MOBILE ROBOT

The essential components for a mobile robot include environment sensors,
navigational intelligence and actuators (wheels or legs). The mobile robot to be
developed in this project incorporates ultrasonic proximity sensors input devices as
environment sensors and two motors (which control the wheels) as actuators. The
main goal of this mobile robot is to avoid collisions with obstacles or walls and plan
its paths around them for subsequent runs.
A transmitter-receiver pair is used for the ultrasonic sensor circuitry. The transmitter
mainly consists of a 555 timer and is controlled by an external device
(microcontroller) to initiate pinging sequences. The receiver is primarily made up of
LM741 Op-Amp, LM567tone decoder, and LM311 comparator. The LM741 is used
to amplify the received signal while the LM567 is used to filter and detect only the
preset frequency. The LM311 comparator is used to minimize false triggering
emanating from power surges in the supply current.
An H-bridge circuit is used to control the motors' forward/reverse motion via its 2 bit
binary inputs at its strobes. The H-bridge circuit utilizes Darlington-Pair transistors
and diodes to control the forward/reverse current flow to the motor.
A PIC16F84 microcontroller is used as the brain of the mobile robot. The main
function of the microcontroller is to initiate ping sequences to the ultrasonic
transmitter, measure the time for the ping echo to return, and decide to move
forward, turn or reverse the robot accordingly. Extended functions of the
microcontroller is to create a 2Dterrain map, and plan its path to any specified target
point. These are to be achieved by Voronoi Diagram or Delaunay Triangulation
method for mapping, and a combination of one or more of the Dijkstra, Bellman,
Ford, Moore, Johnson, Floyd-Warshal, or A* algorithms for best path calculation.
In some parts of the project especially the intelligent navigation algorithms, the
author encountered many new ideas and theories which the author cannot fully
understand. It is hoped that future projects will emphasis on these areas.