Page 336 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

328 CHAPTER 13 Communications
13.4.4 Ethernet..............................................................................................................366 13.4.5 Universal serial bus .............................................................................................. 367 13.4.6 Protocolconverters...............................................................................................368
In this chapter, the subject of data communications as it relates to electronic communication with sensors delivered by a remotely operated vehicle (ROV) will be addressed. This is a very important topic for underwater vehicle control and utility. The entire purpose of the underwater vehicle is to deliver a sensor or tooling package to a work location to perform work of some type or to sense the environment. In order to place the vehicle there, it must be controlled through the use of instruc- tions transmitted to the vehicle, which are based upon data received from the vehicle’s sensors. The constant flow of data and instructions from/to the vehicle and its sensors allows the operator to complete the task safely and efficiently. In two-way communications between humans, it is some- times stated that “it does not matter how you say it as ong as it is understood.” But the easy flow of interpersonal communications does not measure up to the exacting requirements of intelligent machine communications.
13.1 Overview
13.1.1 What is communication?
Imagine yourself in a room where everyone is talking simultaneously in a different language. Is communication taking place (probably not)? Will communication take place if only one person spoke at a time but still in a nonhomogeneous language? How about one person speaking in a com- mon language, only with a different dialect (to better understand this concept, imagine a Bostonian traveling to the bayous of southern Louisiana and ordering lunch!)? Try listening to a speaker who is lecturing in a very slow or rapid manner. College professors are notorious for speaking in low tones while facing the blackboard and writing unintelligible signs using undefined terms—and the profes- sor is shocked when students fail the subsequent test because of a basic failure to communicate.
Communications between spouses, organizations, governments, civilizations—and machines— require a common set of protocols in order for messages to be transmitted, received, and under- stood. For communication to take place, ideas must be conveyed using commonly accepted symbols (speech, body language, data, or other acceptable forms) through some common medium at a rate and with a delivery format that allows these symbols to be both transmitted and received for information dissemination. This is applicable to people, animals, and intelligent machines.
13.1.2 Evolution of data communication
Speech evolved over millennia, eventually allowing for direct human communication over short distances. Technology further allowed humans to communicate over vast distances through the use of differing mediums. Native Americans made use of the smoke signal, tribes in Africa used drums, sailors used flags as well as signal lamps, and church bells signaled the faithful to service (or slow