Abstract-We describe a framework for cooperative control of a group of nonholonomic mobile robots that allows us to build complex systems from simple controllers and estimators. The resultant modular approach is attractive because of the potential for reusability. Our approach to composition also guarantees stability and convergence in a wide range of tasks. There are two key features in our approach: 1) a paradigm for switching between simple decentralized controllers that allows for changes in formation; 2) the use of information from a single type of sensor, an omnidirectional camera, for all our controllers. We describe estimators that abstract the sensory information at different levels, enabling both decentralized and centralized cooperative control. Our results include numerical simulations and experiments using a testbed consisting of three nonholonomic robots.

Visible light photoredox catalyzed inter- and intramolecular C-H functionalization reactions of tertiary amines have been developed. Oxygen was found to act as chemical switch to trigger two different reaction pathways and to obtain two different types of products from the same starting material. In the absence of oxygen, the intermolecular addition of N,N-dimethyl-anilines to electron-deficient alkenes provided γ-amino nitriles in good to high yields. In the presence of oxygen, a radical addition/cyclization reaction occurred which resulted in the formation of tetrahydroquinoline derivatives in good yields under mild reaction conditions. The intramolecular version of the radical addition led to the unexpected formation of indole-3-carboxaldehyde derivatives. Mechanistic investigations of this reaction cascade uncovered a new photoredox catalyzed C-C bond cleavage reaction.

We describe a framework for controlling a group of nonholonomic mobile robots equipped with range sensors. The vehicles are required to follow a prescribed trajectory while maintaining a desired formation. By using the leader-following approach, we formulate the formation control problem as a hybrid (mode switching) control system. We then develop a decision module that allows the robots to automatically switch between continuous-state control laws to achieve a desired formation shape. The stability properties of the closed-loop hybrid system are studied using Lyapunov theory. We do not use explicit communication between robots; instead we integrate optimal estimation techniques with nonlinear controllers. Simulation and experimental results verify the validity of our approach. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.

We consider search and rescue applications in which heterogeneous groups of agents (humans, robots, static and mobile sensors) enter an unknown building and disperse while following gradients in temperature and concentration of toxins, and looking for immobile humans. The agents deploy the static sensors and maintain line of sight visibility and communication connectivity whenever possible. Since different agents have different sensors and therefore different pieces of information, communication is necessary for tasking the network, sharing information, and for control.

We describe a framework for coordinating multiple robots in cooperative manipulation tasks in which vision is used for establishing relative position and orientation and maintaining formation. The two key contributions are a cooperative scheme for localizing the robots based on visual imagery that is more robust than decentralized localization, and a set of control algorithms that allow the robots to maintain a prescribed formation (shape and size}. The ability to maintain a prescribed formation allows the robots to "trap" objects in their midst, and to ''jlow '' the formation to a desired position. We derive the cooperative localization and control algorithms and present experimental results that illustrate the implementation and the pegonnance of these algorithms.

In this contribution we have tried to investigate whether the mechanical properties of the reverse micellar (RM) interface dictate the physical properties of entrapped water molecules in the RM waterpool. We choose AOT/Igepal-520/cyclohexane (Cy) mixed RM as a model system which exhibits synergistic water solubilization behavior as a function of interfacial stoichiometry. Such a phenomenon associates systematic modification of the interface curvature. Dynamic light scattering (DLS) studies reveal linear increase in the droplet size and aggregation number of the RMs with increasing XIgepal (mole fraction of Igepal in the surfactant mixture). FTIR study in the 3000-3800 cm(-1) region identifies that the relative population of the surface-bound water molecules is higher in AOT RM compared to that in Igepal RM, and in mixed systems it also follows a linear trend with XIgepal. Water relaxation dynamics as probed by time-resolved fluorescence spectroscopy using Coumarin-500 also reveals an overall linear trend with no characteristic feature around the solubilization inflation point. Our study clearly identifies that the physical properties of water in RM are mostly governed by the interfacial stoichiometry and water content, and merely bares any dependence on the mechanical properties of the interface.

Pd-catalyzed oxidative cyclizations of 1,6-enynes have found useful applications in organic synthesis, [1] but such reactions with Au and Pt catalysis remain largely unexplored.[2] Goldcatalyzed cycloisomerizations of 1,5-and 1,6-enynes provide uncommon and useful carbocyclic frameworks. [3] In the presence of organic oxidants, most enynes fail to produce oxidative cyclization products because oxidations of hypothetical gold-carbenoid intermediates are difficult. [4,5] Herein, we report two new oxidative cyclizations of 1,5-enynes via 5-endo-dig and 5-exo-dig cyclizations, respectively; both reactions are implemented with Au I and 8-methylquinoline Noxide. The success of such reactions relies on the prior oxidations of enyne [6] form a-carbonyl carbenoids A and B, followed by their intramolecular cyclizations (Scheme 1). Terminal alkynes favor the oxidation at the C2 alkynyl carbon atom and aminoalkynes prefer the C1 carbon atom. Table 1 shows the oxidative cyclization of 2-aminoalkynylstyrene 1 a [7] over commonly used Au I and Pt II catalysts (5 mol %). We employed 8-methylquinoline N-oxide, which exhibited greater catalytic activity than diphenylsulfoxide and other pyridine-based oxides. [8][9][10] Treatment of a solution of 1,5-enyne species 1 a ( We prepared various 1,5-enynes 1 b-l (Table 2) bearing an aminoalkynyl substituent to assess the generality of this oxidative cyclization. Entries 1-5 in Table 2 show the applicability of this catalysis to enynes 1 b-1 f bearing varied electron-withdrawing amino groups including R 2 = Ms and Ts (Ms = methansulfonyl, Ts = toluene-4-sulfonyl), R 3 = Me, nBu, and phenyl to produce 3-carbonyl-1H-indene products 2 b-2 f in good yields (78-92 %). Similar to its analogue 1 a, propan-4-sultam species 1 g was compatible with this catalysis,

A transition metal-free Heck-type cyclization/isomerization reaction has been developed. Mediated by potassium tert-butoxide and phenanthroline a variety of benzofuran derivatives have been synthesized.