Environment sensing and modelling, path finding and position location for a mobile robot
The results of previous research into mobile robotics were
studied and several fundamental properties deduced. These
were then considered in detail and optimum techniques
selected for implementation on a prototype mobile robot.
Several constraints were placed .on the prototype mobile
robot, such as the potential for untethered use (i.e. no
umbilical connections) and minimum restrictions on the
The investigation was concentrated in four main areas:
environment modelling, path selection and following,
absolute position location and environment sensors. An
initial simulation was implemented on a mainframe computer
which used an x-Y grid square model of the environment with
a simple scanning rangefinder, to investigate the usefulness
of the Means-end path finding algorithm. Results were
obtained for varying states of the environment (i.e. known,
unknown and partially known) which indicated that the path
finding algori thm was sui table for implementation on the
prototype mobile robot.
An improved environment model which used a quasi-continuous
X-Y cartesian coordinate system was then constructed. This
was designed to enable environment data from the simulated
or prototype scanning rangefinders to be used as input to
the control processes, wi th movement of the simulated or
prototype mobile robot as the output. In this way the mobile
robot was able to find paths using the model of the
environment and then attempt to follow them in the physical
envi ronment. Al ternati vely, the prototype mobile robot was
able to find a path through an unknown environment using
data from the rangefinder only.
In addi tion, a posi tion location process was implemented
which operated by identifying the position of known objects
in the environment by matching the distribution of three of
the detected objects agai nst the di stri bution of all known
sets of three objects. Once the objects had been identified
the posi tion of the prototype mobile robot was calculated.
The preliminary results indicated that the position could be
found using this technique but that more investigation was
required to reduce the ambiguity of the results.