Introduction to cable parallel mechanisms
A cable parallel mechanism is a conventional parallel mechanism
whose rigid legs have been replaced by cables.
The latter are rolled up at one end (usually the ceiling) and by varying the
length of the cables, one can position and orient the
effector in space (Figure 1).
Fig. 1: A cable parallel mechanism.
The advantages and disadvantages of these mechanisms differ from those of
conventional parallel mechanisms (which are usually
two main advantages are undoubtedly the very large workspace and
the possibility to easily obtain a redundance with respect to the actuators.
One is also able to produce very large
Cable mechanisms do, however, have two intrinsic disadvantages which must be
considered. First, cables produce only tension forces (a cable
cannot push an object). Moreover, cables have a certain flexibility
which will necessarily influence the precision of the mechanism.
These mechanisms are used in several applications, mainly in cases where a
large workspace is required. The best known application is undoubtedly
the Skycam, a camera used, among other things, for
the televization of professional American football games.
Fig. 2: Camera controled by a cable mechanism (courtesy of
Fig. 3: Example of positioning in a stadium (courtesy of