There are a number of problems that can be experienced in sanitary seal applications, many of which are related to thermal and chemical resistance challenges, compression set (permanent deformation), and high static friction (stiction
In particular PlantESP simplifies the identification of common mechanical issues such as Stiction
, reoccurring loop interaction and PID controller tuning challenges.
Among these nonlinearities, we can mention the occurrence of the grip and slip (stick-slip) phenomenal on the valve stem due to static friction (stiction
) between its moving parts.
The term stiction
has been used to define this phenomenon, in which the valve is stuck due to static friction.
Data-driven modeling of control valve stiction
using revised binary-tree structure, Industrial & Engineering Chemistry Research 54(1): 330-337.
According to the help document of ADAMS, the boundary between static friction and dynamical friction is effected by the parameters of stiction
transition velocity and maximum stiction
The sloped portion of the saw tooth actuation is what provides the motion; the rapid retraction breaks the stiction
of the coupling and the actuated element does not retract with the piezo ceramic element.
The equations of motion for the system with the clutch ([J.sub.2] and [J.sub.3]), either in stiction
(sticking) or sliding are derived from the free body diagram shown in figure 3 and as follows
In addition, the dithering technique has been applied to the proportional control in order to reduce the effects of stiction
and hysteresis [1-10].
For example, dry friction or stiction
is a common source of dead-zone nonlinearities in electromechanical systems, and temperature changes on the surface of these components can produce relevant variations of dead-zone effects .
Special attention has been given to clutch modeling, because the unsmooth clutch model formulation around the stiction
zone (Figure 4) can significantly affect the computational efficiency of optimization.