Alessandro Pisano

University of Cagliari | UNICA · Department of Electrical and Electronic Engineering

This paper addresses the state estimation and unknown input reconstruction in strongly observable linear systems under the so-called matching conditions. Our proposal extends previous approaches to predefined-time state estimation, which involved the use of a pair of time-delay observers, adapting them to the framework of sliding mode observation i...

The primary concern of the present chapter is to address the distributed leader-following consensus tracking problem for a network of agents governed by uncertain diffusion PDEs with the Neumann-type boundary actuation and uncertain spatially varying diffusivity. Except for the “leader” agent that generates the reference profile to be tracked, all...

This present article addresses the feedback control design problem of in-line liquid flow heating units used to process silicon wafers in the semiconductor industry. A physics-based model is developed to describe the thermal behavior of the heater and the liquid circulating in it. Under sensible approximations, process dynamics are shown to be gove...

This paper proposes a certainty equivalence model predictive control (MPC) approach for the operation of islanded microgrids with a very high share of renewable energy sources. First, to make the MG model more realistic, the conversion losses of the storage units and the conversion losses of the power electronic devices are considered by the quadra...

This paper focuses on the robust distributed secondary voltage restoration control of AC microgrids (MGs) under multiple communication delays and nonlinear model uncertainties. The problem is addressed in a multi-agent fashion where the generators’ local controllers play the role of cooperative agents communicating over a network and where electric...

A network of agents, modeled by a class of wave PDEs, is under investigation. One agent in the network plays the role of a leader, and all the remaining "follower" agents are required to asymptotically track the state of the leader. Only boundary sensing of the agent's state is assumed, and each agent is controlled through the boundary by Neumann-t...

This paper focuses on solving the problem of voltage restoration in droop-controlled inverter-based islanded micro-grids (MGs) under communication delays. To this aim, we propose a novel robust distributed secondary controller which is the combination between an integral sliding mode controller and a linear consensus scheme with constant weights. L...

This paper deals with the problem of voltage and frequency restoration in droop-controlled inverter-based islanded microgrids (MGs). The problem is solved using a novel tracking consensus secondary control protocol based on the sliding-mode approach, which not only guarantees the exact finite-time restoration among voltages and frequencies of an in...

A network of agents, modeled by a class of wave PDEs, is under investigation. One agent in the network plays the role of a leader, and all the remaining follower" agents are required to asymptotically track the state of the leader. Only boundary sensing of the agent’s state is assumed, and each agent is controlled through the boundary by Neumann-ty...

This paper proposes a design approach, based on the integral sliding mode control paradigm, devoted to provide robustness on multi-agent systems (MASs) executing arbitrary distributed optimization and consensus protocols which do not take this feature into account. Robustness is understood as the capability of rejecting the effect of exogenous dist...

In this chapter, some recent results of applications of sliding-mode control strategies for solving the AC microgrid secondary restoration control problem are discussed. The control problem is formulated in a distributed way in accordance with the leader–follower consensus paradigm thus avoiding centralized decision-making. The control schemes are...

This paper proposes a robust finite-time distributed tracking control problems for n-order non-linear multi-agent systems with a virtual leader in the presence of bounded disturbances and model uncertainties. The proposed algorithm is based on coupled n-order non-linear terminal sliding mode control which ensures the convergence of the agent's stat...

This paper proposes a robust finite-time distributed tracking control problems for n-order non-linear multi-agent systems with a virtual leader in the presence of bounded disturbances and model uncertainties. The proposed algorithm is based on coupled n-order non-linear terminal sliding mode control which ensures the convergence of the agent's stat...

A continuation of previous authors' work on adaptive parameter estimation for linear dynamical systems having irrational transfer function is presented in this work. An original modification of the gradient algorithm, inspired by the variable structure control techniques and additionally featuring a time-varying adaptation gain, is presented and an...

This paper proposes a robust finite-time distributed tracking control problems for n-order non-linear multi-agent systems with a virtual leader in the presence of bounded disturbances and model uncertainties. The proposed algorithm is based on coupled n-order non-linear terminal sliding mode control which ensures the convergence of the agent's stat...

In the present paper we deal with a class of open-loop unstable reaction-diffusion PDEs with boundary control and Robin-type boundary conditions. A second-order sliding mode algorithm is employed along with the backstepping method to asymptotically stabilize the controlled plant while providing at the same time the rejection of an external persiste...

An adaptive algorithm solving the on-line parameter estimation problem for a broad class of linear systems is proposed. The approach can be applied to systems with delay, distributed-parameter systems, fractional order systems, and others which are stable or stabilized by linear feedback. The proposed scheme can be applied to simultaneously track s...

In this chapter we show how the Integral Sliding-Mode Control design paradigm can be usefully applied in the framework of Multi-Agent Systems to allow the agents dynamics to be affected by unknown disturbances. Existing consensus-based algorithms for the distributed estimation of pre-specified quantities such as, e.g., the average or the median val...

In this paper, a novel control strategy to perform the finite-time restoration among voltages and frequencies of an islanded inverter-based microgrid is presented. The problem is attacked from a cooperative-based control perspective inspired to the tracking consensus paradigm. Sliding-mode based distributed algorithms are designed to enhance the un...

The position and attitude control of a six‐degree‐of‐freedom vehicle is dealt with in this paper. The actuation system is assumed to consist of a set of mono‐directional devices suitably located and directed. The model of the system is characterized by a large amount of uncertainties, disturbances and measurement errors. The state is assumed fully...

In this paper we propose a novel continuous-time protocol that solves the consensus problem on the median value, i.e., it provides distributed agreement in networked multi-agent systems where the quantity of interest is the median value of the agents' initial values. In contrast to the average value, the median value is a statistical measure inhere...

In this paper, we present a novel control strategy to perform the exact finite-time restoration among voltages and frequencies of an islanded inverter-based microgrid. The problem is attacked from a cooperative-based control perspective inspired to the tracking consensus paradigm. Ad-hoc chattering-free sliding-mode based distributed algorithms are...

A reaction–diffusion–advection equation with uncertain parameters, and additionally subject to disturbances of both matched and mismatched nature, is considered. It is assumed that only a finite number of point-wise sensing and actuation devices, suitably located in an equi-spaced manner along the 1-dimensional spatial domain of interest, is availa...

This paper deals with the problem of retaining the connectivity in a Mobile Ad-hoc communication mesh Network (MANET). A multi-agent systems perspective is taken, where primary mobile agents (PAs) can only communicate when the relative distance is less than a “visibility range”. PAs form a network that can become disconnected depending on how they...

In this paper we address the problem of voltage restoration and control of inverter-based islanded microgrid. The problem is attacked from a multi-agent systems consensus-based perspective at the microgrid's secondary control layer. An ad-hoc chattering-free second-order sliding-mode controlled is designed to achieve voltage restoration in a distri...

A Fault Detection and Diagnosis scheme able to deal with concurrent, incipient, sensor and actuator faults is presented. The architecture allows the diagnosis whenever the system's outputs are less than the number of faults. Residual generation is achieved by taking advantage from observer-based design, whereas the classification is performed by ex...

In this paper we present a novel discontinuous algorithm which cooperatively solves a distributed convex multi-agent optimization problem under a consensus constraint. The team performance function is the sum of local quadratic objective functions which are known to the local agent only. The proposed local interaction rule between the agents employ...

In this work we address the position and attitude control problems for autonomous vehicles in 6 Degrees of Freedom (DOFs), with monodirectional actuators and whose mathematical description includes uncertainties and disturbances. Quaternion-based guidance rules are proposed for attitude and position control at the kinematic level. The actuation sys...

In this paper we propose a distributed and cooperative approach to address the problem of coordinating the electric power demand of electric thermal systems in an urban environment. We model the network of electric thermal systems as a multi-agent system where each agent has only access to local information and ignores any global data such as the s...

In this chapter, an adaptive second-order sliding mode technique is exploited to optimize the efficiency of a variable-speed wind turbine. A revisited form of a recently proposed adaptation algorithm is proposed to deal with the characteristics and control requirements of the wind energy conversion system (WECS), particularly model uncertainties an...

In this paper, a novel adaptive second-order sliding mode technique to optimize the efficiency of certain types of variable-speed wind turbines is developed and analyzed. A revisited form of a recent adaptation algorithm is proposed to deal with the characteristics and control requirements of wind energy conversion systems (WECS), particularly mode...

Controlling highly uncertain nonlinear systems is in general a quite difficult task, for which Sliding Mode (SM) control has proved to be an effective option. This brief proposes a SM control strategy which combines a switched policy with a time-based adaptation of the control gain, thereby allowing to effectively deal with a very conservative prio...

This paper endows the second-order sliding mode control (2-SMC) approach with additional capabilities of learning and control adaptation. We present a 2-SMC scheme that estimates and compensates for the uncertainties affecting the system dynamics. It also adjusts the discontinuous control effort on-line, so that it can be reduced to arbitrarily sma...

In this paper Ionic Polymer-Metal Composites (IPMC) actuators motion control is addressed by using a new approach based on the modified fractional super twisting control strategy. We present the theoretical aspect of the proposed control strategy and then the performances of the controlling strategy are validated for an IPMC actuator by using an ad...

In this paper the problem of driving the state of a network of identical agents, modeled by boundary-controlled heat equations, towards a common steady-state profile is addressed. Decentralized consensus protocols are proposed to address two distinct problems. The first problem is that of steering the states of all agents towards the same constant...

The problem of designing an observer capable of reconstructing the continuous and discrete states for a class of switched linear systems is addressed. A stack of dynamical observers based on the super twisting algorithm with finite and uniform-in-the-initial-condition convergence is considered, which provides an estimate of the continuous state and...

The problem of boundary stabilization is considered for some classes of coupled parabolic linear PDEs of the reaction–diffusion type. With reference to coupled equations, each one equipped with a scalar boundary control input, a state feedback law is designed with actuation at only one end of the domain, and exponential stability of the closed-loop...

In this paper we propose a decentralized discontinuous interaction rule which allows to achieve consensus in a network of agents modeled by continuous-time first-order integrator dynamics affected by bounded disturbances. The topology of the network is described by a directed graph. The proposed discontinuous interaction rule is capable of rejectin...

The rotor speed estimation problem in electrical drives, based on shaft encoder measurements, has been dealt with by means of a digital approximate differentiator. The proposed differentiator is based on a digital VSC which is able to perform real 2-sliding modes, so that the observer discontinuous control is confined to the second total derivative...

This paper deals with a high-order sliding-mode approach to the observer-based output feedback control of a PEM fuel cell system comprising a compressor, a supply manifold, the fuel-cell stack and the return manifold. The treatment is based on a lumped parameter nonlinear modeling of the PEM fuel cell system under study. The suggested scheme assume...

This paper deals with applications of sliding-mode-based fractional control techniques to address tracking and stabilization control tasks for some classes of nonlinear uncertain fractional-order systems. Both single-input and multi-input systems are considered. A second-order sliding-mode approach is taken, in suitable combination with PI-based de...

In this paper a novel time-based adaptive second-order sliding mode (SOSM) technique to optimise the efficiency of a variable-speed wind turbine is developed and analised. A revisited form of a recent time-based adaptation algorithm is proposed to deal with the characteristics and control requirements of the wind energy conversion system (WECS), pa...

We consider the problem of boundary stabilization for a system of n coupled parabolic linear PDEs. Particularly, we design a state feedback law with actuation on only one end of the domain and prove exponential stability of the closed-loop system with an arbitrarily fast convergence rate. The backstepping method is used for controller design, and t...

A diffusion equation perturbed by uncertain disturbances of both matching and unmatching nature is considered. The problem of disturbance attenuation is tackled by means of the sliding-mode control approach. It is assumed that only a finite number of pointwise sensing and actuation devices, suitably located in an equi-spaced manner along the spatia...

The state observation problem is tackled for a system of n coupled reaction-diffusion PDEs, possessing the same diffusivity parameter and equipped with boundary sensing devices. Particularly, a backstepping-based observer is designed and the exponential stability of the error system is proven with an arbitrarily fast convergence rate. The transfo...

With reference to linear time invariant fractional-order systems, of both commensurate and non-commensurate type, a novel, gradient-based, procedure for the adaptive estimation of the delay parameter is presented in the current paper. The connections between the proposed delay estimation algorithm and a recently proposed technique for commensurate...

In this paper we present a review of our recent advancements in consensus-based cooperative control by using sliding-mode concepts for networked systems. In particular, strategies for achieving consensus in networks of persistently perturbed agents with static and switching network topologies, which can be disconnected for intervals of time, are di...

In this paper we propose a novel protocol to solve the consensus on the median value problem, i.e., the decentralized agreement problem for networked multi-agent systems where the quantity of interest is the median value as opposed to the average value of the agents' states. The median value is a statistical measure particularly robust to the exist...

This presentation focuses on two approaches, both based on second order sliding modes, for detecting faults and controlling certain classes of infinite dimensional systems. Two concrete applications will be presented. The first approach considers a three-dimensional distributed-parameter model of an industrial furnace and addresses the problem of d...

The primary concern of the present paper is to give an overview of the available results and methods in the field of second-order sliding mode based boundary control synthesis for uncertain and perturbed distributed parameter systems. We particularly aim at showing how the same basic algorithm (the combined Twisting/PD algorithm) can be applied to...

This paper deals with the distributed tracking control of a heat process having uncertain diffusivity and subject to a distributed disturbance whose L2 norm is bounded by a constant which is not known a priori. Under certain regularity assumptions on the disturbance and on the chosen reference profile, a distributed unit-vector control, with an ada...

Adaptive parameter estimation schemes for linear fractional-order processes of commensurate type are illustrated in the present note. A gradient-based scheme for commensurate order estimation is outlined first, and a combined gradient/leastsquares scheme for simultaneously estimating the commensurate order and the remaining process parameters is fi...

In this paper we investigate the properties of a decentralized consensus algorithm for a network of continuous- time integrators subject to unknown-but-bounded persistent disturbances. The proposed consensus algorithm is based on a discontinuous local interaction rule. Under certain restrictions on the directed switching topology of the communicati...

This paper considers the problem of achieving consensus in a network of agents whose dynamics consist of perturbed double integrators. The considered class of perturbations is a bounded additive uncertainty, different for each agent, and such that the maximal magnitude is the only information available a-priori. Agents are supposed to interact thro...

The primary concern of the present paper is the regulation of an uncertain wave process with collocated boundary sensing and Neumann-type actuation. It exhibits an unknown constant elasticity parameter and it is affected by a boundary disturbance, which is bounded in magnitude. The proposed robust synthesis is formed by the combination between line...

Controlling highly uncertain nonlinear systems is in general a quite difficult task, for which Sliding Mode (SM) control has proved to be an effective option. However, if only very conservative upper bounds on the uncertainties are known, SM control succeeds in stabilising the closed-loop system at the price of a large control authority, which may...

In this paper we investigate the properties of a decentralized consensus algorithm for a network of continuous-time integrators subject to unknown-but-bounded time-varying disturbances. The proposed consensus algorithm is based on a discontinuous local interaction rule. Under certain restrictions on the switching topology, it is proven that after a...

To realize the basic units of fractional order controllers, it is necessary to approximate irrational differintegrators. Many methods deal with analog approximation. But not many results exist for discrete approximation. In this case, approximations are most times poor in some frequency range, or the quality of the approximation is good in a narrow...

As a consequence of the massive utilization of Online Social Networks (OSNs) they must exploit a huge amount of hardware and network appliances. Therefore, optimizing their energy consumption could lead to major benefits both from the environmental and economical viewpoints. In this perspective, this paper defines a general OSN model based on homog...

In this paper an integrated circuit (IC) design of the fractional order proportional-integral-derivative (PID) controller is proposed. The development of the IC device is realized in Cadence environment, using the switched capacitors (SC) technology in order to reduce the area on the silicon wafer and to improve the electrical controllability. In o...

This paper deals with an high-order sliding-mode approach to the observer-based output feedback control of a PEM fuel cell system comprising a compressor, a supply manifold, the fuel-cell stack and the return manifold. The suggested scheme assumes the availability for measurements of readily accessible quantities such as the compressor angular velo...

This paper investigates certain complex oscillatory phenomena taking place in multivariable relay control systems. A frequency based approach is applied, by making use of such tools of frequency-domain analysis as the Locus of a Perturbed Relay System (LPRS) and transfer properties analysis via the equivalent gain concept. As the novelty, we provid...

This paper deals with the output-tracking control problem for a class of non minimum phase nonlinear systems. In order to provide the desired output tracking features while, at the same time, stabilizing the internal dynamics in finite time, a novel cascade-like control structure is devised, which mixes together first and second order sliding mode...

This chapter introduces recent developments in fault diagnostics of induction motors (IMs), by providing theoretical, simulative, and experimental results along with a number of implementation-related practical considerations and guidelines. The first section of the chapter is a short introduction in which the more common faults of IM are concisely...

This paper considers the problem of state estimation and unknown input reconstruction of a class of connected heterogeneous LTI MIMO systems. Local high order sliding mode observers at each node of the network are designed for this purpose. The proposed method, under some network structural conditions, is inherently robust, nonlinear and totally in...

This paper presents an extension of the trapezoidal integration rule, that in the present work is applied to devise a pseudo-recursive numerical algorithm for the numerical evaluation of fractional-order integrals. The main benefit of pseudo recursive implementation arises in terms of higher accuracy when the algorithm is run in the “short memory”...

This paper presents a novel algorithm for the numerical computation of fractionalorder derivatives, based on a suitable generalization of a sliding-mode based robust and exact first-order differentiator (see Levant (1998)). The method inherits the robustness properties against the measurement noise of the original scheme. The algorithm is first dev...

This chapter addresses the Lyapunov-based design of distributed and boundary second order slidingmode (2-SM) controllers in the domain of distributed parameters systems (DPSs). New distributed control results are given and, additionally, an already presented boundary control approach is briefly recalled to enhance the tutorial value of the chapter....

This paper addresses the problem of simultaneous discrete and continuous state reconstruction in the framework of linear autonomous switched systems. Main ingredient of the approach is a stack of sliding mode observers producing suitable residual signals. These residuals are used for reconstructing the discrete state and, at the same time, for iden...

In this paper we develop a decentralized discontinuous algorithm which guarantees the finite time synchronization of a network of clocks, which are modeled as continuous-time integrators and are subject to unknown-but-bounded time-varying disturbances. The proposed synchronization algorithm is asynchronous and consists in a randomly applied local i...

This paper deals with the design of nonlinear PI control techniques for regulating a class of fractional-order dynamics governed by a commensurate-order model, possibly nonlinear, perturbed by an external disturbance. The suggested control algorithm is the combination between a fractional-order PI controller and a nonlinear robust version of it, na...

This work deals with Single-Input-Single-Output (SISO) fractional order systems with a discontinuous relay control element in the feedback loop. Stable self-sustained oscillations often occur in the closed loop relay system, and this work takes advantage of Describing Function (DF) analysis and of another more accurate approach, called Locus of a P...

This paper provides a novel approach for detecting certain abnormal operating conditions in squirrel cage induction motors (SCIMs). A mathematical model of the faulty operating mode is derived with the rotor broken bars and the rotor eccentricity being the faults of interest. To detect the fault occurrence, an appropriate FDI observer, based on sec...

This paper addresses the Lyapunov-based design of second-order sliding mode controllers in the domain of Distributed Parameter Systems (DPSs). To the best of our knowledge, the recent authors’ publications Y.Orlov, A. Pisano, E. Usai [”Continuous state-feedback tracking of an uncertain heat diffusion process”, Syst. Control Lett. 59, No. 12, 754-75...

This paper addresses a problem of state and disturbance estimation for an open-channel hydraulic system. Particularly, a cascade of n canal reaches, joined by gates, is considered. The underlying Saint-Venant system of PDEs is managed by means of a collocation-based finite-dimensional approximation. The resulting nonlinear systems' dynamics are lin...

The primary concern of the present paper is the regulation of an uncertain heat process with collocated boundary sensing and Neumann-type actuation. It exhibits an unknown constant diffusivity parameter and it is affected by a smooth boundary disturbance, which is possibly unbounded in magnitude. The proposed robust synthesis is formed by a discont...

This paper addresses the design of active controllers for enhancing the stability properties of two-wheeled vehicles, which are not yet available on neither commercial nor racing vehicles. To address this problem an active steering damper is employed by means of which the yaw rate of the vehicle is regulated with a switched, second order sliding mo...

A gradient-based algorithm for the on-line continuous estimation of the commensurate order in linear fractional order processes is presented. A key aspect of the proposed methodology is the use of appropriate variable-order fractional filters, and linear Laplace operators of logarithmic type, within the estimation mechanism. A Lyapunov based analys...

This paper presents an extension of the well-known trapezoidal (bilinear) integration rule, that in the present work is applied to the numerical evaluation of fractional-order integrals. Particularly, this approximation is exploited to derive viable numerical algorithms addressing two distinct problems: i) simulation of Linear Time-Invariant (LTI)...

This note addresses the multi‐input second‐order sliding mode control design for a class of nonlinear multivariable uncertain dynamics. Among the most important peculiarities of the considered control problem, the considered sliding vector variable has a uniform vector relative degree [2,2, … ,2] with respect to the vector control variable, and onl...

This paper considers a discontinuous dynamical observers stack and presents its possible application in the framework of fault detection and isolation (FDI) problems. Non-standard forms for the discontinuous observer injection signals, based on second-order sliding-mode techniques with dynamical sliding manifolds, are employed in the present work....

An adaptive clustering procedure specifically designed for process monitoring, fault detection and isolation is presented in this paper. The key feature of the proposed procedure can be identified as its underlying capability to detect novelties in the system’s mode of operation and, thus, to identify previously unseen functioning modes of the proc...

The primary concern of the present paper is the regulation of an uncertain heat process with collocated boundary sensing and actuation. The underlying heat process is governed by an uncertain parabolic partial differential equation (PDE) with Neumann boundary conditions. It exhibits an unknown constant diffusivity parameter and it is affected by a...

This paper addresses the design of a distributed non smooth tracking controller for a class of uncertain diffusive processes with homogeneous boundary conditions of Neumann type. Uncertainty in the diffusivity parameter, along with the presence of a sufficiently smooth distributed disturbance, characterize the considered class of processes. The pap...

Linear systems controlled by a nonlinear version of the PI algorithm are under study. The modified PI controller in question is known in the literature as the Super–Twisting (STW) algorithm (see Levant (1993)), and it belongs to the family of second order sliding mode controllers. The considered closed–loop system exhibits self–sustained stable osci...

A simple procedure for tuning the parameters of the Super-Twisting (STW) second-order sliding mode control (2-SMC) algorithm, used for the feedback control of uncertain linear plants, is presented. When the plant relative degree is higher than one, it is known [10] that a self-sustained periodic oscillation takes place in the feedback system. The p...