Mohammad Deghat

Localization and Circumnavigation of a Slowly Moving Target Using Bearing Measurements

The problem of localization and circumnavigation of a slowly moving target with unknown speed has been considered. The agent only knows its own position with respect to its initial frame, and the bearing angle to the target in that frame. We propose an estimator to localize the target and a control law that forces the agent to move on a circular trajectory around the target such that both the estimator and the control system are exponentially stable. We consider two different cases where the agents speed is constant and variable. The performance of the proposed algorithm is verified through simulations.

Target localization and circumnavigation using bearing measurements in 2D

This paper considers the problem of localization and circumnavigation of a slowly drifting target with unknown speed using the agents known position and the bearing angle of the target. We first assume that the target is stationary and propose an estimator to localize the target and a control law that forces the agent to move on a circular trajectory around the target such that both the estimator and the control system are exponentially stable. Then the case where the target might experience slow but possibly steady movement is studied.

Finite Time Distance-based Rigid Formation Stabilization and Flocking

Abstract Most of the existing results on distributed distance-based rigid formation control establish asymptotic and often exponentially asymptotic convergence. To further improve the convergence rate, we explain in this paper how to modify existing controllers to obtain finite time stability. For point agents modeled by single integrators, the controllers proposed in this paper drive the whole formation to converge to a desired shape with finite settling time. For agents modeled by double integrators, the proposed controllers allow all agents to both achieve the same velocity and reach a desired shape in finite time. All controllers are totally distributed. Simulations are also provided to validate the proposed control.

Target localization and circumnavigation by a non-holonomic robot

This paper addresses a surveillance problem in which the goal is to achieve a circular motion around a target by a non-holonomic agent. The agent only knows its own position with respect to its initial frame, and the bearing angle of the target in that frame. It is assumed that the position of the target is unknown. An estimator and a controller are proposed to estimate the position of the target and make the agent move on a circular trajectory with a desired radius around it. The performance of the proposed algorithm is verified both through simulations and experiments. Robustness is also established in the face of noise and target motion.

Combined Flocking and Distance-Based Shape Control of Multi-Agent Formations

Steepest descent control laws can be used for formation shape control based on specified inter-agent distances, assuming point agents with single integration of the control action to yield velocity. Separately, it is known how to achieve equal velocity for a collection of agents in a formation using consensus ideas, given appropriate properties for the graph describing information flows. This work shows how the two concepts of formation shape control and flocking behavior can be combined when one changes from an agent with single integration to one with double integration.

Distributed Localization Via Barycentric Coordinates: Finite-Time Convergence

Abstract We consider distributed localization in a sensor network in R 2 from inter-agent distances. Sensors and anchors exchange data with their neighbors. No centralized data processing is required. We establish a differential equation for the unknown sensor positions, and show that the estimated positions of sensors converge to their actual values in finite time (assuming noise-free measurements). The key assumption is that all sensors are in the convex hull of three or more anchors. The proposed localization method uses the barycentric coordinates of each sensor with respect to some of its neighbors (which may not include those anchors), assuming the sensor falls in the convex hull of these neighbors.

Translational velocity consensus using distance-only measurements

This paper proposes a strategy to achieve translational velocity consensus in a multi-agent formation using distance-only measurements. Since with agents executing arbitrary motions, distance-only measurement cannot provide enough information for velocity consensus, we postulate that agents engage in a combination of circular motion and linear motion. When energy saving is the first priority, the linear motion component should dominate. On the other hand, when measurement accuracy is the first priority, the circular motion must be more prominent.

Simultaneous Velocity and Position Estimation via Distance-only Measurements with Application to Multi-Agent System Control

This paper proposes a strategy to estimate the velocity and position of neighbor agents using distance measurements only. Since with agents executing arbitrary motions, instantaneous distance-only measurements cannot provide enough information for our objectives, we postulate that agents engage in a combination of circular motion and linear motion. The proposed estimator can be used to develop control algorithms where only distance measurements are available to each agent. As an example, we show how this estimation method can be used to control the formation shape and secure velocity consensus of the agents in a multi agent system.

Detection of biasing attacks on distributed estimation networks

The paper addresses the problem of detecting attacks on distributed estimator networks that aim to intentionally bias process estimates produced by the network. It provides a sufficient condition, in terms of the feasibility of certain linear matrix inequalities, which guarantees distributed input attack detection using an H∞ approach.

Rigid Formation Control of Double-Integrator Systems

ABSTRACT In this paper, we study rigid formation control systems modelled by double integrators. Two kinds of double-integrator formation systems are considered, namely formation stabilisation systems and flocking control systems. Novel observations on the measurement requirement, the null space and eigenvalues of the system Jacobian matrix will be provided, which reveal important properties of system dynamics and the associated convergence results. We also establish some new links between single-integrator formation systems and double-integrator formation systems via a parameterised Hamiltonian system, which, in addition, provide novel stability criteria for different equilibria in double-integrator formation systems by using available results in single-integrator formation systems.