26-07-2012, 02:31 PM
Implementation of Obstacle Avoidance and ZigBee Control Functions for Omni Directional Mobile Robot
Implementation of Obstacle Avoidance and ZigBee.PDF (Size: 1.93 MB / Downloads: 40)
Abstract
Based on FPGA (field programmable gate array)
development board, this paper presents the obstacle avoiding and
ZigBee wireless control functions for omni directional mobile
robot. By using ultrasonic transducers, the embedded controller
receives the obstacle distance signals, and then calculates the
control signals to drive three omni directional wheels DC motors
which set up on mobile robot. On the other hand, through the
onboard RS-232 port, the controller as well as receives the control
signals from remote PC via ZigBee wireless communication. The
graphical human machine interface is programmed by Visual
Basic software at PC part; such the functions of mobile robot
remote control and messages transmission are displayed on screen.
The experiment results provide the FPGA implementation
techniques for control omni directional mobile robot; also extend
the ZigBee wireless communication techniques into the intelligent
robot research field.
Keywords- omni directional mobile robot, obstacle avoiding,
ZigBee wireless communication
I INTRODUCTION
Mobile robots perform various ways of tasks to serve
humans such as home robot, inspection robot, security robot,
school education robot, rehabilitation robot, and so on. The
conventional mobile robots have used front-steering and rearwheel
driving mechanism to response all needed robot
motions, but the motion restriction is a major problem in the
use of such mechanism. The omni directional configuration is a
most suggested mechanism for mobile robot, which to have the
capability of changing directions within the limited space in the
indoor environment [1-3]. To achieve a real-time control and
provide high speed with an acceptable error in the omni
directional mobile robot (ODMR), the field programmable gate
array (FPGA) based controller has been widely used by the
robotics community [4-6]. Otherwise, the wireless home
networking technology can be categorized into wireless LAN,
Bluetooth and ZigBee. As table 1 shows [7, 8], the ZigBee has
advantages such as low power consumption, large transmission
range, and capability of mesh networking, which are more
suitable for sensor network applications than other wireless
alternatives.
Based on above points, this paper presents an integration of
ODMR obstacle avoiding function and ZigBee control
function, which are implemented on an FPGA development
board. A case study of three active omni directional wheels
was configured to realize the all-round movement mobile robot.
Moreover, by combining ZigBee technique with Visual Basic
(VB) programming language, a graphical human machine
interface was used to remote control the ODMR movement to
reach the desired location.
TABLE 1 Wireless technology comparison.
Bluetooth ZigBee WLAN
Speed 3 Mbps 20~250 kbps 54 Mbps
Price 3 US$ 2 US$ 5~10 US$
Power Consumption medium Lowest Highest
Distance 10~100 m 30~300 m 30~70 m
frequency range 2.4GHz
868 MHz
915 MHz
2.4 GHz
2.4/5 GHz
IEEE Standard 802.15.1 802.15.4 802.11
II PRACTICAL FABRICATION OF ODMR
The components of ODMR are divided into: body structure,
feedback sensor, control circuit, driver mechanism, control
program, and ZigBee wireless transmission modules. It is
obvious that the ODMR covers a wide range of research fields,
and which provides high integration techniques in both theory
and practice
A. Robot Architecture Design
In the design of robot body, it aims to allow the robot to
move around all positions. Based on literature review [9, 10],
the structure of chassis is designed in consideration of the
streamline of the robot body and convenience of controller
production. As shown in Fig. 1, the wheels need to be specially
designed to meet the function of omni directional movement.
The kinematics equation deduced by this system is as
follows:
y
x
cos( ) sin( ) L
-sin( - ) -cos( - ) L
-sin( ) cos( ) L
R
1
m
m
3
2
1
⎥ ⎥ ⎥
⎦
⎤
⎢ ⎢ ⎢
⎣
⎡
⎥ ⎥ ⎥
⎦
⎤
⎢ ⎢ ⎢
⎣
⎡ + +
=
⎥ ⎥ ⎥
⎦
⎤
⎢ ⎢ ⎢
⎣
⎡
φ φ φ
δ φ δ φ
δ φ δ φ
θ
θ
θ