ADVANCES in NATURAL and APPLIED SCIENCES

ISSN: 1995-0772 Published BY AENSI Publication EISSN: 1998-1090 http://www.aensiweb.com/ ANAS 2016 Special10(7): pages 355-370 Open Access Journal

A Review of Reconfigurable Robots

1A. Krishnaraju and 2Dr. H. Abdulzubar

1Assistant Professor with the Mechanical Engineering Department, Mahendra Engineering College, Namakkal - 637503, India. 2Associate Professor with the Mechanical EngineeringDepartment, Knowledge Institute of Technology. Salem - 637504, India.

Received 25 April 2016; Accepted 28 May 2016; Available 5 June 2016

Address For Correspondence: A. Krishnaraju, Assistant Professor with the Mechanical Engineering Department, Mahendra Engineering College, Namakkal - 637503, India. E-mail: [email protected]

Copyright © 2016 by authors and American-Eurasian Network for Scientific Information (AENSI Publication). This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/

ABSTRACT Robot are constructed with rigid parts and donot change shapeshifteasily. But our reconfigurable robot has been designing that have modules or components that can become together in various ways. Robotsare creating not only different shapes, but different shaped robot bodies that can be moved around. Individual robot module to be required a certain amount of intelligence to know their state and role at various times and various configurations. In some cases, the modules are align the same type(homogeneous) ,while in others are not in same module (heterogeneous). Reconfigurable robot that can be autonomously decided when and how to change their shape are called reconfigurable robot. In our humanoid robot, some bodies can change the shape very easy,and other is so difficult or complicated.Humanoid have large number of degrees of freedom. Ever Since the late 1980’s, many systems of reconfigurable robots have been developed. Following the survey of the various robot modules, ageneral discussionof reconfigurable robots is given, summarizing the main features and concernsofphysical characteristics,locomotion,capabilities,applications, challenges and opportunities of reconfigurable robot research.

KEYWORDS: reconfigurable robot,mechanism, locomotion

INTRODUCTION

A robot that is reconfigurable is able to dynamically and autonomously change its configuration in order to perform the task at offer and purpose in the current environment. A modular robot is comprised of many individual modules, which are roughly similar to cells in organisms. The modules may be homogeneous (identical) or heterogeneous (differentiated). Heterogeneous modules can be dedicated to performing a certain function and thus increase the level of adaptability of the robot. On the other module, homogeneous modules are easier to mass- production, and they make possible the process of self-repair, where a damaged module is unnecessary and replaced by another module. Reconfigurable robots can be lattice-based structures, chain- based structures, or a hybrid of the two structures. Lattice-based structures provide more connection points to be provided and thus ease the process of reconfiguration; however, the rigidity of these structures makes locomotion more constrained Chain-based structures allow for more freedom of movement, however, fewer contact points make reconfiguration more demanding. The reconfigurable robot consists of a collection of individual links and few components that can be assembled in a different (various) configuration. Robots rising technology that promises to enlarge the range of various applications and could potentially impact the future of the world. Basic features of the reconfigurable robots are i) Robots are made up of any number of identical interconnected units, or homogenous or heterogeneous modules. ii) The modules have the ability to move to connecting and disconnecting from another, they by changing the posture or various reconfiguration like crawling, walking or rolling etc.

To Cite This Article: A. Krishnaraju and Dr. H. Abdulzubar., A Review of Reconfigurable Robots. Advances in Natural and Applied Sciences . 10(7); Pages: 355-370

356 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370

iii) The ability to change the posture or shape in adaptability and versatility to suit (multiple) various task requirements depend on upon the tasks. iv) Changing the task may require several and configuration. First, appears in the literature in 1988,sincethese have been growing stream of new latest designs coming from a research and development centrein various countries. We will briefly introduce each of the module platforms existing to date, in various categories. Reconfigurable robots can move and operate in two or three dimensions. Many basic aspects of reconfigurable robots are discussed in the review article [25]. Since the late 1980’s, many reconfigurable robotic systems have been developed. A number of these robot structures are presented and physically challenges and opportunities discussed in this report.

II. Examples of Reconfigurable robots: The first modular reconfigurable robot appearing in the literature was the CEBOT [8] system in 1988, where the modules were measured cellular in structure. While then, numerous other projects using reconfigurable robots have been undertaken and reported in the literature. A brief summary of many of these module projects as follows.

2.1 CEBOT (1988): CEBOT [8]is the first type of module reconfigurable robot, it consists of a number of heterogeneous robot or components that can connect or disconnect from one another to create a different component of robots. It hasinadequatecomputation,sensing function and also capable of reconfiguration.

2.2 Polypod (1993): Polypod was developed by m.yim et al .The module has consists of two types.First one is node,and other one is segment. A segment has two connection plates with 2 D.O.F .The node has 6 connection plates with no D.O.F.

Fig. 2: polypod

2.3 Metamorphic (1993): Metamorphic robots [27] are two-dimensional, homogeneous, lattice-based reconfigurable robots with a hexagon or square-shaped modules, as illustrated in Figure 2. A module having performs locomotion by rolling or sliding over neighboring modules. Each module can perform attached or detached from neighboring modules with mechanical hooks or electromagnets Hexagon modules are rolled over their neighbors whereas square modules slide over their neighbors in a vertical, horizontal, or diagonal direction.

Fig. 3: Metamorphic modules

2.4 Fracta (1994): A self-assembling machine using 2D fracta [21] is capable of reconfiguration, in two dimensions, and self- repairs. Three fracta modules have been built that are 125 mm in diameter and 160 mm in height, with a possibility for micro-scale fracta. If connecting between the modules is magnetic connections are replaced with electrostatic connections.

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Fig. 4: Fracta modules

2.5 3D-fracta Unit (1998): The 3D-Unit robot [22] having three prototypes, two units were built, each spanning 26.5 cms and there based on regular hexagon shape. As described in Figure 3, a cube is in the center and another side arm extends in each of the six directions. T he modules are having homogenous configuration and are capable of changing their local relation, communicating with neighbors. The connection between the two modules is realized through by a grasping structure with a key and keyhole mechanism. Two units mus t be moved together, where one is used as a pivot for the other.

Fig. 5: 3D-Unit module [22].

2.6 Molecule (1998): The Molecule [18, 20] is a 3D lattice -based robot with modules consists of two atoms connected by a link, as shown in Figure 4. It has a 10cm cube module .one module half it can swivel relative to the other module .Connections between the two modules are realized through by a electromagnets mechanism. These modules engage one at om rotating around the other atom.

Fig. 6: Molecule robot

2.7 Vertical (1998): These robots [13] have the ability to reconfigure against gravity, as in the case of climbing stairs - like structures. Each module has a cubic body with an edge length of 90 mm and a pair of arms. Further climbing stairs, another potential use of these robots would be to build a bridge structure for transporting cargo across a gap.

Fig. 7: Vertical modules

2.8 CONRO (1998): CONRO ( CONfigurable Robot) modules [3] are having self -sufficient , homogeneous , three-dimensional structure into chain-like structures. Each module has a body and active and passive connectors with infrared

358 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370 communication systems .Connecting between the two module s are realized through by a pin/hole mechanism. Modules can be assembled into snake configuration and hexapod configurations. It has 108mm long. Now recent robot modules are in very thin film and microcontroller used for miniaturerobot.

Fig. 8: CONRO module

2.9 Polybot (1998): Polybot [37] is constructed from a chain configuration consisting of segment type and node type modules. A chain configuration consisting of nine modules are displayed as shown in figure 8. These configurations are capable of several types of locomotion.There are th ree type of generations G1,G2,and G3 are implemented. It can be link with neighboring modules at 90-degreeangle createhyper-redundant assemblies.

Fig. 9: Polybot

Fig.2.10 Telecubes (2002): Telecubesmodules [33, 35] are 3D cubic -shaped units that execute motion by escalating and constricting the sides of the cube, similar to the way tiles move in an 8 -puzzle are shown in Figure 11. The modules are a homogeneous configuration with simple communication and infrared sensors. The connection mechan isms between modules are realized by using permanent switching magnets.

Fig. 10: Telecubes

2.11 I-Cubes (1999): I-Cubes [35] consist of active links and passive cubes, as demonstrated as shown in Figure 6. The links are moveable and the cubes can be rotated, transform simultaneously in two directions, and act as a pivot joint for a moving link. All the links are connecting and externally controlled by buttons or GUI(graphical user interface)

Fig. 11: I-Cube cube

359 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370

2.12 Crystalline (2000): Crystalline robots [29 ] are homogenous structure modules that perform locomotion using expansion and contraction movements similar to muscles and amoeba. Connecting between the two modules is realized through by means of a key and lock (channel) mechanism, and they contain position sensors. Modules are independent in that they contain their own processor and power supply. Each module has 175mm height a nd 50mm-100mm breadth , depending upon th e task whether it is contracted or expanded.

Fig. 12: Crystalline

2.13 Pneumatic (2002): Pneumatic modules [14] are homogeneous, three -dimensional, cubic-shaped configuration, with pneumatic actuators consisting of flexible bellows, as shown in Figure 10. Connecting between the modules are achieved by using compressed air from these bellow mechanisms.The modules can perform rotational movements and stable contraction and elongation. This module system is motivated by animals such as worms and caterpil lars with hydrostatic skeletons

Fig. 13: Pneumaticmodules

2.14CHOBIE: The CHOBIE modules [17] reconfigure by means of slide motion and successive cooperative movements.Modules are capable of locomotion in three -dimensions, connecting to and separating from other modules, communicating with neighbors, and sensing stress in the environment. Three physical modules have been built, each of whose dimensions are 80x80x75 mm .Connecting between the modules is realized through by mechanical grooves mechanism. T he modules contain force sensors and photo sensors. Mechanical constraints of the modules make transforming structures are difficult.

Fig. 14: Chobie

2.15 M-TRAN (2002, 2004, 2005) : A reconfigurable robot composed of a hybrid of lattice and chain structures is M -TRAN (Modular TRANsformer) [19, 23, 24]. It has highly robust design,also very small actuated modules. It is A 4-legged walker and a caterpillar structure constructed from M -TRAN modules is shown in Figure 13. Ten physical modules have been built, each of size 60 cubic mm for each of the two boxes. The modules contain connection surfaces with permanent magnets. There are sensors for position and orientation.

360 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370

Fig. 15: M-TRAN 4-legged walker (left) and caterpillar (right )

2.16 ATRON (2004, 2006): ATRON [15, 26] robots are lattice -based structures consisting of homogeneous modules composed of two hemispheres, as shown in Figure 14. The modules are capable of sensing til t, distance, and gravity; rotating around their equator. Connecting between the modules realized through by means of point -to-point male/female hook method. A module is unable to move on its own, it must move within own power supply .

Fig. 16: ATRON module

2.17Superbot (2004, 2006): Superbot robots [30] combine features and advantages of M -TRAN [19, 23, 24], CONRO [3], and ATRON [15, 26], as illustrated in Figure 15. These robots are three -dimensional and consist of both lattice and chain structures. The modules have three DOF like Pitch,Yaw,and Roll . Connecting between each modules one of the six identical dock connectors with high level de centralized control communications.

Fig. 16: Superbot

2.18 Claytronics (2004, 2005) : The Claytronics robots [9-11] are one form of programmable matter which behaves according to the ensemble principle [12]. The goal is to develop millions of these units (called catoms ) at the micron -scale, and possibly Nano-scale. Macro-scale prototype catoms have been built. Figure 16 displays two of these modules along with their actual size. Each catom is cylindrical in shape and 44 mm in diameter. They are only two - dimensional, although a three-dimensional version is being developed.The catoms move acco rding to local control determined by electromagnetic forces generated by two cooperating catoms

Fig. 18: Claytronics

2.19 Programmable Parts (2005) : The programmable parts project [2] is based on the use of graph grammars for determining the behavior of the modules. The rules of the graph grammar correspond to chemical reactions. It is possible to design a rulebook so that parts are able to assemble into any desired structure [2].The modules passively float on an air

361 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370 table and bind upon random collisions. Connections between modules are made with permanent magnets.

Fig. 19: Programmableparts

2.20 Deformatron: Deformatron [31] is a homogeneous 3D modular robot with modules that resemble bone, muscle, and tendon structures. These modules can form either rigid lattice structures or flexible chain structures. Physical experiments have demonstrated that the muscle structures have actuation power, the joint structures can transfer translator movement of muscles to rotational movement, and bone structures can transfer movement over long distances. Six LEGO-based prototype modules have been built that are cubic structures with a side length of 8 centimeters. A chain of several Deformatron modules appears in Figure 18. The connectors contain a male and female part that fit into a ball and socket-type joint.

Fig. 20: Deformatron (2006)

2.21 Miche (2006): The Miche system is a modular lattice system capable of arbitrary shape formation. Each module is an autonomous robot module capable of connecting to and communicating with its immediate neighbors. When assembled into a structure, the modules form a system that can be virtually sculpted using a computer interface and a distributed process.

Fig. 21: MICHIE

2.22 Amoeboid(2006): Reconfigurable robots with amoeboid locomotion usefully decentralized control mechanisms that are based on coupled biochemical oscillators [15]. Locomotion of modules is a result of the interaction of forces on the robot. Asymmetry breaking scheme generates a pumping motion between the anterior and posterior ends of the system. The robots are two-dimensional and are comprised of a protoplasm and outer skin layer. Each module has a light sensor and a ground friction control mechanism and is capable of local sensory feedback.

Fig. 22: Amoeboid Robot (2006)

2.23 Odin (2007): Odin [33] is a hierarchical lattice-based robot composed of two different types of modules- cylinder-shaped

362 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370 links and sphere-shaped joints. A prototype consisting of six links and four joints in a tetrahedron structure has been constructed, and this prototype is illustrated in Figure 20. The links are 35 mm in diameter and 110 mm in length, and the joints are 50 mm in diameter. Connections between modules involve a lock and key mechanism. The link modules are capable of communicating with neighbors, performing computation, and power sharing among modules. The modules use a hybrid global and local communication system. Locomotion is based on distributed role-based control.

Fig. 20: Odin links

2.24 Morpho (2008): The Morpho robot [25] is based on deformation and the tensegrity model of the cellular structure, where cells exert expansion and contraction forces on the entire structure. Deformation is the critical biological process for transforming an embryo into a complex structure. Robots are assembled from four types of modules: active link, passive link, surface membrane, and interfacing cubes. The active links can change the shape of the structure, the passive links provide a supporting framework for the structure, the interfacing cubes provide attachment points for the links, and the surface membrane covers the skeleton and changes the structure into a volume or a surface.

Fig. 24: Several forms of Morpho

2.25 Anatomy-based Catoms (2008): The anatomy-based catom robots [5] are inspired by the Claytronics project [9-11]. The robots have not yet been physically created, however, a number of promising simulations using Open Dynamics Engine have been implemented. They often involve thousands of sphere-shaped catom modules, and the researchers envision producing modules on the millimeter to micrometer scales (e.g. radius of 65 micrometers). The robots are hierarchical in both control and structure, in those modules from anatomical parts, which in turn form the robot structure. Modules can be combined to form biologically inspired lattice and/or chain structures that resemble muscle, cilia, bone, tendon, hinge-joint, and whisker.

Fig. 22: Anatomy-based [5].

2.26 Swarmbot (2009): The SWARMORPH project [26] involves the development of a distributed scheme for generating morphologies using autonomous self-assembling mobile robots. Global structures emerge as a result of

363 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370 repeatedly applying local rules. This technique is applied to the swarm robot (s-bot) platform. A general limitation of self-assembling mobile robots has been the fact that there is little control over the structure of the formed robot assembly. This work proposes a mechanism for control of the growth of morphological structures based on self-assembly. One by one, individual robots connect to the forming assembly.

Fig. 26: Structures generated (line, rectangle, star, arrow) [26].

2.27Roombot(2009): Roombots have a hybrid structural design with three degree of freedom, two of them using the diametrical axis within a regular cube, and a third (center) axis of rotation connecting the two spherical parts. The outer Roombots DOF is using the same axis-orientation as Molecubes, the third, central Roombots axis enables the module to rotate its two outer DOF against each other.Connectingbetween the modules by means of latching mechanism.

2.28 Moteins (2011): It is mathematically proven that physical strings of simple shapes can be folded into any continuous area or volumetric shape. Moteins employ such shape-universal folding strategies, with one or two degrees of freedom and simple actuators with only two or three states

Fig. 28: Morteins

III. General: Following is a discussion of the above presentation in terms of features of reconfigurable robots that are of interest and relevance to ongoing research in the field. Types of robots

3.1 Rolling Robots: It has construction very simple as compared to others. In this robot is very fast, very efficient, simple to build and easy to control.

3.2 Walking Robots: This robot can be deal with almost any kind of terrain. It is very smoothness movement. But it cannot move fast because complexity of the system. Currently, a lot of researches going on this robot it can walk climb stands up and down.

3.3 Flying Robots: These robots are very small. It is manually used unmanned planes being used for spying force and combat missions. This type of robot locomotion problems of the rough terrain and slow speed will be overcome.

3.4 Swimming Robots: Some robots are needed to keep the sea boundaries safe from floating mines or attack by submarines and also autonomous robots, space robots, lunar robots etc

3.5 Autonomous Robot: These robots that can perform desired tasks in shapeless environments without continuous human guidance. Many kinds of robots have some degree of autonomy.

3.6 Bipedal Robot: First A variety of doing well bipedal robots have been established over the past ten years. This type robot designed for improve walking stability, but they are designed to lie down in the ground and move fast is very

364 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370 difficult.

3.7 Four legged Robot: This type of robot is also doing some particular task. It has hold large degrees of freedom. But robot has walk very slow.

3.8Wheeled robot: The wheel has been by far the most popular movement mechanism in movable robotics andin man-made vehicles in general. It can achieve very good efficiencies, as demonstratedand does so with a relatively simple mechanical realization These type of all robots are a particular task done only, so the cost of the robot will be more.

Reconfigurable robots: These robots are to change the shape, to adopt the environments (situation) after again come to retain the shape. Basic features of the reconfigurable robots are Robots are made up of any number of identical interconnected units, or homogenous or heterogeneous modules. The modules have the ability to move to connecting and disconnecting from another, they by changing the posture or various reconfiguration like crawling, walking or rolling etc. • The ability to change the posture or shape in adaptability and versatility to suit (multiple) various task requirements depend on upon the tasks. • Changing the task may require several and configuration. • The main features of the reconfigurable robots: • Light weight, small size, flexible (less 5kg), • Smooth on the road, uneven pavement, and slope of smooth operation, • With communication ability, • It can change information between master control, • Strong perception capability, • Autonomous

3.1 Inspiration and Motivation: Versatility: In this systems are potentially more adaptive than conventional systems. The ability to allow a robot or a group of robots to enviable and reassembles machines to form new tasks, such as changing from a legged robot to a snake robot and then to a rolling robot.

Robustness: The robot parts are interchangeable, that means, within a robot between different robots. It can also replace faculty parts autonomously, leading to self-repair.

Low cost: In this type robots can potentially lower overall cost by making many copies of one type modulus. So it’s economic of scale. One set of modules, saving cost through reuse and generate of the system.

Scalablity: In this type of robot can be increased or decreased by adding modules or removing modules

Table 1: Physical systems modules with DOF Physical systems created System Class, DOF Author Year CEBOT Mobile Fukuda et al. (Tsukuba) 1988 Polypod chain, 2, 3D Yim (Stanford) 1993 Metamorphic lattice, 6, 2D Chirikjian (Caltech) 1993 Fracta lattice, 3 2D Murata (MEL) 1994 Fractal Robots lattice, 3D Michael(UK) 1995 Tetrobot chain, 1 3D Hamline et al. (RPI) 1996 3D Fracta lattice, 6 3D Murata et al. (MEL) 1998 Molecule lattice, 4 3D Kotay & Rus (Dartmouth) 1998 CONRO chain, 2 3D Will & Shen (USC/ISI) 1998 PolyBot chain, 1 3D Yim et al. (PARC) 1998

365 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370

TeleCube lattice, 6 3D Suh et al., (PARC) 1998 Vertical lattice, 2D Hosokawa et al., (Riken) 1998 Crystalline lattice, 4 2D Vona & Rus, (Dartmouth) 1999 I-Cube lattice, 3D Unsal, (CMU) 1999 Micro Unit lattice, 2 2D Murata et al.(AIST) 1999 M-TRAN I hybrid, 2 3D Murata et al.(AIST) 1999 Pneumatic lattice, 2D Inou et al., (TiTech) 2002 Uni Rover mobile, 2 2D Hirose et al., (TiTech) 2002 M-TRAN II hybrid, 2 3D Murata et al., (AIST) 2002 Atron lattice, 1 3D Stoy et al., (U.S Denmark) 2003 S-bot mobile, 3 2D Mondada et al., (EPFL) 2003 Stochastic lattice, 0 3D White, Kopanski, Lipson (Cornell) 2004 Superbot hybrid, 3 3D Shen et al., (USC/ISI) 2004 Y1 Modules chain, 1 3D Gonzalez-Gomez et al., (UAM) 2004 M-TRAN III hybrid, 2 3D Kurokawa et al., (AIST) 2005 AMOEBA-I Mobile, 7 3D Liu JG et al., (SIA) 2005 Catom lattice, 0 2D Goldstein et al., (CMU) 2005 Stochastic-3D lattice, 0 3D White, Zykov, Lipson (Cornell) 2005 Molecules hybrid, 1 3D Zykov, Mytilinaios, Lipson (Cornell) 2005 Prog. parts lattice, 0 2D Klavins, (U. Washington) 2005 Miche lattice, 0 3D Rus et al., (MIT) 2006 Zhang & Gonzalez-Gomez (U. GZ-I Modules chain, 1 3D 2006 Hamburg, UAM) The Distributed Flight lattice, 6 3D Oung & D'Andrea (ETH Zurich) 2008 Array Evolve chain, 2 3D Chang Fanxi, Francis (NUS) 2008 EM-Cube Lattice, 2 2D An, (Dran Computer Science Lab) 2008 Sproewitz, Moeckel, Ijspeert, Roombots Hybrid, 3 3D 2009 Biorobotics Laboratory, (EPFL) Programmable Matter by Wood, Rus, Demaine et al., (Harvard & Sheet, 3D 2010 Folding MIT) Sambot Hybrid, 3D HY Li, HX Wei, TM Wang et al.,) 2010 Moteins Chain, 1 3D Center for Bits and Atoms, (MIT) 2011

3.2. Physical Characteristics of Reconfigurable Robots: Most of these projects involve fewer than 10 physical modules thus far. Some have implemented as many as 20 modules and others have implemented as many as 100. Several of these projects may eventually involve hundreds to millions of physical modules. Simulations of robots have involved a much larger number of modules, hundreds to thousands in many cases. The size of the modules has generally been on the order of several centimeters. Researchers of many of these projects have goals for scaling these modules to be on the millimeter or micrometer scale. Projects such as Claytronics [9-11] envision modules on the nanoscale. Several of these projects have experimented with a hierarchical structure of modules. Several modules are combined to construct a meta-module [1, 7], which in some cases, can group again to form another level of structure, as in the Molecule [18, 20] project. One major reason for the use of meta-modules is that it greatly simplifies reconfiguration planning algorithms, which would otherwise be impossible in some cases. Another reason is that several levels of structure allow for greater complexity and closer resemblance to biological structures, as in the ATRON anatomical parts [4] project. Most of the projects have involved homogeneous modules, although a few of them, including Odin [33], have prototyped heterogeneous modules.The modules of many of the projects are capable of several functions, including connecting and disconnecting from neighbors, expanding and contracting, reacting to local interactions, basic computation, locomotion, rotation, climbing over neighbors, determining whether the module is connected to a neighbor, and communicating with neighboring modules. In some cases, modules represent biological structures such as bones, muscles, and tendons, as in the Deformatron [32], anatomy-based catoms [5], and ATRON anatomical parts [4] projects. For many of these projects, the modules are autonomous in that they contain their individual processor and power supply. Sensing abilities for many of these modules include sensing position, orientation, contact, proximity, and gravity. Connection mechanisms among modules include electromagnets, permanent magnets, hooks, and a lock and key mechanism.

3.3Mechanisms for Locomotion and Reconfiguration:

366 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370

Fig. 29: Mechanisms for Locomotion used bio systems

Locomotion and manipulationthe same core issues of stability, contact characteristics, and environmental type: • strength - number and geometry of contact points - center of gravity - static/dynamic stability - inclination of landscape • Characteristics of contact - contact point/path size and shape - angle of contact - roughness • Type of location - configuration - standard , (e.g. water, air, soft or hard ground) Locomotion and reconfiguration of structures have been accomplished by numerous mechanisms. The Telecube [34, 36] modules expand and contract their sides to perform sliding motions similar to tiles of an 8 - puzzle [37]. In the Molecule [18, 20] project, ato ms of modules rotate around each other and execute convex and concave transitions. Crystalline [30] modules expand and contract to effect inchworm -like movement [29].The Claytronics [9-11] modules are rearranged by means of random motion of “holes” within the structure [6]. The programmable parts [2] modules are controlled by graph grammars, which represent chemical reactions and involve random collisions of modules. Locomotion of the Morpho [40] robot is based on deformation and the tensegrity of cellula r structure model. Anatomy-based catoms [5] employ several biologically inspired mechanisms such as artificial reflexes, central pattern generators, gradients, and sensor feedback. I -Cube [35] modules move according to rotations of the cube structures of the module. CHOBIE [17] modules perform sliding motions, where a seed module begins the process and a sprout is grown to extend the structure. The M -TRAN [19, 23, 24] project implements a motion planner that also uses genetic algorithms. Movement of Frac ta [21] units is determined by fitness, diffusion, and activation. The Vertical [13] robots perform rotating and sliding motions similar to cellular automata. Metamorphic [28] modules roll and slide over their neighbors to achieve the desired structure. B ellows of compressed air is the motion mechanism for the Pneumatic [14] robot. Amoeboid [15] robots move as a result of a pumping motion between the anterior and posterior ends of the system. Structures of SWARMORPH [26] robots emerge from a repeated appli cation of local rules. In the movement for the 3D -Unit robot [22], one module acts as a pivot for the other, and modules can move on the plane or flip to the orthogonal plane. Superbot [31] combine mechanisms of M -TRAN, CONRO, and ATRON. Capabilities and Applications of Reconfigurable Robots We are also interested in developing various types of task and capability in the physical world. It can control motion executed in parallel lattice structure in a simple configuration. It can more easily scalable to the more complex structure. In real-world applications, robots are required to achieve locomotion, manipulation, and self-reconfiguration responsibilities in the presence of obstacles and in a wild environment, • Military • Monitoring • Disaster relief • Space • Search and rescue • Medical • Firefighting

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• Commercial applications Numerous physical experiments have been conducted on prototype modules of the previously discussed projects. These experiments have involved basic connecting between units, basic reconfiguration, and basic forward motion. Many types of locomotion have been tested, including worm, inchworm, snake, rolling track, caterpillar, cilia surface, hexapod, slinky, spider, cluster walk, and car. Several other types of functions have also been tested, which include convex and concave transitions, flipping, rotating, recovering from failure, lifting another module, building a stairs structure, arm manipulation, ball balancing, an obstacle course with a step and tunnel, transporting an object across an adjustable ramp, maintaining a bridge structure in a rough environment, and an expandable cube [39, 40].Simulations of numerous types of locomotion and reconfiguration have also been studied. Modes of locomotion include snake, caterpillar, insect, spider, rolling track, H-walker, inchworm, cartwheel, slinky, carrying an object while rolling, and climbing over obstacles (such as stairs). Reconfiguration sequences have been verified and executed and they involve transforming a dog-structure into a couch-structure [29, 30], converting a ladder into a tower [22], and creating and dismantling a stairs structure [13]. Several biologically inspired structures have also been created, including volvox, amoeba, programmable tissue [40], cilia surface, muscle actuated arm, and a whisker-like structure to provide sensing feedback to stimulate grasping of a falling object [5].Besides locomotion and reconfiguration, the structures will eventually be capable of object manipulation, sorting, interacting with other systems, adapting to different environments, using tools, transportation, self-repair, climbing obstacles, traversing tunnels and pipes, and various sensing functions. There are numerous potential real-world applications of modular reconfigurable robots in planetary exploration and various space applications, deep sea operations, radioactive environments, search and rescue, forming bridges and other structures, cooperative transportation, collection, construction, production lines and packaging, assembly lines and sorting, cleaning and maintaining hazardous machinery, Nanorobotics, assisting the disabled, entertainment, synthetic reality, mass production of 3D objects, prosthetics, carrying loads, manipulating objects, avoiding obstacles in unstructured and constrained environments, encircling objects, and inspection.

3.4Challenges for Reconfigurable Robots: There are several limitations that challenge the researchers of many of these projects. These limitations include the fact that some of these robots are controlled externally, some types of configuration are difficult to reach, mechanical constraints of modules make transformations more difficult, and there is a tradeoff between efficiency and adaptability. Future work in modular self-reconfigurable robotics involves increasing the number of modules, constructing smaller, simpler, and lighter modules, building modules that are autonomous in that they contain their own processor, power supply, and sensors, improving the module hardware, strengthening self-repair capabilities, increasing robustness, constructing more complex structures and performing more complex tasks, improving adaptation to the current environment, improvements in motion planning, finding the optimal configuration for a given task, testing different types of terrain and travel distances, experimenting with parallel reconfiguration, and implementing distributed reconfiguration algorithms. In spite of the above developments, large numbers of humans are engaged in ground operations to carry out the missions like • attacking a terrorist camp, • thwarting intrusion in the border, • tackling smugglers in the mid-sea and • rescuing civilians during disastrous situation etc These activities can result in heavy human causalities. If we can replace the human by using reconfigurable robots, unnecessary causalities can be avoided. To personal cost savings either in operations or support with results reduction in life cycle cost. However, the robot should posses the various capabilities that the humans are having namely • Effective communication, • Intelligence, • Changing the posture, • Ability to adjust the loss of member • To reduced work load manpower. • To improve decision-making index tailed loads • No threats of robots in case of biological attacks. • Robots would be hidden for long period of time Without food and less energy 3.5 Challenges in Planning and Control Parallel motion for large-scale manipulation and locomotion with and without obstacles, Optimal (time,

368 A. Krishnaraju and Dr. H. Abdulzubar et al., 2016/ Advances in Natural and Applied Sciences. 10(x) Special 2016, Pages: 355-370 energy) reconfiguration planning with and without obstacles, Robustly handling a variety of failure modes, from misalignments and dead units (not responding, not releasing) to units that behave erratically, Determine the optimal configuration for a given task and environment, and Efficient and scalable communication among multiple units.

3.6 Challenges in Environments: Big systems: Most systems of modular robots have been small in number, especially compared to, for example, the number of components in a living cell. The physical demonstrations of such key system will require rethinking method. Self-repairing systems: Besides reconfiguring itself into a new shape, a system comprised of modular robots would be able to recover from serious damage, such as that which might result from an external collision or internal failure.The proposed challenges are, • Build the highest structure possible • Lift an object as high as possible • Traverse the largest gap.

Conclusions: In this report, many different systems of reconfigurable robots were presented. Several interesting features and abilities of these robotic systems were discussed. Common goals among the researchers of a number of these projects include constructing thousands to millions of millimeter or micrometer robotic modules, and developing robotic structures that are self- repairing, able to perform more complex tasks, and have the ability to adapt to a variety of tasks and environments. Reconfigurable robot must have potential to be special purpose environments indented to be ability to change position in flexibility, versatility, adaptability to suit the depends upon the task environments. If the researchers are successful in implementing these desired features, the use of robotic structures can be extended to domains and applications that are currently unrealizable.

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