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A special clamping cell developed in the framework of the collaborative research center 368 at the Technical University of Aachen (RWTH) is able to clamp different workpieces in an absolutely autonomous way. In this paper an autonomous hydraulic clamping system for milling processes as well as a clamping system for 3-dimensional laser welding are presented. In particular a proportional throttle valve for several hydraulic cylinder developed for this clamping cell is introduced. The clamping system for the milling process is a completely autonomous hydraulic clamping system. All of the hydraulic as well as the electric components are integrated into this device. Further more a micro controller and a power supply are integrated into the clamping system as well. For the welding process the clamping system has to hold two sheet metal.

A new hydraulic brake utilizing a self-energizing effect is developed at the Institute for Fluid Power Drives and Controls (IFAS). In addition to a conventional hydraulic braking actuator, it features a supporting cylinder conducting the braking forces into the vehicle undercarriage. The braking force pressurizes the fluid in the supporting cylinder and is the power source for pressure control of the actuator. The new brake needs no external hydraulic power supply. The only input is an electrical braking force reference signal from a superior control unit. One major advantage of the SEHB concept is the direct control of the actual braking torque despite friction coefficient changes. The prototype design, presented in this paper, is done in two phases. The first prototype is based on an automotive brake caliper. It is set up to gain practical experience about the hydraulic self-energisation and to prepare the laboratory automation environment.

The floating cup principle is a new axial piston concept for hydrostatic machines. It features a high number of pistons, arranged in a double ring, back-to-back configuration. Furthermore the pistons are locked onto a central rotor and each piston has its own cuplike cylinder. These ‘cups’ are floating on and supported by a barrel plate. The pistons have a ball shaped crown, which is sealing directly on the cylinder without a piston ring. A first prototype of the new pump has been built and tested. For comparison a state-of-the-art slipper type pump and a bent axis pump (both constant displacement, 28 cc/rev) have been tested as well. The steady-state performance tests have proven the high efficiency of the floating cup principle. The low speed tests, during which the pumps are tested as a motor, have confirmed the low friction losses and high starting torque of the floating cup principle. Furthermore the high number of pistons strongly reduces the torque variations.

The simple, compact design and the high power and force density of linear-motion hydraulic actuators make them suitable for a wide range of applications in the machine building and systems engineering sectors. Linear hydraulic actuators do, however, demonstrate more elasticity with respect to the desired position than their electric counterparts by dynamically changing loads. The time response for maintenance of the desired position when subjected to dynamic load changes is referred to below as dynamic load stiffness. This article begins by considering the elementary principles of a cylinder's stiffness. Afterwards it then goes on to describe various approaches in an attempt to increase dynamic load stiffness and to present the simulation results for the different systems. Then it concludes by discussing these results and using them as the basis for an assessment of the potential of each approach.

In this paper compatibility studies of biofuel candidates and similar liquids with the elastomeric materials nitrile butadiene rubber and fluoroelastomer are presented. The results gained with defined reference elastomers are compared to results gained with the materials used in the technical application. For this purpose test specimens are prepared from fuel hoses and the material used for shaft seals of fuel pumps. The experimental results are subsequently used to evaluate prediction approaches based on the HSP- and QSPR-method. Finally a comparison of these two approaches is given.