Java Reference
In-Depth Information
Ability to record sensor information and build a representation of the
environment.
■
The autonomous robot is made up of a mobile platform, a set of sensors
and an onboard computer which elaborates commands and coordinates the
robot's devices. A remote control station maintains a description of the
robot environment, elaborates exploration strategies and communicates
with the onboard computer in order to receive sensory data and submit
commands to the robot. The robot control system is thus structured as a
master
-
slave system.
10.1.1
Mobile platform
The mobile platform is a four-wheeled rectangular base. The rear wheels are
mounted on a common axis controlled by separate motors (differential
drive), while the front wheels are castor wheels. The robot motion is deter-
mined by controlling the velocities of the two independent motors. Each
wheel is connected to a sensor (encoder) that measures the exact number of
rotation degrees. Figure 10.1 shows the top and side view of a typical mobile
platform. The robot's pose (
x
,
y
) and orientation (
) are represented by a
Cartesian reference frame whose origin coincides with the middle point of
the rear axis.
The onboard computer implements high-level commands that determine
the movements of the mobile platform. Table 10.1 lists the supported
commands.
θ
10.1.2
Sensors
Autonomous robots are usually equipped with a variety of sensors that
guarantee that the robot will perceive useful information in different envi-
ronmental conditions. The accuracy of the sensory measurements depends
on the sensor resolution (the minimum perceived value), the sensor position
(e.g. orthogonal to an obstacle), and the physical characteristics of the
environment (e.g. the obstacle surface is opaque). For example, lasers are
not able to detect opaque surfaces, sonars are not able to detect smooth
surfaces, and video cameras require good light conditions. In this case study
y
θ
x
Figure 10.1
The mobile platform structure
