Modeling and Control of Flexible Link Manipulators

Autonomous maritime navigation and offshore operations have gained wide attention with the aim of reducing operational costs and increasing reliability and safety. Offshore operations, such as wind farm inspection, sea farm cleaning, and ship mooring, could be carried out autonomously or semi-autonomously by mounting one or more long-reach robots on the ship/vessel. In addition to offshore applications, long-reach manipulators can be used in many other engineering applications such as construction automation, aerospace industry, and space research. Some applications require the design of long and slender mechanical structures, which possess some degrees of flexibility and deflections because of the material used and the length of the links. The link elasticity causes deflection leading to problems in precise position control of the end-effector. So, it is necessary to compensate for the deflection of the long-reach arm to fully utilize the long-reach lightweight flexible manipulators. This thesis aims at presenting a unified understanding of modeling, control, and application of long-reach flexible manipulators. State-of-the-art dynamic modeling techniques and control schemes of the flexible link manipulators (FLMs) are discussed along with their merits, limitations, and challenges. The kinematics and dynamics of a planar multi-link flexible manipulator are presented. The effects of robot configuration and payload on the mode shapes and eigenfrequencies of the flexible links are discussed. A method to estimate and compensate for the static deflection of the multi-link flexible manipulators under gravity is proposed and experimentally validated. The redundant degree of freedom of the planar multi-link flexible manipulator is exploited to minimize vibrations. The application of a long-reach arm in autonomous mooring operation based on sensor fusion using camera and light detection and ranging (LiDAR) data is proposed.publishedVersio

Benchmarking Cerebellar Control

Cerebellar models have long been advocated as viable models for robot dynamics control. Building on an increasing insight in and knowledge of the biological cerebellum, many models have been greatly refined, of which some computational models have emerged with useful properties with respect to robot dynamics control. Looking at the application side, however, there is a totally different picture. Not only is there not one robot on the market which uses anything remotely connected with cerebellar control, but even in research labs most testbeds for cerebellar models are restricted to toy problems. Such applications hardly ever exceed the complexity of a 2 DoF simulated robot arm; a task which is hardly representative for the field of robotics, or relates to realistic applications. In order to bring the amalgamation of the two fields forwards, we advocate the use of a set of robotics benchmarks, on which existing and new computational cerebellar models can be comparatively tested. It is clear that the traditional approach to solve robotics dynamics loses ground with the advancing complexity of robotic structures; there is a desire for adaptive methods which can compete as traditional control methods do for traditional robots. In this paper we try to lay down the successes and problems in the fields of cerebellar modelling as well as robot dynamics control. By analyzing the common ground, a set of benchmarks is suggested which may serve as typical robot applications for cerebellar models

Telenursing RoboPuppet

The Tele-Robotic Intelligence Nursing Assistant (TRINA) assists nurses working with infectious patients by performing highly repetitive tasks. The project focused on fabricating a new version of the 2017-2018 Telenursing RoboPuppet through the addition of motors and sensors that provide haptic feedback to the user while simultaneously resisting gravity when the user releases the device. The addition of a simulation environment to visualize the forward/inverse kinematics as well as fully functioning hand controls for TRINA allows for a more user friendly working system. This article discusses the process of the fabrication and implementation of the circuitry, hardware, and programming for the first iteration of the active version of the Telenursing RoboPuppet

Gravity compensation and optimal control of actuated multibody system dynamics

This work investigates the gravity compensation topic, from a control perspective. Thegravity could be levelled by a compensating mechanical system or in the control law, suchas proportional derivative (PD) plus gravity, sliding mode control, or computed torquemethod. The gravity compensation term is missing in linear and nonlinear optimal con-trol, in both continuous- and discrete-time domains. The equilibrium point of the controlsystem is usually zero and this makes it impossible to perform regulation when the desiredcondition is not set at origin or in other cases, where the gravity vector is not zero at theequilibrium point. The system needs a steady-state input signal to compensate for the grav-ity in those conditions. The stability proof of the gravity compensated control law basedon nonlinear optimal control and the corresponding deviation from optimality, with proof,are introduced in this work. The same concept exists in discrete-time control since it usesanalog to digital conversion of the system and that includes the gravity vector of the sys-tem. The simulation results highlight two important cases, a robotic manipulator and atilted-rotor hexacopter, as an application to the claimed theoretical statements.GRIFFIN ERC-2017-Advanced Grant, Action: 788247EU H2020 AERIAL-CORE project contract 871479EU H2020 HYFLIERS project 77941

Model Based Control of Soft Robots: A Survey of the State of the Art and Open Challenges

Continuum soft robots are mechanical systems entirely made of continuously deformable elements. This design solution aims to bring robots closer to invertebrate animals and soft appendices of vertebrate animals (e.g., an elephant's trunk, a monkey's tail). This work aims to introduce the control theorist perspective to this novel development in robotics. We aim to remove the barriers to entry into this field by presenting existing results and future challenges using a unified language and within a coherent framework. Indeed, the main difficulty in entering this field is the wide variability of terminology and scientific backgrounds, making it quite hard to acquire a comprehensive view on the topic. Another limiting factor is that it is not obvious where to draw a clear line between the limitations imposed by the technology not being mature yet and the challenges intrinsic to this class of robots. In this work, we argue that the intrinsic effects are the continuum or multi-body dynamics, the presence of a non-negligible elastic potential field, and the variability in sensing and actuation strategies.Comment: 69 pages, 13 figure

Robot Manipulators

Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world