Quadrotor Aircraft Research Articles

Research on Flight Control of Quad-rotor Based on Backstepping and Adaptive Control Technology

According to the uncertainty problem in the process of quad-rotor aircraft flight, As close to the actual flight environment, The nonlinear dynamic model of quad-rotor aircraft is established,On the basis of the backstepping, Analyzed the presence of interference control quantity expression and adaptive law.This paper puts forward a technique of backstepping and adaptive control technology,Through Matlab simulation and flight test of the designed adaptive inverse footwork the effectiveness of the proposed controller is verified, The simulation results show that the system has good robustness.

Attitude Optimal Backstepping Controller Based Quaternion for a UAV

A hierarchical controller design based on nonlinearH∞theory and backstepping technique is developed for a nonlinear and coupled dynamic attitude system using conventional quaternion based method. The derived controller combines the attractive features ofH∞optimal controller and the advantages of the backstepping technique leading to a control law which avoids winding phenomena. Performance issues of the controller are illustrated in a simulation study made for a four-rotor vertical take-off and landing (VTOL) aerial robot prototype known as the quadrotor aircraft.

Backstepping based Trajectory Tracking Control for a Quadrotor Aircraft with Nonlinear Disturbance Observer

In this paper, we investigate the trajectory tracking problem for the 6-DOF quadrotor aircraft with both internal uncertainties and external disturbances. The nonlinear system model is established based on Modified Rodrigues Parameters and the error model is then obtained based on the trajectory tracking task. To deal with the cascade property of the controlled objective, the system is divided into the translational and rotational subsystem, respectively. Hence, a hierarchical technique is introduced to implement the control system. Then, nonlinear disturbance observer based backstepping control strategy is proposed based on each subsystem. Global stability of the closed-loop system is analyzed based on Lyapunov theorem. Simulation results verify the effectiveness of the proposed control scheme.

An interactive tool for designing quadrotor camera shots

Cameras attached to small quadrotor aircraft are rapidly becoming a ubiquitous tool for cinematographers, enabling dynamic camera movements through 3D environments. Currently, professionals use these cameras by flying quadrotors manually, a process which requires much skill and dexterity. In this paper, we investigate the needs of quadrotor cinematographers, and build a tool to support video capture using quadrotor-based camera systems. We begin by conducting semi-structured interviews with professional photographers and videographers, from which we extract a set of design principles. We present a tool based on these principles for designing and autonomously executing quadrotor-based camera shots. Our tool enables users to: (1) specify shots visually using keyframes; (2) preview the resulting shots in a virtual environment; (3) precisely control the timing of shots using easing curves; and (4) capture the resulting shots in the real world with a single button click using commercially available quadrotors. We evaluate our tool in a user study with novice and expert cinematographers. We show that our tool makes it possible for novices and experts to design compelling and challenging shots, and capture them fully autonomously.

Path-Tracking Control of Stochastic Quadrotor Aircraft in Three-Dimensional Space

Despite the fact that environmental loads (forces and moments) induced by wind on quadrotor vertical take-off and landing (VTOL) aircraft consist of both deterministic and stochastic components, all existing works on controlling the aircraft either ignore these loads or treat them as deterministic. This ignorance or treatment deteriorates the control performance in a practical implementation. This paper presents a constructive design of controllers for a quadrotor aircraft to track a reference path in three-dimensional (3D) space under both deterministic and stochastic disturbances. A combination of Euler angles and unit-quaternion for the attitude representation of the aircraft is used to result in an effective control design, and to achieve path-tracking control results. Weak and strong nonlinear Lyapunov functions are introduced to overcome difficulties caused by underactuation and Hessian terms induced by stochastic differentiation rule. To overcome the inherent underactuation of the aircraft, the roll and pitch angles of the aircraft are considered as immediate controls. Potential projection functions are introduced to design estimates of the deterministic components and covariances of the stochastic components. Simulations illustrate the results.

Almost global trajectory tracking control of quadrotors with constrained control inputs

Control system design of small unmanned aerial vehicles with constrained inputs is an important design problem in practice which is usually not taken into account in many autopilot systems. This paper addresses a new control algorithm for trajectory tracking control of quadrotor aircrafts in the presence of control input constraint. To convert tracking-control problem to regulator one, the modified Rodrigues parameters (MRPs) based relative position and attitude kinematic and dynamic equations of a quadrotor are developed. The proposed algorithm employs the cascaded control scheme that is connected by a MRPs attitude extraction algorithm. The almost global closed-loop stability is guaranteed via the use of Lyapunov analysis tools, and an implicit manipulation for input constraint is obtained by employing the properties of the MRPs representation and hyperbolic tangent function. Finally, simulations are performed to demonstrate the validity and effectiveness of the proposed algorithm.

Robust trajectory tracking for quadrotor aircraft based on ADRC attitude decoupling control

An attitude decoupling algorithm based on active disturbance rejection control( ADRC) was designed for underactuated quadrotor aircraft. The algorithm can overcome some shortcomings of traditional control method for underactuated quadrotor,such as strong coupling between system states,weak anti-interference ability and high sensitivity of tracking performance to modeling errors,etc. The state coupling was tracked and estimated by extended state observer( ESO),system interference can be estimated by ESO at the same time. The interference of the system includes internal and external disturbances. The nonlinear multipleinput multiple-output( MIMO) system was transformed into linear single-input single-output( SISO) system by dynamic feedback linearization. Then using the nonlinear feedback control law to achieve high quality control of the attitude system,and study the robust trajectory tracking problem of the aircraft based on the attitude decoupling control algorithm. The simulation results show that the above attitude control algorithm can improve the robustness of the trajectory tracking system. The algorithm does not rely on the accurate system model,reduces the difficulty of practical application,and has strong anti-interference capability and practical application value as well.

Optimal Kalman Filter for state estimation of a quadrotor UAV

In this work, the main objective is to study the Optimal Kalman Filtering (OKF) method for estimating the state vector of a small quadrotor UAV through incorporating the internal disturbances including the white Gaussian process and measurement noises. Firstly, the kinematic and dynamic model of the quadrotor is transformed into a discrete-time system via the linear extrapolation method. Secondly, for the sake of performing the high accuracy position and attitude tracking control of the quadrotor, the discrete-time flight controller is designed using second order discrete-time sliding mode technique. In addition, the estimation of the quadrotor aircraft's state vector is carried out with the use of OKF. The performance of the combination between the flight controller and the OKF is evaluated through simulation tests. Extensive simulation results show that the combined strategy has a good performance in terms of variance and state estimation.

Aggressive flight of fixed-wing and quadrotor aircraft in dense indoor environments

In this paper, we describe trajectory planning and state estimation algorithms for aggressive flight of micro aerial vehicles in known, obstacle-dense environments. Finding aggressive but dynamically feasible and collision-free trajectories in cluttered environments requires trajectory optimization and state estimation in the full state space of the vehicle, which is usually computationally infeasible on realistic timescales for real vehicles and sensors. We first build on previous work of van Nieuwstadt and Murray and Mellinger and Kumar, to show how a search process can be coupled with optimization in the output space of a differentially flat vehicle model to find aggressive trajectories that utilize the full maneuvering capabilities of a quadrotor. We further extend this work to vehicles with complex, Dubins-type dynamics and present a novel trajectory representation called a “Dubins–Polynomial trajectory”, which allows us to optimize trajectories for fixed-wing vehicles. To provide accurate state estimation for aggressive flight, we show how the Gaussian particle filter can be extended to allow laser rangefinder localization to be combined with a Kalman filter. This formulation allows similar estimation accuracy to particle filtering in the full vehicle state but with an order of magnitude more efficiency. We conclude with experiments demonstrating the execution of quadrotor and fixed-wing trajectories in cluttered environments. We show results of aggressive flight at speeds of up to 8 m/s for the quadrotor and 11 m/s for the fixed-wing aircraft.

Nonlinear augmented observer design and application to quadrotor aircraft

This paper presents a nonlinear augmented observer, and it is applied to an underactuated quadrotor aircraft. Not only the proposed augmented observer can estimate the velocity from the position measurement, but also the uncertainties can be obtained. The robustness in time domain and in frequency domain is analyzed, respectively. The merits of the presented augmented observer include its synchronous estimation of velocity and uncertainties, finite-time stability, ease of parameters selection, and sufficient stochastic noise rejection. Moreover, a simple control law based on the augmented observer is designed to stabilize the flight dynamics. Simulation results illustrate the effectiveness of the proposed method.

Nonlinear Double-Integral Observer and Application to Quadrotor Aircraft

This paper presents a nonlinear double-integral observer based on finite-time stability. The proposed double-integral observer can estimate the onefold and double integrals of a signal synchronously, and the stability in time domain is analyzed. The merits of the presented double-integral observer include its finite-time stability, ease of parameter selection, sufficient stochastic noise rejection, and almost no drift phenomenon. The theoretical results are confirmed by the simulations and an experiment on a quadrotor aircraft: 1) the estimation of position and velocity from the acceleration measurement and 2) a control law is designed based on the double-integral observer to track a reference trajectory.

Augmented L<sub>1</sub> adaptive tracking control of quad-rotor unmanned aircrafts

This paper addresses a new trajectory tracking controller for quad-rotor aircrafts in the presence of time-varying aerodynamic effect and bounded external disturbance using the novel L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> adaptive control methodology augmented with nonlinear feed-forward compensations. The proposed augmented L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> adaptive controller achieves uniformly bounded transient and asymptotic tracking of the output signal for any designated bounded reference trajectory. Finally, simulations of tracking a circular reference trajectory are performed to illustrate the validity of the proposed controller.

Safe Landing Analysis of a Quadrotor Aircraft With Two Legs

We proposed a multi-propeller multifunction aerial robot (MMAR) that is composed of a quadrotor with two legs. The legs can increase the function of the robot. We found that the legs can increase the safety region of the robot during the landing. To study the safety problem, the dynamics of MMAR interacting with environment should be solved. On the basis of the interaction dynamics, this paper investigates the velocity constraint for safe landing of MMAR. The investigation begins from the kinematics and dynamics of MMAR in flight mode. Then the impact dynamics of MMAR during landing is developed. Furthermore, the landing safety problem is formulated by a series of constraint equations which can give a safety region of the velocity during landing. The safety region can give the safe velocity of the aerial robot before landing. Finally, simulation examples are presented using the proposed methodology. In the examples, a detailed safety region of a simulated MMAR is constructed and shown.

High-order nonlinear differentiator and application to aircraft control

In this paper, a high-order continuous nonlinear differentiator with lead compensation is presented based on finite-time stability. Not only the proposed high-order nonlinear differentiator can obtain the high-order derivatives of a signal, but also the chattering phenomenon can be reduced sufficiently. The parameters regulation is only required to be satisfied with Routh–Hurwitz Stability Criterion. The presented differentiator is a generalization of sliding mode differentiator and linear high-gain differentiator. The merits of the continuous differentiator include its simplicity, selecting parameters easily, restraining noises sufficiently, decreasing the phase shift and avoiding the chattering phenomenon. The theoretical results are confirmed by computer simulations and an experiment on a quadrotor aircraft: (i) the estimation of flying velocity and acceleration from the position measurement; (ii) a control law is designed based on the presented nonlinear differentiator to track a reference trajectory.

Verification of a special inertial measurement unit using a Quadrotor aircraft

Purpose – Calibration and 6-DOF test of a unique inertial measurement unit (IMU) using a Quadrotor aircraft. The purpose of this paper is to discuss the above issue. Design/methodology/approach – An IMU with the special capability of measuring the angular acceleration was developed and tested. A Quadrotor aircraft is used as 6-DOF test platform. Kinematics modeling of the Quadrotor was used in the determination of the Euler angles, while Dynamics modeling aided in the design the closed loop controller. For safety, the flight test was performed on a 6-DOF constrained reduced-gravity test stand. Findings – The developed IMU is suitable for measuring states and its time derivatives of mini UAVs. Not only that but also a simple control algorithm can be integrated in the same processing unit (a 32 microcontroller in this case). Originality/value – The tested IMU as well as the safety constrained test techniques are unique.

四旋翼飞行器中升力波动的干扰与抑制

The lift of a quad-rotor aircraft is composed of series frequencies related to the rotor speeds. As it will interferes the control of the aircraft, this paper analyzes the effect of high-frequency lift component on the aircraft and gives an inhibiting method for the lift fluctuation. Firstly, the dynamic model of quad rotor aircraft was established by Lagrangians method and the relational expression between the high-frequency lift component and the disturbance of aircraft angular velocity was obtained. According to the previous analysis, the angular velocity feedback loop was joined a Kalman filter for colored noise to restrain the disturbance of angular velocity acting on the controller. A prototype was designed. The testing results show when the proposed method is used in hovering control of the quad rotor aircraft, the control variable fluctuations decrease by 50% and the high frequency control volume attenuates to under -17 db as compared with that of traditional PID method, respectively. The method of this paper effectively solves the effect of lift fluctuation on the quad rotor aircraft and improves the efficiency of control.

Nonlinear Multiple Integrator and Application to Aircraft Navigation

In this paper, a nonlinear robust multiple integrator algorithm is presented based on finite-time stability. The nonlinear integrator can obtain the multiple integrals of signal. Conditions are given ensuring finite-time stability for the presented integrator. The stability and robustness are analysed. The merits of the presented integrator include its multiple-integral estimation, finite-time stability, selecting parameters easily, restraining stochastic noise sufficiently, and almost no drift phenomenon. The theoretical results are confirmed by computer simulations and two aircraft navigation experiments on a quadrotor aircraft: 1) the estimation of flying trajectory and velocity from the measurements of accelerations; 2) the estimation of attitude angle and angular rate from the measurements of angular accelerations.

Chattering-Free Sliding Mode Altitude Control for a Quad-Rotor Aircraft: Real-Time Application

Nowadays, the chattering problem in sliding mode control is one of the most important points to consider in real-time applications. To address this problem, a real-time robust altitude control scheme is proposed for the efficient performance of a Quad-rotor aircraft system using a continuous sliding mode control. The sensing of altitude measurement sensing is performed by a pressure sensor in order to obtain a robust altitude control of the vehicle in hovering mode both indoor and outdoor. The altitude measurement has the advantage of introducing this state information directly in the closed loop control which should be very useful for achieving robust stabilization of the altitude control. Accordingly, we propose a sliding mode control strategy without chattering. The sliding mode control proposed removes the chattering phenomenon by replacing a sign function with a high-slope saturation function. The control algorithm is derived from the Lyapunov stability theorem. Moreover, we have assumed that the actuators are able to respond quickly and accurately and we have not enforced limits on the control signals for a real-time application. Finally, to verify the satisfactory performance of proposed nonlinear control law, several simulations and experimental results of the Chattering-free sliding mode control for the Quad-rotor aircraft in the presence of bounded disturbances are presented.

Estimation of leaf area index in onion (Allium cepa L.) using an unmanned aerial vehicle

Leaf area index ( LAI ) is one of the most common indices in agronomy , being a parameter associated with physiological processes. Canopy cover and structure are related to LAI and they have effects on the interaction between crops and the environment. The aim was to evaluate a non-destructive method to measure canopy cover in an onion crop using an unmanned aerial vehicle (UAV). A field experiment was conducted in a commercial onion plot irrigated with a centre pivot system during the 2010 irrigation season. Several data sampling events were carried out in order to determine leaf area in eight experimental plots. In each one of these plots, aerial photographs were taken using a vertical take-off and landing (VTOL) quadrotor aircraft. Canopy cover ( CC ) was obtained by means of software developed for this study. The maximum value of LAI represents a CC of 56%, which is high for the characteristics of this crop. Three models were used to analyse the relationship between leaf area index and canopy cover. According to the results, a more linear relationship was found between both parameters during early growth stages than during more advanced stages. For the linear model, which best fitted all growth stages; the slope that relates CC with LAI was 2.877 with a coefficient of determination of 0.837. ► A non-destructive method was evaluated to measure canopy cover in an onion crop. ► Aerial digital photography from unmanned aerial vehicles was used. ► A software tool was developed to determine canopy cover. ► Relationship between canopy cover and leaf area index found using an automatic IR imaging system.

사이클릭 피치제어가 가능한 쿼드로터 항공기의 운동특성 분석과 LQR 제어

Typical quadrotor aircraft use four differential thrust vectors to control the motion. In this study, we design a quadrotor aircraft using collective and cyclic control to improve the shortcomings of existing quadrotor aircraft. The quadrotor aircraft with cyclic control can fly at various attitudes due to the excessive control degrees of freedom. Hence the quadrotor aircraft with cyclic control is suitable as high performance aircraft. In this study, modeling and stability analysis of the quadrotor aircraft have been performed using FLIGHTLAB. LQR control systems were designed using linear models at various flight conditions and verified through nonlinear simulations using MATLAB.