Ivan Gonzalez-Hernandez

Second order sliding mode controllers for altitude control of a quadrotor UAS

This article deals with the design and real-time implementation of three second order sliding mode controllers for the altitude tracking of a quadrotor aircraft. A comparative study based on the analysis of the tracking error was performed in order to determine the controller presenting the best performance in a real-time application at outdoors environments. The compared strategies were the Classical First Order Sliding Mode Controller, the Super Twisting Sliding Mode Controller, the Modified Super Twisting Sliding Mode Controller and the Nonsingular Terminal Super Twisting Sliding Mode Controller. The last three controllers are based on the second order sliding mode technique, and they ensure robustness with respect to modeling errors even under external disturbances while reducing the chattering phenomenon in comparison with first order sliding mode controllers. Lyapunov stability theory is used to prove convergence in finite time of the altitude tracking error in the different proposed control laws. In order to demonstrate the effectiveness of the proposed solutions, an extensive set of simulation and real-time experimental results are presented.

Altitude control improvement for a Quadrotor UAV using integral action in a sliding-mode controller

In this paper, a robust altitude control scheme is proposed for a mini-Quadrotor UAV system based on sliding mode controller with an integral action to eliminate the steady-state error induced by the boundary layer in order to achieve asymptotic convergence to the desired altitude with continuous control input. The proposed integral sliding mode controller is chosen to ensure the stability and robustness of overall dynamics during the altitude control at a desired height reference on the z-axis. Furthermore, we propose a Control Lyapunov Function (CLF) via Lyapunov theory in order to construct the robust stabilizing controller and demonstrate the stability of the z-dynamics of our system. A suitable sliding manifold is designed to achieve the control objective. At last, the theoretical results are supported by different simulation tests to verify the robustness and effectiveness of proposed robust control scheme in presence of bounded external disturbances.

Disturbance rejection for a Quadrotor aircraft through a robust control

This paper addresses the problem of designing and experimentally validating a nonlinear disturbance observer, focus on the attitude regulation control problem of a quad-rotor in presence of external disturbances. The proposed nonlinear observer scheme is based on the angular velocity measurements and the control inputs in order to compensate external disturbances. The stability analysis of the nonlinear observer scheme is proven via the use of Lyapunov theory. Finally, simulation and experimental results in a education platform are presented to show the effectiveness of the proposed nonlinear algorithm in presence of external disturbances.

Super Twisting vs Modified Super Twisting algorithm for altitude control of an Unmanned Aircraft System

This article proposes two control strategies to track a desired altitude of an Unmanned Aircraft System (UAS). These strategies are a Super-Twisting Sliding Mode Controller (Super Twisting-SMC) and a Modified Super-Twisting Sliding Mode Controller (Modified Super Twisting-SMC), both controllers are robusts and present a satisfactory effectiveness even under external disturbances. The Lyapunov Stability Theory is used to guarantee the asymptotic convergence of the altitude tracking error in both control laws. To demonstrate the performance of the proposed solutions, a set of simulation results and experimental results are presented. To carry out the experiments an holonomic quad-rotor UAS is used and their altitude is obtained by using a Motion Capture System. From the theoretical and experimental results it can be proved that the Modified Super Twisting-SMC presents a faster response than the Super Twisting-SMC.

Altitude control of an Unmanned Aircraft System using a Super-Twisting controller based on High Order Sliding Mode Observer

In this paper, the altitude tracking problem for an Unmanned Aircraft System (UAS) is considered under the assumption that the altitud velocity is unknown. Since in a practical implementation the employed sensors used to measure the altitude (Barometer and GPS) do not provide the altitude velocity. The proposed strategy was designed by using a Super-Twisting controller based on a High Order Sliding Mode Observer. A comprehensive stability analysis based on the Lyapunov Stability Theory guarantees the convergence of the tracking error in finite time. To demonstrate the performance of the proposed solution, a set of simulation results are presented.

Simulation and robust trajectory-tracking for a Quadrotor UAV

In this article, a robust control algorithm using sliding modes is proposed for the efficient regulation on the trajectory tracking tasks, in the nonlinear, multivariable, quadrotor system model, that ensures the asymptotic convergence to a desired trajectory (reference signal - r(t)) in presence of all possible uncertainties and external disturbances. A smooth piecewise continuous function trajectory is proposed where the corresponding derivatives are bounded. Furthermore, we assume that the disturbances on the vehicle are bounded and the signal r(t) are available on line. The proposed algorithm employs a sliding surface based on the errors generated from the current state of the path in order to reach the desired reference r(t). The stability analysis of the closed-loop control system is proven via the use of Lyapunov theory. Finally, a numerical simulation of tracking a smooth trajectory is performed to demonstrate the validity and effectiveness of the proposed robust algorithm in presence of disturbances onto the vehicle.

Real-time altitude control for a quadrotor helicopter using a super-twisting controller based on high-order sliding mode observer

This article addresses the problem of altitude tracking for unmanned aircraft system when the altitude velocity is unknown, because in a practical implementation, the available sensors used to measure the vehicle’s altitude (barometer, global positioning system, laser, etc.) do not provide the altitude velocity. We propose a control strategy based on both the super-twisting sliding mode controller as well as a high-order sliding mode observer to control and to estimate the altitude velocity, respectively. A comprehensive stability analysis for the combined controller–observer based on the Lyapunov stability theory is presented, ensuring the asymptotic convergence of the tracking error under external bounded disturbances. To demonstrate the performance and the effectiveness of the proposed solution, an extensive set of real-time experimental tests performed at outdoor environments is presented.

Robust trajectory-tracking control design for a small Quad-rotor aircraft via sliding modes

This article addresses the problem of a real-time implementation trajectory control for a miniature Quad-rotor aircraft along a time-depedent trajectory outdoor. A robust algorithm control based on sliding mode approach is proposed for the trajectory-tracking task, that ensures the convergence to a desired path r(t) in a finite time. A polynomial smooth curve trajectory is selected as reference signal in where the corresponding derivatives of the function are bounded. The proposed solution consists of implementing a real-time control law based on sliding mode using GPS measurements in order to obtain the position in the plane XY to accomplish the desired trajectory. A Lyapunov candidate function is used in order to obtain the control law as well as corresponding stability analysis of the system. Simulation and experimental results of trajectory-tracking control are presented to assess the performance and robustness of the proposed controller in the presence of small perturbations outdoor.

Real-time parameters identification for a quad-rotor mini-aircraft using adaptive control

In this article an adaptive controller is developed in order to estimate the inertia tensor, the mass and the wind parameters (considering wind as a parameter in the input) for the underactuated quad-rotor mini-aircraft. Experimental tests are performed in an educational platform. The proposed control scheme uses the parameter estimation issued from gradient type algorithm. Finally simulations and experimental results are included to illustrate the performance of the parameters identification for the quad-rotor helicopter.

Linear observer for estimating wind gust in UAV's

This paper deals with the problem of estimating the disturbances due a wind gust in a Quadrotor rotorcraft. A linear observer with integral action for estimating the disturbance due a wind is presented. Simulation and real-time result are presented for test performance of control law proposed. The real-time test was ralized in hover fly mode based on GPS sensor signal.