Warody Lombardi

A predictive control scheme for systems with variable time-delay

This article deals with the robust control design problem for linear time invariant systems affected by variable feedback delay. Constraints on the system state are considered in the system description. The starting point is the construction of a predictive control law which guarantees the existence of a nonempty robust positive invariant (RPI) set with respect to the closed-loop dynamics. Subsequently, an iterative algorithm is proposed in order to obtain an approximation of the maximal RPI set. The problem can be treated in the framework of piecewise affine systems due to the explicit formulations of the control law obtained via multiparametric programming.

On the Polyhedral Set-Invariance Conditions for Time-Delay Systems

Abstract In this paper the concept of set invariance for time-delay systems is introduced with a specific attention to the linear discrete-time case. We are interested in the definition of a D(elay) -invariant set with respect to a bounded polyhedral subset of the state-space. D -invariance conditions are derived based on the Minkowski addition in a first stage, and subsequently translated in feasibility-based tests in order to obtain an efficient computation time

Robust invariance for a class of time-delay systems with repeated eigenvalues

Abstract This paper focuses on the set invariance of linear systems characterized by transition matrices with repeated eigenvalues and geometric multiplicity inferior to the algebraic multiplicity. The goal is to model the variable delay affecting the input by polytopic type of uncertainty in order to preserve the linear convex description. It is shown that the embedding problem can be translated into a polytopic containment problem and a iterative approach to the construction of tight, low complexity embedding (simplex) is proposed. A design procedure for the construction of a robust positively invariant set for the system affected by time delay and subject to input and state constraints completes the paper.

State admissible sets for discrete systems under delay constraints

This paper addresses the stabilization problem of a class of linear discrete-time systems with input delays. More precisely, by taking into account the presence of input/state constraints, an analysis of the safety functioning is performed based on an admissible set description.

Sensors fault diagnosis for a BMS

This paper deals with sensor fault diagnosis for a battery management system (BMS). The diagnosis procedure consists on the detection and isolation of sensor faults. A new battery pack design, composed by the cells and sensors, is introduced. Three sensors are considered: voltage, current and temperature. The algorithms are simple and efficient, even for multiple faults, so as to be low-cost from computation and power point of view. Examples are developed during the paper to show the effectiveness of the technique.

Feedback Stabilization and motion synchronization of systems with time-delay in the communication network

Abstract This paper is dedicated to the stabilization problem of dynamical systems in the presence of variable time-delay in the communication channel which is handled at the discretization stage by means of a guaranteed uncertainty approximation technique. In this context, the proposed stabilization methodology will be based on a Lyapunov-Krasovskii candidate leading finally to Linear Matrix Inequalities formulations for the controller synthesis. The motion synchronization control of two interconnected subsystems linked by a network is considered a possible application of these techniques.

Exponential L 2 -stability for a class of linear systems governed by continuous-time difference equations

Linear systems governed by continuous-time difference equations cover a wide class of linear systems. From the Lyapunov-Krasovskii approach, we investigate L 2 -stability for such a class of systems. Sufficient conditions, and in some particular cases, necessary and sufficient conditions for exponential L 2 -stability are established, for multivariable systems with commensurate or rationally independent delays. An analysis of discontinuities evolution appearing in the system response is proposed. Finally, a robustness issue is discussed for time-varying delays.

A Bridge Between Lyapunov-Krasovskii and Spectral Approaches for Difference Equations

Stability and performance properties of a class of systems governed by linear continuous-time difference equations are investigated. These properties are linked with those of discrete-time linear systems. This analysis is carried out via two approaches, namely Lyapunov-Krasovskii techniques and spectral theory. A discussion on robustness issues is made.

Energy management via PI control for data parallel applications with throughput constraints

This paper presents a new proportional-integral (PI) controller that sets the operating point of computing tiles in a system on chip (SoC). We address data-parallel applications with throughput constraints. The controller settings are investigated for application configurations with different QoS levels and different buffer sizes. The control method is evaluated on a test chip with four tiles executing a realistic HMAX object recognition application. Experimental results suggest that the proposed controller outperforms the state-of-the-art results: it attains, on average, 25% less number of frequency switches and has slightly higher energy savings. The reduction in number of frequency switches is important because it decreases the involved overhead. In addition, the PI controller meets the throughput constraint in cases where other approaches fail.

Design and implementation of a Predictive Control strategy for power management of a wireless sensor network

Technological advances have made wireless sensor nodes cheap and reliable enough to be brought into various application domains. The limited energy capacity of sensor nodes is the key factor that restricts their lifespan. In this paper, a Predictive Control strategy for Dynamic Power Management of a set of wireless sensor nodes is proposed. The control formulation is based on Model Predictive Control with constraints and binary optimization variables, leading to a Mixed Integer Quadratic Programming problem. The proposed control algorithm guarantees services and performances levels with a minimum number of active nodes and/or a minimum load on such components. The strategy is evaluated on a real test-bench with wireless sensor nodes equipped with batteries and harvesting systems. Experimental results show the effectiveness of the proposed control method.