Microsoft Word - JournalReviewMorteza.docx

We study an important class of feedback controllers that arise in curve tracking problems for robotics. Previous experimental results suggested the robust performance of the control laws under perturbations. Here we use input‐to‐state stability to prove predictable tolerance and safety bounds that ensure robust performance under perturbations and time delays. Our proofs are based on an invariant polygon argument and a new strict Lyapunov function design. May 2012, Volume: 57 Issue:5 , page(s): 1265 ‐ 1269 Verification of Infinite-Step Opacity and Complexity Considerations Saboori, A.; Hadjicostis, C. N. Microsoft Abstract We describe and analyze the complexity of verifying the notion of infinite‐step opacity in systems that are modeled as non‐deterministic finite automata with partial observation on their transitions. Specifically, a system is infinite‐step opaque if the entrance of the system state, at any particular instant, to a set of secret states remains opaque (uncertain), for the length of the system operation, to an intruder who observes system activity through some projection map. Infinite‐step opacity can be used to characterize the security requirements in many applications, including encryption using pseudo‐ random generators, coverage properties in sensor networks, and anonymity requirements in protocols for web transactions. We show that infinite‐step opacity can be verified via the construction of a set of appropriate initial state estimators and provide illustrative examples. We also establish that the verification of infinite‐step opacity is a PSPACE‐hard problem.We describe and analyze the complexity of verifying the notion of infinite‐step opacity in systems that are modeled as non‐deterministic finite automata with partial observation on their transitions. Specifically, a system is infinite‐step opaque if the entrance of the system state, at any particular instant, to a set of secret states remains opaque (uncertain), for the length of the system operation, to an intruder who observes system activity through some projection map. Infinite‐step opacity can be used to characterize the security requirements in many applications, including encryption using pseudo‐ random generators, coverage properties in sensor networks, and anonymity requirements in protocols for web transactions. We show that infinite‐step opacity can be verified via the construction of a set of appropriate initial state estimators and provide illustrative examples. We also establish that the verification of infinite‐step opacity is a PSPACE‐hard problem. May 2012, Volume: 57 Issue:5 , page(s): 1110 ‐ 1124 Optimal Supervisory Control of Probabilistic Discrete Event Systems Pantelic, V.; Lawford, M. SQRL, Department of Computing and Sofware, Faculty of Engineering, McMaster University, Hamilton Abstract Probabilistic discrete event systems (PDES) are modeled as generators of probabilistic languages and the supervisors employed are a probabilistic generalization of deterministic supervisors used in standard supervisory control theory. In the case when there exists no probabilistic supervisor such that the behavior of a plant under control exactly matches the probabilistic language given as the requirements specification, we want to find a probabilistic control such that the behavior of the plant under control is “as close as possible” to the desired behavior. First, as a measure of this proximity, a pseudometric on states of generators is defined. Two algorithms for the calculation of the distance between states in this pseudometric are described. Then, an algorithm to synthesize a probabilistic supervisor that minimizes the distance between generators representing the achievable and required behavior of the plant is presented.Probabilistic discrete event systems (PDES) are modeled as generators of probabilistic languages and the supervisors employed are a probabilistic generalization of deterministic supervisors used in standard supervisory control theory. In the case when there exists no probabilistic supervisor such that the behavior of a plant under control exactly matches the probabilistic language given as the requirements specification, we want to find a probabilistic control such that the behavior of the plant under control is “as close as possible” to the desired behavior. First, as a measure of this proximity, a pseudometric on states of generators is defined. Two algorithms for the calculation of the distance between states in this pseudometric are described. Then, an algorithm to synthesize a probabilistic supervisor that minimizes the distance between generators representing the achievable and required behavior of the plant is presented. International Journal of Robotics Research Feb 2012, Volume: 31 Issue: 5, Special Issue on the Twelfth International Symposium on Experimental Robotics, 2010 Apr. 2012, Volume: 31 Issue: 5, 588‐603 Towards a discretely actuated steerable cannula for diagnostic and therapeutic procedures Elif Ayvali; Chia‐Pin Liang; Mingyen Ho; Yu Chen; Jaydev P Desai Robotics, Automation, and Medical Systems (RAMS) Laboratory, Maryland Robotics Center, Institute for Systems Research, Department of Mechanical Engineering, University of Maryland, College Park, MD, USA The Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA Abstract We have designed, developed, and evaluated the performance of a multi‐degree‐of‐freedom discretely actuated steerable cannula with shape‐memory alloy (SMA) actuators. This will enable us to deliver diagnostic as well as therapeutic devices to the target location through the hollow inner core of the cannula. We propose to use SMAs to generate bending forces due to its small size and high power density. We annealed the SMA wires through a customized training process in an arc shape and mounted them at discrete locations on the outer surface of the cannula to enable joint motion. A pulse‐ width modulation (PWM)‐based control scheme was implemented to control all SMA actuators simultaneously to enable multiple joint motion using a single power supply. The proposed controller was validated through an experiment inside gelatin to mimic the motion of the cannula inside a medium which requires a significant amount of force to move the joints of the cannula. Trajectory planning using a suitable metric and trajectory execution were successfully implemented. To demonstrate the delivery of a diagnostic tool through our cannula, we demonstrate that we can pass an optical coherence tomography probe through the cannula and perform in situ microscale imaging.