Helicopter coaxial blade approaching monitoring device and monitoring method

Abstract

The invention relates to the technical field of distance measurement of coaxial blades of helicopters, and particularly discloses a proximity monitoring device and method for coaxial blades of helicopters, and the method comprises the following steps: installing a transmitting module and a receiving module on a blade; the transmitting module is arranged at a lower paddle, and all directions of the electromagnetic intensity of the antenna are kept consistent; the receiving module is arranged at the upper paddle, and all directions of the electromagnetic intensity of the antenna are kept consistent; the transmitting module transmits stable signals and the receiving module receives the signals, if the distance between the transmitting module and the receiving module is long, the received signals are weak, and if the distance between the transmitting module and the receiving module is short, the received signals are strong; and the distance between the upper paddle and the lower paddle is identified according to the strength of the received signal. The interference of the sun on the distance measurement by the optical principle in the high altitude is avoided, the reflection interference of the machine body caused by radar distance measurement can be avoided, the structure is simple and reliable, and a complex signal processing unit is not needed.

Description

Technical Field

[0001] The invention relates to the technical field of helicopter coaxial blade ranging, and in particular to a helicopter coaxial blade approach monitoring device and a monitoring method. Background Art

[0002] At present, when a coaxial twin-rotor helicopter performs high-speed maneuvers during flight, there is a risk of collision between the upper and lower blades. It is necessary to measure the distance between the upper and lower blades in real time and send an alarm to the flight control system when the dangerous distance is approaching. After receiving the alarm information, the flight control system will make timely adjustments to avoid collision between the upper and lower blades and prevent serious safety accidents. This device is crucial to the flight safety of coaxial bi-rotor helicopters.

[0003] In the prior art, laser ranging and millimeter-wave radar are often used to measure the distance between the upper and lower blades. Laser ranging has good accuracy. The laser transmitter emits laser, the laser reaches the blade and is reflected back to the receiver, and the round-trip time is calculated. Millimeter-wave radar uses linear frequency modulation radar ranging. A signal reflector is installed on the upper (or lower) blade facing the radar antenna, and a radar transceiver antenna is installed on the lower (or upper) blade. The radar transmits and receives echo signals, and the path distance is calculated after correlation processing.

[0004] However, in the prior art, due to the interference of the sun, the ranging data becomes very unreliable. At the same time, the blades vibrate when rotating at high speed, resulting in unstable signals and frequent false alarms. Summary of the invention

[0005] The purpose of the present invention is to provide a helicopter coaxial blade proximity monitoring device and monitoring method, aiming to solve the technical problems in the prior art that due to the interference of the sun, the ranging data becomes very unreliable, and the blades vibrate when rotating at high speed, resulting in unstable signals and frequent false alarms.

[0006] To achieve the above object, a helicopter coaxial blade approach monitoring method adopted by the present invention comprises the following steps:

[0007] Install the transmitting module and the receiving module onto the propeller blades;

[0008] The transmitting module is placed at the lower blade, and the electromagnetic antenna adopts an omnidirectional design to ensure that the antenna magnetic strength remains consistent in all directions when the blade is operated at a variable inclination angle;

[0009] The receiving module is placed on the upper blade, and the electromagnetic antenna adopts an omnidirectional design to ensure that the antenna magnetic strength remains consistent in all directions when the blade is operated at a variable inclination angle;

[0010] The transmitting module transmits a stable signal and the receiving module receives the signal. If the distance between the transmitting module and the receiving module is far, the received signal is weak, and if the distance between the transmitting module and the receiving module is close, the received signal is strong.

[0011] The distance between the upper blade and the lower blade is identified by the strength of the received signal.

[0012] Wherein, the transmitting module includes an oscillator, an isolation amplifier, a processor, a transmitting interface circuit, a power conversion circuit and an electromagnetic antenna;

[0013] The processor controls the oscillator to generate a 36KHz oscillation signal, which is amplified by the isolation amplifier and output to the electromagnetic antenna, wherein a portion of the signal is coupled to the detection output to the processor for transmission power detection, and the transmission interface circuit outputs an analog differential as a transmission power level indication, which is a constant differential value when the power is constant, and the power conversion circuit converts a single power supply into a differential power supply required by the isolation amplifier analog circuit.

[0014] Wherein, the receiving module includes an electromagnetic receiving antenna, a receiving amplifier, an AD sampling module, an MCU, a DA module, a receiving interface circuit, an analog conversion circuit and a power supply circuit;

[0015] The electromagnetic receiving antenna receives the electromagnetic signal emitted by the transmitting module, converts it into an electrical signal and sends it to the receiving amplifier for 16-bit AD sampling. According to the maximum rotation speed of the blades, the blade interleaving time is calculated to be 0.8ms. A group of numbers are sampled at 0.05ms and the maximum value is taken to obtain 16 maximum values. The average of every 4 maximum values ​​is then taken to improve the detection accuracy. During the intersection period, 4 maximum average values ​​are obtained, and a maximum value is intercepted every 10ms. The corresponding pitch value is obtained by looking up the table, and then the corresponding analog voltage value is converted into an output through the DA module. The whole process is controlled by the MCU.

[0016] Among them, the RS422 interface of the receiving interface circuit is a digital reporting interface.

[0017] Among them, the AD full scale of the AD sampling module is 4096mv. After removing one sign bit of the 16-bit AD, it is calculated as 15, LSB = 125uV. Due to the nonlinearity of the coupling strength of the far and near signals, the distance accuracy of each distance segment is calculated as follows:

[0018] At a distance between 100mm and 110mm, the AD sampling resolution is:

[0019] (1321.59-1025.88) / (110-100)=29.571mv / mm=29571μv / mm, 1LSB is converted to a distance resolution of 125 / 29571=0.004mm;

[0020] At a distance between 500mm and 510mm, the AD sampling resolution is:

[0021] (28.26-26.67) / (500-490)=0.159mv / mm=159μv / mm, 1LSB is converted to a distance resolution of 125 / 159=0.79mm;

[0022] At distances between 1100mm and 1200mm, the AD sampling resolution is:

[0023] (10.5-7.10) / (1200-1100)=0.034mv / mm=34μv / mm, 1LSB is converted to a distance resolution of 125 / 34=3.68mm.

[0024] Wherein, the receiving module includes a boot program, a ranging program, a debugging program and a peripheral driver;

[0025] The boot program is a bare metal program, and its main functions are to initialize board-level peripherals, update and burn firmware, and provide a menu to select to execute a ranging program or a debugging program;

[0026] The main function of the distance measurement program is to call the distance-voltage lookup table from the Flash memory, execute the distance measurement algorithm, drive the A / D and D / A chips to work, and report the distance data to the upper computer through the RS422 serial port;

[0027] The debugging program runs RTOS and provides a simple terminal interactive interface. Its main functions are to read and write distance voltage lookup tables, monitor the working conditions of the underlying hardware, and read and write debugging functions of electronic tags;

[0028] The peripheral driver provides a data interaction interface between software and hardware for the upper layer module.

[0029] The workflow of the receiving module includes the following steps:

[0030] After the interface module is powered on, the boot program is executed first. During this stage, the countdown is 10 seconds. Within 10 seconds, you can manually choose to burn firmware, execute the distance measurement program, or execute the debugging program in the serial terminal interface. After the countdown ends, the distance measurement program will be automatically run.

[0031] The firmware burning is realized through the Y-Modem protocol. The host terminal sends the binary file of the firmware through the Y-Modem protocol. The module receives the file and automatically burns it into the internal memory. After the burning is completed, the ranging program is automatically executed;

[0032] The distance measurement program is a bare metal program driven by a timer interrupt event. Before the module is powered off, it will continuously report distance data at a frequency of 10ms.

[0033] The debugging program is a tool set used by the maintenance module, which interacts with the user through a terminal interface. Due to its sensitivity, password verification is required to run the debugging program;

[0034] After entering the distance measurement program, configure the SDI pin of the AD chip ZJC2001 to a high level, pull up the CONV pin to enter the 3-wire serial mode, and there is no busy indication. The software performs a sample at a minimum sampling interval of 2us. The current sample is compared with the previous sample value, the larger value is retained, and the smaller value is discarded. The maximum value is recorded every 50us, and is reserved for subsequent maximum value average processing;

[0035] When starting the conversion, first pull up the CONV pin, wait for the maximum conversion time of 1.6us, then pull down the CONV signal to read the conversion result. The conversion result is read on the rising edge of the serial clock SCK, and the minimum reading clock cycle is 15ns. After all 16BIT data are read, the SDO signal enters a high impedance state and waits for the next conversion to start;

[0036] The analog-to-digital chip ZJC2001 is driven by the A / D data reading module, the sampling voltage result is read once every 2us and the result is transmitted to the voltage maximum value finding module;

[0037] The voltage maximum value finding module records the maximum value of the sampled voltage within 12.5ms and transmits the result to the voltage-distance lookup table module;

[0038] The voltage-distance lookup table module maps the voltage value to the distance value through the built-in voltage-distance lookup table;

[0039] The maximum value generated by the voltage-distance lookup table module is transmitted through the serial port at a period of 12.5 ms;

[0040] Finally, the D / A voltage generation module converts the distance value into analog output by configuring an off-chip DA chip.

[0041] The present invention also provides a helicopter coaxial blade proximity monitoring device, comprising a magnetic bar, a bracket, a shell, a cover plate and a PCB board, wherein the number of the brackets is two groups, the two groups of brackets are respectively fixedly connected to the shell and are respectively located on one side of the shell, the two ends of the magnetic bar are respectively fixedly connected to the corresponding brackets and are located between the two groups of brackets, the PCB board is embedded in the interior of the shell, and the cover plate covers the shell and is located on one side of the shell.

[0042] Wherein, the PCB board is any one of a transmitting module circuit board or a receiving module circuit board.

[0043] The beneficial effects of the helicopter coaxial blade proximity monitoring device and monitoring method of the present invention are as follows: the present invention adopts the transmitting module to transmit signals, the receiving module to receive signals, and judges the distance between the transmitting module and the receiving module according to the strength of the received signal, thereby realizing the measurement of the distance between the upper blade and the lower blade, avoiding the interference caused by the high-altitude sun, and at the same time avoiding the reflection interference of the body, and can efficiently and stably monitor the distance between the upper blade and the lower blade in real time, with a simple and reliable structure and no need for a complex signal processing unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 It is the principle diagram of magnetic coupling ranging of the present invention.

[0046] Figure 2 It is a system diagram of the transmitting module of the present invention.

[0047] Figure 3 It is a system diagram of the receiving module of the present invention.

[0048] Figure 4 It is a circuit diagram of the receiving module of the present invention.

[0049] Figure 5 It is an AD circuit diagram of the receiving module of the present invention.

[0050] Figure 6 It is a 4.096V voltage reference circuit diagram of the receiving module of the present invention.

[0051] Figure 7 It is a DA circuit diagram of the receiving module of the present invention.

[0052] Figure 8 It is a power circuit diagram of the receiving module of the present invention.

[0053] Fig. 9 It is a microprocessor circuit diagram of the receiving module of the present invention.

[0054] Fig.10 The present invention Figure 5 A zone amplification circuit diagram.

[0055] Fig.11 The present invention Figure 5 B area amplifier circuit diagram.

[0056] Fig.12 The present invention Figure 5 C area amplification circuit diagram.

[0057] Fig.13 It is a circuit diagram of the transmitting module of the present invention.

[0058] Fig.14 It is a 36KHz sinusoidal wave oscillation circuit diagram of the transmitting module of the present invention.

[0059] Fig.15 It is a power supply circuit diagram of the transmitting module of the present invention.

[0060] Fig.16 It is a program operation principle diagram of the receiving module of the present invention.

[0061] Fig.17 It is a conversion timing diagram of the analog-to-digital chip ZJC2001 of the present invention.

[0062] Fig.18 The present invention is a schematic structural diagram of a helicopter coaxial blade proximity monitoring device.

[0063] 1-magnetic bar, 2-bracket, 3-shell, 4-cover plate, 5-PCB board. DETAILED DESCRIPTION

[0064] See also Figures 1 to 17 The present invention provides a helicopter coaxial blade approach monitoring method, comprising the following steps:

[0065] Install the transmitting module and the receiving module onto the propeller blades;

[0066] The transmitting module is placed at the lower blade, and the electromagnetic antenna adopts an omnidirectional design to ensure that the antenna magnetic strength remains consistent in all directions when the blade is operated at a variable inclination angle;

[0067] The receiving module is placed on the upper blade, and the electromagnetic antenna adopts an omnidirectional design to ensure that the antenna magnetic strength remains consistent in all directions when the blade is operated at a variable inclination angle;

[0068] The transmitting module transmits a stable signal and the receiving module receives the signal. If the distance between the transmitting module and the receiving module is far, the received signal is weak, and if the distance between the transmitting module and the receiving module is close, the received signal is strong.

[0069] The distance between the upper blade and the lower blade is identified by the strength of the received signal.

[0070] Further, the transmitting module includes an oscillator, an isolation amplifier, a processor, a transmitting interface circuit, a power conversion circuit and an electromagnetic antenna;

[0071] The processor controls the oscillator to generate a 36KHz oscillation signal, which is amplified by the isolation amplifier and output to the electromagnetic antenna, wherein a portion of the signal is coupled to the detection output to the processor for transmission power detection, and the transmission interface circuit outputs an analog differential as a transmission power level indication, which is a constant differential value when the power is constant, and the power conversion circuit converts a single power supply into a differential power supply required by the isolation amplifier analog circuit.

[0072] Furthermore, the receiving module includes an electromagnetic receiving antenna, a receiving amplifier, an AD sampling module, an MCU, a DA module, a receiving interface circuit, an analog conversion circuit and a power supply circuit;

[0073] The electromagnetic receiving antenna receives the electromagnetic signal emitted by the transmitting module, converts it into an electrical signal and sends it to the receiving amplifier for 16-bit AD sampling. According to the maximum rotation speed of the blades, the blade interleaving time is calculated to be 0.8ms. A group of numbers are sampled at 0.05ms and the maximum value is taken to obtain 16 maximum values. The average of every 4 maximum values ​​is then taken to improve the detection accuracy. During the intersection period, 4 maximum average values ​​are obtained, and a maximum value is intercepted every 10ms. The corresponding pitch value is obtained by looking up the table, and then the corresponding analog voltage value is converted into an output through the DA module. The whole process is controlled by the MCU.

[0074] Furthermore, the RS422 interface of the receiving interface circuit is a digital reporting interface.

[0075] Furthermore, the AD full scale of the AD sampling module is 4096mv. After removing one sign bit from the 16-bit AD, it is calculated as 15, LSB = 125uV. Due to the nonlinearity of the coupling strength of the far and near signals, the distance accuracy of each distance segment is calculated as follows:

[0076] At a distance between 100mm and 110mm, the AD sampling resolution is:

[0077] (1321.59-1025.88) / (110-100)=29.571mv / mm=29571μv / mm, 1LSB is converted to a distance resolution of 125 / 29571=0.004mm;

[0078] At a distance between 500mm and 510mm, the AD sampling resolution is:

[0079] (28.26-26.67) / (500-490)=0.159mv / mm=159μv / mm, 1LSB is converted to a distance resolution of 125 / 159=0.79mm;

[0080] At distances between 1100mm and 1200mm, the AD sampling resolution is:

[0081] (10.5-7.10) / (1200-1100)=0.034mv / mm=34μv / mm, 1LSB is converted to a distance resolution of 125 / 34=3.68mm.

[0082] Furthermore, the receiving module includes a boot program, a ranging program, a debugging program and a peripheral driver;

[0083] The boot program is a bare metal program, and its main functions are to initialize board-level peripherals, update and burn firmware, and provide a menu to select to execute a ranging program or a debugging program;

[0084] The main function of the distance measurement program is to call the distance-voltage lookup table from the Flash memory, execute the distance measurement algorithm, drive the A / D and D / A chips to work, and report the distance data to the upper computer through the RS422 serial port;

[0085] The debugging program runs RTOS and provides a simple terminal interactive interface. Its main functions are to read and write distance voltage lookup tables, monitor the working conditions of the underlying hardware, and read and write debugging functions of electronic tags;

[0086] The peripheral driver provides a data interaction interface between software and hardware for the upper layer module.

[0087] Furthermore, the workflow of the receiving module includes the following steps:

[0088] After the interface module is powered on, the boot program is executed first. During this stage, the countdown is 10 seconds. Within 10 seconds, you can manually choose to burn firmware, execute the distance measurement program, or execute the debugging program in the serial terminal interface. After the countdown ends, the distance measurement program will be automatically run.

[0089] The firmware burning is realized through the Y-Modem protocol. The host terminal sends the binary file of the firmware through the Y-Modem protocol. The module receives the file and automatically burns it into the internal memory. After the burning is completed, the ranging program is automatically executed;

[0090] The distance measurement program is a bare metal program driven by a timer interrupt event. Before the module is powered off, it will continuously report distance data at a frequency of 10ms.

[0091] The debugging program is a tool set used by the maintenance module, which interacts with the user through a terminal interface. Due to its sensitivity, password verification is required to run the debugging program;

[0092] After entering the distance measurement program, configure the SDI pin of the AD chip ZJC2001 to a high level, pull up the CONV pin to enter the 3-wire serial mode, and there is no busy indication. The software performs a sample at a minimum sampling interval of 2us. The current sample is compared with the previous sample value, the larger value is retained, and the smaller value is discarded. The maximum value is recorded every 50us, and is reserved for subsequent maximum value average processing;

[0093] When starting the conversion, first pull up the CONV pin, wait for the maximum conversion time of 1.6us, then pull down the CONV signal to read the conversion result. The conversion result is read on the rising edge of the serial clock SCK, and the minimum reading clock cycle is 15ns. After all 16BIT data are read, the SDO signal enters a high impedance state and waits for the next conversion to start;

[0094] The analog-to-digital chip ZJC2001 is driven by the A / D data reading module, the sampling voltage result is read once every 2us and the result is transmitted to the voltage maximum value finding module;

[0095] The voltage maximum value finding module records the maximum value of the sampled voltage within 12.5ms and transmits the result to the voltage-distance lookup table module;

[0096] The voltage-distance lookup table module maps the voltage value to the distance value through the built-in voltage-distance lookup table;

[0097] The maximum value generated by the voltage-distance lookup table module is transmitted through the serial port at a period of 12.5 ms;

[0098] Finally, the D / A voltage generation module converts the distance value into analog output by configuring an off-chip DA chip.

[0099] See also Fig.18 The present invention also provides a helicopter coaxial blade proximity monitoring device, including a magnetic bar 1, a bracket 2, a shell 3, a cover plate 4 and a PCB board 5. The number of the brackets 2 is two groups, and the two groups of brackets 2 are respectively fixedly connected to the shell 3 and are respectively located on one side of the shell 3. The two ends of the magnetic bar 1 are respectively fixedly connected to the corresponding brackets 2 and are located between the two groups of brackets 2. The PCB board 5 is embedded in the inside of the shell 3, and the cover plate 4 covers the shell 3 and is located on one side of the shell 3.

[0100] Furthermore, the PCB board 5 is any one of a transmitting module circuit board or a receiving module circuit board.

[0101] In this embodiment, the present invention uses the transmitting module to transmit signals, the receiving module to receive signals, and determines the distance between the transmitting module and the receiving module according to the strength of the received signal, thereby realizing the measurement of the distance between the upper blade and the lower blade, avoiding interference due to the high-altitude sun, and also avoiding reflection interference from the body. The distance between the upper blade and the lower blade can be monitored in real time efficiently and stably, the structure is simple and reliable, and no complex signal processing unit is required.

[0102] The present invention is obtained through sample testing and analysis. Table 1 is the test results, which shows the measured correspondence between the distance, the peak voltage of the driving electromagnetic antenna, and the peak-to-peak value of the receiving voltage.

[0103] Table 1 Relationship between received signal voltage and distance

[0104]

[0105]

[0106]

[0107] 16BIT data is signed data, and the data output format is as follows:

[0108] describe Analog input Vref = 2.5V Output 16BIT data Positive full scale 2.4999237 0x7FFF Mid Level 0V 0x0000 Negative full scale -2.5V 0x8000

[0109] See also Figures 4 to 11 The invention discloses a circuit diagram of a receiving module circuit board of the present invention. The receiving module circuit is composed of a two-stage low-noise operational amplifier, a differential drive circuit, an AD circuit, a DA circuit, a microprocessor, an interface drive circuit and a power supply circuit. The two-stage LMH6672 operational amplifier provides 30 dB gain low-noise amplification for the electromagnetic antenna input. The amplified signal enters a differential amplifier drive composed of two groups of LMH6672 operational amplifiers with a gain of 10 dB. The differential signal is input to AD7693 for sampling. The sampled analog quantity is sent to the microprocessor STM32G431KBU3. The microprocessor mainly processes the data signal sent by the AD chip and outputs real-time distance measurement information. The distance measurement information is output in two ways. One way is to convert the linearized distance analog quantity output through the DA conversion chip AD5660CRMZ, and the other way is to output the distance value in data mode through the RS422 interface. The whole circuit is powered by an external 5V and -5V generated by its own power supply chip TPS63700DRCR.

[0110] See also Figure 12 to Figure 14The circuit diagram of the transmitting module circuit board of the present invention is shown in the figure. The transmitting module circuit is composed of a 36KHz sine wave oscillation circuit, an electromagnetic antenna driving circuit, an output detection circuit and a power supply circuit. The sine wave oscillation circuit adopts an LMH6672 operational amplifier. Resistors R124, R125 and capacitors C121, C124 form a self-excited oscillation feedback. R122 and R123 control the oscillation depth so that the oscillation signal is a sine wave. U101B and U101A are output current drive amplifiers. P100 and P101 are output antenna balance interfaces. U102A and B are output signal detection differential outputs for detecting the transmission signal. U101 is a -5V voltage power conversion chip TPS63700DRCR. The chip outputs a -5V voltage and has a maximum output current of 500mA. Together with the +5V power supply, it provides power for the operational amplifier in the circuit.

[0111] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A helicopter coaxial blade approach monitoring method, characterized in that: The steps include: Install the transmitting module and the receiving module onto the propeller blades; The transmitting module is placed at the lower blade, and the electromagnetic antenna adopts an omnidirectional design to ensure that the antenna magnetic strength remains consistent in all directions when the blade is operated at a variable inclination angle; The receiving module is placed on the upper blade, and the electromagnetic antenna adopts an omnidirectional design to ensure that the antenna magnetic strength remains consistent in all directions when the blade is operated at a variable inclination angle; The transmitting module transmits a stable signal and the receiving module receives the signal. If the distance between the transmitting module and the receiving module is far, the received signal is weak, and if the distance between the transmitting module and the receiving module is close, the received signal is strong. The distance between the upper blade and the lower blade is identified by the strength of the received signal.

2. A helicopter coaxial blade proximity monitoring method as claimed in claim 1, characterized in that: The transmitting module includes an oscillator, an isolation amplifier, a processor, a transmitting interface circuit, a power conversion circuit and an electromagnetic antenna; The processor controls the oscillator to generate a 36KHz oscillation signal, which is amplified by the isolation amplifier and output to the electromagnetic antenna, wherein a portion of the signal is coupled to the detection output to the processor for transmission power detection, and the transmission interface circuit outputs an analog differential as a transmission power level indication, which is a constant differential value when the power is constant, and the power conversion circuit converts a single power supply into a differential power supply required by the isolation amplifier analog circuit.

3. A helicopter coaxial blade proximity monitoring method as claimed in claim 1, characterized in that: The receiving module includes an electromagnetic receiving antenna, a receiving amplifier, an AD sampling module, an MCU, a DA module, a receiving interface circuit, an analog conversion circuit and a power supply circuit; The electromagnetic receiving antenna receives the electromagnetic signal emitted by the transmitting module, converts it into an electrical signal and sends it to the receiving amplifier for 16-bit AD sampling. According to the maximum rotation speed of the blades, the blade interleaving time is calculated to be 0.8ms. A group of numbers are sampled at 0.05ms and the maximum value is taken to obtain 16 maximum values. The average of every 4 maximum values ​​is then taken to improve the detection accuracy. During the intersection period, 4 maximum average values ​​are obtained, and a maximum value is intercepted every 10ms. The corresponding pitch value is obtained by looking up the table, and then the corresponding analog voltage value is converted into an output through the DA module. The whole process is controlled by the MCU.

4. A helicopter coaxial blade proximity monitoring method as claimed in claim 3, characterized in that: The RS422 interface of the receiving interface circuit is a digital reporting interface.

5. A helicopter coaxial blade proximity monitoring method as claimed in claim 3, characterized in that: The AD sampling module has an AD full scale of 4096mv. After removing one sign bit from the 16-bit AD, it is calculated as 15, LSB = 125uV. Due to the nonlinearity of the coupling strength of the far and near signals, the distance accuracy of each distance segment is calculated as follows: At a distance between 100mm and 110mm, the AD sampling resolution is: (1321.59-1025.88) / (110-100)=29.571mv / mm=29571μv / mm, 1LSB is converted to a distance resolution of 125 / 29571=0.004mm; At a distance between 500mm and 510mm, the AD sampling resolution is: (28.26-26.67) / (500-490)=0.159mv / mm=159μv / mm, 1LSB is converted to a distance resolution of 125 / 159=0.79mm; At distances between 1100mm and 1200mm, the AD sampling resolution is: (10.5-7.10) / (1200-1100)=0.034mv / mm=34μv / mm, 1LSB is converted to a distance resolution of 125 / 34=3.68mm.

6. A helicopter coaxial blade proximity monitoring method as claimed in claim 3, characterized in that: The receiving module includes a boot program, a distance measuring program, a debugging program and a peripheral driver; The boot program is a bare metal program, and its main functions are to initialize board-level peripherals, update and burn firmware, and provide a menu to select to execute a ranging program or a debugging program; The main functions of the distance measurement program are to call the distance-voltage lookup table from the Flash memory, execute the distance measurement algorithm, drive the A / D and D / A chips to work, and report the distance data to the upper computer through the RS422 serial port; The debugging program runs RTOS and provides a simple terminal interactive interface. Its main functions are to read and write distance voltage lookup tables, monitor the working conditions of the underlying hardware, and read and write debugging functions of electronic tags; The peripheral driver provides a data interaction interface between software and hardware for the upper layer module.

7. A helicopter coaxial blade proximity monitoring method as claimed in claim 3, characterized in that: The workflow of the receiving module includes the following steps: After the interface module is powered on, the boot program is executed first. During this stage, the countdown is 10 seconds. Within 10 seconds, you can manually choose to burn firmware, execute the distance measurement program, or execute the debugging program in the serial terminal interface. After the countdown ends, the distance measurement program will be automatically run. The firmware burning is realized through the Y-Modem protocol. The host terminal sends the binary file of the firmware through the Y-Modem protocol. The module receives the file and automatically burns it into the internal memory. After the burning is completed, the ranging program is automatically executed; The distance measurement program is a bare metal program driven by a timer interrupt event. Before the module is powered off, it will continuously report distance data at a frequency of 10ms. The debugging program is a tool set used by the maintenance module, which interacts with the user through a terminal interface. Due to its sensitivity, password verification is required to run the debugging program; After entering the distance measurement program, configure the SDI pin of the AD chip ZJC2001 to a high level, pull up the CONV pin to enter the 3-wire serial mode, and there is no busy indication. The software performs a sample at a minimum sampling interval of 2us. The current sample is compared with the previous sample value, the larger value is retained, and the smaller value is discarded. The maximum value is recorded every 50us, and is reserved for subsequent maximum value average processing; When starting the conversion, first pull up the CONV pin, wait for the maximum conversion time of 1.6us, then pull down the CONV signal to read the conversion result. The conversion result is read on the rising edge of the serial clock SCK, and the minimum reading clock cycle is 15ns. After all 16BIT data are read, the SDO signal enters a high impedance state and waits for the next conversion to start; The analog-to-digital chip ZJC2001 is driven by the A / D data reading module, the sampling voltage result is read once every 2us and the result is transmitted to the voltage maximum value finding module; The voltage maximum value finding module records the maximum value of the sampled voltage within 12.5ms and transmits the result to the voltage-distance lookup table module; The voltage-distance lookup table module maps the voltage value to the distance value through the built-in voltage-distance lookup table; The maximum value generated by the voltage-distance lookup table module is transmitted through the serial port at a period of 12.5 ms; Finally, the D / A voltage generation module converts the distance value into analog output by configuring an off-chip DA chip.

8. A helicopter coaxial blade proximity monitoring device, characterized in that: It includes a magnetic bar, a bracket, a shell, a cover plate and a PCB board. The number of the brackets is two groups. The two groups of brackets are fixedly connected to the shell and are respectively located on one side of the shell. The two ends of the magnetic bar are respectively fixedly connected to the corresponding brackets and are located between the two groups of brackets. The PCB board is embedded in the shell. The cover plate covers the shell and is located on one side of the shell.

9. A helicopter coaxial blade proximity monitoring device as claimed in claim 8, characterized in that: The PCB board is any one of a transmitting module circuit board or a receiving module circuit board.

Images