Behavior-Based Indoor Navigation - Ambient Intelligence for Scientific Discovery - page 268

SORGIN

module

SORGIN
module

Remote host or

Robot host 2

(Player client)

SORGIN
module

(Player client)

SORGIN

module

player
device

Player

player

device

Robot host 1

Linux Kernel

Hardware

Fig. 1. SORGIN and Player combined software architecture.

The environment where the robot moves is a typical oce-like semistructured
environment, with rectangular halls connected by corridors, full of geometrical
properties and natural landmarks that can be intelligently exploited (Fig. 7).

3.1 Wandering in a Preferred Compass Orientation
The robot needs to move around in order to interact with the environment. The
basic movement behavior is obtained by combining two simple modules:
- Left and right free space balancing for corridor following that allows the
robot to smoothly traverse corridors and halls. Here, rotational velocity is
defined using the difference between left and right side sonar readings, and
translation is dependent on the front sonars. This behavior acts also as an
obstacle avoider when the obstacles are within the perceptual range of the
sensors.
- Follow a desired compass orientation, a simple proportional control that di-
rects the robot through the path defined by the compass orientation. In order
to allow the robot to turn on the spot when it has free space around. The
translational velocity is an inverse exponential function over the difference
between the desired and the actual compass orientations.
Each module outputs translational and rotational velocity values and the final
output motor command is simply the weighted sum of both modules. The be-
havior produced by the combination of these two modules is more than a simple
wanderer as it directs the robot to the goal defined by the orientation avoiding
collisions at the same time. The desired compass orientation acts as an attractor
when there is sucient space for the robot to move safely, thus adding persistence
to the global behavior.

3.2 Landmark Identification Subsystems
For goal oriented navigation, the robot needs more knowledge that must be
properly combined with the capability of wandering in a preferred compass ori-