Robot Modeling and Control, 2nd Edition

CHAPTER 14MOBILE ROBOTS

In this chapter we discuss the control of nonholonomic systems with a focus on the control of mobile robots. Mobile robots are becoming increasingly important in many applications, such as factory and warehouse automation, service and cleaning, household and medical assistance, military applications, agricultural and forestry applications, and search and rescue. Autonomous highway vehicles (cars and trucks) can also be considered mobile robots.

A distinguishing feature of mobile robots that impacts the control problem is the presence of nonholonomic constraints. Nonholonomic constraints arise in two primary ways.

1. In rolling without slipping constraints. For example, the translation and rotation of a wheel are not independent if the wheel rolls without slipping. Examples include:
   • A wheeled mobile robot, unicycle, automobile, or tractor/trailer
   • Manipulation of rigid objects, for example, fingers in rolling contact with an object
2. In systems where angular momentum is conserved. Examples include:
   • Satellites and space robots
   • Gymnastic, diving, and running robots

We will mainly focus in this chapter on the control of wheeled mobile robots, which are part of a particular class of systems known as driftless systems, which we define later. These systems are examples of underactuated systems that are not linearly controllable according to Definition 13.3 in Chapter 13.

We first discuss the notion of nonholonomic constraints and nonholonomic systems, which ...