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MDA Technologies 1/2015

MDA Technologies 1/2015

Universal machine with

Universal machine with energy efficient drive Ralf Schrempp When we consider drive and safety concepts in the design of a machine to be of equal importance, we can naturally talk about a careful look into the design. The result is a modern universal machine with certain advantages. Link to Vredo Video You can use this link to learn more about Vredo in this field Author: Dipl.-Ing. Ralf Schrempp, CEO, Sauer Bibus GmbH, Neu-Ulm, Germany The hydrostatic drive requirements for a vehicle with high service weight are very demanding. Here the continuous and energy efficient drive, considering different requirements in Off-Road and On-Road mode, is complex. Defined driving strategies and associated electrical-hydrostatic control plays a significant role. The combination with the hydrostatic large-angle technology is of special importance in practical implementation. Even theoretical calculations support the experience in test vehicle, which has reduced fuel consumption and increase of power and driving comfort and represents the basis for a modern drive. Requirement for the vehicle The Vredo machines excel through specialized sequences in the communal technology such as cutting, scarifying and gathering. Another interest area of application of these universal machines is in the manure technology. With double-cutting disc system, an optimal result can be achieved irrespective of weather conditions. The requirements for the drive can be compared with that of a tractor. However, these communal machines are specialized in their area of use, drive faster and cope up with lesser traction compared to machine weight. Current standard is continuous and optimized for consumption and performance and requires a complex transmission and engine management. Power distributed transmissions with large-angle hydrostats of 45° and implementation of different driving conditions in forward and reverse direction are proven. Simple operation and uncomplicated reversing operation are indispensable here. Even the electrical control of hydrostats, activation of parking brakes, hydraulic coupling functions and emergency functions must correspond to the applicable safety standards. VVT600 from Vredo is a hydraulicmechanical transmission with a continuous variable output speed for front and rear axis. The transmission consists of two main parts; a mechanical and a hydraulic part, which work completely isolated from each other, whereby the hydraulic pump and two engines are mounted on the transmission box with 45° swivel angle. In addition, the transmission has a mechanically switching joint shaft, suitable for complete engine power and a lockable longitudinal differential. Three mechanical connections for large hydraulic drive pumps are provided in the transmission housing, the permissible input torque for this is 2,650 Nm, the maximum input power 42 MDA Technologies 1/2015

DRIVE TECHNOLOGIES is 405 kW (550 HP) and maximum output torque is 13,500 Nm. The speed range in the new Vredo Trac Generation is from 0 to 50 km/h at maximum 1,300 min -1 , with a maximum tractive force of 280 kN. The transmission has two groups and differentiation is made between road and crosscountry speed, which are switchable under full load. Power distribution with 405 kW input power Different driving strategies can be detected here n Lower gear with a speed from 0 to 20 km/h, with maximum tractive force of 280 kN n Higher gear with a speed from 0 to 50 km/h, with a maximum tractive force of 115 kN n A combination of both, at a speed from 0 to 50 km/h Modern electronics controls the hydrostatics The installed large-angle engine “Module Drive” from Sauer Bibus is controlled through a so-called low pressure adjustment with an adjustment pressure from 25 to 30 bars. The combination of angle sensor and proportional valve enables a precise control of the swivel angle. Vredo’s latest development is equipped with three large-angle units with 233 cm 3 . The drive can quickly adjust to any requirement through latest sensor technology and networking of components through modern electronics. The known and robust hydrostatics in combination with a planetary gear is responsible for power transmission. Comfort and energy savings in proven technology, by adhering to emission laws, is the basis of this development. Integrated safety functions The drive must independently detect potential risks and hazards. In this case, international standards such as IEC 61508 influence the methodical procedure of programming. In addition, the entire system must be analyzed to avoid problematic driving conditions. Fraunhofer Institute has already developed a method called SICMA (Software Integrated Component Failure Modes and Fault Tree Analysis) for this purpose, which is used in this drive. The electronics also monitors all the outputs permanently. The angle sensor of the hydraulic engine sends a ratiometric signal from 0.5 to 4.5 V. The connection is broken if the voltage falls below 0.5 V. In addition, all the sensors are individually monitored and checked for plausibility. In addition, vehicle parts such as driver seat are included in the safety consideration and programming. For example, the vehicle can be moved only with a driver. If the vehicle is moved without a drive, the braking function will start. The constant adjustment between the swivel angle and the appropriate driving performance is another example. If a significant deviation over a longer period of time is measures, the system changes to emergency mode. The so-called “limphome-mode” helps the driver to move the vehicle from dangerous situations with a reduced pressure. Different analytical methods were used for the verification of safety: n FMEA (Failure Modes and Effects Analyses) – the structure analysis n FSR (Failure System and Reaction Analyses) – the evidence of mistakes n FMDEA (Failure Modes, Effects and Diagnostic Analyses) – the evaluation of possible mistakes under consideration of characteristic values Equipping the VREDO machine type VT5518 with all the safety requirements is a cost-intensive challenge. Each vehicle must be checked intensely for its individual functions. Project progression After the presentation in Agritechnica 2013 in Hannover, the tests and preliminary experiments appear to be very promising. The results in the practical machine test with select customers show that we are using the correct drive concept here. The integrated safety concept stands the test. Photographs: Teaser Vredo; other images Sauer Bibus Company name: Sauer Bibus GmbH Headquarters: Neu-Ulm, Germany Established: 1984 Employees: more than 700 Products: drives, pumps, valves and hydraulics THIS ARTICLE IS A CONTRIBUTION BY About MDA Technologies 1/2015 43


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