International Journal of Pure and Applied Mathematics Volume 114 No. 11 2017, 253-263 ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu Special Issue ijpam.eu Development of Low Cost Printable Modular Robot Saket M. Pardeshi Prajakta P. Pachore Pratibha Nalini R Arockia Selvakumar A* SMBS, VIT University, Chennai, India *[email protected] Abstract Modular robotics is a new approach in the field of robotics. Modular robots are autonomous and self-reconfigurable. It can change its shape by changing its topology. This research gives a detailed of hardware design and development of control system for semi-self - reconfigurable robotic system. Semi-self-reconfigurable robot is homogeneous type with 3D printed modules. Research deals with change in configuration of existing modules, reproduction of modules and equipment advancement, obscuring the edge between the computerized and physical world. Control system is designed such that locomotion is optimized for power consumption. This research also focuses on study of locomotion and the phase difference which is a major factor for locomotion. Snake like locomotion is achieved by sinusoidal wave. Each module consists of sinusoidal generator. Each sinusoidal generator acts as Central Pattern Generator (CPG), which controls rotation angle of each module. Arduino is used as control unit. Use of Arduino enables ease of programming and hardware development. Keywords: Modular Robot; rapid prototyping; semi-reconfigurable robot; Locomotion; Central Pattern Generator; Printable Modular Robot; Arduino 1 Introduction A robot is a mechanical or virtual specialists, more often than not an electro-mechanical machine that is guided by a PC program or electronic hardware. Robots are of various types according to structure, function etc. Modular robotics is a type of robotics where each robot is composed of large number of repeated module. This modules are capable of rearranging themselves to form large variety of structures. Self- reconfigurable system is classified into two main categories; chain type and lattice type. In chain type, modules are connected in series forming tree or loop structure. Chain configuration is versatile but computationally difficult to present and analyze. In lattice configuration, modules are connected in space filling 3D pattern. Modular robotics promises versatility, robustness and low cost. Self-reconfiguration capability of modular robot allows it to adopt it to surroundings. It can change its shape according to the task to be performed i.e. one robot can perform various task. Modular robotic system leads to lower cost since mass production of identical modules has an economical advantage. Toshio Fukuda et al developed first modular robot in 1988 named ‘The Cellular Robotic System (CEBOT)’. CEBOT research developed a concept of cellular robotic system. 253 International Journal of Pure and Applied Mathematics Special Issue It is a new kind of robotic system which is able to reconfigure itself to optimal structure depending on purpose and environment. Each cell is able to communicate with each other. CEBOT has achieved automatic connection and separation. CEBOT was the first step towards modular robotics. Since then modular robotics is developing fast [1]. Mark Yim et al. developed PolyBot in 1998. PolyBot is a chain type modular robot. Each module has one degree of freedom and two connection plate. Further two generation of PolyBot has been developed. Low heterogeneity of system is design point for getting more functionality [2]. Satoshi Murata et al. developed M-Tran in 2002. Modular Transform is a hybrid type of modular robot. Research proposed Central Pattern Generation method for locomotion generation. This made modular robot to adapt to unknown terrain. Research took a huge leap in development of modular robotics [3]. Jens Liedke et al. developed CoSMO in 2013. This Collective Self-Reconfigurable Modular Organism i.e. CoSMO is new modular robotic platform. CoSMO has huge computational and communication capabilities. CoSMO use BLDC motor to actuate which results in high load carrying capacity. CoSMO is also capable of transmitting power among its modules. Modular robots developed so far are highly costly [4]. Denis Krupke et al. developed the Printable Modular Robot (PMR) in 2012 as shown in Figure 1. PMR developed by 3D printed mechanical structure and other components used as per standard. Use of 3D printed structure and standard parts reduce manufacturing cost remarkably [5]. Figure 1: Printable Modular Robot (PMR) Locomotion planning and control is major part of any modular robotic system. Houxiang Zhang et al in his research explained how caterpillar are successful climbers and can manoeuvre in complex environment. Research build Cube-M modular robot and successfully implemented caterpillar like locomotion [6]. VojtechVonˇasek proposed a global motion planning for modular robot, in that the central pattern generators produce periodic control signals, hence wide locomotion generation is found to be possible and his research also presents the modification of ‘Rapidly exploring random tree’ algorithm for modular robot [7]. Dennis Krupke introduced a smart locomotion generation based on automatic orientation and topology detection of a reconfigurable modular robot. In that, two axis accelerometer is integrated with Printable Modular Robot platform. Accelerometer gives orientation and topology of modular robot. Based on the information of accelerometer, optimized locomotion of PMR is generated [8]. Modular robotics holds key to future of robotics. The applications of modular robotics are vast. Mark Yim gives the following applications of modular robotics a) Space exploration b) Search and Rescue c) Bucket of Stuff. As space exploration has many constraints such as unpredictable environment, mass and volume of equipment to carry to study such environment. Modular robotics can give solution to these problems. ‘Bucket of Stuff’ is a futuristic idea where customer will have container of full of modules. And as per need of customer modular robot will take shape and perform desired task [9]. Craig Eldershaw et al developed war robot with PolyBot modular robotic platform [10]. Andres Faina et al developed a modular robot to work under dynamic and unstructured environment in industries. In that, the modular robot is developed for shipyard application [11]. Modular robot is capable of work as Cartesian as well as spherical manipulators. Robot have also achieved climber and walker locomotion. 254 International Journal of Pure and Applied Mathematics Special Issue Based on the literature survey, the modular robotics found to be a costly approach. PMR promises low cost modular robot. Locomotion planning is considered as a one of the major factor which affects the performance of modular robot. Hence there is need of development of locomotion technique for optimized locomotion for effective use of power source. This research aims to develop a low cost printable modular robot and to design a low cost printable modular robot based on the availability of standard components. Research also deals with static analysis of mechanical structure of printable modular robot to check whether the design is safe or not and a control system has developed for different locomotion to optimize the power consumption of PMR. This paper is organized in eight sections. Section 2 describes problem with previous work. Section 3 is devoted to design of modular robot, 3D printing and hardware development. Section 4 deals with analysis and material selection. In section 5, we discuss locomotion techniques. In section 6, we carry out actual prototyping of printable modular robot. Section 7 contains results of static analysis as well as locomotion study. Section 8 summaries research carried out and a discussion on future scope. 2 Problem DefinItion A module of PMR must have enough space to contain all essential components, e.g. microcontroller, actuators and connection mechanism. And robot should be small to fit in restricted space. Hence the research is focused on mechanical design of module and its optimization. The locomotion of snake like robot is like sinusoidal curve. Locomotion affects power consumption. As we set amplitude and phase difference in sinusoidal motion, if amplitude is high motion will be tall but displacement will be short or if amplitude is short motion will be short in height also short displacement. Similarly phase difference affects displacement of modular robot. Hence phase difference is important factor for locomotion. Research is focused on finding optimized phase difference and develop control system for modular robot for optimized power consumption. 3 Design Of Modular Robot Krupke et al. [5], 2012 developed design of modules which are optimized for 3D painting and includes only standard components. The design of printable 3D modules is designed in solid works. Now depending upon standard component availability and considering low cost as main criteria for hardware design, we have improved existing design. As in existing Robot, the cost of power source is high. Hence we are proposing low cost power supply to reduce cost. So depending upon power source and availability of standard electronic components, we have modified the design. Figure 2 shows three iterations of the lower module. Note: increased wall thickness in second generation depending upon available magnet slot specification and design optimization for improved