Communications and Control

This chapter discusses communication protocols for mobile robots. A protocol or a layer of protocol that concerns itself with the meaning of the data is usually called the application layer or application protocol. Mobile robots interact with their environments in ways that are virtually nondeterministic. A robot will interact with any given environment in an almost infinite variety of ways, and new environmental factors are often introduced to a robot long after its development has been “finalized.” The result is that the robot's software will evolve indefinitely if it is a commercial success. In many environments, it is necessary for a mobile robot to control fixed resources. For an indoor robot, these may include door openers and elevators. It is possible to put special systems on a robot such as short-range garage-door controllers, but these solutions are often problematic because of the one-way nature of the control and the limited channel capacity. A better approach in many cases is to allow the base station to control these resources for the robot(s). It is, therefore, important that the protocol be flexible enough that it supports special flag exchanges to coordinate interfacing with these systems. The exact nature of such coordination may vary from application to application, but the flexibility of the protocol eliminates this problem. One of the important aspects of a protocol is framing—the means by which the receiver/decoder determines where a new message begins. Sending each byte as two ASCII characters is a waste of bandwidth, but it ensures that the data would never cause the transmission of a byte having the value 0 Dh.