CN101319924A - Embedded Wireless Stress/Strain/Temperature Sensor Test Platform - Google Patents

Abstract

Embedded wireless stress/strain/temperature sensor test platform, including a spherical brittle shell and a rigid shell set in the shell, a spherical joint is hinged on the rigid shell, and a dowel is arranged at the lower end of the spherical joint , the strain gauge is placed at the bottom of the dowel bar and fixed on two linear metal strain bars, a permanent magnet is arranged on the opposite side of the spherical connection in the rigid shell, and an electronic device is arranged on the permanent magnet. A Faraday-piezoelectric energy recovery device is arranged between the strain gauge and the strain gauge. The present invention adopts a completely embedded and wireless method, and has no requirements for route arrangement; the measured stress and strain field is not affected by cables; and the miniaturized force-magnetism-piezoelectric energy device with low energy consumption can reduce the stress caused by traffic or vibration. The mechanical vibration energy is converted into electrical energy of the rechargeable battery to prolong the service life of the system; with MEMS/IT technology and integrated functions, almost no maintenance is required, so the total cost is low.

Description

Embedded Wireless Stress/Strain/Temperature Sensor Test Platform

technical field

The invention relates to equipment for measuring force, stress, torque, work, mechanical power, mechanical efficiency or fluid pressure, in particular to an embedded wireless stress/strain/temperature sensor test platform for fault diagnosis and safety analysis of major facilities.

Background technique

Some experts and scholars at home and abroad use optical fiber technology to measure the stress and strain of some large-scale facilities, such as applying optical fiber technology to performance testing of cable-stayed bridges. Optical fiber technology has a good overall estimation of the equipment, and its sensitivity and signal-to-noise ratio are also high. In particular, it has the advantage of measuring the average stress and average deformation, but it cannot test the relevant dynamic parameters of structural vibration. When applying fiber optic technology to measure the local stress of a facility, it is necessary to tightly integrate the fiber and the surrounding structure. When the structure is more complex (eg with corners smaller than 40°), fiber optic technology shows deficiencies. Optical fiber is a series system. When one of them is damaged, the entire optical fiber will lose its working ability or reduce its reliability. In addition, the optical fiber also needs a light source and needs to be aligned. After minor damage such as vibration, the alignment of the optical fiber is a problem. Optical fibers can be used in new system designs, but most of the existing existing systems are not equipped with optical fibers, so it is impossible to use optical fiber technology for fault diagnosis and safety analysis of these existing devices.

Compared with optical fiber technology, the application of sensors has certain advantages: (1) The mechanical properties of the sensor are very good, the shell strength is high, and the use of the sensor will not damage the structural strength; (2) The sensor is placed at a node and can measure any point Local stress and deformation can also be used in complex structures and special locations, with high reliability; (3) The sensor can be used in existing facilities by drilling holes, pouring cement, etc.; (4) The sensor can measure the dynamics of structural vibration (5) The sensor can be used in post-earthquake detection of large dams, bridges, high-rise dangerous buildings, etc.

Traditional wired sensor technology was once used in the measurement of internal stress and strain of expressway roadbed. With the rapid development of radio frequency (RF) technology, people began to study and pay attention to wireless stress/strain measurement based on RF data transmission technology, which has aroused more and more research and attention. However, at present, this kind of RF module is powered by a battery, and the whole working time generally does not exceed 8 hours. Once placed in the facility, it cannot be reused.

Contents of the invention

The purpose of the present invention is to provide a simple structure, maintenance-free, long-life embedded wireless stress/strain/temperature sensor test platform.

In order to achieve the above object, the technical solution adopted by the present invention is: comprising a spherical brittle shell and a spherical rigid shell arranged in the brittle shell, a spherical joint is hinged in the rigid shell, and a transmission is arranged at the lower end of the spherical joint. The dowel bar, the strain gauge is placed at the bottom of the dowel bar, and is fixed on two linear metal strain bars. A permanent magnet is arranged on the opposite side of the spherical connection in the rigid shell, and an electronic device is arranged on the permanent magnet. A Faraday-piezoelectric energy recovery device connected to the electronic device is arranged between the electronic device and the strain gauge through a spring.

What the permanent magnet of the present invention adopted is that the magnetic field intensity is at least the permanent magnet of 2000 Oersted; Dowel, strain bar and strain gauge form a stress/strain sensor unit; Replace this stress/strain sensor unit, thermometer, hygrometer Or the accelerometer is directly consolidated on the spherical connection to form a temperature sensor unit, a humidity sensor unit and an acceleration sensor unit respectively; the electronic device includes a charging and regulating circuit and a low voltage detection circuit connected to the Faraday-piezoelectric energy recovery device, The charging regulation circuit and the low voltage detection circuit are connected with the energy supply rechargeable battery, and the output of the energy supply rechargeable battery is respectively connected with the strain gauge, the signal conditioner and the microcontroller/transceiver system chip, and the microcontroller/transceiver system The chip includes a data input and output unit and an analog-to-digital converter connected to the signal conditioner to control the signal conditioner. The analog-to-digital converter is also connected to the memory for transmitting data. The memory sends the signal to the transceiver and passes through the The antenna is sent to the outside world; Farah’s first piezoelectric energy recovery device includes a substrate and an array composed of several groups of cantilever beam structure bimorph elements uniformly distributed on the substrate, and a bimorph element is provided at the end of each Mass block; the center of gravity of the rigid shell is at its bottom; the brittle shell is made of ceramic or glass brittle material; a biaxial liquid filling direction sensor is also arranged on the central axis in the rigid shell, and the biaxial liquid filling direction sensor It includes a spherical hollow shell, and more than half of the volume of the conductive liquid is injected into the spherical hollow shell. Two mutually perpendicular intersecting plates are arranged on the spherical hollow shell. The two plates contain sixteen quadrant symmetrical electrodes, each electrode It communicates with other electrodes through a conductive liquid.

Since the structural safety of major facilities generally needs to consider multiple parameters, for its fault diagnosis and safety analysis, it is necessary to establish a platform system to obtain key parameters and dynamic parameters at different locations. In view of the outstanding advantages of sensor applications, the present invention designs an embedded wireless sensor platform system. Compared with the prior art, the sensor system of the present invention has the following advantages: it is fully embedded and wireless, and there is no requirement for routing; the measured stress and strain field is not affected by cables; it uses low-energy miniaturized force- The magnetic-piezoelectric battery charging device can convert the mechanical vibration energy caused by traffic or vibration into the electrical energy of the rechargeable battery to prolong the service life of the system; the use of MEMS/IT technology and integrated functions requires almost no maintenance, so the total cost lower.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the present invention;

Fig. 2 is a system block diagram of the present invention;

3 is a schematic diagram of a bimorph array of the Faraday-piezoelectric energy recovery device 6 of the present invention;

Fig. 4 is a structural schematic diagram of a biaxial liquid filling direction sensor of the present invention;

Fig. 5 is a cross-sectional view of the biaxial liquid filling direction sensor of the present invention.

Detailed ways

Referring to Fig. 1, the present invention includes a spherical brittle shell 9 made of ceramic or glass brittle material and a spherical rigid shell 2 arranged in the brittle shell 9, the rigid shell 2 is strong enough to resist transmission from the ground. mechanical force, and resistant to environmental corrosion, a spherical joint 1 is hinged in the rigid shell 2, a dowel 3 is arranged at the lower end of the spherical joint 1, and a strain gauge 5 is placed at the bottom of the dowel 3, and fixed Junctioned on two linear metal strain bars 4, the spherical joint 1, dowel 3, strain bar 4 and strain gauge together form a sensor, and a magnetic field strength of at least 2000 is provided on the opposite side of the spherical 1 joint in the rigid shell 2. Oster's permanent magnet 7, and electronic device 8 is arranged on permanent magnet 7, is provided with Farah first piezoelectric energy recovery device 6 that is connected with electronic device 8 between electronic device 8 and strain gauge 5, the present invention The center of gravity of the overall structure is at its bottom, so that the rigid shell 2 acts like a tumbler.

Referring to Fig. 2, the electronic device 8 of the present invention includes a charging and regulating circuit and a low-voltage detection circuit connected to the Fara first piezoelectric energy recovery device 6, and the charging regulating circuit and the low-voltage detecting circuit are connected to a rechargeable battery providing energy , the output of the rechargeable battery is connected to the strain gauge 5 (or temperature/humidity/acceleration sensor), the biaxial liquid filling direction sensor, the signal conditioner and the microcontroller/transceiver system chip respectively, and the microcontroller/transceiver system chip Consists of a digital input output (DIO) circuit connected to the signal conditioner to control the signal conditioner and an analog-to-digital converter, which is also connected to a memory for transmitting data, which sends the data to the transceiver And send it to the outside world through the antenna.

First, the energy generated by mechanical vibration is collected by the energy recovery device, and converted into electrical energy through the charging and regulating circuit to supply to the rechargeable battery, and the rechargeable battery provides energy to the sensor. The low-voltage detection circuit can detect the voltage of the working battery. If the voltage drops to a certain level, the backup battery will be turned on and the working battery will start charging. Sensors are generally in a "sleep" state and will be "woke up" to take measurements. Then, through the sensor signal conditioning circuit, the data is fed back to the analog-to-digital converter of the microcontroller, and these data are stored until the data transmission is completed. The microcontroller transmits the data to the outside workstation via the antenna, and then goes back to a "sleep" state. The workstation then transmits these data remotely to the operator via the cellular phone network. All of these circuits are tightly integrated and can withstand bitumen processing temperatures of 200°C, and normally operate in the temperature range of -50°C to 100°C.

Referring to Fig. 3, the Faraday-piezoelectric energy recovery device 6 of the present invention includes a substrate 10 and an array of bimorph elements 11 uniformly distributed on the substrate 10 consisting of several groups of cantilever beam structures, and in each bimorph A mass 12 is provided at the end of the wafer element 11 . The Faraday-piezoelectric energy recovery device 6 converts the energy generated by mechanical vibration into electrical energy to charge the battery, and the battery will provide energy for the low energy consumption sensor. The up and down motion of an electrical conductor in a magnetic field converts mechanical energy into electrical energy, which is how a Faraday device works. Because the output voltage and energy recovery efficiency of the Faraday device are relatively low, usually no more than 25%, the present invention uses MEMS technology to design and manufacture a miniaturized Faraday-piezoelectric energy recovery device, a bimorph made by the LIGA process Chip element array. Each piezoelectric bimorph element is made into a cantilever beam structure, and a mass is placed at the end of the cantilever beam. When the cantilever beam vibrates, an AC voltage is generated between the upper and lower surfaces of the bimorph element. The results show that the piezoelectric device can provide a high output voltage and an electromechanical energy conversion rate as high as 80%. Furthermore, piezoelectric generators can be miniaturized relatively easily using common microfabrication processes.

The brittle shell 9 of the present invention should have the strength to withstand the mixed working pressure in asphalt and clay, but will break into many pieces during the extrusion process of the pavement. In this way, the sensor is gradually embedded in the asphalt or clay during the mixing process, but is automatically oriented vertically by gravity during the paving process. After the shell is broken, the spherical sensor is directly encased in asphalt or clay and remains in a nearly vertical position. However, the sensor may be slightly tilted during the subsequent extrusion process, so the present invention fixes a biaxial liquid angle sensor on the central axis of the spherical sensor system to accurately measure the deflection angle, and transmits the signal by connecting with the electronic device 8 to the outside world.

Referring to Fig. 4, the dual-axis liquid-filled direction sensor includes a spherical hollow shell 13, and more than half of the volume of conductive liquid is injected into the spherical hollow shell 13. The spherical hollow shell 13 is also provided with two mutually perpendicular intersecting plates 14, and the two plates It contains sixteen quarter-part symmetrical electrodes, and each electrode communicates with other electrodes through a conductive liquid.

Figure 5 shows a typical layout of the electrodes. Tables 1 and 2 explain the changes in electrode position and impedance values as the cross plate 14 rotates from 0 to 360 degrees, which demonstrates that this type of sensor design is capable of monitoring tilt in the x-y plane in the range of 0 to 360 degrees.

Table 1: Electrode positions immersed in conductive liquid at different inclination angles

Table 2: Impedance change between electrodes

When the sensor is tilted from 0° to ±10°, a full-bridge circuit is formed between electrodes A/A' and B/B', and the angle sensor has a higher sensitivity of 0.1° at this time. When the sensor is tilted more than 10°, the electrodes form a half-bridge circuit with a reference resistance, resulting in a monitoring sensitivity of 1°. As an example, when the sensor is tilted from 0° to 90°, the impedance between the electrodes C/C' will increase, and the pair of electrodes will act as part of a half-bridge circuit to measure the angle change in this tilt range. Likewise, for tilt angles of 90° to 180°, 180° to 270°, and 270° to 0°, electrodes D/D', B/B' and A/A' will be sequentially used to measure the tilt state. Due to the feature of automatic position adjustment, these sensor units can be deployed in highway bridges and other facilities as part of structural materials during the material mixing stage, without requiring any changes to the original construction process, and without adding additional assembly costs .

Finally, after the sensor units are embedded in the asphalt/soil/concrete structure, the physical coordinates and stress/strain directions of each unit need to be determined in order to accurately map the stress/strain/temperature/humidity information network of the entire facility. There are two ways to determine the physical coordinates of the sensor, one is to use a metal detector to determine the x-y coordinates, and use a sound velocity measuring instrument to determine the z coordinates; the other is to use a high-precision GPS electronic positioning device.

The embedded wireless stress/strain/temperature sensor test platform invented by this patent can perform fault diagnosis and safety analysis on major products and major facilities. The energy recovery device based on MEMS technology can convert mechanical vibration energy into electrical energy and store it in a rechargeable battery, thus ensuring the long-life operation of the embedded sensor. Since the automatic adjustment device of the sensor unit can accurately measure the deflection direction of the sensor axis, the integrated sensor unit can accurately determine different parameters such as local stress/strain/temperature/acceleration/humidity in the facility. Under the power supply of the rechargeable battery, the electronic device can convert various parameters into signals and transmit them to the outside world by the microcontroller/transceiver system chip.

The advantages of the present invention are:

Stability: The sensor is stable in major facility environments and can withstand temperature changes from -50°C to 100°C;

Localized measurements: The measured stress/strain/temperature values are with respect to the material in the very close region around the sensor with a diameter not exceeding 8cm. The precise location of the measurement can be determined by comparing the data information with the sensor layout map;

High sensitivity: the sensitivity of a single sensor will be higher than 0.5kPa, and the sensitivity of the integrated sensor system will be better than 2.5kPa;

Linear response: The sensor uses a micro-processed mechanical device, and its strain degree is designed in a linear range, so that a linear response can be guaranteed;

High sensitivity to the measurement direction: use a specially designed embedded sensor automatic adjustment device to determine the direction of the measurement force;

Insensitive to temperature changes: a temperature sensor is also integrated in the sensor system, and the temperature compensation function in the circuit can ensure accurate measurement when the temperature changes;

Absolute measurement: This sensor system has a long service life and strictly calibrated strain sensor, so that the measurement results of stress/strain/temperature are reliable and accurate;

No impact on the structure under test: the sensor system is small in size, with a diameter of about 5cm, can withstand high temperatures of 200°C in a short period of time, and has an automatic adjustment function; the sensor deployment process is carried out according to the environment of the structure under test and standard procedures;

Does not rely on external energy sources: This sensor system has its own energy device, which can achieve energy self-sufficiency, so it is not affected by environmental energy loss;

Scalability: If a sensor needs to be added somewhere, a hole with a diameter of 5cm should be drilled there, and then filled with the original material. If multiple parameters need to be measured, multiple sensors can be integrated into existing platforms without redesign;

Mass production: due to the use of MEMS technology and off-the-shelf circuit chips, this sensor system can be used for mass production;

Long life: The whole sensor system uses low energy consumption design and miniaturized force-magnetic-piezoelectric battery charging device, which can convert the mechanical vibration energy caused by traffic or vibration into the electrical energy of the rechargeable battery to prolong the service life of the system;

The structural strength is not weakened: the sensor unit housing is made of stainless steel, which will not weaken the strength of the road and bridge facilities.

Claims (8)

1. Embedded wireless stress/strain/temperature sensor test platform is characterized in that it includes a spherical brittle shell (9) and a spherical rigid shell (2) arranged in the brittle shell (9). A spherical joint (1) is hinged in the hard shell (2), and a dowel bar (3) is arranged at the lower end of the spherical joint (1), and the strain gauge (5) is placed at the bottom of the dowel bar (3), and fixed Connected on two linear metal strain bars (4), a permanent magnet (7) is arranged on the opposite side of the connection of the spherical shape (1) in the rigid shell (2), and an electronic device ( 8), a Faraday-piezoelectric energy recovery device (6) connected to the electronic device (8) is provided through a spring between the electronic device (8) and the strain gauge (5). 2. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: said permanent magnet (7) is a permanent magnet with a magnetic field strength of at least 2000 Oersted. 3. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: said dowel bar (3), strain bar (4) and strain gauge (5) form a stress /strain sensor unit; replace this stress/strain sensor unit, and directly consolidate the thermometer, hygrometer or accelerometer on the spherical coupling (1), then respectively form a temperature sensor unit, a humidity sensor unit and an acceleration sensor unit. 4. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: said electronic device (8) includes a charging device connected to a Faraday-piezoelectric energy recovery device (6) And regulating circuit and low-voltage detecting circuit, charge regulating circuit and low-voltage detecting circuit are connected with energy supply rechargeable battery, the output of energy supply rechargeable battery is connected with strain gauge (5), signal conditioner and microcontroller/transmitter respectively The microcontroller/transceiver system chip includes a data input and output unit and an analog-to-digital converter connected to the signal conditioner for controlling the signal conditioner, and the analog-to-digital converter is also connected to a data transmission unit The memory is connected, and the memory sends a signal to the transceiver and through the antenna to the outside world. 5. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: said Faraday-piezoelectric energy recovery device (6) includes a substrate (10) and uniformly distributed on the substrate (10) is an array composed of several groups of bimorph elements (11) with a cantilever beam structure, and a quality block (12) is arranged at the end of each bimorph element (11). 6. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: the center of gravity of the rigid shell (2) is at its bottom. 7. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: said brittle shell (9) is made of ceramic or glass brittle material. 8. The embedded wireless stress/strain/temperature sensor test platform according to claim 1, characterized in that: a biaxial liquid-filled direction sensor is also arranged on the central axis of the rigid shell (2) , the biaxial liquid-filled direction sensor includes a spherical hollow shell (13), and more than half of the volume of conductive liquid is injected into the spherical hollow shell (13), and two mutually perpendicular cross plates are also arranged on the spherical hollow shell (13), Sixteen quadrant symmetrical electrodes are contained in the two plates, and each electrode communicates with other electrodes through a conductive liquid.

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