9.1 Introduction

The preceding chapters have described the fundamental principles of strapdown navigation systems and the sensors required to provide the necessary measurements of angular rate and specific force acceleration. In this chapter, aspects of strapdown system technology are discussed.

9.2 The Components of a Strapdown Navigation System

As indicated in the earlier discussion, a strapdown inertial navigation system is basically formed from a set of inertial instruments and a computer. However, for reasons which will shortly become clear, such a system may be sub-divided further into the following component parts:

• instrument cluster;

• instrument electronics;

• attitude computer;

• navigation computer.

These components, which form the basic building blocks of a full strapdown navigation system, are shown schematically in Figure 9.1. These units will be mounted in a case, together with the necessary electrical power supplies and interface electronics, which may then be installed in a vehicle requiring an on-board navigation capability. Whilst it is often assumed that the unit will be fixed rigidly in the vehicle, it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive.

Figure 9.1: Strapdown inertial navigation system building blocks

Whilst we are primarily concerned here with the implementation of a full inertial navigation system, applications arise in which the full navigation function is not required. For example, in some short range missile applications, inertial measurements, typically of angular rate and specific force, are required purely for flight control...