Ali Saberi - Academia.edu (original) (raw)

Papers by Ali Saberi

arXiv (Cornell University), Oct 25, 2022

This paper studies global regulated state synchronization of discrete-time double-integrator mult... more This paper studies global regulated state synchronization of discrete-time double-integrator multi-agent systems subject to actuator saturation by utilizing localized information exchange. We propose a scale-free linear protocol that achieves global regulated state synchronization for any network with arbitrary number of agents and arbitrarily directed communication graph that has a path between each agent and exosystem which generates the reference trajectory.

International Journal of Robust and Nonlinear Control, 2019

This paper studies H 2 and H ∞ almost output synchronization problems for heterogeneous continuou... more This paper studies H 2 and H ∞ almost output synchronization problems for heterogeneous continuous-time multiagent systems with passive agents and strongly connected communication graph. For non-introspective passive agents, a linear static protocol can be designed to achieve almost output synchronization with arbitrarily small H 2 norm. Moreover, we show that the H ∞ almost output synchronization problem via static protocol is not solvable for this class of systems. KEYWORDS heterogeneous multiagent systems, H ∞ and H 2 almost output synchronization, synchronization in complex networks of dynamical systems 6244

Lecture Notes in Computer Science, 2006

Motivated by the need for agent classification in sensor networking and autonomous vehicle contro... more Motivated by the need for agent classification in sensor networking and autonomous vehicle control applications, we propose a flexible and distributed stochastic automaton-based network partitioning algorithm that is capable of finding the optimal k-way partition with respect to a broad range of cost functions, and given various constraints, in directed and weighted graphs. Specifically, we motivate the need for new algorithms for network partitioning and distributed (or self-) partitioning. We then review our stochastic automaton-based partitioning algorithm, and extend its use for network partitioning and self-partitioning problems. Finally, the application of the algorithm to mobile/sensor classification in ad hoc networks is pursued in detail, and other applications are briefly introduced.

Proceedings of 1995 American Control Conference - ACC'95

Proceedings of the IEEE, 1997

International Journal of Control, 1994

The work explores a specific scenario for structural computational optimization based on the foll... more The work explores a specific scenario for structural computational optimization based on the following elements: (a) a relaxed optimization setting considering the ersatz (bi-material) approximation, (b) a treatment based on a nonsmoothed characteristic function field as a topological design variable, (c) the consistent derivation of a relaxed topological derivative whose determination is simple, general and efficient, (d) formulation of the overall increasing cost function topological sensitivity as a suitable optimality criterion, and (e) consideration of a pseudo-time framework for the problem solution, ruled by the problem constraint evolution. In this setting, it is shown that the optimization problem can be analytically solved in a variational framework, leading to, nonlinear, closed-form algebraic solutions for the characteristic function, which are then solved, in every time-step, via fixed point methods based on a pseudo-energy cutting algorithm combined with the exact fulfillment of the constraint, at every iteration of the non-linear algorithm, via a bisection method. The issue of the ill-posedness (mesh dependency) of the topological solution, is then easily solved via a Laplacian smoothing of that pseudo-energy. In the aforementioned context, a number of (3D) topological structural optimization benchmarks are solved, and the solutions obtained with the explored closed-form solution method, are analyzed, and compared, with their solution through an alternative level set method. Although the obtained results, in terms of the cost function and topology designs, are very similar in both methods, the associated computational cost is about five times smaller in the closedform solution method this possibly being one of its advantages. Some comments, about the possible application of the method to other topological optimization problems, as well as envisaged modifications of the explored method to improve its performance close the work.

IEEE Transactions on Mobile Computing, 2006

IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1998

This brief establishes easy-to-verify necessary and sufficient conditions for global asymptotic s... more This brief establishes easy-to-verify necessary and sufficient conditions for global asymptotic stability of a class of continuous time planar systems which are subject to state saturation nonlinearities on both its state variables.

IEEE Transactions on Automatic Control, 1995

In this paper we consider the problem of robust semiglobal stabilization and/or semiglobal practi... more In this paper we consider the problem of robust semiglobal stabilization and/or semiglobal practical stabilization of minimum-phase input-output linearizable systems. The results of this paper significantly extend the recent work of Teel and Praly on SISO (single-input/single-output) minimum-phase systems in several directions. Among these directions are the development of MIMO (multi-input/multi-output) theory and the relaxation of the restriction on the interaction between nonlinear zero dynamics and the state of the linearizable part of the system. (A. B. C) required in 1161 for global stabilization is relaxed by allowing repeated invariant zeros on the jw-axis. This is a ' A linear system (-4. B. C) is said to be of weakly minimum phase if its zero dynamics is stable in the Tense of Lyapunov.

For a double integrator subject to input saturation, it is well-known that linear control laws ca... more For a double integrator subject to input saturation, it is well-known that linear control laws can achieve global asymptotic stability. But a study of external stability for such a simple system reveals an unexpectedly rich nature. It is shown in this paper that external L p stability for non-input-additive disturbance only holds for p ≤ 2, but not for p > 2 no matter what linear control law is used. However, for input-additive disturbance, L p stability holds for all 1 ≤ p < ∞. As a third result, we show that the double integrator system controlled by a saturating linear feedback is not input-to-state stable (ISS) even when all disturbances have their magnitudes restricted to be arbitrarily small. These results for the first time reveal that external stability of nonlinear systems is essentially different from that of linear systems. A fundamental discovery in this study is that the external stability of nonlinear systems cannot be separated from the internal state behavior.

International Journal of Robust and Nonlinear Control, 2018

This paper studies the synchronization problem for multiagent systems with identical continuous-o... more This paper studies the synchronization problem for multiagent systems with identical continuous-or discrete-time agents with unknown nonuniform constant input delays. The agents are connected via full-or partial-state coupling. The agents are assumed to be asymptotically null controllable, ie, all eigenvalues are in the closed left-half complex plane for continuous-time agents or in the closed unit disc for discrete-time agents. We derive an upper bound for the input delay tolerance, which explicitly depends on the agent dynamics. Moreover, for any unknown delay satisfying this upper bound, a low-gain-based protocol design methodology is proposed without relying on exact knowledge of the network topology such that synchronization is achieved among agents for any network graph in a given set.

2012 American Control Conference (ACC), 2012

We present an observer for estimating position, velocity, attitude, and gyro bias, by using inert... more We present an observer for estimating position, velocity, attitude, and gyro bias, by using inertial measurements of accelerations and angular velocities, magnetometer measurements, and satellite-based measurements of position and (optionally) velocity. The design proceeds in two stages: in Stage I, an attitude and gyro bias estimator is designed based on an unmeasured signal. In Stage II, that design is recovered using measured signals only, by combining it with a position and velocity estimator. We prove exponential convergence of the estimation error from all desired initial conditions and test the design using realistic flight simulation.

IEE Proceedings D Control Theory and Applications, 1993

We define the following subspaces: 1'9(A, B, C, D) is the maximal subspace of IRnwhich is (A + BF... more We define the following subspaces: 1'9(A, B, C, D) is the maximal subspace of IRnwhich is (A + BF)-invariant and contained in Ker (C + DF) such that the eigenvalues of (A + BF) 11'9 are contained in C9~C for some F.

International Journal of Distributed Sensor Networks, 2008

This article proposes a flexible and distributed stochastic automaton-based network partitioning ... more This article proposes a flexible and distributed stochastic automaton-based network partitioning algorithm that is capable of finding the optimal k-way partition with respect to a broad range of cost functions, and given various constraints, in directed and weighted graphs. Specifically, we motivate the distributed partitioning (self-partitioning) problem, introduce the stochastic automaton-based partitioning algorithm, and show that the algorithm finds the optimal partition with probability 1 for a large class of partitioning tasks. Also, a discussion of why the algorithm can be expected to find good partitions quickly is included, and its performance is further illustrated through examples. Finally, applications to mobile/sensor classification in ad hoc networks, fault-isolation in electric power systems, and control of autonomous vehicle teams are pursued in detail.

Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148), 2001

49th IEEE Conference on Decision and Control (CDC), 2010

We consider the problem of observer design for a class of systems described by an observable line... more We consider the problem of observer design for a class of systems described by an observable linear system perturbed by nonlinear, time-varying terms. In particular, we investigate conditions under which the effect of the nonlinear terms may be dominated by using sufficiently high gain. Our main tool is the transformation of the original system to a canonical form suitable for high-gain design, which is similar or equivalent to canonical forms used elsewhere in the high-gain literature. We demonstrate that linear, nonsingular transformations to this canonical form can easily be constructed using available tools, but that many systems do not allow for such a transformation. Our main contribution is a constructive algorithm that aims to rectify this problem by dynamically shaping the output.

Automatica, 2015

This paper deals with the construction of nonlinear observers for navigation purposes. We first p... more This paper deals with the construction of nonlinear observers for navigation purposes. We first present a globally exponentially stable observer for attitude and gyro bias, based on gyro measurements and two or more pairs of vector measurements. We avoid the well-known topological obstructions to global stability by not confining the attitude estimate to SO(3), but rather estimating a full rotation matrix with nine degrees of freedom. We also show how the attitude can be estimated under a relaxed persistency-of-excitation condition, with a single vector measurement as a special case. Next, we use the attitude observer to construct a globally exponentially stable observer for GNSS/INS integration, based on accelerometer, gyro, and magnetometer measurements, as well as GNSS measurements of position and (optionally) velocity. We verify the stability properties of the design using experimental data from a light fixed-wing aircraft.

Proceedings 2005 IEEE Swarm Intelligence Symposium, 2005. SIS 2005.

AIAA Guidance, Navigation, and Control Conference, 2010

2008 47th IEEE Conference on Decision and Control, 2008