Company: Linear Technology Corporation (currently affiliated with Analog Devices)
Author: Military Aviation Marketing Manager Steve Munns
introductionModern unmanned military systems have become an integral part of the world's armed forces, and the defense industry continues to intensively develop such systems to enable them to perform a wide range of attacks, surveillance, and operational support. The unmanned operating system is perhaps the most dynamic area of ​​the defense industry today, with annual global spending of more than $5.5 billion, and by 2024 it is expected to be close to $10 billion [1].
The surprising aspect of the Unmanned Aerial Vehicle (UAV) field is the wide range of systems, from some nano-UVs (NUAV) weighing less than 20 grams to medium-sized UAVs, such as quality. The Watchkeeper of 450 kg with a payload capacity of 150 kg until the MQ-9 Reaper (formerly known as Predator B) with a take-off weight of more than 5,000 kg, spanning The variety and variety are amazing.
UAV Size, Weight and Power (SWaP) are key factors to consider when balancing their performance and mission life. There are a large number of electronic systems that can be used, but in this article, the focus when considering an electronic system will fall into the following areas:
· Airborne safety and autonomous operation
· Sensor and data processing
· Communication and information security
· Power Systems
Introduction to early unmanned operating systemsThe origins of modern UAVs can be traced back more than 100 years, but radio-controlled drones used as aerial target combat exercises in the 1930s may be considered the most famous UAV originator. More than 400 of these aircraft were built in the United Kingdom. They were known as the "Bee King" and it was said that the term "drone" was born for this type of aircraft. This type of aircraft requires that the flight is always within the line of sight of the pilot of the remotely piloted aircraft. But not long after, people began to experiment with autonomous flights beyond the line of sight. In 1940, Edward M. Sorensen filed a patent for his ground station invention, in which frequency modulation techniques were used to control the aircraft and read back flight information outside the line of sight. The reason for this patent is that it is recognized that there is a need for a mode that automatically prevents failures, keeps the aircraft flying flat, and at the same time establishes a backup control system.
With the development of wartime weapon payloads and the subsequent development of reconnaissance platforms in the 1950s and 1960s, the complexity of unmanned military systems has also increased. The Ryan drone in the early 1960s used a basic guidance system consisting of a programmable timer, a gyrocompass and an altimeter that determined the departure altitude, heading and flight time. The aircraft also provides reverse and parachute assisted landing functions. Although these are fairly basic functions, the strategic significance of obtaining images with film cameras and the advantages of semi-autonomous systems are easy to see, so people want to work together for further development.
Air flight safety and autonomous operationObviously, flight safety issues are crucial, and there has been extensive debate on this issue to determine how to control the sky so that the presence of UAV does not affect the safety of existing air traffic, while at the same time making military and civilian UAVs Application development is not restricted.
Small UAVs flying in line of sight rely on pilots of remotely piloted aircraft to determine if a collision will occur, while larger UAVs operating autonomously or semi-autonomously need complex detection and avoidance systems to avoid air collisions. Various sensors are being developed for this purpose, such as modifying conventional aircraft transponders, visual and infrared cameras, Light DetecTIon and Ranging (LiDAR) systems, and conventional radar systems. Converting data from these sensor systems into images that reflect the environment in which they are located, then making flight decisions autonomously, requires very complex software and hardware resources, and for UAVs sharing civil airspace, it is also necessary to meet existing Run on the premise of the agreement. When flying in friendly airspace, using ground-based radar and traffic mapping resources to reduce the complexity of the airborne system and expand the scope of monitoring may be an option, but in this way, on data link reliability, delay and other issues Make a compromise. The ASTREA program shows that autonomous detection and evasion techniques can be used, but this technology is used on Jetstream aircraft that do not have the power, size and weight limitations of the UAV. Adjusting this technology to make it available to most UAVs is a big challenge, but with advanced field-programmable gate arrays (FPGAs), digital signal processing (DSP), and high-performance analog electronics, this technology can be used. Achieve miniaturization. Powering such electronic systems is not a simple task. FPGAs require stringent power supply accuracy and low voltage and high current. This requires careful design of the power supply chain to minimize power consumption and heat generation. One approach is to use Digital Power System Management (PSM) technology, which reduces power consumption by dynamically adjusting voltage and frequency, helping to extend the mission life of smaller UAVs. PSM also improves reliability and provides remote control and monitoring capabilities, as well as energy usage records and "black box" fault logging.
Figure 1: Digital Power System Management
Sensor and data processingEven the smallest, manually activated NUAV can carry multiple cameras and cameras to perform surveillance tasks, and multiple versions of the MQ-9 Reaper can meet a variety of hunting and surveillance needs. The version carrying the weapon may carry a camera, an infrared night vision camera, and a synthetic aperture radar (SAR) used in the presence of clouds or smoke, as well as a laser range finder and target illumination system for munitions. A version that provides bait and jamming functionality has also been developed, while a tactical data link system can send target and image data directly to a manned aircraft. More development work is expected in the field of Signal Intelligence (SIGINT), and with the advancement of signal intelligence systems, longer versions of the voyage will provide more than 40 hours of mission time. Due to the rapid increase in airborne sensors and the prolonged mission life, a large amount of data must be generated, which must be compressed and stored or sent over real-time data links, which is bound to lead to some trade-offs such as bandwidth, quality and possible Loss of image data.
Each additional new payload capability increases the burden on the power system. Fortunately, however, advances have been made in the development of printed circuit board-level power solutions. Power density has improved significantly in recent years, and Linear Technology's μModule® (micromodule) regulator solution is an improvement. Technology. Each small module contains a complete high-efficiency power supply that is sized for applications where dimensional requirements are critical and is highly reliable. Figure 2 shows an example.
Figure 2: LTM4644 μModule Regulator
Communication and information securityThe UAV communication link can be divided into two parts:
• Flight Control Data Link - Used for remote command (uplink) and telemetry (downlink) information to monitor the UAV when the UAV responds to operator commands or autonomously performs mission planning in accordance with GPS coordinates. In general, a 56 kbps link using spread spectrum technology can meet the needs of a flight control data link, and the uplink can be protected with a 128-bit encryption algorithm and forward error correction.
• Communication link that transmits payload sensor information – seen as a separate communication link, HD video may require up to 10 Mbps of bandwidth while running COFDM, MPEG-4 or similar modulation schemes. Large UAVs such as the Reaper will typically use leased dedicated satellite trunk lines (Ku bands) and terrestrial (C-band) communication lines, with plenty of room for large antennas, while other types of drones may be industrial, scientific, and Operating in the medical (ISM) band, such as the 2.4 GHz (WLAN) and 5.8 GHz bands.
Integration with air traffic control systems and protocols is another obstacle to achieving full autonomous operation of the UAV, as UAVs need to respond to voice commands, provide heading and flight level information, and confirm acceptance of orders via VHF radio channels and synthetic voice confirmation systems. .
Information security risks include intentional or accidental interference; impersonation or interception of commands and control signals; communication channel attenuation. In conventional manned flight, in order to avoid any very close airborne objects, the pilot can immediately control the aircraft. Obviously, in the case of UAVs, the pilot always relies on the communication link and the stable operation of the onboard sensors.
The risk can always be mitigated. Even a very small UAV flying in accordance with a set of GPS coordinates can raise the altitude to recover lost GPS signals and automatically return to the base station when the departure time limit is reached. As a contingency measure, the anti-fraud GPS system combined with the GPS receiver and inertial measurement unit, statistical analysis of the received GPS signal also helps determine if someone is trying to deceive the system.
Of course, all of these communication systems require power, and sensitive radio receivers require some very low-noise power supplies so that the radio sensitivity is not reduced by the power supply. New chip process technologies and novel IC design methods have led to a series of groundbreaking products that offer unprecedented levels of efficiency and low noise, such as the LT8640 Silent Switcher® and LT3042 ultra-low noise, ultra-high PSRR RF linear regulator.
Figure 3: LT8640 Silent Switcher Regulator
Power SystemsAs noted earlier in this article, some IC-level power technology advancements have supported continuous changes in UAV and sensor payloads, but the choice of onboard power source is also a central factor influencing overall performance. As people become more focused on developing lower-cost, smaller-sized, lighter-weight UAVs, the attractiveness of internal combustion-type power sources is reduced, and fuel cell technology is becoming a possible choice, especially for long battery life and low average power requirements. In terms of the task.
The Puma series of small UAVs are testing a fuel cell that extends flight time from 150 minutes (when LiSO2 batteries are used) to nearly 5 hours. The entire fuel cell system weighs about 2 kilograms and the power to weight ratio is about 1kW. /kilogram.
Figure 4: Power to weight ratio of the UAV power source
Power-to-Weight RaTIo: power to weight ratio
Solar PV: Solar Photovoltaic Cell
Lithium-Ion Battery Types: Lithium-Ion Battery
Fuel Cells: Fuel Cells
Piston/Radial Engines: Piston / Radial Engine
Turbofan/Turboprop Engines: turbofan / turboprop engine
Increasing Complexity and Cost: Complexity and cost increase
The position of the fuel cell is environmentally friendly between the battery and the internal combustion engine solution, but it does face some fuel handling and storage problems, but it can be overcome by storing particulate hydrogen in a replaceable fuel cartridge.
Small UAVs and NUAVs are most likely to continue to use lithium-ion batteries, depending on the configuration, allowing a NUAV to fly for approximately 30 minutes with a single battery. Longer battery life and larger models will require a multi-cell design that benefits from battery capacity balancing with ICs such as the LTC3300, which maximizes system uptime. UAVs with high flying heights and acting as pseudo-satellites, such as UAVs being developed by Google and other companies and intended to provide Internet services in the future, can also replace batteries with solar power. Such systems need to remain reliable in environments where enhanced radiation may cause single-event upsets, so the complexity will increase, and the characteristics of the ICs used may need to be specified and specifically tested.
in conclusionUnmanned operating systems now play an integral role in the armed forces, and the massive funding provided by the military has facilitated the rapid development of such systems, with a focus on smaller, less expensive UAV systems.
As sensor payloads and UAV platform electronics become more complex, the efficiency of the power chain and onboard power sources is critical to providing high enough operational performance, and new IC power solutions are helping to achieve SWaP targets. .
High-flying UAVs and very long-lived missions are pushing for new power supplies such as solar and fuel cells, and the use of new power supplies means new ICs.
Reference material[1] http://TIon/press-releases/118-2014-uav-press-release
Facade Display,Led Outdoor Display Screen,Low Power Led Light Buried Lamp,Soft-Panel Stage Lighting
Kindwin Technology (H.K.) Limited , https://www.ktlleds.com