interference of environmental noise has a great influence on the measurement accuracy of strain. Many strain acquisition devices do not consider eliminating the influence of environmental noise. On the other hand, due to the fact that some structures are in the field high-altitude environment, it is inconvenient for the inspection personnel to carry and install the large-size measurement device, and it is inconvenient to frequently replace the battery or charge the measurement device. SUMMARY

[0003] In order to solve the problem that the current strain measurement system usually adopts the way of changing the wiring to switch the bridge, which is very inconvenient in practical application, and also does not consider eliminating the influence of environmental noise, and on the other hand, the current strain measurement system is large in size, and it is inconvenient for the inspection personnel to carry and install, the present application provides a micro-bridge adjustable dynamic strain measurement system, which comprises an MCU control module, a bridge circuit, a signal conditioning circuit, an analog-to-digital converter, a display module, a storage module and a power supply circuit.

[0004] The bridge circuit is used for switching the bridge connection mode, and converts the strain into the change of the resistance value of the strain gauge by the switched bridge, and then converts the change of the resistance value of the strain gauge into an electric signal and transmits the electric signal to the signal conditioning circuit.

[0005] The signal conditioning circuit is used for processing the electric signal and transmitting the processed electric signal to the analog-to-digital converter.

[0006] The analog-to-digital converter is used for converting the processed signal into a digital signal and transmitting the digital signal to the MCU control module.

[0007] The MCU control module is used for processing the digital signal and transmitting the processed digital signal to the display module and the storage module.

[0008] The display module is used for displaying the data transmitted by the MCU control module, the bridge connection mode and the remaining capacity of the storage module.

[0009] The storage module is used for storing the strain measurement data collected by the system.

[0010] The power supply circuit is used for converting the voltage of the lithium ion battery into voltages of different levels and supplying power for the bridge circuit module, the MCU control module, the display module and the signal conditioning circuit.

[0011] Optionally, the MCU control module comprises a master control chip and a minimum system peripheral circuit.

[0012] The master control chip is used for generating a control signal and processing interrupt signals in real time.

[0013] The minimum system peripheral circuit is used for providing a unified clock beat for the system and restoring the system to a starting state when a set restart condition is met.

[0014] Optionally, the minimum system peripheral circuit comprises a clock circuit, a reset circuit and an interrupt control circuit.

[0015] The clock circuit is used for providing a unified clock beat for the system.

[0016] The reset circuit is used for restoring the system to a starting state when necessary.

[0017] The interrupt control circuit is used for processing interrupt signals in real time.

[0018] Optionally, the bridge circuit comprises two dial switches, three resistors, a capacitor and a Wheatstone bridge.

[0019] Two of the three resistors are connected in series and connected between the first pin and the second pin of the Wheatstone bridge.

[0020] One of the two dial switches is connected between the two resistors at one end and connected to the fourth pin of the Wheatstone bridge at the other end.

[0021] The third of the three resistors is connected in series with the other dial switch and connected between the first pin and the third pin of the Wheatstone bridge.

[0022] The first pin of the Wheatstone bridge is connected to the positive pole of the power supply, and the second pin of the Wheatstone bridge is connected to the negative pole of the power supply.

[0023] The capacitor is connected to the first pin of the Wheatstone bridge at one end and grounded at the other end.

[0024] Optionally, the signal conditioning circuit comprises an amplification circuit, a filter circuit and a clamping circuit connected in sequence.

[0025] The amplification circuit is used for amplifying the voltage signal output by the bridge.

[0026] The filter circuit is configured to filter the voltage signal amplified by the amplifier circuit.

[0027] The clamping circuit is configured to limit the voltage signal filtered by the filter circuit within a set voltage range.

[0028] Optionally, the power supply circuit comprises a charge-discharge management circuit and a power supply voltage circuit.

[0029] The charge-discharge management circuit is configured to identify a system power supply amplitude, generate a corresponding short rectangular wave, and drive a subsequent circuit to output power.

[0030] The power supply voltage circuit is configured to supply power to the bridge circuit, the signal conditioning circuit, the MCU control module, and the display module.

[0031] Optionally, the power supply voltage circuit comprises a bridge excitation voltage, a PGIA power supply voltage, and a reference voltage.

[0032] The bridge excitation voltage is configured to supply power to the bridge circuit module.

[0033] The PGIA power supply voltage is configured to supply power to the amplifier circuit.

[0034] The reference voltage is configured to lift the negative voltage signal to be collected, so that the signal enters the voltage range of an analog-to-digital converter.

[0035] Optionally, the system adopts a double-layer circuit board.

[0036] The MCU control module and the display module are located on one of the circuit boards, and the bridge circuit, the signal conditioning circuit, and the power supply circuit are located on the other circuit board.

[0037] Optionally, the display module comprises an LCD display screen or a liquid crystal display screen.

[0038] This invention provides a miniature bridge-adjustable dynamic strain measurement system, comprising an MCU control module, a bridge circuit, a signal conditioning circuit, a display module, a storage module, and a power supply circuit. The bridge circuit switches the bridge connection mode, converting the strain into a change in strain gauge resistance, which is then converted into an electrical signal and transmitted to the signal conditioning circuit. The signal conditioning circuit processes the electrical signal and transmits it to an analog-to-digital converter (ADC). The ADC converts the processed signal into a digital signal and transmits it to the MCU control module. The MCU control module receives the digital signal, processes it, and transmits it to the display and storage modules. The display module shows the data transmitted by the MCU control module, the bridge connection mode, and the remaining capacity of the storage module. The storage module stores the strain measurement data acquired by the system. The power supply circuit converts the lithium-ion battery voltage into various voltage levels and supplies power to the bridge circuit module, MCU control module, display module, and signal conditioning circuit. This invention uses a bridge circuit to switch the bridge connection mode, facilitating practical applications. Compared to existing technologies that use different wiring methods to switch bridge circuits, this approach is safer and more practical.

[0039] This invention employs a double-layer circuit board design to improve system space utilization. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the bridge circuit module of the present invention;

[0041] Figure 2 This is a block diagram of the signal conditioning circuit structure of the present invention;

[0042] Figure 3 This is a schematic diagram of the power supply circuit structure of the present invention;

[0043] Figure 4 This is a hardware design diagram of the micro-sized bridge adjustable dynamic strain measurement system of the present invention. Detailed Implementation

[0044] The present invention proposes a miniature adjustable bridge dynamic strain measurement system, which adopts a simple method that allows free switching between single-arm, half-bridge and full-bridge modes via a DIP switch, achieving small size, low power consumption, filtering capability and convenient switching of bridge connection modes.

[0045] Example 1:

[0046] A miniature adjustable dynamic strain measurement system for bridges, such as Figure 4 As shown, it includes:

[0047] MCU control module, bridge circuit, signal conditioning circuit, analog-to-digital converter, display module, storage module and power supply circuit;

[0048] The bridge circuit module is used for switching bridge connection mode, converting strain into the change of strain gauge resistance value by the switched bridge, and then converting the change of strain gauge resistance value into an electrical signal and transmitting the electrical signal to the signal conditioning circuit.

[0049] The signal conditioning circuit is used for processing the electrical signal and transmitting the processed electrical signal to the MCU control module.

[0050] The analog-to-digital converter is used for converting the processed signal into a digital signal and transmitting the digital signal to the MCU control module.

[0051] The MCU control module is used for processing the digital signal and transmitting the processed digital signal to the display module.

[0052] The storage module is used for storing strain measurement data and transmitting the remaining capacity to the display module.

[0053] The display module is used for displaying the data transmitted by the MCU control module.

[0054] The power supply circuit is used for converting the voltage of a lithium ion battery into voltages of various levels and supplying power to the bridge circuit, the MCU control module, the display module and the signal conditioning circuit.

[0055] The following will be described in detail:

[0056] The micro-bridge adjustable dynamic micro-strain measurement system disclosed by the application is composed of hardware and software.

[0057] The hardware part is designed by double-layer circuit boards, the MCU control module, the display module, the storage module and the like are placed on one 36mm*63mm board, the bridge circuit, the signal conditioning circuit, the power supply circuit and the like are placed on another board of the same size, and the two boards are overlapped and fixed, so that the space utilization of the system is improved, the space utilization of the system is improved, and the system occupies a smaller space.

[0058] The MCU control module is the core part of the embedded system, and is mainly used for managing data and generating control signals; the MCU control module is mainly composed of a main control chip and a minimum system peripheral circuit.

[0059] The main control chip selects the STM32L431 chip developed by ST company.

[0060] The minimum system peripheral circuit includes clock circuit, reset circuit and interrupt control circuit, etc. The clock circuit provides unified clock beat for the whole system; the reset circuit can make the system return to the initial state when necessary; the interrupt control circuit can process various interrupt signals in real time to improve the working efficiency of the MCU.

[0061] The software development is based on Keil5 MDK-ARM development environment, and C language is used on the basis of STM32 library functions. The software part mainly includes data acquisition, data processing and data storage functions, and the function implementation is as described above. The data acquisition is mainly to collect strain data at a set sampling frequency, sampling interval and sampling time. The data processing is to use the FIR digital filter to filter the collected strain data, to eliminate the interference of environmental noise as much as possible, to reduce the measurement error, and to perform data operation according to the related theoretical formula of strain. The data storage part uses the FATFS file management system to store the collected strain data in a 128G memory card.

[0062] The software development of the system is based on Keil5 MDK-ARM development environment, and C language is used on the basis of STM32 library functions.

[0063] The bridge circuit is used to convert the resistance change of the resistance strain gauge into voltage output for subsequent data acquisition; the bridge circuit module uses a code switch to switch the bridge connection mode, and the staff can manually adjust the opening and closing of the code switch (J11, J12) to select single-arm, half-bridge and full-bridge. The following figure is a schematic diagram of the bridge circuit switching.

[0064] The bridge circuit switching bridge mode is as shown in Figure 1 When the single-arm bridge mode is used, the staff adjusts the code switch to close J11 and J12, and connects a single strain gauge to the 2 and 3 pins of P11; when the half-bridge mode is used, the staff adjusts the code switch to connect two strain gauges to the 1 and 3 pins and the 2 and 3 pins of P11, and disconnects J11 and closes J12; when the full-bridge mode is used, the staff directly connects four strain gauges to the circuit, and disconnects J11 and J12.

[0065] The signal conditioning circuit mainly amplifies and filters the analog voltage signal, so that it is suitable for the input of ADC; the signal conditioning circuit mainly comprises an amplification circuit, a filter circuit and a clamping circuit, etc. The amplification circuit of the application is composed of a program-controlled instrument amplifier LTC6915, which is mainly used to amplify the voltage signal output by the bridge, so as to meet the voltage range entering the ADC. The filter circuit adopts a first-order RC low-pass filter with a cutoff frequency of 150 Hz, which can filter the voltage signal output by the amplification circuit and reduce the influence of environmental noise; the clamping circuit can limit the filtered voltage signal between 0-3V, so as to avoid damaging the ADC. The structural block diagram of the signal conditioning circuit is shown in Figure 2 .

[0066] As shown in Figure 3 , the power supply circuit converts the voltage of the lithium battery into the power supply voltage required by each chip; the power supply circuit comprises a charge-discharge management circuit and a power supply voltage circuit. The charge-discharge management circuit mainly manages the charging and discharging and protects the battery, and the power supply voltage circuit mainly provides each voltage required by the system.

[0067] The application can be powered by a battery, and the lithium battery is used as the power supply for the whole system; the lithium battery charge-discharge management circuit adopts an ETA9741 chip, which manages the charging and discharging of the lithium battery and outputs +5V voltage; it is mainly responsible for identifying the system power supply amplitude, generating a corresponding short square wave, and driving the power output of the subsequent circuit. The battery protection circuit adopts an XB4908 chip, which has all the protection functions required in battery applications, including overcharge, overcurrent, overdischarge and load short circuit protection, etc.

[0068] The ADP5071 chip converts the +5V voltage generated by the ETA9741, and the generated +5V voltage is of poor quality, so it needs to be converted into two voltage outputs of +-6V first; the first ADP7142 chip reduces +6V to +5V; the second ADP7142 reduces +5V to +3V; ADP7182 reduces -6V to -3V; the REF2030 chip generates a reference voltage of +5V.

[0069] The power supply voltage circuit mainly comprises a bridge excitation voltage, a PGIA power supply voltage and a reference voltage. The bridge excitation voltage (+5V) is mainly used to supply the bridge circuit; the PGIA power supply voltage (+-3V) is mainly used to supply the dual power supply of the programmable gain instrument amplifier; the reference voltage (+1.5V) is mainly used to lift the negative voltage signal to be collected, so as to meet the voltage range (0-3V) entering the ADC. The bridge excitation voltage and the PGIA dual power supply voltage are obtained by different versions of ADP7182 and ADP7142 respectively, and the reference voltage is obtained by the REF2030 chip. The schematic diagram of the power supply circuit is as followsFigure 3 as shown.

[0070] The storage module is used for storing strain measurement data and transmitting the remaining capacity to the display module; the storage module adopts an SD card, and can also adopt a memory, which is introduced by taking the SD card as an example.

[0071] The display module is used for displaying some necessary information, such as strain value, bridge connection mode, SD card remaining capacity and the like, so that the working personnel can clearly know the working state of the system; the SD card is used for data storage of the system, so as to be viewed by the working personnel subsequently.

[0072] The display module can adopt an LCD display screen, a liquid crystal display screen and the like, and the embodiment is introduced by taking the LCD display screen as an example.

[0073] Embodiment 2

[0074] The overall design of the hardware part of the micro-bridge adjustable dynamic micro-strain measurement system involved in the patent is shown in Figure 4 . Among them, the display module adopts an LCD display screen, and the storage module adopts an SD card.

[0075] The strain gauge adopts a standard 120-ohm strain gauge, which is used for measuring the dynamic strain of the structure vibration. The Wheatstone bridge circuit can be freely switched among single-arm, half-bridge and full-bridge by adjusting the code switch.

[0076] The signal conditioning circuit mainly amplifies, filters and lifts the weak voltage signal output by the bridge circuit to the signal range meeting the input of the analog-to-digital converter (referred to as ADC).

[0077] The MCU mainly controls the peripherals such as ADC, LCD and SD card and performs operation and processing of the strain value.

[0078] After the system is powered on, the MCU performs device initialization, including peripheral initialization, clock initialization and the like. Then the bridge mode is selected and the strain is zeroed, and after zeroing, the strain collection mode is entered. The STM32 controls the ADC to collect data according to the sampling frequency, sampling interval and sampling time. When the data collection is completed, the DMA directly performs data transmission, the MCU processes and calculates the collected voltage data, and finally the strain measurement result is displayed on the LCD display screen, and the strain measurement data is stored in the SD card.

[0079] The operation part of the system is concentrated on the side of the system, and only the code switch and the key need to be operated.

[0080] The 1st and 2nd switches of the dial switch are bridge setting switches of channel 1, the 3rd and 4th switches are bridge setting switches of channel 2, and the 5th switch is a power switch. When the single-arm measurement mode is selected, the 1st, 2nd, 3rd and 4th switches need to be opened; when the half-bridge measurement mode is selected, the 2nd and 3rd switches are opened and the 1st and 4th switches are closed; and when the full-bridge measurement mode is selected, the 1st, 2nd, 3rd and 4th switches are all closed.

[0081] The zero setting button has two functions: one is short pressing, which selects the single-arm, half-bridge and full-bridge measurement modes; and the other is long pressing, which performs strain zero setting.

[0082] The operation process of the system is as follows: after the system is powered on and preheated, the strain gauges are connected to the system interface through the wiring terminals in the corresponding connection mode. Then the bridge measurement circuit of the hardware is set according to the established method through the dial switch, and the measurement mode of the system needs to be switched to the corresponding bridge mode through the button. When preparing to start measurement, the strain needs to be zeroed by long pressing the zero setting button first. After the zero setting is completed, the system enters the normal working mode. In the measurement process, the time, strain value, SD card remaining capacity and other related information can be viewed on the LCD display screen, and the historical measurement data can be viewed in the SD card.

[0083] Embodiment 3

[0084] The micro small bridge adjustable dynamic micro strain measurement system of the application is used to measure the strain of a cantilever beam when it is bent.

[0085] First, the strain gauges are pasted on the cantilever beam of the vibration test bench at room temperature, and then the strain gauges are connected to the system interface. After the device initialization is completed and the strain is zeroed, the strain of the cantilever beam is measured. A concentrated load is applied to the free end of the cantilever beam to bend it to a specified position, and the data measured by the system and the standard strain tester are recorded.

[0086] The free end of the cantilever beam is bent to three different positions according to the above measurement method using the single-arm, half-bridge and full-bridge connection modes respectively, and the measurement results are shown in Table 1.

[0087] Table 1: Actual measurement data results

[0088]

[0089] Those skilled in the art will appreciate that embodiments of the application can be provided as methods, systems, or computer program products. Accordingly, the application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the application can be embodied in the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage media, etc.) having computer usable program code embodied therein.

[0090] The present application is described in reference to the flowchart and / or block diagrams of the methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more flowcharts and / or blocks Figure 1 means for carrying out the function specified by the flowchart block or blocks.

[0091] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart and / or block diagram block or blocks. Figure 1 one or more flowcharts and / or blocks Figure 1 means for carrying out the function specified by the flowchart block or blocks.

[0092] The computer program instructions can also be loaded into a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart and / or block diagram block or blocks. Figure 1 one or more flowcharts and / or blocks Figure 1 means for carrying out the function specified by the flowchart block or blocks.

[0093] The above merely provides an embodiment of the present application, but is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims

1. A micro-bridge circuit tunable dynamic strain measurement system, characterized in that, The system comprises an MCU control module, a bridge circuit, a signal conditioning circuit, an analog-to-digital converter, a display module, a storage module and a power supply circuit. The bridge circuit is used for switching the bridge connection mode, converting the strain into the resistance change of the strain gauge by the switched bridge, converting the resistance change of the strain gauge into an electric signal and transmitting the electric signal to the signal conditioning circuit, and transmitting the bridge connection mode to the display module. The signal conditioning circuit is used for processing the electric signal and transmitting the processed electric signal to the analog-to-digital converter. The analog-to-digital converter is used for converting the processed electric signal into a digital signal and transmitting the digital signal to the MCU control module. The MCU control module is used for processing the digital signal and transmitting the processed digital signal to the display module and the storage module. The storage module is used for storing the strain measurement data and transmitting the remaining capacity to the display module. The display module is used for displaying the received data. The power supply circuit is used for supplying power to the bridge circuit, the MCU control module, the display module and the signal conditioning circuit. The system adopts double-layer circuit boards. The MCU control module and the display module are located on one of the circuit boards, and the bridge circuit, the signal conditioning circuit and the power supply circuit are located on the other circuit board. The MCU control module comprises a master control chip and a minimum system peripheral circuit.

2. The system of claim 1, wherein, The master control chip is used for generating a control signal and processing an interrupt signal in real time. The minimum system peripheral circuit is used for providing a unified clock beat for the system and restoring the system to the initial state when a set restart condition is met. The minimum system peripheral circuit comprises a clock circuit, a reset circuit and an interrupt control circuit.

3. The system of claim 2, wherein, The clock circuit is used for providing a unified clock beat for the system. The reset circuit is used for restoring the system to the initial state when necessary. The interrupt control circuit is used for processing various interrupt signals in real time. The bridge circuit comprises two dial switches, three resistors and a Wheatstone bridge.

4. The system of claim 1, wherein, Two of the three resistors are connected in series and connected between the first pin and the second pin of the Wheatstone bridge. One of the two dial switches is connected between the two resistors at one end and connected to the fourth pin of the Wheatstone bridge at the other end. The third resistor of the three resistors is connected in series with the other dial switch and connected between the first pin and the third pin of the Wheatstone bridge. The first pin of the Wheatstone bridge is connected to the positive electrode of the power supply, and the second pin of the Wheatstone bridge is connected to the negative electrode of the power supply. The bridge circuit further comprises a capacitor.

5. The system of claim 4, wherein, One end of the capacitor is connected to the first pin of the Wheatstone bridge, and the other end is grounded. The signal conditioning circuit comprises an amplification circuit, a filter circuit and a clamping circuit connected in sequence.

6. The system of claim 1, wherein, The amplification circuit is used for amplifying the voltage signal output by the bridge. The filter circuit is used for filtering the voltage signal amplified by the amplification circuit. The clamping circuit is used for limiting the voltage signal filtered by the filter circuit within a set voltage range. The power supply circuit comprises a charge-discharge management circuit and a power supply voltage circuit.

7. The system of claim 6, wherein, ​ The charge and discharge management circuit is used for identifying the system power supply amplitude, generating a corresponding short rectangular wave, and driving the power output of the subsequent circuit. The power supply voltage circuit is used for supplying power for the bridge circuit, the signal conditioning circuit, the MCU control module and the display module.

8. The system of claim 7, wherein, The power supply voltage circuit comprises a bridge excitation voltage, a PGIA power supply voltage and a reference voltage. The bridge excitation voltage is used for supplying power for the bridge circuit. The PGIA power supply voltage is used for supplying power for the amplification circuit. The reference voltage is used for lifting the negative voltage signal to be collected, so that the signal enters the voltage range of the analog-to-digital converter.

9. The system of claim 1, wherein, The display module comprises an LCD display screen.

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