Takeshi Tsuchiya

System Identification of Small UAVs with MEMS-based Avionics

A new MEMS-based small, light, and cost-effective avionics is proposed in order to improve the current situation of system identification of small unmanned aerial vehicles (UAVs), which mostly depends on difficult wind tunnel tests. The avionics is capable of gathering navigation, wind, and control input data accurately. Flight tests with a small UAV are conducted, and its longitudinal stability derivatives are obtained accurately using flight data obtained by the avionics and system identification techniques.

Multi-Objective, Multidisciplinary Design Optimization of TSTO Space Planes with RBCC Engines

A fully-reusable two-stage-to-orbit (TSTO) launch vehicle with ethanol-fueled rocketbased combined cycle (RBCC) engines is a promising option for future space transportation that is currently studied in Japan. In this paper, a conceptual design study is conducted for such a vehicle using a multi-objective, multidisciplinary design optimization (MDO) technique. An MDO framework considering the coupling between vehicle geometry, propulsion system, aerodynamics, and flight trajectory is constructed, and they are optimized simultaneously with the aim of maximizing the payload mass, minimizing the gross mass of the combined vehicle (booster and orbiter), and minimizing the horizontal takeoff velocity. This multi-objective optimization enables a more comprehensive and exploratory design study compared with the gross-mass minimization problem subject to a predetermined mission plan and a fixed takeoff-velocity constraint. The optimization is executed via a novel algorithm, and a set of Pareto optimal solutions with a good spread is obtained. In addition to discussing some representative solutions, knowledge is extracted by applying sensitivity analysis to the solutions. The results provide some insight into the underlying features and trends of the design problem of TSTO space planes with RBCC engines.

Application of Wavelet Transform to System Identification of Small UAVs Flight Characteristic

In this paper, a new system identification technique of flight characteristic of small unmanned aerial vehicles (UAVs) is proposed. The proposed method is characterized by the use of time-frequency information provided by wavelet transform. The use of wavelet transform enhances robustness against undesirable condition on small UAVs flight, such as wind gust. The effectiveness of the proposed method is validated using flight log obtained by special avionics in real flight of a small UAV. The target small UAV used for the validation and avionics are also introduced for completeness.

Systems Analysis on Hypersonic Airplanes using Pre- Cooled Turbojet Engine

Systems analysis and evaluation of Mach 5 class hypersonic airplanes is performed. The airplane can fly across the Pacific Ocean in 2 hours. A multi-disciplinary optimization program with aerodynamic, thermal structure, propulsion and trajectory is used to define baseline shape. Pre-cooled turbojet engine is assumed as the propulsion system for the hypersonic airplane. The engine can be operated from takeoff to Mach 5, continuously. This engine has adopted pre-cooling cycle using cryogenic liquid hydrogen. The high temperature inlet air at the hypersonic flight will be cooled by liquid hydrogen for fuel. Surface flow of the airplane at hypersonic speed and low speed are evaluated using results of CFD analyses. The control characteristics with control wings and variation of aerodynamic characteristics by adding strakes are obtained by a low speed wind tunnel experiment. The heat flux distribution on the surface of the airframe at hypersonic cruise condition is evaluated by using the results of CFD analyses. The characteristics of heat shield materials for the surface of the fuselage at downstream of the exhaust gas is evaluated by an elemental experiment.

Formation Control of Small Unmanned Air Vehicles Under Faulty Communications

This paper discusses controlling formation of small unmanned air vehicles under faulty communication between formation members. The control scheme proposed in this paper combines virtual leader approach with point-to-multipoint communication, in order to enhance its robustness to communication failures and vehicle losses. Numerical simulation results show that formations will properly converge for a great majority of possible communication networks between vehicles and for communication success rates as low as 10%. Preparations for ground tests and flight tests are currently under way.

Flight Testing of a Wing-in-Propeller-Slipstream Mini Unmanned Aerial Vehicle

A prototype tail-sitter mini unmanned aerial vehicle (SkyEyeV) was developed and tested in a wind tunnel and by remotely controlled flight. A tail-sitter is an aircraft that takes off and lands on its tail section with its fuselage pointing upward. The prototype is powered by twin electric motors, and has a 1.05 m wingspan and a takeoff weight of 2.4 kg. A key feature of the prototype is leading edge slats, which are designed to avoid stall during high angle of attack transitional flight. Through wind tunnel testing, the slats were confirmed to increase the stall angle of attack not only in a non-powered condition (without propeller) but also in a powered condition (wing in propeller slipstream). The remotely piloted flight tests verified the vehicles designed flight capability, transition and hovering, and several useful insights were obtained.

A Study on Online Flight Trajectory Search and its Flight Simulator Testing

[Abstract] Real -time flight trajectory optimization algorithms are developed and evaluated through numerical simulation and flight simulator testing. The purpose of this study is to guide and control an aircraft in emergency landing. Though our final goal is to develop an automatic control system for tracking flight trajectories generated with the online optimization, this study verifies the validity of the generated optimal trajectories with manual flight control. This paper considers the real-time direct trajectory optimization method that can deal with constraints more strictly.

Indoor Flight Navigation System of Micro Air Vehicle with Inertial Sensor Drift Correction

This paper describes an indoor flight control system capable of autonomously exploring indoor areas with microelectromechanical systems (MEMS). Whereas the significant drift of MEMS is generally mitigated using occasional GPS location estimates, GPS is unavailable indoors. In order to solve this problem, a Rao-Blackwellized Particle Filter SLAM algorithm was used to make MAVs localize themselves and the drift error was examined afterward. This paper develops the way to correct the sensor drift by the pose estimated by localization.

Research Activity on Unmanned Air Vehicles at the University of Tokyo

This paper will summarize recent research activities on small unmanned aerial vehicles at the University of Tokyo. The topics discussed are: fields of research, unmanned aerial vehicles currently used and under development, and avionics and ground control station software.

Flight Test Evaluation of Non-Linear Dynamic Inversion Controller

** †† A guidance and control system for emergency landings is developed and flight tests are carried out using an experimental aircraft. The system consists of an online optimal trajectory design method and a tracking control method. The online version of a direct collocation method is developed and a nonlinear dynamic inversion with a singular perturbation method is designed for tracking optimized 4D trajectories. Numerical simulations and hardware-in-the-loop simulations are carried out before real flight tests. The flight control system is successfully evaluated in real flight experiments using modified Dornier 228 with fly-by-wire control systems.