5

2.BACKGROUND

This chapter presents the background information required to understand later chapters in the

thesis.

First, important definitions are introduced.

Previous related work isthen reviewed,

followed by a description of the underlying control representation on which our balance control

approach is based. Finally we describe our animation system and our biped models.

2. 1

Definitions

A number of important terms and acronyms are used throughout the thesis.

Their definitions and

descriptions can be found in Appendix A. The majority of the terms are commonly used terms in

the robotics and biomechanics literature.

[SV89], [Fr86] and [IRT81].

More in-depth information can be found in [HR86],

2. 2

Previous Work

Bipedal locomotion is a topic of interest to a number of disciplines.

This section describes a

representative subset of the work in these fields.

First, we provide an overview of the various

approaches to motion generation in computer animation.

This is followed by discussion of work

specific to bipedal locomotion in computer animation, biomechanics and robotics.

relevant work in the control literature is addressed.

Finally, some

2. 2. 1

Kinematic Animation

Research in computer animation has evolved significantly in its relatively short life span.

The

earliest

approaches

to

computer

animation

use

keyframing,

a

technique

based

on

classical

animation.

In keyframing, the configuration of the animated objects at various points in time is

specified by the animator and the computer generates the in-between frames using linear or other

forms of interpolation.

In early systems, specification of keyframes required the animator to