Multi-mode composite altimeter

Abstract

The utility model discloses a multimode composite altimeter, which comprises a transceiver and antennas, the antennas comprise a single antenna and a combined antenna, and the combined antenna comprises an ultrasonic transceiver module, a laser transceiver module and a C-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 device 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] This utility model belongs to the field of instrumentation technology, specifically designing a multi-mode composite altimeter that can be used to measure the altitude of a drone above the ground. Background Technology

[0002] A radio altimeter is a flight instrument widely used in military and civilian aircraft. Its primary function is to measure the aircraft's altitude above the ground to ensure flight safety. Radio altimeters offer selectable frequency bands, enabling rapid and accurate altitude measurements, making them an indispensable key piece of equipment in the aviation field. With increasing awareness of aviation safety and continuous technological advancements, modern radio altimeters are gaining increasing attention from airlines and aircraft manufacturers, and are evolving towards greater accuracy, efficiency, and reliability, 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 its internal components are fixed by screws, grooves, cable clamps, and springs, the altimeter is prone to shaking during takeoff or landing due to airflow, which can easily damage internal parts and affect altitude measurement accuracy. The altimeter is highly susceptible to external environmental influences, resulting in poor reliability and safety.

[0004] Patent document CN200620049336.8 discloses a single-antenna radio altimeter, which includes an antenna, a circulator, a microwave transmitting unit, a microwave receiving unit, an intermediate frequency filter, a main amplifier, a microprocessor, and a triangular wave generator. While this single-antenna radio altimeter reduces the installation space required for the antenna, placing the antenna outside the altimeter housing results in drawbacks such as susceptibility to interference, low accuracy, and large altitude measurement errors. The altimeter antenna is also susceptible to interference, leading to lower altitude measurement accuracy; furthermore, the circulator within 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 actual altitude measurement, a temperature sensor on the signal processing module collects temperature data and performs temperature compensation. While this altimeter can address the accuracy degradation caused by external temperature drift, its temperature sensor is still affected by heat generated by other components inside the transceiver, resulting in significant temperature drift and large altitude measurement errors. Furthermore, the heat generated by other components inside the altimeter's transceiver interferes with the sensor's temperature data collection, indicating weak environmental adaptability and low altitude measurement accuracy. The large size of components such as the temperature sensor and oscillator in the altimeter also contributes to the overall increased size of the device.

[0006] Currently, drones fly over various terrains, including but not limited to jungles, rivers, oceans, mountains, and cities. Digital altimeters and radio altimeters cannot accurately measure altitude, leading to errors and erroneous altitude readings that compromise flight safety. Furthermore, during flight and takeoff / landing, the immaturity of single-antenna altimeter technology means that accuracy errors caused by antenna spacing cannot be eliminated at near-ground altitudes. The tracking issues associated with external slings during drone acceleration and deceleration cannot be completely eliminated. Additionally, the slant range error, multipath interference, and tracking harmonics caused by dual-antenna installations have not been fully resolved. All these factors contribute to errors in the altimeter's measurement of the actual altitude from the ground, posing a potential threat to safe drone flight. Utility Model Content

[0007] The purpose of this invention is to address the shortcomings of the prior art by providing a multi-mode composite altimeter to improve measurement accuracy, reduce size, lower power consumption, and enable real-time measurement of UAVs relative to the ground or sea surface in complex environments, thus ensuring their safe flight.

[0008] The technical approach to achieving the objective of this invention is as follows: By setting up a temperature detection circuit and a temperature compensation module, the temperature of the ambient air is measured, and the propagation speed of ultrasonic waves is corrected in real time to reduce the influence of temperature. Simultaneously, by setting heat dissipation fins on both sides of the transceiver, heat exchange between the outer casing and the air is facilitated, reducing the overall temperature of the transceiver and minimizing its impact, thereby improving ranging accuracy. The size of the altimeter is reduced by using a small-sized, low-power antenna, a low-power laser, and a piezoelectric crystal. The stability and safety of the altimeter are improved by changing the main structure and materials of the transceiver. Finally, the altimeter's measurement accuracy and the reliability of the measured data are improved by integrating radio altimetry, laser altimetry, and ultrasonic altimetry.

[0009] Based on the above ideas, the present invention provides a multi-mode composite altimeter, comprising: a transceiver and an antenna, wherein the transceiver includes a power board, a filter assembly, a microwave assembly, 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 the heat generated by the power board during operation on other components, while also facilitating the conduction of its heat to the housing.

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

[0012] The microwave component is mounted on the side wall of the housing to conduct heat directly to the housing for heat dissipation. The housing has scattering ribs on both sides for 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 by locking strips on both sides;

[0014] The housing and the cover plate are connected by an L-shaped overlap, and the middle part of the cover plate is connected to the front guide plate;

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

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

[0017] The ultrasonic transceiver module is used to calculate the height counting pulse signal of the ultrasonic wave and transmit it to the signal processing board.

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

[0019] The C-band transmitting antenna is used to transmit signals to the ground and receive the reflected signals through the single antenna, which are then transmitted to the microwave component. The signals are mixed with the radio frequency signals generated by the microwave component to generate beat signals, which are then transmitted 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, and calculates the ultrasonic altitude, laser altitude, and radio altitude information; then it calculates a highly reliable composite altimeter altitude and transmits it to the flight control system.

[0021] Preferably, the power board includes a power module and a filtering circuit. The power module is an input / output isolated DC-DC converter module that converts the +28V voltage into the +5V, +15V, -15V, and +30V voltages required for the transceiver to operate. The filtering circuit is connected to the output terminal of the power module to filter out ripple interference on the power line and ensure stable and reliable output voltage.

[0022] Preferably, the filtering component uses a low-frequency socket with filtering function, and has an internal electromagnetic compatibility protection circuit and a power characteristic protection circuit; the electromagnetic compatibility protection circuit is used to reduce electromagnetic interference damage to components and ensure the normal operation of electronic equipment; the power characteristic protection circuit is used to prevent excessive voltage or current from damaging the power supply and ensure the normal operation of the power supply.

[0023] Preferably, the microwave component includes a microwave oscillator, a cavity resonator detector, a low-noise preamplifier, and a mixer. The microwave oscillator is connected to a sawtooth wave generator on the servo board to generate a stable radio frequency signal. The cavity resonator detector consists of two independent dielectric resonator detectors. When the radio frequency signal enters the two dielectric resonator detectors, two sharp pulse voltages are output at their respective resonant frequencies for frequency offset self-calibration and calibration and calculation of the modulated sawtooth wave. The low-noise amplifier amplifies 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 comprises a mixer cutoff circuit, a high-pass filter, an equalization gain unit, a tracking discriminator, an error voltage integrator, a sawtooth wave generator, and a control discriminator circuit.

[0025] The mixer cutoff circuit is used to prevent or allow the beat signal to be transmitted to the tracking loop so that a self-test signal can be sent to perform BIT detection on the tracking loop;

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

[0027] The equalization gain unit is used to control the gain circuit to generate different gains for echo signals at different heights, which increase with the actual height, so as to ensure that long-distance signals can be sufficiently amplified and short-distance signals will not saturate due to excessive signal strength. The amplified beat signal is sent to both the control discriminator and the tracking discriminator.

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

[0029] The sawtooth wave generator is used to generate sawtooth waves, and the sawtooth wave modulation period is scanned from small to large until it enters the tracking state.

[0030] The tracking discriminator is used to output an error voltage. Once in tracking mode, the tracking discriminator will continuously track changes in altitude.

[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 energy storage capacitor of the sawtooth wave generator is charged through the GVA signal. 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 an altitude data processing and interface circuit; the signal processing circuit is used to decode and track the ultrasonic altitude pulse signal, the laser altitude pulse signal and the beat signal respectively, and calculate the ultrasonic altitude, laser altitude and radio altitude information.

[0033] 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 altimetry altitude with high reliability.

[0034] The interface circuit is used to transmit the calculated composite altitude information to the flight control system and other interconnection devices.

[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 dedicated integrated circuit chip, which includes an oscillator, frequency divider, microprocessor, latch, and adapter for split or integrated ultrasonic sensors. It is used to set the transmission power and the damping characteristic compensation coefficient of the sensor to prevent aftershocks after the transmission cycle and to receive frequency signals that are proportional to the ambient temperature.

[0037] The ultrasonic emission conditioning circuit includes an ultrasonic generator and a counter. The generator consists of two piezoelectric crystals and a resonant plate. It works by using the resonance of the piezoelectric crystals 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 return immediately when they hit the ground.

[0038] The ultrasonic echo receiving and processing circuit includes an ultrasonic receiver. After the receiver receives the echo, the counter immediately stops counting. 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.

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

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

[0041] The laser emitting circuit consists of a sinusoidal signal generator, a semiconductor laser, and a driving circuit. The laser emitting circuit is used to convert electrical signals into optical signals and to perform sinusoidal modulation of the semiconductor laser. The sinusoidal modulation is to apply a high-precision sinusoidal signal to a stable bias current.

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

[0043] The data signal processing circuit consists of two high-frequency AD conversion chips and a comparator, used to control the phase difference and flight time timing of the modulation signal and measurement signal required for laser emission, and outputs the altimeter data as a digital pulse signal to the signal processing circuit.

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

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

[0046] Preferably, the single antenna is mounted on the tail boom of the aircraft, is well grounded to the aircraft fuselage, and is connected to a transceiver via a radio frequency cable to receive signals reflected from the ground and transmit them to the transceiver.

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

[0048] 1. This utility model reduces the influence of temperature by incorporating a temperature detection circuit and a temperature compensation module into the ultrasonic module of the combined antenna to measure the ambient air temperature and correct the propagation speed of ultrasonic waves in real time. Simultaneously, the inclusion of heat dissipation fins in the transceiver allows for convective heat exchange between the outer casing and the air, lowering the overall temperature of the transceiver, reducing its impact, and improving the accuracy and reliability of the altimeter.

[0049] 2. This utility model reduces the power consumption of the altimeter by using a small-sized, low-power C-band transmitting antenna in the combined antenna and a low-power laser and piezoelectric chip in the laser module; at the same time, the modular and integrated self-test design in the servo board and signal processing board of the transceiver reduces the number of discrete components and the size of the altimeter.

[0050] 3. The transceiver housing of this utility model adopts a precision casting structure of aluminum alloy and is equipped with weight-reducing grooves and reinforcing ribs on the outside of the housing, which improves the structural strength. At the same time, by installing the filter components on the front guide plate, installing the microwave components on the side wall of the housing, and fixing the power board, servo board and signal processing board to the housing with locking strips on both sides, and then using an L-shaped overlapping method to connect the housing and the cover plate, the stability of the altimeter is improved.

[0051] 4. This utility model adopts a closed design for both the transceiver and the combined antenna, reducing electromagnetic compatibility gap leakage, preventing the transceiver and combined antenna from emitting electromagnetic interference and being affected by external electromagnetic interference, thus improving the electromagnetic compatibility of the altimeter; at the same time, since the power supply uses DC28V and is designed with filtering, isolation and shielding, it will not affect the safety of normal operators, thus improving the safety of the altimeter.

[0052] 5. This utility model improves the altimeter's accuracy and the reliability of altimeter data by employing 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 altimeter height. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the multi-mode composite height gauge structure according to an embodiment of the present invention;

[0054] Figure 2 This is a structural schematic diagram of the multi-mode composite height gauge from another angle according to an embodiment of this utility model;

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

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

[0057] Figure 5 This is a schematic diagram of the power board circuit of an embodiment of the present utility model;

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

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

[0060] Figure 8 This is a flowchart illustrating the calculation of an aircraft's altitude above 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 Implementation

[0062] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort should all fall within the protection scope of the present invention.

[0063] Please refer to the following: Figures 1 to 3 This is a multimode composite altimeter in 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 assembly 12, a microwave assembly 13, a servo board 14, a signal processing board 15, a housing 16, a cover plate 17, and a front guide plate 18.

[0065] Wherein: the power board 11 is installed on the side near the transceiver housing and is fixed by locking strips on both sides; the filter assembly 12 is installed on the front guide plate 18; the microwave assembly 13 is installed on the side wall of the housing; the servo board 14 and the signal processing board 15 are fixed to the housing 16 by locking strips on both sides; the housing 16 and the cover plate 17 are connected by an L-shaped overlapping method, and the middle part of the cover plate 17 is connected to the front guide plate 18;

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

[0067] The filter component 12 uses a low-frequency socket with filtering function and has an internal electromagnetic compatibility protection circuit and a power characteristic protection circuit. The electromagnetic compatibility protection circuit is used to reduce electromagnetic interference damage to components and ensure the normal operation of electronic equipment. The power characteristic protection circuit is used to prevent excessive voltage or current from damaging the power supply and ensure the normal operation of the power supply.

[0068] The microwave component 13 includes a microwave oscillator, a cavity resonator detector, a low-noise preamplifier, and a mixer. The microwave oscillator is connected to a sawtooth wave generator on the servo board to generate a stable radio frequency signal. The cavity resonator detector consists of two independent dielectric resonator detectors. When the radio frequency signal enters the two dielectric resonator detectors, two sharp pulse voltages are output at the resonant frequency respectively for frequency offset self-calibration and calibration and calculation of the modulated sawtooth wave. The low-noise amplifier amplifies 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 mainly consists of a mixer cutoff circuit, a high-pass filter, an equalization gain circuit, a tracking discriminator, an error voltage integrator, a sawtooth wave generator, and a control discriminator. The mixer cutoff circuit is used to prevent or allow beat signals to be transmitted to the tracking loop, so that a 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 equalization gain circuit controls the gain circuit to generate different gains for echo signals at different altitudes, increasing with the actual altitude, to ensure that long-distance signals are sufficiently amplified and that short-distance signals do not saturate due to excessive signal strength. The amplified beat signal is simultaneously sent to the control discriminator and the tracking discriminator. The control discriminator determines whether to enter the tracking state based on the input signal-to-noise ratio (SNR), entering the search state when the input SNR does not meet the tracking conditions. When the detection result of the frequency discriminator exceeds the set threshold, the frequency discriminator controls the sawtooth wave generator to stop scanning and enter the tracking state. The modulation period of the sawtooth wave is adjusted according to the error voltage to keep the beat tracking signal constant. The sawtooth wave generator is used to generate sawtooth waves, and the modulation period of the sawtooth wave is scanned from small to large until the tracking state is entered. The tracking frequency discriminator outputs the error voltage. After entering the tracking state, the tracking frequency discriminator will continuously track the change in altitude. 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 according to the DC voltage. The energy storage capacitor of the sawtooth wave generator is charged through the GVA signal. A monostable circuit can be used to reset the sawtooth wave to control the modulation period of the sawtooth wave.

[0070] The signal processing board 15 includes a signal processing circuit and an altitude data processing and interface circuit, which is 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 composite altimeter altitude with high reliability, and transmit it to the flight control system and other cross-linking devices.

[0071] Both the individual antenna 21 and the combined antenna 22 are connected to the transceiver via radio frequency cables; and the individual 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, which is used to calculate the height counting pulse signal of the ultrasonic wave and transmit it to the signal processing board 15.

[0074] The laser transceiver module 222 is used to measure the laser altitude counting pulse signal and transmit it to the signal processing board. It includes a laser emitting circuit, a laser receiving circuit, a power supply filtering module, and a data signal processing circuit. The laser emitting circuit consists of a sine wave generator, a semiconductor laser, and a driving circuit. The laser emitting circuit converts the electrical signal into an optical signal and performs sinusoidal modulation of the semiconductor laser. The sinusoidal modulation involves applying a high-precision sinusoidal signal to a stable bias current. The laser receiving circuit consists of an avalanche diode and its signal amplification and filtering circuit. It converts the optical signal into an electrical signal, amplifies the signal, filters noise, and reduces the phase shift of the sinusoidal signal. The power supply filtering module converts the input +28V voltage to the +12V voltage required by the laser module and ensures stable and reliable voltage. The data signal processing circuit consists of two high-frequency AD conversion chips and a comparator. It controls the phase difference and time-of-flight timing of the modulation signal and measurement signal required for laser emission, and is used to measure the laser altitude counting 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 receive the reflected signals through a single antenna 21 and transmit them to the microwave component 13. The signals are mixed with the radio frequency signals generated by the microwave component 13 to generate beat signals, which are then transmitted to the signal processing circuit.

[0076] The signal processing circuit described above is used to decode and track the ultrasonic height pulse signal, laser height pulse signal and 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 reliability; the interface circuit is used to transmit the calculated composite altitude information to the flight control system and other cross-linking devices.

[0078] Reference Figure 5 The 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 uses an SB5227 ultrasonic dedicated integrated circuit chip, which includes an oscillator, a frequency divider, a microprocessor, a latch, and an adapter for separate or integrated ultrasonic sensors. It is used to set the transmission power and the damping characteristic compensation coefficient of the sensor to prevent aftershocks after the transmission cycle and to receive frequency signals proportional to the ambient temperature. The ultrasonic transmission conditioning circuit includes an ultrasonic generator and a counter. The generator consists of two piezoelectric crystals and a resonant plate. It works by using the resonance of the piezoelectric crystals to drive the vibration of the surrounding air. When the generator emits ultrasonic waves to the ground through the transmitter head, the counter starts timing at the same time. The ultrasonic waves return immediately upon hitting 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. The ultrasonic echo receiving and processing circuit transmits the echo signal to the ultrasonic chip circuit, which 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 for sound speed and distance, thereby improving measurement accuracy.

[0079] Reference Figure 6 The power board 11 includes power supply and filtering circuits. The power module uses two input / output isolated DC-DC converter modules. The first power module converts +28V voltage to +5V, +15V, and -15V voltages. The second power module converts +28V to +30V. Meanwhile, the filtering circuit is connected to the output terminal 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 height data processing and interface circuit in the signal processing board 15 are operated by a microprocessor, and are implemented as follows:

[0081] The microprocessor determines the fault type by searching for reset and searching / tracking detection;

[0082] The microprocessor completes the self-test through calibration control and mixer cutoff, and puts the height measuring component into a 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 ultrasonic ranging information, and performs counting measurement based on the input sawtooth wave period signal and cavity pulse signal. The radio altitude information is calculated through the measurement and output through the interface circuit.

[0084] The microprocessor controls the transmission signal of the microwave component VCO by calibrating the amplitude and average voltage of the sawtooth wave, thereby keeping the center frequency and frequency deviation of the transmission signal constant.

[0085] Reference Figure 8 The implementation for calculating the aircraft's altitude above the ground in this example is as follows:

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

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

[0088] When the altimeter data is between 0m and 2m, the three types of data, namely radio altimeter data, laser altimeter data, and ultrasonic altimeter data, are fused to obtain accurate altitude data, which is then transmitted to the flight control system and the interconnection equipment.

[0089] When the altimeter data is between 2m and 100m, the radio altimeter data and the laser altimeter data are fused together to obtain accurate altitude data, which is then transmitted to the flight control system and the interconnection equipment.

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

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

[0092] I. Testing environment: including ground environment, forest environment, and lake environment.

[0093] II. Test Content

[0094] 1. Aircraft testing in ground environments:

[0095] The test covered several states of the aircraft, from takeoff and hovering at low altitude, to gradual ascent, to hovering at a set altitude for a period of time, and finally to landing. Specifically, during low-altitude hovering, altitude data was obtained using radio altimetry, laser altimetry, and ultrasonic altimetry, and these three types of data were fused together. During ascent, hovering, and descent, altitude data was obtained using radio altimetry and laser altimetry, and these two types of data were fused together.

[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 merges the two types of data.

[0098] 3. Aircraft testing in a lake environment:

[0099] After the aircraft entered the lake environment, it used radio altimetry and laser altimetry to obtain altitude data, and then fused the two types of data.

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

[0101] from Figure 9 It is evident that during the aircraft's testing in the ground environment, the fused data was largely consistent with the laser data, radio data, and ultrasonic data. During the aircraft's testing in the forest environment, the laser data and radio data were affected by interference factors such as leaves, resulting in errors, which the fused data could reduce. During the aircraft's testing in the lake environment, the fused data was largely consistent with the radio data. Subsequently, 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 UAVs relative to the ground or sea surface in complex environments, ensuring their safe flight.

[0103] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the description and drawings of this utility model, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A multi-mode composite height gauge, characterized by, include: The transceiver (1) and antenna (2) include a power board (11), a filter assembly (12), a microwave assembly (13), a servo board (14), a signal processing board (15), a housing (16), a cover plate (17), and a front board (18). The power board (11) is installed on one side close to the housing (16) and fixed by locking strips on both sides to reduce the impact of the heat generated by the power board (11) during operation on other components, and at the same time facilitates the conduction of its heat to the housing. The filter assembly (12) is mounted on the front guide plate (18); The microwave component (13) is installed on the side wall of the housing (16) to conduct heat directly to the housing (16) for heat dissipation. The housing (16) is provided with scattering ribs on both sides for heat exchange between the outside of the housing and the air. The servo board (14) and the signal processing board (15) are fixed to the housing (16) by locking strips on both sides; The housing (16) and the cover plate (17) are connected by an L-shaped overlap, and the middle part 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) includes: 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 calculate the height counting pulse signal of the ultrasonic wave and transmit it to the signal processing board (15). The laser transceiver module (222) is used to measure the height counting pulse signal of the laser and transmit it to the signal processing board (15); The C-band transmitting antenna (223) is used to transmit signals to the ground and receive the reflected signals through the single antenna (21), which are then transmitted to the microwave component (13) to generate radio frequency signals. This generates beat signals, which are then transmitted to the signal processing board (15). The signal processing board (15) decodes and tracks the ultrasonic altitude counting pulse signal, the laser altitude counting pulse signal and the beat signal respectively, and calculates the ultrasonic altitude, laser altitude and radio altitude information; then it calculates the composite altimeter altitude with high reliability and transmits it to the flight control system.

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

3. The multi-mode compound height gauge of claim 1, wherein: The filter component (12) adopts a low-frequency socket with filtering function, and is equipped with an electromagnetic compatibility protection circuit and a power 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 characteristic protection circuit is used to prevent excessive voltage or current from damaging the power supply and ensure the normal operation of the power supply.

4. The multi-mode compound height gauge of claim 1, wherein: The microwave component (13) includes a microwave oscillator, a cavity resonator detector, a low-noise preamplifier, and a mixer. The microwave oscillator is connected to a sawtooth wave generator on the servo board to generate a stable radio frequency signal. The cavity resonator detector consists of two independent dielectric resonator detectors. When the radio frequency signal enters the two dielectric resonator detectors, two sharp pulse voltages are output at the resonant frequency respectively for frequency offset self-calibration and calibration and calculation of the modulated sawtooth wave. The low-noise amplifier amplifies 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 compound height gauge of claim 1, wherein: The servo board (14) consists of a mixer cutoff circuit, a high-pass filter, an equalization gainer, a tracking discriminator, an error voltage integrator, a sawtooth wave generator, and a control discriminator circuit. The mixer cutoff circuit is used to prevent or allow the beat signal to be transmitted to the tracking loop so that a 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 equalization gain unit is used to control the gain circuit to generate different gains for echo signals at different heights, which increase with the actual height, so as to ensure that long-distance signals can be sufficiently amplified and short-distance signals will not saturate due to excessive signal strength. The amplified beat signal is sent to both the control discriminator and the tracking discriminator. The frequency discriminator is used to determine whether to switch to the tracking state based on the input signal-to-noise ratio. When the input signal-to-noise ratio does not meet the tracking conditions, it enters the search state. When the detection result of the frequency discriminator exceeds the set threshold, the frequency discriminator controls the sawtooth wave generator to stop scanning and enter the tracking state. The modulation period of the sawtooth wave is adjusted according to the error voltage to keep the beat tracking signal constant. The sawtooth wave generator is used to generate sawtooth waves, and the sawtooth wave modulation period is scanned from small to large until it enters the tracking state. The tracking discriminator is used to output an error voltage. Once in tracking mode, the tracking discriminator will continuously track changes in altitude. 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 energy storage capacitor of the sawtooth wave generator is charged through the GVA signal. A monostable circuit can be used to reset the sawtooth wave to control the sawtooth wave modulation period.

6. The multi-mode compound height gauge of claim 1, wherein: The signal processing board (15) includes signal processing circuitry and high-resolution data processing and interface circuitry; The signal processing circuit is used to decode and track the ultrasonic height pulse signal, laser height pulse signal and 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 the altitude fusion algorithm to calculate a composite altimetry altitude with high reliability. The interface circuit is used to transmit the calculated composite altitude information to the flight control system.

7. The multi-mode compound height gauge according to claim 1, characterized in that: The ultrasonic transceiver module (221) includes an ultrasonic chip circuit, an ultrasonic emission conditioning circuit, an ultrasonic echo receiving and processing circuit, and a temperature detection circuit. The ultrasonic chip circuit uses the SB5227 ultrasonic dedicated integrated circuit chip, which includes an oscillator, frequency divider, microprocessor, latch, and adapter for split or integrated ultrasonic sensors. It is used to set the transmission power and the damping characteristic compensation coefficient of the sensor to prevent aftershocks after the transmission cycle and to receive frequency signals that are proportional to the ambient temperature. The ultrasonic emission conditioning circuit includes an ultrasonic generator and a counter. The generator consists of two piezoelectric crystals and a resonant plate. It works by using the resonance of the piezoelectric crystals 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 return immediately when they hit the ground. The ultrasonic echo receiving and processing circuit includes an ultrasonic receiver. After the receiver receives the echo, the counter immediately stops counting. 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 for sound speed and distance, thereby improving measurement accuracy.

8. The multi-mode compound height gauge of claim 1, wherein: The laser transceiver module (222) includes a laser emitting circuit, a laser receiving circuit, a data signal processing circuit, and a power filtering module; The laser emitting circuit consists of a sinusoidal signal generator, a semiconductor laser, and a driving circuit. The laser emitting circuit is used to convert electrical signals into optical signals and to perform sinusoidal modulation of the semiconductor laser. The sinusoidal modulation is to apply a high-precision sinusoidal signal to a stable bias current. The laser receiving circuit consists of an avalanche diode and its signal amplification and filtering circuit, which is used to convert the optical signal into an electrical signal, and to amplify the signal, filter noise, and reduce the phase shift of the sinusoidal signal. The data signal processing circuit consists of two high-frequency AD conversion chips and a comparator, used to control the phase difference and flight time timing of the modulation signal and measurement signal required for laser emission, and outputs the altimeter data as a digital pulse signal to the signal processing circuit. The power filtering module is used to convert the input +28V voltage into the +12V voltage required by the laser module and to make the voltage stable and reliable.

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

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

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