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Full-Text Articles in Computer Engineering

Joint Rate Control And Demand Balancing For Electric Vehicle Charging, Fanxin Kong, Xue Liu, Insup Lee Apr 2018

Joint Rate Control And Demand Balancing For Electric Vehicle Charging, Fanxin Kong, Xue Liu, Insup Lee

Departmental Papers (CIS)

Charging stations have become indispensable infrastructure to support the rapid proliferation of electric vehicles (EVs). The operational scheme of charging stations is crucial to satisfy the stability of the power grid and the quality of service (QoS) to EV users. Most existing schemes target either of the two major operations: charging rate control and demand balancing. This partial focus overlooks the coupling relation between the two operations and thus causes the degradation on the grid stability or customer QoS. A thoughtful scheme should manage both operations together. A big challenge to design such a scheme is the aggregated uncertainty caused ...


Attack-Resilient Sensor Fusion For Safety-Critical Cyber-Physical, Radoslav Ivanov, Miroslav Pajic, Insup Lee Feb 2016

Attack-Resilient Sensor Fusion For Safety-Critical Cyber-Physical, Radoslav Ivanov, Miroslav Pajic, Insup Lee

Departmental Papers (CIS)

This paper focuses on the design of safe and attack-resilient Cyber-Physical Systems (CPS) equipped with multiple sensors measuring the same physical variable. A malicious attacker may be able to disrupt system performance through compromising a subset of these sensors. Consequently, we develop a precise and resilient sensor fusion algorithm that combines the data received from all sensors by taking into account their specified precisions. In particular, we note that in the presence of a shared bus, in which messages are broadcast to all nodes in the network, the attacker’s impact depends on what sensors he has seen before sending ...


Attack-Resilient State Estimation In The Presence Of Noise, Miroslav Pajic, Paulo Tabuada, Insup Lee, George Pappas Dec 2015

Attack-Resilient State Estimation In The Presence Of Noise, Miroslav Pajic, Paulo Tabuada, Insup Lee, George Pappas

Departmental Papers (CIS)

We consider the problem of attack-resilient state estimation in the presence of noise. We focus on the most general model for sensor attacks where any signal can be injected via the compromised sensors. An l0-based state estimator that can be formulated as a mixed-integer linear program and its convex relaxation based on the l1 norm are presented. For both l0 and l1-based state estimators, we derive rigorous analytic bounds on the state-estimation errors. We show that the worst-case error is linear with the size of the noise, meaning that the attacker cannot exploit noise ...


Automatic Verification Of Linear Controller Software, Miroslav Pajic, Junkil Park, Insup Lee, George J. Pappas, Oleg Sokolsky Oct 2015

Automatic Verification Of Linear Controller Software, Miroslav Pajic, Junkil Park, Insup Lee, George J. Pappas, Oleg Sokolsky

Departmental Papers (CIS)

We consider the problem of verification of software implementations of linear time-invariant controllers. Commonly, different implementations use different representations of the controller’s state, for example due to optimizations in a third-party code generator. To accommodate this variation, we exploit input-output controller specification captured by the controller’s transfer function and show how to automatically verify correctness of C code controller implementations using a Frama-C/Why3/Z3 toolchain. Scalability of the approach is evaluated using randomly generated controller specifications of realistic size.


Robust Estimation Using Context-Aware Filtering, Radoslav Ivanov, Nikolay Atanasov, Miroslav Pajic, George Pappas, Insup Lee Sep 2015

Robust Estimation Using Context-Aware Filtering, Radoslav Ivanov, Nikolay Atanasov, Miroslav Pajic, George Pappas, Insup Lee

Departmental Papers (CIS)

This paper presents the context-aware filter, an estimation technique that incorporates context measurements, in addition to the regular continuous measurements. Context measurements provide binary information about the system’s context which is not directly encoded in the state; examples include a robot detecting a nearby building using image processing or a medical device alarming that a vital sign has exceeded a predefined threshold. These measurements can only be received from certain states and can therefore be modeled as a function of the system’s current state. We focus on two classes of functions describing the probability of context detection given ...


Robust Localization Using Context-Aware Filtering, Radoslav Ivanov, Nikolay Atanasov, Miroslav Pajic, Insup Lee, George Pappas Jul 2015

Robust Localization Using Context-Aware Filtering, Radoslav Ivanov, Nikolay Atanasov, Miroslav Pajic, Insup Lee, George Pappas

Departmental Papers (CIS)

In this paper we develop a robot localization technique that incorporates discrete context measurements, in addition to standard continuous state measurements. Context measurements provide binary information about detected events in the robot’s environment, e.g., a building is recognized using image processing or a known radio station is received. Such measurements can only be detected from certain positions and can, therefore, be correlated with the robot’s state. We investigate two specific examples where context measurements are especially useful – an urban localization scenario where GPS measurements are not reliable as well as the capture of the RQ-170 Sentinel drone ...


Towards Synthesis Of Platform-Aware Attack-Resilient Control Systems: Extended Abstract, Miroslav Pajic, Nicola Bezzo, James Weimer, Rajeev Alur, Rahul Mangharam, Nathan Michael, George Pappas, Oleg Sokolsky, Paulo Tabuada, Stephanie Weirich, Insup Lee Jun 2015

Towards Synthesis Of Platform-Aware Attack-Resilient Control Systems: Extended Abstract, Miroslav Pajic, Nicola Bezzo, James Weimer, Rajeev Alur, Rahul Mangharam, Nathan Michael, George Pappas, Oleg Sokolsky, Paulo Tabuada, Stephanie Weirich, Insup Lee

Stephanie Weirich

No abstract provided.


Verified Ros-Based Deployment Of Platform-Independent Control Systems, Wenrui Meng, Junkil Park, Oleg Sokolsky, Stephanie Weirich, Insup Lee Apr 2015

Verified Ros-Based Deployment Of Platform-Independent Control Systems, Wenrui Meng, Junkil Park, Oleg Sokolsky, Stephanie Weirich, Insup Lee

Departmental Papers (CIS)

The paper considers the problem of model-based deployment of platform-independent control code on a specific platform. The approach is based on automatic generation of platform-specific glue code from an architectural model of the system. We present a tool, ROSGen, that generates the glue code based on a declarative specification of platform interfaces. Our implementation targets the popular Robot Operating System (ROS) platform. We demonstrate that the code generation process is amenable to formal verification. The code generator is implemented in Coq and relies on the infrastructure provided by the CompCert and VST tool. We prove that the generated code always ...


Controller Synthesis For Autonomous Systems Interacting With Human Operators, Lu Feng, Clemens Wiltsche, Laura Humphrey, Ufuk Topcu Apr 2015

Controller Synthesis For Autonomous Systems Interacting With Human Operators, Lu Feng, Clemens Wiltsche, Laura Humphrey, Ufuk Topcu

Departmental Papers (CIS)

We propose an approach to synthesize control protocols for autonomous systems that account for uncertainties and imperfections in interactions with human operators. As an illustrative example, we consider a scenario involving road network surveillance by an unmanned aerial vehicle (UAV) that is controlled remotely by a human operator but also has a certain degree of autonomy. Depending on the type (i.e., probabilistic and/or nondeterministic) of knowledge about the uncertainties and imperfections in the operatorautonomy interactions, we use abstractions based on Markov decision processes and augment these models to stochastic two-player games. Our approach enables the synthesis of operator-dependent ...


Architecture-Centric Software Development For Cyber-Physical Systems, Oleg Sokolsky, Miroslav Pajic, Nicola Bezzo, Insup Lee Oct 2014

Architecture-Centric Software Development For Cyber-Physical Systems, Oleg Sokolsky, Miroslav Pajic, Nicola Bezzo, Insup Lee

Departmental Papers (CIS)

We discuss the problem of high-assurance development of cyber-physical systems. Specifically, we concentrate on the interaction between the development of the control system layer and platform-specific software engineering for system components. We argue that an architecture-centric approach allows us to streamline the development and increase the level of assurance for the resulting system. The case study of an unmanned ground vehicle illustrates the approach.


Towards Assurance Cases For Resilient Control Systems, James Weimer, Oleg Sokolsky, Nicola Bezzo, Insup Lee Aug 2014

Towards Assurance Cases For Resilient Control Systems, James Weimer, Oleg Sokolsky, Nicola Bezzo, Insup Lee

Departmental Papers (CIS)

The paper studies the problem of constructing assurance cases for embedded control systems developed using a model-based approach. Assurance cases aim to provide a convincing argument that the system delivers certain guarantees, based on the evidence obtained during the design and evaluation of the system. We suggest an argument strategy centered around properties of models used in the development and properties of tools that manipulate these models. The paper presents the case study of a resilient speed estimator for an autonomous ground vehicle and takes the reader through a detailed assurance case arguing that the estimator computes speed estimates with ...


Attack-Resilient Minimum Mean-Squared Error Estimation, James Weimer, Nicola Bezzo, Miroslav Pajic, Oleg Sokolsky, Insup Lee Jun 2014

Attack-Resilient Minimum Mean-Squared Error Estimation, James Weimer, Nicola Bezzo, Miroslav Pajic, Oleg Sokolsky, Insup Lee

Departmental Papers (CIS)

This work addresses the design of resilient estimators for stochastic systems. To this end, we introduce a minimum mean-squared error resilient (MMSE-R) estimator whose conditional mean squared error from the state remains finitely bounded and is independent of additive measurement attacks. An implementation of the MMSE-R estimator is presented and is shown as the solution of a semidefinite programming problem, which can be implemented efficiently using convex optimization techniques. The MMSE-R strategy is evaluated against other competing strategies representing other estimation approaches in the presence of small and large measurement attacks. The results indicate that the MMSE-R estimator significantly outperforms ...


Robustness Of Attack-Resilient State Estimators, Miroslav Pajic, James Weimer, Nicola Bezzo, Paulo Tabuada, Oleg Sokolsky, Insup Lee, George Pappas Apr 2014

Robustness Of Attack-Resilient State Estimators, Miroslav Pajic, James Weimer, Nicola Bezzo, Paulo Tabuada, Oleg Sokolsky, Insup Lee, George Pappas

Departmental Papers (CIS)

The interaction between information technology and physical 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 difeerence between the model used for the ...


Resilient Multidimensional Sensor Fusion Using Measurement History, Radoslav Ivanov, Miroslav Pajic, Insup Lee Feb 2014

Resilient Multidimensional Sensor Fusion Using Measurement History, Radoslav Ivanov, Miroslav Pajic, Insup Lee

Departmental Papers (CIS)

This work considers the problem of performing resilient sensor fusion using past sensor measurements. In particular, we consider a system with n sensors measuring the same physical variable where some sensors might be attacked or faulty. We consider a setup in which each sensor provides the controller with a set of possible values for the true value. Here, more precise sensors provide smaller sets. Since a lot of modern sensors provide multidimensional measurements (e.g., position in three dimensions), the sets considered in this work are multidimensional polyhedra.

Given the assumption that some sensors can be attacked or faulty, the ...


Attack-Resilient Sensor Fusion, Radoslav Ivanov, Miroslav Pajic, Insup Lee Feb 2014

Attack-Resilient Sensor Fusion, Radoslav Ivanov, Miroslav Pajic, Insup Lee

Departmental Papers (CIS)

This work considers the problem of attack-resilient sensor fusion in an autonomous system where multiple sensors measure the same physical variable. A malicious attacker may corrupt a subset of these sensors and send wrong measurements to the controller on their behalf, potentially compromising the safety of the system. We formalize the goals and constraints of such an attacker who also wants to avoid detection by the system. We argue that the attacker’s capabilities depend on the amount of information she has about the correct sensors’ measurements. In the presence of a shared bus where messages are broadcast to all ...


Towards Synthesis Of Platform-Aware Attack-Resilient Control Systems: Extended Abstract, Miroslav Pajic, Nicola Bezzo, James Weimer, Rajeev Alur, Rahul Mangharam, Nathan Michael, George J. Pappas, Oleg Sokolsky, Paulo Tabuada, Stephanie Weirich, Insup Lee Apr 2013

Towards Synthesis Of Platform-Aware Attack-Resilient Control Systems: Extended Abstract, Miroslav Pajic, Nicola Bezzo, James Weimer, Rajeev Alur, Rahul Mangharam, Nathan Michael, George J. Pappas, Oleg Sokolsky, Paulo Tabuada, Stephanie Weirich, Insup Lee

Departmental Papers (CIS)

No abstract provided.


Hmm-Based Characterization Of Channel Behavior For Networked Control Systems, Jian Chang, Krishna K. Venkatasubramanian, Chinwendu Enyioha, Shreyas Sundaram, George J. Pappas, Insup Lee Apr 2012

Hmm-Based Characterization Of Channel Behavior For Networked Control Systems, Jian Chang, Krishna K. Venkatasubramanian, Chinwendu Enyioha, Shreyas Sundaram, George J. Pappas, Insup Lee

Departmental Papers (CIS)

We study the problem of characterizing the behavior of lossy and data corrupting communication channels in a networked control setting, where the channel's behavior exhibits temporal correlation. We propose a behavior characterization mechanism based on a hidden Markov model (HMM). The use of a HMM in this regard presents multiple challenges including dealing with incomplete observation sequences (due to data losses and corruptions) and the lack of a priori information about the model complexity (number of states in the model). We address the first challenges by using the plant state information and history of received/applied control inputs to ...