Omar Santos

Approximation of Control Laws with Distributed Delays: A Necessary Condition for Stability

The implementation of control laws with distributed delays that assign the spectrum of unstable linear multivariable systems with delay in the input requires an approximation of the integral. A necessary condition for stability of the closed-loop system is shown to be the stability of the controller itself. An illustrative multivariable example is given.

Robust nonlinear real-time control strategy to stabilize a PVTOL aircraft in crosswind

A robust control strategy to stabilize a PVTOL aircraft in the presence of crosswind is proposed in this paper. The approach makes use of Robust Control Lyapunov Functions (RCLF) and Sontags universal stabilizing feedback. A nonlinear dynamic model of the aircraft taking account the crosswind has been developed. Likewise, a robust nonlinear control strategy is proposed to stabilize the PVTOL aircraft using RCLF, and we have employed the Riccati equations parameters to compute and tune it in real-time. To validate the proposed control strategy, various simulations have been carried out. The controller has been also applied in real-time to a PVTOL prototype undergoing crosswinds. The experimental results show the good performance of the control algorithm.

Nonlinear and optimal real-time control of a rotary-wing UAV

In this contribution nonlinear stabilizing and optimal nonlinear control strategies for a quadrotor mini helicopter are addressed. These control strategies are an alternative for the control of flying machines not much explored yet. Simulation and real-time experiences are presented in this contribution. Nonlinear stabilizing control algorithm has been successfully implemented on an autonomous aerial vehicle and demonstrates an acceptable performance.

Real-time Stabilization of a Quadrotor UAV: Nonlinear Optimal and Suboptimal Control

In this paper a nonlinear suboptimal stabilizing control strategy based on Control Lyapunov Functions (CLF) is synthesized and applied to a quadrotor helicopter. Sufficient conditions are obtained for this control law to ensure the asymptotic stability of the closed loop system. Furthermore, a particular methodology to find a CLF candidate for nonlinear affine system is also presented, which is highly relevant because the dynamical model representing the VTOL aerial vehicles have this affine structure. Using this CLF candidate, we are able to synthesize a nonlinear stabilizing optimal control law which allows energy saving. Numerical simulations were developed for both control strategies and real time experiments have been performed using the nonlinear stabilizing control algorithm. The numerical simulations have shown a successful performance of the autonomous aerial vehicle.

Robust Control Algorithm for a Rotorcraft Disturbed by Crosswind

A nonlinear stabilization of vertical take-off and landing aircrafts exposed to wind is presented. The algorithm is based on a robust control Lyapunov function approach and rejects disturbances without knowledge of them. Two nonlinear models considering the disturbances are proposed. Simulations and experimental results show the good performance of the proposed control strategy.

Embedded robust nonlinear control for a four-rotor rotorcraft: Validation in real-time with wind disturbances

An embedded robust nonlinear controller to stabilize a four-rotor rotorcraft in presence of crosswind is developed in this paper. A previous dynamical system of the aircraft taking in account aerodynamical effects induced by lateral wind is conceived using the Newton-Euler approach. The stability analysis and robustness with respect disturbances is proved using the Lyapunov theory. Simulations have been accomplished to validate the performance of the proposed control schema. Additionally, a prototype with an embedded control system was created to prove, in real-time, the effectiveness and robustness of the proposed algorithm. Experimental results have illustrated the good behavior of the closed-loop system even in presence of several disturbances.

Discrete optimal control for a quadrotor UAV: Experimental approach

In this paper we propose a discrete time optimal control law to stabilize the four-rotor rotorcraft in attitude and position. The main objective of this kind of control law is to save energy and therefore increase the effective time in takeoff and hover flight phases for this robotic platforms. The optimal control law is synthesized considering a infinite horizon combined with an exact linearization by applying a nonlinear control law over nonlinear equations describing the robot dynamic model. The control law obtained is simple, easy and better adapted to be programmed in a micro-controller. Both simulation and experimental test and results show a satisfactory UAV behavior.

Optimized Discrete Control Law for Quadrotor Stabilization: Experimental Results

This paper deals with the real-time stabilization of a Quadrotor mini helicopter applying a discrete optimal control. A discrete control strategy is better adapted to be executed in a micro-controller, therefore better results are expected with respect to continuous case. Furthermore, the optimal control law allows to helicopter to save energy and then increase its time of flight. The discrete optimal control law is synthesized considering an infinite horizon together with an exact linearization of the nonlinear dynamics of flying vehicle. At the end of this procedure the optimal control law obtained through an exact linearization is simple and easier to tune compared to the optimal strategy where the exact linearization is not performed. Taking into account the obtained experimental results, the proposed control technique produces an appropriate stabilization of the mini UAV.

Robust stabilization of nonlinear time delay systems: A complete type functionals approach

Abstract The robust stabilization of some classes of nonlinear delay systems with nominal linear delay system is addressed. The form of the controller is not an a priori proposal, but it is the result of a synthesis relying on the use of complete type Lyapunov–Krasovskii functionals, leading to distributed delay linear or nonlinear robust control laws. Simulation results of the stabilization of a chemical refining process demonstrate the good performance of the proposed approaches.

On the tracking trajectory using optimal control in a quadrotor helicopter: Experimental results

This paper is about the control tracking trajectories with a finite optimal strategy using quadcopter helicopter. We performed a lot of experiments to obtained a statistic energetic comparative analysis with PID and optimal control laws. The experimental results have shown that the optimal control is better than PID control based on energy consumption.