arXiv subjects

Hashem Ashrafiuon

Publications and source records attributed to Hashem Ashrafiuon.

4 recordsLinked to original sources

arXiv2025

Extremum Seeking Control for Antenna Pointing via Symmetric Product Approximation

This paper investigates extremum seeking control for a torque-controlled antenna pointing system without direct angular measurements. We consider a two-degree-of-freedom (2-DOF) antenna system that receives an unknown signal from its environment, where the signal strength varies with the antenna orientation. It is assumed that only real-time measurements of the signal are available. We develop an extremum seeking control strategy that enables the antenna to autonomously adjust its direction to maximize the received signal strength based on the symmetric product approximation. Under suitable assumptions on the signal function, we prove local practical uniform asymptotic stability for the closed-loop system.

eess.SY↗

arXiv2022

Underactuated Source Seeking by Surge Force Tuning: Theory and Boat Experiments

We extend source seeking algorithms, in the absence of position and velocity measurements, and with tuning of the surge input, from velocity-actuated (unicycle) kinematic models to force-actuated generic Euler-Lagrange dynamic underactuated models. In the design and analysis, we employ a symmetric product approximation, averaging, passivity, and partial-state stability theory. The proposed control law requires only real-time measurement of the source signal at the current position of the vehicle and ensures semi-global practical uniform asymptotic stability (SPUAS) with respect to the linear motion coordinates for the closed-loop system. The performance of our source seeker with surge force tuning is illustrated with both numerical simulations and experiments of an underactuated boat.

eess.SY↗

arXiv2021

Collision-Free Continuum Deformation Coordination of a Multi-Quadcopter System Using Cooperative Localization

This paper integrates cooperative localization with continuum deformation coordination of a multi-quadcopter system {(MQS) to assure safety and optimality of the quadcopter team coordination in the presence of position uncertainty. We first consider the MQS as a finite number of particles of a deformable triangle in a $3$-D motion space and define their continuum deformation coordination as a leader-follower problem in which leader quadcopters} can estimate (know) their positions but follower quadcopters rely on relative position measurements to localize themselves and estimate the leaders' positions. We then propose a navigation strategy for the MQS to plan and acquire the desired continuum deformation coordination, in the presence of measurement noise, disturbance, and position uncertainties, such that collision is avoided and rotor angular speeds of all quadcopters remain bounded. We show the efficacy of the proposed strategy by simulating the continuum deformation coordination of an MQS with eight quadcopters.

math.DS↗

arXiv2021

Continuum Deformation Coordination of Multi-Agent Systems Using Cooperative Localization

This paper studies the problem of decentralized continuum deformation coordination of multi-agent systems aided by cooperative localization. We treat agents as particles inside a triangular continuum (deformable body) in a2-D motion space and let the continuum deformation coordination be defined by three leaders located at vertices of a triangle, called the leading triangle. The leaders desired trajectories are assigned as the solution of a constrained optimal control problem such that safety requirements are satisfied in the presence of disturbance and measurement noise. Followers distributed inside the leading tri-angle acquire continuum deformation in a decentralized fashion by integrating cooperative localization and local communication. Specifically, cooperative localization estimates the global positions of all agents using relative position measurements based primarily on proximity of agents. Simulation results are presented for a network of ten agents.

cs.MA↗