Increased safety for direct drives

Increased safety for direct drives

Hollow shaft, multi-turn, safety: the new motor feedback systems in the SES/SEM product family from SICK

Excellent dynamic performance, low inertia, gearless operation, and long service life are just four of the benefits
OEMs are looking to achieve when they install direct drives in their machines.
Rotative direct drives are the optimal choice for applications, with fast
cycles and very high standards for positioning accuracy in particular. With its
new motor feedback systems in the SES/SEM 70 and 90 series, SICK is now also
introducing safety technology and built-in direct multi-turn to the world of
direct drives.

Within state-of-the-art
production processes, close interaction between man and machine continues to
progress, creating opportunities for human-robot collaboration within a
cyber-physical working environment. As we see the boundaries between automation
and workers becoming more and more blurred, brand-new options for interaction
are opening up. However, all of this comes with a whole host of questions relating
to safety that we have not needed to
consider before now. The only way to provide personal protection within a
production setting that no longer
involves fixed safety fences or cordoned-off areas
is to introduce reliable safety technology with fast response times.

SICK envisions new applications
for the hollow shaft variant in the SES/SEM 70 and 90 series, primarily to be
within the field of torque motors and rotary tables as well as in the diverse
area of direct drives within robot applications, injection moulding machines, woodworking centres, semiconductor technology, and handling

No battery buffer

The new SES/SEM 70 and 90 motor
feedback systems are available in a singleturn
and multi-turn variant, which marks true innovation on the market. Rather than
relying on a revolution counter with a battery buffer to measure revolutions,
SICK has integrated a gear mechanism into the encoder for this purpose, which
is hugely beneficial regarding both
installation and maintenance. For one thing, the SES/SEM system does not
require an additional power supply through the battery buffer of the connected
drive. This cuts back on the wiring
required, as there is no need for a cable between the drive and the motor
feedback system.

The significant benefits
afforded by the lack of the battery buffer are also particularly evident during
operation. Once batteries reach the end of their life cycle, they inevitably
have to be replaced, which is costly and necessitates machine downtime. By
cutting out this step, the availability and productivity levels of the whole
machine will increase, while material and
staffing costs associated with monitoring and maintenance will drop.

The SICK solution instead
transmits the revolutions recorded by the mechanical multi-turn, along with
positioning information to the connected drive via the HIPERFACE interface. The
mechanical multi-turn can capture up to 4,096 revolutions. The motor feedback
system is installed directly on the motor shaft, without the need for extra
strap connections or mechanical couplings. The entire system has an impressively
long service life with fewer wear and
tear parts, rendering it maintenance-free.

Functional safety

With the view
ofmeeting requirements for safety
technology, SICK is currently working toward achieving functional safety
certification in line with Safety Integrity Level 2 (SIL2) under EN 61508 and
Performance Level d (PLd) under EN ISO
13849 for the new HIPERFACE devices within the SES/SEM 70 and 90 product
family. These motor feedback systems have been designed specifically for
rotative direct drives (such as torque motors), opening up new opportunities
for configuring machines with direct drives and safety technology with relative
ease. SICK supplying the new encoders with certification
will make life easier for machine manufacturers performing final acceptance on
a system as far as safety technology is concerned.

In terms of different motor sizes, SICK is providing the new
hollow shaft encoder for direct drives with shaft diameters of 25 millimetres (SES/SEM70 model) and 50 millimetres (SES/SEM90 model). The smart size of the hollow shaft encoder with HIPERFACE
interface is keeping with the current
trend of manufacturing machines and systems that are as compact as possible.
The motor feedback systems are suitable for hollow shaft motors operating at
high speeds. The SES/SEM70 can be used up to a maximum speed of 8,500 rpm,
while the SES/SEM90 is compatible with speeds of up to 6,000 rpm.

From a functional point of view,
the motor feedback system is based on capacitive
measurement principle with holistic sensing. The core element of the SES/SEM
product family is the bearing-free sensor element, consisting of a sender and
receiver printed circuit board and a sinusoidal rotor. The rotation of the
rotor, which is installed on the motor
shaft, alters the dielectric between the sender and receiver printed circuit
board. The change to the electric field is converted into sine-cosine signals
and transmitted to the drive via the HIPERFACE interface.

The holistic sensing is
incredibly robust and resistant to dust, moisture, and mechanical influences in
comparison to optical systems with ball bearings, code disks, and light
sources. Regarding control quality, the
new motor feedback system features a finely resolving track with 32 sine-cosine
periods per revolution (SES/SEM70) or 64 sine-cosine periods per revolution
(SES/SEM90). The hollow shaft diameter of 25 millimetres or 50 millimetres
allows for cables, cooling lines, and other connections to be fed through the motor shaft with ease. When
designing machines, this property offers unprecedented levels of flexibility,
which can be beneficial within collaborative robot applications, for instance.

The motor feedback systems in
the SES and SEM product family are quick and easy to install without the need
for any special adjustment tools. Just attach and rotate them, and you are good
to go. Once a system is installed, the
SOPAS software can be used to check the position of the rotor, which can be
used to ensure correct attachment directly. This
is a reliable way of identifying installation errors before delivery of the


Direct drives are currently an
undeniable trend in the field of electrical
drive technology. The countless reasons behind this include their long service
life, increased immediacy, lack of backlash, energy efficiency, and compact
design. Having identified this trend early, SICK decided to develop motor
feedback systems for torque motors and linear drives. Mechanical multi-turn and
safety technology has been added to the
properties of the new SES/SEM70 and 90 product family, allowing SICK to deliver
a full portfolio of motor feedback systems with HIPERFACE interface for direct

Written by: Kathrin Kritzer,
Motor Feedback Systems/Motion Control Sensors Product Manager, SICK STEGMANN
GmbH, Donaueschingen

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