Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

14 Chapter 1 Motor and Motion Control Systems
Figure 1-15 Flexible shaft couplings
adjust for and accommodate
parallel misalignment (a)
and angular misalignment
between rotating shafts (b).
Figure 1-16 Bellows couplings
(a) are acceptable for light-duty
applications. Misalignments can
be 9º angular or 1⁄4 in. parallel.
Helical couplings (b) prevent
backlash and can operate at constant
velocity with misalignment
and be run at high speed.
The structure on which the motion control system is mounted directly
affects the system’s performance. A properly designed base or host
machine will be highly damped and act as a compliant barrier to isolate
the motion system from its environment and minimize the impact of
external disturbances. The structure must be stiff enough and sufficiently
damped to avoid resonance problems. A high static mass to reciprocating
mass ratio can also prevent the motion control system from exciting its
host structure to harmful resonance.
Any components that move will affect a system’s response by changing
the amount of inertia, damping, friction, stiffness, or resonance. For
example, a flexible shaft coupling, as shown in Figure 1-15, will compensate
for minor parallel (a) and angular (b) misalignment between
rotating shafts. Flexible couplings are available in other configurations
such as bellows and helixes, as shown in Figure 1-16. The bellows configuration
(a) is acceptable for light-duty applications where misalign-