Existence and Completeness of Bounded Disturbance Observers: A Set-Membership Viewpoint

This paper investigates the boundedness of the Disturbance Observer (DO) for linear discrete-time systems. In contrast to previous studies that focus on analyzing and/or designing observer gains, our analysis and synthesis approach is based on a set-membership viewpoint. From this viewpoint, a necessary and sufficient existence condition of bounded DOs is first established, which can be easily verified. Furthermore, a set-membership filter-based DO is developed, and its completeness is proved; thus, our proposed DO is bounded if and only if bounded DOs exist. We also prove that the proposed DO has the capability to achieve the worst-case optimality, which can provide a benchmark for the design of DOs. Finally, numerical simulations are performed to corroborate the effectiveness of the theoretical results

Implementation of UAV Coordination Based on a Hierarchical Multi-UAV Simulation Platform

In this paper, a hierarchical multi-UAV simulation platform,called XTDrone, is designed for UAV swarms, which is completely open-source 4 . There are six layers in XTDrone: communication, simulator,low-level control, high-level control, coordination, and human interac-tion layers. XTDrone has three advantages. Firstly, the simulation speedcan be adjusted to match the computer performance, based on the lock-step mode. Thus, the simulations can be conducted on a work stationor on a personal laptop, for different purposes. Secondly, a simplifiedsimulator is also developed which enables quick algorithm designing sothat the approximated behavior of UAV swarms can be observed inadvance. Thirdly, XTDrone is based on ROS, Gazebo, and PX4, andhence the codes in simulations can be easily transplanted to embeddedsystems. Note that XTDrone can support various types of multi-UAVmissions, and we provide two important demos in this paper: one is aground-station-based multi-UAV cooperative search, and the other is adistributed UAV formation flight, including consensus-based formationcontrol, task assignment, and obstacle avoidance.Comment: 12 pages, 10 figures. And for the, see https://gitee.com/robin_shaun/XTDron

Communications in Mobile Wireless Networks: A Finite Time-Horizon Viewpoint

In mobile wireless networks (MWNs), short-term communications carry two key features: 1) Different from communications over a large time window where the performance is governed by the long-term average effect, the short-term communications in MWNs are sensitive to the instantaneous location and channel condition caused by node mobility. 2) The short-term communications in MWNs have the finite blocklength coding effect which means it is not amenable to the well-known Shannon's capacity formulation. To deal with the short-term communications in MWNs, this thesis focuses on three main issues: how the node mobility affects the instantaneous interference, how to reduce the uncertainty in the locations of mobile users, and what is the maximal throughput of a multi-user network over a short time-horizon. First, we study interference prediction in MWNs by proposing and using a general-order linear model for node mobility. The proposed mobility model can well approximate node dynamics of practical MWNs. Unlike previous studies on interference statistics, we are able through this model to give a best estimate of the time-varying interference at any time rather than long-term average effects. In particular, we propose a compound Gaussian point process functional (CGPPF) in a general framework to obtain analytical results on the mean value and moment-generating function of the interference prediction. Second, to reduce the uncertainty in nodal locations, the cooperative localization problem for mobile nodes is studied. In contrast to previous works, which highly rely on the synchronized time-slotted systems, this cooperative localization framework we establish does not need any synchronization for the communication links and measurement processes in the entire wireless network. To solve the cooperative localization problem in a distributed manner, we first propose the centralized localization algorithm based on the global information, and use it as the benchmark. Then, we rigorously prove when a localization estimation with partial information has a small performance gap from the one with global information. Finally, by applying this result at each node, the distributed prior-cut algorithm is designed to solve this asynchronous localization problem. Finally, we study the throughput region of any MWN consisting of multiple transmitter-receiver pairs where interference is treated as noise. Unlike the infinite-horizon throughput region, which is simply the convex hull of the throughput region of one time slot, the finite-horizon throughput region is generally non-convex. Instead of directly characterizing all achievable rate-tuples in the finite-horizon throughput region, we propose a metric termed the rate margin, which not only determines whether any given rate-tuple is within the throughput region (i.e., achievable or unachievable), but also tells the amount of scaling that can be done to the given achievable (unachievable) rate-tuple such that the resulting rate-tuple is still within (brought back into) the throughput region. This thesis advances our understanding in communications in MWNs from a finite-time horizon viewpoint. It establishes new frameworks for tracking the instantaneous behaviors, such as interference and nodal location, of MWNs. It also reveals the fundamental limits on short-term communications of a multi-user mobile network, which sheds light on communications with low latency

Covert communication with finite blocklength in AWGN channels

Covert communication is to achieve a reliable transmission from a transmitter to a receiver while guaranteeing an arbitrarily small probability of this transmission being detected by a warden. In this work, we study the covert communication in AWGN channels with finite blocklength, in which the number of channel uses is finite. Specifically, we analytically prove that the entire block (all available channel uses) should be utilized to maximize the effective throughput of the transmission subject to a predetermined covert requirement. This is a nontrivial result because more channel uses results in more observations at the warden for detecting the transmission. We also determine the maximum allowable transmit power per channel use, which is shown to decrease as the blocklength increases. Despite the decrease in the maximum allowable transmit power per channel use, the maximum allowable total power over the entire block is proved to increase with the blocklength, which leads to the fact that the effective throughput increases with the blocklength.ARC Discovery Projects Grant DP15010390

Cooperative Filtering with Range Measurements: A Distributed Constrained Zonotopic Method

This article studies the distributed estimation problem of a multi-agent system with bounded absolute and relative range measurements. Parts of the agents are with high-accuracy absolute measurements, which are considered as anchors; the other agents utilize lowaccuracy absolute and relative range measurements, each derives an uncertain range that contains its true state in a distributed manner. Different from previous studies, we design a distributed algorithm to handle the range measurements based on extended constrained zonotopes, which has low computational complexity and high precision. With our proposed algorithm, agents can derive their uncertain range sequentially along the chain topology, such that agents with low-accuracy sensors can benefit from the high-accuracy absolute measurements of anchors and improve the estimation performance. Simulation results corroborate the effectiveness of our proposed algorithm and verify our method can significantly improve the estimation accuracy.Comment: 15 pages 6 figure