Actuators, and corresponding methods and systems for controlling such
actuators, provide independent lift and timing control with minimum
energy consumption. In an exemplary embodiment, an electromechanical
actuator comprises a housing, first and second electromagnets rigidly
disposed in the housing and separated from each other by an armature
chamber, an armature disposed in the armature chamber and movable between
the first and second electromagnets, an armature rod rigidly connected
with the armature and operably connected with a load, at least one first
actuation spring biasing the armature in a first direction, at least one
second actuation spring biasing the armature in a second direction, and
one fluid-operated spring controller capable of controlling the position
of the first-direction end of the at least one second actuation spring.
The spring controller allows the actuation springs at their least
compressed state and the engine valve closed when engine power is off.
The spring controller may also be adjusted, with a low or moderate
control fluid pressure, to allow the engine valve to operate with a
partial lift.