M. Lopez-Martinez

A Multivariable Nonlinear H ∞ Controller for a Laboratory Helicopter

This paper considers the problem of a nonlinear H∞design for a laboratory twin rotor system. This mechanical device features a highly nonlinear strongly coupled dynamics, which constitutes a challenge for many classical linear control techniques. The approach presented in this paper considers a nonlinear H∞disturbance rejection procedure on the reduced dynamics of the rotors, including integral terms on the tracking error to cope with persistent disturbances. The resulting controller exhibits the structure of a nonlinear PID, with time-varying constants according to the system dynamics. The methodology has been tested by experimental results using a laboratory helicopter.

Constructive feedback linearization of underactuated mechanical systems with 2-DOF

In the last years, the control community has developed several and powerful methods to control nonlinear systems, especially for underactuated mechanical systems. Thus, methods based on passivity, like Interconnection and damping assignment passivity–based control (IDA-PBC) and Controlled Lagrangians have solved many interesting control problems for particular full classes of systems. Usually, the solutions of these methods relies on solving a set of partial differential equations (PDEs), which is not always possible. This paper presents a constructive methodology to control underactuated mechanical systems with 2-DOF, by means of classical feedback linearization and Lyapunov design. The steps of the design are presented following a simple pseudo-code1, that allows us to redesign a proposed fictitious output in a constructive way. The methodology has been tested with three very well-known underactuated mechanical systems: the inertia wheel pendulum, the pendulum on a cart and the rotary pendulum. The obtained solution for the inertia wheel pendulum takes into account the friction, since recent works have shown that it cannot be neglected. In the case of the planar pendulum on a cart, the solution is quite similar to the one obtained by Controlled Lagrangians but with better performance, and, furthermore, our planar pendulum solution paves the way to obtain a new solution for the rotary pendulum, or the so–called Furuta pendulum, that, to the best of our knowledge, has the largest attraction basin presented and experimentally tested so far. The attraction basin tends to the whole upper half plane by increasing a control gain.

Vision-Based System for the Safe Operation of a Solar Power Tower Plant

In this paper several vision-based systems for the operation of a solar power tower plant are shown. These systems detect the presence of clouds next to the sun and compute a field coverture factor which features the area of the heliostat field that is shadowed by them. This cloud detection process is fundamental in order to preserve the integrity of the solar central receiver located at the top of the tower of these solar plants. These systems prevent the rupture of the receiver by thermal stress.

Control no lineal robusto de una maqueta de helicóptero con rotores de velocidad variable

This paper presents the design of a robust nonlinear controller for a scaled helicopter. This device features rotors with fixed angles of attack blades, and is controlled by changing the speed of the rotors using two direct drive engines. The resultant system is multivariable (2 inputs and 4 outputs), highly nonlinear and strongly coupled. The application presented in this paper includes the design of a robust controller that rejects persistent disturbances, which is based on feedback linearization and two external controllers. These controllers have PID structure and are designed using LQR regulators extending the state vector with the integral of the positions. The methodology has been verified by means of experimental results

An H/sub /spl infin// controller for a double rotor system

In this paper the design of an H/sub /spl infin// controller for a double rotor system is presented. This mechanical set features the characteristics of being a multivariable, highly nonlinear, strongly coupled and non-minimum phase system. The H/sub /spl infin// theory for linear systems has been applied after linearizing the dynamics by means of feedback linearization.

Cloud detection system for a solar power tower plant

In this paper a cloud detection system for the operation of solar power tower plants is shown. The presence of clouds is detected at a region next to the sun, which is fundamental in order to preserve the integrity of the solar central receiver, which is located at the top of the tower of these solar plants. This system prevents the rupture of the receiver by thermal stress.

On Singular Perturbations of Unstable Underactuated Mechanical Systems With Underactuation Degree ≥ 1

Abstract 10 years ago, K.J. Astrom proposed that the essence of the complex control problem originated by the joint of the pilot–&–aircraft can be captured on labs, by means of unstable underactuated mechanical systems. Thus, the unactuated part describes the autonomous aircraft dynamics and the actuated the piloted one. In this c onstructive approach we propose a nonlinear controller based on classical feedback linearization and singular perturbation theory, which has a compact and explicit expression , providing the designer a handle to address transient performance and robustness issues to dominate undesirable friction and/or drag effects, even in the unactuated coordinates. Further, partial differential equations need not to be solved. A multivariable example and successful experiments on the Furutas pendulum are reported. To the best of authors’ knowledge it has the largest attraction basin experimentally tested so far.

Energy-aware consensus algorithms in networked sampled systems

Abstract This work presents a method to analyze the convergence to consensus of a network of first order linear systems, when the signals associated to the interconnections are sampled from the continuous time systems. In order to minimize the energy consumed in the process of communication, we will look for the optimal sampling time such that the consensus is reached in a minimum number of iterations (communications). The analysis is performed by minimizing several objective functions that take into account a measure of the convergence rate to reach a consensus. These objective functions mainly depend on the eigenvalues of the sampled transition matrix of the system. Finally, we present a case study based on the torus topology, where a simple case of communication is analyzed and the optimal sampling time to reach a consensus is obtained.

Linealizacion por realimentacion constructiva de sistemas mecanicos con grado de subactuacion 1 inestables con friccion

In the last years, several methods to control nonlinear underactuated mechanical systems have been developed. In fact, these nonlinear methods have solved interesting control problems. Nevertheless, the solutions of these methods relies on solving a set of partial differential equations, which is not always possible. This article presents a constructive methodology to control a class of unstable underactuated mechanical systems with underactuation degree one. The design is based on classical feedback linearization and Lyapunov redesign. The methodology is based on proposing a dummy output that allows its redesign in a constructive way to solve the problem, giving rise an explicit and compact control law that allows to take into account the friction even in the underactuated coordinates.

Energy-Aware Consensus for Networked Sampled MIMO Systems

Abstract This work presents a method to compute the optimal sampling time that makes N MIMO agents converge to the consensus state with minimum energy consumption. In its turn, every agent in the network is composed of n continuous time first order linear systems. The communication is done in discrete time, sampling all the signals associated to every agent at the same sampling time. In order to minimize the energy consumed in the process of communication, we will look for the optimal sampling time such that the consensus is reached in a minimum number of iterations. The analysis is performed by minimizing objective functions that take into account a measure of the convergence rate to reach a consensus. These objective functions mainly depend on the eigenvalues of the sampled transition matrix of the system. The method can be applied to medium/large scale networks, since it requires computing the eigenvalues of the adjacency matrix just once. Finally, we present a case study based on the torus topology, where a MIMO case of communication (1000 systems) is analyzed, obtaining the optimal sampling time to reach the consensus.