Early Appearance

This study encompasses the engineering analysis of Airstream, a flying vehicle developed within the framework of Urban Air Mobility as an alternative transportation solution, equipped with a hydrogen fuel cell and dual-mode mobility capability, and possessing high maneuverability. Airstream is equipped with a hybrid propulsion system that offers near-zero emission values, based on a sustainability-focused transportation approach. For ground mode, an electric motor with a power of 178 kW is used, while for vertical takeoff and flight mode, eight independent electric motors with a power of 40 kW each are utilized. The hydrogen fuel cell, which forms the basis of the hybrid system, provides high efficiency throughout the mission profile thanks to battery-supported energy sharing. In the design, biomimicry and symmetrical layout principles have been adopted, and especially through the integration of steerable propellers into the wheel hubs, an effective vertical takeoff/landing performance has been achieved even in confined spaces. The vehicle can respond dynamically during land-air transitions thanks to its jump-assisted active suspension system; flight stability is maintained through gyroscopic stabilization and autonomous orientation control systems. The carbon fiber composite body and titanium alloy wheels used in the structural system both increase the load capacity and contribute to overall energy efficiency by reducing the system's weight. Flight control is provided in an integrated manner with multi-layered navigation systems such as GNSS, VOR/DME, ILS, and TCAS through a central flight computer developed by ASELSAN. Additionally, safety elements such as fire detection and suppression modules, parachute-assisted emergency landing systems, and electromagnetic protection ensure the integrity of the system. Airstream offers a concrete engineering solution for the smart and sustainable transportation systems of the future with its high performance, eco-friendly structure, safety-focused system design, and technological components. Prototyping and flight tests will guide the integration of this concept into commercial applications.

This article presents a Fault Tolerant Control (FTC) scheme for an octoplane UAV, a fixed-wing unmanned aerial vehicle (UAV) equipped with eight vertical rotors, using sliding mode control (SMC) allocation. The proposed approach requires the design of only a single baseline controller that is effective under fault-free and fault/failure scenarios. The octoplane, a hybrid dual-system UAV (a fixed-wing aircraft with vertical takeoff and landing (VTOL) capabilities), presents unique challenges and opportunities due to its actuator redundancy. The scheme fully exploits the octoplane’s redundant vertical rotors and additional control surfaces, including the elevator, rudder, and independently operated ailerons, to manage total actuator faults/failures during cruise flight. The approach utilises sliding mode control with a control allocation (CA) strategy to redistribute control signals in the case of actuator failure. Simulation results based on a nonlinear model of the octoplane are presented at the end of the article to demonstrate the effectiveness of the proposed scheme. The paper commences with an introduction that includes a general review of the SMC Method and dual-system UAVs, specifically an octoplane configuration, highlighting the significance of FTC in improving UAV stability and the benefits of including extra actuator redundancy in the FTC design. The paper then presents an analysis of the equations of motion for an octoplane UAV, setting the foundation for examining the FTC of cruise mode. Subsequently, it introduces the SMC design process and explains its implementation of FTC. In cruise mode, the proposed SMC-CA method exhibits no performance degradation in the event of fault/failure compared to fault-free cases. The scheme demonstrates the effective combination of CA and SMC methods to an octoplane UAV during cruise flight.