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Product category: Drives, motors and power transmission, couplings, clutches
News Release from: Control Techniques | Subject: 'Unidrive SP' AC drives at D-C Ludwigsfelde
Edited by the Manufacturingtalk Editorial Team on 01 February 2008

AC drives simplify production line
maintenance

To simplify maintenance, an automotive production plant has restricted itself to one make and one type of frequency converter for all applications over 1.1kW, to eliminate long down-times.

Control Techniques Drive Centre in Chemnitz, Germany, has supplied over 800 AC drives, for all applications over 1.1kW in the new DaimlerChrysler 'Sprinter' car production facility in its Ludwigsfelde plant, near Berlin Built specifically for a new model of the Mercedes 'Sprinter', the plant chose Control Technique's 'Unidrive SP' AC drives

Technical manager at Ludwigsfelde, Mr Wagner, said that the main reasons for choosing Unidrive SP were programming flexibility and openness.

Wagner said: "We had already gained a lot of experience with Control Techniques Unidrive and Commander SE drives on the 'Vaneo' project and we particularly liked the Unidrive SP's versatility".

DaimlerChrysler used around 600 Control Techniques drives in its 'Vaneo' production facility in Ludwigsfelde.

Production was optimised by direct communication between PLCs and the drives.

Wagner said: "We like the flexibility and openness of the Unidrive SP range.

It enabled us to use a standard equipment range for all relevant applications and allowed us to use our own process expertise in the form of a standard user programme".

He explained: "To simplify maintenance, we have restricted ourselves to one make and one type of frequency converter for all applications over 1.1kW, and the system was designed to eliminate long downtimes".

Wagner added: "Our experience has shown that the Unidrive SP is very reliable and also very flexible in its configuration.

But if we do ever have to swap a drive, it's a very quick job.

We have reserve systems for critical parts of the plant, so that the production line keeps running, but we know that, in an emergency, we can swap and reprogram a drive in around 10 minutes".

* Open and closed loop usage - after the decision was made to produce a new Sprinter model in the Ludwigsfelde plant, Unidrive SP was specified as the standard for all applications over 1.1 kW.

These included open loop and closed loop applications, for synchronous motors and induction motors, and all position-controlled axes in the entire facility.

Applications ranged from control of conveyor belts, scissor lifts, automated guided transport vehicles and advanced compact storage systems, up to ventilation and extraction systems.

Locations included body shop, paint shop and final assembly.

* Body shop (BIW) - in the body shop, the Sprinter bodies are built from preformed sheet metal, using welding robots and a fully-automatic material transport system.

Over 200 Unidrive SP drives are used in this area.

They are operated in open loop mode for transport tasks (in the buffer store, for example, where up to 86 bodyshells are stored temporarily on eleven rails) and in closed loop mode for hoist units.

A typical precision application can be seen in the automatic welding cells where two Unidrive SPs, coupled with the UMD Unimotors are used in a master/slave configuration for the lifting mechanism, synchronised with a third Unidrive SP with Unimotors in position control.

Most of the Unidrive SP drives in the Ludwigsfelde plant are fitted with an application module for additional onboard processing and Interbus communication.

Profibus DP or CANOpen bus protocol is used on some axes, this depends on the particular controller type used.

Others have an additional encoder module to enable a second transmitter signal, from a laser measuring instrument, for example, to be processed.

* Paint shop - around 200 more drives - rated at up to 110kW - are used in the Durr paint shop for ventilation and extraction tasks.

Added to this, a number of blowers and pumps for hydraulic axes have to be controlled.

Most of these drives run in open loop mode, with Interbus communication links to the corresponding PLCs.

Synchronous motors with resolver feedback to the controlling Unidrive SP drives are used in the 15-workstation cathodic electro dip coating plant, not only for forward movement, but also to rotate the body shells within the dip.

In this section, Profibus communication is used for all drives, including the open-loop elevator drives.

* Final assembly - the most demanding drive applications are found in the final assembly, where approximately 400 Unidrive SPs are used, in open-loop and closed-loop mode.

Each of the open-loop transport units in the overhead conveyor system is supplied with DC power for its onboard drive / motor system via a specially designed busbar system that also enables CANbus communication.

The Unidrive SP drives were installed using through-panel mounting technology, to keep the control cabinets very shallow.

* AGVs - automated guided transport vehicles, used for carrying components such as the complete power transmission system of a Sprinter - engine, gearbox, drive shaft and axles - are supplied by induction from conductors laid in the floor.

In addition, six Unidrive SP inverters (1.1 to 1.5kW) are supplied at 500V DC.

Two induction motors are used for movement and steering, whereas two Unimotor type 142 UMD synchronous servo motors are required for the scissor lift, and two Unimotor type 115 UMD motors for trim.

Control signals are picked up from feed points let into the floor, so the vehicle is instructed when it should move and which movement profile it should follow.

A CANbus/Interbus gateway is located in the interior of the vehicle and communication with all six inverters takes place via Interbus.

* Storage systems - two high density storage systems employ Unidrive SP AC drives for the automated storage / retrieval systems.

A bodyshell storage facility with 198 positions over two tracks and four-high racks is used as a call-off point between the painting and assembly operations, and demands precision movements in three axes.

The axes comprise lifting (55kW), travelling motion (37kW) and lateral motion (2.2kW) and are all controlled in closed loop mode with encoder feedback.

Additional feedback signals are provided for longitudinal and lifting axes.

A long-range laser for the distance along the rail and an absolute encoder fitted on a wheel of the lifting axis enable monitoring and error correction, where necessary.

Any significant deviation between these signals and the position feedback at the motor results in a fault trip.

In the small components storage system, around 10,000 different components are accommodated in four magazines.

Two vehicles are used there, each fitted with four Unidrive SP giving 3-axis servo control (18.5kW for lifting, 11kW for longitudinal and lateral motion) as well as a small, integral 1.5kW conveyor for the picking process.

Here too, all inverters have an application module for processing and Interbus communication.

The Unidrive SP variable speed drive range spans 0.75kW right up to 1.9MW.

Unidrive SP is the world's most advanced 'solutions platform' AC drive, configurable into five operating modes - open and closed loop, vector, servo and regenerating modes - connectivity to most industry standard networks and accepting 14 position feedback protocols.

With a range of plug-in module options, its on-board PLC can be supplemented with high-end PLC processors, customer programmable application modules are also offered with a library of software solutions. Request a free brochure from Control Techniques ...

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