The heavy bodies are lowered quietly in front of the workers, perfectly synchronized with the chassis, which glide along on push platforms. The process is a single flowing movement; nowhere do assemblies stop abruptly. The fitters in the joining area, who no longer have to endure the rattling of chain drives, are integrated into this quietly whirring ensemble without fixed time windows: Depending on requirements, the electric monorail systems move sometimes quickly, sometimes slowly, always in unison with the lifting stations and the skillets (push platforms) on the floor. There is no longer a fixed cycle time in this production process. Every transport unit, every hanger knows its position in the system at all times and continuously reports its status parameters to the stationary, higher-level segment controller (control system). Communication is divided into segments that are in constant communication with each other: "The flow movement is parameterized in the segment controller. The travel behavior can be dynamically adapted by the PLC," explains Maxolution project manager Dario Casas Noriega from SEW-Eurodrive. The team from Bruchsal planned, installed and commissioned the Maxolution system solution together with the system manufacturer Logsystems from Schopfheim in South Baden.

The Movivision software from SEW has greatly reduced the real effort on site thanks to the possibility of simulation, emulation and virtual commissioning: "Within just four weeks, 96 vehicles were integrated into the system," summarizes Dominik Adam, project manager at Logsystems, the general contractor in the project at Audi Brussels.

Secure communication, position and movement
The networking of components with each other must function without interference, even in demanding environments such as a modern assembly hall. The WLAN connection is therefore routed via so-called slotted waveguides. The signal - with its high bandwidth - is largely shielded from interference and hardly attenuated even over long distances. A data matrix barcode reader (PXV) for Maxolution solutions is used to clearly and reliably determine the position of the hangers. The Movisafe HM31B intelligent safety controller uses this to reliably generate functions such as SLS (Safe Limited Speed - safe speed monitoring of the lifting axis), SLP (Safe Limited Position - switching off the lifting axis and loader depending on the X position), SDI (Safe Direction - safe direction of movement of the lifting axis) and also the innovation for safe distance monitoring in the assembly line "Safe Distance Monitoring (SDM)".

The double-track electric monorail system with redundant lifting drives at the front end, shown here after cornering. © SEW

SDM, winner of the handling award 2016, makes the production line flexible. Rigid mechanical spacers between the hangers are no longer required and SDM allows the exact distance required to protect employees to be varied - both in a straight line and in the curved area, which creates an additional workstation. This function is realized in the electric monorail systems by the Maxolution system consisting of controller and safety controller: each unit has a controller from the Movipro series from SEW and a Movisafe HM31B safety controller for the safety functions.

Drive technology with wide speed ranges
Depending on the range and current requirements, the EMS units operate autonomously at speeds of between one and 70 meters per minute. This wide speed setting range (maximum 1:2,000) is made possible by the energy-efficient, decentralized DRC synchronous servo motor (IE4 drive). In the assembly sections where workers are at work, the safe speed of maximum 15 meters per minute is maintained. At Audi in Brussels, the requirements were very high: "We are implementing a curve drive here that has never been seen before in the industry," reports Dominik Adam. The reason for this is the sophisticated, special design of the heavy-duty EMS as a two-rail system.

In the application, the sophisticated drive technology is realized by the electronic differential with two DRC motors (double-track EMS and widely spaced drive motors). This enables smooth and wear-free cornering. "We have," says Tom Timmermann, Project and Technical Manager at Audi Brussels, "much greater flexibility for the employees on the assembly line. The work is more ergonomic and the conveyor is much quieter overall than with the old chain conveyor technology. Due to the low height, we could not install a single-track EMS, but had to build a lower double-track track, a non-standard solution. Correctly coordinating and monitoring the different speeds of the inner and outer curve radius is a technical challenge. It was mastered thanks to the close cooperation of the project partners right from the start."

Pioneer on the road and in production
The Belgian plant is a pioneer in the Audi Group - in line with the e-tron product. "We don't want to be fast followers, but trendsetters. When we get involved in a project, it's all or nothing," emphasizes Secretary General Andreas Cremer from Audi Brussels. "We go one step further with our demands on modern production technologies and are dependent on partners who support and advise us in such processes."

With SEW, Audi has proven experts for the automotive sector on board: the specialist for drive technology can count numerous giants of the automotive industry among its customers. Since 2012, the specialists from Bruchsal have equipped over 2,000 EMS units and skillets with drive solutions for Audi worldwide (Ingolstadt, Neckarsulm, Hungary, Mexico). The installed base is always kept up to date with the latest functions, for example through software updates for condition monitoring. SEW-Eurodrive with its Maxolution system solutions will continue to be a strong partner for Audi in the future.

U.Marmann/as