DEVICES DRIVE HIGH-PERFORMANCE ACTUATION
AND FEEDBACK SYSTEMS
By Stefan Vorndran and Scott Jordan,
PI (Physik Instrumente) L.P.
In a similar vein, these motion control technology
advancements are also driving the laboratory research
market, where swiftly advancing scientific endeavors
necessitate ever finer and faster motion control. Innovative
electromechanical actuation and feedback technologies are
driving the development of very high-resolution microscopies,
single-molecule biophysics investigations, and the latest
materials and photonics.
Engineers have access to a wide range of precision
motorized positioning systems that provide very few
limitations on travel, precision, repeatability and speed. This
article will familiarize you with some of the commonly-used
types of motorized precision positioning systems.
Motorized linear actuators are high-precision positioning
devices that create motion in one degree of freedom. They
typically do not include a guiding system for the payload.
While electrically-driven actuators draw the most interest,
micrometer-driven actuators are also common, along with
screw-driven, pneumatic and hydraulic variants for lower-precision applications.
By attaching a linear DC motor (which can be thought of
as a rotary DC motor sliced lengthwise and laid flat) to linear
guidance and an output shaft, direct linear actuation of very
high speeds can be achieved. Linear DC motors can have a
multitude of north/south magnetic pairs, depending on how
much travel is needed. These serve the role of the stator
in a rotary motor. Gliding along them to generate force is
a three-phase coil assembly. The phases are commutated
electronically to generate smooth motion in the desired
direction, ensuring long life.
A related type of linear actuator is driven by a voice coil
motor – a nested pair of cylindrical electromagnetic coils
which attract or repel each other along their mutual axis.
These provide travels on the order of 25 mm and provide
high speeds and accelerations for small loads. Such
mechanisms are very long lived. Voice coil actuators (see
Figure 1) can offer impressive step/settle times owing to their
high responsiveness, and their direct actuation of the motion
shaft in its low-friction bearings offers exquisite force control,
Rapidly evolving production processes have driven the need for motion control systems that
provide higher accuracy, speed, resolution
and repeatability. In response, motion
control manufacturers have unleashed
a number of mechanisms, position
and force feedback technologies, and
electromechanical actuation technologies.
Together, these innovations are enabling
new actuation and feedback systems for
mission-critical deployment in automation,
laser processing, optical inspection,
photonics alignment, semiconductor
metrology, and medical device and micromachining applications.
Figure 1. A voice-coil linear motor actuator has integrated high resolution position
and force sensors, for automation applications. Image source: Physik Instrumente