A monitoring device and system for loose bolts of volute inlet door of hydropower unit

Abstract

The present invention provides a monitoring device and system for bolt loosening of a volute entry door of a hydropower unit, comprising a hexagonal nut sleeve sleeved on the outside of a bolt assembly; a tag antenna is embedded in a groove on the bottom surface of the hexagonal nut sleeve; a three-axis magnetic field sensor is embedded in a groove on the inner wall surface of the hexagonal nut sleeve; a passive RFID sensor chip is embedded in a groove on the inner wall surface of the hexagonal nut sleeve; and the passive RFID sensor chip connects the three-axis magnetic field sensor and the tag antenna. The present invention realizes rapid installation of sensors and passive wireless bolt loosening monitoring without changing the position state of the original bolts and nuts, changing the appearance size of the nuts, and affecting the normal use of the bolts. The material is simple and the cost is lower. At the same time, the RFID technology is used to reduce the communication requirements, and it can be activated by electromagnetic waves to make it work without the need for an additional power supply, so that the sensor is passive and has a wide range of applications, providing a prerequisite for normalized detection of large-scale bolts.

Description

Technical Field

[0001] The invention relates to the technical field of bolt loosening monitoring, and in particular to a device and a system for monitoring the loosening of bolts on a volute inlet door of a hydropower unit. Background Art

[0002] Bolts are widely used because of their direct force transmission, easy disassembly, good economy, and wide application range. Bolt connection is the most widely used connection method in engineering practice, which transmits force between components. Bolts will loosen under the impact of cyclic loads and forced vibration. However, for bolts working in harsh environments, their tightness and fatigue damage are often difficult to judge directly, or their health status is often ignored. In order to avoid the catastrophic consequences of bolt loosening, it is necessary to conduct bolt loosening detection so as to understand the bolt status in time and minimize the occurrence of accidents.

[0003] At present, the detection methods for bolt loosening mainly include vibration-based bolt detection technology, which determines the connection status of the bolt by extracting the changes in the dynamic characteristics of the overall structure such as the characteristic frequency, transfer function, and power spectrum before and after the bolt loosening. However, an assembly structure usually contains a large number of bolt connections, and the loosening of bolts at local positions will not cause changes in the overall dynamic characteristics of the structure, which leads to the inability of vibration-based bolt loosening monitoring technology to make timely judgments on the loosening of bolts at local positions. The bolt loosening detection technology based on guided waves determines the state of the bolt connection by measuring the change in the propagation time of ultrasonic waves in the bolt screw or the change in the energy of the transmitted wave of ultrasonic guided waves at the connection surface of the connected parts. It is an effective non-destructive testing method. However, this method has high requirements for measuring equipment and is difficult to apply on a large scale. In addition, many hydropower generating units still use manual regular sampling to check the tightening status of the bolts. This method has the disadvantages of being time-consuming, inefficient, and expensive. In addition, manual regular inspections cannot guarantee the real-time and synchronization of the detection of the tightness of the bolt connection, which poses a great safety hazard to the safety of the operation of the hydropower generating units.

[0004] How to realize passive wireless bolt loosening failure detection while also achieving rapid installation of the device and bolt loosening monitoring without changing the position status of the original bolts and nuts. To this end, the present invention designs a hydropower unit volute entry door bolt loosening monitoring device and monitoring system. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a device and system for monitoring the loosening of bolts on a volute entry door of a hydropower unit, which can solve the existing problems.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention is realized through the following technical scheme: a device for monitoring the loosening of bolts of a volute entry door of a hydropower unit, comprising a hexagonal nut sleeve sleeved on the outside of a bolt assembly; a tag antenna is embedded in a groove on the bottom surface of the hexagonal nut sleeve; a three-axis magnetic field sensor is embedded in a groove on the inner wall surface of the hexagonal nut sleeve; a passive RFID sensor chip is embedded in the groove on the inner wall surface of the hexagonal nut sleeve; the passive RFID sensor chip is connected to the three-axis magnetic field sensor and the tag antenna, and the passive RFID sensor chip determines the change information of the three-dimensional magnetic field detected by the three-axis magnetic field sensor and transmits it wirelessly through the tag antenna.

[0008] Furthermore, the tag antenna includes a wireless radio frequency identification PCB antenna and a bent symmetrical vibrator; the wireless radio frequency identification PCB antenna is connected to the bent symmetrical vibrator, and the wireless radio frequency identification PCB antenna is connected to the passive RFID sensor chip through the bent symmetrical vibrator; the wireless radio frequency identification PCB antenna adopts a 915MHz flexible RFID wireless radio frequency identification PCB antenna, and the wireless radio frequency identification PCB antenna is provided with two symmetrical ones.

[0009] Furthermore, the three-axis magnetic field sensor includes a single-chip microcomputer and a three-axis magnetic field sensing module. The single-chip microcomputer adopts an MSP430 single-chip microcomputer, and the MSP430 single-chip microcomputer is used to digitally process the sensing information based on the analog signal of the three-axis magnetic field sensing module and transmit it to the passive RFID sensor chip.

[0010] Furthermore, the passive RFID sensor chip adopts Farsens ROCKY100 chip; the passive RFID sensor chip includes an SPI control module, a memory, a processor, a clock, a rectifier and a voltage regulator module and a radio frequency front end; the SPI control module is connected to the single-chip microcomputer, the processor is connected to the SPI control module, the memory, the clock, the rectifier and the voltage regulator module and the radio frequency front end, and the radio frequency front end is connected to the rectifier and the voltage regulator module.

[0011] Furthermore, the bolt assembly includes a bolt fixing nut, the hexagonal nut sleeve is sleeved on the outside of the bolt fixing nut, and the bolt fixing nut is threadedly connected to a screw rod; a bolt is fixed at the bottom end of the screw rod, and a bottom plate is provided at the top of the bolt; a base plate is provided at the top of the bottom plate, and the base plate is fixed to the outside of the bottom end of the bolt fixing nut; a nut cap is provided at the top of the bolt fixing nut; the screw rod passes through the connected bottom plate, and the screw rod is threadedly connected to the nut cap.

[0012] Furthermore, the thickness of the substrate is 1.6 mm, and the substrate is made of FR4 dielectric substrate material. The cross-section of the substrate is hexagonal, and the inner diameter of the substrate is the same as the outer diameter parameter of the bolt fixing nut.

[0013] Furthermore, the hexagonal nut sleeve includes a polyamide fiber hexagonal nut sleeve, and the inner diameter of the hexagonal nut sleeve is the same as the outer diameter parameter of the bolt fixing nut; the cross-section of the hexagonal nut sleeve adopts a regular hexagonal structure, and a wireless radio frequency identification PCB antenna is symmetrically arranged in the bottom end groove of the hexagonal nut sleeve; the wireless radio frequency identification PCB antenna is attached to the substrate.

[0014] A system for monitoring bolt loosening of a volute entry door of a hydropower unit comprises a bolt loosening monitoring device and a reader as described above, wherein the reader is connected to a tag antenna, and the tag antenna is connected to a three-axis magnetic field sensor via a passive RFID sensor chip; the passive RFID sensor chip determines the change information of the three-dimensional magnetic field detected by the three-axis magnetic field sensor and wirelessly transmits it to the reader via the tag antenna.

[0015] Furthermore, the maximum theoretical reading distance between the tag antenna and the reader is 13.26 m.

[0016] Compared with the prior art, the beneficial effects of the present invention include:

[0017] The device of the present invention is quick and convenient to install. It only needs to fix the polyamide fiber hexagonal nut sleeve outside the bolt fixing nut to realize passive bolt loosening monitoring. The sensor can be quickly installed and passive wireless bolt loosening monitoring can be realized without changing the original bolt and nut position status, changing the nut appearance size, and affecting the normal use of the bolt. The material is simple and the cost is lower. At the same time, the RFID technology is used to reduce the communication requirements. It can be activated by electromagnetic waves to make it work without the need for additional power supply, and the sensor is passive. The application range is wide, and it provides a prerequisite for normalized detection of large-scale bolts. The present invention has a simple structure and can adapt to the bolt loosening monitoring device of the volute entry door of the hydropower unit, so as to realize the loosening failure warning and dynamic monitoring of the bolt connection structure of the volute entry door of the hydropower unit; it solves the problems that the traditional bolt loosening detection is difficult to timely and accurately identify and it is difficult to locate the loose position and loose damage of a single bolt.

[0018] The present invention adopts a passive wireless automatic detection method for bolts, which changes the traditional situation that manual regular inspections are required and it is difficult to accurately identify and locate the loose position and damage information of a single bolt. It can realize real-time measurement, improve the detection accuracy, and improve the reliability of the detection results. The application of RFID, the core technology of the intelligent Internet of Things, to bolt loosening monitoring is of great significance to realizing the transformation of bolt loosening detection towards digitalization, automation, networking and intelligence. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them:

[0020] Figure 1 It is a schematic diagram of the overall structure of a device for monitoring the loosening of bolts of a volute inlet door of a hydropower unit according to the present invention;

[0021] Figure 2 It is a structural schematic diagram of a bolt loosening monitoring device applied to a bolt assembly in an implementation case of the present invention;

[0022] Figure 3 This is an overall system block diagram of a bolt loosening monitoring system according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the connection between the passive RFID sensor chip and the three-axis magnetic field sensor circuit in the embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the structure of a tag antenna in an implementation example of the present invention;

[0025] Figure 6 The HFSS simulation result diagram of a 915MHz flexible RFID wireless radio frequency identification PCB antenna is shown as an implementation example of the present invention.

[0026] Explanations in the figure: 1. Bolt; 2. Bottom plate; 3. Base plate; 4. Hexagonal nut sleeve; 5. Bolt fixing nut; 6. Nut cap; 7. Screw; 8. Passive RFID sensor chip; 9. Wireless radio frequency identification PCB antenna; 10. Three-axis magnetic field sensor; 11. Bend-symmetrical vibrator. DETAILED DESCRIPTION

[0027] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0028] The present invention provides a device and system for monitoring the loosening of bolts at a volute entry door of a hydropower unit. The device for monitoring the loosening of bolts at a volute entry door of the present invention is applied to monitoring the loosening of bolts at a volute entry door of a hydropower unit, but is not limited thereto.

[0029] The device for monitoring the loosening of bolts of the spiral casing inlet door of a hydropower unit of the present invention comprises a bolt assembly and a monitoring assembly.

[0030] The bolt assembly includes a screw rod 7, such as Figure 2As shown, the bottom end of the screw rod 7 is fixed with a bolt 1, the top end of the bolt 1 is provided with a bottom plate 2, and the screw rod 7 is connected through the bottom plate 2; the top end of the bottom plate 2 is provided with a base plate 3, and the base plate 3 is fixed to the outside of the bolt fixing nut 5, the inner diameter of the base plate 3 is the same as the outer diameter of the bolt fixing nut 5, and the bolt fixing nut 5 is threadedly connected to the screw rod 7; the top end of the bolt fixing nut 5 is provided with a nut cap 6, and the screw rod 7 is threadedly connected to the nut cap 6.

[0031] Exemplarily, the thickness of the substrate 3 of the present invention is 1.6 mm, and the substrate 3 adopts FR4 dielectric substrate material (FR4 is a common glass fiber reinforced epoxy resin composite material, also known as glass fiber board or glass fiber board; it is one of the most commonly used electronic circuit board (PCB) substrate materials; the name of FR4 substrate is derived from the IPC-4101 standard, where "FR" stands for flame retardant (Flame Retardant), and "4" indicates that it has a higher level of flame retardancy), the cross-section of the substrate 3 is hexagonal, and the inner diameter of the substrate 3 is the same as the outer diameter parameter of the bolt fixing nut 5.

[0032] Monitoring component, the detection component includes a hexagonal nut sleeve 4, a passive RFID sensor chip 8, a tag antenna and a three-axis magnetic field sensor 10; Figure 1 As shown, the tag antenna is embedded in the groove at the bottom end of the hexagonal nut sleeve 4; the three-axis magnetic field sensor 10 is embedded in the groove on the inner wall surface of the hexagonal nut sleeve 4; the passive RFID sensor chip 8 is embedded in the groove on the inner wall surface of the hexagonal nut sleeve 4; the passive RFID sensor chip 8 connects the three-axis magnetic field sensor 10 and the tag antenna, and the passive RFID sensor chip 8 determines the change information of the three-dimensional magnetic field detected by the three-axis magnetic field sensor 10 and transmits it wirelessly through the tag antenna.

[0033] The present invention also provides a monitoring system for the loosening of bolts entering the spiral casing of a hydropower unit. Figure 3 As shown, it includes the bolt loosening monitoring device and the reader as described above, the reader is connected to the tag antenna for two-end remote signal transmission; the tag antenna is connected to the three-axis magnetic field sensor 10 through the passive RFID sensor chip 8; the passive RFID sensor chip 8 determines the change information of the three-dimensional magnetic field detected by the three-axis magnetic field sensor 10 and transmits it to the reader wirelessly through the tag antenna.

[0034] Exemplarily, the hexagonal nut sleeve 4 in the present invention comprises a polyamide fiber hexagonal nut sleeve 4, and the inner diameter of the hexagonal nut sleeve 4 is the same as the outer diameter parameter of the bolt fixing nut 5; the cross-section of the hexagonal nut sleeve 4 adopts a regular hexagonal structure,

[0035] Specifically, the tag antenna includes a wireless radio frequency identification PCB antenna 9 and a bending symmetrical vibrator 11; the wireless radio frequency identification PCB antenna 9 is connected to the bending symmetrical vibrator 11, and the wireless radio frequency identification PCB antenna 9 is connected to the passive RFID sensor chip 8 through the bending symmetrical vibrator 11; the wireless radio frequency identification PCB antenna 9 adopts a 915MHz flexible RFID wireless radio frequency identification PCB antenna 9, and the wireless radio frequency identification PCB antenna 9 is provided with two symmetrical ones. The wireless radio frequency identification PCB antenna 9 is symmetrically arranged in the groove at the bottom end of the hexagonal nut sleeve 4; the wireless radio frequency identification PCB antenna 9 is attached to the substrate 3;

[0036] The three-axis magnetic field sensor 10 is used to simultaneously detect the magnetic field information of the bolt fixing nut 5 along the X, Y and Z axes; the three-axis magnetic field sensor 10 includes a single-chip microcomputer and a three-axis magnetic field sensing module, the single-chip microcomputer adopts an MSP430 single-chip microcomputer, and the MSP430 single-chip microcomputer is used to digitize the sensing information based on the analog signal of the three-axis magnetic field sensing module and transmit it to the passive RFID sensor chip 8 at the same time.

[0037] The passive RFID sensor chip 8 adopts the Farsens ROCKY100 chip, which is a wireless radio frequency energy harvesting device (RF Energy Harvester) chip of Farsens. It is a passive RFID (Radio Frequency Identification) solution that uses radio frequency energy in the environment for power supply without batteries or external power supplies. The ROCKY100 chip has the following characteristics: Energy harvesting: The ROCKY100 chip receives radio frequency energy from the surrounding environment and converts it into the electrical energy required for the chip to operate. Efficient energy harvesting: It uses efficient energy harvesting technology to obtain enough energy from lower radio frequency signals for the chip to work. Multiple frequency band support: The ROCKY100 chip can operate on multiple radio frequency bands to adapt to different environments and radio frequency signal conditions. Simplified design: The chip can be integrated with other components such as sensors, antennas and microcontrollers to realize wireless sensing and data acquisition applications. The passive RFID sensor chip 8 is used for decoding the forward link and modulating the backscatter signal of the backward link; the passive RFID sensor chip 8 includes an SPI control module, a memory, a processor, a clock, a rectifier and a voltage regulator module, and a radio frequency front end; Figure 3As shown, the SPI control module is connected to the single-chip microcomputer, the processor is connected to the SPI control module, the memory, the clock, the rectifier and voltage regulator module and the radio frequency front end, and the radio frequency front end is connected to the rectifier and voltage regulator module; wherein the radio frequency front end is used for UHF RFID (UHF RFID is Ultra-High Frequency Radio-Frequency Identification, which is a wireless radio frequency identification technology that uses radio frequency signals in the ultra-high frequency band for communication and data transmission) energy collection and communication, and the processor adopts a digital processor that complies with the EPCC1G2 / ISO18000-6C standard, and the digital processor is connected to the SPI (Serial Peripheral Interface) control module, and is used to control the SPI bridge through the EPC C1G2 standard memory access command. The connection circuit diagram of the passive RFID sensor, the single-chip microcomputer and the single magnetic field sensor module of the present invention is shown in Figure 4 As shown, the MSP430 microcontroller can control the measurement of the magnetic field, the three-axis magnetic field sensor module is used to provide the real magnetic field measurement value, and the capacitor C1 in the circuit is to support the peak current during the measurement process.

[0038] Figure 5 The schematic diagram of the 915MHz flexible RFID wireless radio frequency identification PCB antenna structure is shown, and the tag antenna parameters are shown in the table:

[0039]

[0040] Figure 6 (a, b, c, d) show the HFSS simulation results of the 915MHz flexible RFID wireless radio frequency identification PCB antenna. Figure 6 It can be seen that when the tag antenna resonates at 915MHz, the return loss reaches -43.99dB. The frequency band where the return loss is below -10dB is 840~970MHz, and the bandwidth can reach 130MHz. The real and imaginary parts of the antenna impedance increase slowly, and the real part does not change much. At 915MHz, the impedance is (46+461j)Ω, and the antenna gain reaches 0.8dBi. According to free space FRISS transmission, the recognition distance of the RFID system can be expressed by the formula (where P1 is the tag's receiving power (minimum power on); P0 is the reader's antenna transmission power; G0 is the reader's transmitting antenna gain; G1 is the tag's receiving antenna gain; R is the distance between the receiving antenna and the transmitting antenna, and δ is the correction factor) is used to estimate the maximum gain of the antenna, 0.8dBi, by substituting it into The maximum theoretical reading distance of the tag antenna is calculated to be about 13.26m.

[0041] When the hydropower unit volute entry door bolt loosening monitoring device of the present invention is in use, when the bolt fixing nut 5 is loosened and displaced, the three-axis magnetic field sensor 10 can simultaneously detect the three-dimensional magnetic field along the X, Y and Z axes, and the magnetic field information detected by the three-axis magnetic field sensor module used to detect the magnetic field information of the bolt fixing nut 5 will also change, and then be detected by the passive RFID sensor chip 8 and transmitted to the reader wirelessly.

[0042] The present invention also provides a method for monitoring the loosening of bolts of a volute inlet door of a hydropower unit, comprising the following steps:

[0043] Step 1: Sleeve the bolt loosening device as described above onto the outer side of the bolt fixing nut;

[0044] Step 2: Detect the three-axis magnetic field of the bolt fixing nut through the three-axis magnetic field sensor module;

[0045] Step 3: The microcontroller digitizes the sensing information based on the analog signal of the three-axis magnetic field sensing module and transmits it to the passive RFID sensor chip;

[0046] Step 4: The passive RFID sensor chip determines whether the bolt is loose based on the detected information by checking whether the magnetic field information changes and transmits the detected information wirelessly to the reader.

[0047] The device of the present invention is quick and convenient to install. It only needs to fix the polyamide fiber hexagonal nut sleeve outside the bolt fixing nut. The RFID wireless radio frequency identification PCB antenna, the passive RFID sensor chip, and the three-axis magnetic field sensor for detecting the magnetic field information of the bolt fixing nut are all embedded in the polyamide fiber hexagonal nut sleeve. The three-axis magnetic field sensor can simultaneously detect the three-dimensional magnetic field along the X, Y and Z axes. When the bolt fixing nut is loosened and displaced, the magnetic field information detected by the three-axis magnetic field sensor will also change, and then it will be detected by the passive RFID sensor chip ROCKY100 and transmitted to the reader by wireless, so as to realize passive bolt loosening monitoring. Without changing the original bolt and nut position state, without changing the nut appearance size, and without affecting the normal use of the bolt, the sensor can be quickly installed and passive wireless bolt loosening monitoring can be realized. The material is simple and the cost is lower. At the same time, the RFID technology reduces the communication requirements, and can be activated by electromagnetic waves to make it work without the need for additional power supply. The sensor is passive and has a wide range of applications, providing a prerequisite for normalized detection of large-scale bolts. The present invention has a simple structure and can adapt to the bolt loosening monitoring device of the volute entry door of the hydropower unit, so as to realize the early warning and dynamic monitoring of the loosening failure of the bolt connection structure of the volute entry door of the hydropower unit. It solves the problems that the traditional bolt loosening detection is difficult to timely and accurately identify and it is difficult to locate the loose position and loose damage of a single bolt.

[0048] The present invention adopts a passive wireless automatic detection method for bolts, which changes the traditional situation that manual regular inspections are required and it is difficult to accurately identify and locate the loose position and damage information of a single bolt. It can realize real-time measurement, improve the detection accuracy, and improve the reliability of the detection results. The application of RFID, the core technology of the intelligent Internet of Things, to bolt loosening monitoring is of great significance to realizing the transformation of bolt loosening detection towards digitalization, automation, networking and intelligence.

[0049] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0050] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "several" is two or more, unless otherwise clearly and specifically defined.

[0052] The technical scope of the present invention is not limited to the contents in the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of ​​the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A device for monitoring the loosening of bolts at the volute inlet door of a hydropower unit, characterized in that: It comprises a hexagonal nut sleeve sleeved on the outside of the bolt assembly; a tag antenna is embedded in a groove on the bottom surface of the hexagonal nut sleeve; a three-axis magnetic field sensor is embedded in a groove on the inner wall surface of the hexagonal nut sleeve; a passive RFID sensor chip is embedded in the groove on the inner wall surface of the hexagonal nut sleeve; the passive RFID sensor chip is connected to the three-axis magnetic field sensor and the tag antenna, and the passive RFID sensor chip determines the change information of the three-dimensional magnetic field detected by the three-axis magnetic field sensor and transmits it wirelessly through the tag antenna; The tag antenna includes a wireless radio frequency identification PCB antenna and a bent symmetrical vibrator; the wireless radio frequency identification PCB antenna is connected to the bent symmetrical vibrator, and the wireless radio frequency identification PCB antenna is connected to a passive RFID sensor chip through the bent symmetrical vibrator; the wireless radio frequency identification PCB antenna adopts a 915MHz flexible RFID wireless radio frequency identification PCB antenna, and the wireless radio frequency identification PCB antenna is provided with two symmetrical ones.

2. A device for monitoring the loosening of bolts at the volute inlet door of a hydropower unit according to claim 1, characterized in that: The three-axis magnetic field sensor includes a single-chip microcomputer and a three-axis magnetic field sensing module. The single-chip microcomputer adopts an MSP430 single-chip microcomputer, and the MSP430 single-chip microcomputer is used to digitally process the sensing information based on the analog signal of the three-axis magnetic field sensing module and transmit it to the passive RFID sensor chip.

3. A device for monitoring the loosening of bolts at the volute inlet door of a hydropower unit according to claim 1, characterized in that: The passive RFID sensor chip adopts Farsens ROCKY100 chip; the passive RFID sensor chip includes an SPI control module, a memory, a processor, a clock, a rectifier and a voltage regulator module and a radio frequency front end; the SPI control module is connected to the single-chip microcomputer, the processor is connected to the SPI control module, the memory, the clock, the rectifier and the voltage regulator module and the radio frequency front end, and the radio frequency front end is connected to the rectifier and the voltage regulator module.

4. A device for monitoring the loosening of bolts at the volute inlet door of a hydropower unit according to claim 1, characterized in that: The bolt assembly includes a bolt fixing nut, the hexagonal nut sleeve is sleeved on the outside of the bolt fixing nut, and the bolt fixing nut is threadedly connected to a screw rod; a bolt is fixed at the bottom end of the screw rod, and a bottom plate is provided at the top of the bolt; a base plate is provided at the top of the bottom plate, and the base plate is fixed to the outside of the bottom end of the bolt fixing nut; a nut cap is provided at the top of the bolt fixing nut; the screw rod passes through the connected bottom plate, and the screw rod is threadedly connected to the nut cap.

5. A device for monitoring the loosening of bolts at the volute inlet door of a hydropower unit according to claim 4, characterized in that: The thickness of the substrate is 1.6 mm, and the substrate adopts FR4 dielectric substrate material. The cross section of the substrate adopts a hexagonal shape, and the inner diameter of the substrate is the same as the outer diameter parameter of the bolt fixing nut.

6. A device for monitoring the loosening of bolts at the volute inlet door of a hydropower unit according to claim 5, characterized in that: The hexagonal nut sleeve comprises a polyamide fiber hexagonal nut sleeve, and the inner diameter of the hexagonal nut sleeve is the same as the outer diameter parameter of the bolt fixing nut; the cross-section of the hexagonal nut sleeve adopts a regular hexagonal structure, and a wireless radio frequency identification PCB antenna is symmetrically arranged in the bottom groove of the hexagonal nut sleeve; the wireless radio frequency identification PCB antenna is attached to the substrate.

7. A system for monitoring the loosening of bolts at the volute inlet door of a hydropower unit, characterized in that: It comprises a bolt loosening monitoring device and a reader as described in any one of claims 1 to 6, wherein the reader is connected to a tag antenna, and the tag antenna is connected to a three-axis magnetic field sensor via a passive RFID sensor chip; the passive RFID sensor chip determines the change information of the three-dimensional magnetic field detected by the three-axis magnetic field sensor and wirelessly transmits it to the reader via the tag antenna.

8. A hydropower unit volute inlet door bolt loosening monitoring system according to claim 7, characterized in that: The maximum theoretical reading distance between the tag antenna and the reader is 13.26m.

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