Tech Briefs Magazine - June 2024 - MD8

Without dampener
With dampener
Figure 1. With smart electric actuators, instead of spending valuable time wiring, installing, and testing, you
can immediately take advantage of plug-and-play control functionalities such as force feedback. (Image:
Thomson Industries, Inc.)
be relevant to the immediate application.
Without electronics, system designers are
forced to use less sophisticated measurement
techniques, like calculating pressure
from changes in current flow at a pump.
Adding force feedback to a conventional
electromechanical actuator is also
challenging. This type of functionality
also typically requires redesigning the
actuator from the ground up. The manufacturer
might start with an existing
structure, but would have to make size,
shape, or other adjustments. While designers
end up with a custom solution,
getting to the solution is difficult, the
components are potentially more expensive,
and the solution is likely not easily
adapted for other applications.
Designing for future adaptation is
much easier with a smart actuator. Some
80 percent of the technology of a smart
actuator is core technology that could
be the same in multiple applications.
Leading manufacturers design this core
technology separately from the force
feedback function, utilizing a device
such as a strain gauge, a more representative
measure of pressure than perhaps
relying on current draw from the motor,
for example (Figure 1). Connecting the
strain gauge is simply a matter of plugging
in a couple of wires from the actuaFigure
2. The dampening option is mounted between
the rear adapter and the housing and allows the
actuator to absorb shock loads. (Image: Thomson
Industries, Inc.)
tor to the control system, rather than
adding complex componentry to measure
pressure in a hydraulic system.
Load Dampening
Figure 3. In situations where a machine component is stuck, breaks, or finds itself in an awkward position, an
electric actuator can be moved manually into a position that allows the user access for maintenance. A manual
brake release option disengages the holding brake so that the extension tube can extend or retract under
load and assisted by gravity to the desired position. (Image: Thomson Industries, Inc.)
8
That same core technology remains
unchanged when used to provide load
dampening. The ability to withstand
shock loads has long been the purview of
hydraulics. The incompressibility of the
hydraulic fluid helps absorb shock and
prevents the vibration from damaging all
other system components. Fortunately, it
is now possible to add this shock dampener
to an electric actuator without
needing to change the core structure.
A dampener can be attached to an
adapter on the rear of the actuator, adding
to the component's total length and
weight (Figure 2). This adaptation comprises
shock-absorbing washers that elastically
deform and dissipate energy in
the load path of the actuator. When the
actuator extension tube is hit with a
shock load, the attached dampener extends
or compresses, depending on the
direction of the shock load force, and
then returns to its original position.
The travel distance depends mainly on
the power of the shock itself, but load
size, temperature, shock load speed and
mounting position also affect it. The
dampening adapter prevents positive and
negative shock loads from acting on the
other mechanical components of the
thrust assembly, including the ball nut,
Motion Design, June 2024

Tech Briefs Magazine - June 2024

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