Nicola Bezzo

Robustness of Attack-Resilient State Estimators

The interaction between information technology and phys ical world makes Cyber-Physical Systems (CPS) vulnerable to malicious attacks beyond the standard cyber attacks. This has motivated the need for attack-resilient state estimation. Yet, the existing state-estimators are based on the non-realistic assumption that the exact system model is known. Consequently, in this work we present a method for state estimation in presence of attacks, for systems with noise and modeling errors. When the the estimated states are used by a state-based feedback controller, we show that the attacker cannot destabilize the system by exploiting the difference between the model used for the state estimation and the real physical dynamics of the system. Furthermore, we describe how implementation issues such as jitter, latency and synchronization errors can be mapped into parameters of the state estimation procedure that describe modeling errors, and provide a bound on the state-estimation error caused by modeling errors. This enables mapping control performance requirements into real-time (i.e., timing related) specifications imposed on the underlying platform. Finally, we illustrate and experimentally evaluate this approach on an unmanned ground vehicle case-study.

A Cooperative Heterogeneous Mobile Wireless Mechatronic System

This paper describes a framework for controlling a heterogeneous wireless robotic network consisting of aerial and ground vehicles. By use of the term heterogeneous, we imply the synergy of multiple robotic platforms characterized by different dynamics and specialized sensing capabilities. Two main scenarios concerning wireless communications are presented: 1) a decentralized connectivity strategy in which a mesh of ground mobile routers swarms in a cluttered environment maintaining communication constraints based on spring-mass virtual physics, potential functions, and routing optimization and 2) an autonomous communications relay in GPS-denied environments via antenna diversity and extremum-seeking SNR optimization. For both scenarios, we validate the proposed methodologies by numerical simulations and experiments. One important feature of our test bed is that it can be used for both indoor and outdoor operations.

Attack resilient state estimation for autonomous robotic systems

In this paper we present a methodology to control ground robots under malicious attack on sensors. Within the term attack we intend any malicious disturbance injection on sensors, actuators, and controller that would compromise the safety of a robot. In order to guarantee resilience against attacks, we use a control-level technique implemented within a recursive algorithm that takes advantage of redundancy in the information received by the controller. We use the case study of a vehicle cruise-control, however, the strategy we present in this work is general for several applications. Our methodology relays on redundancy in the sensor measurements: specifically we consider N velocity measurements and use a recursive filtering technique that estimates the state of the system while being resilient against sensor attacks by acting on the variance of the measurements noise. Finally, we move our focus on hardware validation demonstrating our algorithm through extensive outdoor experiments conducted on two unmanned ground robots.

A DISJUNCTIVE PROGRAMMING APPROACH FOR MOTION PLANNING OF MOBILE ROUTER NETWORKS

In this paper we develop a framework based on disjunctive programming for motion planning of robotic networks. Although the methodology presented in this paper can be applied to general motion planning problems we focus on coordinating a team of mobile routers to maintain connectivity between a fixed base station and a mobile user within a walled environment. This connectivity management problem is decomposed into three steps: (i) a feasible line-of-sight path between the base station and the mobile user is computed; (ii) the number of required routers and their goal locations are determined; and (iii) the motion planning with obstacle and inter-vehicle collision avoidance problem is solved. To illustrate the flexibility of the proposed approach we also formulate a novel motion planning algorithm for a team of mobile robots as a disjunctive program. Cell decomposition is used to take into account the size and orientation of the robots. In both cases, connectivity and motion planning, the mixed-integer optimization problems are solve using CPLEX. Moreover, the proposed approach can easily accommodate input and other constraints and mission objectives. Simulation results show the applicability of the proposed strategy.

A Decentralized Connectivity Strategy for Mobile Router Swarms

Abstract In this paper we create a mesh of mobile robots that move in a decentralized fashion (swarming) in a two-dimensional space while maintaining communication constraints. The motion of the agents is dictated by four factors: i) a spring-mass interaction between agents; ii) a repulsive force from the obstacles; iii) an attractive force from the base station; and iv) an attractive field to regions with high probability to find users. Dijkstras algorithm is implemented for optimal routing and a Bit Error Rate minimization is performed for communication optimization. The network is seen as a switched system in which virtual springs interactions create and delete the sensing links between agents. Stability analysis in the sense of Lyapunov is presented. Simulation results validate the applicability of the proposed method.

Tethering of mobile router networks

In this paper we develop a framework based on disjunctive programming for motion planning of mobile routers. Although the methodology presented in this paper can be applied to general motion planning problems we focus on coordinating a team of mobile routers to maintain connectivity between a fixed base station and a mobile user within a walled environment. This connectivity management problem is decomposed into three phases: (i) computing a feasible line-of- sight path between the base station and the mobile user; (ii) determining the number of required routers and their goal locations; and (iii) solving the motion planning with obstacle and inter-vehicle collision avoidance problem. The optimization problems are solved using CPLEX. Simulation results show the applicability of the proposed strategy.

A Design Environment for the Rapid Specification and Fabrication of Printable Robots

In this work, we have developed a design environment to allow casual users to quickly and easily create custom robots. A drag-and-drop graphical interface allows users to intuitively assemble electromechanical systems from a library of predesigned parametrized components. A script-based infrastructure encapsulates and automatically composes mechanical, electrical, and software subsystems based on the user input. The generated design can be passed through output plugins to produce fabrication drawings for a range of rapid manufacturing processes, along with the necessary firmware and software to control the device. From an intuitive description of the desired specification, this system generates ready-to-use printable robots on demand.

Decentralized identification and control of networks of coupled mobile platforms through adaptive synchronization of chaos

Abstract In this paper, we propose an application of adaptive synchronization of chaos to detect changes in the topology of a mobile robotic network. We assume that the network may evolve in time due to the relative motion of the mobile robots and due to unknown environmental conditions, such as the presence of obstacles in the environment. We consider that each robotic agent is equipped with a chaotic oscillator whose state is propagated to the other robots through wireless communication, with the goal of synchronizing the oscillators. We introduce an adaptive strategy that each agent independently implements to: (i) estimate the net coupling of all the oscillators in its neighborhood and (ii) synchronize the state of the oscillators onto the same time evolution. We show that, by using this strategy, synchronization can be attained and changes in the network topology can be detected. We further consider the possibility of using this information to control the mobile network. We apply our technique to the problem of maintaining a formation between a set of mobile platforms which operate in an inhomogeneous and uncertain environment. We discuss the importance of using chaotic oscillators, and validate our methodology by numerical simulations.

Demo Abstract: ROSLab --- A Modular Programming Environment for Robotic Applications

We propose a simplified high-level programming language based on blocks and links dragged on a workspace which generates the skeleton code for robotic applications involving different types of robots. In order to develop such a high-level programming language that still can guarantee flexibility in term of implementation, our approach takes advantage of the robot operating system (ROS). ROS is a open source meta-operating system that provides a message passing structure between different processes (or nodes) across a network (inter-process communication). In our framework, we consider a hierarchical approach in which at the base there is ROS that allows inter-process communication between nodes in a robot and on the top we create a high-level language that interacts with ROS and thus with the real robot. The high-level language can be viewed as an extra layer added to simplify lower level code generation.

Robot Makers: The Future of Digital Rapid Design and Fabrication of Robots

Robots are complex systems, and their design requires detailed knowledge of diverse fields, including mechanics, electronics, software, and control theory. Thus, our ability to rapidly create robotic systems requires a synergy between these diverse disciplines. In the near future, new paradigms and tools will be needed for on-demand design generation; new fabrication methods will be needed to realize custom electromechanical devices; and new algorithms and programming languages will be necessary to define, evaluate, and optimize behavioral specifications and designs. In this article, we assess the main challenges, problems, vision, and future steps on the topic of codesign and rapid fabrication of robotic systems.