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Integral Input to State Stable systems in cascade

TitleIntegral Input to State Stable systems in cascade
Publication TypeMiscellaneous
Year of Publication2005
AuthorsChaillet, A, Angeli, D
KeywordsRobotics
Abstract

The Integral Input to State Stability (iISS) property is studied is the context of nonlinear time-invariant systems in cascade. A sufficient condition is given, in terms of the storage function of each subsystem, to ensure that the cascade composed of an iISS system driven by a Globally Asymptotically Stable (GAS) one remains GAS. Some sufficient conditions for the preservation of the iISS property under a cascade interconnection are also presented.

Decentralized Intrusion Detection in Cooperative Multi-Agent Systems

TitleDecentralized Intrusion Detection in Cooperative Multi-Agent Systems
Publication TypeMiscellaneous
Year of Publication2007
AuthorsFagiolini, A, Pallottino, L, Dini, G
KeywordsEmbedded Control, Robotics
Abstract

We address the problem of detecting faulty behaviors of robots belonging to a multi-agent system. Our objective is to develop a scalable architecture that can be adopted to realize a completely decentralized intrusion detector monitoring the agents' behavior. We want the solution to be independent from the set of ``rules'' describing the interaction among the agents, and from their dynamics; (non-invasive) mainly based on HW/SW components that are already present on-board of each agent. We focus on systems with decentralized cooperation schemes where cooperation is obtained by sharing a set of ``rules'' by which each agent plans its next ``action'' and where some of the agents may act not according to the rules due to spontaneous failure, tampering, or malicious introduction.

Notes

Poster Presentation

Uniform stabilization for linear systems with persistency of excitation. The neutrally stable and the double integrator cases

TitleUniform stabilization for linear systems with persistency of excitation. The neutrally stable and the double integrator cases
Publication TypeMiscellaneous
Year of Publication2007
AuthorsChaillet, A, Chitour, Y, Lor, A, Sigalotti, M
KeywordsRobotics
Abstract

Consider the controlled system $dx/dt = Ax + \alpha(t)Bu$ where the pair $(A,B)$ is stabilizable and $\alpha(t)$ takes values in $[0,1]$ and is persistently exciting. In particular, when $\alpha(t)$ becomes zero the system dynamics switches to an uncontrollable system. In this paper, we address the following question: is it possible to find a linear time-invariant state-feedback, only depending on $(A,B)$ and the parameters of the persistent excitation, which globally asymptotically stabilizes the system? We give a positive answer to this question for two cases: when $A$ is neutrally stable and when the system is the double integrator.

Towards uniform linear time-invariant stabilization of systems with persistency of excitation

TitleTowards uniform linear time-invariant stabilization of systems with persistency of excitation
Publication TypeMiscellaneous
Year of Publication2007
AuthorsChaillet, A, Chitour, Y, Lor, A, Sigalotti, M
KeywordsRobotics
Abstract

Consider the controlled system $dx/dt = Ax + \alpha(t)Bu$ where the pair $(A,B)$ is stabilizableand $\alpha(t)$ takes values in $[0,1]$ and is persistently exciting. In particular, when $\alpha(t)$ becomes zero the system dynamics switches to an uncontrollable system. In this paper, we address the following question: is it possible to find a linear time-invariant state-feedback, only depending on $(A,B)$ and the parameters of the persistent excitation, which globally exponentially stabilizes the system? We give a positive answer to this question for two cases: when $A$ is neutrally stable and when the system is the double integrator.

Adaptive nonlinear control of dynamic mobile robots with parameters uncertainty

TitleAdaptive nonlinear control of dynamic mobile robots with parameters uncertainty
Publication TypeMiscellaneous
Year of Publication2005
AuthorsBicchi, A, Caiti, A, Fontanelli, D, Greco, L, Viviani, R
KeywordsEmbedded Control, Robotics
Abstract

Research of a modular stabilizing control law for uncertain, nonholonomic mobile systems with actuators limitation has been investigated. Modular design allows the definition of a stabilizing control law for the kinematic model. The presence of uncertainties in the actuators parameters or in the vehicle dynamics has been treated both adding suitable components to the Lyapunov function and using parameters adaptation laws (e.g. adaptive control and backstepping techniques). Simulations are reported for the set point stabilization of a unicycle like vehicle showing the feasibility of the proposed approach. Torque limitations for a unicycle like vehicle has been investigated using backstepping techniques for the vehicle tracking problem. Simulations are reported.

Any Time Control

TitleAny Time Control
Publication TypeMiscellaneous
Year of Publication2006
AuthorsFontanelli, D, Greco, L
KeywordsEmbedded Control, Robotics
Abstract

It is widely accepted in the control community that the Computer Controlled Systems (briefly, CCSs), have a lot of advantages based primarily on the high reconfigurability of the controller platform and the ability of making complex yet fast decisions. Such positive features make the CCS a useful platform for multitasking control, i.e. using only one single-processor platform to control several plants. Within this framework, the computer has to share its computational time to solve several critical tasks, each one with its priority. Taking into account schedulability and real time operating systems problems, it is just a step forward to realize that tasks with low priority could be interrupted any time, with unpredictable distributions, and it is just a logical intuition that not all the tasks can be at the highest priority. From a control point of view, each control task should compute a control input to the controlled system to prevent instability or to ensure the performances. This field seems to be at the border between the control community and the computer science community and it has not been widely investigated. Some work has been presented introducing more general scheduling models and methods for control systems, where control design methodology takes the availability of computing resources into account and allows the trade–offs between control performance and computer resources utilization, and also introducing the idea of any time CCS without solutions. In literature, the Control Server is introduced, allowing the separation between scheduling and control design by treating the controllers as scalable real–time components. Jitter and latency is included in the model and cannot be taken over. Furthermore, the interrupt time, the I/O operations and the overrun handling are not taken into account, simply imposing only soft real time control tasks. Useful tools for the analysis of real time control performance are the Jitterbug and the True Time that analyze the control performance once the control tasks are implemented as soft real time tasks.