This paper discusses an investigation on a novel hydraulic pump concept. The idea aims on a pump principle to be directly connected to highspeed electric motors to build compact highpressure drives [... aus der Einführung]

Pressure reducing valves perform various control tasks in mobile machines. In many cases contamination sensitive environments require pilot-operated valves, because of its more robust performance. On the other hand, dynamic valve behavior can be critically in certain applications. Overcoming the restrictions resulting from stand-alone test rig attempts, suitable simulation principles are nowadays the state of art in valve design. Unsuitable model approaches and missing consideration of the application may result in wrong design decisions. This paper discusses two important modeling issues, in particular the solenoid and spool leakage behavior, in combination with the connected system under control, a pressure-actuated clutch. It is shown, that even for standard proportional valves a critical view on customers´excitation strategy and site of installation decides on success or failure of an already used design variant.

All-wheel suspensions are generally challenging, particularly if they are equipped with an automatic level control. In mobile machines, the special application conditions make their use even more demanding regarding layout and control. A high center of gravity, load variations, off-road-conditions etc. require special measures to reduce roll and pitch movements. Additionally the uneven ground along with the mechanical suspension setup often create a need to measure and optimize tyre-to-ground forces in order to provide best traction and suspension properties. Hydropneumatic suspensions have all the potential to meet all these requirements and provide a comfortable, safe and efficient suspension setup.

This paper will give an overview about the technological change in Industrial Hydraulics and the impact of the Digital Twin on the related new engineering processes and methods in order to overcome the challenges coming out of that technology change. Simulation models will more and more become a decisive factor for the engineering process. The Digital Twin will be a window of opportunity for innovations and a technology push for the engineering process and the products in the Industrial Hydraulics.

Hydraulic displacement systems are a technology that has been known for many years. Nevertheless, the impression is created that the large fields of application are not only being developed very tentatively, but in many cases are being completely denied. What might be the reason for this? Are the electromechanical solutions better? What is the missing element to build the bridge from the available hydraulic-mechatronic technology to broad customer application? This paper provides an overview of how the targeted use of the latest technologies in the product and in the entire value-added chain has resulted in a complete mechatronic hydraulic system that pushes the limits of feasibility in terms of power, accuracy and efficiency and delivers a clearly calculable benefit for both the plant manufacturer and the end customer. In addition to the great accuracy and high reliability, there are also considerable savings in the total cost of ownership (TCO) due to a previously unattained level of efficiency. The thoughts of health and environmental protection are just as much a part of the considerations as product safety and personal protection. Finally, an outlook on possible expansions is given, and which areas of application are possible for the technologies developed within the project. The aim is not to show how the traditional fields of application of hydraulics are to be defended, but rather to use the strengths of a hydraulic-mechatronic approach in a conscious and clearly structured way to make new applications possible.

Independent metering valve systems open up for more flexibility because of the ability to control meter in and meter out flow individually, thus enabling many possibilities to adapt the actuator s behaviour to the user´s needs without altering any hardware. Furthermore, with alternative flow modes significant energy savings are possible. In many applications like excavators smooth switching between flow modes is required, a demand the market does not provide a satisfying solution for yet. Here, an approach using a short circuit path for smooth switching has been developed. The control algorithm hands over the volume flow from one path to another continuously depending on the current actuator load. Due to the flexible software structure the developed control algorithm can be applied to a very broad variety of independent metering valve layouts. Simulation results are promising and currently the solution is undergoing test rig evaluation.

The paper presents a study of a highly integrated hydraulic powertrain for mobile working machines. The highlight of this new concept is the replacement of separated drive and working pumps in conventional systems with only one displacement pump. After a comparison of different system architectures, the appropriate operating and control strategies for the chosen topology were applied and optimized. With the help of simulations in AMESim, a proof of the function of the hydraulic circuit and the controlling has been established. In addition, the energy saving potential of the integrated hydraulic system is also considered, by comparing the energy consumption of the new and the conventional powertrain in different duty cycles.

Modern electronic technologies allow for the design and production of Micro Electro-Mechanical Systems, also called MEMS. These microchips are widely used as sensors in many fields of application, also in embedded systems in heavy-duty and agricultural vehicles and in automotive applications. In addition to the classic uses of these sensors, new architectures and sensor topologies exploit electromechanical principles of great interest for the field of hydraulic applications. This paper presents some examples of the application of a new MEMS architecture based on self-oscillating microresonators, which offer interesting capabilities in the measurement of mechanical deformation of mechanical components. MEMS are applied as non-invasive pressure and oil flow sensors, and represent an interesting option for creating smart components. All the applications described are intended to show the sensor potential and have a qualitative and exemplary character, but they can provide a basis for in-depth studies on the potential and applicability of these sensors.

Proportional valves are widely used in fluid systems for controlling the volume flow rate or fluid pressure. The actuation of this valves is done by PWM-driven proportional solenoids, which enable self-sensing position determination abilities due to air gap-dependent electrical behaviour, e. g. for condition monitoring or position controlling tasks. However, the sensor properties of conventional proportional solenoids are poor due to ambiguities caused by hysteresis effects (magnetic hysteresis, eddy currents) and saturation effects. Thus, a sensor-designed actuator was developed with very low hysteresis effects and unique position determination by using electrical sheet and a particular air gap design. This paper deals with investigations of a novel self-sensing position determination approach on a demonstrator of the sensor-designed solenoid. The advantage of this method is an online consideration of transient effects such as mean current change and armature motion as well as temperature-dependent resistance. For this, a combined evaluation of the differential inductance and flux linkage during PWM periods is proposed.

As is generally known, pressure-resistant solenoids for valves are used in hydraulics and pneumatics. These solenoids, for example, consist of a so-called pole tube with an integrated armature and a separate solenoid coil. Suitable displacement measuring systems are used in order to measure the armature´s as well as valve spool´s position constnatly; these ar directly mounted to the solenoid. Exeamples here are Hall Effect sensors or LVDT transducers. In case of lesser requirements, it is also possible to measure the valve spool´s position directly and in simplified manner. Here, partially standard proximity sensors are employed, which use the valve spool directly as measuring object. In these cases, however, only discrete position measurement is possible. A constant displacement measurement is not necessary. By means of the sensorless position-control developed by MSM, the armature´s position can be executed directly by analyzing the solenoid coil, partly replacing the usual sensors, under adapted basic conditions.