Aksel Andreas Transeth

Snake Robot Obstacle-Aided Locomotion: Modeling, Simulations, and Experiments

Snakes utilize irregularities in the terrain, such as rocks and vegetation, for faster and more efficient locomotion. This motivates the development of snake robots that actively use the terrain for locomotion, i.e., obstacle-aided locomotion. In order to accurately model and understand this phenomenon, this paper presents a novel nonsmooth (hybrid) mathematical model for wheel-less snake robots, which allows the snake robot to push against external obstacles apart from a flat ground. The framework of nonsmooth dynamics and convex analysis allows us to systematically and accurately incorporate both unilateral contact forces (from the obstacles) and isotropic friction forces based on Coulombs law using set-valued force laws. The mathematical model is verified through experiments. In particular, a back-to-back comparison between numerical simulations and experimental results is presented. It is, furthermore, shown that the snake robot is able to move forward faster and more robustly by exploiting obstacles.

A survey on snake robot modeling and locomotion

Snake robots have the potential to make substantial contributions in areas such as rescue missions, firefighting, and maintenance where it may either be too narrow or too dangerous for personnel to operate. During the last 10–15 years, the published literature on snake robots has increased significantly. The purpose of this paper is to give a survey of the various mathematical models and motion patterns presented for snake robots. Both purely kinematic models and models including dynamics are investigated. Moreover, the different approaches to biologically inspired locomotion and artificially generated motion patterns for snake robots are discussed.

3-D Snake Robot Motion: Nonsmooth Modeling, Simulations, and Experiments

A nonsmooth (hybrid) 3-D mathematical model of a snake robot (without wheels) is developed and experimentally validated in this paper. The model is based on the framework of nonsmooth dynamics and convex analysis that allows us to easily and systematically incorporate unilateral contact forces (i.e., between the snake robot and the ground surface) and friction forces based on Coulombs law of dry friction. Conventional numerical solvers cannot be employed directly due to set-valued force laws and possible instantaneous velocity changes. Therefore, we show how to implement the model for numerical treatment with a numerical integrator called the time-stepping method. This method helps to avoid explicit changes between equations during simulation even though the system is hybrid. Simulation results for the serpentine motion pattern lateral undulation and sidewinding are presented. In addition, experiments are performed with the snake robot ldquoAikordquo for locomotion by lateral undulation and sidewinding, both with isotropic friction. For these cases, back-to-back comparisons between numerical results and experimental results are given.

A snake-like robot for internal inspection of complex pipe structures (PIKo)

This paper presents a mechanism for navigating complex pipe structures, both horizontally and vertically. The mechanism consists of a series of identical modules interconnected by two degree of freedom active joints. A set of active wheels on each module provides propulsion. Horizontal motion is achieved through a train-like scheme, while vertical motion is achieved through spanning the pipe alternatingly with the modules. The design and the capability of horizontal and vertical motion is validated through experiments.

A literature review on the levels of automation during the years. What are the different taxonomies that have been proposed

In this paper we present a literature review of the evolution of the levels of autonomy from the end of the 1950s up until now. The motivation of this study was primarily to gather and to compare the literature that exists, on taxonomies on levels of automation. Technical developments within both computer hardware and software have made it possible to introduce autonomy into virtually all aspects of human-machine systems. The current study, is focusing on how different authors treat the problem of different levels of automation. The outcome of this study is to present the differences between the proposed levels of automation and the various taxonomies, giving the potential users a number of choices in order to decide which taxonomy satisfies their needs better. In addition, this paper surveys deals with the term adaptive automation, which seems to be a new trend in the literature on autonomy.

Modeling and path-following for a snake robot with active wheels

Snake robots with active wheels provide interesting opportunities within many areas such as inspection and maintenance and search and rescue operations. The highly-articulated body of a snake robot combined with the advantages of wheeled locomotion makes it ideal for locomotion in, for example, pipes and other narrow or constricted structures. In this paper we present a mathematical model of the dynamics of a snake robot with active wheels together with a novel path-following approach for such robots. The path-following approach includes both how to find a desired turning angle for the snake robot head given a reference path, together with a module coordination strategy based on a n-trailer kinematic model. The path-following approach is tested and verified by simulations with the dynamic model. In addition, simulations suggest that the proposed approach results in reduced commanded joint and wheels shaft torques and, in most cases, a reduced path-following error compared to an implementation of a follow-the-leader algorithm.

Tracking control for snake robot joints

This paper considers the problem of model based control of the joints of a snake robot without wheels. The potential range of applications for snake robots are numerous, and delicate operations such as inspection and maintenance in industrial environments or performing search and rescue operations require precise control of a snake robot joints. To this end we present a controller that asymptotically stabilizes the joints of the snake robot to a desired reference trajectory. The controller is based on input-output linearization of a control plant model of the snake robot dynamics also developed in this paper. In addition, we provide a formal Lyapunov-based proof of the closed-loop stability, together with simulation results for a smooth dynamical model. Finally, the performance of the controller is tested on a non-smooth snake robot model with set-valued Coulomb friction that offers an accurate description of the stick-slip transitions during locomotion.

Developments in Snake Robot Modeling and Locomotion

Snake robots may one day play a crucial role in search and rescue operations and fire-fighting where it may either be too narrow or to dangerous for personnel to operate. Properties such as high terrainability, redundancy, and the possibility of complete sealing of the body of the robot, make snake robots very interesting for practical applications and hence as a research topic. During the last ten to fifteen years, the published literature on snake robots has increased vastly. However, no thorough review of the theory presented in this period regarding mathematical modeling techniques and locomotion of snake robots has been found. The purpose of this paper is to give such a review. Both purely kinematic models and models including dynamics are investigated. The choice of modeling method is linked to snake robot design characteristics and locomotion approach. Different approaches to biologically inspired locomotion are also discussed

A Robotic Concept for Remote Inspection and Maintenance on Oil Platforms

This paper presents a novel concept for remote inspection and maintenance operations on next generation normally-unmanned offshore oil platforms. The concept is presented through the design of a robotic lab facility for automated and teleoperated inspection and maintenance operations by robot manipulators — ranging from simple inspection tasks to advanced maintenance operations. The lab facility is built around two cooperating robot manipulators equipped with sensors measuring temperature, vibrations, gas concentration and sound, and that automatically changes between tools to operate valves, exchange batteries in wireless sensors and to manipulate objects and the integrated process equipment. A graphical interface allows users to start automated inspection rounds where sensor data are collected, analyzed and compared to normal operating conditions, and alarms are generated if deviations are detected. Users may also plan new operations in a virtual environment before executing them, or remotely control the robots through a number of control interfaces. Live video feeds and stereoscopic vision are available to aid the operator during remote operations. A model-based collision avoidance system ensures that both automated operations and unplanned operations are verified before and during execution, and ensures safe operation of the robots. The paper presents results from the lab facility to illustrate the functionality of the remote inspection and maintenance concept, and demonstrate how remote operators may start automatic inspection and maintenance operations, plan new operations in a virtual environment, or directly control the remote facility onshore.Copyright

A robotic concept for remote maintenance operations: A robust 3D object detection and pose estimation method and a novel robot tool

Future normally-unmanned oil platforms offer potentially significantly lower commissioning and operation costs than their current manned counterparts. The ability to initiate and perform remote inspection and maintenance (I&M) operations is crucial for maintaining such platforms. This paper presents a system solution, including key components such as a 3D robot vision system, a robot tool and a control architecture for remote I&M operations on processes similar to those on topside oil platforms. In particular, a case study on how to automatically replace a battery in a wireless process sensor is investigated. A novel robot tool for removing and re-attaching the sensor lid has been designed. Moreover, a robot control architecture for remote control of industrial-type robot manipulators is presented. A 3D robot vision system for localizing the sensor lid and the battery has been developed. The system utilizes structured light, using an off-the-shelf projector and a standard machine vision camera. A novel, robust and fast vision algorithm called 3D-MaMa has been adapted to work for object localization and pose estimation in complex scenes, in our case the process equipment in our lab facility. Experimental results from our lab facility are presented which describe a series of battery replacement operations for various unknown positions of the wireless sensor, and we report on accuracies and success ratios. The experiments demonstrate that the described vision system is able to recover the full pose and orientation of an object, and that the results are directly applicable for controlling advanced robot contact operations. Moreover, the custom-built lid operation tool demonstrates successful results.