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Configurable Robots

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1. Configurable RobotsS Austin Moses 2. Modular Self-Reconfiguring (MSR) Robots Robots composed of a large number of repeated modules thatcan rearrange their connectness to form a large variety ofstructures. They are able to deliberately change their own shapes byreorganizing the connectivity of their modules to adapt toenvironment or perform new tasks. Best known example of an MSR robot would be thefictional T1000 liquid-metal robot from the film, Terminator2: Judgment Day. Self-reconfigurable mechanism utilizes two types segmentarticulation Lattice reconfiguration Chain reconfiguration. 3. Architecture Chain Architectures: Modules are connected together ina string and tree topology. Motion controls of the modules areexecuted sequentially. Easier to design and implement. Lattice Architectures: Modules are connected in someregular, space filling 3 D pattern. Control and motion are executed inparallel. More flexible and efficient to formcomplex structures. More suitable for dynamicenvironments. 4. Homogeneous and HeterogeneousReconfigurable RobotsHomogeneous All modules are all the same Module position determines role Less-costly hardware/software design process Simple to reconfigureHeterogeneous Can have different modules Function of module determines role Many different hardware/designs costly Complex reconfiguration 5. Chain: CKBot System The CKBot system is a reconfigurablerobotic system developed by Yim atthe University of Pennsylvania. These modules utilize a servo torotate one portion of the module withrespect to the other. Global inter-module communicationthrough CANbus as well as localneighbor-to-neighbor communicationis incorporated on the modules. Thissystem has also been used in someexperiments in self-repair. 6. Lattice: Atron System The Atron system reconfigures in a latticesystem, but can form chains as well. Thisimage shows a four legged or wheeledconfiguration depending on how themodules are actuated. Modules can distribute power via theirbonding mechanisms and use a powermanagement system for voltage regulationand battery charge maintenance. A module consists of two hemisphereswhere one can rotate continuously relativeto the other. Reconfiguration is performed by having onemodule grab another and then rotate somemultiple of 90 degrees to another position inthe lattice structure. 7. Hybrid: M Tran System The M-TRAN system developed by Murata at AIST/Tokyo Institute ofTechnology combines the positive capabilities of chain and lattice basedsystems to implement a highly maneuverable and reconfigurable system,. A module consists of one passive and one active cube that can pivotabout the link that connects them and can form chains for performingtasks. However during reconfiguration, each of a modules two cubes canoccupy a discrete set of positions in space when attempting to align withanother module and bond for reconfiguration as in a lattice system. 8. How Do They Re-configure ? Deterministic reconfiguration: Relies on units moving or being directly manipulated into their targetlocation during reconfiguration. The exact location of each module/unit is always known. Stochastic reconfiguration Relies on units moving around using statistical processes. The exact location of each unit only known when it is connected to themain structure, but it may take unknown paths to move betweenlocationsSelf-reconfigure The units can do this in three ways They can move among each other. They can change their size. They can change a particular property, like color. 9. Complexity in Robot Configuration With numerous configuration for a set of modules, the problem ofrecognizing & choosing useful config. is a central area of research. Factors- Processor organization(centralized/decentralized), inter-modulecommunication schemes(global bus, local neighbour-neighbour),module labelling(unique module id vs unlabeled) andstructural symmetry all add to modular systems complexity. Centralized-With help of identifying labels central controllerdesignates explicit commands over global bus. There is no indicationof relative location of modules within the configuration. Global & Neighbour-neighbour adjacency is not enough to representfull kinematics relationship between 2 modules. 10. Approaches Robot Configurations Variants of adjacency matrices that take into account how structuresare put together & adds essential structural information, such as intermodule-port connections. When doing self discovery its often useful to see if a configuration issame as another configuration by matching a configuration with theone in a library of configuration. In case of neighbour to neighbour communication(ATRON),distributed algorithms that employ processors of modules interactingtogether in parallel, divides the computation required. These MSRsystems use token type messages to pass configuration info frommodule-module. Enumeration algorithm developed by chen more precisely counts thenumber of non-isomorphic configurations. 11. APPLICATIONS Studies of the flow of excitation in heart tissue, the dispersal ofmedicinal drugs, and pattern recognition Space - If you send a robot to Mars, for example, and it breaks, thereis little you can do. But if instead of sending a fixed robot you send arobot with a supply of modules, then that robot may be able to self-repairand they need to sustain operation for long periods of timewithout human assistance. Search & Rescue - Disaster areas such as those around collapsedbuildings or other structures present another type of highlyunstructured unpredictable environment where the use of an MSRrobot could be beneficial. For example, the MSR system could takethe form of a snake which can more easily squeeze through small voidspaces to find victims. Bucket of Stuff - The system would be a consumer product comprisedof a container of reconfigurable modules that would reconfigure toaccomplish arbitrary household tasks. This application can be seen asthe most general practical goal of MSR robotics: a system that canadapt to any task in real time 12. References MARK YIM, PAUL WHITE, MICHAEL PARK, JIMMY SASTRA(2009) Modular Self-Reconfigurable Robots. In: Encyclopedia ofComplexity and Systems Science, University of Pennsylvania,Philadelphia, USA, pp 1932

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