Wireless ultrasonic bolt pre-tightening force detection sensor and detection algorithm thereof

Abstract

The application relates to the technical field of sensor measurement, and discloses a wireless ultrasonic bolt pre-tightening force detection sensor and a detection algorithm thereof, which comprises a microcontroller module, a magnetic control switch circuit, an ultralow-power consumption realization circuit, a temperature sensor module, an ultrasonic piezoelectric wafer head and an ultrasonic wave transmitting, processing and measuring circuit. After the microcontroller module receives an interrupt wake-up signal of the magnetic control switch circuit, the microcontroller module exits hibernation and controls the ultralow-power consumption circuit to realize conduction power supply. The ultrasonic wave signal transmitting circuit drives the piezoelectric wafer head to send ultrasonic waves to the bolt, the receiving circuit acquires reflected echoes, processes the echoes to extract effective echo envelopes and acquires time-of-flight data. The microcontroller module combines environmental temperature data to perform temperature compensation on the time-of-flight data, calculates a pre-tightening force value, sends the pre-tightening force value by using a wireless transceiving circuit, and then disconnects external device power supply to enter hibernation. The application reduces overall static power consumption, eliminates temperature difference interference and improves measurement precision.

Description

Technical Field

[0001] This invention relates to the field of sensor measurement technology, specifically to a wireless ultrasonic bolt preload detection sensor and its detection algorithm. Background Technology

[0002] Bolts, as fundamental fasteners in mechanical structures, directly affect the operational safety and reliability of the entire equipment due to their preload condition. Currently, ultrasonic testing utilizes the acoustic elastic effect to measure the flight time of ultrasonic waves propagating inside the bolt, thereby calculating the bolt's deformation and preload. This method is widely used because it does not damage the structure being tested and offers high measurement accuracy. However, existing ultrasonic bolt preload testing equipment mostly employs wired connections, which presents challenges in complex industrial environments such as wind turbine hubs, rotating machinery, or areas with limited space, making long-term online monitoring difficult.

[0003] To address the limitations of wired monitoring, integrated wireless ultrasonic testing equipment has gradually emerged in the industry. However, these devices have revealed significant power consumption and accuracy deficiencies in practical applications. On the one hand, the high static current in the signal chain modules such as ultrasonic transmitters, receivers, and analog-to-digital converters during standby leads to high overall power consumption and short battery life, increasing maintenance and battery replacement costs in industrial settings. On the other hand, the propagation speed of ultrasound in metallic media is significantly affected by ambient temperature changes. Existing wireless testing equipment often lacks real-time temperature acquisition and dynamic sound velocity compensation mechanisms for the working environment of the bolts being tested. When temperature fluctuations occur due to day / night cycles or equipment operation, the preload calculated directly using a fixed sound velocity will produce significant errors. Furthermore, in ultrasonic transceiver integrated structures, the high-frequency, high-voltage excitation signal driving the piezoelectric crystal to generate ultrasound can easily cause voltage surges in weak signal receiving circuits. Additionally, strong spatial electromagnetic interference and structural noise in industrial environments make it difficult for the sensor's internal measurement circuitry to accurately extract the effective echo envelope from complex interference, directly reducing the stability and accuracy of time-of-flight measurements. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a wireless ultrasonic bolt preload detection sensor and its detection algorithm, which solves the problems of high static power consumption leading to short battery life, lack of real-time temperature compensation causing measurement errors, and inaccurate effective echo extraction caused by high voltage impact and environmental interference at the transceiver end in existing wireless ultrasonic testing equipment.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a wireless ultrasonic bolt preload detection sensor, comprising: The microcontroller module integrates a wireless transceiver circuit. A magnetically controlled switch circuit is used to output an interrupt wake-up signal to the microcontroller module; The ultra-low power consumption implementation circuit, which is controlled by the microcontroller module, supplies power to the temperature sensor module, ultrasonic signal transmitting circuit, ultrasonic signal receiving circuit and signal processing circuit. The temperature sensor module outputs ambient temperature data to the microcontroller module; The ultrasonic signal transmitting circuit is controlled by the microcontroller module to drive the ultrasonic piezoelectric crystal head to send ultrasonic signals to the bolt. The ultrasonic piezoelectric crystal head receives the echo ultrasonic signal generated on the bolt and converts the echo ultrasonic signal into a weak electrical signal. The ultrasonic signal receiving circuit transmits the weak electrical signal to the signal processing circuit. The signal processing circuit extracts the effective echo envelope and outputs it to the signal measurement circuit. The signal measurement circuit acquires time-of-flight data and sends it to the microcontroller module; The microcontroller module combines the ambient temperature data and the flight time data to calculate and transmit the preload value using the wireless transceiver circuit.

[0006] Preferably, the ultra-low power consumption implementation circuit includes a P-channel metal-oxide-semiconductor field-effect transistor and a bias resistor. The source of the P-channel metal-oxide-semiconductor field-effect transistor is connected to the system battery power supply terminal, and the drain of the P-channel metal-oxide-semiconductor field-effect transistor is connected to the power input terminals of the ultrasonic signal transmitting circuit, the ultrasonic signal receiving circuit, and the temperature sensor module. The gate of the P-channel metal-oxide-semiconductor field-effect transistor is connected to the general-purpose input / output pin of the microcontroller module, and the bias resistor is connected between the source and the gate.

[0007] Preferably, the magnetically controlled switch circuit includes a Hall switch chip, a pull-up resistor, and a RC filter network. The signal output pin of the Hall switch chip is connected to the external interrupt pin of the microcontroller module. The pull-up resistor is connected between the signal output pin and the system constant power network. The filter capacitor in the RC filter network is connected between the signal output pin and the system ground.

[0008] Preferably, the ultrasonic signal transmitting circuit includes a field-effect transistor push-pull drive network and a high-frequency boost transformer. The ultrasonic signal transmitting circuit includes a DC-DC boost power supply and a gate driver chip. The microcontroller module outputs a pulse width modulation signal to the gate driver chip. The gate driver chip receives the pulse width modulation signal and switches the DC-DC boost power supply. The switching DC-DC boost power supply generates a high-frequency high-voltage excitation signal. An impedance matching network is connected between the ultrasonic piezoelectric crystal head and the ultrasonic signal transmitting circuit. The impedance matching network includes an ultrasonic matching inductor and an ultrasonic matching capacitor.

[0009] Preferably, the ultrasonic signal receiving circuit includes a transceiver isolation network composed of anti-parallel limiting diodes, one end of the limiting diodes being connected to the input terminal of the ultrasonic signal receiving circuit, and the other end of the limiting diodes being grounded. The signal processing circuit includes a low-noise amplifier and an active bandpass filter. The input terminal of the low-noise amplifier is connected to the output terminal of the ultrasonic signal receiving circuit, and the output terminal of the low-noise amplifier is connected to the input terminal of the active bandpass filter.

[0010] Preferably, the signal measurement circuit includes a time-to-digital converter chip and a zero-crossing comparator. The input terminal of the zero-crossing comparator is connected to the output terminal of the signal processing circuit, and the output terminal of the zero-crossing comparator is connected to the receiving channel of the time-to-digital converter chip. The microcontroller module sends a trigger pulse to the transmit channel of the time-to-digital converter chip, and the time-to-digital converter chip measures the time interval between the trigger pulse and the digital square wave signal received by the receive channel as the time of flight data.

[0011] Preferably, the temperature sensor module includes an RTD1000 thermistor and a resistance measurement conversion circuit, wherein the RTD1000 thermistor is connected to the input terminal of the resistance measurement conversion circuit, and the output terminal of the resistance measurement conversion circuit is connected to the data input interface of the microcontroller module; The resistance measurement conversion circuit includes a resistance measurement network consisting of a reference resistor and the RTD1000 thermistor.

[0012] Preferably, the wireless transceiver circuit includes a Bluetooth baseband processing unit and an RF transceiver front end, the RF output pin of the microcontroller module is connected to the input terminal of the RF impedance matching network, and the output terminal of the RF impedance matching network is connected to the radio antenna. The radio frequency impedance matching network includes a pi-type filter circuit composed of a radio frequency matching inductor and a radio frequency matching capacitor.

[0013] Preferably, an acoustic coupling layer is filled between the ultrasonic piezoelectric crystal head and the end face of the bolt, and a threaded connecting sleeve or a magnetic base is connected between the housing of the wireless ultrasonic bolt preload detection sensor and the bolt, wherein the threaded connecting sleeve or the magnetic base provides axial contact pressure for the ultrasonic piezoelectric crystal head.

[0014] A second aspect of the present invention provides a detection algorithm for a wireless ultrasonic bolt preload detection sensor, comprising the following steps: The magnetic switch circuit generates the interrupt wake-up signal, and the microcontroller module receives the interrupt wake-up signal and exits the sleep state. The microcontroller module outputs a control signal to the ultra-low power implementation circuit, which in turn turns on and supplies power to the temperature sensor module, the ultrasonic signal transmitting circuit, the ultrasonic signal receiving circuit, and the signal processing circuit. The temperature sensor module acquires and outputs the ambient temperature data to the microcontroller module. The microcontroller module sends an excitation command to the ultrasonic signal transmitting circuit, and the ultrasonic signal transmitting circuit receives the command and drives the ultrasonic piezoelectric crystal head to send the ultrasonic signal to the bolt. The ultrasonic piezoelectric crystal head receives the reflected echo ultrasonic signal, converts the echo ultrasonic signal into the weak electrical signal, and the ultrasonic signal receiving circuit transmits the weak electrical signal to the signal processing circuit. The signal processing circuit filters the weak electrical signal and extracts the effective echo envelope, which is then output to the signal measurement circuit. The signal measurement circuit measures the effective echo envelope to obtain the time-of-flight data, and sends the time-of-flight data to the microcontroller module; The microcontroller module performs temperature compensation on the flight time data based on the ambient temperature data, and calculates the preload force value. The microcontroller module uses the wireless transceiver circuit to transmit the preload value, and then the microcontroller module controls the ultra-low power realization circuit to disconnect the power supply, and the microcontroller module enters a sleep state.

[0015] This invention provides a wireless ultrasonic bolt preload detection sensor and its detection algorithm. It has the following advantages: 1. This invention enables the sensor to have hardware-level power management capabilities by setting up a magnetic control switch circuit and an ultra-low power consumption implementation circuit. The microcontroller module is in a sleep state when not measuring. Only when it receives an interrupt wake-up signal from the magnetic control switch circuit will it control the ultra-low power consumption implementation circuit to conduct and supply power to the peripheral measurement circuit. After the data transmission is completed, the power supply is immediately disconnected. This design cuts off the static current of each peripheral module during idle periods, reduces the overall power consumption of the sensor, and thus extends the battery life of the device.

[0016] 2. This invention introduces a dynamic compensation mechanism based on ambient temperature feedback, which improves the measurement accuracy of preload. The microcontroller module synchronously acquires the ambient temperature data output by the temperature sensor module and the flight time data acquired by the signal measurement circuit. Before calculating the absolute deformation of the bolt, the ambient temperature data is used to perform temperature compensation on the flight time data. This calculation process eliminates the fluctuation error caused by the rise and fall of ultrasonic velocity in metal materials with temperature, and overcomes the interference of ambient temperature difference on the measurement results.

[0017] 3. The signal transceiver front end of the present invention has high anti-interference and self-protection capabilities. The front end of the ultrasonic signal receiving circuit is equipped with a transceiver isolation network composed of anti-parallel limiting diodes. During the transmission stage, it is turned on to isolate the high-frequency high-voltage excitation signal and protect the subsequent measurement devices. At the same time, the received weak electrical signal is amplified and filtered by the signal processing circuit including a low-noise amplifier and an active bandpass filter, which attenuates out-of-band electromagnetic interference and noise, ensuring that the signal measurement circuit can extract an accurate and effective echo envelope. Attached Figure Description

[0018] Figure 1 This is a system architecture diagram of the present invention; Figure 2 This is a flowchart of the method of the present invention; Figure 3 This is a bar chart comparing the system power consumption of the present invention; Figure 4 This is a line graph comparing the measurement errors in the variable temperature environment of the present invention. Figure 5 This is a schematic diagram of the microcontroller module and its peripheral circuits of the present invention. Detailed Implementation

[0019] 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, and 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.

[0020] See attached document Figure 1 and Figure 5 This invention provides a wireless ultrasonic bolt preload detection sensor, which may include: The system includes a microcontroller module, an ultrasonic piezoelectric crystal head, a temperature sensor module, an ultrasonic signal transmitting circuit, an ultrasonic signal receiving circuit, a signal processing circuit, a signal measurement circuit, a magnetic switch circuit, and an ultra-low power consumption implementation circuit.

[0021] The microcontroller module, serving as the main control unit of the wireless ultrasonic bolt preload detection sensor, integrates a wireless transceiver circuit that uses the Bluetooth 5.0 communication protocol for data transmission. The microcontroller module is electrically connected to the temperature sensor module, ultrasonic signal transmitting circuit, signal measurement circuit, magnetic switch circuit, and ultra-low power consumption circuit.

[0022] The ultra-low power implementation circuit uses MOSFETs to control the power output. The microcontroller module manages the power supply status of the ultrasonic signal transmitting circuit, ultrasonic signal receiving circuit, signal processing circuit, and temperature sensor module by controlling the on / off state of the MOSFETs in the ultra-low power implementation circuit. In sleep mode, the microcontroller module outputs a control signal to the ultra-low power implementation circuit to disconnect the power supply lines of the aforementioned peripheral circuits.

[0023] The magnetically controlled switch circuit uses Hall effect sensors to physically acquire and logically output the switching signal. The signal output of the magnetically controlled switch circuit is connected to the external interrupt pin of the microcontroller module. When an external magnet approaches the magnetically controlled switch circuit, the Hall effect sensor outputs a low-level signal; when no magnet is nearby, it outputs a high-level signal. The microcontroller module is configured for falling-edge interrupt wake-up mode, responding to the low-level signal output by the magnetically controlled switch circuit and exiting sleep mode.

[0024] After receiving power, the ultrasonic signal transmitting circuit receives excitation commands from the microcontroller module, generates a high-frequency, high-voltage signal at 4MHz, and drives the ultrasonic piezoelectric crystal head. The ultrasonic piezoelectric crystal head, made of piezoelectric ceramic material, converts the received electrical signal into an ultrasonic signal and transmits it into the bolt. Simultaneously, it receives the echo ultrasonic signal reflected from the bottom surface of the bolt and converts it into a weak electrical signal.

[0025] The ultrasonic signal receiving circuit transmits the weak electrical signal output from the ultrasonic piezoelectric crystal head to the signal processing circuit. The signal processing circuit includes a low-noise amplifier that amplifies and filters the received ultrasonic echo signal to extract the effective echo envelope. The signal measurement circuit uses a high-precision timer to measure the amplified and filtered ultrasonic echo signal, obtaining the time difference between the transmitted and received ultrasonic signals, and sends this time-of-flight data to the microcontroller module.

[0026] The temperature sensor module uses an RTD1000 thermistor. The temperature sensor module converts temperature changes in the bonding surface and bolt environment into changes in resistance. The microcontroller module obtains this resistance value through a measurement circuit and calculates the current ambient temperature data.

[0027] See attached document Figure 2This invention provides a detection algorithm for a wireless ultrasonic bolt preload detection sensor. The overall workflow of this detection algorithm in the time dimension is a periodic state transition based on interrupt triggering or timed triggering.

[0028] In its initial sleep state, the wireless ultrasonic bolt preload sensor is in power-off standby mode. The microcontroller module starts operating upon interruption of the magnetic switch circuit or timing trigger of the internal timer. The microcontroller module first controls the ultra-low power consumption circuit to establish operating voltage for the various measurement units within the sensor.

[0029] After power is established, the microcontroller module reads the ambient temperature data acquired by the temperature sensor module. Simultaneously, it instructs the ultrasonic signal transmitting circuit to send an ultrasonic signal, and the signal measurement circuit measures the flight time of the ultrasonic wave inside the bolt. The microcontroller module acquires the temperature and flight time data, combines them with internally stored reference parameters to run a temperature compensation algorithm, calculates the bolt elongation, and converts it into the preload value.

[0030] The microcontroller module uses its internal wireless transceiver circuitry to transmit the calculated preload value to the external receiving terminal. After the data transmission process is complete, the microcontroller module controls the ultra-low power implementation circuit to cut off the power supply to the peripheral device, shut down the wireless transceiver circuitry, and the microcontroller module itself stops clock calculations and enters a sleep state, waiting for the next trigger signal.

[0031] The wireless ultrasonic bolt preload detection sensor has an internal battery-powered module, which achieves low-power standby and external signal-triggered wake-up through hardware peripheral topology and control logic.

[0032] The specific hardware features of the magnetically controlled switch circuit include a Hall effect switch chip and its surrounding RC filter network. The power supply pin of the Hall effect switch chip is connected to the system's constant power network, and its ground pin is connected to system ground. The signal output pin of the Hall effect switch chip is connected to the external interrupt pin of the microcontroller module. To improve the electromagnetic interference immunity of the signal transmission, a pull-up resistor is connected between the signal output pin and the system's constant power network, and a filter capacitor is connected between the signal output pin and system ground.

[0033] For the selection of Hall switch chip models and the packaging structure of its internal hysteresis comparison circuit, those skilled in the art can make conventional selections based on the actual magnetic field wake-up distance requirements. The internal Hall effect sensing principle is a well-known technology in this field and will not be elaborated here.

[0034] The specific hardware features of the ultra-low power implementation circuit include a P-channel metal-oxide-semiconductor field-effect transistor, or PMOS transistor, which serves as a load switch for global power supply. The source of the PMOS transistor is connected to the system battery power supply, and its drain is connected to the power inputs of the ultrasonic signal transmitting circuit, ultrasonic signal receiving circuit, and temperature sensor module, thus forming a controlled peripheral power supply network. The gate of the PMOS transistor is connected to a general-purpose input / output pin of the microcontroller module. A bias resistor is connected between the source and gate of the PMOS transistor to maintain the gate at its default high level when there is no drive signal, ensuring that the peripheral power supply network is disconnected.

[0035] A filter capacitor connected between the signal output pin of the magnetically controlled switch circuit and system ground is used for hardware debouncing. There is an electrical delay before the microcontroller module receives a hardware interrupt signal; this delay time is specified in the figure. The calculation formula is as follows: ; in: The actual electrical delay time required for the Hall switch chip signal output level to drop to the microcontroller module interrupt trigger threshold; The value of the pull-up resistor connected to the signal output pin; The capacitance value of the filter capacitor connected to the signal output pin; The logic threshold voltage that is identified as low level by the external interrupt pin of the microcontroller module; This is the reference supply voltage for the system's constant power network.

[0036] The system standby and wake-up control process includes the following steps: When the S101 wireless ultrasonic bolt preload sensor is in sleep mode, the microcontroller module configures the general-purpose input / output pin of its control PMOS transistor to a high-impedance state or directly output a high level. The gate-source voltage difference of the PMOS transistor is zero, and the PMOS transistor is in the off state, cutting off the power input to the peripheral power supply network. Simultaneously, the microcontroller module configures the external interrupt pin connected to the Hall switch chip to a falling-edge hardware-triggered mode.

[0037] S102, when the magnetic field strength of the external magnet reaches the action threshold of the Hall switch chip, the open-drain output tube inside the Hall switch chip is turned on, and the level state of its signal output pin is flipped from the high level pulled up by the system to the low level, thereby generating the interrupt wake-up signal.

[0038] S103, the external interrupt pin of the microcontroller module detects the interrupt wake-up signal, i.e., the falling edge of the level. The microcontroller module 10 responds to this signal and triggers an interrupt, switching the microcontroller module from sleep mode to running mode.

[0039] S104, when the microcontroller module is running, controls the corresponding general-purpose input / output pins to output a low level. The gate voltage of the PMOS transistor is pulled low, and the gate-source voltage difference reaches the PMOS transistor's turn-on threshold. The PMOS transistor enters the turn-on state, and the system battery power supply terminal outputs operating voltage to the external power supply network through the source-drain junction, establishing power supply for the ultrasonic signal transmitting circuit, ultrasonic signal receiving circuit, and temperature sensor module.

[0040] The wireless ultrasonic bolt preload detection sensor internally relies on a transceiver signal chain to convert electrical signals into ultrasonic signals and process echo signals.

[0041] The general-purpose input / output pins of the microcontroller module are connected to the input terminals of the ultrasonic signal transmitting circuit. The output terminals of the ultrasonic signal transmitting circuit are connected to the ultrasonic piezoelectric crystal head. The ultrasonic piezoelectric crystal head is also connected to the input terminals of the ultrasonic signal receiving circuit. The output terminals of the ultrasonic signal receiving circuit are connected to the input terminals of the signal processing circuit.

[0042] The ultrasonic signal transmitting circuit includes a DC-DC boost power supply and a gate driver chip. The microcontroller module outputs a pulse width modulation signal to the gate driver chip, and the gate driver chip receives the pulse width modulation signal and switches the DC-DC boost power supply. The switching of the DC-DC boost power supply generates a high-frequency high-voltage excitation signal.

[0043] An impedance matching network is connected between the ultrasonic piezoelectric crystal head and the ultrasonic signal transmitting circuit. This impedance matching network includes an ultrasonic matching inductor and an ultrasonic matching capacitor. The formula for calculating the resonant frequency is as follows: ; in: This is the resonant frequency of the impedance matching network; The inductance value for the ultrasonic matching inductor; This is the sum of the capacitance value of the ultrasonic matching capacitor and the static capacitance value of the ultrasonic piezoelectric crystal head. The microcontroller module is configured to output a signal frequency equal to the resonant frequency of the impedance matching network. ,and Set to 4MHz.

[0044] The ultrasonic signal receiving circuit includes a transceiver isolation network, which consists of anti-parallel limiting diodes. One end of each limiting diode is connected to the input terminal of the ultrasonic signal receiving circuit, and the other end is grounded. During the ultrasonic transmission phase, the high-frequency, high-voltage excitation signal turns on the limiting diodes, short-circuiting the input terminal of the ultrasonic signal receiving circuit to ground, thus preventing high voltage damage to subsequent circuit components.

[0045] During the ultrasonic wave reception phase, the echo signal voltage is lower than the forward voltage drop of the limiting diode, causing the transceiver isolation network to exhibit a high-impedance state, allowing the echo signal to pass through. The signal processing circuit includes a low-noise amplifier and an active bandpass filter. The input of the low-noise amplifier is connected to the output of the ultrasonic signal receiving circuit, and the output of the low-noise amplifier is connected to the input of the active bandpass filter. The center frequency of the active bandpass filter is set to 4MHz.

[0046] The specific composition of the piezoelectric ceramic material used in the ultrasonic piezoelectric crystal head can be conventionally selected by those skilled in the art based on the actual requirements of the sound source emission intensity. The physical mechanisms of the positive and inverse piezoelectric effects within it are well-known technologies in the field and will not be elaborated here.

[0047] The workflow of the ultrasonic transceiver front-end and signal chain circuit includes the following steps: S201, the microcontroller module generates a pulse width modulation signal with a frequency of 4MHz, which is input to the ultrasonic signal transmitting circuit.

[0048] S202, the gate driver chip in the ultrasonic signal transmitting circuit receives the pulse width modulation signal, switches the DC-DC boost power supply, and outputs a high-frequency high-voltage excitation signal to the ultrasonic piezoelectric crystal head.

[0049] S203, the ultrasonic piezoelectric crystal head converts the high-frequency, high-voltage excitation signal into an ultrasonic signal, which is then transmitted to the bolt. During this period, the limiting diode in the ultrasonic signal receiving circuit is turned on, isolating the high-frequency, high-voltage excitation signal.

[0050] S204, the ultrasonic signal is reflected at the bottom of the bolt, forming an echo signal. The ultrasonic piezoelectric crystal head receives the echo signal and converts it into an echo electrical signal. The limiting diode in the ultrasonic signal receiving circuit is turned off, and the echo electrical signal enters the signal processing circuit.

[0051] S205 is a low-noise amplifier in the signal processing circuit that amplifies the echo signal.

[0052] S206, the active bandpass filter in the signal processing circuit filters the amplified echo signal, attenuates environmental electromagnetic interference and structural noise outside the 4MHz frequency band, and outputs the filtered echo signal to the signal measurement circuit.

[0053] The wireless ultrasonic bolt preload detection sensor obtains physical parameters through a time measurement unit and a temperature measurement unit.

[0054] The signal measurement circuit includes a time-to-digital converter (TD-SCDMA) chip and a zero-crossing comparator. The input of the signal measurement circuit is connected to the output of the signal processing circuit. Specifically, the input of the zero-crossing comparator is connected to the output of the signal processing circuit, and the output of the zero-crossing comparator is connected to the receiving channel of the TD-SCDMA chip. The control and data outputs of the signal measurement circuit are connected to a microcontroller module. The filtered echo signal output from the signal processing circuit is converted into a digital square wave signal by the zero-crossing comparator, and this digital square wave signal is input to the receiving channel of the TD-SCDMA chip. When the microcontroller module drives the ultrasonic signal transmitting circuit to send an excitation signal, it synchronously sends a trigger pulse to the transmitting channel of the TD-SCDMA chip. The TD-SCDMA chip measures the time interval between the trigger pulse and the digital square wave signal to obtain the flight time of the ultrasonic wave propagating inside the bolt.

[0055] The temperature sensor module includes an RTD1000 thermistor and a resistance measurement conversion circuit. The RTD1000 thermistor is connected to the input of the resistance measurement conversion circuit, and the output of the resistance measurement conversion circuit is connected to the data input interface of the microcontroller module. The resistance measurement conversion circuit uses a resistance measurement network consisting of a reference resistor and the RTD1000 thermistor to convert the resistance value of the RTD1000 thermistor as it changes with temperature into a voltage signal. The microcontroller module acquires this voltage signal and converts it into the current resistance value.

[0056] The resistance of the RTD1000 thermistor has a linear approximate relationship with temperature; the current ambient temperature... The calculation formula is as follows: ; in: The current ambient temperature; For reference temperature; This is the current resistance value; The nominal resistance value; This refers to the temperature coefficient. The microcontroller module has a pre-stored reference temperature. Nominal resistance and temperature coefficient Substitute the value into the measured current resistance value. The current ambient temperature is calculated. .

[0057] Regarding the specific model selection of the time-to-digital converter chip and the circuit topology of the zero-crossing comparator, those skilled in the art can make conventional selections based on the actual measurement accuracy requirements. The internal gate delay measurement principle is a well-known technology in the field and will not be elaborated here. The sample-and-hold mechanism of the analog-to-digital converter circuit is also a well-known technology in the field and will not be elaborated here.

[0058] The workflow of a high-precision time measurement and temperature sensing circuit includes the following steps: S301, the microcontroller module outputs a pulse width modulation signal, which synchronously sends a trigger pulse to the signal measurement circuit. The time-to-digital converter chip inside the signal measurement circuit receives the trigger pulse and starts its internal high-frequency timer.

[0059] S302, the signal processing circuit outputs an echo signal to the signal measurement circuit, and the zero-crossing comparator converts the echo signal into a digital square wave signal. This digital square wave signal triggers the stop timing channel of the time-to-digital converter chip, and the time-to-digital converter chip stops timing.

[0060] The S303 time-to-digital converter chip calculates the time interval between the start and stop of the timer, uses this time interval as the flight time, and sends it to the microcontroller module via the serial peripheral interface bus.

[0061] After the peripheral power supply network is established, the S304 resistance measurement conversion circuit outputs the corresponding analog voltage signal based on the impedance characteristics of the RTD1000 thermistor.

[0062] The S305 microcontroller module uses a resistance measurement conversion circuit to obtain the digital value of the resistance. The microcontroller module uses the nominal resistance value... Calculate the current resistance value It calculates and records the current ambient temperature by combining internally stored parameters. .

[0063] The wireless ultrasonic bolt preload detection sensor interacts with an external receiving terminal via a Bluetooth wireless radio frequency transceiver module.

[0064] The microcontroller module integrates a wireless transceiver circuit, which includes a Bluetooth baseband processing unit and an RF transceiver front-end. The RF output pin of the microcontroller module is connected to the input of an RF impedance matching network, and the output of the RF impedance matching network is connected to a radio antenna. The radio antenna is either a ceramic antenna or an onboard antenna on a printed circuit board. The clock input pin of the microcontroller module is connected to a quartz crystal oscillator. The quartz crystal oscillator provides a reference frequency clock signal for the Bluetooth baseband processing unit and the RF transceiver front-end.

[0065] The RF impedance matching network employs a Pi-type filter circuit composed of an RF matching inductor and an RF matching capacitor. The RF impedance matching network is used to filter out high-order harmonics at the output of the RF transceiver front-end and transform the output impedance of the microcontroller module's RF output pins into the characteristic impedance of the radio antenna, achieving impedance conjugate matching to improve the transmission power of the RF signal.

[0066] RF resonant frequency of RF impedance matching network The calculation formula is as follows: ; in: It is the radio frequency resonant frequency; The inductance value of the RF matching inductor; This refers to the capacitance value of the RF matching capacitor. The microcontroller module is configured to operate at a frequency equal to the RF resonant frequency of the wireless transceiver circuit. ,and It is set to the 2.4GHz communication frequency band.

[0067] For the specific model selection of quartz crystal oscillators and the microstrip wiring structure of radio antennas, those skilled in the art can make conventional selections based on the actual communication distance requirements. The internal radio frequency modulation and demodulation principles are well-known technologies in the field and will not be elaborated here.

[0068] The data interaction process of the Bluetooth wireless radio frequency transceiver module includes the following steps: S401, the microcontroller module encapsulates the acquired ambient temperature data, flight time data, and calculated preload force value into data frames according to the Bluetooth communication protocol.

[0069] The S402, the Bluetooth baseband processing unit inside the microcontroller module, performs channel coding and error correction on the data frames and outputs the baseband digital signal.

[0070] The S403 microcontroller module's internal RF transceiver front end modulates the baseband digital signal onto the RF carrier, amplifies it, and outputs the RF AC signal through the RF output pin.

[0071] S404, the radio frequency AC signal enters the radio frequency impedance matching network, which performs out-of-band noise filtering and impedance transformation on the radio frequency AC signal, and then transmits the processed radio frequency AC signal to the radio antenna.

[0072] S405, the radio antenna converts the incoming radio frequency AC signal into a spatial electromagnetic wave signal and transmits it to an external receiving terminal.

[0073] When ultrasound propagates within a metallic medium, its propagation speed is affected by the medium's temperature. The microcontroller module obtains the current ambient temperature through a temperature sensor module and performs dynamic sound velocity temperature compensation calculations internally to correct measurement deviations caused by changes in ambient temperature.

[0074] The elastic modulus and density of the carbon steel or alloy steel used in bolts change with fluctuations in ambient temperature. These changes in material physical properties alter the propagation speed of ultrasonic waves within the bolt. Without altering the bolt's mechanical stress state, temperature changes cause variations in the ultrasonic wave's time of flight. The microcontroller module contains a non-volatile memory storing calibration parameters for the corresponding batch of bolt materials. These calibration parameters are values ​​pre-measured and written based on the bolt material's physical properties before shipment.

[0075] The temperature compensation formula for dynamic sound velocity is as follows: ; in: The speed of sound of the ultrasonic wave at the current temperature; The ultrasonic velocity at the calibration temperature; The temperature coefficient of sound speed; The current ambient temperature; For calibration temperature.

[0076] For the specific derivation of the acoustic wave equation for the propagation of ultrasound in a solid medium, those skilled in the art can consult relevant basic acoustic theory literature. The physical law that the sound speed changes approximately linearly with temperature is a well-known technique in this field and will not be elaborated here.

[0077] The temperature compensation calculation process for dynamic sound velocity includes the following steps: S501, the microcontroller module reads the ultrasonic velocity at the calibration temperature from non-volatile memory. Temperature coefficient of sound speed and calibration temperature .

[0078] S502, the microcontroller module acquires the current ambient temperature output by the temperature sensor module. .

[0079] S503, the microcontroller module calculates the current ambient temperature. With the calibration temperature The difference is used to obtain the temperature change.

[0080] S504, microcontroller module 10, based on temperature change and sound velocity temperature coefficient and the speed of sound of ultrasound at the calibration temperature Calculate the ultrasonic velocity at the current temperature according to the above temperature compensation formula. .

[0081] The S505 microcontroller module calculates the ultrasonic velocity at the current temperature. It is written to the internal random access memory for subsequent program calls.

[0082] The microcontroller module obtains the measured flight time through the signal measurement circuit and calculates the absolute deformation of the bolt by combining it with the temperature-compensated sound velocity.

[0083] During tightening, the bolt is subjected to axial tensile force, causing it to elongate. Simultaneously, the change in stress state within the bolt triggers an acoustoelastic effect, resulting in a change in the propagation speed of ultrasonic waves within the bolt as stress increases. The initial flight time is stored in the non-volatile memory within the microcontroller module 10. With the elastic coefficient of bolts .

[0084] The formula for calculating the absolute deformation of a bolt is as follows: ; in: The absolute deformation of the bolt; The speed of sound of the ultrasonic wave at the current temperature; To measure flight time; The initial flight time is the reference time data measured and recorded ultrasonically before the bolt is installed without being stressed. The elastic coefficient of the bolt is a proportionality coefficient obtained through tensile calibration based on the bolt material. The division by 2 in the formula is necessary because the ultrasonic waves propagate back and forth inside the bolt, and the time difference between the round trip needs to be converted into a one-way time for calculation.

[0085] For the specific physical mechanism of the acoustic elasticity effect of ultrasound propagation in a stressed medium, those skilled in the art can consult relevant solid mechanics literature. The law of sound velocity changing with internal stress is well known in the field and will not be elaborated here.

[0086] The computational process for time-of-flight extraction and deformation calculation includes the following steps: The S601 microcontroller module receives the measurement time of flight sent by the signal measurement circuit via the serial peripheral interface bus. .

[0087] S602, the microcontroller module reads the initial flight time from its internal non-volatile memory. With the elastic coefficient of bolts .

[0088] S603, microcontroller module calculates and measures flight time. With initial flight time The difference is used to obtain the change over time.

[0089] S604, the microcontroller module calls the ultrasonic velocity at the current temperature stored in its internal random access memory. .

[0090] The S605 microcontroller module calculates the ultrasonic velocity based on the time change and the current temperature. and the elastic coefficient of bolts Based on the above calculation formula, the absolute deformation of the bolt is calculated. .

[0091] S606, the microcontroller module will calculate the absolute deformation of the bolt. It is temporarily stored in an internal register as the input for subsequent calculation of the preload.

[0092] The wireless ultrasonic bolt preload sensor is in sleep mode when not performing measurement tasks. The microcontroller module integrates a nested vector interrupt controller and a clock management unit. In sleep mode, the clock management unit shuts down its internal high-speed clock source, and the microcontroller module maintains the operation of the nested vector interrupt controller via a low-frequency internal oscillator to reduce system static power consumption.

[0093] A pull-up resistor is connected between the signal output pin and the power supply network inside the magnetically controlled switch circuit. When the Hall effect switch chip inside the magnetically controlled switch circuit is turned on by the internal open-drain output transistor under the action of a magnetic field, its signal output pin outputs a falling edge. This falling edge signal is transmitted to the external interrupt pin of the microcontroller module. The nested vector interrupt controller receives this falling edge signal and triggers an asynchronous hardware interrupt. The clock management unit responds to the interrupt request and starts the high-speed clock source.

[0094] Total delay time from triggering an interrupt to starting the main program execution The calculation formula is as follows: ; in: This represents the total delay time. This is the start-up and settling time of the high-speed clock source; The total number of clock cycles required to exit sleep mode; This is the master clock cycle of the high-speed clock source. The above information is recorded in the non-volatile memory inside the microcontroller module 10. and The parameters.

[0095] For the low-power mode architecture and clock tree configuration principle inside the microcontroller module, those skilled in the art can consult the relevant microcontroller datasheets. Its state saving and recovery mechanism is a well-known technology in the field and will not be described in detail here.

[0096] The workflow of asynchronous interrupts and hardware wake-up includes the following steps: When the S701 microcontroller module is in sleep mode, the clock management unit shuts down the high-speed clock source, and the general-purpose input / output pins of the microcontroller module output a high level, causing the PMOS transistor to be turned off, thus disconnecting the peripheral power supply network.

[0097] In the S702 magnetic control switch circuit, the Hall switch chip inside senses an external magnetic field, causing its internal output transistor to conduct. The level of its signal output pin switches from high level to low level, outputting a falling edge signal.

[0098] The S703 microcontroller module's external interrupt pin captures this falling edge signal, triggering a hardware interrupt from the nested vector interrupt controller, which then controls the clock management unit to start the high-speed clock source.

[0099] S704, oscillation settling time after high-speed clock source Then, the high-speed clock source outputs a stable master clock signal. The microcontroller module executes the interrupt service routine, switching from sleep mode to running mode.

[0100] When the S705 microcontroller module is running, it controls the general-purpose input / output pins to output a low level to turn on the PMOS transistor, establishing a power supply network for the peripheral devices and providing operating voltage for the signal processing circuit, signal measurement circuit, and temperature sensor module.

[0101] The S706 microcontroller module writes control commands to the signal measurement circuit through the serial peripheral interface bus, completes the parameter configuration and reset operations of the internal registers, completes the hardware configuration, and enters the measurement ready state.

[0102] After entering the measurement ready state, the wireless ultrasonic bolt preload detection sensor controls the system average operating current by controlling the switching frequency between the working state and the sleep state.

[0103] The microcontroller module integrates a real-time clock unit. This real-time clock unit is connected to an independent 32.768kHz low-frequency quartz crystal oscillator. After measurement and data transmission are completed, the microcontroller module 10 configures the real-time clock unit as a timed wake-up source, then disconnects the peripheral power supply network and enters a low-power sleep mode. In low-power sleep mode, the main clock source is turned off, but the real-time clock unit continues to run and perform an accumulation count. When the count value reaches a preset matching value in the alarm register, the real-time clock unit sends an interrupt request to the microcontroller module's nested vector interrupt controller, triggering the microcontroller module to exit low-power sleep mode and resume the measurement task.

[0104] System average operating current The calculation formula is as follows: ; in: This represents the system's average operating current. This is the operating current for the wake-up state; The duration of the awakened state; This is the quiescent current in the dormant state; This represents the duration of the sleep state. The non-volatile memory inside the microcontroller module pre-stores the wake-up state operating current. With dormant static current The physical parameters are as follows. The external receiving terminal sends a sampling period command via the Bluetooth wireless RF transceiver module. The microcontroller module parses this command and dynamically configures the alarm register of the real-time clock unit to set the sleep state duration. .

[0105] For the underlying counting logic of the real-time clock unit and the frequency divider circuit design of the low-frequency quartz crystal oscillator, those skilled in the art can refer to the microcontroller hardware manual for conventional configuration. The hardware timing and wake-up mechanisms are well-known technologies in the field and will not be described in detail here.

[0106] The workflow of periodic sampling state transition includes the following steps: The S801 microcontroller module completes the current ultrasonic ranging, temperature acquisition, and preload calculation, and sends the data frames to the external receiving terminal via the Bluetooth wireless RF transceiver module.

[0107] S802, the microcontroller module calculates the sleep state duration required for the next sampling. Duration of the dormant state The value is converted into a corresponding count value and written into the alarm register of the real-time clock unit.

[0108] The S803 microcontroller module controls the general-purpose input / output pins to output a high level, which turns off the PMOS transistor in the peripheral power supply network, cutting off the power supply to the signal processing circuit, signal measurement circuit, and temperature sensor module.

[0109] The S804 microcontroller module is configured with an internal power management controller that cuts off the clock of internal high-speed peripherals and enters a low-power sleep mode. At this time, the microcontroller module's main clock source stops oscillating, and the real-time clock unit continues timing operations based on a low-frequency quartz crystal oscillator.

[0110] S805: When the internal counter value of the real-time clock unit is equal to the counter value in the alarm register, the real-time clock unit triggers a hardware interrupt and generates a timed wake-up interrupt signal.

[0111] The S806 microcontroller module's nested vector interrupt controller responds to a timed wake-up interrupt signal, starting the main clock source. The microcontroller module resumes operation, controlling the general-purpose input / output pins to output a low level to re-enable the PMOS transistors to power peripherals, thus entering the measurement-ready state.

[0112] During installation, the wireless ultrasonic bolt preload sensor forms a physical connection with the bolt's end face. Since ultrasonic signals cannot penetrate the air layer at high frequencies, acoustic coupling is performed between the ultrasonic piezoelectric crystal head inside the sensor and the bolt's end face to allow ultrasonic energy to enter the bolt.

[0113] The bolt end face needs to be mechanically ground to achieve the preset surface roughness. The sensor housing and bolt are mechanically fixed using a threaded sleeve or magnetic base to provide axial contact pressure for the ultrasonic piezoelectric crystal head. When a threaded sleeve is used, it engages with the outer threads of the bolt head; when a magnetic base is used, it adheres to the metal area surrounding the bolt end face. An acoustic coupling layer is filled between the ultrasonic piezoelectric crystal head and the bolt end face. This acoustic coupling layer, made of epoxy resin or high-temperature silicone grease, fills the microscopic gaps in the contact surface and allows air to escape.

[0114] The sound energy transmission coefficient of ultrasound when crossing different media interfaces The calculation formula is as follows: ; in: The sound energy transmission coefficient; The acoustic impedance of the ultrasonic piezoelectric crystal head; The acoustic impedance of the bolt material. To improve... The acoustic impedance value of the selected acoustic coupling layer is configured to be between and between.

[0115] For bolt end face grinding process and mechanical housing structural design, those skilled in the art can make conventional selections based on the on-site installation space. The surface processing methods and anti-loosening principles are well-known technologies in this field and will not be elaborated here.

[0116] The process for handling the interface between mechanical connection and acoustic coupling includes the following steps: S901, use a grinding tool to mill and polish the bolt end face to remove the oxide layer and rust, exposing the metal base.

[0117] S902 uses anhydrous ethanol to clean the metal substrate, removing surface oil and metal dust, and keeping the substrate dry.

[0118] S903. Apply the acoustic coupling layer material at the center of the bolt end face, and the coating range covers the effective radiation surface of the ultrasonic piezoelectric crystal head.

[0119] S904. Fit the ultrasonic piezoelectric crystal head of the sensor onto the area coated with the acoustic coupling layer material, and apply axial pressure to squeeze out the bubbles inside the interface.

[0120] S905. Install the peripheral threaded connection sleeve or magnetic absorption base, lock the sensor housing onto the bolt, and maintain the contact pressure.

[0121] After the sensor completes mechanical connection and acoustic coupling, it enters the on-site initialization calibration stage. When the bolt is in a zero-stress state without applying the tightening torque, the microcontroller module obtains the reference parameters in this state.

[0122] The external receiving terminal sends an initialization instruction to the microcontroller module through the Bluetooth wireless radio frequency transceiver module. After receiving this instruction, the microcontroller module controls the signal processing circuit and the signal measurement circuit to perform ultrasonic transceiver operations. The microcontroller module is internally integrated with an analog-to-digital converter, which discretely samples the analog echo signal through this analog-to-digital converter and evaluates the quality of the echo signal.

[0123] The signal-to-noise ratio of the echo signal The calculation formula is as follows: ; Where: is the signal-to-noise ratio; is the peak voltage of the echo; is the background noise voltage. The microcontroller module judges whether the calculated is greater than the signal-to-noise ratio threshold pre-stored in the internal non-volatile memory. When is greater than the signal-to-noise ratio threshold, it is determined that the acoustic coupling state is qualified. The microcontroller module writes the flight time measured this time as the initial flight time into the internal non-volatile memory.

[0124] Regarding the parsing protocol of the Bluetooth communication instruction and the data sampling principle of the analog-to-digital converter, those skilled in the art can consult the relevant communication standards and the microcontroller hardware manual. Their data encoding and decoding and digital signal processing methods belong to the well-known technologies in this field and will not be elaborated here.

[0125] The process of on-site initialization calibration and commissioning test includes the following steps: S1001. The external receiving terminal establishes a wireless communication connection with the Bluetooth wireless radio frequency transceiver module and issues an initialization instruction.

[0126] S1002, the microcontroller module parses the initialization instructions, controls the ultrasonic signal transmitting circuit to drive the ultrasonic piezoelectric crystal head to emit ultrasonic waves and receive echo signals, and the analog-to-digital converter samples the echo signals to obtain digital sequences.

[0127] S1003, Microcontroller module for traversing and extracting digital sequences Extracting the echo-free time window between the transmitted pulse and the arrival of the first echo. .

[0128] S1004, the microcontroller module calculates according to the above calculation formula. The calculation results are then compared with the signal-to-noise ratio thresholds pre-stored in the internal non-volatile memory.

[0129] S1005, if If the signal-to-noise ratio is less than or equal to the threshold, the microcontroller module returns an installation abnormality alarm data packet to the external receiving terminal via the Bluetooth wireless RF transceiver module, prompting the operator to reapply the acoustic coupling layer.

[0130] S1006, if If the signal-to-noise ratio is greater than the threshold, the microcontroller module stores the currently measured flight time as the initial flight time. It then returns a calibration success data packet to the external receiving terminal.

[0131] S1007, the microcontroller module controls the general-purpose input / output pins to output a high level, which turns off the PMOS transistor in the peripheral power supply network, cuts off the power supply, configures the relevant internal registers to enter a low-power sleep mode, and waits for the active measurement command from the external receiving terminal or the periodic wake-up timer.

[0132] Specific application examples: This embodiment is applied to the monitoring of the preload of M36 high-strength carbon steel bolts at the flange connection of a wind turbine tower. The bolt material is 42CrMo, and the ultrasonic velocity at the calibration temperature of 25°C is... The speed is 5920 m / s, and the temperature coefficient of sound velocity is... It is 0.00015 / ℃.

[0133] During installation, the M36 bolt end face is sanded smooth and cleaned of oil. Epoxy resin is applied to the center of the bolt end face as an acoustic coupling layer. The wireless ultrasonic bolt preload sensor is then attached to the bolt end face and adsorbed onto the bolt flange surface via its built-in magnetic base, providing axial contact pressure to the ultrasonic piezoelectric crystal head.

[0134] After installation, without applying any tightening torque to the bolts, the external receiving terminal sends an initialization command via Bluetooth. Upon receiving the command, the microcontroller module initiates an ultrasonic transceiver test. The analog-to-digital converter samples and calculates the signal-to-noise ratio of the echo signal, which is 32dB, exceeding the system's preset 25dB threshold, thus determining that the acoustic coupling is qualified. The microcontroller module uses the flight time measured at this point as the initial flight time. Store in non-volatile memory.

[0135] During routine operation and monitoring, the external receiving terminal sends a periodic configuration command, setting the system to perform a measurement every 4 hours. The microcontroller module writes this periodic parameter into its internal real-time clock unit and enters sleep mode. During sleep mode, the microcontroller module keeps the general-purpose input / output pins at a high level, the PMOS transistor is turned off, and the power supply to the temperature sensor module, ultrasonic signal transmitting circuit, and receiving circuit is cut off.

[0136] When the 4-hour timer expires, the real-time clock unit triggers a hardware interrupt to wake up the microcontroller module. The microcontroller module outputs a low-level signal to turn on the PMOS transistor, supplying power to the peripheral circuits. The RTD1000 thermistor in the temperature sensor module senses the current ambient temperature as -5℃. The microcontroller module reads this temperature data and calculates the ultrasonic velocity at the current temperature using a formula. The speed is 5946.6 m / s. Simultaneously, the signal measurement circuit, in conjunction with a time-to-digital converter chip, acquires the measured flight time of the ultrasonic wave propagating inside the bolt under the current tensile state. Microcontroller module combined , , The absolute deformation is calculated using the material's acoustic elasticity coefficient, further converted into the current preload value, and then transmitted to an external receiving terminal via a Bluetooth transceiver module. After data transmission is complete, the microcontroller module controls the PMOS transistor to disconnect the power supply and re-enter sleep mode.

[0137] Experimental verification and effect comparison: To verify the technical effect of the present invention, M36 bolts of the same specification and testing equipment were selected. The sensor of the present invention was compared with existing conventional wireless ultrasonic sensors that do not have power management and temperature compensation mechanisms in terms of system power consumption and preload measurement accuracy.

[0138] System power consumption and battery life comparison test: The test conditions were set such that the measurement and transmission cycles for both sets of devices were 4 hours each, and the ambient temperature was maintained at 25℃. A digital source meter (Keithley 2450) was used to record the current consumption during a single complete operating cycle, and a 2000mAh lithium battery was used as the benchmark for battery life evaluation. The comparative test data for system power consumption and battery life are shown in Table 1.

[0139] Table 1 Comparison of System Power Consumption and Battery Life ;in conclusion: Existing conventional wireless ultrasonic sensors maintain power to their peripheral signal transceiver circuits during non-measurement periods, resulting in significant quiescent current. This invention, however, disconnects the peripheral power supply network via a PMOS transistor during non-measurement periods, allowing only the low-frequency real-time clock unit within the microcontroller module to operate. This reduces the system's average operating current and extends the device's theoretical battery life. Combined with… Figure 3 The system power consumption comparison bar chart shows that, under the test conditions of a 4-hour wake-up cycle, the average operating current of existing conventional sensors corresponds to a bar height of 12.5 mA, while the average operating current of the sensor of this invention corresponds to a bar height of only 0.0202 mA (i.e., 20.2 μA). This bar chart visually demonstrates the significant decrease in average system current after the invention disconnects the power supply to idle peripherals through hardware power management logic.

[0140] Preload measurement error test under variable temperature environment: The M36 bolt under test was mounted on a tensile testing machine, and a constant axial tensile load of 800 kN was applied and maintained. The entire setup was placed in a high-low temperature alternating test chamber, with the temperature set from -10℃ to 50℃ in 10℃ increments. Each temperature point was held for 2 hours to ensure uniform internal temperature of the bolt, and then the preload values ​​output by the two sets of equipment were recorded. The comparison data of measurement errors under varying temperature conditions are shown in Table 2.

[0141] Table 2 Comparison of Preload Measurement Errors in Variable Temperature Environments (Actual Tensile Load: 800kN) ;in conclusion: The actual sound velocity of ultrasound within a metallic medium decreases as ambient temperature increases, leading to an increase in flight time. Existing conventional equipment uses a constant calibrated sound velocity to calculate deformation, interpreting the temperature-induced increase in flight time as bolt elongation; however, its output error increases with temperature deviation. This invention's sensor acquires ambient temperature data at different temperature points and performs sound velocity compensation calculations, controlling the relative error of preload measurement under various temperature conditions within ±1.0%, thus correcting the acoustic measurement deviation caused by ambient temperature differences. Combined with… Figure 4The line graph comparing measurement errors in varying temperature environments shows that, within the ambient temperature range of -10℃ to 50℃ on the horizontal axis, the relative error curve of existing conventional sensors exhibits a clear upward sloping trend, with the error value continuously deviating from -3.5% to the positive direction, reaching a maximum of 8.1%. In contrast, the relative error curve of the sensor of this invention remains consistently stable, fluctuating within a very small range (-0.6% to +0.8%) near the 0% baseline on the vertical axis. The difference in the trends of the two lines verifies that the dynamic sound velocity compensation calculation of this invention can effectively eliminate the interference caused by ambient temperature differences on the preload measurement results.

Claims

1. A wireless ultrasonic bolt preload detection sensor, characterized in that, include: The microcontroller module integrates a wireless transceiver circuit. A magnetically controlled switch circuit is used to output an interrupt wake-up signal to the microcontroller module; The ultra-low power consumption implementation circuit, which is controlled by the microcontroller module, supplies power to the temperature sensor module, ultrasonic signal transmitting circuit, ultrasonic signal receiving circuit and signal processing circuit. The temperature sensor module outputs ambient temperature data to the microcontroller module; The ultrasonic signal transmitting circuit is controlled by the microcontroller module to drive the ultrasonic piezoelectric crystal head to send ultrasonic signals to the bolt. The ultrasonic piezoelectric crystal head receives the echo ultrasonic signal generated on the bolt and converts the echo ultrasonic signal into a weak electrical signal. The ultrasonic signal receiving circuit transmits the weak electrical signal to the signal processing circuit. The signal processing circuit extracts the effective echo envelope and outputs it to the signal measurement circuit. The signal measurement circuit acquires time-of-flight data and sends it to the microcontroller module; The microcontroller module combines the ambient temperature data and the flight time data to calculate and transmit the preload value using the wireless transceiver circuit.

2. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The ultra-low power consumption implementation circuit includes a P-channel metal-oxide-semiconductor field-effect transistor and a bias resistor. The source of the P-channel metal-oxide-semiconductor field-effect transistor is connected to the system battery power supply terminal, and the drain of the P-channel metal-oxide-semiconductor field-effect transistor is connected to the power input terminals of the ultrasonic signal transmitting circuit, the ultrasonic signal receiving circuit, and the temperature sensor module. The gate of the P-channel metal-oxide-semiconductor field-effect transistor is connected to the general-purpose input / output pin of the microcontroller module, and the bias resistor is connected between the source and the gate.

3. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The magnetically controlled switch circuit includes a Hall switch chip, a pull-up resistor, and a RC filter network. The signal output pin of the Hall switch chip is connected to the external interrupt pin of the microcontroller module. The pull-up resistor is connected between the signal output pin and the system constant power network. The filter capacitor in the RC filter network is connected between the signal output pin and the system ground.

4. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The ultrasonic signal transmitting circuit includes a DC-DC boost power supply and a gate driver chip. The microcontroller module outputs a pulse width modulation signal to the gate driver chip. The gate driver chip receives the pulse width modulation signal and switches the DC-DC boost power supply. The switching of the DC-DC boost power supply generates a high-frequency high-voltage excitation signal. An impedance matching network is connected between the ultrasonic piezoelectric crystal head and the ultrasonic signal transmitting circuit. The impedance matching network includes an ultrasonic matching inductor and an ultrasonic matching capacitor.

5. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The ultrasonic signal receiving circuit includes a transceiver isolation network composed of anti-parallel limiting diodes. One end of the limiting diode is connected to the input terminal of the ultrasonic signal receiving circuit, and the other end of the limiting diode is grounded. The signal processing circuit includes a low-noise amplifier and an active bandpass filter. The input terminal of the low-noise amplifier is connected to the output terminal of the ultrasonic signal receiving circuit, and the output terminal of the low-noise amplifier is connected to the input terminal of the active bandpass filter.

6. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The signal measurement circuit includes a time-to-digital converter chip and a zero-crossing comparator. The input terminal of the zero-crossing comparator is connected to the output terminal of the signal processing circuit, and the output terminal of the zero-crossing comparator is connected to the receiving channel of the time-to-digital converter chip. The microcontroller module sends a trigger pulse to the transmit channel of the time-to-digital converter chip, and the time-to-digital converter chip measures the time interval between the trigger pulse and the digital square wave signal received by the receive channel as the time of flight data.

7. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The temperature sensor module includes an RTD1000 thermistor and a resistance measurement conversion circuit. The RTD1000 thermistor is connected to the input terminal of the resistance measurement conversion circuit, and the output terminal of the resistance measurement conversion circuit is connected to the data input interface of the microcontroller module. The resistance measurement conversion circuit includes a resistance measurement network consisting of a reference resistor and the RTD1000 thermistor.

8. The wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, The wireless transceiver circuit includes a Bluetooth baseband processing unit and an RF transceiver front end. The RF output pin of the microcontroller module is connected to the input of the RF impedance matching network, and the output of the RF impedance matching network is connected to the radio antenna. The radio frequency impedance matching network includes a pi-type filter circuit composed of a radio frequency matching inductor and a radio frequency matching capacitor.

9. A wireless ultrasonic bolt preload detection sensor according to claim 1, characterized in that, An acoustic coupling layer is filled between the ultrasonic piezoelectric crystal head and the end face of the bolt. A threaded connecting sleeve or a magnetic base is connected between the housing of the wireless ultrasonic bolt preload detection sensor and the bolt. The threaded connecting sleeve or the magnetic base provides axial contact pressure for the ultrasonic piezoelectric crystal head.

10. A detection algorithm for a wireless ultrasonic bolt preload detection sensor, applied to the wireless ultrasonic bolt preload detection sensor according to any one of claims 1-9, characterized in that, Includes the following steps: The magnetic switch circuit generates the interrupt wake-up signal, and the microcontroller module receives the interrupt wake-up signal and exits the sleep state. The microcontroller module outputs a control signal to the ultra-low power implementation circuit, which in turn turns on and supplies power to the temperature sensor module, the ultrasonic signal transmitting circuit, the ultrasonic signal receiving circuit, and the signal processing circuit. The temperature sensor module acquires and outputs the ambient temperature data to the microcontroller module. The microcontroller module sends an excitation command to the ultrasonic signal transmitting circuit, and the ultrasonic signal transmitting circuit receives the command and drives the ultrasonic piezoelectric crystal head to send the ultrasonic signal to the bolt. The ultrasonic piezoelectric crystal head receives the reflected echo ultrasonic signal, converts the echo ultrasonic signal into the weak electrical signal, and the ultrasonic signal receiving circuit transmits the weak electrical signal to the signal processing circuit. The signal processing circuit filters the weak electrical signal and extracts the effective echo envelope, which is then output to the signal measurement circuit. The signal measurement circuit measures the effective echo envelope to obtain the time-of-flight data, and sends the time-of-flight data to the microcontroller module; The microcontroller module performs temperature compensation on the flight time data based on the ambient temperature data, and calculates the preload force value. The microcontroller module uses the wireless transceiver circuit to transmit the preload value, and then the microcontroller module controls the ultra-low power implementation circuit to disconnect the power supply, so that the microcontroller module enters a sleep state.

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