Page 58 - Introduction to AI Robotics

2 The Hierarchical Paradigm

Chapter Objectives:

Describe the Hierarchical Paradigm in terms of the three robot paradigms
and its organization of sensing.
Name and evaluate one representative Hierarchical architecture in terms
of: support for modularity, niche targetability, ease of portability to other
domains, robustness.

Solve a simple navigation problem using Strips, given a world model, op-
erators, difference table, and difference evaluator. The state of the world
model should be shown after each step.

Understand the meaning of the following terms as applied to robotics:
precondition, closed world assumption, open world, frame problem.

Describe the mission planner, navigator, pilot organization of the Nested
Hierarchical Controller.

List two advantages and disadvantages of the Hierarchical Paradigm.

2.1 Overview

The Hierarchical Paradigm is historically the oldest method of organizing in-
telligence in mainstream robotics. It dominated robot implementations from
1967, with the inception of the first AI robot, Shakey (Fig. 2.1) at SRI, up until
the late 1980’s when the Reactive Paradigm burst onto the scene.
This chapter begins with a description of the Hierarchical Paradigm in
terms of the SENSE, PLAN, ACT primitives and by its sensing representa-
tion. The chapter then covers the use of Strips in Shakey to reason and plan