HEIDENHAIN Measuring Technology for the Elevators of the Future

TECHNOLOGY REPORT

Traveling Vertically andHorizontally Without a Cable

HEIDENHAIN Measuring Technology for the Elevators of the Future

Traveling Vertically and Horizontally Without a Cable
An elevator cab that is not moved by cables—elevator
manufacturers are already working on turning this vision intoreality. And HEIDENHAIN provides the measuring technology thatmakes this operation safe and comfortable.
For most people, the term “elevator” means a cab that hangs from a cable and thattransports people or freight up or down. This technology has become an indispensable
part of our daily lives, and has achieved remarkable standards regarding speed,
passenger comfort, and safety. For example, cable-bound elevators in modern
skyscrapers move at speeds greater than 10 m/s and reach heights of over 400 m.
Modern measuring and control technology with rotary encoders from HEIDENHAIN
that are designed especially for elevator technology ensure particularly pleasantacceleration and braking, a smooth motion, and exact stops. As a result, passengers
barely feel the beginning and end of movement.
Also, the elevator stops so that its floor is even with the floor of the selected
destination, in order to avoid tripping. In light of the immense number of passengers
who ride in elevators every day, cable-bound elevators are one of the safest methodsof transport anywhere on the planet. Nevertheless, there are good reasons for
improving upon this successful technology.

New elevator designs for increasingly large buildings
Modern cable-bound elevators have two significant restrictions resulting fromtheir design: Due to the weight of the cable itself, it is almost impossible tofurther increase the travel heights, and as a rule, only one cab can travel up anddown an elevator shaft. This strongly limits the number of passengers that can betransported. However, the advances in the construction of large building projects
present new challenges: Architects keep striving for ever greater heights and arebuilding increasingly sweeping complexes that are visited by an ever growing
number of people—whether for living, working, or shopping, or for spending their
free time in fitness studios, movie theaters, restaurants, bars, etc. The elaborate

2construction methods and structural analysis of such buildings at the same time also drive costs higher, meaning that there
should be as much usable space as possible while simultaneously keeping traffic and operational spaces to a minimum.

With increasing passenger numbers,
conventional cable-bound elevators
require more traffic space in the formof additional elevator shafts, as well as
additional elevator systems beyond
certain travel heights.

AEF 1323 rotary encoder from HEIDENHAIN, with EnDat 2.2
interface and connections for a motor temperature sensor:
dynamic drive control in cable-bound elevators for gentle starting, continuous acceleration, comfortable and stress-free travel,gentle braking, and stopping exactly at the intended position.

In order to realize the necessary performance regarding the number of passengers as well as the distances to be coveredin such megabuildings of the future while still using the elevator technology of today, a correspondingly large number ofelevator shafts would need to be planned for, as well as additional elevator systems for further travel if the buildings exceed
a certain height. This would naturally detract from the very valuable usable space. However, since passenger capacities
are calculated based on maximum utilization, the elevators would be severely underutilized most of the time. For example,
in an office building there must be enough capacity for the large amount of traffic at the start and end of each work day,TECHNOLOGY REPORT
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whereas many fewer elevator cabs suffice during the rest of the day. That is why elevator manufacturers are looking foralternative solutions that not only do not limit the travel height, but at the same time also increase passenger capacity andeven make it flexible.

Absolute angle encoders like the AMO WMKA withexternal scanning are suited for particularly precise
position measurement on torque motors with large
diameters.

Into the future, without a cable
When looking for new approaches and solutions, one likes to weed out whatever is no longer necessary. Elevator
manufacturers are currently considering weeding out the cables in order to build cable-less elevators. This technical idea
borrows from the Transrapid, the high-speed magnetic levitation train developed in Germany, since the elevators of thefuture will be powered with the aid of direct linear-motor technology. The cab is equipped with passive magnets, and theactive stator, divided into segments, is located in the elevator shaft. By appropriately providing current to these individualsegments, multiple cabs can travel inside a shaft—independently of each other.
In addition to the vertical motion, this drive concept also permits horizontal motion. This horizontal motion makes it possible
to use this new technology for the increasingly long level distances in tall megabuildings and in sprawling but connectedbuilding complexes. After a horizontal traverse, the cab can then move up or down in the shaft of another part of thebuilding or complex.

Innovative measuring technology must rise to the challengeThis new transportation strategy requires a tailor-made measuring technology—on the one hand to ascertain the position
information in order to control the cab’s speed, and on the other hand for positioning and controlling a swivel joint whenswitching between vertical and horizontal travel. The main challenge presented to the motor control during the linear motionis the tolerance required for guideway deviations, since the control must simultaneously provide high signal quality forcontrolling the direct drive. Only excellent measuring signals reduce vibrations, permit dynamic motions, and significantly
increase the speed stability, while at the same time avoiding the generation of additional heat. Passenger comfort isanother important requirement, since the desire is for passengers to barely notice that the cab is starting or stopping. Last
but not least, the change in direction from vertical to horizontal and back must of course occur exactly, safely, and without
any jerk.

4Cable-less elevators can move multiple cabs within an elevator shaft in a highly flexible manner and can move thecabs into a horizontal shaft—not only to make room for a passing cab but also to move them between connectedbuildings.

HEIDENHAIN’s solution for these complicated requirements is the LINA 200: an inductive absolute linear measuringsystem with special properties. The absolute scale consists of two tracks with different signals periods, from which theabsolute position value is then calculated. The EnDat 2.2 interface transmits this highly accurate position value to thesubsequent electronics purely digitally. A special feature of this scale is that the two tracks are not located in one plane;
instead, they face each other. The U-shaped scale design realized for this not only makes it possible to scan the measuring
standard from both sides, but the double-walled design also protects the graduation and the scanning procedure itself
from mechanical and electromagnetic influences. In addition, this type of construction provides maximum rigidity at a lowweight. The U-shaped design also brings significant benefits regarding the mechanical sturdiness of the scale as well as thestability of the encoder signals.

TECHNOLOGY REPORT
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Newly developed linear measuring technology for the demanding control of the linear drive
The graduation carrier of the LINA 200, with an overall length of 2400 mm, is attached to the elevator cab. The scaleconsists of four segments, each with a measuring length of approximately 600 mm. These segments are scanned byscanning heads that are placed in the shaft in a cascading alignment. This permits continuous position measurement overthe entire distance traveled. Despite the generous guide tolerances of ±5 mm and ±4 mm, the LINA 200 achieves a small
measuring step of approximately 2 µm. This means that it reliably supplies highly accurate positioning signals for the drive
control of the cable-less elevator, while at the same time offering tolerances that are sufficient for permitting a real-world
mounting strategy in the elevator shaft as well as for compensating for movements of the building itself.
The LINA 200, which was designed specifically for cable-less elevators, also attains peak values regarding dynamics andpassenger comfort. Initial tests showed that traveling speeds of 6 m/s are achieved easily, and in the laboratory the LINA
200 provided reliable position values at speeds of up to 18 m/s. At slow speeds, as well as during acceleration after a stopand braking before a stop, the high resolution of the position values (18 bits) at a measuring length of approximately 600
mm ensures a very comfortable and gentle motion.

EnDat interface supplies diagnostic data
Furthermore, the signals from the scanning heads are so stable and reproducible that the diagnostic values for signal
quality defined in the EnDat protocol permit conclusions about the mechanical tolerances of the guide rails. The LINA 200
therefore is not only a part of the drive control, but it also supplies data for the permanent diagnosing and status monitoringof the mechanism. This makes it possible to detect linear deviations during operation.
In this application the purely digital EnDat 2.2. interface offers yet another important and safety-relevant advantage. Strong
electromagnetic interference fields usually arise around linear motors. The EnDat 2.2 interface has a high electromagnetic
compatibility, and thus—as opposed to conventional transmission of analog signals—ensures safe data transmission evenin this type of environment.
Indeed, the EnDat 2.2 interface for absolute encoders is not only available for the application-specific feedback systems forlinear motors described here, but also in encoders for traditional cable-bound elevators. In these applications the encoders
with the EnDat 2.2 interface complement the pure position-value acquisition with additional data, such as the diagnosisof the encoder’s scanning signals for continuous status monitoring or the possibility of measuring the temperature at themotor winding.

Angular measuring technology for positioning the swivel joint
In order to switch from vertical to horizontal travel or vice versa, the active stators and the associated scanning heads
in the shaft as well as the passive magnets and the scale on the elevator cab must rotate by exactly 90° where theshafts intersect. This motion is brought about by a swivel joint in the shaft, driven by a powerful torque motor. The exact
positioning of the swivel joint in the intersection is crucial for a smooth change in direction. Only if the linear components ofthe swivel joint are aligned exactly is a safe change in direction possible that is also free from jerks and oscillations.

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The position measurement necessary for controlling the torque motor during the rotational movement is performed by amodular angle encoder from HEIDENHAIN. Like the LINA 200, it also features the powerful EnDat 2.2 interface. The angle
encoder consists of a scale segment and the associated scanning electronics, and supplies the motor control with all datanecessary for determining the current position of the swivel joint. It also digitally provides comprehensive additional data
about the status of the elevator system at a high resolution.

Conclusion
Once again, measuring technology from HEIDENHAIN is proving itself in a challenging application. The skillful
implementation of the optimum scanning principle in an encoder configuration tailored to the application, together with thefeatures of the digital EnDat 2.2 interface, turns visions into reality.

Change of direction with a cable-less elevator

TECHNOLOGY REPORT7

The new LINA 200 linear encoder for cable-lesselevator technology: above, the U-shaped scale,
which is attached to the cab; and below, thescanning head for mounting in the elevator
shaft.

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*I1249270-20*
1249270-20 · 5 · 4/2018 · H · Printed in Germany