Formation control and coordination of autonomous agents

Abstract

The primary purpose of this thesis is to present new results in the field of localization, co-ordination and control of multi-agent systems. In the first part of the thesis, initially, the problem of localization in the presence of inter-agent noisy measurements is formalized and it is established that approximate localizability, i.e. the ability to calculate the approximate positions of the agents, is a generic property and as long as the magnitude of noise is smaller than an upper bound, one can solve the approximate localization problem. Moreover, it is shown that the accuracy of the approximate localization solution using distance measurements of a formation depends on the choice of the nodes with the known positions, anchors, in the formation. Additionally, a method to select these anchors in the network is introduced which minimizes some performance index associated with the error in the approximate solution for the positions of the agents in the formation. In the next chapter, some methods based on polynomial optimization are proposed that can be employed to solve two important problems of cooperative target localization and reference frame determination using different types of measurements. The first part of the thesis is concluded by addressing another localization problem that arose in an experiment conducted by Australia Defence Science and Technology Organization (DSTO). The problem of interest is to localize a formation of unmanned aerial vehicles (UAVs) capable of measuring the inter-agent distances or angles, and the angles subtended at each of them by two landmarks at known positions. We tackle this problem using tools from graph theory and linkage mechanism design. In the second part of this thesis, we shift our focus to motion control of autonomous agents. First, we address the problem of simultaneous localization and circumnavigation of an initially stationary target at an unknown position by a single agent aware of its own trajectory that is capable of measuring its distance to the target. We propose, a control law and an estimator that achieves this objective exponentially fast. Later, we extend our analysis to the case where the target is moving and calculate an upper bound for the estimation error in terms of the target speed. The last problem that we consider is the problem of forcing a set of agents initially at arbitrary positions subject to a constant speed constraint to rotate around a target at a known position forming a prescribed formation shape while guaranteeing that no collision occurs. We show that our proposed algorithm achieves this objective under some mild and realistic assumptions in finite time. Show more