Decentralized Visual-Inertial-UWB Fusion for Relative State Estimation of Aerial Swarm

The collaboration of unmanned aerial vehicles (UAVs) has become a popular research topic for its practicability in multiple scenarios. The collaboration of multiple UAVs, which is also known as aerial swarm is a highly complex system, which still lacks a state-of-art decentralized relative state estimation method. In this paper, we present a novel fully decentralized visual-inertial-UWB fusion framework for relative state estimation and demonstrate the practicability by performing extensive aerial swarm flight experiments. The comparison result with ground truth data from the motion capture system shows the centimeter-level precision which outperforms all the Ultra-WideBand (UWB) and even vision based method. The system is not limited by the field of view (FoV) of the camera or Global Positioning System (GPS), meanwhile on account of its estimation consistency, we believe that the proposed relative state estimation framework has the potential to be prevalently adopted by aerial swarm applications in different scenarios in multiple scales.Comment: Accepted ICRA 202

A single-camera gaze tracking system under natural light

Gaze tracking is a human-computer interaction technology, and it has been widely studied in the academic and industrial fields. However, constrained by the performance of the specific sensors and algorithms, it has not been popularized for everyone. This paper proposes a single-camera gaze tracking system under natural light to enable its versatility. The iris center and anchor point are the most crucial factors for the accuracy of the system. The accurate iris center is detected by the simple active contour snakuscule, which is initialized by the prior knowledge of eye anatomical dimensions. After that, a novel anchor point is computed by the stable facial landmarks. Next, second-order mapping functions use the eye vectors and the head pose to estimate the points of regard. Finally, the gaze errors are improved by implementing a weight coefficient on the points of regard of the left and right eyes. The feature position of the iris center achieves an accuracy of 98.87% on the GI4E database when the normalized error is lower than 0.05. The accuracy of the gaze tracking method is superior to the-state-of-the-art appearance-based and feature-based methods on the EYEDIAP database

Let the light guide us: VLC-based localization

We propose to use visible-light beacons for low-cost indoor localization. Modulated light-emitting diode (LED) lights are adapted for localization as well as illumination. The proposed solution consists of two components: light-signal decomposition and Bayesian localization

Performance Analysis of A Burst-Frame-Based MAC Protocol for Ultra-Wideband Ad Hoc Networks

Abstract — Ultra-wideband (UWB) communication is becomin

On Medium Access Control for High Data Rate Ultra-Wideband Ad Hoc Networks

A critical challenge in ultra-wideband (UWB) system design is that a receiver usually needs tens of micro-seconds or even tens of milliseconds to synchronize with transmitted signals, known as timing acquisition problem. Such a long synchronization time will cause significant overhead, since the data rate of UWB systems is expected to be very high. In this paper, we address the timing acquisition problem at the medium access control (MAC) layer, and propose a general framework for medium access control in UWB systems; in this framework, a transmitting node can aggregate multiple upper-layer packets into a larger burst frame at the MAC layer. Furthermore, we design an MAC protocol based on the framework, and analyze its saturation throughput performance. Compared to sending each upper-layer packet individually, which is a typical situation in exiting MAC protocols, the proposed MAC can drastically reduce the synchronization overhead. Numerical and simulation results show that the proposed MAC can significantly improve the performance of UWB networks, in terms of both throughput and end-to-end delay

Performance of an Aggregation-Based MAC Protocol for High-Data-Rate Ultrawideband Ad Hoc

Abstract—Ultrawideband (UWB) communication is an emerging technology that promises to provide high data rate communication for wireless personal area networks. One of the critical challenges in UWB system design is the timing acquisition problem, i.e., a receiver needs a relative long time to synchronize with transmitted signals. Clearly, the timing acquisition overhead will significantly limit the throughput of high data rate UWB ad hoc networks. To resolve the timing acquisition problem, the authors proposed a general framework for medium access control (MAC) protocols in their previous work (K. Lu, D. Wu, and Y. Fang, “A novel framework for medium access control in ultra-wideband ad hoc networks, ” Dynamics of Continuous, Discrete and Impulsive Systems (Series B), vol. 12, no. 3, pp. 427–441, Jun. 2005); under the framework, a transmitting node can aggregate multiple upper layer packets into a burst frame at the MAC layer. In this paper, the authors propose an aggregation-based MAC protocol within the framework. Besides packet aggregation, they also design a novel retransmission scheme which is suitable for error-prone wireless environment, in which only the packets that encounter transmission errors will be retransmitted. To evaluate the performance of the protocol, they develop a three-dimensional Markov chain model for the saturated throughput performance. In addition, they also analyze the end-to-end delay performance through simulation. Extensive numerical and simulation results show that, compared to existing MAC protocols, in which upper layer packets are transmitted one by one, the proposed protocol can drastically reduce the timing acquisition overhead. Consequently, both the throughput and the end-to-end delay performance can be significantly improved. Index Terms—Bit error rate (BER), burst frame, delay, medium access control (MAC), throughput, timing acquisition, ultrawideband (UWB)