Introduction to the Mechanics of Space Robots

Abstract

This text started as a collection of notes of the lectures on Space Robotics given by the author to the students of the International Master on Space Exploration and Development Systems (SEEDS). The aim of the course was the study of the automatic machines aimed to operate both autonomously and as a support to astronauts in space exploration and exploitation missions, with particular attention to the devices designed for planetary environment, including small planets, comets and asteroids.This material was then completed and made more systematic so that it can hopefully be useful not only to the students of that course but also to those who have an interest in the wide and much interdisciplinary field of space robotics, and in particular in its mechanical aspects.The focus is drawn mainly on the mechanics of space robots: the author is well aware that, even in this specific field, it is far from being complete and that robots, like all mechatronic systems, are so integrated that no single aspect can be dealt separately. Many important aspects are either dealt with only marginally or altogether left out. The very important topics of the control and the behavior of robots, for instance, are only marginally touched, even if their influence on the mechanical aspect to which this book is dedicated is not at all marginal.The structure of the book is so organized:• Chapter 1: a very short introductory overview of human and robotic space exploration, stressing the need for man-machine cooperation in exploration. The various types of robotic missions in LEO, deep space and on planets and their basic requirements are shortly summarized. • Chapter 2 deals in a synthetic way with the main characteristics of the environments space robots are facing and will face in the future. Since space environment is a specialized subject, dealt with in many books, this subject is only briefly summarized. • The configurations of robot arms and the basic kinematic and dynamic relationships needed for their design are described in Chap. 3. • Chapter 4 is devoted to the study of mobility on planetary surfaces, using different kind of supporting devices, like wheels, legs and aerodynamic or aerostatic devices.vii viii Preface all details. To all of them goes my gratitude. Last, but far from least, this book could not have been written without the support, encouragement and patience by my wife Franca-advisor, critic, editor, companion and best friend since 44 years.A Note on the Illustrations I have made every effort to seek permission from the original copyright holders of the figures, and I apologize if there are cases where I have not been able to achieve my objective. This applies in particular to figures taken from the web, like Figs. 4.10,

Hexapod Walking Robot Locomotion

“…Further discussion on forward and inverse kinematics, for several configuration of HWR such as mammalian, reptile or arachnid can be found, for example, in [1]. Figure 12 shows a flow-chart in order to choose a proper dynamic model of HWR.…”

“…The constants in the polynomials are determined by the initial and end conditions of the endpoint p for l 1 where l i is the length of ith link and m i is the mass of the ith actuator. The degree of these polynomials is chosen so that they are able to express the desired conditions on the initial and final acceleration [87].…”

“…In order to evaluate the Lagrangian, we must obtain the kinetic and potential energies in terms of the generalized coordinates {θ 1 …”

Design Issues for Hexapod Walking Robots

“…Many hexapod rovers for space exploration have been designed and built in the last years. A very rich reference of this vehicle and their design issues can be found in [41].…”

Design of a Novel Leg-Wheel Hexapod Walking Robot

“…Other key factors that have restricted a pervasive application of hexapod robots are high complexity and costs. In fact, HWRs are usually expensive machines, consisting of many actuators, sensors, transmissions, and supporting hardware [6,7]. The complexity of legged locomotion requires careful attention also to the control strategy by considering both path and gait planning.…”