Introduction to UAV Systems. Mohammad H. Sadraey

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СКАЧАТЬ and recovery subsystems, air‐vehicle carriers, and other ground handling and maintenance equipment. A very simple generic UAV system is shown in Figure 1.1.

Figure 1.1 Generic UAV system

      1.3.1 Air Vehicle

      The air vehicle is the airborne part of the unmanned aerial system that includes the airframe, propulsion unit, flight controls, and electric power system. The air data terminal is mounted in the air vehicle, and is the airborne portion of the communications data link. The payload is also onboard the air vehicle, but it is recognized as an independent subsystem that often is easily interchanged with different air vehicles and uniquely designed to accomplish one or more of a variety of missions. The air vehicle can be a fixed‐wing airplane, rotary wing (single or multiple), or a ducted fan. Lighter‐than‐air vehicles are also eligible to be termed UAVs.

      1.3.2 Mission Planning and Control Station

      The MPCS, also called the GCS, is the operational control center of the UAV system where video, command, and telemetry data from the air vehicle are processed and displayed. These data are usually relayed through a ground terminal, which is the ground portion of the data link. The MPCS shelter incorporates a mission planning facility, control and display consoles, video and telemetry instrumentation, a computer and signal processing group, the ground data terminal, communications equipment, and environmental control and survivability protection equipment.

      The MPCS can also serve as the command post for the person who performs mission planning, receives mission assignments from supported headquarters, and reports acquired data and information to the appropriate unit, be it weapon fire direction, intelligence, or command and control, for example, the mission commander. The station usually has positions for both the air vehicle and mission payload operators to perform monitoring and mission execution functions.

      In some small UAS, the ground control station is contained in a case that can be carried around in a back‐pack and set up on the ground, and consists of little more than a remote control and some sort of display, probably augmented by embedded microprocessors or hosted on a ruggedized laptop computer.

At the other extreme, some ground stations are located in permanent structures thousands of miles away from where the air vehicle is flying, using satellite relays to maintain communications with the air vehicle. In this case, the operator’s consoles might be located in an internal room of a large building, connected to satellite dishes on the roof. A cut‐away view of a typical field MPCS for a long‐range UAV is shown in Figure 1.2.

Figure 1.2 Mission planning and control station for a long‐range UAV

      1.3.3 Launch and Recovery Equipment

      Launch and recovery can be accomplished by a number of techniques ranging from conventional takeoff and landing on prepared sites to vertical ascent/descent using rotary wing or fan systems. Catapults using either pyrotechnic (rocket) or a combination of pneumatic/hydraulic arrangements are also popular methods for launching air vehicles. Some small UAVs are launched by hand, essentially thrown into the air like a toy glider.

      Nets and arresting gear are used to capture fixed‐wing air vehicles in small spaces. Parachutes and parafoils are used for landing in small areas for point recoveries. One advantage of a rotary‐wing or fan‐powered vehicle is that elaborate launch and recovery equipment usually is not necessary. However, operations from the deck of a pitching ship, even with a rotary‐wing vehicle, will require hold‐down equipment unless the ship motion is minimal.

      1.3.4 Payloads

      Carrying a payload is the ultimate reason for having a UAV system, and the payload sometimes is the most expensive subsystem of the UAV. Payloads often include video cameras, either daylight or night (image‐intensifiers or thermal infrared), for reconnaissance and surveillance missions. Film cameras were widely used with UAV systems in the past, but are largely replaced today with electronic image collection and storage, as has happened in all areas in which video images are used. Currently, video cameras are the most popular payloads in UAVs.

If target designation is required, a laser is added to the imaging device and the cost increases dramatically. Radar sensors, often using a Moving Target Indicator (MTI) and/or synthetic aperture radar (SAR) technology, are also important payloads for UAVs conducting reconnaissance missions. Another major category of payloads is electronic warfare (EW) systems. They include the full spectrum of signal intelligence (SIGINT) and jammer equipment. Other sensors such as meteorological and chemical sensing devices have been proposed as UAV payloads.

      Armed UAVs carry weapons to be fired, dropped, or launched. “Lethal” UAVs carry explosive or other types of warheads and may be deliberately crashed into targets. As discussed elsewhere in this book, there is a significant overlap between UAVs, cruise missiles, and other types of missiles. The design issues for missiles, which are “one‐shot” systems intended to destroy themselves at the end of one flight, are different from those of reusable UAVs and this book concentrates of the reusable systems, although much that is said about them applies as well to the expendable systems.

      Another use of UAVs is as a platform for data and communications relays to extend the coverage and range of line‐of‐sight radio‐frequency systems, including the data links used to control UAVs and to return data to the UAV users.

      1.3.5 Data Links

      The data link is a key subsystem for any UAV. The data link for a UAV system provides two‐way communication (i.e., uplink and down link), either upon demand or on a continuous basis. An uplink with a data rate of a few kbps provides control of the air‐vehicle flight path and commands to its payload. The downlink provides both a low data‐rate channel to acknowledge commands and transmit status information about the air vehicle and a high data‐rate channel (1–10 Mbps) for sensor data such as a video camera and radar.

      The data link may also be called upon to measure the position of the air vehicle by determining its azimuth and range from the ground‐station antenna. This information is used to assist in navigation and in accurately determining air‐vehicle location (e.g., altitude). Other flight parameters, such as aircraft speed, climb rate, and direction, are often transmitted by a down link to MPCS.

      Data links require some kind of anti‐jam and anti‐deception capability if they are to be sure of effectiveness in combat.

      The ground data terminal is usually a microwave electronic system and antenna that provides line‐of‐sight communications, sometimes via satellite or other relays, between the MPCS and the air vehicle. It can be co‐located with the MPCS shelter or remote from it. In the case of the remote location, it is usually connected to the MPCS by hard wire (often fiber‐optic cables). The ground terminal transmits guidance and payload commands and receives flight status information (altitude, speed, direction, СКАЧАТЬ