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Nov 14, 2013 (3 years and 6 months ago)

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Technical feature

Thursday, 14 November 2013


The

world’s first three
-
phase linear motor designed as an actuator


The world’s first three phase linear motor designed specifically as an actuator overcomes all

the traditional problems associated with pneumatic, ballscrew and
traditional U
-
channel or
flat bed
linear motor technology
. Users also gain the cost and service benefits associated
with harmonising technologies under a single supplier.


All that has now

changed forever with the launch of the direct drive ServoTube actuator from
Copley Controls. A fast, clean, simple, rugged and inexpensive solution, ServoTube is the
first three phase linear motor designed specifically as an actuator.


In the past, actua
tors based on linear motor technology have only had limited success
, their
use being restricted to high precision applications
. There are two problems. Firstly,
conventional
U
-
channel and flat bed
linear motors
have
dirt collecting channels and grooves
tha
t become clogged in factory floor use. Secondly, the need for an external encoder has
made them too expensive for widespread use.


Copley’s engineers have overcome the first challenge by developing a hermetically sealed
tubular construction that is inheren
tly compatible with actuator operation. Magnetic drive coils
are contained within the metal enclosed forcer, while the motor’s permanent magnets are
hermetically sealed in the cylindrical thrust rod. Using internal Hall effect encoders has
solved the secon
d problem.




The result is a single
-
vendor, inherently programmable solution that has better controllability
than pneumatics, higher speed than ballscrews and superior reliability to belt drives.


ServoTube’s motor forcer contains the motor’s electrical
ly powered drive coils while the
thruster is a 25mm diameter stainless steel actuation tube enclosing rare
-
earth permanent
magnets. Interaction between the forcer’s travelling magnetic field and the thruster’s fixed
magnet field sets up a magnetic force th
at drives the thruster. The ServoTube forcer is a
rugged IP67 rated enclosure that houses the position sensing Hall devices as well as the
drive coils.


Integral Hall position sensing develops high accuracy position sensing in response to the
precise fiel
d patterns. The result is 12 micron repeatability. Not only do these sensors bring
an immediate cost reduction, but also they do away with the need for the time consuming set
up and alignment procedures associated with conventional external encoders.


Easy

to configure


Because of its Windows
-
based Copley Motion Explorer 2 (CME2) software, ServoTube is
also easy to configure. Using CME2, ServoTube can be optimised for a range of factors such
as speed, position and defining shutdown procedures. The program c
an also be used to set
motion profiles. A PLC or row of switches can then be used to automatically trigger these
pre
-
programmed profiles. While CME2 does support other vendors’ rotary or linear motors,
Servotube comes with preconfigured motion profiles and

an automatic tuning procedure to
make installation and use even more straightforward.


The motion profiles themselves are defined by a Xenus line powered indexer. This can
define indexes, change parameters, handle I/O or create sequences of indexes and
c
ommands. Any parameter can be assigned to a register, allowing on the hoof adjustment
from a master controller. Clear diagnostics and advanced oscilloscope tools simply system
commissioning, while autophasing automatically compensates for crossed encoder l
ines or
mis
-
wired Halls and motor phases.


Xenus indexers plug in to 50/60 Hz at 120 or 240VAC, dispensing with the bulk and cost of a
separate DC power supply. ServoTube continuous force ranges from 51N to 104N (11.2 to
23 LB), with a peak of 662N (146 LB
). The actuator attains a maximum 527 m/s
2

acceleration, and 6m/s velocity, all at resolution down to 12 microns.


Paired with a matching Xenus indexer, ServoTube actuators makes a complete low cost
positioning subsystem for stacking, cutting, pressing, co
ating, filling, picking and placing.
Neither pneumatic nor hydraulic lines are needed. For maximum simplicity, an external multi
-
position thumbwheel switch can call up Xenus’ stored motion profile. At the opposite
performance extreme, ServoTube will execut
e CANopen positioning profiles transmitted to
Xenus via CAN bus.




Multi
-
axis operations


The simple 2 wire CAN interface is reliable and cost effective for industrial application, by
implementing the CANOpen higher level protocol communications in thei
r drives Copley
Controls use process data objects (PDO) and service data objects (SDO) to communicate
between nodes.


A PDO is used to communicate between the drives in a distributed control architecture. An
intelligent Copley Controls drive will close
any control loops, tightly synchronising axes. If
more axes are required, another drive is simply added to the CANOpen bus without the need
for an additional controller or breakout box. An SDO can be used to configure drive
parameters on
-
the
-
fly from the

network, managing start
-
up and reducing changeover times in
batch operations.


Two drive modes are available for motion control, depending on the application. The first is
Profile Mode, which is ideal for simple pneumatic
-
type positioning applications.

In profile
mode, the CPU broadcasts a command to the network with move distance, velocity and
acceleration to control a point
-
to
-
point movement. Because the command is broadcast to all
nodes on the CANOpen network, multiple axes can be controlled simulta
neously.


Of course, linear motors are capable of much more sophisticated dynamics, using the
second, PVT mode, multiple
-
axis contouring is possible. When contouring, the CPU issues a
series of points defined by position, velocity, time (P,V,T). Each dri
ve then uses cubic
polynomial interpolation to create a best
-
fit curve, resulting in smooth linear actuation in the
most complex manoeuvres.


Copley provide powerful motion libraries for C++, to simplify programming motion objects are
also available that c
an be used in Visual Basic, Labview or .Net applications. These libraries
are powerful because they are designed specifically for multi
-
axis motion applications. For
example, axes that must be coordinated can be controlled by grouping axes together in a
single programming object. That object can then be commanded to move to an x,y,z
coordinate, and the
PVT data will be automatically generated to control all three axes. This
vastly simplifies motion programming for the OEM.



Simple installation


Redes
igned as the ServoTube actuator, linear motors not only shed their encoder, but also
work with low cost full length industrial bearings. Freed from the need to align a precision
encoder, ServoTube actuators install as easily as pneumatic actuators. Compati
bility with
pneumatic actuator fittings adds application diversity. Eliminating these complexities, and
substituting simple bearings for precision linear motor bearings enables ServoTube to
compete not only on performance, but on price as well.


The Servo
Tube integral bearings also wipe the thrust rod clean with each stroke, further
improving robustness and prolonging operational life. The actuator’s embedded Hall position
sensor provides a clear operational advantages by eliminating the possibility of deg
radation
from tarnishing or soiling, or damage by physical contact


a real consideration in factory
floor environments.


The ServoTube motor’s cost and performance superiority is most pronounced in modern
short run production, where product specification
s vary from batch to batch. Programmable
position control


at which the ServoTube excels

rather than the unvarying fixed or ‘bang
-
bang’ actuation of pneumatic actuators, is key to production efficiency.


As a result, ServoTube actuators provide the speed,

programmability and precision needed
for today’s short production runs, variable duty cycles, and harsh factory floor environments.
Solid state control plus minimal parts count provides a distinct advantage over traditional
pneumatic, lead screw and belt
drive mechanisms. Typically uses include stacking, cutting,
pressing, coating, filling, picking, placing and related automated functions.


For more in
formation visit
www.copleycontrols.com


Or contact Bill Lu
ckin,
Tel: (
01268
)

287070

Fax:
(01268
)

293344

Email:
info
@copleymotion.com



Copley Motion Systems LLC

Luckyn Lane

Pipps Hill

Basildon

Essex

SS14 3BW


About Copley Controls Corp.


Copley Controls Corp. i
s a worldwide leader in high power amplifiers and high performance
motion solutions for OEMs in the semiconductor, medical, pharmaceutical and automated
assembly/inspection industries. Headquartered in the US with a division in England

(Copley
Motion Syste
ms LLC)
, Copley Controls has 20 years of experience in OEM partnerships. Our
global commitment is backed with sales offices and local technical support in the US, Europe
and Asia.


Press Contact:


Robin Wolstenholme

Tel: (01306) 882288

Fax: (01306) 881803

Email:
r.wolstenholme@ballard.co.uk