The all-rounder: SCHLEICHER industrial controller in the Liebherr MK 80 mobile construction crane

How do you combine flexibility and quick availability of a mobile construction crane with the functional advantages of a high-performance tower crane ? Liebherr provides an answer with the MK80 mobile construction crane: Design a folding crane with a maximum jib length of 42 m and a maximum hook height of 48 m, assemble the entire construction on a special vehicle with axes with individual steering and add a controller which unpacks and erects the crane almost fully automatically within a few minutes at the site of operation. Assembly and disassembly, all safety functions and crane functions are controlled and monitored by SCHLEICHER's compact controller Promodul-F during operation.

Fig.: 1

Liebherr MK 80 mobile construction crane

Liebherr: Cranes and more

The company founded by Hans Liebherr in 1949 has today become a decentralized group of companies represented on each of the world's continents with more than 20,000 employees. For civil engineering applications above and below ground, Liebherr offers construction machines such as hydraulic excavators, mining trucks, duty cycle crawler cranes, wheel loaders, crawler tractors and loaders, pipelayers, cement mixing plants and truck mixers. The extensive range of cranes includes tower slewing cranes as well as mobile, ship, container and handling cranes. In addition, the group operates in mechanical and construction engineering as well as in aerospace and transportation systems. It also designs refrigerators and freezers for domestic use as well as planning and implementing complete industrial installations.   Push-button assembly.

The MK 80 is transported fully equipped with the tower, boom, counterweight, power unit and height adjustable crane driving cab. Despite this, the crane is only 15.9 m long, 2.75 m wide and 4.0 m high when in transport position. All axes on the vehicle are steerable, allowing the mobile crane to access almost any location. On arrival at the site of operation, it takes the crane driver around 13 minutes to set up the crane. The required "crane configuration" (assembly direction, height of hook and boom position) is preselected, after which the program-controlled crane unfolds itself using an assembly winch for the tower and a second winch for the boom. The controller monitors every single step of the process; hoist rope and trolley travel rope remain tensioned during assembly and disassembly. The crane chassis is supported by four hydraulically extendable sliding beams with hydraulic jacks and supporting pads, and the crane is leveled automatically.

Fig.: 2

Crane unfolding in a few minutes

PLC in the crane

Using an industrial controller in a crane is nothing unusual for Hartmut Ketteler, Chief Designer of Control and Drivetrain Technology at the Liebherr factory in Biberach: "The Promodul-F easily satisfies the performance requirements of a crane controller, including all the safety functions. We were therefore able to make use of an inexpensive, tried and tested standard controller with a compatible programming environment." However, the controller must also be capable of withstanding the specific stresses and strains experienced during transport and operation. Special structural elements and a completely sealed circuit board extend the temperature range down to -10 °C and allow it to be used when covered in condensation. Vibrations do not cause any problems either, for example, during transport along uneven roads because the Promodul-F has a much flatter and more robust design than comparable controllers.

Promodul-F

Schleicher's Promodul-F is a universal, modular compact controller for bit and analog value processing as well as positioning control. Two control units make up the core of the system: one PLC module and one CNC module with integrated PLC and trajectory controls for up to 6 axes. These control units can be combined with up to six function modules (bit and analog I/O modules, positioning interfaces etc.), whereby the control bus is simply looped through without requiring any additional hardware. A total of 192 I/O channels are possible. The bus is connected via Profibus-FMS or CANopen. A modem connected to the control units allows remote diagnosis and maintenance and a large selection of compatible indicators and operator panels for mobile and stationary use is also available.

The real time multitasking operating system stored in the Flash-ROM can be interrupted. Jump instructions and loop constructions familiar from high-level languages are available for programming. More extensive programs can be structured more clearly by dividing them up into subprograms with transfer parameters. Prodoc U5 is a type of programming software for writing programs and for testing purposes that can be used to show and change the status of selected variables and display the flow of the program. A Macro AWL and a FUPKOP editor (logic and ladder diagram) are integrated.

Fig.: 3

Compact control for PLC and CNC applications: Promodul-F

Conclusion

On the MK 80 mobile construction crane, the Promodul-F actually manages the crane while in operation, handles monitoring and safety tasks and overseesautomatic assembly and disassembly. The high performance , robust system provides a welcome alternative to costly proprietary solutions.