Pressure oscillation in hydrostatic drive trains can cause noise and damage to components. They impair function and reliability. The visualization of the oscillation mode helps to clarify the causal relationships in the hydrostatic drive train and is a basis for the development of remedial measures. Analysis of the pressure oscillation situation, however, can only be carried out in the complete system, since line branching and the impedance of the hydrostats have an influence on the resonance frequencies and the oscillation modes. If only the line length between the components is considered in the pressure oscillation analysis, neither the calculated frequencies nor the position of the pressure antinodes where possible remedial measures are to be placed are correct. This paper presents the metrological determination of the impedance of a hydrostat on a functional test bench (“mobile impedance measurement”) and the preparation of the measurement data for the subsequent simulative pressure oscillation analysis of a hydraulic drive train.

Commissioning of a machine is still representing a very challenging operation and most steps are still executed manually by commissioning engineers. A future goal is to support the commissioning engineers and further automate the entire integration process of a newly installed system with a minimum of manual effort. This use case is known as plug-and-produce (PnP). In this contribution a concept of the Industrial Internet of Things is presented to improve the commissioning task for a pneumatic handling system. The system is based on a service-oriented architecture. Within this context, information models are developed to meet the requirements of PnP to provide relevant information via virtual representations, e.g. the asset administration shell, of the components to the commissioning process. Finally, a draft of the entire PnP process is shown, providing a general understanding of Industrial Internet of Things fluid power systems.

Technological advances (e.g., high speed communication, artificial intelligence) and affordable computing and sensor hardware have become a key driver of developments like “Industry 4.0” or the “Industrial Internet of Things” (IIoT). Large numbers of machines and products are equipped with sensors to constantly monitor their condition, log usage data or trigger control processes. IIoT has been largely adopted by OEMs in various industries (such as automotive, machinery industry, or healthcare and medical), turning their product into cyber-physical systems. However, the resulting potential is not yet accessible to component manufacturers. Overall, horizontal integration of the value chain is still in its infancy. Specifically, IIoT for fluid powers just started in recent years with first research projects and commercial solutions. This work presents a reference architecture for cyber-physical fluid power systems which depicts how horizontal integration can be achieved and which potentials thus can be released. The architecture is validated in an industrial use case. Furthermore, the paper at hand discusses which components of the architecture should be addressed by which actor in the fluid power ecosystem in order to leverage opportunities from the IIoT.

Virtualization of products means the representation of some of their properties by models. In a stronger digitalized world, these models will gain a much broader use than models had in engineering so far. Even for one modelling aspect different models of the same product will be used, depending on the specific need of the model user. That need may change in the course of product life, between first product concepts till over the different phases of development, to product use, maintenance, or even recycling. Since a digitalized world use of these diverse models will not be limited to experts model consistency will play a much stronger role. Model hierarchies will play a stronger role and can serve also as means for teaching product users a deeper understanding of product properties. A consistent model hierarchy leading from a simple to a more advanced property representation can support this learning process. In this paper perturbation methods are analyzed as a means for setting up model hierarchies in a consistent manner. This is studied by models for the behavior of a electrohydraulic drive, which consists of a variable speed motor, a pump, a double stroke cylinder and a counterbalance valve. Model hierarchy is achieved by model reduction in the sense of perturbation theory. The use of these different models for different questions in a system design context and their interrelations are exemplified.

This paper aims to show that controlled hydraulic drives, when properly considered and approached, are a technology that allows for a systematic and safe system design with regard to performance and energy efficiency. Controlled hydraulic drives are predestinated to be an indispensable alternative to electromechanical drives for many fields of application, especially against the background of Industry 4.0. But hydraulic drives will only be able to play this role if they see themselves as a part of mechatronics, speak the language of mechatronics and recognize the increasing importance of electric drives as part of the hydraulic toolbox as a chance.

Recent Power On Demand approaches, realized by using speed and/or displacement variable pump units, led to a significant increase of energy efficiency on hydraulic forming presses. In this paper we follow up on this development by laying the focus on the energy management and storage design of such machinery. With a derived fluidtronical model, we compare five different topologies that supply and manage the power flow for a forming press with die cushion. Our evaluation criteria are: energy consumption, minimization of the infeed power, and qualitative costs. For a representative forming cycle, the losses occurring on each of the drivetrain components and the power electronics accessory are derived in detail. We expect that this research will lead to deeper investigation of more intelligent energy management systems that use multiple storages in an optimal way and further learn and adapt during operation.

Various academic studies show that in the use of common ICE Off-road Vehicles only about 10-15% of the available power at fuel level is actually transformed into useful energy for the actuators. Particularly the Directional Control Valves are responsible for the dissipation of about 35-40% of the hydraulic energy available at the pump level. The machine electrification trend makes it even more urgent to optimize the hydraulic system to ensure greater performance and higher battery autonomy. Traditional Directional Control Valves design solutions neglect important opportunities for reducing losses and improve internal regeneration. Especially, energy recovery is rarely applied and in any case by means of important superstructures which considerably increase the costs of the system. This paper presents an innovative Directional Control Valve layout, based on the Downstream Compensation approach that, in a simple and cost-effective design, allows to recover a considerable amount of energy from both the inertial loads and the simultaneous use of multiple actuators at different pressure level. The proposed layout performance and efficiency are studied through lumped element simulation and laboratory experimental tests.

Oscillating positive displacement pumps are used in many industrial sectors. Mechanical stroke generators / drives such as crank drive, spring-cam drive etc have reached a high technological level, but to which are set mechanical limits. Especially in the smallest dosing range <1 l/h at a pressure range from 100 … 400 bar considerable optimisation is still required with regard to precision and continuity / control range of the dosing flow. In order to expand the current application possibilities for the diaphragm metering pump technology, it is necessary to use new drive systems such as linear motor technology. A linear motor is an electric drive unit which transmits the oscillating delivery movement of the dosing pumps directly to the displacer (hydraulic piston, diaphragm, etc.) without any mechanics, so that highly dynamic movements can be carried out with maximum precision, an individual kinematic profile and a control range of 1:200. The examples of gas odorization and filling processes show how the linear motor drive can be used to technologically solve and even optimize the customer's process requirements. The linear motor pump can realize an integrated 3-parameter control and is therefore suitable for almost any kinematically solvable dosing task.

This paper addresses the necessity of a correct hydraulic accumulator pre-charge pressure for the optimum performance and in some cases even the essential function of the corresponding hydraulic application. In this context HYDAC has developed a smart product for predictive monitoring of the pre-charge pressure without any need to do a measurement on the gas side of the accumulator – the p0-Guard. The paper gives an overview on the conventional way of checking the pre-charge pressure, the function of the monitoring device and points out the benefits of a predictive monitoring of the accumulator precharge pressure. The benefits are clearly depicted by an analytical view as well as on practical example.

Electro-hydrostatic Actuation Systems (EAS) successfully combine the advantages of electro-mechanical actuation - such as high-energy efficiency and low noise emission - with the benefits of electro-hydraulic technology –which include robustness and the precise handling of large forces. This paper defines keywords like EAS and Electro-hydraulic pump unit (EPU), and provides a comparison of the two technologies. Given the wide range of EAS technology topics, it is only possible to briefly introduce and discuss these in this paper. This technology has reached a level that renders it a strong mechanism for machine manufacturers to support existing and future motion control requirements.