Design and Operation of Human Locomotion Systems

Design and Operation of Locomotion Systems examines recent advances in locomotion systems with multidisciplinary viewpoints, including mechanical design, biomechanics, control and computer science. In particular, the book addresses the specifications and requirements needed to achieve the proper design of locomotion systems. The book provides insights on the gait analysis of humans by considering image capture systems. It also studies human locomotion from a rehabilitation viewpoint and outlines the design and operation of exoskeletons, both for rehabilitation and human performance enhancement tasks. Additionally, the book content ranges from fundamental theory and mathematical formulations, to practical implementations and experimental testing procedures.

• Written and contributed by leading experts in robotics and locomotion systems
• Addresses humanoid locomotion from both design and control viewpoints
• Discusses the design and control of multi-legged locomotion systems

• Language: English
• Publisher: Academic Press
• Release date: Sep 10, 2019
• ISBN: 9780128156605

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Preface

Marco Ceccarelli, Tor Vergata University, Rome, Italy

Giuseppe Carbone, University of Calabria, Rende, Italy

This book aims to give a survey of advances on locomotion systems with multidisciplinary viewpoints, including mechanical design, biomechanics, control, computer science. In particular, the book addresses specifications and requirements to achieve a proper design of locomotion systems. It gives insight on the gait analysis of humans by considering image capture systems. It investigates also the human locomotion from a rehabilitation viewpoint. It outlines the design and operation of exoskeletons both for rehabilitation and human performance enhancement tasks. Multilegged locomotion systems are also discussed with careful attention.

Expected readers can be identified as scholars dealing with related topics with various backgrounds including mechanical design, biomechanics, control, computer science. The book can be also seen as a reference textbook for PhD students. The multidisciplinary contents distinguish this book from other currently available books on the topic as the book content ranges from fundamental theory and mathematical formulations up to practical implementations and experimental testing procedures.

We wish to acknowledge all the authors and expert blind reviewers for their significant contributions to this project. Also it is gratefully acknowledged the professional assistance by all the staff at Elsevier that have supported this project with their assistance and valuable advice in the preparation of the book.

Last but not least we are indebted with our families. Without their patience and understanding it would not have been possible for us to work on this book.

Chapter 1

Mechanism design for legged locomotion systems

Giuseppe Carbonea; Marco Ceccarellib    a DIMEG, University of Calabria, Rende, Italy

b LARM2: Laboratory of Robot Mechatronics, Department of Industrial Engineering, University of Rome Tor Vergata, Rome, Italy

Abstract

This chapter gives an overview of challenges and solutions for designing mechanisms in legged locomotion systems. Key attention is given to the mechanism design since it can be considered fundamental to achieve proper user-friendly cost-oriented solutions. Several prototypes are described by emphasizing their characteristics and design challenges with illustrative examples in several cases ranging from bipeds to multilegged solutions.

Keywords

Mobile robots; Legged locomotion; Mechanism design; Modeling; Experimental validation

1 Introduction

Locomotion is defined as the Movement or the ability to move from one place to another [1]. More in particular in IFToMM terminology [2], it is defined as autonomous, internally driven change of location of human being, animals, or machines during which base of support and center of mass of the body are displayed with more details in the several types of locomotion as per the environment in which it is performed.

Locomotion is fundamental to the survival of many animal species including humans. The mechanics and performance of locomotion varies significantly as function of the environment in which locomotor behaviors are executed, which can be divided into terrestrial, aquatic, aerial, as outlined in refs. [3–6]. Terrestrial locomotion can be achieved with legs, wheels, and crawlers. Legged locomotion is the most widely used solution for terrestrial locomotion in nature as it is the most effective speedy and versatile when it operates in a rough terrain or in presence of obstacles. The energy efficiency of legged locomotion might significantly vary among animals and machines. Wheeled/crawler locomotion is instead preferred for vehicles on flat surfaces as it can be more easily controlled, and it can be more energy efficient.

A large literature reports a wide range of legged locomotion systems, which have been designed for a wide variety of applications as indicated for example in refs. [7, 8]. For example, there are legged locomotion systems, which are used for entertainment purposes; other solutions for carrying heavy loads on hills or rough terrains, or even for carrying humans while overcoming stairs or other architectonic barriers. The common limits of legged locomotion systems are high costs and complex design and operation, which often prevent a widespread in the market, even if they have been inspired by very successful examples in nature. Accordingly, efforts should be made to improve user-friendliness, user-printed design and operation, costs of the solutions for legged locomotion systems, with activities since the very early design stage.

Generally, legged systems can be slow and more difficult to design and operate with respect to mobile machines that are equipped with crawlers or wheels. But, legged robots are more suitable for rough terrain, where obstacles of any size can appear. In fact, the use of wheels or crawlers limits the size of the obstacle that can be climbed, to half the diameter of the wheels. On the contrary, legged machines can overcome obstacles that are comparable with the size of the machine leg.

This chapter provides useful considerations for the design of legged locomotion systems by focusing at their mechanism synthesis for specific applications with suitable low-cost user-friendly features. After a general overview on design requirements and design process, several examples are reported as based on over 20 years of experiences by the authors.

2 Characteristics of legged locomotion

Legged locomotion is the basis for several different types of movement such as walking, running, and jumping. Walking and running, in which the body is carried well off the surface on which a body is moving (substrate), occur only in arthropods and vertebrates. Running (cursorial) vertebrates are characterized by elongated lower legs and feet and by reduction and fusion of toes. Saltatory locomotion, movement by leaping, hopping, or jumping, is found in a number of insects and vertebrates.

Only arthropods (e.g., insects, spiders, and crustaceans) and vertebrates have developed a means of rapid surface locomotion. In both groups, the body is raised above the ground and moved forward by means of a series of jointed appendages, the legs. Because the legs provide support as well as propulsion, the sequences of their movements must be adjusted to maintain the body's center of gravity within a zone of support; if the center of gravity is outside this zone, the animal loses its balance and falls. It is the necessity to maintain stability that determines the functional sequences of limb movements, which are similar in vertebrates and arthropods. The apparent differences in the walking and slow running gaits of these two groups are caused by differences in the tetrapodal (four-legged) sequences of vertebrates and in the hexapodal (six-legged) or more sequences of arthropods. Although many legs increase stability during locomotion, they also appear to reduce the maximum speed of locomotion. Whereas the fastest vertebrate gaits are asymmetrical, arthropods cannot have asymmetrical gaits, because the movements of the legs would interfere with each other.

The cycle of limb movements is the same in both arthropods and vertebrates. During the propulsive, or retractive, stage, which begins with footfall and ends with foot liftoff, the foot and leg remain essentially stationary as the body pivots forward over the leg. During the recovery, or protractive, stage, which begins with foot liftoff and ends with footfall, the body remains essentially stationary as the leg moves forward. The advance of one leg is a step; a stride is composed of as many steps as there are legs. During a stride, each leg passes through one complete cycle of retraction and protraction, and the distance that the body travels is equal to the longest step in the stride. The speed of locomotion is the product of stride length and duration of stride. Stride duration is directly related to retraction: the longer the propulsive stage, the more time is required to complete a stride and the slower is the gait. A gait is the sequence of leg movements for a single stride. For walking and slow running, gaits are generally symmetrical—i.e., the footfalls are regularly spaced in time. The gaits of fast-running vertebrates, however, tend to be asymmetrical—i.e., the footfalls are irregularly spaced in