Autonomous Control Modes and Optimized Path Guidance for Shipboard Landing in High Sea States

Restricted (Penn State Only)
Author:
Yang, Junfeng
Graduate Program:
Aerospace Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 06, 2018
Committee Members:
  • Joseph F. Horn, Dissertation Advisor
  • Joseph F. Horn, Committee Chair
  • Edward C. Smith, Committee Member
  • Jack W. Langelaan, Committee Member
  • Christopher D. Rahn, Outside Member
Keywords:
  • Rotorcraft
  • Flight Simulation
  • Flight Control
  • Guidance and navigation
  • Autonomous System
  • Shipboard Landing
Abstract:
Rotorcraft, due to their unique vertical take-off and landing capability, are well-suited for maritime applications. The capability of shipboard launch and recovery of a rotorcraft allows extension of the operational envelope of a single ship as well as the whole fleet. However, due to the cross-axes coupling, inherent instability and sluggish response, accurate and soft landing of rotorcraft is a challenging task, especially when the flight deck is moving in high sea states and in the presence of adverse factors such as the gusty airwake and limited space. In low to medium sea state, an experienced pilot can designate a window of quiescent ship motion to perform the landing while also using an intuitive predictive strategy. In very high sea states, the workload and control precision become unacceptable, and therefore motivate the development of an automated landing system. This thesis contributes both theoretical investigations and technical solutions to the guidance, navigation and control for an autonomous shipboard recovery mode in high states. Using the high-fidelity modeling software FLIGHTLAB together with ship airwake and motion models, the specific aspects of rotorcraft flight dynamics and the characteristics of the shipboard landing environment were studied and provided guidelines for the formulation of design requirements. The Dynamic Inversion method was applied to design an inner-loop attitude control system and then an outer-loop trajectory following system, and the associated design problems such as control parameter optimization, robustness testing are discussed. In order to provide a fully autonomous capability, a parameterization and optimization algorithm was developed for approach path generation. The resulting path geometry and velocity profile can ensure fundamental flight safety but also provide enough flexibility for console operators to specify approach azimuth and steepness. A landing path generator incorporating predictive deck state has been developed to complete the last stage of shipboard recovery, both forecasting and instantaneous measurement of deck state are used to construct the commanded descent trajectory through a hybrid implementation. The technical adequacy of high-grade vehicle location and motion detection has been proven by an integrated navigation system incorporating information from GPS, inertial measurement unit and shipboard tracking system. Stand-alone testing of system components, as well as comprehensive testing of the entire system from approach entry to touchdown have been carried out using FLIGHTLAB simulations. As justified by the simulation results: the scientific concept and engineering approach developed in this thesis show great potential to an overall solution to the challenging problems of shipboard recovery of rotorcraft in high sea states in a fully autonomous mode.