METAMORPHIC ROBOTS

DISSECTING THE MODULE The segment module can be divided into three subsystems: 1.Connection plate 2.Sensing,computation and communication 3.Structure and actuation

CONNECTION PLATE Each segment has two connection plates. It attach modules electrically and physically together. The connection plates consists of 4 grooved pins along 4chamfered holes. It has 2 photodiodes and 4 LED’s which determines the relative 6 DOF and orientation of mating plate

SENSING,COMPUTATION AND COMMUNICATION 4 SENSING,COMPUTATION AND COMMUNICATION Four emmiter-detector pairs on the center of four edges. When two centered faces are closer, intensities received from corresponding emitters are larger. It enables local communication for two connected modules. Accelerometer reflects acceleration along axis Each module contains a Motorola Power PC555 embedded processor with 448K internal flash ROM, 1MB of external RAM. Each module communicates over local bus within chains of segments by CAN bus standard. Six sided nodes have switching and routing capability. There are two on each module Various sensors like IR, force, accelerometer, touch sensors are present. They are used to determine current state of system and environment, obtain 6 DOF between docking plates for automatic reconfiguration, select right path for locomotion, to trigger different behaviour modes in response to different terrain conditions G2- position and proximity sensors. G3- BLDC Hall effect sensors, joint angle potentiometer, tension sensors etc

STRUCTURE AND ACTUATION IR sensors align the modules for docking and a latch made of shape-memory alloy holds them together. Holes and pins add stability to connection. Power and data are transmitted by elecrical connectors. For physically docking and undock every connection plate houses a latch. In Conro-robot system every module moves every other with two servomotors controlled by 8-bit microcontroller. Modules communicate through IR interface. Segment module of a Conro -robot

6 LOCOMOTION OF ROBOTS Locomotion of robots is determined by angle between connection plates made by the motor of each module. In addition to physically implemented gaits several other gaits are simulated( 4armed cartwheel locomotion, carrying an object while rolling) In sinusoidal locomotion two properties were considered: 1.torque( how many modules can be raised to cantilevered condition) 2.complaince(it helps system to confirm to terrain and gain maximum foot contact) G1-torque(<5) G2-toque(8) G3(6) Figure illustrates a snake robot passing through a pipe and is considering what configuration to use in order to manipulate the encountered cubic object

LOCOMOTION OF ROBOTS

DISTRUBUTED CONTROL BASED ON DIGITAL HORMONES Self reconfigure system consists of cells and Digital Hormones. Digital hormones are released from cells and captured by receptors of neighboring cells. They are propogated from high to low density space and stops when density is below threshold Metamorphic robots are made of r-cells that can connect and disconnect to form different configurations r-cells’ actions and decisions depend on received hormones, receptors ,local information and knowledge They has no destination, has a lifetime, contains codes. A local engine with a set of receptors can examine the incoming signals received from its active links, and decides if any local actions should be taken.

HOW DO THEY CHANGE SHAPE In order to change from a legged configuration into a snake “leg-tail assimilating” action must be done 4 times. The robot connects its tail to the foot of a leg and disconnects the leg from the body. The process starts with generation of reconfiguration digital hormone LTS The LTS digital hormone will react only to foot cell which is triggered to generate RCT digital hormone(4 ). Only tail r-cell will react to this hormone . The tail will acknowledge RCT by sending out a new TAR digital hormone and inhibit the receptor for accepting any RCT. Only the leg r-cell that initiated the acknowledged RCT will react. It terminates generation of RCT and generates ALT digital hormone and starts reconfiguration. The tail r- cell will terminate TAR digital hormone and start action to assimilate leg. The tail r-cell will reactivate its receptor for RCT digital hormone and another leg assimilation is performed. This procedure repeats until all legs are assimilated l The robot must change from a legged configuratio n (at the top-left of the figure) into a snake (at the bottom of the figure).

CHANGING SHAPE

CONFIGURATION –ADAPTATION FOR ENVIRONMENTS AND TASKS Self-reconfiguration in a dynamic environment is a challenging task. Each configuration is a graph In search space one state can be changed to another through an operator Configuration graphs can be evaluated by evaluation function which takes a set of configuration properties(cofiguration size, energy consumption)and environmental properties( nature of terrain, height of obstacle) and returns a value in total domain On facing a situation, it discovers its current configuration toplogy, evaluates the situation with current configuration using evaluation function If the return value is below threshold, it will search through state space of configuration using operator and evaluation function until a satisfying configuration is found Entire process is implemented in the Digital Hormone

APPLICATIONS Planetary explorations Undersea mining Maintenance tasks on ship hulls and oil tanks Inspection and rescue : In such places as pipes, nuclear plant, or tunnels, which are hardly accessible to humans Other tasks in unstructured unknown environments

FUTURE IMPROVEMENT Currently, all the modules are controlled by a host computer in a central manner to perform previously planned motions. In future, technology will made to allow the modular robot to move or conduct tasks by adapting itself to unknown or dynamically changing environment through the following improvements: • Equipping modules with sensors to detect external environments • Implementing a distributed control system where each module decides its action in an autonomous way • Automatic and more efficient motion planning that is currently hand-coded. Improvement of connection and motion mechanism for more reliable motion.

CONCLUSION Metamorphic robots are a revolutionary robotic technology that could greatly enhance human capabilities in space and enable a new range of scientific activities and planetary exploration. It opens the possibility of constructing robots that can change their shape and functionality, affording extreme adaptability to new tasks and changing environmental constraints. They could employed by astronauts to construct robotic devices suited to new tasks. At a more advanced stage, this technology could allow for autonomous reconfiguration based on the concept of “Digital Hormones”.

REFERENCES 1.parasol.tamu.edu 2. www2.parc.com 3.custer.me.jhu.edu 4. www.cs.cmu.edu 5.www.google.com 6.www.ieee.org

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