Multi-mode composite altimeter

Abstract

A multimode composite altimeter disclosed by the present invention comprises a transceiver and antennas, the antennas comprise a single antenna and a combined antenna, and the combined antenna comprises an ultrasonic wave receiving and transmitting module, a laser receiving and transmitting module and a C wave band transmitting antenna; the ultrasonic wave receiving and transmitting module measures and calculates height counting pulse signals of ultrasonic waves, the laser receiving and transmitting module measures and calculates height counting pulse signals of laser, the C-band transmitting antenna transmits signals to the ground, the single antenna receives reflected signals, and all the signals are transmitted to the transceiver. The transceiver comprises a power panel, a filtering assembly, a microwave assembly, a servo board, a signal processing board, a shell, a cover plate and a front guide plate, and the parts are matched with each other through respective processing circuits according to pulse signals and radio frequency signals transmitted by the antenna to calculate the height of the airplane. The method is high in measurement precision, good in reliability and high in safety, and can be used for measuring the height of the unmanned aerial vehicle from the ground in the air.

Description

Technical Field

[0001] The present invention belongs to the technical field of instruments and meters, and specifically designs a multi-mode composite altimeter which can be used to measure the height of a UAV in the air from the ground. Background Art

[0002] Radio altimeters are widely used in military and civilian aircraft, primarily for measuring the aircraft's altitude above the ground to ensure flight safety. Radio altimeters offer a choice of frequency bands, enabling rapid and accurate measurement of the aircraft's altitude relative to the ground. They are essential and critical equipment in the aviation industry. With rising aviation safety awareness and continuous technological advancements, modern radio altimeters are gaining increasing attention from airlines and aircraft manufacturers. The shift towards more accurate, efficient, and reliable radio altimeters is becoming a future market trend.

[0003] Patent document CN201920680178.3 discloses a digital radio altimeter, which includes a transceiver, antenna, and indicator. It is typically used during aircraft approach and landing. Because the transceiver uses aluminum plates and hinged plates, and internal components are secured with screws, slides, cable clamps, and springs, airflow can cause the radio altimeter to shake during takeoff or landing, potentially damaging internal components and affecting altitude measurement accuracy. This altimeter is significantly affected by the external environment, resulting in poor reliability and safety.

[0004] Patent document CN200620049336.8 discloses a single-antenna radio altimeter, comprising an antenna, a circulator, a microwave transmitting unit, a microwave receiving unit, an intermediate frequency filter, a main amplifier, a microprocessor, and a triangle wave generator. While this single-antenna radio altimeter reduces antenna installation space, the placement of the antenna outside the housing results in susceptibility to interference, low accuracy, and large altitude measurement errors. The altimeter antenna's susceptibility to interference reduces altitude measurement accuracy, and the inclusion of a circulator in the altimeter increases power consumption.

[0005] Patent document CN201911406206.3 discloses a radio altimeter, which includes a transceiver antenna assembly, a microwave transceiver assembly, and a signal processing module. During the actual altimeter measurement process, the temperature and temperature compensation are collected by the temperature sensor on the signal processing module. Although the altimeter can solve the problem of reduced accuracy caused by external temperature drift, its temperature sensor is also affected by the heat generated by other components inside the transceiver, which causes a large temperature drift, resulting in a large error in the altimeter measurement. Because the heat generated by other components inside the altimeter transceiver will interfere with the sensor's collection of temperature information, its adaptability to the environment is weak, resulting in low altitude measurement accuracy. The temperature sensor, oscillator and other components in the altimeter are large in size, resulting in an increase in the overall device size.

[0006] Currently, drones fly over a variety of terrain, including but not limited to jungles, rivers, oceans, mountains, and urban environments. These digital altimeters and radio altimeters are unable to accurately measure altitude, resulting in errors and erroneous altitude measurements, compromising flight safety. During drone flight and takeoff and landing, due to the immaturity of single-sheet antenna technology, the accuracy errors caused by antenna installation spacing cannot be eliminated at near-ground altitudes. The tracking problem of external mounting cannot be completely eliminated during drone acceleration or deceleration. Furthermore, the slant range error, multipath interference, and tracking harmonics caused by dual antenna installations have not been fully resolved. This leads to errors in the altimeter's true altitude measurement of the ground, posing a potential threat to the drone's safe flight. Summary of the Invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and provide a multi-mode composite altimeter to improve measurement accuracy, reduce size, reduce power consumption, and realize real-time measurement of UAV relative to the ground or sea surface in complex environments to ensure its safe flight.

[0008] The technical approach to achieving the objectives of the present invention is as follows: by providing a temperature detection circuit and a temperature compensation module to measure the ambient air temperature, the ultrasonic wave propagation velocity is corrected in real time, and the impact of temperature is reduced. Furthermore, by providing heat dissipation ribs on both sides of the transceiver to facilitate convection heat exchange between the exterior of the housing and the air, the overall transceiver temperature is reduced, reducing the impact of temperature and thus improving ranging accuracy. The altimeter is reduced in size by using a small, low-power antenna, a low-power laser, and a piezoelectric chip. The stability and safety of the altimeter are improved by modifying the main structure and materials of the transceiver. Furthermore, by integrating radio, laser, and ultrasonic altimetry into a fusion altimeter, the altimeter's measurement accuracy and the reliability of the measured data are improved.

[0009] According to the above ideas, the multi-mode composite altimeter of the present invention includes: a transceiver and an antenna, wherein the transceiver includes a power supply board, a filter component, a microwave component, a servo board, a signal processing board, a housing, a cover plate and a front guide plate;

[0010] The power board is installed on one side close to the housing and is fixed by locking strips on both sides to reduce the impact of heat generated by the power board during operation on other components and facilitate the conduction of heat to the housing;

[0011] The filter assembly is mounted on the front guide plate;

[0012] The microwave assembly is mounted on the side wall of the housing to conduct heat directly to the housing for heat dissipation. Scattering ribs are provided on both sides of the housing for convection heat exchange between the outside of the housing and the air.

[0013] The servo board and the signal processing board are fixed to the housing via locking strips on both sides;

[0014] The shell and the cover plate are connected in an L-shaped overlapping manner, and the middle part of the cover plate is connected to the front guide plate;

[0015] The antenna includes a single antenna and a combined antenna;

[0016] The combined antenna comprises: an ultrasonic transceiver module, a laser transceiver module, and a C-band transmitting antenna;

[0017] The ultrasonic transceiver module is used to measure the ultrasonic height count pulse signal and transmit it to the signal processing board;

[0018] The laser transceiver module is used to measure the laser height count pulse signal and transmit it to the signal processing board;

[0019] The C-band transmitting antenna is used to transmit a signal to the ground, and receive the reflected signal through the single antenna, transmit it to the microwave component, mix it with the radio frequency signal generated by the microwave component, generate a beat signal, and transmit it to the signal processing board;

[0020] The signal processing board decodes and tracks the ultrasonic altitude counting pulse signal, the laser altitude counting pulse signal and the beat signal respectively, calculates the ultrasonic altitude, the laser altitude and the radio altitude information; and then calculates the composite altitude with high reliability and transmits it to the flight control system.

[0021] Preferably, the power board is provided with a power module and a filter circuit. The power module adopts an input / output isolated DC-DC conversion module to convert the +28V voltage into the +5V, +15V, -15V, and +30V voltages required for the operation of the transceiver; the filter circuit is connected to the output end of the power module to filter out ripple interference on the power line and ensure that the output voltage is stable and reliable.

[0022] Preferably, the filtering component adopts a low-frequency socket with a filtering function, which is internally provided with an electromagnetic compatibility protection circuit and a power supply characteristic protection circuit; the electromagnetic compatibility protection circuit is used to reduce the damage to components caused by electromagnetic interference and ensure the normal operation of electronic equipment; the power supply characteristic protection circuit is used to prevent the power supply from being damaged by excessive voltage or current and ensure the normal operation of the power supply.

[0023] Preferably, the microwave component includes a microwave oscillator, a cavity resonant detector, a low-noise preamplifier and a mixer. The microwave oscillator is connected to the sawtooth wave generator on the servo board to generate a stable radio frequency signal; the cavity resonant detector is composed of two independent dielectric resonant detectors. When the radio frequency signal enters the two dielectric resonant detectors, two sharp pulse voltages are output at the resonant frequency respectively, which are used for frequency deviation self-calibration and calibration and calculation of the modulated sawtooth wave. The low-noise amplifier completes the amplification of the received radio frequency signal; the mixer mixes the output signal of the low-noise amplifier with the local oscillator signal to generate a beat signal.

[0024] Preferably, the servo board includes a mixer cut-off circuit, a high-pass filter, an equalizer gain device, a tracking discriminator, an error voltage integrator, a sawtooth wave generator, and a control discriminator circuit;

[0025] The mixer cut-off circuit is used to prevent or allow the beat signal to be transmitted to the tracking loop, so as to input the self-test signal to perform BIT detection on the tracking loop;

[0026] The high-pass filter is used to filter out low-frequency noise;

[0027] The equalizer is used to control the gain circuit to generate different gains for echo signals at different heights, which increase with the actual height, to ensure that long-distance signals can be sufficiently amplified and short-distance signals are not saturated due to excessive signal strength. The amplified beat signal is sent to the control frequency discriminator and the tracking frequency discriminator at the same time.

[0028] The control discriminator is used to determine whether to enter the tracking state based on the input signal-to-noise ratio, and enter the search state when the input signal-to-noise ratio does not meet the tracking conditions. When the detection result of the control discriminator exceeds the set threshold, the control discriminator controls the sawtooth wave generator to stop scanning and enter the tracking state, and adjusts the modulation period of the sawtooth wave according to the error voltage to keep the beat tracking signal constant.

[0029] The sawtooth wave generator is used to generate a sawtooth wave, and the sawtooth wave modulation period is scanned from small to large until entering a tracking state;

[0030] The tracking discriminator is used to output an error voltage. After entering the tracking state, the tracking discriminator will always track the change in height.

[0031] The error voltage integrator is used to stabilize the tracking loop. In the tracking state, the error voltage integrator integrates the output error voltage of the tracking discriminator and sends the DC voltage to the compensation amplifier. The compensation amplifier generates a GVA signal based on the DC voltage. The GVA signal is used to charge the energy storage capacitor of the sawtooth wave generator. A monostable circuit can be used to reset the sawtooth wave to control the sawtooth wave modulation period.

[0032] Preferably, the signal processing board includes a signal processing circuit and a height data processing and interface circuit; the signal processing circuit is used to decode and track the ultrasonic height pulse signal, the laser height pulse signal and the beat signal respectively, and calculate the ultrasonic height, laser height and radio height information;

[0033] The altitude data processing circuit is used to fuse radio altitude, ultrasonic altitude and laser altitude according to an altitude fusion algorithm to calculate a composite altitude measurement with high reliability;

[0034] The interface circuit is used to transmit the calculated composite altitude information to the flight control system and other cross-linking equipment.

[0035] Preferably, the ultrasonic transceiver module includes an ultrasonic chip circuit, an ultrasonic transmission conditioning circuit, an ultrasonic echo receiving and processing circuit, and a temperature detection circuit;

[0036] The ultrasonic chip circuit uses the SB5227 ultrasonic ASIC chip, which contains an oscillator, a frequency divider, a microprocessor, a latch, and is compatible with split or integrated ultrasonic sensors. It is used to set the transmission power and the sensor's damping characteristic compensation coefficient to prevent aftershocks after the transmission cycle, and receives a frequency signal proportional to the ambient temperature.

[0037] The ultrasonic emission conditioning circuit includes an ultrasonic generator and a counter. The generator is composed of two piezoelectric crystals and a resonance plate. It uses the resonance of the piezoelectric crystal to drive the surrounding air to vibrate. When the generator emits ultrasonic waves toward the ground, the counter starts timing at the same time as the emission. The ultrasonic waves immediately return when they hit the ground.

[0038] The ultrasonic echo receiving and processing circuit includes an ultrasonic receiver. After the receiver receives the return wave, the counter immediately stops timing. The ultrasonic echo receiving and processing circuit transmits the echo signal to the ultrasonic chip circuit. The ultrasonic chip circuit converts the signal into a digital pulse signal and transmits it to the signal processing circuit.

[0039] The temperature detection circuit is used to perform temperature compensation on the sound velocity and distance, thereby improving the measurement accuracy.

[0040] Preferably, the laser transceiver module includes a laser transmitting circuit, a laser receiving circuit, a data signal processing circuit and a power supply filtering module;

[0041] The laser emission circuit is composed of a sinusoidal signal generator, a semiconductor laser and a drive circuit. The laser emission circuit is used to convert the electrical signal into an optical signal and perform sinusoidal modulation of the semiconductor laser. The sinusoidal modulation is to add a high-precision sinusoidal signal to a stable bias current.

[0042] The laser receiving circuit is composed of an avalanche diode and its signal amplification and filtering circuit, which is used to convert the optical signal into an electrical signal, amplify the signal, filter noise and reduce the phase deviation of the sinusoidal signal;

[0043] The data signal processing circuit is composed of two high-frequency AD conversion chips and a comparator, which is used to control the phase difference between the modulation signal and the measurement signal required for laser emission and the time of flight timing, and output the height measurement data to the signal processing circuit in the form of a digital pulse signal;

[0044] The power filter module is used to convert the input +28V voltage into the +12V voltage required by the laser module and make the voltage stable and reliable.

[0045] Preferably, the C-band transmitting antenna adopts a microstrip antenna structure for transmitting radio frequency signals to the ground.

[0046] Preferably, the single antenna is installed on the tail boom of the aircraft, is well grounded to the aircraft casing, and is connected to the transceiver via a radio frequency cable, for receiving signals reflected from the ground and transmitting them to the transceiver.

[0047] Compared with related technologies, the multi-mode composite altimeter provided by the present invention has the following beneficial effects:

[0048] 1. The present invention provides a temperature detection circuit and a temperature compensation module in the ultrasonic module of the combined antenna to measure the temperature of the air environment and perform real-time correction of the ultrasonic propagation speed, thereby reducing the impact of temperature. Furthermore, the provision of heat dissipation ribs in the transceiver allows for convection heat exchange between the exterior of the housing and the air, thereby lowering the overall temperature of the transceiver, reducing the impact of temperature, and improving the measurement accuracy and reliability of the altimeter.

[0049] 2. The present invention uses a small, low-power C-band transmitting antenna in the combined antenna, and a low-power laser and piezoelectric chip in the laser module, thereby reducing the power consumption of the altimeter. At the same time, the modular and integrated self-test design is adopted in the servo board and signal processing board in the transceiver, which can reduce the number of discrete components and the size of the altimeter.

[0050] 3. The transceiver housing of the present invention adopts an aluminum alloy precision casting structure and is provided with weight-reducing grooves and reinforcing ribs on the outside of the housing, thereby improving the structural strength. At the same time, since the filter component is installed on the front guide plate, the microwave component is installed on the side wall of the housing, and the power board, servo board and signal processing board are fixed to the housing by locking strips on both sides, and the housing and cover are connected by an L-shaped overlap method, the stability of the altimeter is improved.

[0051] 4. The present invention adopts a closed design for both the transceiver and the combined antenna, thereby reducing electromagnetic compatibility gap leakage, preventing the transceiver and the combined antenna from emitting electromagnetic interference outward and being affected by external electromagnetic interference, thereby improving the electromagnetic compatibility of the altimeter; at the same time, since the power supply adopts DC28V and is filtered, isolated and shielded, it will not affect the safety of normal operators, thereby improving the safety of the altimeter.

[0052] 5. The present invention adopts an altitude fusion algorithm in the altitude data processing circuit to fuse radio altitude, ultrasonic altitude and laser altitude, thereby calculating a highly reliable composite altitude measurement, thereby improving the altitude measurement accuracy of the altimeter and the reliability of the altitude measurement data. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A schematic diagram of the structure of a multi-mode composite altimeter according to an embodiment of the present invention;

[0054] Figure 2 A schematic structural diagram of a multi-mode composite altimeter according to another embodiment of the present invention;

[0055] Figure 3 This is a structural schematic diagram of the multi-mode composite altimeter according to another embodiment of the present invention;

[0056] Figure 4 This is a functional block diagram of a multi-mode composite altimeter according to an embodiment of the present invention;

[0057] Figure 5 This is a schematic diagram of a power board circuit according to an embodiment of the present invention;

[0058] Figure 6 This is a hardware block diagram of an ultrasonic module according to an embodiment of the present invention;

[0059] Figure 7This is a schematic diagram of the operation of a signal processing board according to an embodiment of the present invention;

[0060] Figure 8 This is a flow chart for calculating the height of an aircraft from the ground according to an embodiment of the present invention;

[0061] Figure 9 This is a test result diagram of the multi-mode composite altimeter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0063] Please refer to Figures 1 to 3 , is a multi-mode composite altimeter of this example; it includes a transceiver 1 and an antenna 2, wherein the antenna 2 includes a single antenna 21 and a combined antenna 22.

[0064] The transceiver 1 includes a power board 11 , a filter component 12 , a microwave component 13 , a servo board 14 , a signal processing board 15 , a housing 16 , a cover 17 , and a front guide plate 18 .

[0065] The power board 11 is mounted on one side of the transceiver housing and secured by locking strips on both sides. The filter assembly 12 is mounted on the front guide plate 18. The microwave assembly 13 is mounted on the side wall of the housing. The servo board 14 and the signal processing board 15 are secured to the housing 16 by locking strips on both sides. The housing 16 and the cover plate 17 are connected in an L-shaped overlap manner, with the middle portion of the cover plate 17 connected to the front guide plate 18.

[0066] The power board 11 is provided with a power module and a filter circuit. The power module adopts an input / output isolated DC-DC conversion module to convert the +28V voltage into the +5V, +15V, -15V, and +30V voltages required for the operation of the transceiver; the filter circuit is connected to the output end of the power module to filter out ripple interference on the power line and ensure that the output voltage is stable and reliable.

[0067] The filtering component 12 adopts a low-frequency socket with a filtering function, and is internally provided with an electromagnetic compatibility protection circuit and a power supply characteristic protection circuit; the electromagnetic compatibility protection circuit is used to reduce the damage to components caused by electromagnetic interference and ensure the normal operation of electronic equipment; the power supply characteristic protection circuit is used to prevent the power supply from being damaged by excessive voltage or current and ensure the normal operation of the power supply.

[0068] The microwave component 13 includes a microwave oscillator, a cavity resonant detector, a low-noise preamplifier, and a mixer. The microwave oscillator is connected to the sawtooth wave generator on the servo board to generate a stable radio frequency signal. The cavity resonant detector is composed of two independent dielectric resonant detectors. When the radio frequency signal enters the two dielectric resonant detectors, two sharp pulse voltages are output at the resonant frequency respectively for frequency deviation self-calibration and calibration and calculation of the modulated sawtooth wave. The low-noise amplifier completes amplification of the received radio frequency signal. The mixer mixes the output signal of the low-noise amplifier with the local oscillator signal to generate a beat signal.

[0069] The servo board 14 is mainly composed of a mixer cut-off circuit, a high-pass filter, an equalizer, a tracking discriminator, an error voltage integrator, a sawtooth wave generator, a control discriminator and other circuits; the mixer cut-off circuit is used to prevent or allow the beat signal from being transmitted to the tracking loop so that the self-test signal can be sent to perform BIT detection on the tracking loop; the high-pass filter is used to filter out low-frequency noise; the equalizer is used to control the gain circuit to generate different gains for echo signals at different heights that increase with the increase of actual height, so as to ensure that long-distance signals can be sufficiently amplified and short-distance signals are not saturated due to excessive signal strength. The amplified beat signal is sent to the control discriminator and the tracking discriminator at the same time; the control discriminator is used to determine whether to enter the tracking state according to the input signal-to-noise ratio, and enter the search state when the input signal-to-noise ratio does not meet the tracking conditions; when the control When the detection result of the frequency discriminator exceeds a set threshold, the frequency discriminator controls the sawtooth wave generator to stop scanning and enter a tracking state, and adjusts the modulation period of the sawtooth wave according to the error voltage to keep the beat tracking signal constant. The sawtooth wave generator is used to generate a sawtooth wave, and the sawtooth wave modulation period is scanned from small to large until entering the tracking state. The tracking frequency discriminator is used to output an error voltage. After entering the tracking state, the tracking frequency discriminator will continuously track the change in height. The error voltage integrator is used to stabilize the tracking loop. In the tracking state, the error voltage integrator integrates the output error voltage of the tracking frequency discriminator and sends the DC voltage to the compensation amplifier. The compensation amplifier generates a GVA signal based on the DC voltage, and charges the energy storage capacitor of the sawtooth wave generator through the GVA signal. A monostable circuit can be used to reset the sawtooth wave to control the sawtooth wave modulation period.

[0070] The signal processing board 15 includes a signal processing circuit and an altitude data processing and interface circuit, which are used to decode and track the ultrasonic altitude counting pulse signal, the laser altitude counting pulse signal and the beat signal respectively, and calculate the ultrasonic altitude, laser altitude and radio altitude information; then calculate the highly reliable composite altitude measurement height and transmit it to the flight control system and other cross-linking equipment.

[0071] The single antenna 21 and the combined antenna 22 are both connected to the transceiver via a radio frequency cable; and the single antenna 21 and the combined antenna 22 are placed separately.

[0072] Reference Figure 4 The combined antenna 22 includes an ultrasonic transceiver module 221 , a laser transceiver module 222 , and a C-band transmitting antenna 223 .

[0073] The ultrasonic transceiver module 221 includes an ultrasonic transmission conditioning circuit, an ultrasonic echo receiving and processing circuit, and a temperature detection circuit, and is used to measure the ultrasonic height counting pulse signal and transmit it to the signal processing board 15;

[0074] The laser transceiver module 222 is used to measure the laser height count pulse signal and transmit it to the signal processing board; it includes a laser emitting circuit, a laser receiving circuit, a power supply filter module and a data signal processing circuit, wherein the laser emitting circuit is composed of a sinusoidal signal generator, a semiconductor laser and a driving circuit, and the laser emitting circuit is used to convert the electrical signal into an optical signal and complete the sinusoidal modulation of the semiconductor laser. The sinusoidal modulation is to add a high-precision sinusoidal signal to a stable bias current; the laser receiving circuit is composed of an avalanche diode and its signal amplification and filtering circuit, which is used to convert the optical signal into an electrical signal, amplify the signal, filter noise and reduce the phase offset of the sinusoidal signal; the power supply filter module is used to convert the input +28V voltage into the +12V voltage required by the laser module and make the voltage stable and reliable; the data signal processing circuit is composed of two high-frequency AD conversion chips and a comparator, which is used to control the phase difference and flight time timing of the modulation signal and measurement signal required for laser emission, and is used to measure the laser height count pulse signal and transmit it to the signal processing board.

[0075] The C-band transmitting antenna 223 is used to transmit signals to the ground, and receives the reflected signal through the single antenna 21 and transmits it to the microwave component 13, mixes with the radio frequency signal generated by the microwave component 13, generates a beat signal, and transmits it to the signal processing circuit.

[0076] The signal processing circuit is used to decode and track the ultrasonic height pulse signal, the laser height pulse signal and the beat signal respectively, and calculate the ultrasonic height, laser height and radio height information;

[0077] The altitude data processing circuit is used to fuse radio altitude, ultrasonic altitude, and laser altitude according to the altitude fusion algorithm to calculate a composite altitude with high credibility; the interface circuit is used to transmit the calculated composite altitude information to the flight control system and other cross-linking equipment.

[0078] Reference Figure 5The ultrasonic transceiver module 221 includes an ultrasonic chip circuit, an ultrasonic transmission conditioning circuit, an ultrasonic echo receiving and processing circuit, and a temperature detection circuit; the ultrasonic chip circuit adopts the SB5227 ultrasonic special integrated circuit chip, which contains an oscillator, a frequency divider, a microprocessor, a latch, and an adaptive split or integrated ultrasonic sensor for setting the transmission power and the damping characteristic compensation coefficient of the sensor to prevent aftershocks after the transmission cycle and receive a frequency signal proportional to the ambient temperature; the ultrasonic transmission conditioning circuit includes an ultrasonic generator and a counter, the generator consists of two piezoelectric chips and a resonance plate, and uses the resonance of the piezoelectric crystal to drive the vibration of the surrounding air to work. When the generator transmits ultrasonic waves to the ground through the transmitting head, the counter starts timing at the same time as the transmission, and the ultrasonic waves immediately return when they hit the ground; the ultrasonic echo receiving and processing circuit includes an ultrasonic receiver. After receiving the return wave through the receiver head, the counter immediately stops timing, and the ultrasonic echo receiving and processing circuit transmits the echo signal to the ultrasonic chip circuit, and the ultrasonic chip circuit converts the signal into a digital pulse signal and transmits it to the signal processing circuit. The temperature detection circuit is used to perform temperature compensation on the sound velocity and distance, thereby improving the measurement accuracy.

[0079] Reference Figure 6 The power board 11 includes a power supply and a filter circuit. The power module uses two input / output isolated DC-DC conversion modules, wherein the first power module converts the +28V voltage into +5V, +15V, and -15V voltages; the second power module converts the +28V voltage into +30V voltage. At the same time, the filter circuit is connected to the output end of the power module to filter out ripple interference on the power line and ensure stable and reliable output voltage.

[0080] Reference Figure 7 The signal processing circuit and the high-level data processing and interface circuit in the signal processing board 15 are operated by a microprocessor, which is implemented as follows:

[0081] The microprocessor determines the fault type through search reset and search / track detection;

[0082] The microprocessor completes the self-test work through calibration control and mixer cut-off and makes the height measurement component enter the periodic self-test state;

[0083] The microprocessor converts the laser digital pulse signal and the ultrasonic digital pulse signal into ranging time according to the decoding requirements, calculates the laser ranging information and the ultrasonic ranging information, and performs counting measurement based on the input sawtooth wave periodic signal and cavity pulse signal. The radio altitude information is calculated through the measurement and outputted through the interface circuit.

[0084] The microprocessor controls the transmitting signal of the microwave component VCO by calibrating the amplitude and voltage average of the sawtooth wave, so that the center frequency and frequency deviation of the transmitting signal remain constant.

[0085] Reference Figure 8 , for this example, the calculation of the aircraft's height from the ground is implemented as follows:

[0086] After the altimeter is powered on, the data processing module in the transceiver completes the sampling of radio altimeter data, laser altimeter data, and ultrasonic altimeter data. The altimeter data is mainly based on radio altimeter data, and the validity of the altimeter data is judged:

[0087] When the height data is invalid, it is discarded and resampled until the data is valid, and then the data is filtered, fused, and output;

[0088] When the altitude data is between 0m and 2m, the radio altitude data, laser altitude data, and ultrasonic altitude data are fused to obtain accurate altitude data and transmit it to the flight control system and cross-linking equipment;

[0089] When the altitude data is between 2m and 100m, the radio altitude data and laser altitude data are fused to obtain accurate altitude data and transmit it to the flight control system and cross-linking equipment;

[0090] When the altitude data is greater than 100m, the radio altitude data will be directly output to the flight control system and cross-linking equipment.

[0091] The effects of the present invention can be further illustrated by the following experimental results:

[0092] 1. Test environment: including ground environment, forest environment and lake environment.

[0093] 2. Test content

[0094] 1. Aircraft testing in a ground environment:

[0095] The aircraft was tested in several states: taking off and hovering at low altitude, gradually rising, rising to a set altitude and hovering for a period of time, and finally landing. That is, when the aircraft was hovering at low altitude, radio altimetry, laser altimetry, and ultrasonic altimetry were used to obtain altitude data, and these three types of data were fused; when the aircraft was rising, hovering, and descending, radio altimetry and laser altimetry were used to obtain altitude data, and these two types of data were fused.

[0096] 2. Aircraft testing in a forest environment:

[0097] After the aircraft enters the forest environment, it uses radio altimetry and laser altimetry to obtain altitude data and then fuses the two types of data.

[0098] 3. Aircraft testing in lake environment:

[0099] After the aircraft enters the lake environment, it uses radio altimetry and laser altimetry to obtain altitude data, and then fuses these two types of data.

[0100] The test results of the above three environments are as follows Figure 9 shown.

[0101] from Figure 9 It can be seen that when the aircraft was tested in a ground environment, its fused data was basically consistent with the laser data, radio data, and ultrasonic data; when the aircraft was tested in a forest environment, its laser data and radio data were affected by interference factors such as leaves, resulting in errors, and the fused data can reduce the errors; when the aircraft was tested in a lake environment, its fused data was basically consistent with the radio data, and then the aircraft left the lake environment and landed on the ground.

[0102] The above results show that the present invention can achieve real-time and accurate measurement of the UAV relative to the ground or sea surface in complex environments, ensuring its safe flight.

[0103] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A multi-mode composite altimeter, characterized in that: include: A transceiver (1) and an antenna (2), wherein the transceiver (1) comprises a power supply board (11), a filter component (12), a microwave component (13), a servo board (14), a signal processing board (15), a housing (16), a cover plate (17), and a front guide plate (18); The power board (11) is installed on a side close to the housing (16) and is fixed by locking strips on both sides to reduce the influence of heat generated by the power board (11) during operation on other components and facilitate the conduction of heat to the housing; The filter assembly (12) is mounted on the front guide plate (18); The microwave assembly (13) is mounted on the side wall of the housing (16) to conduct heat directly to the housing (16) for heat dissipation. Scattering ribs are provided on both sides of the housing (16) for heat exchange between the outside of the housing and the air through convection. The servo board (14) and the signal processing board (15) are fixed to the housing (16) via locking strips on both sides; The housing (16) and the cover plate (17) are connected in an L-shaped overlapping manner, and the middle portion of the cover plate (17) is connected to the front guide plate (18); The antenna (2) includes a single antenna (21) and a combined antenna (22); The combined antenna (22) comprises: an ultrasonic transceiver module (221), a laser transceiver module (222), and a C-band transmitting antenna (223); The ultrasonic transceiver module (221) is used to measure the ultrasonic height counting pulse signal and transmit it to the signal processing board (15); The laser transceiver module (222) is used to measure the laser height count pulse signal and transmit it to the signal processing board (15); The C-band transmitting antenna (223) is used to transmit a signal to the ground, and receive the reflected signal through the single antenna (21), transmit the reflected signal to the microwave component (13), mix the reflected signal with the radio frequency signal generated by the microwave component (13), generate a beat signal, and transmit the beat signal to the signal processing board (15); The signal processing board (15) decodes and tracks the ultrasonic height counting pulse signal, the laser height counting pulse signal and the beat signal respectively, calculates the ultrasonic height, the laser height and the radio height information; and then calculates the composite height measurement with high reliability and transmits it to the flight control system.

2. A multi-mode composite altimeter according to claim 1, characterized in that: The power board (11) is provided with a power module and a filter circuit. The power module adopts an input / output isolated DC-DC conversion module to convert the +28V voltage into the +5V, +15V, -15V, and +30V voltages required for the operation of the transceiver. The filter circuit is connected to the output end of the power module to filter out ripple interference on the power line and ensure that the output voltage is stable and reliable.

3. The multi-mode composite altimeter according to claim 1, characterized in that: The filtering component (12) adopts a low-frequency socket with a filtering function, and is internally provided with an electromagnetic compatibility protection circuit and a power supply characteristic protection circuit; the electromagnetic compatibility protection circuit is used to reduce the damage of electromagnetic interference to components and ensure the normal operation of electronic equipment; the power supply characteristic protection circuit is used to prevent the power supply from being damaged by excessive voltage or current, ensuring the normal operation of the power supply.

4. The multi-mode composite altimeter according to claim 1, characterized in that: The microwave component (13) includes a microwave oscillator, a cavity resonant detector, a low-noise preamplifier and a mixer. The microwave oscillator is connected to the sawtooth wave generator on the servo board and is used to generate a stable radio frequency signal. The cavity resonant detector is composed of two independent dielectric resonant detectors. When the radio frequency signal enters the two dielectric resonant detectors, two sharp pulse voltages are output at the resonant frequency respectively, which are used for frequency deviation self-calibration and calibration and calculation of the modulated sawtooth wave. The low-noise amplifier completes amplification of the received radio frequency signal. The mixer mixes the output signal of the low noise amplifier with the local oscillator signal to generate a beat signal.

5. The multi-mode composite altimeter according to claim 1, characterized in that: The servo board (14) comprises a mixer cut-off circuit, a high-pass filter, an equalizer gain device, a tracking discriminator, an error voltage integrator, a sawtooth wave generator, and a control discriminator circuit; The mixer cut-off circuit is used to prevent or allow the beat signal to be transmitted to the tracking loop, so as to input the self-test signal to perform BIT detection on the tracking loop; The high-pass filter is used to filter out low-frequency noise; The equalizer is used to control the gain circuit to generate different gains for echo signals at different heights, which increase with the actual height, to ensure that long-distance signals can be sufficiently amplified and short-distance signals are not saturated due to excessive signal strength. The amplified beat signal is sent to the control frequency discriminator and the tracking frequency discriminator at the same time. The control discriminator is used to determine whether to enter the tracking state based on the input signal-to-noise ratio, and enter the search state when the input signal-to-noise ratio does not meet the tracking conditions. When the detection result of the control discriminator exceeds the set threshold, the control discriminator controls the sawtooth wave generator to stop scanning and enter the tracking state, and adjusts the modulation period of the sawtooth wave according to the error voltage to keep the beat tracking signal constant. The sawtooth wave generator is used to generate a sawtooth wave, and the sawtooth wave modulation period is scanned from small to large until entering a tracking state; The tracking discriminator is used to output an error voltage. After entering the tracking state, the tracking discriminator will always track the change in height. The error voltage integrator is used to stabilize the tracking loop. In the tracking state, the error voltage integrator integrates the output error voltage of the tracking discriminator and sends the DC voltage to the compensation amplifier. The compensation amplifier generates a GVA signal based on the DC voltage. The GVA signal is used to charge the energy storage capacitor of the sawtooth wave generator. A monostable circuit can be used to reset the sawtooth wave to control the sawtooth wave modulation period.

6. The multi-mode composite altimeter according to claim 1, characterized in that: The signal processing board (15) comprises a signal processing circuit and a height data processing and interface circuit; The signal processing circuit is used to decode and track the ultrasonic height pulse signal, the laser height pulse signal and the beat signal respectively, and calculate the ultrasonic height, laser height and radio height information; The altitude data processing circuit is used to fuse radio altitude, ultrasonic altitude, and laser altitude according to an altitude fusion algorithm to calculate a composite altitude measurement with high reliability; The interface circuit is used to transmit the calculated composite altitude information to the flight control system.

7. The multi-mode composite altimeter according to claim 1, characterized in that: The ultrasonic transceiver module (221) comprises an ultrasonic chip circuit, an ultrasonic transmission conditioning circuit, an ultrasonic echo receiving and processing circuit, and a temperature detection circuit; The ultrasonic chip circuit uses the SB5227 ultrasonic ASIC chip, which contains an oscillator, a frequency divider, a microprocessor, a latch, and is compatible with split or integrated ultrasonic sensors. It is used to set the transmission power and the sensor's damping characteristic compensation coefficient to prevent aftershocks after the transmission cycle, and receives a frequency signal proportional to the ambient temperature. The ultrasonic emission conditioning circuit includes an ultrasonic generator and a counter. The generator is composed of two piezoelectric crystals and a resonance plate. It uses the resonance of the piezoelectric crystal to drive the surrounding air to vibrate. When the generator emits ultrasonic waves toward the ground, the counter starts timing at the same time as the emission. The ultrasonic waves immediately return when they hit the ground. The ultrasonic echo receiving and processing circuit includes an ultrasonic receiver. After the receiver receives the return wave, the counter immediately stops timing. The ultrasonic echo receiving and processing circuit transmits the echo signal to the ultrasonic chip circuit. The ultrasonic chip circuit converts the signal into a digital pulse signal and transmits it to the signal processing circuit. The temperature detection circuit is used to perform temperature compensation on the sound velocity and distance, thereby improving the measurement accuracy.

8. The multi-mode composite altimeter according to claim 1, characterized in that: The laser transceiver module (222) includes a laser transmitting circuit, a laser receiving circuit, a data signal processing circuit and a power supply filtering module; The laser emission circuit is composed of a sinusoidal signal generator, a semiconductor laser and a drive circuit. The laser emission circuit is used to convert the electrical signal into an optical signal and perform sinusoidal modulation of the semiconductor laser. The sinusoidal modulation is to add a high-precision sinusoidal signal to a stable bias current. The laser receiving circuit is composed of an avalanche diode and its signal amplification and filtering circuit, which is used to convert the optical signal into an electrical signal, amplify the signal, filter noise and reduce the phase deviation of the sinusoidal signal; The data signal processing circuit is composed of two high-frequency AD conversion chips and a comparator, which is used to control the phase difference and flight time timing of the modulation signal and measurement signal required for laser emission, and output the height measurement data to the signal processing circuit in the form of a digital pulse signal; The power filter module is used to convert the input +28V voltage into the +12V voltage required by the laser module and make the voltage stable and reliable.

9. The multi-mode composite altimeter according to claim 1, characterized in that: The C-band transmitting antenna (223) adopts a microstrip antenna structure and is used for transmitting radio frequency signals to the ground.

10. The multi-mode composite altimeter according to claim 1, characterized in that: The single antenna (21) is installed on the tail beam of the aircraft, is well grounded to the aircraft casing, and is connected to the transceiver via a radio frequency cable, and is used to receive signals reflected from the ground and transmit them to the transceiver (1).

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