Landing Of Unmanned Helicopter Research Articles

Whole-Body Control for Autonomous Landing of Unmanned Helicopter Equipped With Antagonistic Cable-Driven Legged Landing Gear

Whole-Body Control for Autonomous Landing of Unmanned Helicopter Equipped With Antagonistic Cable-Driven Legged Landing Gear

Guidance Law for Autonomous Takeoff and Landing of Unmanned Helicopter on Mobile Platform Based on Asymmetric Tracking Differentiator

For some flight missions, such as autonomous landing on mobile platforms, the demands on indicators such as target-tracking accuracy and so on are relatively high. To achieve this, a guidance system with excellent precision is necessary. An asymmetric tracking differentiator based on a tracking differentiator is proposed to establish the guidance system. On the basis of the proposed asymmetric tracking differentiator, an altitudinal and horizontal helicopter guidance system structure is designed. In this paper, a guidance law is designed in order to meet the accuracy and precision requirements in the autonomous landing and transition process. Apart from that, a plane-motion-guidance law is also designed to realize static and dynamic point tracking, linear route tracking and circular route tracking to improve the trajectory smoothness and accuracy. Finally, simulations of the autonomous landing process on moving platforms, including three stages, namely approaching, tracking and landing, are completed. The application effects and precision of the autonomous landing guidance algorithm under different wave heights and period conditions are analyzed through the obtained simulation curves.

Linear Velocity-Free Visual Servoing Control for Unmanned Helicopter Landing on a Ship With Visibility Constraint

In this article, a constrained image-based visual servoing control method for the shipboard landing problem of unmanned helicopters is proposed. First, the pitch and roll motion of ship are predicted by an autoregressive (AR) model to determine an appropriate period for landing. Subsequently, a novel robust sliding mode controller without linear velocity measurements is developed on the basis of the perspective image feature in a virtual image plane. Meanwhile, a modified Chebyshev neural network (CNN) is proposed to estimate the uncertainties, including the linear acceleration of ship and translational perturbation, while an adaptive law is employed to compensate the influence of rotational disturbances. The whole controller only requires the measurements feedback of a vision sensor and an inertial measurement unit (IMU). Ulteriorly, to prevent the visual target on the ship from going beyond the field of view of camera, the constrained controller is developed by a control barrier function and a quadratic programming, where the unknown relative velocity is estimated by a velocity observer. Finally, simulations are implemented to substantiate the capability of the presented shipboard landing control method.

Design and analysis of retractable structure of new quadrotor landing gear

With the development of equipment level, the requirements for the compact-ness and light-weight of UAV become more and more stringent. In order to solve the problems such as the weight and large volume of the landing gear of the existing four-rotor aircraft, this paper developed a new four-rotor unmanned helicopter landing gear retractable structure based on the existing landing gear. The release process and retractation of retractable structure of the new landing gear are described, and its motion form and attitude are introduced in detail. In this paper, the stress of high strength flexible rope during landing gear releasing and re-tracting is analyzed, and the mathematical model is established. Adams software is used to simulate and analyze the force state of the landing gear leg when the rope is pulling at a constant speed. The results of the dynamic simulation and mathematical model are consistent, that is, the maximum force when retracted to 90° is about 30N (for a single wing). Finally, the finite element simulation software Ansys Workbench was used to carry out strength checking and deformation analysis of the wing, and the rationality of the designed me-chanical structure was verified. The research results of this paper provide a certain basis for the development of landing gear of four-rotor unmanned helicopter.

Feature article: Overview of landmarks for autonomous, vision-based landing of unmanned helicopters

The characteristics of a landing landmark are a key concern when an autonomous, vision-based unmanned helicopter is landing. The shape and recognition of the landmark determines the posture parameters of the unmanned helicopter and the accuracy of its autonomous landing. This article analyzes and summarizes the shapes and the detection methods of various landmarks used for autonomous landing of helicopters, as well as their relationship to the posture parameters. The characteristics of different landing landmarks are obtained, and then the development of autonomous landing landmarks is analyzed. Finally, this article offers some directions for the future research of autonomous, vision-based landing of unmanned helicopters.

Autonomous Shipboard Landing Algorithm for Unmanned Helicopters in Crosswind

This paper introduces an algorithm for the autonomous shipboard landing of unmanned helicopters in crosswind, using time-delay control. The proposed algorithm is composed of two parts: the controll...

Research on Unmanned Aerial Vehicles Autonomous Soft Landing Based on Optimal Control

This paper deals with the autonomous soft landing of unmanned helicopter aiming to enhance its application. Soft landing means to reduce the shock force upon ground during the helicopters land. Helicopter is a multi-input multi-output system and for which optimal control provides graceful and coordinated controls. Firstly, the experimental platform configuration for autonomous soft-landing system is introduced, which is based on the model helicopter. The time-varying gains and time-varying quadratic performance index Linear Quadratic control for autonomous soft landing of miniature helicopter is applied to unmanned helicopter. Simulation shows that the outputs of the system can respond the input signals accurately.

Lyapunov Control Law for Automatic Approach for Unmanned Helicopter Landing

Describing the flight behavior of a helicopter is a difficult challenge in mathematical modeling. A rotorcraft can be considered as a complex arrangement of interacting subsystems, and the problem is dominated by rotor. The rotor blades bend and twist under the influence of unsteady and nonlinear aerodynamic loads, which are themselves a function of blade motion. This problem makes it more difficult to estimate the behavior of a helicopter. Furthermore, it is difficult to design a flight controller for unmanned helicopter systems. In this paper, to obtain a nonlinear dynamic model of a helicopter, parameter identification is performed using flight test data. A globally stable tracking control law for agile and precise landing of an unmanned helicopter is proposed. A near-minimum time control scheme is adopted to design the reference trajectory, and it is shown that the control law is guaranteed to be stable globally in the sense of Lyapunov. A flight test verified the performance of the proposed method. Performance can be improved by choosing the control parameters via optimization. The proposed method can be extended to a multiple output trajectory tracking problem for a precise fixed-wing UAV landing.