Manuel G. Ortega

Backstepping/nonlinear H ∞ control for path tracking of a quadrotor unmanned aerial vehicle

This paper presents a nonlinear robust control strategy to solve the path tracking problem for a quadrotor unmanned aerial vehicle. The helicopter motion equations is obtained by the Lagrange- Euler formalism. The control structure is performed through a nonlinear Hinfin controller to stabilize the rotational movements and a control law based on backstepping approach to track the reference trajectory. Finally, simulations results in presence of aerodynamic moments disturbances and parametric uncertainty is carried out to corroborate the effectiveness and the robustness of the strategy proposed.

Nonlinear H∞ Controller for the Quad-Rotor Helicopter with Input Coupling

Abstract This paper presents a nonlinear H∞ control law for underactuated mechanical systems with input coupling. Apart from the controlled degrees of freedom (DOF), the proposed controller considers the dynamics of the remaining DOF in the cost variable, which allows to stabilize them. The underactuated mechanical system is normalized to obtain a diagonal inertia matrix allowing to weigh with various criteria different DOF. This controller is applied to the quadrotor helicopter to perform path tracking, whose mechanical structure has been modified in order to obtain coupling between longitudinal and lateral movements with roll and pitch motions. Simulation results in presence of aerodynamic disturbances, structural and parametric uncertainties are presented to corroborate the effectiveness and the robustness of the proposed controller. Copyright

Path Tracking of a UAV via an Underactuated Control Strategy

In this study, a nonlinear robust control strategy designed for underactuated mechanical systems is proposed in order to solve the path tracking problem for a quadrotor unmanned aerial vehicle. An underactuated nonlinear controller based on the six degrees of freedom dynamic model is designed to control the helicopter attitude and altitude in the inner-loop. The outer-loop control is performed using a model-based predictive controller ( MPC ) to track the reference trajectory. The robust performance achieved with the proposed control strategy is checked by simulation in the presence of aerodynamic disturbances, unmodelled dynamics and parametric uncertainties.

Improved design of the weighting matrices for the S/KS/T mixed sensitivity problem-application to a multivariable thermodynamic system

This paper describes an improved design procedure for the weighting matrices of the S/KS/T mixed sensitivity problem. Using low-order models, as usual in industrial processes, and based on recent works, the new design will allow to significantly reduce the time response overshoots, without degrading the speed of these responses. Weighting matrices are designed in such a way that they depend only on a few parameters, which can be easily adjusted by means of the proposed methodology. Experimental results in the simultaneous control of two temperatures of a pilot plant (which constitutes a typical example of industrial process) are included in order to validate the proposed methodology.

MPC with Nonlinear ℋ∞ Control for Path Tracking of a Quad-Rotor Helicopter

Abstract This paper presents a predictive and nonlinear robust control strategy to solve the path tracking problem for a quadrotor helicopter. The dynamic motion equations are obtained by the Lagrange-Euler formalism. The control structure is performed through a model-based predictive controller (MPC) to track the reference trajectory and a nonlinear ℋ ∞ controller to stabilize the rotational movements. Simulations results in presence of aerodynamic disturbances and parametric uncertainty are presented to corroborate the effectiveness and the robustness of the proposed strategy.

Robust PID Control of the Quadrotor Helicopter

Abstract In this paper a robust PID control strategy via affine parametrization is designed for an multivariable nonlinear unmanned aerial vehicle. The robustness of the controlled system is assured by using the H ∞ norm of the weighted complementary sensitivity function. Simulation results carried out using a complete nonlinear model are shown, wherein the performance achieved with this control strategy is shown.

Modeling of a Cocurrent Rotary Dryer

Parametric mathematical models of drying plants include balance equations and correlations that should be adjusted for each case depending on the material to be dried and the installation. In some cases, variable parameters are simplified as constants, providing an inaccurate model. This article presents a model of a cocurrent dryer, showing the process by which it is arrived at, and raises suggestions for some improvements in the determination of the drying rate to obtain a more accurate analytical expression. Preliminary tests are presented that can be performed on the solid material and the model of a pilot plant is validated.

Anticipatory strategies of team-handball goalkeepers

Abstract This study seeks to discover whether handball goalkeepers employ a general anticipatory strategy when facing long distance throws and the effect of uncertainty on these strategies. Seven goalkeepers and four throwers took part. We used a force platform to analyse the goalkeepers movements on the basis of reaction forces and two video cameras synchronised at 500 Hz to film the throw using 3D video techniques. The goalkeepers initiated their movement towards the side of the throw 193 ± 67 ms before the release of the ball and when the uncertainty was reduced the time increased to 349 ± 71 ms. The kinematics analysis of their centre of mass indicated that there was an anticipatory strategy of movement with certain modifications when there was greater uncertainty. All the average scores referring to velocity and lateral movement of the goalkeepers centre of mass are significantly greater than those recorded for the experimental situation with bigger uncertainty. The methodology used has enabled us to tackle the study of anticipation from an analysis of the movement used by goalkeepers to save the ball.

Bifurcation analysis of a feedback system with dead zone and saturation

An experimental example has been presented showing how nonlinearities affect the dynamic behavior of a DC servomechanism controlled by a proportional controller. The analysis has been developed using tools supplied by classical methods for feedback system analysis based on the describing function method. The case studied is a very good and simple example of a feedback system where a saddle-node bifurcation of periodic orbits occurs. This bifurcation is very interesting because it explains the coexistence of a stable equilibrium at the operating point with a stable limit cycle for large perturbations. The major advantage of the bifurcation analysis developed is that it supplies a single unified framework for representing all the different behavior modes the system can display. Finally, these results have been tested using laboratory equipment.

Design, automation and control of a two-stage, two-load-demand experimental refrigeration plant

This paper describes the design, implementation and automation of a two-stage, two-load-demand experimental refrigeration plant. The facility is fully configurable, since cycles with one or two compression stages, and one or two load demands can be set up. Detailed description of the experimental facility concerning its physical components, actuators and sensors is addressed, as well as low-level control and communication bus issues. The high-level control environment and its communication with the low-level controller are also approached. Furthermore, a well-known in industry decentralised control strategy is applied to a one-stage, two-load-demand refrigeration cycle, analysing some preliminary control results from an energy efficiency point of view.