3,616 research outputs found
Vision-based control of multi-agent systems
Scope and Methodology of Study: Creating systems with multiple autonomous vehicles places severe demands on the design of decision-making supervisors, cooperative control schemes, and communication strategies. In last years, several approaches have been developed in the literature. Most of them solve the vehicle coordination problem assuming some kind of communications between team members. However, communications make the group sensitive to failure and restrict the applicability of the controllers to teams of friendly robots. This dissertation deals with the problem of designing decentralized controllers that use just local sensor information to achieve some group goals.Findings and Conclusions: This dissertation presents a decentralized architecture for vision-based stabilization of unmanned vehicles moving in formation. The architecture consists of two main components: (i) a vision system, and (ii) vision-based control algorithms. The vision system is capable of recognizing and localizing robots. It is a model-based scheme composed of three main components: image acquisition and processing, robot identification, and pose estimation.Using vision information, we address the problem of stabilizing groups of mobile robots in leader- or two leader-follower formations. The strategies use relative pose between a robot and its designated leader or leaders to achieve formation objectives. Several leader-follower formation control algorithms, which ensure asymptotic coordinated motion, are described and compared. Lyapunov's stability theory-based analysis and numerical simulations in a realistic tridimensional environment show the stability properties of the control approaches
Formation Shape Control Based on Distance Measurements Using Lie Bracket Approximations
We study the problem of distance-based formation control in autonomous
multi-agent systems in which only distance measurements are available. This
means that the target formations as well as the sensed variables are both
determined by distances. We propose a fully distributed distance-only control
law, which requires neither a time synchronization of the agents nor storage of
measured data. The approach is applicable to point agents in the Euclidean
space of arbitrary dimension. Under the assumption of infinitesimal rigidity of
the target formations, we show that the proposed control law induces local
uniform asymptotic stability. Our approach involves sinusoidal perturbations in
order to extract information about the negative gradient direction of each
agent's local potential function. An averaging analysis reveals that the
gradient information originates from an approximation of Lie brackets of
certain vector fields. The method is based on a recently introduced approach to
the problem of extremum seeking control. We discuss the relation in the paper
Angle-Constrained Formation Control for Circular Mobile Robots
In this letter, we investigate the formation control problem of mobile robots moving in the plane where, instead of assuming robots to be simple points, each robot is assumed to have the form of a disk with equal radius. Based on interior angle measurements of the neighboring robots’ disk, which can be obtained from low-cost vision sensors, we propose a gradient-based distributed control law and show the exponential convergence property of the associated error system. By construction, the proposed control law has the appealing property of ensuring collision avoidance between neighboring robots. We also present simulation results for a team of four circular mobile robots forming a rectangular shape
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 velocity of the agents in a multi
agent system. Simulation results are provided to illustrate the performance of
the proposed algorithm.This work was
supported by National ICT Australia, which is funded by the Australian
Research Council through the ICT Centre of Excellence program and
is also supported by the Australian Research Council under Grant
DP110100538
Bearing Rigidity and Almost Global Bearing-Only Formation Stabilization
A fundamental problem that the bearing rigidity theory studies is to determine when a framework can be uniquely determined up to a translation and a scaling factor by its inter-neighbor bearings. While many previous works focused on the bearing rigidity of two-dimensional frameworks, a first contribution of this paper is to extend these results to arbitrary dimensions. It is shown that a framework in an arbitrary dimension can be uniquely determined up to a translation and a scaling factor by the bearings if and only if the framework is infinitesimally bearing rigid. In this paper, the proposed bearing rigidity theory is further applied to the bearing-only formation stabilization problem where the target formation is defined by inter-neighbor bearings and the feedback control uses only bearing measurements. Nonlinear distributed bearing-only formation control laws are proposed for the cases with and without a global orientation. It is proved that the control laws can almost globally stabilize infinitesimally bearing rigid formations. Numerical simulations are provided to support the analysis
Animal-Inspired Agile Flight Using Optical Flow Sensing
There is evidence that flying animals such as pigeons, goshawks, and bats use
optical flow sensing to enable high-speed flight through forest clutter. This
paper discusses the elements of a theory of controlled flight through obstacle
fields in which motion control laws are based on optical flow sensing.
Performance comparison is made with feedback laws that use distance and bearing
measurements, and practical challenges of implementation on an actual robotic
air vehicle are described. The related question of fundamental performance
limits due to clutter density is addressed.Comment: 20 pages, 7 figure
- …