UAV is the abbreviation of Unmanned Aerial Vehicle (Unmanned Aerial Vehicle), which is an unmanned aircraft using radio remote control equipment and self-provided program control devices, including unmanned helicopters, fixed-wing aircraft, multi-rotor aircraft, unmanned airships , Unmanned umbrella wing aircraft.
In a broad sense, it also includes adjacent space vehicles (20-100 km airspace), such as stratospheric airships, high-altitude balloons, and solar drones.
From a certain perspective, drones can complete complex aerial flight tasks and various load tasks under unmanned conditions, and can be regarded as "air robots". Among them, the flight control system, navigation system, power system, and communication link are the core technologies of the UAV system, and are the factors for the UAV manufacturers to obtain core competitiveness at this stage.
Below we focus on the role and development trends of the next four systems.
1. The flight control system is the "driver" of the drone-more precise and clearer
The flight control subsystem is the core system for the entire flight process of the drone to complete takeoff, aerial flight, mission execution and return to the field. The flight control is the core of the drone, which is equivalent to the driver's role for manned aircraft. One of the technologies. Flight control generally includes three parts: sensors, on-board computers, and servo actuation equipment. The functions implemented mainly include three categories: UAV attitude stabilization and control, UAV mission equipment management, and emergency control.
Among them, various sensors (including angular rate, attitude, position, acceleration, altitude and airspeed, etc.) assembled in large amounts are the basis of the flight control system and the key to ensuring the accuracy of the aircraft control. In different flight environments, different UAVs have different requirements for sensor configuration. The future requirements for drone situational awareness, identification of enemies and foes on the battlefield, and the ability of the region to conduct diplomatic warfare, etc., require unmanned aerial vehicles with higher detection accuracy and higher resolution. Therefore, a large number of domestic and foreign UAV sensors are used New technologies such as hyperspectral imaging, synthetic aperture radar, and UHF penetration are introduced.
2. The navigation system is the "eye" of the drone-multi-technology integration is the development direction
The navigation system provides the position, speed, and flight attitude of the reference coordinate system to the UAV, and guides the UAV to fly according to the designated route, which is equivalent to a pilot in a man-machine system. UAV-based navigation systems are mainly divided into non-autonomous (GPS, etc.) and autonomous (inertial guidance), but have the disadvantages of being vulnerable to interference and increasing error accumulation, and the future development of UAVs requires obstacle avoidance, materials or Weapons delivery, automatic approach and landing functions require high precision, high reliability, and high anti-jamming performance. Therefore, the combination of multiple navigation technologies, "inertia + multi-sensor + GPS + photoelectric navigation system" will be the direction of future development.
3. Power system-the turbine is expected to gradually replace the piston, and the new energy engine improves the endurance
Different UAVs have different requirements for power devices, but they all want small engines, low cost, and reliable operation:
The power unit currently widely used by drones is a piston engine, but the piston type is only suitable for low speed and low altitude small drones;
For single-use target aircrafts, suicide drones or missiles, a high thrust-to-weight ratio is required but the lifespan can be short (1-2h), and turbojet engines are generally used;
Low-altitude unmanned helicopters generally use turboshaft engines, and large drones with high altitude and long endurance generally use turbofan engines (US Global Eagle weighs 12t);
Micro UAVs (multi-rotors) generally use battery-driven motors, with a take-off mass of less than 10Kg and a battery life of less than one hour.
With the push-to-weight ratio of turbine engines, the continuous improvement of life, and the reduction of fuel consumption, turbines will replace pistons as the main power model of drones, and new energy motors such as solar energy and hydrogen energy are also expected to provide more durable survivability for small drones.
4. The data link is the "kite flying line"-the development of high speed and high bandwidth
Data link transmission system is one of the important technologies of unmanned aerial vehicles. It is responsible for the remote control, telemetry, tracking and positioning and sensor transmission of unmanned aerial vehicles. The uplink data link realizes the functions of telemetry and data transmission for the remote control of the unmanned aerial vehicle and the downlink data link. Most ordinary drones use customized line-of-sight data links, while medium-altitude and long-range drones use line-of-sight and over-the-horizon satellite data links.
The development of modern data link technology promotes the development of UAV data link in the direction of high speed, broadband, confidentiality, and anti-jamming, and the practical ability of drones will become stronger and stronger. With the increasing accuracy of airborne sensors, positioning, and the complexity of performing tasks, strong requirements are placed on the bandwidth of the data link. In the future, with the rapid development of airborne high-speed processors, it is expected that existing RF data will be available in a few years. The transmission rate of the chain will be doubled, and laser communication methods may also appear in areas with low all-weather requirements in the future.
Optical time-domain reflectometer (English name: optical time-domain reflectometer, OTDR) is an instrument that understands the uniformity, defect, fracture, and coupling of the optical fiber through the analysis of the measurement curve. It is made according to the principle of light backscattering and Fresnel reverse. It uses the backscattered light generated when light propagates in the optical fiber to obtain attenuation information. It can be used to measure optical fiber attenuation, connector loss, fiber fault location and understanding The loss distribution of the optical fiber along the length, etc., is an indispensable tool in the construction, maintenance and monitoring of the optical cable.
The optical time domain reflectometer will inject a series of optical bursts into the optical fiber for inspection. The method of inspection is to receive the optical signal from the same side of the incident wave, because the incident signal will be scattered and reflected back when it encounters a medium with a different refractive index. The intensity of the reflected light signal will be measured and is a function of time, so it can be converted into the length of the optical fiber.
The optical time domain reflectometer can be used to measure the length and attenuation of the optical fiber, including the fusion splice and transition of the optical fiber. It can also be used to measure the interruption point when the fiber is broken.
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