poster presentation

ER - TY - CONF T1 - Resource aware control T2 - Automatica.it 2011 Y1 - 2011 A1 - L. Greco A1 - D. Fontanelli A1 - L. Palopoli KW - Robotics JF - Automatica.it 2011 CY - Pisa, Italy ER - TY - JOUR T1 - Design of Embedded Controllers Based on Anytime Computing JF - IEEE Trans. Industrial Infor. Y1 - 2010 A1 - A. Quagli A1 - D. Fontanelli A1 - L. Greco A1 - L. Palopoli A1 - A. Bicchi KW - Embedded Control KW - Robotics AB -In this paper, we present a methodology for designing embedded controllers based on the so-called anytime control paradigm. A control law is split into a sequence of subroutine calls, each one fulfilling a control goal and refining the result produced by the previous one. We propose a design methodology to define a feedback controller structured in accordance with this paradigm and show how a switching policy of selecting the controller subroutines can be designed that provides stability guarantees for the closed-loop system. The cornerstone of this construction is a stochastic model describing the probability of executing, in each activation of the controller, the different subroutines. We show how this model can be constructed for realistic real-time task sets and provide an experimental validation of the approach.

VL - 6 ER - TY - JOUR T1 - Sensor Deployment for Network-like Environments JF - IEEE Trans. on Automat. Contr. Y1 - 2010 A1 - L. Greco A1 - M. Gaeta A1 - B. Piccoli KW - Robotics N1 -Condit. accepted as Technical Note

ER - TY - ABST T1 - Sensor Deployment for Network-like Environments Y1 - 2010 A1 - L. Greco A1 - M. Gaeta A1 - B. Piccoli KW - Robotics N1 -Full version

ER - TY - CONF T1 - Designing Real-Time Embedded Controllers using the Anytime Computing Paradigm T2 - IEEE International Conference on Emerging Technology and Factory Automation Y1 - 2009 A1 - A. Quagli A1 - D. Fontanelli A1 - L. Greco A1 - L. Palopoli A1 - A. Bicchi KW - Embedded Control KW - Robotics AB -In this paper we present a methodology for designing embedded controllers with a variable accuracy. The adopted paradigm is the so called any-time control, which derives from the computing paradigm known as "imprecise computation". The most relevant contributions of the paper are a procedure for designing an incremental control law, whose different pieces cater for increasingly aggressive control requirements, and a modelling technique for the execution platform that allows us to design provably correct switching policies for the controllers. The methodology is validated by both simulations and experimental results.

JF - IEEE International Conference on Emerging Technology and Factory Automation CY - Palma de Mallorca, Spain ER - TY - CONF T1 - Anytime Control Algorithms for Real-Time Embedded Systems T2 - Int Conf of Hybrid Systems: Computation and Control Y1 - 2008 A1 - D. Fontanelli A1 - L. Greco A1 - A. Bicchi ED - M. Egerstedt ED - B. Mishra KW - Embedded Control KW - Robotics AB -In this paper we consider the problem of designing controllers for linear plants to be implemented in embedded platforms under stringent real-time constraints. These include preemptive scheduling schemes, under which the maximum execution time allowed for control software tasks is uncertain. We propose an ``anytime control'' design approach, consisting in a hierarchy of controllers for the same plant. Higher controllers in the hierarchy provide better closed-loop performance, while typically requiring a larger worst-case execution time. We provide a procedure for the design of controllers which, together with a conditioning process of the stochastic scheduling, provides better performance than prevailing worst case-based design, while guaranteeing almost sure stability of the resulting switching system.

JF - Int Conf of Hybrid Systems: Computation and Control T3 - Lecture Notes in Computer Science PB - Springer-Verlag CY - St. Louis, MO VL - 4981/2008 ER - TY - CONF T1 - Deployment of sensors in a network-like environment T2 - Proc. 47th IEEE Conference on Decision and Control Y1 - 2008 A1 - L. Greco A1 - M. Gaeta A1 - B. Piccoli KW - Robotics JF - Proc. 47th IEEE Conference on Decision and Control CY - Cancun, Mexico ER - TY - CONF T1 - Optimal Paths in a Constrained Image Plane for Purely Image-Based Parking T2 - IROS Y1 - 2008 A1 - P Salaris A1 - F. A. W. Belo A1 - D. Fontanelli A1 - L. Greco A1 - A. Bicchi KW - Robotics AB -This paper presents a correct solution to the optimal feedback control for a nonholonomic vehicle with limited field-of-view. Previous work on this subject has shown that the search for a shortest path can be limited to simple families of trajectories. We preliminarily provide an extension of the alphabet of optimal control words, to cover some regions of the vehicle plane where the synthesis of turns out to be suboptimal. The main contribution of this paper is an algorithm to translate the optimal synthesis to the image plane, thus enabling a purely image-based optimal control scheme. This allows better performance and increases the robustness of the overall process, avoiding the need of slowly-converging and error-prone parameter estimation algorithms. Simulations and experiments are reported which demonstrate the effectiveness of the proposed technique.

JF - IROS ER - TY - CONF T1 - Robust Almost Sure Stability for Uncertain Stochastically Scheduled Anytime Controllers T2 - Control and Automation, 16 th Mediterranean Conference on Control and Automation Y1 - 2008 A1 - D. Fontanelli A1 - L. Greco A1 - A. Bicchi KW - Robotics AB -In this paper we consider closed loop stability of a number of different software tasks implementing a hierarchy of real-time controllers for a given plant, i.e.

JF - Control and Automation, 16 th Mediterranean Conference on Control and Automation ER - TY - CONF T1 - Almost Sure Stability of Anytime Controllers via Stochastic Scheduling T2 - Proc. IEEE Int. Conf. on Decision and Control Y1 - 2007 A1 - L. Greco A1 - D. Fontanelli A1 - A. Bicchi KW - Embedded Control KW - Robotics AB -In this paper we consider scheduling the execution of a number of different software tasks implementing a hierarchy of real-time controllers for a given plant. Controllers are considered to be given and ordered according to a measure of the performance they provide. Software tasks implementing higher-performance controllers are assumed to require a larger worst-case execution time. Control tasks are to be scheduled within given availability limits on execution time, which change stochastically in time. The ensuing switching system is prone to instability, unless a very conservative policy is enforced of always using the simplest, least performant controller. The presented method allows to condition the stochastic scheduling of control tasks so as to obtain a better exploitation of computing capabilities, while guaranteeing almost sure stability of the resulting switching system.

JF - Proc. IEEE Int. Conf. on Decision and Control ER - TY - JOUR T1 - Comments on Necessary and Sufficient Vertex Solutions for Robust Stability Analysis of Families of Linear State Space Systems JF - Dyn. Contin. Discrete Impuls. Syst. Ser. B Appl. Algorithms Y1 - 2007 A1 - L. Greco KW - Robotics VL - 14 ER - TY - CONF T1 - Steering Dynamical Systems with Finite Plans and Limited Path Length T2 - European Control Conference Y1 - 2007 A1 - L. Greco A1 - A. Fagiolini A1 - A. Bicchi A1 - B. Piccoli KW - Embedded Control KW - Robotics AB -Complex dynamical systems can be steered by using symbolic input plans. These plans must have a finite descriptive length, and can be expressed by means of words chosen in an alphabet of symbols. In this way, such plans can be sent through a limited capacity channel to a remote system, where they are decoded in suitable control actions. The choice of this symbols is essential to efficiently encode steering plans. To this aim, in this paper, we state the problem of finding symbols maximizing the interval of points reachable by the system along paths with constrained length. We focus on the problem with two symbols, and compare the results with those produced by plans not accounting for the length constraint. Moreover, the behavior of a simple helicopter, steered by both kinds of plans, has been simulated, in order to illustrate the power of the overall control system, and to emphasize the improvements introduced by the new plans.

JF - European Control Conference ER - TY - CONF T1 - Adaptive non Linear Control of Dynamic Mobile Robots with Parameters Uncertainty T2 - Int. IFAC Symp. on Robot Control Y1 - 2006 A1 - D. Fontanelli A1 - R. Viviani A1 - L. Greco A1 - A. Caiti A1 - A. Bicchi KW - Embedded Control KW - Robotics AB -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.

JF - Int. IFAC Symp. on Robot Control CY - Bologna, Italy ER - TY - ABST T1 - Any Time Control Y1 - 2006 A1 - D. Fontanelli A1 - L. Greco KW - Embedded Control KW - Robotics AB -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.

PB - Interdepartmental Research Center E. Piaggio, University of Pisa CY - Pisa, Italy ER - TY - JOUR T1 - A Geometry-Based Algorithm for the Stability of Planar Switching Systems JF - Int. J. of Systems Science Y1 - 2006 A1 - L. Greco A1 - F. Tocchini A1 - M. Innocenti KW - Embedded Control KW - Robotics VL - 37 ER - TY - CONF T1 - Symbolic Control for Underactuated Differentially Flat Systems T2 - Proc. IEEE Int. Conf. on Robotics and Automation Y1 - 2006 A1 - A. Fagiolini A1 - L. Greco A1 - A. Bicchi A1 - B. Piccoli A1 - A. Marigo KW - Embedded Control KW - Robotics AB -In this paper we address the problem of generating input plans to steer complex dynamical systems in an obstacle-free environment. Plans considered admit a finite description length and are constructed by words on an alphabet of input symbols, which could be e.g. transmitted through a limited capacity channel to a remote system, where they can be decoded in suitable control actions. We show that, by suitable choice of the control encoding, finite plans can be efficiently built for a wide class of dynamical systems, computing arbitrarily close approximations of a desired equilibrium in polynomial time. Moreover, we illustrate by simulations the power of the proposed method, solving the steering problem for two examples in the class of underactuated systems, which have attracted wide attention in the recent literature.

JF - Proc. IEEE Int. Conf. on Robotics and Automation ER - TY - ABST T1 - Adaptive nonlinear control of dynamic mobile robots with parameters uncertainty Y1 - 2005 A1 - A. Bicchi A1 - A. Caiti A1 - D. Fontanelli A1 - L. Greco A1 - R. Viviani KW - Embedded Control KW - Robotics AB -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.

PB - Dipartimento di Sistemi Elettrici e Automazione, Università di Pisa ER - TY - THES T1 - Stability and Stabilization Issues in Switched Systems Y1 - 2005 A1 - L. Greco KW - Robotics PB - University of Pisa ER - TY - CONF T1 - Stabilization of a Class of Planar Nonlinear Systems T2 - 44th IEEE CDC-ECC'05 Y1 - 2005 A1 - F. Tocchini A1 - L. Greco A1 - M. Innocenti KW - Robotics JF - 44th IEEE CDC-ECC'05 CY - Seville, Spain ER - TY - CONF T1 - Stabilization of a Class of Unstable Switching Systems T2 - 12th IEEE Mediterranean Conference Y1 - 2004 A1 - L. Greco A1 - F. Tocchini A1 - M. Innocenti KW - Robotics JF - 12th IEEE Mediterranean Conference CY - Kusadasi, Turkey ER - TY - ABST T1 - Necessary and Sufficient Conditions for Asymptotic Stability of Second Order LTI Switching Systems Y1 - 2003 A1 - L. Greco A1 - F. Tocchini A1 - M. Innocenti KW - Robotics PB - Dept. of Electrical Systems and Automation, University of Pisa ER - TY - JOUR T1 - Sliding Mode Control for Two-Time Scale Systems: Stability Issues JF - Automatica Y1 - 2003 A1 - M. Innocenti A1 - L. Greco A1 - L. Pollini KW - Robotics VL - 39 ER - TY - CONF T1 - Stability Issues in Dual Time Scale Systems T2 - American Control Conference Y1 - 2002 A1 - M. Innocenti A1 - L. Greco A1 - L. Pollini KW - Robotics JF - American Control Conference CY - Anchorage, Alaska ER - TY - ABST T1 - Variable Structure Control for Singularly Perturbed System: Stability Issues Y1 - 2002 A1 - M. Innocenti A1 - L. Greco KW - Robotics PB - Dept. of Electrical Systems and Automation, University of Pisa CY - Pisa, Italy ER -