3PAC: A Plug-and-Play System for Distributed Power Sharing and Communication in Modular Robots

In modular robotics, there is classically a compromise between coupling complexity and functionality. The mechanical and electrical designs are linked, such that adding electrical features often requires redesigning the mechanical components. However, increasing the functionality of each electrical contact adds capabilities or redundancies to existing robots without redesigning the coupling and allows for fewer contacts in new designs. This article presents a power distribution and local communication system for modular robotics, using only three electrical contacts between modules. The proposed system can be easily recreated, modeled, and outfitted into an existing modular robotic coupling to introduce power sharing, communication, or redundancy, without increasing the couplings mechanical complexity. By focusing on local power transfer, the system is scalable in number as well as coherent with modularity. We demonstrate that, through this system, distributed power sharing can improve the runtime of a simple modular robotic system by up to 62% while maintaining local communication streams. The circuit is modeled through empirical characteristics and therefore the same methods can predict the power distribution accurately in any other modular robot.

From Modular Origami Robots to Polygon-based Modular Systems: a New Paradigm in Reconfigurable Robotics

Christoph Heinrich Belke

A useful robot is one that fulfils its intended function. In a factory setting, where robots have been used successfully for decades, this function is often singular and clearly defined. Similarly, the surroundings of the robot are mostly known, sterile, and unobstructed. Taking robotic systems out of these conditions and into the real world comes with numerous challenges that are non-existent in factory cages. We want personal robots to cope with the uncertain and dynamic environments we inhabit, while at the same time managing and solving diverse tasks. Reconfigurable robots aim to achieve this by changing shape and function to address a variety of applications, environments, and users. While reconfigurable robots carry a lot of promise, finding a balance between the system's adaptability, the extent to which it can alter shape and function, and the added complexity is difficult. Research efforts have largely focused on proof-of-concept studies with limited reconfigurability and application range, avoiding the increasingly overwhelming mechanical, computational, and electronic complexities. This thesis introduces a new paradigm to the world of reconfigurable robotics with an inherent adaptability through simplification of the underlying structure. Approximating physical structures through polygon abstractions, similar to computer graphics, such systems can assume a wide range of structural or functional three-dimensional shapes. Based on this paradigm, it also presents a new robotic platform combining the concepts behind both modular and origami robotics, as well as reconfigurable mechanisms and polygon meshing. In order to take advantage of this new paradigm, a diverse set of problems must be investigated, spanning multiple robotic disciplines. With an increasing degree of reconfigurability, both within a module and the overall system, the growing physical and mechatronic requirements need to be analysed and addressed accordingly. New reconfiguration algorithms and control strategies need to be developed to cope with the large, and constantly changing, number of degrees of freedom. These must then be synchronised and scaled appropriately, leveraging modularity at multiple levels, to accomplish diverse sets of tasks and functions. Addressing the challenges associated with this new robotic paradigm and proving its viability provides the context for this thesis. In a first phase it outlines the initial conception, studying scalability and applicability through the combination of modularity and origami robots with a first prototype and its use in multiple scenarios. It continues with the development and analysis of several building blocks of modular origami robots, both mechanical and algorithmic, analysing mechanisms for the coupling between modules and the reconfiguration process. In the second phase the proposed paradigm is elaborated into its full form, integrating and examining reconfigurable mechanisms and polygon meshing. The resulting morphological and functional flexibility is validated through the development and testing of a highly sophisticated modular robotic system. Individual modules can alter their own triangular shape, drive towards and attach to each other, and transform into functional three-dimensional configurations. The conceptual and physical systems developed and studied in this thesis answer some of the challenges posed by this new paradigm and underline the potential of reconfigurability in robotics.

EPFL2020

Automatic Gait Generation in Modular Robots: to Oscillate or to Rotate? that is the question

Auke Ijspeert, Soha Pouya, Alexander Spröwitz, Jesse van den Kieboom

Modular robots offer the possibility to design robots with a high diversity of shapes and functionalities. This nice feature also brings an important challenge: namely how to design efficient locomotion gaits for arbitrary robot structures with many degrees of freedom. In this paper, we present a framework that allows one to explore and identify highly different gaits for a given arbitraryshaped modular robot. For this, we use simulated robots made of several Roombots modules that have three rotational joints each. These modules have as interesting feature that they can produce both oscillatory movements (i.e. periodic movements around a rest position) and rotational movements (i.e. with continuously increasing angle), leading to very rich locomotion patterns. Here we ask ourselves which types of movements — purely oscillatory, purely rotational, or a combination of both— lead to the fastest gaits. To address this question we designed a control architecture based on a distributed system of coupled phase oscillators that can produce synchronized rotations and oscillations in many degrees of freedom. We also designed a specific optimization algorithm that can automatically design hybrid controllers, i.e. controllers that use oscillations in some joints and rotations in others, for fast gaits. The proposed framework is verified through multiple simulations for several robot morphologies. The results show that (i) the question whether it is better to oscillate or to rotate depends on the morphology of the robot, and that in general it is best to do both, (ii) the optimization framework can successfully generate hybrid controllers that outperform purely oscillatory and purely rotational ones, and (iii) the resulting gaits are fast, innovative, and would have been hard to design by hand

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2010

Roombots: Design and Implementation of a Modular Robot for Reconfiguration and Locomotion

Alexander Spröwitz

In this thesis we present the design and implementation of a novel self-reconfiguring modular (SR-MR) robotic system: Roombots. We are aiming at three main applications with Roombots; locomotion through self-reconfiguration in the regular cubic 3D-lattice on structured surfaces, locomotion in non-structured environments applying central pattern generators (CPG) as the locomotion controller, and self-assembly and reconfiguration of static objects of the day-to-day environment, such as furniture. Robot assemblies from self-reconfigurable modular robots have the ability to adapt to a given task and working environment by altering their shape through a series of reconfiguration moves, and attachments and detachments between the modules. We are interested in self-reconfiguring modular robots for their shape-changing capabilities, and their distributed characteristics. We envision the following applications for Roombots: First, self-reconfiguration in a structured 3D lattice, i.e. a floor and walls equipped with connectors. Embedded connectors can provide pivot points for locomotion of SR-MR assemblies, and docking and recharging places for our adaptive furniture pieces. Second, our proposed concept for locomotion control of modular robots on non-structured ground are central pattern generators. Third, we would like to build adaptive and versatile furniture from modular robots and light-weight elements. In the following we are able to count more than 60 modular robotic systems, developed over the last two decades. However we were unable to identify an existing system which could provide us with all desired kinematic and geometric capabilities. This led us to design and implement a novel self-reconfiguring modular robotic system: Roombots. To tackle the module design we attempt to identify both meaningful design parameters from existing modular robots, and essential features for our applications. The combination of both leads to the kinematic and geometric description of the Roombots modules, and eventually to its implementation. In order to be able to assemble furniture from our Roombots units in the future, we need a reconfiguration framework which supports the specific requirements of Roombots. Metamodules made of two units attached in-series are attracted and guided by a virtual force-field, they use broadcast signals, look-up tables of collision clouds and simple assumptions about their near environment to reach their seeding positions, which are currently hand coded. For the task of locomotion in non-structured environments we propose a framework for learning to move with modular robots using central pattern generators and online optimization. The distributed implementation of CPGs offers an ideal substrate for producing locomotion patterns and for online learning, and an optimization framework for fast learning.

EPFL2010