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Articles 1 - 30 of 55
Full-Text Articles in Engineering
Adaptive Algorithms For Coverage Control And Space Partitioning In Mobile Robotic Networks, Jerome Le Ny, George J. Pappas
Adaptive Algorithms For Coverage Control And Space Partitioning In Mobile Robotic Networks, Jerome Le Ny, George J. Pappas
George J. Pappas
We consider deployment problems where a mobile robotic network must optimize its configuration in a distributed way in order to minimize a steady-state cost function that depends on the spatial distribution of certain probabilistic events of interest. Three classes of problems are discussed in detail: coverage control problems, spatial partitioning problems, and dynamic vehicle routing problems. Moreover, we assume that the event distribution is a priori unknown, and can only be progressively inferred from the observation of the location of the actual event occurrences. For each problem we present distributed stochastic gradient algorithms that optimize the performance objective. The stochastic …
Geometric Programming And Mechanism Design For Air Traffic Conflict Resolution, Jerome Le Ny, George J. Pappas
Geometric Programming And Mechanism Design For Air Traffic Conflict Resolution, Jerome Le Ny, George J. Pappas
George J. Pappas
We develop certain extensions of optimization based conflict resolution methods in air traffic control. The problem considered concerns the scheduling of the crossing times of a set of aircraft through a metering fix, while maintaining aircraft separation. First, we show how to solve this combined path planning and scheduling problem using mixed integer geometric programming. Second, the objective function used to determine the aircraft ordering at the fix is not given a priori but needs to be obtained from the airlines, which are strategic profit maximizing agents and could lie about their true cost. In order to realign individual and …
Temporal Logic Motion Planning For Mobile Robots, Geogios E. Fainekos, Hadas Kress-Gazit, George J. Pappas
Temporal Logic Motion Planning For Mobile Robots, Geogios E. Fainekos, Hadas Kress-Gazit, George J. Pappas
George J. Pappas
In this paper, we consider the problem of robot motion planning in order to satisfy formulas expressible in temporal logics. Temporal logics naturally express traditional robot specifications such as reaching a goal or avoiding an obstacle, but also more sophisticated specifications such as sequencing, coverage, or temporal ordering of different tasks. In order to provide computational solutions to this problem, we first construct discrete abstractions of robot motion based on some environmental decomposition. We then generate discrete plans satisfying the temporal logic formula using powerful model checking tools, and finally translate the discrete plans to continuous trajectories using hybrid control. …
On The Feasibility Of Linear Discrete-Time Systems Of The Green Scheduling Problem, Zheng Li, Pei-Chi Huang, Aloysius K. Mok, Truong Nghiem, Madhur Behl, George Pappas, Rahul Mangharam
On The Feasibility Of Linear Discrete-Time Systems Of The Green Scheduling Problem, Zheng Li, Pei-Chi Huang, Aloysius K. Mok, Truong Nghiem, Madhur Behl, George Pappas, Rahul Mangharam
George J. Pappas
Peak power consumption of buildings in large facilities like hospitals and universities becomes a big issue because peak prices are much higher than normal rates. During a power demand surge an automated power controller of a building may need to schedule ON and OFF different environment actuators such as heaters and air quality control while maintaining the state variables such as temperature or air quality of any room within comfortable ranges. The green scheduling problem asks whether a scheduling policy is possible for a system and what is the necessary and sufficient condition for systems to be feasible. In this …
Joint Metering And Conflict Resolution In Air Traffic Control, Jerome Le Ny, George J. Pappas
Joint Metering And Conflict Resolution In Air Traffic Control, Jerome Le Ny, George J. Pappas
George J. Pappas
This paper describes a novel optimization-based approach to conflict resolution in air traffic control, based on geometric programming. The main advantage of the approach is that Geometric Programs (GPs) can also capture various metering directives issued by the traffic flow management level, in contrast to most recent methods focusing purely on aircraft separation issues. GPs can also account for some of the nonlinearities present in the formulations of conflict resolution problems, while incurring only a small penalty in computation time with respect to the fastest linear programming based approaches. Additional integer variables can be introduced to improve the quality of …
Modeling And Analyzing Biomolecular Networks, Rajeev Alur, Calin Belta, Vijay Kumar, Max Mintz, George J. Pappas, Harvey Rubin, Jonathan Schug
Modeling And Analyzing Biomolecular Networks, Rajeev Alur, Calin Belta, Vijay Kumar, Max Mintz, George J. Pappas, Harvey Rubin, Jonathan Schug
George J. Pappas
The authors argue for the need to model and analyze biological networks at molecular and cellular levels. They propose a computational toolbox for biologists. Central to their approach is the paradigm of hybrid models in which discrete events are combined with continuous differential equations to capture switching behavior.
Adaptive Robot Deployment Algorithms, Jerome Le Ny, George J. Pappas
Adaptive Robot Deployment Algorithms, Jerome Le Ny, George J. Pappas
George J. Pappas
In robot deployment problems, the fundamental issue is to optimize a steady state performance measure that depends on the spatial configuration of a group of robots. For static deployment problems, a classical way of designing high- level feedback motion planners is to implement a gradient descent scheme on a suitably chosen objective function. This can lead to computationally expensive deployment algorithms that may not be adaptive to uncertain dynamic environments. We address this challenge by showing that algorithms for a variety of deployment scenarios in stochastic environments and with noisy sensor measurements can be designed as stochastic gradient descent algorithms, …
The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos N. Hadjicostis, Rahul Mangharam, George J. Pappas
The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos N. Hadjicostis, Rahul Mangharam, George J. Pappas
George J. Pappas
We consider the problem of stabilizing a plant with a network of resource constrained wireless nodes. In a companion paper, we developed a protocol where each node repeatedly transmits a linear combination of the values in its neighborhood. For certain topologies, we showed that these linear combinations can be designed so that the closed loop system is stable (i.e., the wireless network itself acts as a controller for the plant). In this paper, we design a Intrusion Detection System (IDS) for this control scheme, which observes the transmissions of certain nodes in the network and uses that information to (a) …
Controlling Connectivity Of Dynamic Graphs, Michael M. Zavlanos, George J. Pappas
Controlling Connectivity Of Dynamic Graphs, Michael M. Zavlanos, George J. Pappas
George J. Pappas
The control of mobile networks of multiple agents raises fundamental and novel problems in controlling the structure of the resulting dynamic graphs. In this paper, we consider the problem of controlling a network of agents so that the resulting motion always preserves various connectivity properties. In particular, we consider preserving k-hop connectivity, where agents are allowed to move while maintaining connections to agents that are no more than k-hops away. The connectivity constraint is translated to constrains on individual agent motion by considering the dynamics of the adjacency matrix and related constructs from algebraic graph theory. As special cases, we …
Topological Conditions For Wireless Control Networks, Miroslav Pajic, Shreyas Sundaram, George J. Pappas, Rahul Mangharam
Topological Conditions For Wireless Control Networks, Miroslav Pajic, Shreyas Sundaram, George J. Pappas, Rahul Mangharam
George J. Pappas
We study the problem of stabilizing a linear system over a wireless control network. We propose a scheme where each wireless node maintains a scalar state, and periodically updates it as a linear combination of neighboring plant outputs and node states. We make connections to decentralized fixed modes and structured system theory to provide conditions on the network topology that allow the system to be stabilized. Our analysis provides the minimal number of feedback edges that have to be introduced to stabilize the system over a network, and shows that as long as the network connectivity is larger than the …
Network Synthesis For Dynamical System Stabilization, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
Network Synthesis For Dynamical System Stabilization, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
George J. Pappas
We present our recent results in the area of distributed control over wireless networks. In our previous work, we introduced the concept of a Wireless Control Network (WCN), where the network acts as a decentralized structured controller. In this case, the network is not used only as a communication medium (as in traditional control paradigms), but instead as a fully distributed computational substrate. We show that the dynamics of the plant dictate the types of network topologies that can be used to stabilize the system. Finally, we describe how to obtain a stabilizing configuration for the WCN if the topological …
Cooperative Air And Ground Survaillance, Ben Grocholsky, James Keller, Vijay Kumar, George J. Pappas
Cooperative Air And Ground Survaillance, Ben Grocholsky, James Keller, Vijay Kumar, George J. Pappas
George J. Pappas
Unmanned aerial vehicles (UAVs) can be used to cover large areas searching for targets. However, sensors on UAVs are typically limited in their accuracy of localization of targets on the ground. On the other hand, unmanned ground vehicles (UGVs) can be deployed to accurately locate ground targets, but they have the disadvantage of not being able to move rapidly or see through such obstacles as buildings or fences. In this article, we describe how we can exploit this synergy by creating a seamless network of UAVs and UGVs. The keys to this are our framework and algorithms for search and …
Optimal Paths In Weighted Timed Automata, Rajeev Alur, Salvatore La Torre, George J. Pappas
Optimal Paths In Weighted Timed Automata, Rajeev Alur, Salvatore La Torre, George J. Pappas
George J. Pappas
We consider the optimal-reachability problem for a timed automaton with respect to a linear cost function which results in a weighted timed automaton. Our solution to this optimization problem consists of reducing it to computing (parametric) shortest paths in a finite weighted directed graph. We call this graph a parametric sub-region graph. It refines the region graph, a standard tool for the analysis of timed automata, by adding the information which is relevant to solving the optimal-reachability problem. We present an algorithm to solve the optimal-reachability problem for weighted timed automata that takes time exponential in O(n (|δ(A)|+|wmax|)), where n …
A Simple Distributed Method For Control Over Wireless Networks, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
A Simple Distributed Method For Control Over Wireless Networks, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
George J. Pappas
We present a distributed scheme used for control over wireless networks. In our previous work, we introduced the concept of a Wireless Control Network (WCN), where the network itself, with no centralized node, acts as the controller. In this work, we show how the WCN can be modified to include observer style updates which substantially improves robustness of the closed-loop system to link failures. In addition, we analyze how the WCN simplifies extraction of the communication and computation schedules and enables system compositionality and scalability.
Hybrid Controllers For Path Planning: A Temporal Logic Approach, Geogios E. Fainekos, Hadas Kress-Gazit, George J. Pappas
Hybrid Controllers For Path Planning: A Temporal Logic Approach, Geogios E. Fainekos, Hadas Kress-Gazit, George J. Pappas
George J. Pappas
Robot motion planning algorithms have focused on low-level reachability goals taking into account robot kinematics, or on high level task planning while ignoring low-level dynamics. In this paper, we present an integrated approach to the design of closed–loop hybrid controllers that guarantee by construction that the resulting continuous robot trajectories satisfy sophisticated specifications expressed in the so–called Linear Temporal Logic. In addition, our framework ensures that the temporal logic specification is satisfied even in the presence of an adversary that may instantaneously reposition the robot within the environment a finite number of times. This is achieved by obtaining a Büchi …
The Wireless Control Network: Synthesis And Robustness, Miroslav Pajic, Shreyas Sundaram, Jerome Le Ny, George J. Pappas, Rahul Mangharam
The Wireless Control Network: Synthesis And Robustness, Miroslav Pajic, Shreyas Sundaram, Jerome Le Ny, George J. Pappas, Rahul Mangharam
George J. Pappas
We consider the problem of stabilizing a plant with a network of resource constrained wireless nodes. Traditional networked control schemes are designed with one of the nodes in the network acting as a dedicated controller, while the other nodes simply route information to and from the controller and the plant. We introduce the concept of a Wireless Control Network (WCN) where the entire network itself acts as the controller. Specifically, at each time-step, each node updates its internal state to be a linear combination of the states of the nodes in its neighborhood. We show that this causes the entire …
The Wireless Control Network: A New Approach For Control Over Networks, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
The Wireless Control Network: A New Approach For Control Over Networks, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
George J. Pappas
We present a method to stabilize a plant with a network of resource constrained wireless nodes. As opposed to traditional networked control schemes where the nodes simply route information to and from a dedicated controller (perhaps performing some encoding along the way), our approach treats the network itself as the controller. Specifically, we formulate a strategy for each node in the network to follow, where at each time-step, each node updates its internal state to be a linear combination of the states of the nodes in its neighborhood. We show that this causes the entire network to behave as a …
Adaptive Algorithms For Coverage Control And Space Partitioning In Mobile Robotic Networks, Jerome Le Ny, George J. Pappas
Adaptive Algorithms For Coverage Control And Space Partitioning In Mobile Robotic Networks, Jerome Le Ny, George J. Pappas
George J. Pappas
We consider deployment problems where a mobile robotic network must optimize its configuration in a distributed way in order to minimize a steady-state cost function that depends on the spatial distribution of certain probabilistic events of interest. Three classes of problems are discussed in detail: coverage control problems, spatial partitioning problems, and dynamic vehicle routing problems. Moreover, we assume that the event distribution is a priori unknown, and can only be progressively inferred from the observation of the location of the actual event occurrences. For each problem we present distributed stochastic gradient algorithms that optimize the performance objective. The stochastic …
Geometric Programming And Mechanism Design For Air Traffic Conflict Resolution, Jerome Le Ny, George J. Pappas
Geometric Programming And Mechanism Design For Air Traffic Conflict Resolution, Jerome Le Ny, George J. Pappas
George J. Pappas
We develop certain extensions of optimization based conflict resolution methods in air traffic control. The problem considered concerns the scheduling of the crossing times of a set of aircraft through a metering fix, while maintaining aircraft separation. First, we show how to solve this combined path planning and scheduling problem using mixed integer geometric programming. Second, the objective function used to determine the aircraft ordering at the fix is not given a priori but needs to be obtained from the airlines, which are strategic profit maximizing agents and could lie about their true cost. In order to realign individual and …
Temporal Logic Motion Planning For Mobile Robots, Geogios E. Fainekos, Hadas Kress-Gazit, George J. Pappas
Temporal Logic Motion Planning For Mobile Robots, Geogios E. Fainekos, Hadas Kress-Gazit, George J. Pappas
George J. Pappas
In this paper, we consider the problem of robot motion planning in order to satisfy formulas expressible in temporal logics. Temporal logics naturally express traditional robot specifications such as reaching a goal or avoiding an obstacle, but also more sophisticated specifications such as sequencing, coverage, or temporal ordering of different tasks. In order to provide computational solutions to this problem, we first construct discrete abstractions of robot motion based on some environmental decomposition. We then generate discrete plans satisfying the temporal logic formula using powerful model checking tools, and finally translate the discrete plans to continuous trajectories using hybrid control. …
Joint Metering And Conflict Resolution In Air Traffic Control, Jerome Le Ny, George J. Pappas
Joint Metering And Conflict Resolution In Air Traffic Control, Jerome Le Ny, George J. Pappas
George J. Pappas
This paper describes a novel optimization-based approach to conflict resolution in air traffic control, based on geometric programming. The main advantage of the approach is that Geometric Programs (GPs) can also capture various metering directives issued by the traffic flow management level, in contrast to most recent methods focusing purely on aircraft separation issues. GPs can also account for some of the nonlinearities present in the formulations of conflict resolution problems, while incurring only a small penalty in computation time with respect to the fastest linear programming based approaches. Additional integer variables can be introduced to improve the quality of …
Modeling And Analyzing Biomolecular Networks, Rajeev Alur, Calin Belta, Vijay Kumar, Max Mintz, George J. Pappas, Harvey Rubin, Jonathan Schug
Modeling And Analyzing Biomolecular Networks, Rajeev Alur, Calin Belta, Vijay Kumar, Max Mintz, George J. Pappas, Harvey Rubin, Jonathan Schug
George J. Pappas
The authors argue for the need to model and analyze biological networks at molecular and cellular levels. They propose a computational toolbox for biologists. Central to their approach is the paradigm of hybrid models in which discrete events are combined with continuous differential equations to capture switching behavior.
Adaptive Robot Deployment Algorithms, Jerome Le Ny, George J. Pappas
Adaptive Robot Deployment Algorithms, Jerome Le Ny, George J. Pappas
George J. Pappas
In robot deployment problems, the fundamental issue is to optimize a steady state performance measure that depends on the spatial configuration of a group of robots. For static deployment problems, a classical way of designing high- level feedback motion planners is to implement a gradient descent scheme on a suitably chosen objective function. This can lead to computationally expensive deployment algorithms that may not be adaptive to uncertain dynamic environments. We address this challenge by showing that algorithms for a variety of deployment scenarios in stochastic environments and with noisy sensor measurements can be designed as stochastic gradient descent algorithms, …
The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos N. Hadjicostis, Rahul Mangharam, George J. Pappas
The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos N. Hadjicostis, Rahul Mangharam, George J. Pappas
George J. Pappas
We consider the problem of stabilizing a plant with a network of resource constrained wireless nodes. In a companion paper, we developed a protocol where each node repeatedly transmits a linear combination of the values in its neighborhood. For certain topologies, we showed that these linear combinations can be designed so that the closed loop system is stable (i.e., the wireless network itself acts as a controller for the plant). In this paper, we design a Intrusion Detection System (IDS) for this control scheme, which observes the transmissions of certain nodes in the network and uses that information to (a) …
Controlling Biological Systems: The Lactose Regulation System Of Escherichia Coli, Anak Agung Julius, Ádam Halasz, Vijay Kumar, George Pappas
Controlling Biological Systems: The Lactose Regulation System Of Escherichia Coli, Anak Agung Julius, Ádam Halasz, Vijay Kumar, George Pappas
George J. Pappas
In this paper we present a comprehensive framework for abstraction and controller design for a biological system. The first half of the paper concerns modeling and model abstraction of the system. Most models in systems biology are deterministic models with ordinary differential equations in the concentration variables. We present a stochastic hybrid model of the lactose regulation system of E. coli bacteria that capture important phenomena which cannot be described by continuous deterministic models. We then show that the resulting stochastic hybrid model can be abstracted into a much simpler model, a two-state continuous time Markov chain. The second half …
Single Cell Manipulation Using Ferromagnetic Composite Microtransporters, Mahmut Selman Sakar, Edward B. Steager, Dal Hyung Kim, Min Jun Kim, George J. Pappas, Vijay Kumar
Single Cell Manipulation Using Ferromagnetic Composite Microtransporters, Mahmut Selman Sakar, Edward B. Steager, Dal Hyung Kim, Min Jun Kim, George J. Pappas, Vijay Kumar
George J. Pappas
For biomedical applications, such as single cell manipulation, it is important to fabricate microstructures that can be powered and controlled wirelessly in fluidic environments. In this letter, we describe the construction and operation of truly micron-sized, biocompatible ferromagnetic microtransporters driven by external magnetic fields. Microtransporters were fabricated using a simple, single step fabrication method and can be produced in large numbers. We demonstrate that they can be navigated to manipulate single cells with micron-size precision without disturbing the local environment.
Topological Conditions For Wireless Control Networks, Miroslav Pajic, Shreyas Sundaram, George J. Pappas, Rahul Mangharam
Topological Conditions For Wireless Control Networks, Miroslav Pajic, Shreyas Sundaram, George J. Pappas, Rahul Mangharam
George J. Pappas
We study the problem of stabilizing a linear system over a wireless control network. We propose a scheme where each wireless node maintains a scalar state, and periodically updates it as a linear combination of neighboring plant outputs and node states. We make connections to decentralized fixed modes and structured system theory to provide conditions on the network topology that allow the system to be stabilized. Our analysis provides the minimal number of feedback edges that have to be introduced to stabilize the system over a network, and shows that as long as the network connectivity is larger than the …
Modeling And Analysis Of Multi-Hop Control Networks, Alur Rajeev, Alessandro D'Innocenzo, Karl H. Johansson, George James Pappas, Gera Weiss
Modeling And Analysis Of Multi-Hop Control Networks, Alur Rajeev, Alessandro D'Innocenzo, Karl H. Johansson, George James Pappas, Gera Weiss
George J. Pappas
We propose a mathematical framework, inspired by the Wireless HART specification, for modeling and analyzing multi-hop communication networks. The framework is designed for systems consisting of multiple control loops closed over a multi-hop communication network. We separate control, topology, routing, and scheduling and propose formal syntax and semantics for the dynamics of the composed system. The main technical contribution of the paper is an explicit translation of multi-hop control networks to switched systems. We describe a Mathematica notebook that automates the translation of multihop control networks to switched systems, and use this tool to show how techniques for analysis of …
Network Synthesis For Dynamical System Stabilization, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
Network Synthesis For Dynamical System Stabilization, Miroslav Pajic, Shreyas Sundaram, George Pappas, Rahul Mangharam
George J. Pappas
We present our recent results in the area of distributed control over wireless networks. In our previous work, we introduced the concept of a Wireless Control Network (WCN), where the network acts as a decentralized structured controller. In this case, the network is not used only as a communication medium (as in traditional control paradigms), but instead as a fully distributed computational substrate. We show that the dynamics of the plant dictate the types of network topologies that can be used to stabilize the system. Finally, we describe how to obtain a stabilizing configuration for the WCN if the topological …
Cooperative Air And Ground Survaillance, Ben Grocholsky, James Keller, Vijay Kumar, George J. Pappas
Cooperative Air And Ground Survaillance, Ben Grocholsky, James Keller, Vijay Kumar, George J. Pappas
George J. Pappas
Unmanned aerial vehicles (UAVs) can be used to cover large areas searching for targets. However, sensors on UAVs are typically limited in their accuracy of localization of targets on the ground. On the other hand, unmanned ground vehicles (UGVs) can be deployed to accurately locate ground targets, but they have the disadvantage of not being able to move rapidly or see through such obstacles as buildings or fences. In this article, we describe how we can exploit this synergy by creating a seamless network of UAVs and UGVs. The keys to this are our framework and algorithms for search and …