A wireless operating condition monitoring system and method for clustered drive shafts

Abstract

This invention relates to the field of industrial equipment condition monitoring and industrial Internet of Things (IIoT) technology, specifically a wireless condition monitoring system and method for clustered drive shafts. The system includes multiple monitoring node modules installed in through holes in the drive shaft body and at least one centralized signal receiving and communication device. The monitoring node module includes a thin-film pressure sensing unit, a low-power dual-threshold comparison circuit, a wireless optical communication transmitting module, and a button battery power supply module. The sensing unit senses the pressure on the inner wall of the through hole and outputs an analog voltage. The dual-threshold comparison circuit determines the condition as one of three conditions: normal torque, torque loss, or torque overload. The optical communication module is only activated when the condition changes to send a light pulse signal with node identification. The centralized device receives and parses the signals from each node and sends alarm information to the PLC via the Modbus-TCP / IP protocol.

Description

Technical Field

[0001] This invention relates to the field of industrial equipment condition monitoring and industrial Internet of Things (IIoT) technology, specifically to a wireless condition monitoring system and method for clustered drive shafts. Specifically, it relates to a system and method based on thin-film pressure sensing and wireless optical communication technology, characterized by extremely low single-node cost, high temperature resistance, and the ability to perform distributed wireless monitoring of the normal torque, torque loss, and torque overload conditions of hundreds or thousands of drive shafts in a factory. Background Technology

[0002] In industrial settings such as textile machinery, chemical fiber winding equipment, injection molding machines, logistics sorting lines, and printing and packaging machinery, a large number of drive shafts are often deployed. These drive shafts typically drive actuators via motors and couplings, and their operating status directly affects product quality and production safety. During normal operation, the torque borne by the drive shaft is usually within a stable range of 1-2 N·m. Typical abnormal operating conditions include two types: First, the loss of torque due to load shedding, material interruption, belt breakage, or clutch failure. In this case, although the drive shaft is rotating, the torque it bears drops sharply to 0 or close to 0, resulting in energy waste and production interruption. Second, torque overload due to mechanical jamming, bearing seizure, or foreign object intrusion. In this case, the torque rises sharply to 100 N·m or even higher; if the machine is not stopped in time, it may cause motor burnout, transmission component breakage, or even a fire.

[0003] Currently, existing technologies for monitoring the working condition of drive shafts mainly include the following categories:

[0004] (1) Motor current monitoring method: The load status is indirectly determined by detecting the current of the drive motor. This method has a delayed response. When the current rises significantly, the drive shaft body may have already been subjected to overload impact, making it impossible to achieve rapid protection. In addition, in a system with multiple shafts sharing a bus, the fault characteristics of a single shaft are easily submerged, making it difficult to accurately locate the specific faulty shaft.

[0005] (2) Torque sensor method: A dedicated torque sensor is inserted into the transmission chain to accurately measure real-time torque. However, the unit price of an industrial-grade torque sensor is usually several hundred to several thousand yuan. If it is deployed in a factory with thousands of transmission shafts, the hardware cost can reach hundreds of thousands of yuan, which is difficult for enterprises to afford. In addition, torque sensors usually require wired power supply and signal transmission, and conductive slip rings need to be used on the rotating shaft, which makes the installation complicated and the long-term reliability is poor.

[0006] (3) Strain gauge telemetry: Resistance strain gauges are attached to the surface of the drive shaft body, and torque is obtained through wireless telemetry. This method has drawbacks such as high requirements for strain gauge attachment process, difficulty in temperature drift compensation, and high power consumption of the wireless transmitter requiring frequent battery replacement, making it difficult to promote on a large scale. In addition, the reliability of strain gauges and adhesive layers in long-term service at high temperature environments (such as 120°C) is poor.

[0007] (4) Vibration monitoring method: The vibration changes of the bearing are monitored by an accelerometer. This method is more sensitive to bearing failures, but it is difficult to accurately distinguish between torque loss and torque overload conditions, and it also faces the constraints of cost and wiring.

[0008] Furthermore, existing wireless sensing solutions mostly employ radio frequency (RF) communication methods such as Bluetooth and Wi-Fi. In dense industrial environments, the simultaneous operation of numerous RF nodes can lead to co-channel interference; in environments surrounded by metal equipment, RF signals suffer severe attenuation, impacting communication reliability. Wireless optical communication (such as infrared optical communication), on the other hand, offers advantages such as good directivity, strong resistance to electromagnetic interference, no spectrum restrictions, and low cost, making it particularly suitable for distributed node data acquisition under line-of-sight conditions in industrial workshops. However, it has not yet been fully utilized in the field of drive shaft condition monitoring.

[0009] In summary, existing technologies suffer from the following prominent contradictions: On the one hand, factories contain a large number of drive shafts, and their torque loss and torque overload faults need to be detected and alarmed to the PLC control system within 5 seconds; on the other hand, existing monitoring methods are either too costly, consume too much power, or have poor environmental adaptability (not resistant to high temperatures, unreliable), making it impossible to achieve large-scale, low-cost, high-temperature resistant, and maintenance-free distributed deployment. Therefore, there is an urgent need for a dedicated drive shaft condition monitoring solution with a single-node hardware cost of less than 15 yuan, using wireless optical communication transmission, a battery life of over 2 years, the ability to withstand temperatures up to 120℃, a single centralized signal receiving and communication device capable of simultaneously managing more than 300 nodes, and support for Modbus-TCP / IP protocol output. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a wireless operating condition monitoring system and method for clustered drive shafts, overcoming the deficiencies of existing technologies.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] This invention provides a wireless condition monitoring system for clustered drive shafts, comprising:

[0013] At least one monitoring node module, each of the monitoring node modules being installed in a through hole radially opened in the body of a drive shaft;

[0014] At least one centralized signal receiving and communication device, wherein the monitoring node module and the centralized signal receiving and communication device establish a one-way optical pulse wireless communication connection through a wireless optical communication transmitting module and an optical communication receiving module;

[0015] The monitoring node module includes a sealed housing and a thin-film pressure sensing unit, a dual threshold comparison circuit, a wireless optical communication transmitting module, and a power supply module disposed within the sealed housing.

[0016] The thin-film pressure sensing unit is attached to the inner wall of the through hole, and its output terminal is electrically connected to the input terminal of the dual threshold comparison circuit.

[0017] The output terminal of the dual threshold comparison circuit is electrically connected to the control input terminal of the wireless optical communication transmitting module.

[0018] The power supply module is electrically connected to the power supply terminals of the dual threshold comparison circuit and the wireless optical communication transmitting module, respectively.

[0019] The centralized signal receiving and communication device includes an optical communication receiving module, a main control processing unit, and a communication interface module;

[0020] The output terminal of the optical communication receiving module is connected to the input terminal of the main control processing unit;

[0021] The output of the main control processing unit is connected to the input of the communication interface module.

[0022] Preferably, the sealing housing is made of high-temperature resistant engineering plastic, and the encapsulation structure is designed to be non-destructive. The thin-film pressure sensing unit is a piezoresistive flexible thin-film pressure sensor with a sensitive layer thickness of no more than 0.5 mm and a surface coated with an oil-resistant, wear-resistant, and high-temperature resistant polymer protective coating.

[0023] Preferably, the dual threshold comparison circuit includes a dual differential comparator and a reference voltage generation circuit composed of a first voltage divider network and a second voltage divider network.

[0024] The output of the first voltage divider network is connected to the inverting input of the first comparator in the dual-channel differential comparator; it is used to generate the lower limit reference voltage.

[0025] The output of the second voltage divider network is connected to the non-inverting input of the second comparator in the dual-channel differential comparator; it is used to generate the upper limit reference voltage.

[0026] The output of the thin-film pressure sensing unit is filtered and then connected to both the non-inverting input of the first comparator and the inverting input of the second comparator.

[0027] The outputs of the first and second comparators are connected to the positive terminal of the power supply module via pull-up resistors, and then connected to the control input terminal of the wireless optical communication transmitter module.

[0028] Preferably, both the first voltage divider network and the second voltage divider network include two resistors and an adjustable resistor, which are used to adjust the corresponding reference voltage threshold according to the normal operating torque range and overload threshold of different specifications of the drive shaft body.

[0029] Preferably, the wireless optical communication transmitting module of the monitoring node module is configured to continuously transmit multiple frames of identical data during a single state change, with each frame containing a CRC checksum; the centralized signal receiving and communication device is configured to compare and verify the received multiple frames of data, and only confirm a valid state change when multiple consecutive frames of data are consistent.

[0030] The present invention also provides a wireless operating condition monitoring method for clustered drive shafts, used to implement the system described in any of the above claims, comprising the following steps:

[0031] Step S1: Mass-produce monitoring node modules according to uniform specifications. Each monitoring node module should integrate a low-power microcontroller to store a unique identification code. Each monitoring node module is pre-set with a unique identification code and undergoes initial calibration upon leaving the factory.

[0032] Step S2: On the force-bearing surface of the inner wall of the through hole opened in each target drive shaft body within the industrial site, attach a thin film pressure sensing unit and install a monitoring node module including a dual threshold comparison circuit, a wireless optical communication transmission module and a power supply module; bind the identity of the monitoring node module to the physical location on site and enter it into the node database of the centralized signal receiving and communication device.

[0033] Step S3: Each monitoring node module independently senses the compressive force on the inner wall of the through hole and outputs an analog voltage signal. The analog voltage signal is converted into a digital logic level signal representing normal torque, torque loss, or torque overload conditions through a dual threshold comparison circuit.

[0034] Step S4: When the digital logic level signal undergoes a state switch, the wireless optical communication transmitting module is awakened and sends out a status data signal containing the node identification and current operating condition code in an optical pulse modulation manner.

[0035] Step S5: The centralized signal receiving and communication device deployed at the industrial site receives optical communication signals emitted by each monitoring node module in real time through its optical communication receiving module. After being parsed by the main control processing unit, the alarm information and the corresponding drive shaft body identity information are sent to the third-party device through the standard industrial protocol. When any monitoring node module reports a loss of torque or torque overload, the centralized signal receiving and communication device outputs an alarm signal within the allowed time.

[0036] Preferably, in step S2, the determination logic for the digital logic level signal is as follows:

[0037] When the simulated voltage signal is less than the lower limit reference voltage, the torque loss condition is determined.

[0038] When the simulated voltage signal is greater than or equal to the lower limit reference voltage and less than or equal to the upper limit reference voltage, the torque is determined to be in normal operating condition.

[0039] When the simulated voltage signal is greater than the upper limit reference voltage, a torque overload condition is determined.

[0040] Preferably, the wireless optical communication transmitting module is in a deep sleep state during stable operating conditions; when the digital logic level signal output by the dual threshold comparison circuit changes, the wireless optical communication transmitting module is interrupted and woken up, completes initialization, status reading and continuous transmission of optical pulse modulation signals within a preset time window, and then enters a deep sleep state again.

[0041] Preferably, a threshold calibration step is included before step S2: when the drive shaft body is running normally for the first time, the adjustable resistor in the dual threshold comparison circuit is adjusted to set the lower threshold of the voltage window corresponding to the normal operating condition and the upper threshold of the voltage window corresponding to the overload operating condition.

[0042] Preferably, the method further includes a battery power monitoring step: the monitoring node module sends status data signals along with current battery voltage information; the centralized signal receiving and communication device generates a low battery reminder signal for nodes whose battery voltage is lower than a preset threshold; and the centralized signal receiving and communication device periodically checks the online status of each monitoring node module, and generates a node offline alarm when a node has not received any signal for a preset time.

[0043] This invention provides a wireless operating condition monitoring system and method for clustered drive shafts. It has the following beneficial effects:

[0044] Disruptive low cost: By reusing the through-hole structure on the drive shaft body, replacing the torque sensor with a thin-film pressure sensing unit, and utilizing a low-power dual-threshold comparison circuit and a wireless optical communication transmission module, the material cost per node is controlled to within 15 yuan. Compared with traditional torque sensor solutions, the cost is reduced by more than 95%, making large-scale deployment of thousands of nodes economically feasible.

[0045] True maintenance-free wireless monitoring: Based on an event-driven optical communication mechanism and ultra-low power circuit design, the monitoring node module consumes less than 0.5mW under steady-state conditions, and a single button battery (power supply module) can operate continuously for more than 2 years. This completely solves the slip ring problem of wired transmission of rotating parts and the pain point of frequent battery replacement in wireless RF solutions.

[0046] Supports large-scale cluster management: Adopting a "one-to-many" architecture, a single centralized signal receiving and communication device can simultaneously manage more than 300 monitoring node modules. Wireless optical communication has the advantages of good directionality and no electromagnetic interference, allowing multiple devices to work in parallel in the same space without interfering with each other. The system supports flexible expansion to meet the deployment needs of factories of different sizes.

[0047] Rapid fault response and precise location: The low-power dual-threshold comparison circuit is a pure hardware comparison structure, with a response time of milliseconds to changes in operating conditions. Combined with low-latency optical communication transmission and Modbus-TCP / IP protocol output, it can send an alarm signal containing the specific drive shaft identification information to the PLC within 5 seconds, providing timely basis for automatic shutdown protection and accurately guiding maintenance personnel to locate the faulty shaft.

[0048] Harsh environmental adaptability: The monitoring node module adopts a sealed housing and is designed to be non-destructive, with a protection level of IP54 or higher. The thin-film pressure sensing unit and circuit can withstand high temperatures of 120℃, making it suitable for high-temperature industrial scenarios such as injection molding machines, drying equipment, and heat treatment lines.

[0049] Easy to install and highly adaptable: It directly utilizes the existing through-hole on the drive shaft body, requiring no modification to the shaft structure. The thin-film pressure sensing unit is thin and flexible, adaptable to through-holes of different shapes and sizes. The entire installation process only requires attaching the sensor and fixing the sealing housing, with a single-node installation time of no more than 10 minutes.

[0050] High reliability and prevention of false alarms and missed alarms: Through multiple redundancy designs such as continuous transmission and comparison verification of multiple frames, CRC verification, battery power monitoring, and offline node detection, the system ensures that there are no false alarms or missed alarms in complex industrial environments. Attached Figure Description

[0051] Figure 1 Overall deployment architecture diagram of the system of this invention.

[0052] Figure 2 The structural diagram of the transmission shaft body of this invention.

[0053] Figure 3 Overall flowchart of the method of this invention.

[0054] Figure 4 This invention provides an event-driven wake-up and communication timing diagram. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] like Figures 1-2 As shown, in one embodiment, a wireless condition monitoring system for clustered drive shafts includes:

[0057] At least one monitoring node module (deployed in the industrial site; after initial installation, the monitoring node module, by adjusting the adjustable resistor in the (low-power) dual threshold comparison circuit, sets the lower threshold of the voltage window corresponding to 1-2 N·m normal operating conditions and the upper threshold of the voltage window corresponding to 100 N·m overload conditions), each monitoring node module is installed on a drive shaft body (when the drive shaft body transmits torque, the actuating component (such as a pry bar, wrench, mating key, etc.) inserted into the through hole will squeeze the inner wall of the through hole, and the squeezing force is positively correlated with the transmitted torque). Under normal operating conditions, the drive shaft body withstands a stable torque of 1-2 N·m, corresponding to a certain range of compressive force. When a torque loss fault occurs, the torque drops sharply to 0, and the compressive force drops sharply accordingly. When a torque overload fault occurs, the torque rises sharply to 100 N·m or more, and the compressive force rises sharply accordingly. The thin-film pressure sensing unit senses this change in compressive force and outputs a corresponding analog voltage signal. A radially opened through-hole (the through-hole can be a strip-shaped hole (e.g., 7 mm wide, 36 mm long), a circular hole, or an internal hexagonal hole, etc.; the drive shaft body is used to transmit torque, and the through-hole facilitates the disassembly and assembly of the monitoring node module) is also present.

[0058] At least one centralized signal receiving and communication device, wherein the monitoring node module and the centralized signal receiving and communication device establish a one-way optical pulse wireless communication connection through a wireless optical communication transmitting module and an optical communication receiving module;

[0059] The monitoring node module includes a sealed housing and a thin-film pressure sensing unit, a (low-power) dual threshold comparison circuit, a wireless optical communication transmitting module (the wireless optical communication transmitting module is an infrared light-emitting diode (IR LED) and its driving circuit, with a transmission wavelength of 850nm or 940nm and a wide-angle design of 30° to 60°, and uses optical pulse modulation (such as 38kHz carrier modulation) to encode node identification and operating information to improve the ability to resist ambient light interference) and a power supply module;

[0060] The thin-film pressure sensing unit is attached to the inner wall of the through hole, and its output terminal is electrically connected to the input terminal of the low-power dual threshold comparison circuit.

[0061] The output of the (low-power) dual threshold comparison circuit is electrically connected to the control input of the wireless optical communication transmitting module; (the (low-power) dual threshold comparison circuit is preset with a lower limit reference voltage VL corresponding to the idle / torque loss condition of the drive shaft body and an upper limit reference voltage VH corresponding to the stall / torque overload condition of the drive shaft body; it is used to compare the analog voltage signal with the lower limit reference voltage and the upper limit reference voltage respectively, and output digital logic level signals representing the three conditions of normal torque, torque loss, and torque overload).

[0062] The power supply module is electrically connected to the power supply terminals of the (low-power) dual threshold comparison circuit and the wireless optical communication transmitting module, respectively; (the power supply module uses a disposable lithium manganese button battery (such as CR2032, capacity 240mAh) or a lithium thionyl chloride battery (such as ER14250), the battery is directly soldered or mounted on the node circuit board through a battery holder to ensure contact reliability in a vibration environment).

[0063] The centralized signal receiving and communication device (a single centralized signal receiving and communication device supports the simultaneous reception and processing of optical communication signals emitted by no less than 300 monitoring node modules, and the effective and reliable transmission distance of the optical communication signals is no less than 15 meters) includes an optical communication receiving module (the optical communication receiving module is a wide-angle infrared receiver tube (or infrared receiver head, such as VS1838B) and a signal amplification and shaping circuit), a main control processing unit, and an (industrial) communication interface module;

[0064] The output of the optical communication receiving module is connected to the input of the main control processing unit (for transmitting the received and demodulated status data signal to the main control processing unit);

[0065] The output of the main control processing unit is connected to the input of the (industrial) communication interface module (the main control processing unit is used to parse and process the received operating data of each monitoring node module (decoding, identification, operating condition judgment and data management), and send alarm information (node ​​address and fault type code) and monitoring node module identification information to third-party equipment (such as PLC) through the (industrial) communication interface module using standard industrial protocols (such as Modbus-TCP / IP)).

[0066] In this embodiment, the sealing housing is made of high-temperature resistant engineering plastic (such as PPS or PA66), and the encapsulation structure is designed to be non-destructive (such as by ultrasonic welding or epoxy resin potting). The thin-film pressure sensing unit is a piezoresistive flexible thin-film pressure sensor with a sensitive layer thickness of no more than 0.5 mm. The surface is coated with an oil-resistant, wear-resistant, and high-temperature resistant polymer protective coating and is configured to withstand an operating ambient temperature of at least 120°C.

[0067] In this embodiment, the (low-power) dual threshold comparison circuit includes a dual differential comparator (LM393 chip) and a reference voltage generation circuit composed of a first voltage divider network and a second voltage divider network.

[0068] The output of the first voltage divider network (composed of resistors R2, R3 and adjustable resistor RP1) is connected to the inverting input of the first comparator in the dual-channel differential comparator; it is used to generate the lower limit reference voltage VL.

[0069] The output of the second voltage divider network (composed of resistors R4, R5, and adjustable resistor RP2) is connected to the non-inverting input of the second comparator in the dual-channel differential comparator; it is used to generate the upper limit reference voltage VH.

[0070] The output of the thin-film pressure sensing unit is connected to both the non-inverting input of the first comparator and the inverting input of the second comparator after passing through a filtering circuit (which consists of a resistor R1 and a capacitor C1).

[0071] The outputs of the first and second comparators are connected to the positive terminal of the power supply module via pull-up resistors (R6 and R8), and then connected to the control input terminal of the wireless optical communication transmitter module.

[0072] In this embodiment, both the first voltage divider network and the second voltage divider network include two resistors and one adjustable resistor (the first voltage divider network consists of resistors R2, R3 and adjustable resistor RP1; the second voltage divider network consists of resistors R4, R5 and adjustable resistor RP2), which are used to adjust the corresponding reference voltage threshold according to the normal operating torque range (e.g., 1-2 N.m) and overload threshold (e.g., 100 N.m) of different specifications of the drive shaft body.

[0073] In this embodiment, the wireless optical communication transmitting module of the monitoring node module is configured to continuously transmit multiple frames of the same data during a single state change, with each frame containing a CRC checksum; the centralized signal receiving and communication device is configured to compare and verify the received multiple frames of data, and only confirm a valid state change when multiple consecutive frames of data are consistent.

[0074] like Figures 3-4 As shown, the present invention provides a wireless operating condition monitoring method for clustered drive shafts, used to implement the system described in any of the above claims, comprising the following steps:

[0075] Step S1: Mass production and pre-configuration: Mass produce monitoring node modules according to uniform specifications. Each monitoring node module should integrate a low-power microcontroller or hardware coding circuit to store a unique identification code. Each monitoring node module is pre-configured with a unique identification code and undergoes initial calibration at the factory.

[0076] Step S2: On-site installation and registration: On the force-bearing surface of the through hole opened in the body of each target drive shaft in the industrial field, attach a thin film pressure sensing unit and install a monitoring node module including a low-power dual threshold comparison circuit, a wireless optical communication transmission module and a power supply module; bind the identity of the monitoring node module to the physical location on site and enter it into the node database of the centralized signal receiving and communication device.

[0077] Step S3: Working condition sensing and signal conversion: Each monitoring node module independently senses the compressive force on the inner wall of the through hole and outputs an analog voltage signal. The analog voltage signal is converted into a digital logic level signal representing the working conditions of normal torque, torque loss, or torque overload through a low-power dual threshold comparison circuit.

[0078] Step S4: State change triggers communication: When the digital logic level signal undergoes a state switch, the wireless optical communication transmitting module is awakened and sends out a state data signal containing the node identity and current operating condition code in the form of optical pulse modulation.

[0079] Step S5: Centralized reception and alarm output: The centralized signal receiving and communication device deployed in the industrial site receives optical communication signals emitted by each monitoring node module in real time through its optical communication receiving module. After being parsed by the main control processing unit, the alarm information and the corresponding drive shaft body identification information are sent to the third-party device through the standard industrial protocol. When any monitoring node module reports a loss of torque or torque overload, the centralized signal receiving and communication device outputs an alarm signal within the allowed time.

[0080] In this embodiment, in step S2, the determination logic for the digital logic level signal is as follows:

[0081] When the analog voltage signal is less than the lower limit reference voltage ( When the torque disappears, both the first comparator and the second comparator output a low level, thus determining the torque loss condition (corresponding to a fault state where the torque suddenly drops to 0 or close to 0).

[0082] When the analog voltage signal is greater than or equal to the lower limit reference voltage and less than or equal to the upper limit reference voltage ( When the torque is normal, the first comparator outputs a high level and the second comparator outputs a low level, thus determining the normal torque condition (corresponding to the normal working torque range of 1-2 N.m).

[0083] When the analog voltage signal is greater than the upper limit reference voltage ( When the torque overload condition is detected, both the first comparator and the second comparator output a high level, which determines the torque overload condition (corresponding to a fault state where the torque suddenly increases to 100 N.m or more).

[0084] In this embodiment, the wireless optical communication transmitting module is in a deep sleep state during stable operating conditions; when the digital logic level signal output by the (low-power) dual threshold comparison circuit changes, the wireless optical communication transmitting module is interrupted and woken up, completes initialization, status reading and continuous transmission of optical pulse modulation signals within a preset time window, and then enters a deep sleep state again.

[0085] In this embodiment, a threshold calibration step is included before step S2: when the drive shaft body is running normally for the first time, the adjustable resistor in the low-power dual threshold comparison circuit is adjusted to set the lower threshold of the voltage window corresponding to the normal operating condition and the upper threshold of the voltage window corresponding to the overload operating condition.

[0086] In this embodiment, the method further includes a battery power monitoring step: the monitoring node module sends status data signals along with current battery voltage information; the centralized signal receiving and communication device generates a low battery reminder signal for nodes whose battery voltage is lower than a preset threshold; and the centralized signal receiving and communication device periodically checks the online status of each monitoring node module, and generates a node offline alarm when a node has not received any signal for a preset time.

[0087] In a specific embodiment, to achieve the goal of a single-node material cost of less than 15 RMB, the present invention adopts the following specific design methods:

[0088] Thin-film pressure sensing unit 120℃ piezoresistive flexible thin film <5.0 Dual threshold comparison circuit LM393 + RC components + adjustable resistor <1.5 Wireless optical communication transmitter module IR LED + Driver Transistor + Modulation Circuit <1.5 Printed Circuit Board Double-layer FR-4 high-temperature resistant small board <1.0 Power supply module (button battery) CR2032 High Temperature Resistant Type <1.5 Packaging housing and accessories High-temperature resistant PPS housing, potting compound <2.5 total <13.0

[0089] By simplifying functions (only performing three-state classification, without continuous waveform acquisition), reusing shaft structure, selecting mature and low-cost domestic chip solutions, and adopting pure hardware comparison logic to reduce dependence on MCU, the BOM cost of a single node can be stably controlled within 15 yuan, making full deployment in factories with hundreds or thousands of drive shaft bodies an economically feasible solution.

[0090] Example 1: Monitoring of Drive Shaft Clusters in Chemical Fiber Winding Machines

[0091] A chemical fiber production enterprise has a total of 240 POY winding machines. Each winding machine contains 4 key drive shafts (friction roller shaft, grooved drum shaft, traverse shaft, and chuck shaft). A total of 960 drive shafts in the workshop need to be monitored for torque loss / torque overload.

[0092] Monitoring Node Module: The drive shaft body is a 40mm diameter tempered 45 steel shaft with a pre-drilled through-hole (7mm wide, 36mm long) for installing the monitoring node module. The sealed housing is fixed to the center of the drive shaft end face and integrates a thin-film pressure sensing unit, a low-power dual threshold comparison circuit, a wireless optical communication transmitter module, and a power supply module.

[0093] Thin-film pressure sensing unit: Employs a high-temperature resistant piezoresistive flexible thin-film sensor with a sensitive area size of 5mm × 20mm and a thickness of 0.3mm. It is coated with an oil-resistant, wear-resistant, and high-temperature resistant polymer protective coating, capable of withstanding a working environment of 120℃. It is attached to the stress-bearing surface of the long side inner wall of the through-hole using high-temperature resistant epoxy resin adhesive.

[0094] Low-power dual-threshold comparator circuit: Employs an LM393DR2G dual-channel differential comparator, with a power supply voltage VCC=3.3V (regulated by an LDO from a button battery). A filter circuit is constructed using resistor R1=10kΩ and capacitor C1=100nF. The first voltage divider network, consisting of resistors R2 and R3 and an adjustable resistor RP1, generates the lower limit reference voltage VL; the second voltage divider network, consisting of resistors R4 and R5 and an adjustable resistor RP2, generates the upper limit reference voltage VH. The comparator output is connected to the control input of the wireless optical communication transmitter module via an 820kΩ pull-up resistor.

[0095] Wireless optical communication transmitter module: It adopts a 940nm infrared light-emitting diode with a 45° emission angle and a 38kHz modulation circuit. When a single state change occurs, it continuously transmits multiple frames of the same data (each frame contains a CRC check code).

[0096] Power supply module: Uses CR2032 high-temperature resistant lithium manganese button battery with a capacity of 240mAh, which is directly soldered onto the circuit board.

[0097] Centralized signal receiving and communication device: Since 960 nodes exceed the capacity of a single unit of 300 nodes, four units are deployed in different areas. Each unit includes an optical communication receiving module (infrared receiver head), a main control processing unit (STM32F407), and an industrial communication interface module (Modbus-TCP / IP). The device is configured to compare and verify the received multi-frame data, and only confirm a valid state change when multiple consecutive frames of data are consistent.

[0098] Step S1 (Mass Production and Pre-configuration): Mass produce monitoring node modules according to uniform specifications, pre-set a unique identification code for each module upon leaving the factory, and complete the initial calibration.

[0099] Step S2 (On-site installation and registration): Attach the thin-film pressure sensing unit to the stress surface of the inner wall of the through hole and install the fully encapsulated monitoring node module; bind the node identification with the physical location (e.g., “Workshop 2 Line 3 No. 17 Winding Machine”) using a handheld configuration tool and enter it into the node database of the centralized signal receiving and communication device.

[0100] Step S3 (Operating Condition Sensing and Signal Conversion): Under normal production conditions (torque approximately 1.5 Nm), the sensor output voltage is approximately 1.8 V; approximately 0.2 V when simulating torque loss; approximately 4.2 V when simulating 100 Nm overload; adjust the adjustable resistor RP1 to... =0.8V, adjust the adjustable resistor RP2 to make =3.5V; Judgment <0.8V → Torque disappears; 0.8V≤ ≤3.5V → Torque is normal; >3.5V → Torque overload.

[0101] Step S4 (State Change Triggers Communication): When the digital logic level signal undergoes a state switch, the wireless optical communication transmitting module is awakened and continuously sends multiple frames of optical pulse modulation signals containing node ID and operating condition code.

[0102] Step S5 (Centralized Reception and Alarm Output): Four centralized signal receiving and communication devices receive signals in real time, and after parsing, send alarm information to the central control room PLC via Modbus-TCP / IP. When torque loss or overload is detected, an alarm signal is output within 5 seconds.

[0103] Battery power monitoring and offline detection: Nodes send status data along with the current battery voltage; the receiving device generates a low battery alert for nodes with voltages below a preset threshold; and periodically checks the online status of nodes, generating an offline alarm if no signal is received within a timeout period.

[0104] The "torque loss" event was detected 52 times, with an average response time of 3.2 seconds, achieving the alarm within the "preset allowable time" in step S5;

[0105] Three "torque overload" events were detected, and a shutdown signal was issued within 4 seconds for each event.

[0106] Five out of 960 nodes experienced occasional packet loss in optical communication, which was resolved after adjusting the angle of the receiving device—the verified "multi-frame comparison and verification" mechanism can effectively eliminate occasional interference.

[0107] After 6 months, the battery voltage dropped by an average of 0.18V, with an expected lifespan of 2.5 years—verifying the actual effect of the low-power dual threshold comparison circuit with steady-state power consumption of <0.5mW.

[0108] No false alarms or missed alarms – verifying reliable wake-up and data verification mechanisms.

[0109] The traditional solution costs about 600 yuan per axis for monitoring, while the cost of a single node in this invention is 11.5 yuan. With the receiving device costing about 3 yuan per node, the total cost per node is about 14.5 yuan. The total investment in the workshop is about 14,000 yuan, which is only 2.4% of the cost of the traditional solution.

[0110] Example 2: High-Temperature Environment Monitoring of Mold Adjustment Drive Shaft in Injection Molding Machine Group

[0111] A certain injection molding workshop has 100 injection molding machines, each mold adjustment mechanism contains a drive shaft; the ambient temperature is 100℃~120℃, and mold jamming can cause torque overload (>150N.m).

[0112] The drive shaft has an 8mm circular through-hole, with the diaphragm pressure sensing unit formed as a ring-shaped plate embedded in the inner wall of the hole. The sealing housing is made of PPS engineering plastic (temperature resistant up to 150℃), and the internal components are automotive-grade models resistant to 125℃. The power supply module uses a lithium thionyl chloride battery ER14250 (suitable for temperatures from -55℃ to 125℃).

[0113] Normal mold adjustment torque is approximately 1.2 Nm, corresponding to a sensor voltage of 1.5 V. Adjust the adjustable resistor RP1 of the first voltage divider network to... =0.6V, adjust the adjustable resistor RP2 of the second voltage divider network to make =3.0V.

[0114] Deploy one centralized signal receiving and communication device (covering an area of ​​2000 square meters) and install it in the center of the workshop at a high position. Register the node according to step S2, the judgment logic of step S3 is the same as above, wake up the transmission in step S4, and send an alarm to the injection molding machine PLC via Modbus-TCP / IP in step S5, with a preset allowable time of 5 seconds.

[0115] After 3 months of operation, it successfully issued warnings for 12 instances of mold adjustment torque overload, all of which triggered an alarm within 5 seconds. The PLC automatically stopped the mold adjustment motor, preventing chain breakage accidents (the cost of a single repair is approximately 800 yuan, saving nearly 10,000 yuan in 3 months, with an investment payback period of less than 4 months).

[0116] After three months of continuous operation at 120°C, all node packages showed no deformation or cracking, and the circuits showed no high-temperature failure—verifying "withstanding an operating environment temperature of at least 120°C".

[0117] Example 3: Large-scale monitoring of roller drive shafts in logistics sorting lines

[0118] A certain express delivery transit center has 8 sorting lines, each containing approximately 150 electric roller drive shafts, totaling 1200 shafts. Loss of torque (belt breakage) or overload (package jamming) requires immediate attention.

[0119] The 1200 monitoring nodes are deployed in zones using four centralized signal receiving and communication devices (each supporting ≥300 nodes). The Modbus-TCP / IP outputs of each device are uniformly connected to the central control PLC.

[0120] The PLC program is configured to detect belt breakage (emergency stop) when three or more rollers simultaneously report "torque loss"; a single "torque overload" alarm prompts the operator to check the corresponding roller. Verification through multi-frame comparison avoids false alarms.

[0121] Adding a new node only requires installing hardware and registering it in the receiving device, without modifying the network; there is no mutual interference between optical communication nodes; a single node failure does not affect the overall system; multiple receiving devices work in parallel, and data is uniformly aggregated.

[0122] After one year of operation: 86 instances of loss of torque due to belt breakage were detected (machine stopped within 5 seconds), and 215 instances of torque overload due to package jamming were detected (operators cleaned up in time).

[0123] All 1200-node battery voltages are normal, with no false alarms or missed alarms.

[0124] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wireless condition monitoring system for clustered drive shafts, characterized in that, include: At least one monitoring node module, each of the monitoring node modules being installed in a through hole radially opened in the body of a drive shaft; At least one centralized signal receiving and communication device, wherein the monitoring node module and the centralized signal receiving and communication device establish a one-way optical pulse wireless communication connection through a wireless optical communication transmitting module and an optical communication receiving module; The monitoring node module includes a sealed housing and a thin-film pressure sensing unit, a dual threshold comparison circuit, a wireless optical communication transmitting module, and a power supply module disposed within the sealed housing. The thin-film pressure sensing unit is attached to the inner wall of the through hole, and its output terminal is electrically connected to the input terminal of the dual threshold comparison circuit. The output terminal of the dual threshold comparison circuit is electrically connected to the control input terminal of the wireless optical communication transmitting module. The power supply module is electrically connected to the power supply terminals of the dual threshold comparison circuit and the wireless optical communication transmitting module, respectively. The centralized signal receiving and communication device includes an optical communication receiving module, a main control processing unit, and a communication interface module; The output terminal of the optical communication receiving module is connected to the input terminal of the main control processing unit; The output of the main control processing unit is connected to the input of the communication interface module.

2. The system according to claim 1, characterized in that, The sealed housing is made of high-temperature resistant engineering plastic, and the encapsulation structure is designed to be non-destructive. The thin-film pressure sensing unit is a piezoresistive flexible thin-film pressure sensor with a sensitive layer thickness of no more than 0.5 mm and a surface coated with an oil-resistant, wear-resistant, and high-temperature resistant polymer protective coating.

3. The system according to claim 1, characterized in that, The dual threshold comparison circuit includes a dual differential comparator and a reference voltage generation circuit composed of a first voltage divider network and a second voltage divider network. The output of the first voltage divider network is connected to the inverting input of the first comparator in the dual-channel differential comparator; it is used to generate the lower limit reference voltage. The output of the second voltage divider network is connected to the non-inverting input of the second comparator in the dual-channel differential comparator; it is used to generate the upper limit reference voltage. The output of the thin-film pressure sensing unit is filtered and then connected to both the non-inverting input of the first comparator and the inverting input of the second comparator. The outputs of the first and second comparators are connected to the positive terminal of the power supply module via pull-up resistors, and then connected to the control input terminal of the wireless optical communication transmitter module.

4. The system according to claim 3, characterized in that, Both the first voltage divider network and the second voltage divider network include two resistors and one adjustable resistor, which are used to adjust the corresponding reference voltage threshold according to the normal operating torque range and overload threshold of different specifications of the drive shaft body.

5. The system according to claim 1, characterized in that, The wireless optical communication transmitting module of the monitoring node module is configured to continuously send multiple frames of identical data during a single state change, with each frame containing a CRC checksum; the centralized signal receiving and communication device is configured to compare and verify the received multiple frames of data, and only confirm a valid state change when multiple consecutive frames of data are consistent.

6. A wireless operating condition monitoring method for clustered drive shafts, used to implement the system described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step S1: Mass-produce monitoring node modules according to uniform specifications. Each monitoring node module should integrate a low-power microcontroller to store a unique identification code. Each monitoring node module is pre-set with a unique identification code and undergoes initial calibration upon leaving the factory. Step S2: On the force-bearing surface of the inner wall of the through hole opened in each target drive shaft body within the industrial site, attach a thin film pressure sensing unit and install a monitoring node module including a dual threshold comparison circuit, a wireless optical communication transmission module and a power supply module; bind the identity of the monitoring node module to the physical location on site and enter it into the node database of the centralized signal receiving and communication device. Step S3: Each monitoring node module independently senses the compressive force on the inner wall of the through hole and outputs an analog voltage signal. The analog voltage signal is converted into a digital logic level signal representing normal torque, torque loss, or torque overload conditions through a dual threshold comparison circuit. Step S4: When the digital logic level signal undergoes a state switch, the wireless optical communication transmitting module is awakened and sends out a status data signal containing the node identification and current operating condition code in an optical pulse modulation manner. Step S5: The centralized signal receiving and communication device deployed at the industrial site receives optical communication signals emitted by each monitoring node module in real time through its optical communication receiving module. After being parsed by the main control processing unit, the alarm information and the corresponding drive shaft body identity information are sent to the third-party device through the standard industrial protocol. When any monitoring node module reports a loss of torque or torque overload, the centralized signal receiving and communication device outputs an alarm signal within the allowed time.

7. The method according to claim 6, characterized in that, In step S2, the determination logic for the digital logic level signal is as follows: When the simulated voltage signal is less than the lower limit reference voltage, the torque loss condition is determined. When the simulated voltage signal is greater than or equal to the lower limit reference voltage and less than or equal to the upper limit reference voltage, the torque is determined to be in normal operating condition. When the simulated voltage signal is greater than the upper limit reference voltage, a torque overload condition is determined.

8. The method according to claim 6, characterized in that, The wireless optical communication transmitting module is in a deep sleep state during stable operating conditions. When the digital logic level signal output by the dual threshold comparison circuit changes, the wireless optical communication transmitting module is interrupted and woken up. Within a preset time window, it completes initialization, status reading, and continuous transmission of optical pulse modulation signals, and then enters a deep sleep state again.

9. The method according to claim 6, characterized in that, Before step S2, a threshold calibration step is also included: when the drive shaft body is running normally for the first time, the adjustable resistor in the dual threshold comparison circuit is adjusted to set the lower threshold of the voltage window corresponding to the normal working condition and the upper threshold of the voltage window corresponding to the overload working condition.

10. The method according to claim 6, characterized in that, It also includes a battery power monitoring step: when the monitoring node module sends a status data signal, it includes the current battery voltage information; the centralized signal receiving and communication device generates a low battery reminder signal for nodes whose battery voltage is lower than a preset threshold; and the centralized signal receiving and communication device periodically checks the online status of each monitoring node module, and generates a node offline alarm when a node has not received any signal for a preset time.

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