This is the second chapter of the first section. It presents the mechanical and physical foundations of mobile robots that are needed for a complete understanding of the concepts of further chapters, such as sensor and motion models. It provides a detailed review of the most common electro-mechanical components found in state-of-the-art mobile robots, emphasizing practical aspects, such as weight and size, power consumption, and performance trade-offs. Sensors and actuators, in particular, are stated as the hardware basis for coping with localization and mapping, and thus, specialized sections are devoted to them. The described devices range from low-cost sensors/actuators suitable for hobbyists to expensive professional-grade components.
TopChapter Guideline
Top1. Introduction
As established in the previous chapter, this book mainly focuses on mobile robots, which are indeed more interesting and have a greater potential in the service sector than static robots or robotic arms. Unfortunately, their advantages only come at the cost of an increased complexity, in both software and hardware. The first step to cope with that complexity is to provide the bases related to the mechanics and electronics of this kind of robots.
In this chapter, readers not familiarized with mobile robots will find an accessible, while thorough, overview of typical engineering designs and technologies employed in current research labs to build autonomous robots. Those already familiar with robotic sensors may also find it motivating to go through all the introduced technologies, ranging from those intended for the hobbyists to the latest developments.
A mobile robot must be able to interact with its environment through a set of basic actions. What we mean here by basic action is the execution of some set of minimal operations—in the sense that they do not invoke other actions—which are very close (and coupled) to the hardware of the robot. The set of basic actions of a mobile robot often comprises only one capability: to move around. For instance, in the case of an intelligent vehicle aimed at transporting a payload from one point to another, this capability of moving permits the design of a complete control architecture, capable of accomplishing uncountable specific tasks. More complex robots are equipped in such a way that they can also do other things, for instance grasp and manipulate objects by themselves, which exponentially increases their potential applications. In fact, moving around and manipulating objects are the two most common robot actions today, followed by the ability to communicate with humans and other machines. Just think of how many real-life tasks can be decomposed into sequences of the moving-manipulating pair of actions. Section 2 will review these and other less common robot actions, and how they are implemented in the hardware of current robots.
From the very first instant that a robot interacts with its environment, by moving itself or by manipulating other objects, there appears the need to gain some feedback from the world. For example, if a robot grasps a cup in a kitchen with the intention of taking it somewhere else, it absolutely needs to figure out whether the grasping was achieved at the intended points of the object. As another example closer to the scope of this book, when a wheeled robot intends to walk down a corridor in a straight path it needs to sense the world in order to compare the planned and the actual trajectories to avoid clashing with the walls.