  The impact forces during switching operations of short-stroke actuators may
cause bouncing, audible noise and mechanical wear. The application of
soft-landing control strategies to these devices aims at minimizing the impact
velocities of their moving components to ultimately improve their lifetime and
performance. In this paper, a novel approach for soft-landing trajectory
planning, including probability functions, is proposed for optimal control of
the actuators. The main contribution of the proposal is that it considers
uncertainty in the contact position and hence the obtained trajectories are
more robust against system uncertainties. The problem is formulated as an
optimal control problem and transformed into a two-point boundary value problem
for its numerical resolution. Simulated and experimental tests have been
performed using a dynamic model and a commercial short-stroke solenoid valve.
The results show a significant improvement in the expected velocities and
accelerations at contact with respect to past solutions in which the contact
position is assumed to be perfectly known.
