Functions and Development Trends of Four Core UAV Systems

Abstract

Unmanned Aerial Vehicles (UAVs) can perform complex aerial flight missions and payload tasks without onboard pilots, and can be regarded as "aerial robots". The flight control system, navigation system, power system and data link are core technologies of UAV platforms, which constitute the key core competitiveness for UAV manufacturers at the current stage.

UAV stands for Unmanned Aerial Vehicle. It refers to unpiloted aircraft controlled by radio remote-control equipment and onboard programmed controllers, including unmanned helicopters, fixed-wing aircraft, multi-rotor vehicles, unmanned airships and paraglider vehicles. In a broader sense, it also covers near-space vehicles operating within 20–100 km altitude, such as stratospheric airships, high-altitude balloons and solar-powered UAVs.

A UAV can complete sophisticated flight and payload missions without pilots, earning it the name "aerial robot". Flight control, navigation, power system and data link serve as four core technologies and major competitive factors for UAV enterprises. This article focuses on the functions and development trends of these four systems.

1. Flight Control System: The "Pilot" of UAVs

The flight control subsystem is the core system supporting the whole flight cycle including takeoff, cruising, mission execution and recovery. Equivalent to the pilot on manned aircraft, it represents one of the most critical UAV technologies. A flight control system generally consists of sensors, onboard computer and servo actuators. Its main functions cover UAV attitude stabilization and control, mission payload management and emergency control.

Various onboard sensors (angular rate, attitude, position, acceleration, altitude, airspeed sensors, etc.) form the foundation of flight control and determine flight control accuracy. Sensor configurations vary according to flight environments and application scenarios. Future requirements such as battlefield situational awareness, friend-or-foe identification and standoff combat demand higher detection precision and resolution. Therefore, new technologies including hyperspectral imaging, synthetic aperture radar (SAR) and ultrahigh-frequency penetration detection will be widely adopted in UAV sensors.

2. Navigation System: The "Eyes" of UAVs, Multi-sensor Fusion as Main Trend

The navigation system provides UAVs with position, velocity and attitude data under reference coordinate frames, guiding the aircraft along pre-planned routes, similar to a navigator in manned aircraft. UAV onboard navigation systems fall into two categories: non-autonomous navigation (e.g. GPS) and autonomous inertial navigation. Non-autonomous navigation is vulnerable to interference, while inertial navigation suffers from accumulated errors over time. Future UAVs require obstacle avoidance, cargo or weapon delivery, automatic landing and other capabilities, which demand high precision, reliability and anti-interference performance. Thus, an integrated navigation scheme combining inertial navigation, multi-sensors, GPS and electro-optical navigation will become the mainstream development direction.

3. Power System: Turbine Engines to Gradually Replace Piston Engines; New Energy Motors Improve Endurance

UAVs for different missions have different requirements for power units, while the general expectations are small size, low cost and high reliability.

• Piston engines: widely used currently, mainly for low-speed and low-altitude small UAVs.
• Turbojet engines: high thrust-to-weight ratio with short service life (1–2 hours), suitable for targets, loitering munitions and missiles.
• Turboshaft engines: commonly adopted by low-altitude unmanned helicopters.
• Turbofan engines: deployed on large high-altitude long-endurance UAVs, such as the US Global Hawk (12 tons).
• Battery-powered electric motors: applied to micro multi-rotor UAVs, usually with takeoff weight below 10 kg and flight endurance less than one hour.

As turbine engines achieve higher thrust-to-weight ratio, longer service life and lower fuel consumption, turbine power will gradually replace piston engines as the primary power option for UAVs. New energy motors driven by solar energy, hydrogen energy and other sources are expected to extend flight duration for small UAVs.

4. Data Link: The Control Tether, Evolving toward High Bandwidth

The data link transmission system is a vital UAV technology. It undertakes remote control, telemetry, tracking & positioning and sensor data transmission. The uplink delivers remote control commands, while the downlink transmits telemetry data and sensor information. Ordinary UAVs mostly adopt customized line-of-sight data links. Medium/high-altitude long-endurance UAVs combine line-of-sight links and beyond-line-of-sight satellite communication links.

Modern data link technologies push UAV communication toward high speed, wide bandwidth, encryption and anti-jamming, improving overall practicability. Rising precision of onboard sensors and growing mission complexity impose greater bandwidth demands. It is predicted that transmission rates of existing RF data links will double in the coming years. Laser communication may be adopted in scenarios with less stringent all-weather requirements.