Tech Briefs Magazine - December 2022 - MD8

Enhancing Design Efficiency
in Linear Motion
Automation
Integrated measuring systems for linear motion simplify design,
improve precision, and eliminate maintenance.
A
s linear motion systems continue
to advance, new solutions
are emerging that enable both
system designers and end users to
realize benefits such as simplified
assemblies, greater precision, and
zero maintenance. One such solution
is the integrated measuring system
(IMS), which has demonstrated notable
cost savings and improved design
efficiencies in linear motion automation
applications.
To fully benefit from this solution, it
is essential to understand how the IMS
works and keep in mind key considerations
when working with it.
Understanding IMS
An IMS uses the inductive measuring
principle to place the linear encoder
inside the linear guide rail so that
both guiding and measuring functions
can be achieved with one component.
This configuration replaces traditional
designs that relied on separate external
linear encoders and readers that
were susceptible to dirt and lubricant
contamination and breakdown. The
8
new design not only solves the contamination
issue but also improves the
precision and uptime of linear motion
systems and eliminates maintenance
altogether.
Consider a task within the automation
industry that requires placement or
positioning of a workpiece using a linear
motion axis. The basic components
needed to perform this task include a
servo controller, a servo motor with a
rotary encoder and a linear motion axis
such as a ball screw.
Traditionally, this type of system
would be designed using a semi-closed
control loop in which the required
workpiece position is communicated
from the PLC or CNC to the servo
drive. The servo drive directs the rotation
of the servo motor, and an externally
mounted rotary encoder precisely
counts the turns using the joints
of the ball screw and the corresponding
lead to position the workpiece
accordingly on the linear motion axis.
The downside of the semi-closed control
loop is that it indirectly measures
the position of the workpiece,
thereby increasing the opportunity
for mechanical drive chain or belt
positioning deviation and decreasing
precision.
Alternatively, an IMS allows system
designers to switch to closed-loop control
to overcome position errors and
improve precision. In a closed-loop
configuration, the linear encoder is
mounted in parallel to the linear guideway
to measure the actual position of
the workpiece. If there is a difference
between the actual position and the
required position, the servo drive corrects
any position error; therefore, this
approach removes error from the drive
chain or belt.
These systems are currently available
using inductive measuring and magnetic
measuring principles. Compact models
for magnetic measuring offer robust
performance and economy for applications
that include automatic positioning,
handling, and axes with linear motors.
Larger systems for inductive measuring
are also exceptionally robust and deliver
greater precision for applications such
as machine tools.
Motion Design, December 2022
Tech Briefs Magazine - December 2022

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