Modeling, Control and Energy Efficiency of Underwater Snake Robots

This thesis is mainly motivated by the attribute of the snake robots that they are able to move over land as well as underwater while the physiology of the robot remains the same. This adaptability to different motion demands depending on the environment is one of the main characteristics of the snake robots. In particular, this thesis targets several interesting aspects regarding the modeling, control and energy efficiency of the underwater snake robots. This thesis addresses the problem of modeling the hydrodynamic effects with an analytical perspective and a primary objective to conclude in a closed-form solution for the dynamic model of an underwater snake robot. Two mathematical models of the kinematics and dynamics of underwater snake robots swimming in virtual horizontal and vertical planes aimed at control design are presented. The presented models are derived in a closed-form and can be utilized in modern modelbased control schemes. In addition, these proposed models comprise snake robots moving both on land and in water which makes the model applicable for unified control methods for amphibious snake robots moving both on land and in water. The third model presented in this thesis is based on simplifying assumptions in order to derive a control-oriented model of an underwater snake robot moving in a virtual horizontal plane that is well-suited for control design and stability analysis. The models are analysed using several techniques. An extensive analysis of the model of a fully immersed underwater snake robot moving in a virtual horizontal plane is conducted. Based on this analysis, a set of essential properties that characterize the overall motion of underwater snake robots is derived. An averaging analysis reveals new fundamental properties of underwater snake robot locomotion that are useful from a motion planning perspective. In this thesis, both the motion analysis and control strategies are conducted based on a general sinusoidal motion pattern which can be used for a broad class of motion patterns including lateral undulation and eel-like motion. This thesis proposes and experimentally validates solutions to the path following control problem for biologically inspired swimming snake robots. In particular, line-of-sight (LOS) and integral line-of-sight (I-LOS) guidance laws, which are combined with a sinusoidal gait pattern and a directional controller that steers the robot towards and along the desired path are proposed. An I-LOS path following controller for steering an underwater snake robot along a straight line path in the presence of ocean currents of unknown direction and magnitude is presented and by using a Poincaré map, it is shown that all state variables of an underwater snake robot, except for the position along the desired path, trace out an exponentially stable periodic orbit. Moreover, this thesis presents the combined use of an artificial potential fields-based path planner with a new waypoint guidance strategy for steering an underwater snake robot along a path defined by waypoints interconnected by straight lines. The waypoints are derived by using a path planner based on the artificial potential field method in order to also address the obstacle avoidance problem. Furthermore, this thesis considers the energy efficiency of underwater snake robots. In particular, the relationship between the parameters of the gait patterns, the forward velocity and the energy consumption for the different motion patterns for underwater snake robots is investigated. Based on simulation results, this thesis presents empirical rules to choose the values for the parameters of the motion gait pattern of underwater snake robots. The experimental results support the derived properties regarding the relationship between the gait parameters and the power consumption both for lateral undulation and eel-like motion patterns. Moreover, comparison results are obtained for the total energy consumption and the cost of transportation of underwater snake robots and remotely operated vehicles (ROVs). Furthermore, in this thesis a multi-objective optimization problem is developed with the aim of maximizing the achieved forward velocity of the robot and minimizing the corresponding average power consumption of the system

Task-Space Control of Articulated Mobile Robots With a Soft Gripper for Operations

A task-space method is presented for the control of a head-raising articulated mobile robot, allowing the trajectory tracking of a tip of a gripper located on the head of the robot in various operations, e.g., picking up an object and rotating a valve. If the robot cannot continue moving because it reaches a joint angle limit, the robot moves away from the joint limit and changes posture by switching the allocation of lifted/grounded wheels. An articulated mobile robot with a gripper that can grasp objects using jamming transition was developed, and experiments were conducted to demonstrate the effectiveness of the proposed controller in operations

Bio-Inspired Robotics

Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field

Underwater Robots Part I: Current Systems and Problem Pose

International audienceThis paper constitutes the first part of a general overview of underwater robotics. The second part is titled: Underwater Robots Part II: existing solutions and open issues

Intelligent Escape of Robotic Systems: A Survey of Methodologies, Applications, and Challenges

Intelligent escape is an interdisciplinary field that employs artificial intelligence (AI) techniques to enable robots with the capacity to intelligently react to potential dangers in dynamic, intricate, and unpredictable scenarios. As the emphasis on safety becomes increasingly paramount and advancements in robotic technologies continue to advance, a wide range of intelligent escape methodologies has been developed in recent years. This paper presents a comprehensive survey of state-of-the-art research work on intelligent escape of robotic systems. Four main methods of intelligent escape are reviewed, including planning-based methodologies, partitioning-based methodologies, learning-based methodologies, and bio-inspired methodologies. The strengths and limitations of existing methods are summarized. In addition, potential applications of intelligent escape are discussed in various domains, such as search and rescue, evacuation, military security, and healthcare. In an effort to develop new approaches to intelligent escape, this survey identifies current research challenges and provides insights into future research trends in intelligent escape.Comment: This paper is accepted by Journal of Intelligent and Robotic System

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

A study towards the potentials of robotic technologies to decrease risk to personnel’s safety in Statnett

Background of the project Health, safety and the environment (HSE) is Statnett´s nr.1 priority and Statnett has a zero vision towards accidents. Unfortunately, Statnett and their entrepreneurs experience accidents each year. With an increasing activity level towards 2020, it is natural to estimate that the number of accidents will increase in line with the activity. It can therefore be interesting to study new technologies with high potential to reduce risk, if it is rapidly implemented. Goals There were three goals with this thesis. The first was to identify robotic technologies, available now or within a five-year period with potential for use in Statnett. The second goal was to identify dangerous operations performed by Statnett or Statnett´s entrepreneurs. The third goal was to provide a recommendation of which robotic technologies that can both execute the identified operations and reduce the risks of the operations. General information about the thesis This report was made as a master thesis at the end of a five-year study towards a Master's Degree in science at Norwegian University of Life Science(NMBU). The study was performed between January and May 2016, and represent 30 ECTS. The thesis is written under collaboration between Statnett and NMBU. Method This thesis is based on literature study, interviews, observations and data analysis. Results The main outcome was the following: • There are many types of robotic technologies with different abilities and potential for implementation in Statnett and Statnett´s entrepreneurs, all with a high level of technology readiness(TRL) or already in use. There are however limitations with every type of robotic technologies, e.g. many of the line suspended robotic devices have problems crossing suspension towers and there is actually only one that is supposedly able to cross dead-end towers. • There is no doubt that Statnett and their entrepreneurs perform dangerous operations. Many high risk operations are identified, but there are still reasons to believe that even more could be found. All of the identified operations contain different factors of risk. Some of the risk factors have led to tragic accidents ending with death or severe illness. The biggest identified risk factors are working with helicopter and working at height. • There are several robotic technologies with the possibility to both perform and reduce the risk of some of the dangerous operations identified in this thesis. Recommendation for further work Based on the robotic technology with the highest potential to both execute operations and reduce the operations risks, eleven technologies are recommended for further research and development towards permanent implementation in specific operations.Bakgrunn for prosjektet Helse, miljø og sikkerhet (HMS) er Statnetts topp prioritet. Statnett har en visjon om null ulykker, men opplever ulykker hvert år sammen med sine entreprenører. Frem mot 2020 er det planlagt økt aktivitet og det er derfor naturlig å anta at antall ulykker vil øke i takt med aktiviteten. Det kan derfor være interessant å se på ny teknologis mulighet til å redusere risiko, hvis det kan implementeres raskt. Mål: Oppgaven har tre mål. Det første er å identifisere robotteknologi tilgjengelig i dag eller innen en femårs periode med potensial for bruk i Statnett. Mål nummer to er å identifisere farlige operasjoner utført av Statnett eller deres entreprenører. Det siste målet er å gi en anbefaling av hvilken robotteknologi som har størst mulighet til å både utføre operasjonene samtidig som den kan redusere operasjonens risiko. Generell informasjon om oppgaven Oppgaven er skrevet som en masteroppgave i siste semester av et femårig masterstudie på Norges miljø- og biovitenskapelige universitet (NMBU). Oppgaven representerer 30 studiepoeng og er skrevet som et samarbeid mellom Statnett og NMBU. Metode Oppgaven er basert på litteratur, intervjuer, observasjoner og analyse av innsamlet data. Resultat Hovedresultatene var som følger: • Det er identifisert mange typer robotteknologi med forskjellige anvendelser og potensial for implementering hos Statnett og Statnetts entreprenører. Alle teknologiene var langt i utviklingen, høy ”technology readiness level” (TRL), eller var allerede i bruk. Det var like vell utfordringer med alle teknologiene, som f.eks. at få ”line suspended robotic devices” kan krysse bæremaster og at det faktisk bare er en som skal klare å krysse ankermaster. • Det er ingen tvil om at Statnett og deres entreprenører utfører farlige operasjoner. Det er identifisert mange høy risiko operasjoner, men det er fortsatt grunn til å tro at enda flere kan identifiseres ved et grundigere studium. Alle operasjonene inneholder forskjellige risikofaktorer og noen av risikofaktorene har ført til tragiske ulykker som har endt med død eller alvorlige skader. De største risikofaktorene er identifisert som bruk av helikopter og arbeid i høyden. • Det er identifisert flere robotteknologier med potensial for å både kunne utføre og redusere risikoen til noen av de identifiserte operasjonene. Anbefaling for videre arbeid Basert på den robotteknologien med høyest potensial for å bade utføre og redusere risikoen til noen av de identifiserte operasjonene er elleve teknologier anbefalt for videre arbeid.M-M