For several decades now, mobile robots have been integral to the development of new robotic systems for new applications, even in nontechnical areas. Mobile robots have already been developed for such uses as industrial automation, medical care, space exploration, demining operations, surveillance, entertainment, museum guides and many other industrial and non-industrial applications. In some cases these products are readily available on the market. A considerable amount of literature is also available; not all of which pertains to technical issues, as listed in the chapters of this book. Mobile robots will always be further developed with the goal of performing locomotion tasks, those related to movement and interaction with the surrounding environment, within which a task can be fulfilled even without the supervision of human operators. The complexity of locomotion requires different solutions both for design and operation. As such, a large variety of mobile robots and mobile robotic systems has been, and still can be, developed. In fact, considerable advancements have been achieved within the last few decades, and a vast amount of literature is already available detailing a large variety of mobile robots. The literature emphasizes design issues, operational success, procedures and algorithms that can be used specifically for these applications, as opposed to general approaches for a variety of cases. One key point for mobile robots is interaction with the environment in which the mobile robot moves and corresponding solutions can determine the success or failure of the motion. Indeed, the mechanical design is not very often considered a critical issue, but rather it is often included as an issue in the overall design of mechanical solutions within servo-controlled operation and environment interaction. A second important issue is the acceptance of robotic systems and the corresponding psychological aspects, when robots are proposed to operators and users in fields with very low levels of technical means in their current work practice. These two subjects are the core of the discussions in this book and its companion volume, Designs and Prototypes of Mobile Robots (available separately from ASME Press), which aims to illustrate not only the potential but also the problems for the dissemination of mobile robots and mobile robotic systems in all human activities with service. Authors have been invited from all over the world and chapters have been selected after review as to approach the most challenging aspects and applications of mobile robotic systems, with the aim to survey the current state-of-the-art and its future potential. We believe that readers will enjoy this book and its companion, and will utilize the knowledge gained with satisfaction and will be assisted by its content in their interdisciplinary work for engineering developments of mobile robots, in both old and new applications. This book and its companion can be used as a graduate level course books or guide books for the practicing engineer who is working on a specific problem which is described in one of the chapters. We are grateful to the authors of the chapters for their valuable contributions and for preparing their manuscripts on time. Also acknowledged is the professional assistance by the staff of ASME Press and especially by Dr. Vladimir Vantsevich, who has enthusiastically supported this book project, as the Robotics Series Editor.