Gap control for a proportional floating vacuum pad
In this article, a new proportional pneumatic floating vacuum pad is developed and constructed. There are two features concerning this new vacuum pad. The first is the inclusion of a proportional solenoid, which enables the continuously variable control of the suction force output. The floating mechanism design between the vacuum pad and the work-piece is the second feature, which is more preferable in real industries because it can protect the surface of the work-piece from scratches or other damage. Moreover, in addition to the open-loop gap control mode, two closed-loop gap control schemes are proposed in this paper. The first is the constant gap control. A preset gap is input to the controller as the command input that further drives the proportional solenoid to maintain a steady-state gap between the vacuum pad and the work-piece. In the second control approach, the gap between the vacuum pad and the work-piece is kept as large as possible to minimize the energy consumption. Both closed-loop control schemes are successfully implemented in this study.