This article presents digital fluid power as a new branch of which offers high potential for innovative solutions. The variety concepts is quite large and have long been successfully applied in low-power applications. Research development now becoming more intensive, being undertaken by several research groups also industry. First applications will be brought to industry soon. A successful application requires components, sound understanding system control principles.

Switching and digital hydraulics require adequate switching valves for their practical application. A major criterion is the time which should in most cases be less than 5 ms. The demands on valve nominal flow rate are rather wide range from 1 l/min (@ bar) up to hundreds of litres. In this paper a new seat concept presented. It piloted employs multi poppet concept. Its about 100 its ms pressure drop bar. With energy efficient drives can realized, instance 10 kW 20 range. type design makes...

Digital hydraulics uses simple and cheap on/off valves in order to replace expensive proportional valves. Furthermore, with fast switching hydraulic converters the energy efficiency can be raised compared valve control. The buck converter (HBC) represents an efficient cost-effective switched inertance system, because its inductance is realized by a pipe. In this paper, prototype for linear cylinder drive controlled HBC presented. Characteristic axis that directly mounted on cylinder, which...

This paper is concerned with the application of switching technology to hydraulic actuation. Over last 50 years advances in power electronics, faster and static switches have been developed applied control motors. Hydraulic evolved opposite direction: was not considered, more accurate proportional flow/pressure devices (servovalves etc) were developed. However despite sophistication such valves, from an energetic viewpoint dissipative inefficient. Indeed, by analogy it can be seen as...

Various control strategies in digital hydraulics have been proposed and studied so far. In hydraulic switching Pulse Width Modulation (PWM) of one or two valves was mostly considered. This paper deals with Frequency Control (PFC) which — opposite to PWM uses the pulse repeating frequency not width as input. PFC may be preferred if device can realize a very particular quite favorable way. studies influences flow rate shapes on overall system dynamics. Based dimensionless mathematical model...

This article addresses mainly questions about the roles of fluid systems, in particular digital ones, an “Industrie 4.0 (I4.0)” environment. There are three roles: general machines’ subsystems/components’ role machines I4.0 production system, subsystems/components which produced under conditions, and manufacturing systems’ components setting. These discussed examples hydraulic solutions fulfill these excellently presented. They feature simplicity robustness hardware transfer functionality to...

Hydraulic switching control with fast valves may excite unacceptable hydraulic and mechanical oscillations. Particularly if transmission lines are used, which have many oscillation modes, the avoidance of resonances by a proper timing pulses is hardly feasible. Then, passive filters be good solution. A simple RC filter applied to cylinder drive line investigated transfer function analysis, numerical methods, experiments. Properties dynamic behaviour elucidated approximate relations derived...

This paper is concerned with the application of fluid power in autonomous robotics where high density and energy efficiency are key requirements. A hydraulic drive for a bioinspired quadruped robot leg studied. The performance classical valve-controlled (“resistive-type”) an saving (“switching-control mode”) actuation system compared. After describing bio-inspired design prototyping, models both drives developed assessments carried out. It shown through simulation that switching-control mode...

Fluid stiction is a force which created by the average pressure difference between fluid-filled, narrow, quickly opening gap and surrounding pressure. It plays negative role in compressor valve technology fast switching valves, since it hinders an immediate response of valves to changing driving situation. In this paper, axisymmetric fluid problem studied analytical mathematical models experiments performed on specific test rig. The study shows that narrow gaps dominated viscous flow as...

Modelling of a hydraulic system featuring specific type switching control is presented. Despite conventional drive technology where rather smooth changes pressure and flow rate are intended oscillations constitute undesired phenomena, provokes as an indispensable element to achieve high energetic efficiency with valve control. The under study one which comprises novel valve, long line considerable wave propagation dynamics, cylinder, the valve's dynamics.

This paper deals with the efficient computation of hydraulic switching systems a check valve by mixed time–frequency domain method; frequency-domain modelling is performed on wave propagation in pipe and time-domain applied to valve. The dual property makes complete problem have variational inequality properties. A solution method presented which replaces pressure flowrate as function one new variable. resulting system non-linear algebraic equations solved using Newton–Raphson combination...

In digital hydraulic systems, switching valves have opening and closing times in the range of a few milliseconds. Due to this fast switching, high bandwidth pressure pulsation is excited, which stimulus for airborne noise up some kilohertz. Since human ear very sensitive audible frequency range, an analysis influence valve’s curve on surge pipe system intended. The study based simulations employing dynamic models linear wave propagation laminar fluid flow. particular, simple with valve at...

This paper deals with the investigation of two actuation concepts for hydraulic switching valves which utilizes a piezo stack and bistable mechanism. The goal this work is to show small compact light-weight can be designed pave way their integration in exoskeleton applications. shows modeling design aspects valve prototype discusses measurements were taken throughout process as well final valve's behavior. Finally, possible improvements robustness, miniaturization increased dynamics are suggested.

This paper presents the application of a hydraulic DC-DC converter, namely step down Buck Converter to actuation robot leg that is part quadruped HyQ. The use Hydraulic (HBC) offers significant advantages in terms improved efficiency systems analogously an electric switching converter as opposed rheostatic-type system. In this paper, HBC consisting two digital valves and check introduced improve performance singl (HyQ). type buck able support locomotion directions. operates at frequency 100...

Check valve dynamics plays an important role in many fluid systems, such as compressors, hydraulic pumps, and switching converters. Plate type check valves are a frequently employed dynamically challenging cases. Despite the relevancy of plate dynamics, only few exhaustive works can be found literature, focusing on behavior for high-frequency applications. This paper presents in-depth characterization designed rectifier oscillation pump working at 300 Hz. The aim is to identify sufficiently...

Digital hydraulic drives are known for their superior efficiency, power density, and robustness. Such advantages make them an attractive alternative (to electric drives) actuation of exoskeleton devices. This work presents development a prototype such digital hydraulically driven knee its experimental testing. The device uses two miniature cylinders novel mechanism to translate the linear motion rotary motion. is controlled via passive control method in stance phase simplified model...

Stiction forces exerted by a fluid in thin, quickly widening gap to its boundaries can become strongly limiting factor of the performance technical devices, like compressor valves or hydraulic on–off valves. In design optimization, such need be properly and efficiently modeled. Cavitation during parts stiction process plays strong role needs taken into account achieve meaningful model. The paper presents an approximate calculation method which uses qualitative solution properties non...

Magneto-rheological (MR) fluids are suspensions of micron-sized ferromagnetic particles in a non-magnetic carrier fluid. The essential characteristic MR fluid is the rapid and reversible transition from state Newtonian-like to behaviour stiff semi-solid by applying magnetic field ∼0.1–0.4 T. This feature can be understood fact that form chain-like structures aligned direction. offers three modes operation, namely direct shear mode, valve squeeze mode. latter particular interest due its...