Papers by Giacomo Innocenti
IEEE Access
Oscillatory circuits with real memristors have attracted a lot of interest in recent years. The v... more Oscillatory circuits with real memristors have attracted a lot of interest in recent years. The vast majority of circuits involve volatile memristors, while less explored is the use of non-volatile ones. This paper considers a circuit composed by the interconnection of a two-terminal (one port) element, based on the linear part of Chua's circuit, and a non-volatile memristor obeying the Stanford model. A peculiar feature of such a memristor is that its state displays negligible time-variations under some voltage threshold. Exploiting this feature, the memristor is modeled below threshold as a programmable nonlinear resistor whose resistance depends on the gap distance. Then, the first-order Harmonic Balance (HB) method is employed to derive a procedure to select the parameters of the two-terminal element in order to generate programmable subthreshold oscillatory behaviors, within a given range of the gap, via a supercritical Hopf bifurcation. Finally, the dynamic behaviors of the designed circuits as well as the sensitivity of the procedure with respect to the location of the bifurcating equilibrium point and the range of the gap are discussed and illustrated via some application examples.
arXiv (Cornell University), Mar 3, 2011
In many applications, it is important to derive information about the topology and the internal c... more In many applications, it is important to derive information about the topology and the internal connections of dynamical systems interacting together. Examples can be found in fields as diverse as Economics, Neuroscience and Biochemistry. The paper deals with the problem of deriving a descriptive model of a network, collecting the node outputs as time series with no use of a priori insight on the topology, and unveiling an unknown structure as the estimate of a "sparse Wiener filter". A geometric interpretation of the problem in a pre-Hilbert space for wide-sense stochastic processes is provided. We cast the problem as the optimization of a cost function where a set of parameters are used to operate a trade-off between accuracy and complexity in the final model. The problem of reducing the complexity is addressed by fixing a certain degree of sparsity and finding the solution that "better" satisfies the constraints according to the criterion of approximation. Applications starting from real data and numerical simulations are provided.
IFAC Proceedings Volumes, 2008
the paper deals with the problem of finding models and making predictions within a large set of t... more the paper deals with the problem of finding models and making predictions within a large set of time series or random processes. Nothing is assumed about their mutual influence and dependence. The problem can not be tackled efficiently, starting from a classical system identification approach. Indeed, the general optimal solution would provide a large number of models, since it would consider every possible interdependence. Then a suboptimal approach will be developed. The proposed technique will present interesting modeling properties which can interpreted in terms of graph theory. The application of this procedure will also be exploited as a tool to provide a clusterization of time series. Finally, we will show that it turns out to be a dynamical generalization of other techniques described in literature.
The recent advent of “smart” technologies in the industry has increased the interest on technique... more The recent advent of “smart” technologies in the industry has increased the interest on techniques able to lighten the burden on communication networks. In this framework, the debate on event triggered controllers has been heated by many recent and promising developments from a number of different approaches. In this paper we investigate the potential of an original input-output event triggering strategy via an ideal implementation. Special attention is put on the worst case scenario, where systems in the control loop are not stable in free running configuration. A detailed numerical example featuring a Proportional-Integral controller is then used to test the obtained performance against a common technique.
In this paper, the latency problem of computer vision systems is addressed in the framework of au... more In this paper, the latency problem of computer vision systems is addressed in the framework of autonomous Unmanned Aerial Vehicles. Recent advancements in sensors and embedded electronic boards made it possible to load, even on small size drones, cameras and image processing devices. Here, a navigation system based on computer vision is considered as one of the most popular applications exploiting this technology in substitution of Global Navigation Satellite System solutions. The main issues when working with a video stream are the limited frame rate (i.e., small sampling frequency), and the non negligible computational time for extracting features from the images (i.e., latency). In particular, the latency negatively affects a position controller that exploits data from the computer vision system, preventing its usage for precise positioning applications. In this paper, a possible solution is designed according to this recipe: First, a sensor fusion technique able to compensate the latency is adopted to estimate the velocity using the position of the computer vision system and the accelerations provided by a Inertial Measurement Unit. Then, a controller is developed using two feedback loops, the inner one accounting for the estimated velocity, and the outer one exploiting the delayed position. Test experiments, showing very positive results, are finally reported.
International Conference on Autonomic and Autonomous Systems, Jun 2, 2019
This work explores a way to achieve high precision in the positioning of a 250-class aerial drone... more This work explores a way to achieve high precision in the positioning of a 250-class aerial drone by means of only onboard sensors. The proposed technology is still in development, and its basic idea is to compensate the errors of the sensors by fusing together strongly correlated data streams. The main players are a 6 Degrees of Freedom (DoF) Inertial Measurement Unit (IMU) and a computer vision system, arranged to work together as a "virtual sensor" providing the pose of the drone relative to one or more markers acting as reference points of known position and orientation. The proposed advance sensing exploits complementary filters to merge inertial and visual data. Such a refined positioning is then used to feed a custom control strategy acting as auto-pilot for implementing autonomous navigation. Preliminary results on the developed technologies are reported.
arXiv (Cornell University), Nov 8, 2018
In this paper a novel platoon model is presented. Nonlinear aerodynamic effects, such as the wake... more In this paper a novel platoon model is presented. Nonlinear aerodynamic effects, such as the wake generated by the preceding vehicle, are considered, and their influence in the set up of a Adaptive Cruise Controller (ACC) is investigated. To this aim, bifurcation analysis tools are exploited in combination with an embedding technique independent from the vehicles number. The results highlight the importance of a proper configuration for the ACC in order to guarantee the platoon convergence to the desired motion.
arXiv (Cornell University), May 18, 2008
The paper tackles the problem of deriving a topological structure among stock prices from high fr... more The paper tackles the problem of deriving a topological structure among stock prices from high frequency historical values. Similar studies using low frequency data have already provided valuable insights. However, in those cases data need to be collected for a longer period and then they have to be detrended. An effective technique based on averaging a metric function on short subperiods of the observation horizon is suggested. Since a standard correlation-based metric is not capable of catching dependencies at different time instants, it is not expected to perform the best when dealing with high frequency data. Hence, the choice of a more suitable metric is discussed. In particular, a coherence-based metric is proposed, for it is able to detect any possible linear relation between two times series, even at different time instants. The averaging technique is employed to analyze a set of 100 high volume stocks of the New York Stock Exchange, observed during March 2008.
RePEc: Research Papers in Economics, Jul 1, 2008
IFAC Proceedings Volumes, 2008
The aim of the paper is to present ARTIST, the remote control laboratory at University of Florenc... more The aim of the paper is to present ARTIST, the remote control laboratory at University of Florence. Students can remotely interact with a number of physical processes exploiting predefined controllers or uploading their own. The main features of the lab are: a modular approach for the realization of different control tasks for the same process, which can be executed on different lab PCs and communicate over a network; a web-service application which exploits a database to facilitate the registration of users, processes and experiments of the laboratory. ARTIST website can be found at http://artist.dsi.unifi.it.
Computer Applications in Engineering Education, Jun 2, 2015
ABSTRACT
2018 AIAA Guidance, Navigation, and Control Conference
ESSCIRC 2022- IEEE 48th European Solid State Circuits Conference (ESSCIRC)
Journal of the Franklin Institute
2019 18th European Control Conference (ECC), 2019
This paper deals with control of multistability in memristor circuits, an issue of growing intere... more This paper deals with control of multistability in memristor circuits, an issue of growing interest also for its connection with the development of new computational paradigms, such as reservoir computing. Under the assumption that the memristor is ideal, the invariant manifolds of the Murali-Lakshmanan-Chua circuit are first explicitly computed and their own attractors are investigated. Feed-forward and feedback control laws are then devised for targeting dynamics on the manifolds. Specifically, the controllers are able to make the circuit state converging in finite time on an assigned invariant manifold and to switch over time among different manifolds. It is also pointed out that the intrinsic robustness of feedback control laws can positively counteract the possible lack of ideality of memristors, due, e.g., to imperfections in their practical realization.
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2019
A stochastic reaction-diffusion model is studied on a networked support. In each patch of the net... more A stochastic reaction-diffusion model is studied on a networked support. In each patch of the network, two species are assumed to interact following a non-normal reaction scheme. When the interaction unit is replicated on a directed linear lattice, noise gets amplified via a self-consistent process, which we trace back to the degenerate spectrum of the embedding support. The same phenomenon holds when the system is bound to explore a quasidegenerate network. In this case, the eigenvalues of the Laplacian operator, which governs species diffusion, accumulate over a limited portion of the complex plane. The larger the network, the more pronounced the amplification. Beyond a critical network size, a system deemed deterministically stable, hence resilient, can develop seemingly regular patterns in the concentration amount. Non-normality and quasidegenerate networks may, therefore, amplify the inherent stochasticity and so contribute to altering the perception of resilience, as quantifie...
The article revisits Aizerman and Kalman conjectures for absolute stability through the lens of a... more The article revisits Aizerman and Kalman conjectures for absolute stability through the lens of a novel graphical interpretation. Even though these conjectures are false in the general case, such a graphical interpretation suggests natural ways to introduce additional conditions in order to obtain valid absolute stability criteria. As an illustration, the article proves a new absolute stability criterion obtained by the iterative application of a variation of the circle criterion.
IEEE Journal on Emerging and Selected Topics in Circuits and Systems
A well-known feature of memristors is that they makes the circuit dynamics much richer than that ... more A well-known feature of memristors is that they makes the circuit dynamics much richer than that generated by classical RLC circuits containing nonlinear resistors. In the case of circuits with ideal memristors, such a multistability property, i.e., the coexistence of many different attractors for a fixed set of parameters, is connected to the fact that the state space is composed of a continuum of invariant manifolds where either convergent or oscillatory and more complex behaviors can be displayed. In this paper we investigate the possibility of designing memristor circuits where known attractors are embedded into the invariant manifolds. We consider a class of forced nonlinear systems containing several systems which are known to display complex dynamics, and we investigate under which conditions the dynamics of any given system of the class can be reproduced by a circuit composed of a two-terminal (one port) element connected to a flux-controlled memristor. It is shown that an input-less circuit is capable to replicate the system attractors generated by varying the constant forcing input, once the parameters of the two-terminal element and the memristor nonlinear characteristic are suitably selected. Indeed, there is a one-one correspondence between the dynamics generated by the nonlinear system for a constant value of the input and that displayed on one of the invariant manifolds of the input-less memristor circuit. Some extensions concerning the case of non-constant forcing terms and the use of charge-controlled memristors are also provided. The results are illustrated via FitzHugh-Nagumo model and Duffing oscillator.
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Papers by Giacomo Innocenti