Autonomous landing control of highly flexible aircraft based on Lidar preview in the presence of wind turbulence

This paper investigates preview-based autonomous landing control of a highly flexible flying wing model using short range Lidar wind measurements in the presence of wind turbulence. The preview control system is developed based on a reduced-order linear aeroelastic model and employs a two-loop control scheme. The outer loop employs the LADRC (linear active disturbance rejection control) and PI algorithms to track the reference landing trajectory and vertical speed, respectively, and to generate the attitude angle command. This is then used by the inner-loop using H∞ preview control to compute the control inputs to the actuators (control flaps and thrust). A landing trajectory navigation system is designed to generate real-time reference commands for the landing control system. A Lidar (light detection and ranging) simulator is developed to measure the wind disturbances at a distance in front of the aircraft, which are provided to the inner-loop H∞ preview controller as prior knowledge to improve control performance. Simulation results based on the full-order nonlinear flexible aircraft dynamic model show that the preview-based landing control system is able to land the flying wing effectively and safely, showing better control performance than the baseline landing control system (without preview) with respect to landing effectiveness and disturbance rejection. The control system’s robustness to measurement error in the Lidar system is also demonstrated

Wind Preview-Based Model Predictive Control of Multi-Rotor UAVs Using LiDAR

Autonomous outdoor operations of Unmanned Aerial Vehicles (UAVs), such as quadrotors, expose the aircraft to wind gusts causing a significant reduction in their position-holding performance. This vulnerability becomes more critical during the automated docking of these vehicles to outdoor charging stations. Utilising real-time wind preview information for the gust rejection control of UAVs has become more feasible due to the advancement of remote wind sensing technology such as LiDAR. This work proposes the use of a wind-preview-based Model Predictive Controller (MPC) to utilise remote wind measurements from a LiDAR for disturbance rejection. Here a ground-based LiDAR unit is used to predict the incoming wind disturbance at the takeoff and landing site of an autonomous quadrotor UAV. This preview information is then utilised by an MPC to provide the optimal compensation over the defined horizon. Simulations were conducted with LiDAR data gathered from field tests to verify the efficacy of the proposed system and to test the robustness of the wind-preview-based control. The results show a favourable improvement in the aircraft response to wind gusts with the addition of wind preview to the MPC; An 80% improvement in its position-holding performance combined with reduced rotational rates and peak rotational angles signifying a less aggressive approach to increased performance when compared with only feedback based MPC disturbance rejection. System robustness tests demonstrated a 1.75 s or 120% margin in the gust preview’s timing or strength respectively before adverse performance impact. The addition of wind-preview to an MPC has been shown to increase the gust rejection of UAVs over standard feedback-based MPC thus enabling their precision landing onto docking stations in the presence of wind gusts

Flight control of very flexible unmanned aerial vehicles

This thesis aims to investigate the flight control of a very flexible ying wing model already developed in the literature. The model was derived from geometrically nonlinear beam theory using intrinsic degrees of freedom and linear unsteady aerodynamics, which resulted in a coupled structural dynamics, aerodynamics, and flight dynamics description. The scenarios of trajectory tracking and autonomous landing in the presence of wind disturbance are considered in control designs. Firstly, the aeroelastic and trajectory control of this very flexible ying wing model is studied. The control design employs a two-loop PI/LADRC (proportional integral/linear active disturbance rejection control) and H1 control scheme, based on a reduced-order linear model. The outer loop employs the PI/LADRC technique to track the desired flight paths and generate attitude commands to the inner loop, while the inner loop uses H1 control to track the attitude command and computes the corresponding control inputs. The particle swarm optimization algorithm is employed for parameter optimization in the H1 control design to enhance the control effectiveness and robustness. Simulation tests conducted on the full-order nonlinear model show that the designed aeroelastic and trajectory control system achieves good performance in aspects of tracking effectiveness and robustness against disturbance rejection. Secondly, the preview-based autonomous landing control of the very flexible ying wing model using light detection and ranging (Lidar) wind measurements is studied. The preview control system follows the above two-loop control structure and is also designed based on the reduced-order linear model. The outer loop emxv ploys the same LADRC and PI algorithms to track the reference landing trajectory and vertical speed, respectively. But the inner loop is extended to introduce Lidar wind measurements at a distance in front of the aircraft, employing H1 preview control to improve disturbance rejection performance during landing. Simulation results based on the full-order nonlinear model show that the preview-based landing control system is able to land the aircraft safely and effectively, which also achieves better control performance than a baseline landing control system (without preview) with respect to landing effectiveness and disturbance rejection. Finally, the data-driven flight control of the very flexible ying wing model using Model-Free Adaptive Control (MFAC) scheme to reduce the dependence of control design on system modeling is studied. A cascaded proportional-derivative MFAC (PD-MFAC) approach is proposed to accommodate the MFAC scheme in a flight control problem, which shows better control performance over the original MFAC algorithm. Based on the PD-MFAC approach, the data-driven flight control system is developed to achieve gust load alleviation and trajectory tracking. Simulation results based on the full-order nonlinear model show that the proposed data-driven flight control system is able to properly regulate all the rigid-body and flexible modes with better effectiveness and robustness (against disturbance rejection and modeling uncertainties), compared to a baseline H1 flight control system

2020 NASA Technology Taxonomy

This document is an update (new photos used) of the PDF version of the 2020 NASA Technology Taxonomy that will be available to download on the OCT Public Website. The updated 2020 NASA Technology Taxonomy, or "technology dictionary", uses a technology discipline based approach that realigns like-technologies independent of their application within the NASA mission portfolio. This tool is meant to serve as a common technology discipline-based communication tool across the agency and with its partners in other government agencies, academia, industry, and across the world

Aeronautical engineering: A continuing bibliography with indexes (supplement 233)

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1988. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 201)

This bibliography lists 438 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1986

Fourth Airborne Geoscience Workshop

The focus of the workshop was on how the airborne community can assist in achieving the goals of the Global Change Research Program. The many activities that employ airborne platforms and sensors were discussed: platforms and instrument development; airborne oceanography; lidar research; SAR measurements; Doppler radar; laser measurements; cloud physics; airborne experiments; airborne microwave measurements; and airborne data collection

Research and technology highlights, 1993

This report contains highlights of the major accomplishments and applications that have been made by Langley researchers and by our university and industry colleagues during the past year. The highlights illustrate both the broad range of the research and technology activities supported by NASA Langley Research Center and the contributions of this work toward maintaining United States leadership in aeronautics and space research. This report also describes some of the Center's most important research and testing facilities

Aeronautical engineering: A continuing bibliography with indexes (supplement 268)

This bibliography lists 406 reports, articles, and other documents introduced into the NASA scientific and technical information system in July, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics