Actuators and corresponding methods and systems for controlling such
actuators offer efficient, fast, flexible control with large forces. In
an exemplary embodiment, an fluid actuator includes a housing having
first and second fluid ports, an actuation cylinder in the housing
defining a longitudinal axis and having first and second ends in first
and second directions, an actuation piston in the cylinder with first and
second surfaces moveable along the longitudinal axis, a spring subsystem
biasing the actuation piston to a neutral position, a first fluid space
defined by the first end of the actuation cylinder and the first surface
of the actuation piston, a second fluid space defined by the second end
of the actuation cylinder and the second surface of the actuation piston;
and a flow bypass that short-circuits the first and second fluid spaces
when the actuation piston is not proximate to the second end of the
actuation cylinder. A first flow mechanism controls fluid communication
between the first fluid space and the first port, whereas a second flow
mechanism controls fluid communication between the second fluid space and
the second port. The first flow mechanism is always wide-open, whereas
the second flow mechanism is open and closed when the flow bypass is
closed and open, respectively. The system is able to latch the actuation
piston at its second direction end position while making it possible for
the actuation piston not to dwell at its first direction end position,
thus reducing the overall actuation time.