A modal approach to hyper-redundant manipulator kinematics

This paper presents novel and efficient kinematic modeling techniques for “hyper-redundant” robots. This approach is based on a “backbone curve” that captures the robot's macroscopic geometric features. The inverse kinematic, or “hyper-redundancy resolution,” problem reduces to determining the time varying backbone curve behavior. To efficiently solve the inverse kinematics problem, the authors introduce a “modal” approach, in which a set of intrinsic backbone curve shape functions are restricted to a modal form. The singularities of the modal approach, modal non-degeneracy conditions, and modal switching are considered. For discretely segmented morphologies, the authors introduce “fitting” algorithms that determine the actuator displacements that cause the discrete manipulator to adhere to the backbone curve. These techniques are demonstrated with planar and spatial mechanism examples. They have also been implemented on a 30 degree-of-freedom robot prototype

Improving Soft Snake Robot Locomotion Through Targeted Environmental Interactions Using Artificial Snake Skin

This dissertation outlines the design and development of the �first fully-soft, snake robot and its snake-inspired skin. Soft robotics takes advantage of soft materials to, among other things, improve robot interactions with complex, unstructured environments. Due to the interplay between the soft material and the environment, minor tweaks to the morphological design of the robot can produce major changes in behavior when using the same control input. The research goal of this dissertation was to determine how the locomotion a soft snake robot, using a lateral undulation gait, can be improved by targeting a specific environmental interaction through the confluence of body design, gait design, and interfacial mechanism design. Understanding how these three areas of design can affect one another is key in developing robots that are adaptable in a range of environments. Each design area is addressed in a chapter of this dissertation to illustrate how changes to one area propagate to others, and how that can be an advantage to improving the locomotion of a soft robot. Chapter 3 examines how the body design of the robot changes its locomotion capabilities in granular media, focusing on interactions between the body and the ridges formed in the media. Chapter 4 illustrates how improvements to the gait can also be driven by interactions between the robot's body and the granular media. The design and implementation of an interfacial mechanism to further improve locomotion is described in Chapter 5. Kirigami, a Japanese art form involving the patterning of cuts in thin materials, is used to create a snake-inspired skin. The skin design targets directional friction, a morphological characteristic vital to snake locomotion in two axes. Most skins implemented for snake robots focus only on the longitudinal axis for creating directional friction. However, lateral undulation, the gait employed throughout this work, requires a significant lateral resistance to successfully create locomotion. This interfacial mechanism is designed speci�cally for the kinematics of the soft actuators as well as the production of directional friction in two axes, which required the creation of a new set of radial kirigami lattices. Each chapter demonstrates how improvements to locomotion can come from designing the morphological characteristics of the robot alongside the development of a gait and interfacial mechanisms by targeting specific, bioinspired interactions between the robot and the environment. The �final iteration of system resulted in a soft robot and it's snake-inspired skin with a 530% improvement in velocity over the original robot with no skin. The main contributions of this dissertation are: 1. The development of the �first fully-soft snake robot. 2. A skin for lateral undulation with two axes of directional friction 3. A set of new kirigami lattice structures that can be used for bending actuators 4. A framework in which to investigate bioinspired design of robots in three areas of design: morphology, gait, and interfacial mechanisms

The role of functional surfaces in the locomotion of snakes

Snakes are one of the world’s most versatile organisms, at ease slithering through rubble or climbing vertical tree trunks. Their adaptations for conquering complex terrain thus serve naturally as inspirations for search and rescue robotics. In a combined experimental and theoretical investigation, we elucidate the propulsion mechanisms of snakes on both hard and granular substrates. The focus of this study is on physics of snake interactions with its environment. Snakes use one of several modes of locomotion, such as slithering on flat surfaces, sidewinding on sand, or accordion-like concertina and worm-like rectilinear motion to traverse crevices. We present a series of experiments and supporting mathematical models demonstrating how snakes optimize their speed and efficiency by adjusting their frictional properties as a function of position and time. Particular attention is paid to a novel paradigm in locomotion, a snake’s active control of its scales, which enables it to modify its frictional interactions with the ground. We use this discovery to build bio-inspired limbless robots that have improved sensitivity to the current state of the art: Scalybot has individually controlled sets of belly scales enabling it to climb slopes of 55 degrees. These findings will result in developing new functional materials and control algorithms that will guide roboticists as they endeavor towards building more effective all-terrain search and rescue robots.Ph.D

Snake and Snake Robot Locomotion in Complex, 3-D Terrain

Snakes are able to traverse almost all types of environments by bending their elongate bodies in three dimensions to interact with the terrain. Similarly, a snake robot is a promising platform to perform critical tasks in various environments. Understanding how 3-D body bending effectively interacts with the terrain for propulsion and stability can not only inform how snakes move through natural environments, but also inspire snake robots to achieve similar performance to facilitate humans. How snakes and snake robots move on flat surfaces has been understood relatively well in previous studies. However, such ideal terrain is rare in natural environments and little was understood about how to generate propulsion and maintain stability when large height variations occur, except for some qualitative descriptions of arboreal snake locomotion and a few robots using geometric planning. To bridge this knowledge gap, in this dissertation research we integrated animal experiments and robotic studies in three representative environments: a large smooth step, an uneven arena of blocks of large height variation, and large bumps. We discovered that vertical body bending induces stability challenges but can generate large propulsion. When traversing a large smooth step, a snake robot is challenged by roll instability that increases with larger vertical body bending because of a higher center of mass. The instability can be reduced by body compliance that statistically increases surface contact. Despite the stability challenge, vertical body bending can potentially allow snakes to push against terrain for propulsion similar to lateral body bending, as demonstrated by corn snakes traversing an uneven arena. This ability to generate large propulsion was confirmed on a robot if body-terrain contact is well maintained. Contact feedback control can help the strategy accommodate perturbations such as novel terrain geometry or excessive external forces by helping the body regain lost contact. Our findings provide insights into how snakes and snake robots can use vertical body bending for efficient and versatile traversal of the three-dimensional world while maintaining stability

Geometric Motion Planning for Inertial Systems

In order to enable better visualization and understanding of the effect of the robot's geometry and inertia on the robot's trajectories, this dissertation proposes to use geometric mechanics to bridge the gap between the physical motion of a robot and its mathematical structure. The main focus of this research is to investigate the system geometry and inertia and their relationship with the curves and acceleration that produce the most efficient trajectories or gaits. This dissertation ‘s approach has an advantage over the state-of-the-art method, which uses numerical forward dynamic simulations. Such numerical simulations are computationally expensive and dependent on starting parameters. The proposed geometric motion planning framework allows the user to design a trajectory with respect to the requirements without any need for forward simulation. Furthermore, the proposed framework enables the user to understand the system's movement from its mathematical model rather than computing the results and exploring the outputs. Unlike previous works that were focusing on the system geometry to gain insight about the system's movement, this dissertation uses the geometry and inertia to describe the system's movement. This is achieved using two tools to gain insight into the underlying locomotion: constructing geodesics and constructing metric fields. The geodesic illustrates the robots geometric structure of the natural dynamic path which is defined as the straightest path. The metric field in mechanical systems is obtained from the system's inertia which illustrates where it is easier to move in parameterized space. In this research we consider four classes of systems: (1) fixed base systems such as robotic arms, (2) crawling systems in an inertial based environment such as floating snakes, (3) flying object with an abrupt change in momentum such as casting manipulator, and (4) system with fast energy release such as jumping robots

Challenges in the Locomotion of Self-Reconfigurable Modular Robots

Self-Reconfigurable Modular Robots (SRMRs) are assemblies of autonomous robotic units, referred to as modules, joined together using active connection mechanisms. By changing the connectivity of these modules, SRMRs are able to deliberately change their own shape in order to adapt to new environmental circumstances. One of the main motivations for the development of SRMRs is that conventional robots are limited in their capabilities by their morphology. The promise of the field of self-reconfigurable modular robotics is to design robots that are robust, self-healing, versatile, multi-purpose, and inexpensive. Despite significant efforts by numerous research groups worldwide, the potential advantages of SRMRs have yet to be realized. A high number of degrees of freedom and connectors make SRMRs more versatile, but also more complex both in terms of mechanical design and control algorithms. Scalability issues affect these robots in terms of hardware, low-level control, and high-level planning. In this thesis we identify and target three major challenges: (i) Hardware design; (ii) Planning and control; and, (iii) Application challenges. To tackle the hardware challenges we redesigned and manufactured the Self-Reconfigurable Modular Robot Roombots to meet desired requirements and characteristics. We explored in detail and improved two major mechanical components of an SRMR: the actuation and the connection mechanisms. We also analyzed the use of compliant extensions to increase locomotion performance in terms of locomotion speed and power consumption. We contributed to the control challenge by developing new methods that allow an arbitrary SRMR structure to learn to locomote in an efficient way. We defined a novel bio-inspired locomotion-learning framework that allows the quick and reliable optimization of new gaits after a morphological change due to self-reconfiguration or human construction. In order to find new suitable application scenarios for SRMRs we envision the use of Roombots modules to create Self-Reconfigurable Robotic Furniture. As a first step towards this vision, we explored the use and control of Plug-n-Play Robotic Elements that can augment existing pieces of furniture and create new functionalities in a household to improve quality of life

Robot Serpiente Modular Simulado

Para complementar la investigación teórica que explota las capacidades de locomoción de los robots serpiente modulares, un conjunto grande de herramientas es requerido para validar los modelos y controladores diseñados para ese propósito. En nuestra investigación, la mayoría de esos procesos de validación requieren los prototipos del robot real para realizar experimentos que consumen tiempo y en algunos casos comprometen la estructura mecánica del robot. Para superar este último problema un software de simulación se presenta como una herramienta que permite a los investigadores enfrentar el diseño de controles y experimentar de una manera segura, con esta clase de sistemas costosos. El robot Lola-OPTM, diseñado por KM-RoBoTa y liberado como una plataforma abierta de investigación, sirve de personaje virtual principal en la primera versión de nuestro software de simulación de robots serpiente modulares. Los componentes principales de este conjunto de herramientas de simulación corresponden al motor de física, el motor gráfico, la definición del ambiente y el módulo de comunicación que permite que las entradas del simulador se obtengan y la integración con una arquitectura de control mayor utilizada con el robot real.To complement the theoretical research that exploits the locomotion capabilities of Modular Snake Robots, a large collection of tools are required to validate the models and controllers designed for that purpose. In our research, most of these validation processes require the real robot prototypes to perform experiments that are time consuming and a variety of cases compromise the robot s mechanical structure. To overcome this last issue a simulation software arises as a tool that allows researches to face controller design processes and experimentation in a safe manner, with this kind of expensive systems. The robot Lola-OPTM, designed by KM-RoBoTa and released as an open research platform, serves as the main virtual character for the first version of our modular snake robot simulation software. The main components of this set of simulation software tools correspond to the physics engine, the graphics engine, the environment definition and the communication module that allow the inputs to the simulator data to be retrieved and the integration with a major control software architecture used with the real robot.Ingeniero (a) ElectrónicoPregrad

Improving Understanding of Geometric Swimmer Locomotion

This work seeks to improve the knowledge surrounding geometric snake swimmers through both theoretical and practical means. To begin, manufacturing techniques for a silicon-based pneumatic actuator were validated through experimentation. When inflated, the actuators exhibited an unanticipated elongation. In an attempt to confirm theoretical displacement predictions, a more accurate dynamic model was created which included curvature-coupled extension. The resulting model was simulated with varying degrees of extension and corresponding optimized gaits. Results suggest that the pneumatic actuator’s efficiency does improve, although serpenoid systems used as a baseline comparison decreased in efficiency when extension was added. For the second stage of this work, it was assumed that a system’s theoretical model would be either completely unknown or unreasonable to calculate, thus another motion prediction method would be required. This method, referred to as Data-Driven or Empirical Local Connection Derivation, requires the system to execute a gait which adequately spans the desired shape space while its position and velocity are tracked through motion capture. This process is demonstrated using two different locomotors. Finally, these methods are integrated into a continually updated MATLAB extregistered{} graphical user interface (GUI) titled Geometric System Plotter. The aim of this software is to provide geometric system evaluation techniques without requiring background knowledge in geometric mechanics. In addition to the projects described here, other tools and general performance improvements have been integrated into the software for future releases