Robot design
Several alternatives were considered for the
robot’s design, but due to space limitations only the
one selected is described herein. As mentioned in
Section 3.1, the robot has two modules, a work
module and a mobility module. In contrast to the
previous concept, presented in Ref. w8x, the work
module is aboÍe the mobility module Fig. 1.. The
previous concept was governed by the robot configuration,
which had to allow the gripper to pick up the
tiles accurately in order to set them precisely. Because
of this, the tiles had to be stored in special
magazines on a turntable. The present concept permits
a simpler design, because the accuracy of picking
up the tiles is assured by using a computer vision
system, as described in Section 4. This modification
of concept does not change the multi-functionality of
the robot, as it still has separate work and mobility
modules.
At this stage of development, it was decided to
concentrate on the autonomy of the robot only at a
workstation. Thus, the robot and the operator work
as a ‘team’, as explained in Section 3.1. As a result
of this decision, the work envelope of the robot had
to be extended in order to minimize the percentage
of the unproductive time resulting from the movement
between workstations. That extension is
achieved here by adding a rotating plate between the
mobility and the work modules. The plate enables a
908 change in the robot’s orientation each time. Once
such a turn is completed, the robot position is fixed
by means of a pin which enters a hole in the plate
designated for it. Thus, the robot’s effective work
envelope is tripled and, in some cases, even quadrupled.