Sangjong Lee

Three-Dimensional Ascent Trajectory Optimization for Stratospheric Airship Platforms in the Jet Stream

The authors would like to thank the Korea Ministry of Commerce, Industry, and Energy for their support of this project and for the permission to publish this work.

Feedback linearization controller for semi station keeping of the unmanned airship

This paper presents the process and results of the nonlinear system analysis and controller design for the station keeping flight of the large-scaled unmanned airship. Based on the nonlinear control techniques, the feedback linearization controller of the Multi-InputMulti-Output (MIMO) system has been applied to the 50m unmanned airship’s model which has been developed by Korea Aerospace Research Institute (KARI). The station keeping flight is one of the airship’s peculiar characteristic flight regime compared to a fixed wing aircraft’s one. It seems to be the hovering flight of the helicopter or tilt-rotor wing aircraft. To succeed in this flight, the airship should control the velocity, pitch attitude and heading angle as much accurately as possible under the given control scheme. The nonlinear system modeling and brief configuration of the 50m unmanned airship is introduced and the implementation process of the MIMO input-output linearization method is summarized. Finally numerical simulations are carried out to assess the performance of the proposed controller and the analysis of the zero dynamics of the proposed controller is performed to prove the stability of the controller.

Lateral and Directional SCAS Controller Design Using Multidisciplinary Optimization Program

The flight controller should meet the flying qualities, stability margins, and time response requirement according to the class of a target aircraft or UAV. Classical design process of PID controller is a very time consuming process and needed trial and erros. The best way is to apply the multi-disciplinary optimization algorithm to meet the numerous constraints of controller requirements. This paper presents how multi-objective parameter optimization (CONDUIT) can be used to determine many design parameters of lateral stability and augmentation system for roll and heading controller of the small UAV. To verify the effectiveness of applying the optimization method, designed controller using optimization are compared with the baseline controller that is designed only considering the time responses.

Comparison Study on Take-Off and Landing Flight Test Using Ground Observation and DGPS Method

The flight test is last means of compliance to satisfy airworthiness standards and important to evaluate the performance and safety of the developed aircraft. The flight test technologies are obtained from great numbers of experiences and know-hows and protected. In addition, flight test should be conducted efficiently since its various test conditions and items. Therefore, it is requisite to secure efficient flight test methods. This paper discusses the flight test methods for take-off and landing performance and two kinds of techniques are proposed. By performing real flight tests, they are compared with each other and analyzed through the flight analysis.

Design of the Automatic Flight and Guidance Controller for 50m Unmanned Airship Platform

The Stratospheric Airship Platform (SAP) has a capability of performing the autonomous and guidance flight to satisfy given missions. To be used as the High Altitude Platforms (HAPs), the capabilities of controlling platforms accurate position and keeping the station point are the most important features. Under this circumstances Autonomous Flight Control System (AFCS) is a critical system and plays a key role in achieving the given requirements and succeeding in missions. In this paper, the design and analysis results of the AFCS algorithms and controller are presented. The brief summary of the AFCS hardware structure is also explained. The autopilot controller and guidance logics were designed based on the linear dynamics of the unmanned airship platform and the full nonlinear dynamics was considered to evaluate and verify their performances.

Trajectory Optimization for Nonlinear Tracking Control in Stratospheric Airship Platform

Contrast to the 6-DOF nonlinear dynamic modeling of nonlinear tracking problem, 3-DOF point-mass modeling of flight mechanics is efficient and adequate for applying the trajectory optimization problem. There exist limitations to apply an optimal trajectory from point-mass modeling as a reference trajectory directly to conduct the nonlinear tracking control, In this paper, new matching trajectory optimization scheme is proposed to compensate those differences of mismatching. To verify performance of proposed method, full ascent three-dimensional flight trajectories are obtained by reflecting the real constraints of flight conditions and airship performance with and without jet stream condition. Then, they are compared with the optimal trajectories obtained from conventional method.

Nonlinear trajectory tracking using vectorial backstepping approach

This paper discussed a nonlinear trajectory tracking problem for stratospheric airship platform and a novel approach of the nonlinear control scheme is applied. Target airship model is the 200 m stratospheric airship platform capable of flying upto 20 km altitude. Full 6-DOF nonlinear dynamics of unmanned airship are defined according to the target airshippsilas configuration including the moving wind field. Based on this airship model, a backstepping design formulation for the trajectory tracking control is described. The tracking control strategy of vectorial backstepping is applied to derive the tracking control law and global asymptotically stability is proved by Lyapunov stability analysis. Finally, numerical simulations have been carried out to assess the performance of the proposed tracking controller.

ADAPTIVE BACKSTEPPING CONTROL FOR SATELLITE FORMATION FLYING WITH MASS UNCERTAINTY

Satellite formation flying has become a critical issue in the aerospace engineering because it is considered as an enabling technology for many space missions. Thus, many nonlinear control theories have been developed for the tracking problem of satellite formation flying, which include full-nonlinear dynamics, external disturbances and parameter uncertainty. In this study, nonlinear adaptive control law is developed using an adaptive backstepping technique to solve the relative position tracking problem of the satellite formation flying in the presence of mass uncertainty and the bounded external disturbance. Simulation studies are included to demonstrate the proposed controller performance. The proposed controller is shown to guarantee the system stability against the external bounded disturbances in the presence of mass uncertainty.