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In this letter, a robust quantized sampled–data controller is provided for a class of nonlinear systems affected by time–varying uncertainties, actuation disturbances and measurement noises. Sufficient conditions based on linear matrix inequalities and ensuring the existence of the proposed robust quantized sampled–data controller are given. Quantization of both state measurements and input signals is simultaneously considered. Input–to–state stability redesign technique is used in order to attenuate the effects of bounded actuation disturbances and of bounded observation errors. It is proved that, under suitably fast sampling and accurate quantization of the input/output channels, the proposed controller achieves the semi–global practical stability, with arbitrarily small final target ball, of the related quantized sampled–data closed–loop system provided that the observation errors do not affect (or affect marginally) the robustification term added in the controller and, that the bounds of the actuation disturbances as well as of the observation errors are a priori known. The theory here developed includes also the cases of time–varying sampling intervals and of non–uniform quantization of the input/output channels as well as the stability analysis of the inter–sampling system behavior. The provided results are validated through an example of one–link manipulator.

In this letter, the notion of GALES (Global Asymptotic Local Exponential Stability) is extended to nonlinear systems described by Retarded Functional Differential Equations. Necessary and sufficient Lyapunov-Krasovskii conditions ensuring the GALES of nonlinear time-delay systems are provided. The conditions related to the lower bound and to the dissipation rate of the Lyapunov-Krasovskii functional involve only the current value of the solution, making the provided tool easy to use. An example validating the results is presented.

In this paper, a nonlinear impulsive observer for a class of Lipschitz nonlinear systems with time-varying uncertainties is investigated. The observer uses discrete time measurements of the system output. A time-varying Lyapunov function is used to show that, under sufficient conditions based on linear matrix inequalities, the estimation error is globally practically stable at the origin. The dynamic observer is tested on an example to demonstrate the effectiveness of the proposed approach.

We present a novel solution to the attitude control problem of ground vehicles by means of the Active Front Steering (AFS) system. The classical feedback linearization method is often used to track a reference yaw dynamics while guaranteeing vehicle stability and handling performance, but it is difficult to apply because it relies on the exact knowledge of the nonlinearities of the vehicle, in particular the tire model. In this work, the unknown nonlinearities are real-time learnt on the basis of the universal approximation property, widely used in the area of neural networks. With this approximation method, the Uniform Ultimate Boundedness (UUB) property with respect to tracking and estimation errors can be formally proven. Preliminary simulation results show good tracking capabilities when model and parameters are affected by uncertainties, also in presence of actuator saturation.

In this paper, the sampled–data formation control problem of multi unmanned aerial vehicles (UAVs), affected by actuation disturbances and observation errors, over strongly directed networks is studied. In particular, a robust consensus based sampled–data protocol enabling a connected and leaderless swarm of UAVs to reach a desired formation in altitude and position is proposed. The provided sampled–data control algorithm relies on the architecture of leaderless consensus, in which each UAV communicates with the adjacent UAVs only and, furthermore, on the input-to-state stability redesign methodology which is used in order to attenuate the effects of any bounded actuation disturbance and of any sufficiently small observation error. A sampled–data control strategy for the collision avoidance of adjacent UAVs is also included. The theory of the stabilization in the sample–and–hold sense is used as a tool in order to prove that the sampled–data leaderless consensus of the multi–UAVs swarm is ensured, regardless of the above disturbances and errors. Actuator disturbances are assumed to be bounded with arbitrarily large a-priori known bound. Simulations show the good performances of the proposed robust sampled–data control algorithm.

In this paper, the plasma glucose regulation problem for type 2 diabetic patients is studied. A nonlinear time-delay model of the glucose–insulin regulatory system is exploited to design a quantized sampled-data static output feedback control, using only glucose measurements. It is shown that the proposed control law achieves semiglobal practical stability of the related quantized sampled-data closed-loop glucose–insulin system with arbitrary small steady-state tracking error. The controller involves past values of the glucose, which may not be available in the buffer, for instance because of non-uniform sampling. Such a drawback is overcome by means of spline interpolation. Furthermore, quantization in both input and output channels are taken into account. A pre-clinical validation, concerning the performances of the proposed glucose regulator, is carried out by means of a well-known simulator of diabetic patients, broadly accepted for testing insulin infusion therapies. The simulation results pave the way for further clinical evaluation.

This paper deals with the sampled-data leaderless consensus tracking problem of nonlinear time-delay multi-agent systems (MASs) over strongly directed networks. In particular, a new methodology for the design of sampled-data controllers achieving the leaderless consensus tracking of nonlinear MASs affected by state-delays is proposed. Firstly, the notion of steepest descent consensus feedback (SDCF), induced by a general class of Lyapunov-Krasovskii functionals, is introduced. Then, it is proved that there exists a suitably small maximum inter-sampling time such that the digital implementation of SDCFs (continuous or not) achieves the leaderless consensus tracking in a semi-global practical sense of the related sampled-data closed-loop MAS. The stabilization in the sample-and-hold sense theory is used as a tool for proving the results. The case of time-varying sampling intervals as well as the stability analysis of the inter-sampling system behaviour is included in the theory here developed. An example is studied in order to validate the results.

In this paper, an impulsive observer–based controller is designed for a class of Lipschitz nonlinear systems with time–varying uncertainties. The impulsive observer uses only sampled measurements of the system output. Sufficient conditions for the existence of the controller are given in terms of Linear Matrix Inequalities, obtaining exponential stability to the origin of the system state and the state estimation error. The performance of the proposed impulsive observer–based controller is tested via simulations.

In this paper we design a dynamic controller for the attitude control of a ground vehicle. This controller ensures the tracking of desired references, in the presence of uncertainties in the parameters describing the tire-road friction coefficient and the lateral tire stiffness, and in the presence of external perturbations, such as lateral wind. It incorporates some dynamics reconstructing the lateral vehicle velocity, often not directly measured. Finally, the proposed control scheme allows the identification of the unknown parameters and, at the same time, of the disturbance due to the lateral wind acting on the vehicle. The performance of the dynamic controller is evaluated making use of CarSim considering a challenging double steer maneuver.

This paper deals with the feedback stabilization problem for a class of nonlinear neutral stochastic functional differential equations. The systems under consideration are nonlinear, nonaffine in control with discrete and distributed delays. They are described as Ito differential equations. We use a Razumikhin-type approach to establish sufficient conditions ensuring the stabilizability of the system and a class of stabilizing feedback is proposed.

The aim of this study is to design and implement a virtual reality bicycle system based on a functional-based mechatronic design approach. The development of virtual reality technologies with haptic systems demands a proper integration of the involved disciplines to provide immerse experiences for users. The proposed design approach provides a formal manner to gather the subsystems in the mechatronic device. The developed system is divided in a Virtual Reality System (VRS) and a Physical System (PS) for the design process. The former includes an interactive virtual environment in which an Avatar is animated using a simple kinematic bicycle model. The latter includes an adapted mountain bicycle with haptic feedback mechanisms to interact with the user and to produce the corresponding inputs for the bicycle model. Both systems are integrated by a control behavior system that works under two operation modes, where the user carries out virtual tours and gets feedbacks from a stereoscopic display system, audio cues, and haptic mechanisms. A multibody simulation validates the consistency and the integration of the physical system. In addition, a set of experimental results show the performance of instrumentation elements, control strategies, and feedback mechanisms, to provide the user with an immersive experience in the virtual environment. A brief survey was carried out to assess the opinion of users about the virtual bicycle tours, providing feedback for future improvements. The different designed modules and sub-systems allow modifying and enhancing the VRS without major modifications of the PS, or allow enhancing the physical platform without affecting the functionality of the virtual environment.

International audience; In this paper, we investigate the stabilization of a Lipschitz non linear plant under the assumption of dynamic event triggered sampling. Sufficient conditions, making use of a hybrid Lyapunov function and convex embedding, are given to guarantee the existence of a triggering mechanism, leading to asymptotic stability. Both gain analysis and gain synthesis are considered.

This paper proposes the design of a reset fuzzy observer for the class of nonlinear systems able to be described by a Takagi–Sugeno fuzzy model. The observer uses both continuous and discrete measurements and in contrast with the observers based on the First Order Reset Element (FORE), it updates its states resetting the initial condition of the integrator at each instant when the discrete measurements are available. The proposed fuzzy observer is applied to estimate the substrate and biomass concentration of an anaerobic wastewater treatment process and the effectiveness of the proposed method is tested by simulations comparing the results of a reset fuzzy observer with two fuzzy observers using continuous measurements only. Finally, the estimation scheme is validated using experimental data from an actual anaerobic digestion process, suggesting that the proposed reset fuzzy observer is a practical and encouraging approach to the state estimation of the class nonlinear processes under study.

In this paper, we develop novel results on self-triggered control of nonlinear systems, subject to perturbations, and sensing/computation/actuation delays. First, considering an unperturbed nonlinear system with bounded delays, we provide conditions that guarantee the existence of a self-triggered control strategy stabilizing the closed-loop system. Then, considering parameter uncertainties, disturbances and bounded delays, we provide conditions guaranteeing the existence of a self-triggered strategy that keeps the state arbitrarily close to the equilibrium point. In both cases, we provide a methodology for the computation of the next execution time. We show on an example the relevant benefits obtained with this approach in terms of energy consumption with respect to control algorithms based on a constant sampling with a sensible reduction of the average sampling time.

The oral bioavailability of the antiretroviral efavirenz (EFV) undergoes high inter and intra-individual variability, this fact supporting its therapeutic drug monitoring. Previously, it was demonstrated that the encapsulation of EFV within polymeric micelles increases the oral bioavailability of the drug. The breast cancer resistant protein (BCRP, ABCG2) is known to be inhibited by EFV in vitro. Since ABCG2 is profusely expressed in the gastrointestinal tract, the aim of the present work was to thoroughly investigate whether the intestinal permeability of EFV is modulated by ABCG2. The functional role of ABCG2 in mediating the transport of EFV at the intestinal level was consistent with the following findings: (a) an ABCG2 inhibitor, fumitremorgin C (5-10μM), significantly potentiated the mucosal-to-serosal permeation of the drug in everted gut sacs; (b) a five-day oral treatment with 20mg/kg EFV promotes the over-expression of ABCG2 in about 100%, this phenomenon being accompanied by a clear decline in the intestinal permeability of the antiretroviral and (c) the normalization of the ABCG2 expression within 24h after the last administration of EFV was coincident with the recovery of the ability of the drug to permeate through the small intestine wall. Interestingly, no interactions between EFV and P-glycoprotein (ABCB1) were apparent. Since the intestinal permeability of a drug could be associated with its in vivo absorbability, we suggest that the oral absorption of EFV is affected by modifications in the ABCG2 intestinal expression contributing to the intra-individual bioavailability variations.

In this paper the problem of stabilization of continuous systems with time delay in input which are discretized is addressed. Using a predictor based controller capable of stabilizing and compensating the discrete model and continuous model as well, is obtained. This scheme allows using a digital controller for stabilizing an analog plant. The performance of such a control scheme is tested in the case of simplified attitude control of a vehicle.

In this paper we propose a solution to the model-based fault diagnosis problem for the class of non-linear dynamic systems subjected to be described by a Takagi-Sugeno fuzzy model. A fuzzy observer is designed to estimate the system's state vector and to derive a diagnostic signal-residual. The residual is generated by the comparison of the measured and the estimated outputs. The proposed scheme has been satisfactorily tested in simulation and in a real-time benchmark given by a Two-Tank Hydraulic System. Work supported by the Consejo Nacional de Ciencia y Tecnologia (Conacyt, Mexico), by the Secretaria de Relaciones Exteriores (S.R.E.Mexico), by the Consiglio Nazionale delle Ricerche (C.N.R., Italy), and by the Ministero degli Affari Esteri (M.A.E., Italy).

This work deals with a sliding mode control scheme for discrete time nonlinear systems. The control law synthesis problem is subdivided into a finite number of subproblems of lower complexity, which can be solved independently. The sliding mode controller is designed to force the system to track a desired reference and to eliminate unwanted disturbances, compensating at the same time matched and unmatched parameter variations. Then, an observer is designed to eliminate the need of the state in the controller implementation. This design technique is illustrated determining a dynamic discrete time controller for induction motors.

In this paper, a controller for induction motors is proposed. A continuous feedback is first applied to obtain a discrete-time model in closed form. Then, on the basis of these exact sampled dynamics, a discrete-time controller ensuring speed and flux modulus reference tracking is determined, making use of the sliding mode technique. The resulting controller is hence hybrid, in the sense that it contains both continuous and discrete-time terms. It is shown how to implement such a hybrid controller using the so-called exponential holder, which is the only device to be implemented analogically, together with an analog integrator. Moreover, a discrete-time reduced-order observer is designed for rotor fluxes and load torque estimation. The performance of the proposed controller is finally studied by simulation and experimental tests.

Given a wireless network and a graph modelling the node connection topology, we address the problem of fault diagnosis of nodes. When the external point of access to network information is at a lower layer of the ISO/OSI protocol stack, the problem is trivial. However, as often occurs, a user is able to access the network at the application layer : this implies that the available observation of the network status is considerably restricted, and solving the diagnosis problem is not trivial. In this paper, we state necessary and sufficient conditions for being able to detect which node is faulty, and propose a diagnosis algorithm on the basis of diagnosability definitions and theoretical studies developed for timed and hybrid automata in the computer science community.

Conventional internal combustion engines use mechanical camshafts to command the opening and closing phases of the intake and exhaust valves. The lift valve profile is designed in order to reach a good compromise among various requirements of the engine operating conditions. In principle, optimality in every engine condition can be attained by camless valvetrains. In this context, electromagnetic valves appear to be promising, although there are some relevant open problems. In fact, in order to eliminate acoustic noises and avoid damage to the mechanical components, the control specifications require sufficiently low impact velocities between the valve and the constraints (typically the valve seat), so that “soft-landing” is obtained. In this paper, the soft–landing problem is translated into a regulation problem for the lift valve profile, by imposing that the valve position tracks a desired reference, while the modelled disturbances are rejected. Both reference and disturbance are generated by an autono...

Aim: To assess the involvement of ABCG2 in the pharmacokinetics of efavirenz in the blood–brain barrier (BBB) and investigate a nanotechnology strategy to overcome its overexpression under a model of chronic oral administration. Materials & methods A model of chronic efavirenz (EFV) administration was established in male Sprague–Dawley rats treated with a daily oral dose over 5 days. Then, different treatments were conducted and drug concentrations in plasma and brain measured. Results: Chronic treatment with oral EFV led to the overexpression of ABCG2 in the BBB that was reverted after a brief washout period. Moreover, gefitinib and the polymeric amphiphile Tetronic® 904 significantly inhibited the activity of the pump and potentiated the accumulation of EFV in CNS. The same effect was observed when the drug was administered within mixed micelles containing TetronicT904 as the main component. Conclusion: Tetronic 904-containing polymeric micelles overcame the overexpression of ABCG2 in the BBB caused by chronic administration of EFV then boosting its penetration into the CNS. Fil: Roma, Martín Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires; Argentina Fil: Hocht, Christian. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina Fil: Chiappetta, Diego Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Di Gennaro, Stefania S.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina Fil: Minoia, Juan Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina Fil: Bramuglia, Guillermo F.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina Fil: Rubio, Modesto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina Fil: Sosnik, Alejandro Dario. Technion - Israel Institute Of Technology; Israel Fil: Peroni, Roxana Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina

In this paper the stabilization problem for a class of neutral stochastic systems with delay is investigated. The state equations are described by an Ito differential equation driven by a Wiener noise. The input generically enters both in the deterministic dynamics and in those affected by noise. The considered systems are nonlinear and nonaffine in the control. By using the Razumikhin-type approach, general conditions are developed for stabilizing the closed-loop system. A stabilizing state feedback control is also derived.

International audience; In this paper, we investigate the stabilization of a linear plant subject to network constraints, partial state knowledge and time varying bounded parameter uncertainties. An event–triggered version of the Luenberger observer is proposed, and necessary conditions on the uncertainties are given in term of LMI's to enable output– based stabilization under different triggering strategies. The proposed observer is tested in simulations on a linearized inverted pendulum. I. INTRODUCTION In modern control system it is more and more common to use digital technology, where the control task consists of sampling the outputs of the plant then computing and implementing new actuator signals. The classic way to proceed is to sample in a periodic fashion the output, thus allowing the closed–loop system to be analyzed on the basis of sampled–data systems [1]. In network control system such as vehicle platooning and smart grid, communication between different agent on the network play a big role in the overall stability. Therefore, it can be of use to reduce the communication when sampling is not needed. Recent years have seen the development of a new paradigm where, instead of sampling periodically, i.e. with a time triggered policy, the system is triggered when needed, i.e. using an event triggered policy. A lot of works have been done on this subject, see [2], [18], [19], [16], [6] and references therein, while for an introduction to the topic see [7]. Our main focus in this work is to investigate the impact of the event triggered paradigm on observer– based (i.e. dynamical feedback) control systems. More precisely, the observer–based control problem is considered for linear systems in the presence of model uncertainties. Different kinds of event triggered policies allow practical or asymptotic stability. Furthermore, the result proposed are global in the sense that the stability does not depend on initial condition and initial observation error. As particular case, the proposed results can be obviously applied for full state feedback. Some studies are available on observer–based controller [3], [4], [12], [17]. In [3] and [4] practical stability is ensured in presence of a disturbance on the plant, while a L ∞ gain is guaranteed. In [12], the plant and the output are subject to perturbation and practical stability is also guaranteed. In [17], asymptotic stability is obtained in absence of perturbations. In [5], an uncertain plant is used to stabilize a system between two communications, in the case of availability of the full state. To the best of the authors' knowledge, no result are available when the system under consideration are not linear. With respect to these previous results, this paper considers the robustness issues of the event triggered observation and control with respect to time varying modeling uncertainties, allowing to state that if the continuous closed loop system is robust, then the uncertain system is stabilizable with the event triggered policy. Moreover, asymptotic stabilization of an uncertain system using an adapted event triggered policy is obtained.

In this paper, we investigate the stabilization of a nonlinear plant subject to network constraints, under the assumption of partial knowledge of the plant state. The event triggered paradigm is used for the observation and the control of the system. Necessary conditions, making use of the ISS property, are given to guarantee the existence of a triggering mechanism, leading to asymptotic convergence of the observer and system states. The proposed triggering mechanism is illustrated in the stabilization of a robot with a flexible link robot., Proceedings of the 2015 American Control Conference - ACC 2015

Event-Triggered control is a resource-aware sampling strategy that updates the control value when a certain condition is satisfied, which denotes event instants. Such technique allows to reduce the control computational cost and communications. In this paper an Event-Triggered linear control for an Antilock Braking System is developed and simulated using the mathematical model of the ABS laboratory setup, manufactured by INTECO. The proposed feedback ensures the asymptotically stability of the ABS.

Addressed here is the problem of designing a dynamic controller capable of performing rest-to-rest maneuvers for flexible spacecraft, by using attitude measures. This controller does not need the knowledge of modal variables and spacecraft angular velocity. The absence of measurements of these variables is compensated by appropriate dynamics of the controller, which supplies their estimates. The Lyapunov technique is applied in the design of this dynamic controller. Possible source of instability of the controlled system in real cases are the influence of the flexibility on the rigid motion, the presence of disturbances acting on the structure, and parameter variations. In order to attenuate their effects and to damp out undesirable vibrations affecting the spacecraft attitude, distributed piezoelectric actuators are used. In fact, in presence of disturbances and/or parameter variation the proposed controller ensures an approximate solution of the control problem.

In this work, we propose a dynamic controller for a spacecraft with flexible appendages and based on attitude measurements. This control ensures the asymptotic fulfillment of the objectives in the case of rest-to-rest maneuvers when a failure occurs on the accelerometer sensors, so that the angular velocity is not available for feedback. Also, it is assumed that the modal variables describing the flexible elements are not measured. This is a lower level controller and is to be selected at the higher level by a supervisor when an emergency situation is detected.

In this work a class of nonlinear controllers has been derived for spacecraft with flexible appendages. The control aim is to track a given desired attitude. First, a static controller based on the measure of the whole state is determined. Then, a dynamic controller is designed; this controller does not use measures from the modal variables, and the variables measured are the parameters describing the attitude and the spacecraft angular velocity. Finally, it is shown that a relaxed version of the tracking problem can be solved when the only measured variable is the spacecraft angular velocity. Simulations show the performances of such control schemes.

This work deals with the nonlinear H∞ control of a permanent magnet synchronous motor subject to parameter variations during its operation. The control aim is to track a desired angular trajectory. The controller design is achieved in two steps: first, a controller based on the nominal parameter values is determined, while the parameter variations and the deterioration of the ideal control law, due to the use of a real actuator, are considered disturbances acting on the nominal plant. Second, a nonlinear H∞ controller is designed in order to satisfy the sub-optimal attenuation problem in the case of availability of the whole state vector. This second phase entails the approximated resolution of a (nonlinear) Hamilton-Jacobi-Isaacs equation. The resulting controller is tested in numerical simulations and its performances are compared with those of an LQR controller.

When a failure occurs in a nuclear plant, a lack in the response of the controller could lead to serious consequences. The fundamental property to be ensured by the controller is the plant stability, possibly proved formally, and at least in the range of validity of the process model. In this work, using a mathematical model for the primary circuit of a PWR, accurate enough to catch the nonlinear, time–varying, and switching nature of the system, and suitable for the control purposes, the reactor power controller, the inventory controller for the primary circuit, and the pressurizer pressure controllers are designed. These controllers do not use direct measurements of the pressurizer pressure or temperature, but they use instead pressurizer wall temperature measurements. Disturbances and parameter variations are compensated by the use of sliding–mode terms, which guarantee further robustness to the control scheme. The switching nature of the controller, reflecting the switching nature of the pressurizer dynamics, and the nonlinear terms implemented in the controllers, along with classical PI actions, ensure better transient behaviors. Hence, they represent an evolution and an improvement with respect to classical PID controllers, usually implemented in standard control actions.Copyright © 2014 by ASME

WOS:000354963600071; International audience; It is here shown that investigating the controllability of a positive chaotic system is not appropriate to determine influences of parametric variations on its solutions. A stabilizability analysis is then performed using a Lyapunov approach by taking into account the fact that the solution must remain in a given positive domain. Some numerical results highlight the advantage of the proposed analysis.

Switched systems constitute a subclass of hybrid systems, which are systems where both continuous and discrete event dynamics are tangled together. In this work, we consider two classes of observable switched systems. For each class, an observer is designed. First, some results available for linear switched systems are extended to the nonlinear case, assuming that each system is linearizable by output injection. Then, for the class of switched systems which can be put in triangular form by a diffeomorphism, an observer is designed. The proposed observers are tested on an illustrative example.

Robust feedback control of a synchronous motor with model and parameter uncertainties and load disturbances is studied. The mathematical description of the motor in the (d, q) frame yields a bilinear model in state space form. The control strategy is based on a worst-case analysis and leads to the formulation of a min–max problem, whose solution provides an H∞ bound for the noise-to-output transfer function. The design of the dynamic controller entails the solution of an appropriate Riccati equation.

We consider a class of hybrid dynamical systems and obtain conditions under which the behavior of these systems can be reduced to a finite state automaton. Specifically, we consider timed automata with more general enabling regions coupling the continuous and discrete dynamics than those previously considered. We provide a necessary condition for the existence of a finite state reduction, together with examples showing that this condition is not sufficient. We then give two sufficient conditions that provide a large class of systems with general enabling regions which admit finite reductions.

The paper deals with linear and nonlinear regulation under sampling. It is shown that digital solutions exist under assumptions which are closely related to the existence of robust solutions to the continuous problem. Approximated solutions are computed starting from the continuous ones.

Studying criteria ensuring better implementations of control laws and logics on digital programmable devices is today a crucial point in order to improve performance and safety in nuclear plants of novel design. To this aim, a mathematical model of a PWR is considered, describing the dynamics of the primary circuit. This model is simple enough to allow the determination of a control policy, but it is also sufficiently accurate to capture the nonlinear, time–varying, and switching nature of the system. A dynamic controller for the pressurizer pressure and water level is hence designed. Its main advantage is the reduction of the control response. This latter is a classical drawback, which may cause some troubles to pressure control, due to the long response of temperature sensors. The digital implementation of the controller has been taken into account to study the important aspects of the influence of the implementation on the performance of the control law. A particularly effective and flexible environment where it is possible to analyze these aspects is Matlab/Simulink, a general–purpose tool for analysis and simulation of multi–domain dynamic systems, practically a standard in control implementations, also in industrial applications. The designed controller ensures a good performance when applied to the model used to derive them, also in the presence of unmodeled uncertainties and disturbances. Its nonlinear switching nature, reflecting the real pressurizer dynamics, ensures better transient behaviors. Since it contains a PI action, it represents an evolution and an improvement with respect to classical PID controllers, usually implemented in standard control actions. To better analyze the control performance, three steps have been considered: first, the designed nonlinear controller has been compared with a linear one. Second, it has been tested on a more detailed model, with more realistic dynamics. Finally, the digital implementation of the controller has been simulated, in order to optimize the electronic implementation on the FPGA–CPU hybrid platform. A simulation study has been conducted with sampling times in ascending order, to further test its robustness against delays. LabVIEW development tool and technology has been chosen to create the electronic layout and to obtain preliminary results in terms of timing, resources availability and power consumption. Due to the same graphical mode of programming, an immediate link between Matlab/Scilab and LabVIEW is possible in order to optimize the use of each language where it guarantees the best performance. The methodology here presented could be very useful to better integrate the different features of control engineering and IC design, thus giving the possibility of realizing more accurate simulations and permitting to perform a hardware in the loop (HIL) testing of a wide variety of control algorithms.

International audience; This paper presents the design of a self-triggered methodology for control of multi-agent systems. Conditions that guarantee the existence of a self-triggered strategy solving the consensus problem, are provided for first order systems under fixed and switching topologies. A methodology for the computation of the feedback gain and the control update time is given. Simulation results show the effectiveness of the proposed strategy

This paper addresses the problem of vehicle attitude control in the presence of saturating actuators. A novel approach of actuation balancing is proven to be the best way to keep the vehicle off saturation or, at least, to postpone the saturation occurrences as late as possible. In hard conditions, this may be not sufficient to guarantee tracking; hence the joint design of a load-balancing control law and an adapted reference generator is addressed, in order to cope with the lack in the control action and prevent unstable behaviors. On top of the formal results, the method is validated by means of simulations.

In this paper we address the problem of stabilizing a sampled continuous system with time-delay in the input, by means of a digital predictor-based controller. The predictor is capable of compensating the delay of the sampled and continuous model as well. This scheme allows using a digital controller for stabilizing the continuous system. The performance of this control scheme is tested in an illustrative example.

This technical note addresses the problem of observability of continuous-time Switched Linear Systems (SLS) subject to unknown disturbances, unknown switching signals and unconstrained nonzero dwell time. For this class of hybrid systems, a geometric characterization of the observability properties is presented. In particular, attention is focused on the estimation of the SLS state from the continuous measurements. Using the well known concept of (A, B)-invariant subspaces, three main problems are addressed and solved, namely the observability for every nonzero state trajectory, the observability for almost every control input, and the observability for almost every state trajectory. It is also shown that the approach herein presented subsumes some of the classical results on observability of SLS previously reported in the literature, and allows expressing them in a common framework.

In this paper we develop novel results on self triggering control of nonlinear systems, subject to perturbations and actuation delays. First, considering an unperturbed nonlinear system with bounded actuation delays, we provide conditions that guarantee the existence of a self triggering control strategy stabilizing the closed--loop system. Then, considering parameter uncertainties, disturbances, and bounded actuation delays, we provide conditions guaranteeing the existence of a self triggering strategy, that keeps the state arbitrarily close to the equilibrium point. In both cases, we provide a methodology for the computation of the next execution time. We show on an example the relevant benefits obtained with this approach, in terms of energy consumption, with respect to control algorithms based on a constant sampling, with a sensible reduction of the average sampling time., Comment: Proceedings of the 50th IEEE CDC-ECC, Orlando, Florida, USA, 2011

A notion of diagnosability for hybrid systems is defined, which generalizes the common notion of observability. We propose an abstraction procedure to translate a hybrid automaton into a timed automaton, in order to verify observability and diagnosability properties. We introduce a procedure to check diagnosability, and show that for the system class of our abstraction (namely for a subclass of timed automata: the durational graphs) the verification problem belongs to the complexity class P. We apply our procedure to an electromagnetic valve system for camless engines.

In this work an integrated attitude control of a vehicle is designed. The actuators considered are the active front steering, the rear torque vectoring, and the semi–active suspensions. We design also an algorithm for the saturation management. The resulting controller is hybrid. In nominal conditions, when saturation conditions do not occur, a feedback guarantees exponential tracking of the reference trajectories. In critical conditions, a hybrid feedback law assigns higher priority to some states to improve the tracking. It is shown that the saturation management improves the controller performance. Some simulations results are provided, showing the performance of the proposed controller.

The paper deals with torque control of induction motors. A nonlinear control design solving an instantaneous high power demand is proposed while maintaining the stability of the filter which is located between the converter and the power supply line. A continuous time solution is proposed as the nominal solution of a more accurate digital design. Simulation results are discussed.

Integrated control design to guarantee vehicle stability is one of the main topics in vehicle control. Actuators saturation is a main concern when dealing with this issue. In this work, we propose a fully integrated control by means of three actuators: Active Front Steering (AFS), Rear Torque Vectoring (RTV) and Semi-Active Suspensions (SAS). A feedback controller is used to ensure, in absence of input saturation, the exponential tracking of the reference trajectories. On top of that, a smart saturation management scheme detects when the actuators approach the occurrence of saturation, and determines a policy to avoid actuator saturations. The performance of the resulting control strategy, that is hybrid in general, is tested in simulation and compared with some classical solutions.

This paper proposes a new approach for compensating input delays in nonlinear systems under sampling. The proposed dynamic controller is based on an approximated predictor of the state of the system, obtained from an approximated representation of the sampled system dynamics, and ensures practical stabilization of the exact sampled system. The approximated representation can be obtained using well-known techniques (Euler, Runge-Kutta, Takagi-Sugeno, etc.), and the controller exists provided that the exact and approximated sampled dynamics verify conditions expressing their closeness.

In this paper the sliding mode technique is used to design a discrete-time control scheme for torque and flux tracking for induction motors. The controller is designed on the basis of an approximated nonlinear discrete-time model. First, the reference current vector is determined to impose the control objectives. Then, we propose a discrete-time sliding mode controller to force the motor currents to converge to the reference values. The rotor flux and the load torque are estimated by using a reduced order observer. The effectiveness of the designed control scheme is confirmed via simulations.