In this paper, we present the static and dynamic structural characterisation of a
low-mobility parallel kinematic manipulator, involving analysis of its stiffness and
vibrational dynamic behaviour. The study starts by building numerical models of the
behaviour of the manipulator to be compared to experimental measurements from a prototype.
For the case study, we consider a four-degree-of-freedom
(x, y, z, θz) manipulator
with prismatic actuators designed by the COMPMECH research group at the University of the
Basque Country. The characterisation allows the behaviour of the static and dynamic
stiffness, as well as the natural frequencies of the manipulator, to be mapped in the
manipulator workspace. These maps together with kinematic, static and dynamic constraints
lead to the definition of operational, static, dynamic and structural workspaces,
respectively. Further, we analyse the modes of the manipulator to determine dynamic
displacements, these being key in the performance in the machining tasks for which the
robot was designed.