Showing papers by "Francesco Amato published in 2013"

Finite-Time Stability and Control

Abstract: Part I: Linear Systems.- Finite-time Stability Analysis of Continuous-Time Linear Systems.- Controller Design for the Finite-Time Stabilization of Continuous-Time Linear Systems.- Robustness Issues.- Finite-time Stability of Discrete-Time Linear Systems.- Finite-time Stability Analysis via PQLFs.- Part II: Hybrid Systems.- Finite-time Stability of Impulsive Dynamical Linear Systems.- Controller Design for the Finite-time Stability of Impulsive Dynamical Linear Systems.- Robustness Issues for Impulsive Dynamical Linear Systems.

Domain of attraction and guaranteed cost control for non-linear quadratic systems. Part 2: controller design

Abstract: This study addresses the problem of designing a guaranteed cost controller for non-linear discrete quadratic systems. More specifically, the main contribution concerns a sufficient condition for the existence of a state-feedback controller achieving a certain guaranteed cost, whenever the state trajectories start from a prescribed set of initial conditions. The controller design requires the solution of a convex optimisation problem involving linear matrix inequalities, which can be efficiently solved via available optimisation algorithms. Finally, the proposed design methodology is illustrated via an example concerning the attitude control of an unmanned aerial vehicle.

Robust and optimal tracking control for manipulator arm driven by pneumatic muscle actuators

Abstract: In this paper, a robust and optimal control problem for uncertain bilinear systems is formulated via a guaranteed-cost approach and then applied to tracking control design of a robotic arm actuated by Pneumatic Artificial Muscles (PAMs). Taking into account the nonlinear dynamics of the pneumatic actuators, the tracking error dynamics has been described as an uncertain bilinear systems, whereas unknown perturbations on robot dynamics and modelling mismatch are regarded as an external disturbance to be attenuated. Some numerical simulations are also given to demonstrate both robustness and optimality of the control performance in tracking desired trajectories with the required accuracy.

Validation of a model of the GAL regulatory system via robustness analysis of its bistability characteristics

Abstract: Background In Saccharomyces cerevisiae, structural bistability generates a bimodal expression of the galactose uptake genes (GAL) when exposed to low and high glucose concentrations. This indicates that yeast cells can decide between using either the limited amount of glucose or growing on galactose under changing environmental conditions. A crucial requirement for any plausible mechanistic model of this system is that it reproduces the robustness of the bistable response observed in vivo against inter-individual parametric variability and fluctuating environmental conditions.

Validation of a model of the GAL regulatory system via robustness analysis of its bistability

Abstract: Background: In Saccharomyces cerevisiae, structural bistability generates a bimodal expression of the galactose uptake genes (GAL) when exposed to low and high glucose concentrations. This indicates that yeast cells can decide between using either the limited amount of glucose or growing on galactose under changing environmental conditions. A crucial requirement for any plausible mechanistic model of this system is that it reproduces the robustness of the bistable response observed in vivo against inter-individual parametric variability and fluctuating environmental conditions. Results: We show how a control-theoretic analysis of the robustness of a model of the GAL regulatory network may be used to establish the model’s plausibility in characterizing the persistent memory of different carbon sources, without the need for extensive simulations. Chemical Reaction Network Theory is used to establish that the proposed network model is compatible with structural bistability. The robustness of each of the two operative conditions against fluctuations of the species concentrations is demonstrated by studying the Domains of Attraction of the corresponding equilibrium points. Finally, we use a global robustness analysis method based on Semi-Definite Programming to evaluate the modification of the bistable steady states induced by multiple parametric variations throughout bounded regions of the parameter space. Conclusions: Our analysis provides convincing evidence for the robustness, and hence plausibility, of the GAL regulatory network model. The proposed workflow also demonstrates the power of analytical methods from control theory to provide a direct quantitative characterization of the dynamics of multistable biomolecular regulatory systems without recourse to extensive computer simulations.

A Synthetic Biology approach to the realization of embedded feedback controllers for Chemical Reaction Networks

Abstract: Chemical Reaction Network (CRN) models based on the mass-action law play an important role in the life sciences, since they can be used to describe dynamical processes of interest in many fields of chemistry and biology. A fundamental challenge related to this kind of systems is represented by the lack, within the framework of Systems and Synthetic Biology, of a general methodology to design control systems for CRNs. The main issue addressed by this work is the development of a general methodology for designing embedded feedback control schemes for an assigned CRN, i.e. controllers that are themselves realizable through a CRN. In particular, we illustrate the effectiveness of the proposed approach by designing a proportional feedback controller for a well-characterized biochemical system.

A lumped parameter model for the analysis of the motion of the muscles of the lower limbs under whole-body vibration

Abstract: Through a lumped parameter modelling approach, a dynamical model, which can reproduce the motion of the muscles of a human body standing in different postures during Whole Body Vibrations (WBVs) treatment, has been developed. The key parameters, associated to the dynamics of the motion of the muscles of the lower limbs, have been identified starting from accelerometer measurements. The developed model can be usefully applied to the optimization of WBVs treatments which can effectively enhance muscle activation.

Invariant sets and guaranteed cost control of nonlinear quadratic systems

Abstract: This paper addresses the problem of designing a guaranteed cost controller for continuous-time nonlinear quadratic systems. The main result is a sufficient condition for the existence of a linear state feedback controller achieving an assigned guaranteed cost, whenever the state trajectories remain within a suitable invariant set. The conditions are cast in the form of Linear Matrix Inequalities (LMIs), which can be efficiently solved via available optimization algorithms. The effectiveness of the devised approach is illustrated through an example concerning the attitude control of an unmanned aerial vehicle.

Robust control of quadratic systems with norm bounded uncertainties

Abstract: This paper deals with the problem of the stabilization of uncertain quadratic systems via state feedback. The main contribution of the paper is a control design methodology which enables to find a robust controller guaranteeing for the closed-loop system: i) the local asymptotic stability of the zero equilibrium point; ii) the inclusion of a given polytopic region into the domain of attraction of the zero equilibrium point. This design procedure involves the solution of a Linear Matrix Inequalities (LMIs) feasibility problem, which can be efficiently solved via available optimization algorithms. A numerical example shows the effectiveness of the proposed methodology.

From touch to brain control: augmenting communication in persons with ALS.

Abstract: Brain Computer Interface (BCI) systems aim to provide people with severe motor impairment with an additional/alternative channel to communicate and interact with the external world. At the state of the art there are several custom computer programs specifically developed to be controlled through a BCI. However from the end users' point of view it is important to become familiar with their own assistive device before the BCI represents the only way to access it. The Brindisys project aims at designing and developing a general assistive technology to support communication and autonomy in people with Amyotrophic Lateral Sclerosis (ALS) from the onset of the disease to the locked-in phase. The prototype consists of a specific interface allowing for communication and environmental control that can be managed both with conventional/assistive input devices and with a P300-based BCI. This work describes the system functionalities and reports the results of a preliminary assessment with end users and healthy control subjects.