Vision-Based Autonomous Landing of a Quadrotor on the Perturbed Deck of an Unmanned Surface Vehicle

Autonomous landing on the deck of an unmanned surface vehicle (USV) is still a major challenge for unmanned aerial vehicles (UAVs). In this paper, a fiducial marker is located on the platform so as to facilitate the task since it is possible to retrieve its six-degrees of freedom relative-pose in an easy way. To compensate interruption in the marker’s observations, an extended Kalman filter (EKF) estimates the current USV’s position with reference to the last known position. Validation experiments have been performed in a simulated environment under various marine conditions. The results confirmed that the EKF provides estimates accurate enough to direct the UAV in proximity of the autonomous vessel such that the marker becomes visible again. Using only the odometry and the inertial measurements for the estimation, this method is found to be applicable even under adverse weather conditions in the absence of the global positioning system

Helicopter Autonomous Ship Landing System

This research focuses on developing a helicopter autonomous ship landing algorithm based on the real helicopter ship landing procedure which is already proven and currently used by Navy pilots. It encompasses the entire ship landing procedure from approach to landing using a pilot-inspired vision-based navigation system. The present thesis focuses on the first step towards achieving this overarching objective, which involves modeling the flight dynamics and control of a helicopter and some preliminary simulations of a UH-60 (Blackhawk) helicopter landing on a ship. The airframe of the helicopter is modeled as a rigid body along with rotating articulated blades that can undergo flap, lag and pitch motions about the root. A UH-60 helicopter is used for a representative model due to its ample simulation and flight test data. Modeling a UH-60 helicopter is based on Blade Element Momentum Theory (BEMT), rotor aerodynamics with the Pitt-Peters linear inflow model, empennage aerodynamics and rigid body dynamics for fuselage. For the blade dynamics, the cyclic (1/rev) and collective pitch motions are prescribed and the blade (1/rev) flap and lag motions are obtained as a response to the aerodynamic and inertial forces. The helicopter control inputs and translational and attitude dynamics obtained from the model are validated with flight test data at various speeds and attitude. A linearized model is extracted based on a first-order Taylor series expansion of the nonlinear system about an equilibrium point for the purpose of determining the stability of the dynamic system, investigating sensitivity to gusts, and designing a model-based flight control system. Combined vision-based navigation and Linear Quadratic Regulator (LQR) for set-point tracking is used for disturbance rejection and tracking states. A rotatable camera is used for identifying the relative position of the helicopter with respect to the ship. Based on the position, a corresponding trajectory is computed. Considering the trade-off between transient responses and control efforts, gains for the LQR controller are chosen carefully and realistically. A fully autonomous flight is simulated from approach to landing on a ship. It consists of initial descent, steady forward flight, steady coordinated turn, deceleration, and final landing. Corresponding to each maneuver, relevant linearized model is used and gains are tuned. By using X-plane flight simulator program, the simulation data which include fuselage attitude and position at each time step are visualized with a single flight deck ship. This method allows an aircraft to land on a ship autonomously while maintaining high level of safety and accuracy without the need to capture the ship deck motions, however, by using a camera, and any other additional sensors, which will provide the accurate location of the ship relative to the helicopter. This method is not only relevant for a particular helicopter, but for any types of VTOL aircraft, manned or unmanned. Hence, it can improve the level of safety by preventing human errors that may occur during landing on a ship

Helicopter Autonomous Ship Landing System

This research focuses on developing a helicopter autonomous ship landing algorithm based on the real helicopter ship landing procedure which is already proven and currently used by Navy pilots. It encompasses the entire ship landing procedure from approach to landing using a pilot-inspired vision-based navigation system. The present thesis focuses on the first step towards achieving this overarching objective, which involves modeling the flight dynamics and control of a helicopter and some preliminary simulations of a UH-60 (Blackhawk) helicopter landing on a ship. The airframe of the helicopter is modeled as a rigid body along with rotating articulated blades that can undergo flap, lag and pitch motions about the root. A UH-60 helicopter is used for a representative model due to its ample simulation and flight test data. Modeling a UH-60 helicopter is based on Blade Element Momentum Theory (BEMT), rotor aerodynamics with the Pitt-Peters linear inflow model, empennage aerodynamics and rigid body dynamics for fuselage. For the blade dynamics, the cyclic (1/rev) and collective pitch motions are prescribed and the blade (1/rev) flap and lag motions are obtained as a response to the aerodynamic and inertial forces. The helicopter control inputs and translational and attitude dynamics obtained from the model are validated with flight test data at various speeds and attitude. A linearized model is extracted based on a first-order Taylor series expansion of the nonlinear system about an equilibrium point for the purpose of determining the stability of the dynamic system, investigating sensitivity to gusts, and designing a model-based flight control system. Combined vision-based navigation and Linear Quadratic Regulator (LQR) for set-point tracking is used for disturbance rejection and tracking states. A rotatable camera is used for identifying the relative position of the helicopter with respect to the ship. Based on the position, a corresponding trajectory is computed. Considering the trade-off between transient responses and control efforts, gains for the LQR controller are chosen carefully and realistically. A fully autonomous flight is simulated from approach to landing on a ship. It consists of initial descent, steady forward flight, steady coordinated turn, deceleration, and final landing. Corresponding to each maneuver, relevant linearized model is used and gains are tuned. By using X-plane flight simulator program, the simulation data which include fuselage attitude and position at each time step are visualized with a single flight deck ship. This method allows an aircraft to land on a ship autonomously while maintaining high level of safety and accuracy without the need to capture the ship deck motions, however, by using a camera, and any other additional sensors, which will provide the accurate location of the ship relative to the helicopter. This method is not only relevant for a particular helicopter, but for any types of VTOL aircraft, manned or unmanned. Hence, it can improve the level of safety by preventing human errors that may occur during landing on a ship

Helicopter Autonomous Ship Landing System

This research focuses on developing a helicopter autonomous ship landing algorithm based on the real helicopter ship landing procedure which is already proven and currently used by Navy pilots. It encompasses the entire ship landing procedure from approach to landing using a pilot-inspired vision-based navigation system. The present thesis focuses on the first step towards achieving this overarching objective, which involves modeling the flight dynamics and control of a helicopter and some preliminary simulations of a UH-60 (Blackhawk) helicopter landing on a ship. The airframe of the helicopter is modeled as a rigid body along with rotating articulated blades that can undergo flap, lag and pitch motions about the root. A UH-60 helicopter is used for a representative model due to its ample simulation and flight test data. Modeling a UH-60 helicopter is based on Blade Element Momentum Theory (BEMT), rotor aerodynamics with the Pitt-Peters linear inflow model, empennage aerodynamics and rigid body dynamics for fuselage. For the blade dynamics, the cyclic (1/rev) and collective pitch motions are prescribed and the blade (1/rev) flap and lag motions are obtained as a response to the aerodynamic and inertial forces. The helicopter control inputs and translational and attitude dynamics obtained from the model are validated with flight test data at various speeds and attitude. A linearized model is extracted based on a first-order Taylor series expansion of the nonlinear system about an equilibrium point for the purpose of determining the stability of the dynamic system, investigating sensitivity to gusts, and designing a model-based flight control system. Combined vision-based navigation and Linear Quadratic Regulator (LQR) for set-point tracking is used for disturbance rejection and tracking states. A rotatable camera is used for identifying the relative position of the helicopter with respect to the ship. Based on the position, a corresponding trajectory is computed. Considering the trade-off between transient responses and control efforts, gains for the LQR controller are chosen carefully and realistically. A fully autonomous flight is simulated from approach to landing on a ship. It consists of initial descent, steady forward flight, steady coordinated turn, deceleration, and final landing. Corresponding to each maneuver, relevant linearized model is used and gains are tuned. By using X-plane flight simulator program, the simulation data which include fuselage attitude and position at each time step are visualized with a single flight deck ship. This method allows an aircraft to land on a ship autonomously while maintaining high level of safety and accuracy without the need to capture the ship deck motions, however, by using a camera, and any other additional sensors, which will provide the accurate location of the ship relative to the helicopter. This method is not only relevant for a particular helicopter, but for any types of VTOL aircraft, manned or unmanned. Hence, it can improve the level of safety by preventing human errors that may occur during landing on a ship

Helicopter Autonomous Ship Landing System

This research focuses on developing a helicopter autonomous ship landing algorithm based on the real helicopter ship landing procedure which is already proven and currently used by Navy pilots. It encompasses the entire ship landing procedure from approach to landing using a pilot-inspired vision-based navigation system. The present thesis focuses on the first step towards achieving this overarching objective, which involves modeling the flight dynamics and control of a helicopter and some preliminary simulations of a UH-60 (Blackhawk) helicopter landing on a ship. The airframe of the helicopter is modeled as a rigid body along with rotating articulated blades that can undergo flap, lag and pitch motions about the root. A UH-60 helicopter is used for a representative model due to its ample simulation and flight test data. Modeling a UH-60 helicopter is based on Blade Element Momentum Theory (BEMT), rotor aerodynamics with the Pitt-Peters linear inflow model, empennage aerodynamics and rigid body dynamics for fuselage. For the blade dynamics, the cyclic (1/rev) and collective pitch motions are prescribed and the blade (1/rev) flap and lag motions are obtained as a response to the aerodynamic and inertial forces. The helicopter control inputs and translational and attitude dynamics obtained from the model are validated with flight test data at various speeds and attitude. A linearized model is extracted based on a first-order Taylor series expansion of the nonlinear system about an equilibrium point for the purpose of determining the stability of the dynamic system, investigating sensitivity to gusts, and designing a model-based flight control system. Combined vision-based navigation and Linear Quadratic Regulator (LQR) for set-point tracking is used for disturbance rejection and tracking states. A rotatable camera is used for identifying the relative position of the helicopter with respect to the ship. Based on the position, a corresponding trajectory is computed. Considering the trade-off between transient responses and control efforts, gains for the LQR controller are chosen carefully and realistically. A fully autonomous flight is simulated from approach to landing on a ship. It consists of initial descent, steady forward flight, steady coordinated turn, deceleration, and final landing. Corresponding to each maneuver, relevant linearized model is used and gains are tuned. By using X-plane flight simulator program, the simulation data which include fuselage attitude and position at each time step are visualized with a single flight deck ship. This method allows an aircraft to land on a ship autonomously while maintaining high level of safety and accuracy without the need to capture the ship deck motions, however, by using a camera, and any other additional sensors, which will provide the accurate location of the ship relative to the helicopter. This method is not only relevant for a particular helicopter, but for any types of VTOL aircraft, manned or unmanned. Hence, it can improve the level of safety by preventing human errors that may occur during landing on a ship

Technical Workshop: Advanced Helicopter Cockpit Design

Information processing demands on both civilian and military aircrews have increased enormously as rotorcraft have come to be used for adverse weather, day/night, and remote area missions. Applied psychology, engineering, or operational research for future helicopter cockpit design criteria were identified. Three areas were addressed: (1) operational requirements, (2) advanced avionics, and (3) man-system integration

Aeronautical Engineering: A Continuing Bibliography with Indexes (supplement 194)

This bibliography lists 369 reports, articles and other documents introduced into the NASA scientific and technical information system in November 1985

Automatic Landing of a Rotary-Wing UAV in Rough Seas

Rotary-wing unmanned aerial vehicles (RUAVs) have created extensive interest in the past few decades due to their unique manoeuverability and because of their suitability in a variety of flight missions ranging from traffic inspection to surveillance and reconnaissance. The ability of a RUAV to operate from a ship in the presence of adverse winds and deck motion could greatly extend its applications in both military and civilian roles. This requires the design of a flight control system to achieve safe and reliable automatic landings. Although ground-based landings in various scenarios have been investigated and some satisfactory flight test results are obtained, automatic shipboard recovery is still a dangerous and challenging task. Also, the highly coupled and inherently unstable flight dynamics of the helicopter exacerbate the difficulty in designing a flight control system which would enable the RUAV to attenuate the gust effect. This thesis makes both theoretical and technical contributions to the shipboard recovery problem of the RUAV operating in rough seas. The first main contribution involves a novel automatic landing scheme which reduces time, cost and experimental resources in the design and testing of the RUAV/ship landing system. The novelty of the proposed landing system enables the RUAV to track slow-varying mean deck height instead of instantaneous deck motion to reduce vertical oscillations. This is achieved by estimating the mean deck height through extracting dominant modes from the estimated deck displacement using the recursive Prony Analysis procedure. The second main contribution is the design of a flight control system with gust-attenuation and rapid position tracking capabilities. A feedback-feedforward controller has been devised for height stabilization in a windy environment based on the construction of an effective gust estimator. Flight tests have been conducted to verify its performance, and they demonstrate improved gust-attenuation capability in the RUAV. The proposed feedback-feedforward controller can dynamically and synchronously compensate for the gust effect. In addition, a nonlinear H1 controller has been designed for horizontal position tracking which shows rapid position tracking performance and gust-attenuation capability when gusts occur. This thesis also contains a description of technical contributions necessary for a real-time evaluation of the landing system. A high-infedlity simulation framework has been developed with the goal of minimizing the number of iterations required for theoretical analysis, simulation verification and flight validation. The real-time performance of the landing system is assessed in simulations using the C-code, which can be easily transferred to the autopilot for flight tests. All the subsystems are parameterized and can be extended to different RUAV platforms. The integration of helicopter flight dynamics, flapping dynamics, ship motion, gust effect, the flight control system and servo dynamics justifies the reliability of the simulation results. Also, practical constraints are imposed on the simulation to check the robustness of the flight control system. The feasibility of the landing procedure is confimed for the Vario helicopter using real-time ship motion data

Employ sensor fusion techniques for determining aircraft attitude and position information

Inertial Navigation Systems (INS) with the level of precision needed for Unmanned Aerial Vehicles (UAV) can easily cost more than the vehicle itself. This drastically increases the amount of aircraft power consumption and payload weight that drives the need for a low cost solution. This can be achieved through the use of sensor fusion techniques on low cost accelerometers and gyroscopes fused with Global Positioning System (GPS) data. In this paper, existing GPS and Inertial Measurement Unit (IMU) flight data is fused with the use of both an Kalman filter (KF) and Extended Kalman filter (EKF) methods for a more accurate estimate of the aircraft attitude, velocity, and position eliminating the need for the high cost attitude sensors. A simulation study shows that four sensor fusion methods verifying that an improvement of position, velocity, and attitude can be achieved using low-cost sensors. The first method incorporates a six state KF that corrects INS/GPS position and velocity errors. The second method features the GPS to estimate attitude parameters, which in turn uses in an EKF to correct INS attitude values. With this method, improved attitude values are obtained without the calculation of the full INS state; such that the INS position and velocity are not required, reducing the computational load. The third method uses only the GPS and INS position and velocity to correct for the errors in the full state of the INS also using an EKF. Finally, the last method combines the GPS attitude of the second method and the error reduction of the third method to further decrease the error in the velocity, position, and attitude of the system. The simulation results illustrate that all of the methods tested provide performance improvement to the system, and could be implemented in real-time on a UAV for accurate navigation parameters

Aeronautical engineering, a continuing bibliography with indexes

This bibliography lists 419 reports, articles and other documents introduced into the NASA scientific and technical information system in March 1985