2001 Volume 32 Issue 7 Pages 178-184
Water hydraulics is applied to molding press machines for chip-size-package technology. Velocity and force control are essential for molding quality. In this paper, fundamental control performance is investigated using an experimental water-hydraulic servo system. A single rod cylinder is controlled by a water-hydraulic servo valve. A spring is used to simulate the reaction force of plastic tablets under compression. Piston velocity and force are detected using an encoder and a load cell. These signals are fed back to a PI controller. Mathematical models that represent velocity and force control systems are derived. In particular, time delay of force response is modeled on the assumption of annular flow and equivalent bulk modulus. With regard to closed loop systems, a non-dimensional transfer function and a condition of no overshoot are obtained.
