The original construction of the robot chassis [12] included a form of ‘‘suspension’’.
The motor and wheel assembly at each corner of the chassis was mounted on a
single shaft that allowed one degree-of-freedom between it and the chassis about the
longitudinal axis. As shown in Fig. 1(a) there was no mechanism designed to limit or
control this degree-of-freedom and, once constructed, left a free moving joint. The
two side assemblies at either end were subsequently linked via a piece of thin tubing
in an attempt to limit and effectively prevent movement of the joints. A pair of
springs had been added in an attempt to stiffen the setup further.
Some investigations were made into the system and it quickly became apparent
that movement about the free axis was completely undesirable as it would allow the
sides of the hub to foul the ground. Movement of this form would also affect the
motion of the Mecanum wheel, as the sideways force vector generated would work
directly against the ‘‘suspension’’. When the wheel pivoted it would alter the current
contact patch, thus altering the dynamics of the system. Early testing of the platform
using the prototype driver board found this temporary solution unsuitable as it
collapsed after only a short period of operation. The robot was to be used on level