Piezoelectric ultrasonic guided wave monitoring node and wireless control method thereof

Abstract

The invention discloses a piezoelectric type ultrasonic guided wave monitoring node and a wireless control method thereof, and relates to the field of ultrasonic guided wave monitoring. The node has the functions of ultrasonic excitation acquisition, wireless communication and low-power-consumption control, can be used as an independent monitoring unit to operate, and can switch the state under the unified instruction scheduling of an upper computer. According to the method, the upper computer generates and issues a scheduling instruction according to a monitoring requirement, and the scheduling instruction is used for defining a working mode and a data uploading time slot of each node. And the monitoring nodes enter an excitation, acquisition or self-excitation and self-receiving mode at the same time by taking a function control instruction issued by the upper computer as a global time reference. And after the acquisition is completed, the acquisition end node configures a timer according to a corresponding delay control byte to generate data transmission time slots which do not conflict with each other, and orderly transmits the data to an upper computer through a wireless channel in the independent time slots. According to the invention, synchronous control of a plurality of independent monitoring nodes is realized, expandability of node monitoring and reliability of data transmission can be improved, and the method is suitable for large-scale equipment based on ultrasonic guided waves.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic guided wave structure health monitoring technology, specifically to a piezoelectric ultrasonic guided wave monitoring node and a wireless control method for multiple nodes. Background Technology

[0002] During service, large structural equipment (such as storage tanks, long-distance pipelines, and pressure vessels) are prone to cracking, corrosion, or fatigue damage due to prolonged exposure to complex conditions such as high temperature, high pressure, and corrosion. To ensure the long-term safe operation of these large structural components, an effective damage identification method is needed. Traditional ultrasonic testing methods are mostly single-point detection, which, while able to acquire damage information within a certain range, have limited coverage and are deficient in terms of defect omissions, detection efficiency, and real-time performance. Some detection methods require frequent use of coupling agents and manual intervention, which is not conducive to large-area, long-term monitoring. Wireless ultrasonic guided wave monitoring technology has attracted much attention in structural health monitoring due to its wide propagation distance, high degree of automation, and no wiring required. Existing wireless ultrasonic guided wave monitoring systems mostly operate independently with single nodes, making it difficult to synchronize excitation and acquisition between nodes. A method to achieve multi-node collaborative operation is lacking to meet the needs of large-area, distributed structural health monitoring. Therefore, there is an urgent need for ultrasonic guided wave monitoring equipment and a corresponding wireless control method to achieve collaborative monitoring of multiple nodes, improving the coverage and efficiency of structural health monitoring. Summary of the Invention

[0003] Purpose of the invention

[0004] The purpose of this invention is to provide an ultrasonic guided wave monitoring node and a matching multi-node wireless control method, which can realize the collaborative monitoring of multiple nodes and meet the structural health monitoring needs of large structures during service.

[0005] To achieve the above objectives, the present invention mainly includes the following aspects:

[0006] (I) Functional Design of Monitoring Nodes:

[0007] A single monitoring node achieves high integration within a PCB size of only 60mm × 55mm. It features ultrasonic excitation, signal acquisition, LoRa wireless communication, and low-power management, and is equipped with a ZYNQ chip to drive and control each functional module. Each node can operate as an independent monitoring unit.

[0008] 1. Ultrasonic Excitation Circuit Design: The ultrasonic excitation circuit consists of a high-speed dual-channel MOSFET driver TC4428 and an N / P-channel enhancement-mode dual-channel MOSFET transistor TC6320. The ZYNQ chip outputs two inverse level signals with the same frequency as the center frequency of the piezoelectric ceramic. These level signals are converted into bipolar pulse signals by the driver TC4428 chip. The TC6320 chip amplifies the bipolar pulses under the ±100V voltage provided by the boost module, outputting a high-voltage pulse signal with a peak-to-peak value of 200V.

[0009] 2. Ultrasonic Acquisition Circuit Design: Ultrasonic guided wave monitoring often uses low-frequency excitation of tens to hundreds of kHz. According to the sampling theorem, the sampling rate needs to be higher than twice the highest frequency of the signal; in engineering applications, it is usually ten times. Therefore, this design selects the AD9266 chip, which can achieve a maximum sampling rate of 65 MSPS. Since the chip requires positive input voltages and has a relatively small input range (1V to 3V), a potential shift and attenuation module is added to the circuit to extend the input range to ±5V in order to acquire a wider range of data. Simultaneously, a diode limiting protection circuit is used to prevent high-voltage excitation pulses from the front-end excitation module from damaging the receiving module.

[0010] 3. Low-Power Control Circuit Design: This power management unit is based on the STM32L051C8T6 chip, combining MOSFETs and relays to achieve periodic short-term operation and long-term standby modes. The STM32 chip uses an RTC timed wake-up mode. When the chip wakes up, it drives the MOSFET to open the relay, providing short-term power to the back-end circuitry. In non-operating mode, the STM32 chip enters a low-power sleep mode, and the MOSFETs and relays cut off the power supply. This method achieves standby power consumption as low as 1.5mW, effectively reducing node energy consumption.

[0011] (II) Multi-node control method:

[0012] With the support of the aforementioned monitoring node functions, this invention proposes a multi-node control method. The core control logic is written in Verilog and implemented on the ZYNQ platform. The ZYNQ chip parses instructions issued by the host computer to achieve unified control over the excitation, acquisition, and data transmission states of each monitoring node. The specific operation steps of this method are as follows:

[0013] 1. The host computer first generates a complete scheduling instruction based on the monitoring requirements, and sends the instruction to each node through the LoRa broadcast mode. The instruction includes configuration information such as check bit, working mode and data upload time slot, so as to realize unified scheduling of multiple nodes.

[0014] 2. After receiving the instruction sent by the host computer, each monitoring node will enter the working mode corresponding to the instruction (excitation, acquisition, standby).

[0015] 3. After each acquisition node completes the acquisition of a fixed amount of data, it will transmit the data in the order of the time slots allocated by the host computer using the Time Division Multiple Access (TDMA) method to avoid channel conflicts caused by multiple nodes uploading data at the same time, which would result in data chaos.

[0016] 4. After receiving the data transmitted from each node, the host computer performs preprocessing operations on the collected signals (including noise reduction, filtering, envelope extraction, etc.) and combines them with defect identification algorithms to perform visual monitoring of defects in the tested object.

[0017] The beneficial effects of this invention are as follows:

[0018] A piezoelectric ultrasonic guided wave monitoring node and its supporting multi-node wireless control method are proposed. Through centralized scheduling by a host computer, multiple wireless monitoring nodes can operate collaboratively, synchronously performing guided wave excitation and signal acquisition, ensuring the timing consistency of the guided wave signals. During monitoring, the excitation and acquisition ends can be flexibly specified, supporting the expansion of the number of nodes, thereby improving the monitoring range and efficiency. Simultaneously, a time-division multiple access (TDMA) scheduling strategy is introduced during data upload, allocating independent transmission time slots to each node, effectively avoiding channel conflicts and data corruption. Attached Figure Description

[0019] Figure 1 This is the working framework for a single node in this invention.

[0020] Figure 2 This is a schematic diagram of the node structure in this invention.

[0021] Figure 3 The multi-node control program design flow of this invention

[0022] Figure 4 This is a schematic diagram of the time-division multiple access mechanism for multi-node data transmission in this invention.

[0023] Figure 5 This is a schematic diagram of the overall structure of the wireless ultrasonic guided wave multi-node monitoring system of the present invention.

[0024] Figure 6 This is a schematic diagram of the multi-node monitoring process of the present invention.

[0025] Figure 7 This invention provides an example of multi-node application and signal acquisition. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The present invention will be further described below with reference to the accompanying drawings and the above embodiments. The specific implementation examples provided below are descriptive only and not limiting, and should not be used to limit the scope of protection of the present invention.

[0027] This invention is built upon a highly integrated monitoring node. Figure 1 This demonstrates the working framework of a single monitoring node and the relationships between its functional modules. The node integrates piezoelectric ceramics, an excitation module, a signal conditioning circuit, an analog-to-digital converter (ADC), a low-power control module, a wireless communication module (LoRa), and a lithium battery power supply module. Its workflow is as follows: the piezoelectric ceramics generate guided wave signals under the drive of bipolar high-voltage pulses output from the excitation module. The echo signal is processed by the conditioning circuit and then input to the ADC chip for analog-to-digital conversion. The signal is then transmitted to the ZYNQ main control circuit for buffering. The LoRa module sends the buffered data from the ZYNQ to the host computer. Finally, the node enters standby mode, completing a full single-node monitoring cycle. All these functions are ultimately integrated into a 60mm × 55mm PCB in hardware circuitry. Figure 2 As shown, the layout structure of the battery, piezoelectric ceramics, and various functional modules is illustrated, demonstrating the miniaturization and high integration of the nodes in this invention.

[0028] Based on single-node hardware, this invention further proposes a multi-node cooperative control method. Figure 3 The control program written in the ZYNQ chip and its operation flow are demonstrated (taking three nodes as an example). After receiving the scheduling instruction from the host computer, the node first verifies the frame header and frame tail to confirm the validity of the instruction. Then, it parses the function control bytes and delay control bytes (X and Y in the figure do not refer to any specific fixed byte, but are used to represent representative control fields in the instruction frame), automatically configuring the node's working mode (excitation, acquisition, or standby) and data upload time slot. When the delay field of the acquisition node is non-zero, the node starts a timer corresponding to the delay field. After counting is complete, data is uploaded. Through this mechanism, this invention realizes time-division multiple access scheduling, such as... Figure 4 As shown, this allows each node to upload data in an orderly manner within an independent transmission time slot after completing the stimulus acquisition operation, thus avoiding data conflicts.

[0029] Combining the functional characteristics of a single node with the control method of multiple nodes, the overall architecture of the wireless ultrasonic guided wave multi-node monitoring system in this invention is formed, such as... Figure 5 As shown, the system consists of a host computer and multiple wireless monitoring nodes. The host computer issues unified scheduling commands via a wireless channel, and the nodes are responsible for configuring their status according to the commands issued by the host computer. In single-node mode, each node can independently complete excitation, data acquisition, and uploading. In multi-node collaborative mode, the host computer uniformly controls the working status of each node and introduces a mechanism to avoid transmission conflicts at the communication layer, thereby ensuring the orderly uploading of data from multiple nodes.

[0030] Under the above system architecture, the overall operation flow of the present invention is as follows: Figure 6 As shown, the process includes key steps such as node standby, system initialization, scheduling command issuance, node status configuration, excitation signal transmission, echo signal acquisition, and wireless data transmission, forming a complete monitoring loop that ensures the synchronization of excitation acquisition across multiple nodes and the coordination of data transmission.

[0031] Figure 7 This is a multi-node implementation example of the present invention, demonstrating the application of the above-described operation process in a real-world scenario. In this implementation example, the system consists of a host computer and three wireless monitoring nodes, which are arranged on a steel plate with dimensions of 1.5m × 1.5m and a thickness of 1.8mm. At the start of monitoring, each node powers on and initializes. Then, the host computer sends a unified scheduling command to the three nodes on the steel plate via a wireless channel. After receiving and parsing the command, each node is configured in self-excitation and self-reception mode to trigger the excitation module to drive the piezoelectric ceramic to generate guided wave signals and collect the guided wave signals in the steel plate. Nodes 2 and 3 are configured in acquisition mode to synchronously collect the guided wave signals in the steel plate. After signal acquisition, the three sets of data are sequentially sent to the host computer via the wireless channel (in this implementation example, data is uploaded in the preset order according to the scheduling command, from node 1 to node 3), and then integrated and visualized by the user terminal. Finally, all nodes enter a low-power standby state, completing a full monitoring process.

[0032] The above description is only for the purpose of helping to understand the method and core idea of ​​the present invention; at the same time, those skilled in the art will know that, based on the idea of ​​the present invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A piezoelectric ultrasonic guided wave monitoring node, characterized in that, The monitoring node includes an excitation module, a data acquisition module, a main control module, a low-power control module, and a LoRa wireless communication module, and can operate as an independent monitoring unit. The excitation module consists of a high-voltage pulse drive circuit composed of a driver and MOSFET transistors, used to output bipolar excitation pulses to drive piezoelectric ceramics to generate ultrasonic guided waves. The data acquisition module includes an ADC chip and a potential shift and attenuation circuit to support signal acquisition over a wide voltage range and bandwidth. The ZYNQ main control module coordinates and controls the various functional modules within the node and performs buffering processing on the acquired data. The low-power control module consists of an STM32L0 series low-power microcontroller, MOSFETs, and relays. The microcontroller uses an RTC timed wake-up method, powering the drive circuit during the working cycle and entering a low-power sleep state during non-working cycles to reduce standby power consumption. The wireless communication module, based on a LoRa chip, enables bidirectional communication between the monitoring node and the host computer.

2. A multi-node wireless control method based on the monitoring node described in claim 1, characterized in that, This method can be implemented in a monitoring system consisting of a host computer and multiple monitoring nodes. The host computer sends unified scheduling instructions to each monitoring node and configures the working mode and data upload time slot of each monitoring node using a time-division multiple access (TDMA) data transmission mechanism. The method includes the following steps: Step 1: The host computer first generates a complete scheduling instruction based on the monitoring requirements and sends it to each node in the monitoring system via a wireless channel. The instruction includes a frame header, function control bytes, delay control bytes, and frame tail, which are used to define the working mode of each node and the corresponding data transmission time slot. Step 2: After each monitoring node receives the instruction from the host computer, the main control chip first verifies the validity of the data. If the instruction is valid, the monitoring node enters the corresponding working mode according to the function control byte, and uses the host computer instruction as the global time reference to synchronously start the excitation and acquisition functions. Step 3: After completing data acquisition, each node starts a timer according to the transmission time slot set by the delay control byte, and sends the data to the host computer through the wireless communication module in the corresponding independent time slot; Step 4: The host computer receives the data uploaded by each node, preprocesses the data, and combines it with a defect identification algorithm to achieve health monitoring of the tested structure.

3. A wireless ultrasonic guided wave monitoring system, characterized in that, It includes a host computer and multiple monitoring nodes as described in claim 1; the host computer remotely controls the nodes using the wireless control method of claim 2.

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