Hydraulic Fluid Power Research Articles

Sensor Technologies for Hydraulic Valve and System Performance Monitoring: Challenges and Perspectives

AbstractHydraulic fluid power systems are essential for a range of engineering applications such as transportation, heavy industry, and robotics. The scale of the industry is such that hydraulic pumps are estimated to account for 15% of all the energy consumption in the European Union and yet the average efficiency of fluid power systems is only 22%. The digitalization of hydraulic systems offers significant advantages in terms of energy efficiency, performance, reduced maintenance, and automation. However, this requires advances in the integration of smart sensing technologies to provide real‐time feedback on the operation and health of hydraulic components. This review details developing trends in hydraulic fluid power research and provides an overview of progress related to the digitalization of these systems and their integration within an Industry 4.0 framework. The fundamentals of relevant sensor technologies and innovative approaches for integrating sensors into hydraulics systems are discussed. Methods to deliver power to the sensors and associated electronics through harvested pressure ripples are also reviewed. An outlook with respect to future directions in this field is given, including an assessment of the potential for exploiting advanced manufacturing technologies, in particular additive manufacturing, to facilitate successful sensor integration into hydraulic fluid power systems.

ANALYSIS OF THE POSSIBILITY OF APPLICATION OF HYDRAULIC MOTOR-WHEELS IN TRANSMISSIONS HIGH-SPEED TRACTORS

Goal. The purpose of the article is to assess the possibility of developing a hydraulic fluid power in accordance with the standard traction-speed characteristics of the KhTZ-17021 wheeled tractor with the of using gearless drives of the driving wheels. For this purpose, the calculation of the hydraulic fluid power of the wheeled tractor was performed when using the latest radial piston multi-cycle hydraulic motor-wheels with a wide range of rotation frequency and adjustment of the working volume. Research methodology. An analysis of the traction-speed characteristics of the KhTZ- 17021 wheeled tractor and, based on it, a review of modern high-torque radial-piston multi-cycle hydraulic motors from the point of view of meeting the characteristics of torque and rotation frequency with power limitations relative to the serial model in the full speed range of the tractor. The maximum values of the working volumes of the 4 driving hydraulic motor-wheels and the power supply pump of these hydraulic motors, the torque and pressure drop in the hydraulic drive are calculated, and the modes in which it is necessary to change the working volume of the hydraulic motors from the maximum to the minimum values to work out the traction-speed characteristics. A comparative analysis of radial-piston multi-cycle hydraulic motors was carried out, and for the hydromotor-wheel model MHP27 of the "Poclain Hydraulics" company, which was chosen for the study, the hydraulic principle diagrams were considered with the use of a hydraulic regulation system of four stages of the working volume in hydraulic motors, the use of combined parking and service brakes, as well as an anti-skid system using means of proportional electro-hydraulic automation. The results. High-torque hydraulic motor-wheels of the radial piston type were selected, which make it possible to ensure the operation of the tractor transmission without intermediate gearboxes between the hydraulic motors and wheel hubs, and the calculated value of the working volume of the axial piston pump, which ensures the operation of the tractor transmission in the full speed range. Based on the results of the calculations, it was established that the pressure in the hydraulic drive does not exceed 35 MPa, while values from 40 MPa to 50 MPa are achieved in modern pumps and hydraulic motors. The possibility of increasing the speed of the tractor from standard 35 km/h to promising 50 km/h is shown.

ANALYSIS OF DYNAMICS OF VOLUME HYDRAULIC POWER STEERING SELF-PROPELLED TRACTOR CHASSIS

Goal. Analysis of the dynamics of the hydraulic fluid power steering drive of the wheeled tractor self-propelled chassis СШ2540 by simulating the operation of a hydraulic cylinder with a one-sided rod for moving the steering trapezoid when turning the wheels and studying the change in the pressure of the working fluid and the movement of the hydraulic cylinder rod under different load modes. Research methodology. The method of simulation modeling is used, when the variables describing the behavior of the steering hydraulic cylinder are determined by certain load algorithms and operating fluid flows, and are described by differential equations. The differential equations that determine the pressure of the working fluid in the cavities of the hydraulic cylinder and the movement of its rod when the working fluid is fed into the piston or rod cavity are based on the laws of mechanics, the principle of the continuity of the flow of the working fluid and its compressibility. The VisSim package of application programs was used for modeling according to the proposed methodology. The changes of the parameters in the hydraulic cylinder of turning the wheels when they are shifted from the task of the control action in the form of an increase in the external load and the flow of the working fluid in the output channels of the metering pump overcome by the hydraulic cylinder were studied. The influence of the modulus of elasticity of the working fluid, which decreases when it is saturated with undissolved air, was also investigated. The results. When starting the hydraulic steering drive, i.e. when turning the steering wheel from its neutral position, depending on the external load and the intensity of the driver's work at the wheel, oscillatory processes take place in the hydraulic cylinder cavities, which can significantly exceed the working pressure. The results of the research give a reason to conclude that it is necessary to study the nature of the increase in the flow rate and pressure of the working fluid on a full-scale sample of the tractor chassis metering pump, i.e. by replacing the flow rate simulation with its actual value. Setting the loading time and flow rate of the working fluid using the map-VisSim unit is more convenient than setting it with analytical expressions, as it makes it possible to simulate different acceleration rates of the hydraulic cylinder and, if necessary, to control the stationary mode of the steering wheel in the neutral position.

Analysis of the technical level of hydraulic fluid power with motor-wheels

The analysis of the use of hydraulic fluid power of rotation of hydraulic motor-wheels for tracked and wheeled machines was carried out. The hydraulic principle schemes for the use of high-speed axial-piston hydraulic motors with planetary gearboxes and high-torque low-speed radial-piston hydraulic motors are considered, in particular, hydraulic devices for ensuring reliable movement in the event of obstacles from the road surface. The features of static and dynamic calculation methods using a mathematical model for the numerical solution of differential equations when calculating pressure fluctuations and the frequency of rotation of hydraulic motors depending on the tasks of changing the intensity of the pump supply and the working volume of the hydraulic motor, taking into account its efficiency, are shown. A comparative analysis of the technical level of hydraulic motor-wheels was carried out and a significant increase in the output parameters of high-torque radial piston hydraulic motors with respect to pressure, rotation frequency and mass-to-torque ratio was revealed. The article may be useful for engineers, scientists and master's students.

Analyzing the possibility of using hiqhtorque hydraulic motors for rotation of the drums of automatic concrete mixers

Goal. The goal is conducting an analysis of the use of hydraulic fluid power for rotating the drums of concrete mixers, in particular, evaluating the possibility of using high-torque low-speed radial-piston hydraulic motors instead of axial-piston motors with planetary gearboxes. The technical level of such hydraulic drives is assessed based on the use of mass to torque and power ratios. The nomenclature, technical characteristics and design features of high-torque hydraulic motors are considered. In particular, compared to previous studies, the nomenclature of the considered hydraulic motors is widespread. Method. The methods of comparative analysis of designs and technical characteristics of axial-piston with planetary gearboxes and high-torque hydraulic motors according to the main technical parameters, in particular, the developing pressure, torque, rotation frequency and power depending on the specific indicators of the mass ratio to the absolute values of these parameters were used. Design features of high-torque hydraulic motors were also considered. Originality. For the first time in the domestic literature, a comparative analysis of the performed high -motion hydraulic motors of the MCR model was carried out. Results and practical usefulness. It is recognized that the modern technical level of high-torque hydraulic motors allows to compete with axial-piston gear hydraulic drives for rotating drums with a concrete mixture of auto-concrete mixers. The given materials will be useful in the educational process for machine-building specialists who study hydraulic fluid power as a means of improving the technical level of various machines and mechanisms.

ANALYSIS OF TECHNICAL CHARACTERISTICS OF HIGH TORQUE HYDROMOTORS WITH LIMITATIONS BASED ON DYNAMIC CALCULATIONS

The goal is to study the technical characteristics of the world's largest modern high-torque multi-acting hydraulic motor from the point of view of ensuring reliable operation by the manufacturer at elevated pressures, speeds and depending on the type of working fluid used. Analysis of the influence of dynamic loads on fluctuations in pressure and speed of the hydraulic motor in the modes of starting and braking, taking into account changes in the pump flow rate and inertial loads. Method. Dynamic calculation of a hydraulic fluid power with a high-torque hydraulic motor based on studies of external loads, changes in the pump feed time, providing the maximum speed. To solve nonlinear differential equations when calculating the pressure in the hydraulic drive and the rotational speed of the hydraulic motor, the VisSim application software package was used. The modes of change in the operation of the hydraulic motor over time in terms of rotational speed, pressure in the hydraulic fluid power, output power and hydromechanical efficiency, depending on the external load and pump flow, are presented on the corresponding oscillograms. The mathematical model of the hydraulic fluid power includes simulation modules for controlling the supply of an axial piston pump and changing the moment of resistance on the hydraulic motor. Results. Calculations of the dynamics of a hydraulic fluid power with a high-torque multi-acting radial piston hydraulic motor showed the need for preliminary modeling of its operation modes, taking into account the nature of the external loading, the moment of inertia and the intensity of the pump flow. Conclusion. The conducted studies can be used in the development of hydraulic fluid power with high-torque hydraulic motors to clarify the technological processes of work during the operation of a hydraulic machine.

TO THE MODERNIZATION OF HYDRAULIC FLUID POWER OF WHEEL EARTH MACHINE BASED ON HTZ TRACTORS

The purpose of the article is to scientifically search for the possibility of replacing mechanical drives of a chain working body and a rotary soil thrower of an earth-moving trenching machine with a hydraulic fluid power in order to increase reliability and effective protection against overloads.Studies have been carried out on the load characteristics of earth-moving machines of the PZM-2 (3) type and an assessment of the possibility of replacing the rotation of the chain working body and the rotary thrower of the dumped soil with the selection of hydraulic motors and pumps for a hydraulic fluid power. Hydraulic actuators must provide operation during the starting mode, minimal power loss during idling and effective protection in the event of a sudden stop of thehydraulic motors due to overloads.As a result of the calculations, it was found that for the hydraulic fluid power of the chain working body earthmoving trencher, high-torque low-speed radial piston hydraulic motors of single or multiple action with a working volume of 1800 ... 2500 cm3, as well as high-speed axial piston hydraulic motors with planetary gearboxes, for a rotary thrower of dumped soil, gerotor hydraulic motors with a working volume of about 200 cm3. The hydraulic motors required by the workingvolume are mass-produced by a number of foreign companies. To supply the working fluid to the hydraulic motors, axial piston tandem pumps with adjustable displacement, which are produced by the Hydrosila plant, are recommended.The results of the research can be used in the development of a new generation of earth-moving trenching machines when replacing the mechanical drive of the chain working body and the thrower of the dump soil with a hydraulic fluid power.

Аnalysis of energy saving methods servic-ing airfields and airplanes

Problem. The problem is an integral part of developing the concept of forming a standard range of transport and technological hydrophilic modular means for maintenance of airfields and aircraft. Goal. The goal is development of scientifically sound recommendations for determining the rational parameters of the hydraulic system with automation of control and energy saving during operation of modular vehicles for maintenance of airfields and aircraft, taking into account the potential of domestic engineering and critical imports of units and assemblies. Methodology. The methods include analysis of energy saving methods in hydraulic fluid power of mobile machines according to manufacturers' catalogs and industrial examples taking into account the needs of modular vehicles for maintenance of airfields and aircraft, in particular, taking into account the creation of modern hydraulic devices and circuit solutions in hydraulic drives with throttle and machine control and automatic regulators of change of hydraulic fluid power. Results. It is established that in hydraulic drives with throttle control and pumps with unregulated working volume, throttles on parallel flow and three-wire flow regulators or LS and LUDV modern systems are used; automatic pressure and flow regulators are used with pumps with adjustable displacement; in machine-controlled hydraulic drives through the use of pumps and hydraulic motors with adjustable displacement and hydraulic automation; by energy recovery during operation and bench tests of hydraulic drives; at the design stage of hydraulic drives, when the static analysis is performed in terms of efficiency and dynamic to reduce the loads on the starting modes of operation; and also at designing lay the effective circuit technical decisions promoting energy saving; directly in operation due to high-quality working fluids, heat exchange systems and filtration. Originality. The classification of methods of energy saving in volumetric hydraulic drives of mobile machines is made and examples of application of some means which are planned for introduction in transmissions and the technological equipment of cars for service of aerodromes and planes are resulted. Practical value. The possibility of a rational selection of axial-piston domestic hydraulic machines for the development of hydraulic drives for airfields and aircraft is proven.

Analysis of modern technical means for servicing airports and airplanes

Problem. The problem is an integral part of developing the concept of forming a standard range of transport and technological hydrophilic modular means for maintenance of airfields and airplanes. Goal. The goal is development of scientifically sound recommendations for determining the rational parameters of the hydraulic system with automation of control and energy saving during operation of modular vehicles for maintenance of airfields and aircraft, taking into account the potential of domestic engineering and critical imports of units and assemblies. Methodology. The methods include analysis of energy saving methods in hydraulic fluid power of mobile machines according to manufacturers' catalogs and industrial examples taking into account the needs of modular vehicles for maintenance of airfields and aircraft, in particular, taking into account the creation of modern hydraulic devices and circuit solutions in hydraulic drives with throttle and machine control and automatic regulators of change of hydraulic fluid power. Results. It is established that in hydraulic drives with throttle control and pumps with unregulated working volume, throttles on parallel flow and three-wire flow regulators or LS and LUDV modern systems are used; automatic pressure and flow regulators are used with pumps with adjustable displacement; in machine-controlled hydraulic drives through the use of pumps and hydraulic motors with adjustable displacement and hydraulic automation; by energy recovery during operation and bench tests of hydraulic drives; at the design stage of hydraulic drives, when the static analysis is performed in terms of efficiency and dynamic to reduce the loads on the starting modes of operation; and also at designing lay the effective circuit technical decisions promoting energy saving; directly in operation due to high-quality working fluids, heat exchange systems and filtration. Originality. The classification of methods of energy saving in volumetric hydraulic drives of mobile machines is made and examples of application of some means which are planned for introduction in transmissions and the technological equipment of cars for service of aerodromes and planes are resulted. Practical value. The possibility of a rational selection of axial-piston domestic hydraulic machines for the development of hydraulic drives for airfields and aircraft is proven.

FEATURES OF THE DYNAMICS OF HYDRAULIC FLUID POWER DEPENDING ON THE MODES OF EXTERNAL LOADING

An aim is a scientific search of possibility of replacement of mechanical drive of rotation of rotor thrower of earthmover on hydraulic fluid power and determination of his dynamic descriptions on the basis of mathematical model, that examines the modes of starting, set motion, and his sudden stopping for an insuperable obstacle from the side of the poured out soil. Method. Static calculation of by hydraulic fluid power on the basis of researches descriptions of loading of working organs of earthmovers and dynamic calculation with the use of package applied programs of VisSim. The mathematical model of hydraulic fluid power includes the imitation modules adjusting of serve of axial piston pump and change of moment of resistance on the modes of starting of hydromotor at idling motion, normal ladening of rotor thrower and sudden stop. Results. For by hydraulic fluid power of rotation of thrower of earthmovers machine can be applied gerotor hydromotors with the swept volume to 200 cm3, and also high-speed axial piston hydromotor with reducing gears. Necessary on the displacement gerotor hydromotors are mass-produced by the row of foreign firms. The calculation of dynamics of hydraulic fluid power showed that at the critical mode of sudden stop of rotor thrower at his hit on an insuperable obstacle from the side of soil, there are attenuation pressure fluctuations. The worked out program of design can be substantially used for the use of other values of loading and frequency of rotation of hydromotor. Conclusion. Results undertaken studies can be drawn on at development of earthmovers of new generation at substituting of mechanical drive of rotor thrower by hydraulic fluid power.

Dynamics of the hydraulic fluid power of rotation of the hose concrete pump

Purpose. Search for ways to improve the technical level of the hydraulic fluid power of a hose concrete pump by analyzing the hydraulic schematic diagram and dynamic characteristics depending on the moment of resistance, moment of inertia and properties of the working fluid. Method. The construction of a mathematical model of the dynamics of a hydraulic fluid power is based on Newton's laws of mechanics, Pascal's law and the continuity equation for fluids. The dynamics study was implemented using the VisSim package. The results of studies of the influence of variable parameters on the rotor speed and pressure in the discharge line of the hydraulic motor are presented in graphical form. Results. It was found that in a volumetric hydraulic fluid power of a concrete pump with rotor rotation from a gerotor hydraulic motor, there are significant fluctuations in pressure and speed, due to the kinematics of the pump, temporary factors of the increase in the moment of resistance and supply of the working fluid to the hydraulic motor with the throttle method of its regulation. The ratio of the maximum and steady-state pressure values is 1,9 times obtained for hydraulic motors of different displacement. The possibilities of reducing the dynamic loading of the hydraulic fluid power by improving its hydraulic schematic diagram and control algorithm are shown. Conclusion. Recommendations have been developed for reducing dynamic loads in a hydraulic fluid power by modernizing the hydraulic circuit diagram by introducing electrohydroautomatics devices and changing the algorithm for starting and stopping the pump.

Novel Integrated Active and Passive Control of Fluid-Borne Noise in Hydraulic Systems

Abstract Fluid-borne noise (FBN) is a major contributor to structure-borne noise (SBN) and air-borne noise (ABN) in hydraulic fluid power systems and could lead to increased fatigue in system components. FBN is caused by the unsteady flow generated by pumps and motors and propagates through the system resulting in SBN and ABN. New hydraulic technologies such as digital switched hydraulic converters also generate unavoidable FBN. This article reports on a novel integrated FBN attenuation approach, which employs a hybrid control system by integrating an active feed forward noise attenuator with passive tuned flexible hoses. The active system which consists of adaptive notch filters using a variable step-size filtered-X Least Mean Squares algorithm is used to control a newly designed high-force high-bandwidth piezoelectric actuator in order to attenuate the dominant narrowband pressure ripples. The passive hose is tuned in the frequency domain and used to cancel the high-frequency pressure ripples. A time-domain hose model considering coupling of longitudinal wall and fluid waves was used to model the flexible hose in the integrated control system. Very good FBN cancellation was achieved by using the integrated control approach in simulation and experiments. It is an effective, cost-efficient and practical solution for FBN attenuation. The problem of high noise levels generated by hydraulically powered machines has risen significantly in awareness within industry and amongst the general public, and this work constitutes an important contribution to the sustainable development of low noise hydraulic fluid power machines.

To the choice of materials of working and distributive links of by displacement hydraulic mashines for the needs of building-travelling industry.

Search of ways of increase of technical level and reliability of by hydraulic fluid power of rotatory motion for building and travelling machines. Analysis of designer and technological decisions in part of choice of materials of pairs of friction of working links and distribution of working liquid in by displacement hydraulic mashines – pumps and hydraulic motors with the purpose of acquaintance of specialists with advanced experience in this type of technique. Method. On the basis of mathematical model of dynamics of hydraulic fluid power by means of application of VisSim package the estimation of intensity of height of extreme values of pressures is conducted from character of action of the external loading on hydraulic motor at starting of hydraulic fluid power. Results. It is set that in by hydraulic fluid power can take place substantial vibrations pressures exceeding almost in two times the set values in the technological mode of operations of machine. Conclusion. Depending on the fast-acting of loading on hydraulic fluid power of machine a preliminary dynamic design the value of the capacity of hydraulic motors gets out on results that is recommended for providing of supply on working pressure. The brought information over about the applied pairs of friction of hydromashines and their thermo-chemical treatment can be useful to the specialists at planning of new hydraulic mashines, and repair of exploited.

Solution of the multi-criteria problem of optimization of a gear pump by the method of research of the space of parameters

Introduction. Gear pumps are one of the main sources of hydraulic energy for hydraulic fluid power of a number of machines for national and special applications. Improving the characteristics of the gear pump of the external gearing is based on a search for the gearing parameters of the gear pump in terms of reducing the overall size while maintaining the value of the working volume set by the customer, which is the subject of the formulation and solution of multicriteria optimization problemsProblem. Improving the characteristics of the gear pump of the external gearing is based on the search for the parameters of the gearing of the gear pump in terms of reducing the overall size while maintaining the value of the working volume set by the customer. In the studies of a number of authors, the problems of reducing velocity and pressure pulsations, optimizing gearing parameters, and determining the geometry of gear pump cavities are separately solved. However, a multicriteria approach to gear pump is absent, which narrows the range of positive results obtained by studying the quality of the developed design.Method. A method for studying the parameter space for a gear pump is proposed. This method makes it possible to work with models of various nature due to the absence of any restrictions imposed on functions, including quality functions (smoothness, continuity), the designer is not required to rank criteria, assign weighting factors, limits and restrictions, it is possible obtaining information about the behavior of the criteria and restrictions in the parameter space under study with the minimum calculation time due to the simplicity of data analysis.The practical results. The mathematical model of the gear pump is improved by introducing the equations of the radial and normal lateral gaps, which increased its adequacy to the full-scale sample. As a result of the multicriteria optimization, the overall dimensions of the pump were reduced by 7% while ensuring a given value of the working volume.

ANALYSIS OF UNIVERSAL CHARACTERISTICS OF HYDRAULIC FLUID POWER TRANSMISSIONS OPERATING IN A COMPOSITION OF HYDRAULIC-MECHANICAL TRANSMISSIONS FOR DIFFERENT WORKING VOLUMES OF HYDRAULIC MACHINES OF AXIAL PISTON TYPE

When victorious in the day-to-day infrequent hydraulic fluid power mechanical transmissions (HVMT), the hydraulic fluid power transmissions (HVT)), which are supported by the implementation of all the demands of the daily transport diesel engine, are absolutely necessary in a wide range of for the analysis of the flow of pressure in the HVMT, coefficient of efficiency, thermal images in the motor-transmission drive, traction and propulsive characteristics of the transport machine. More informational and effective when analyzing the universal characteristics of the HVT, which should be entered before the HVMT warehouse. The statute is assigned to the scientific enrichment of the need for a recurrent procedure in the case of the value of the working parameters of the HVT, the automated inducement of the universal characteristics of the hydraulic volume transmissions, the adjustment of the characteristics for the different working types of the central storage of the hydraulic drives.

Use of dynamic modeling of VisSim in teaching the discipline «Design and Testing of Hydraulic Fluid Power»

The widespread use of hydraulic fluid drive in modern road-building and hoisting machines with electrohydroautomation and energy saving requires an increase in the level of education of future specialists for successful work at operation and modernization of the domestic fleet. Problem. Increasing the level of training masters on the basis of familiarization with modern means of analyzing the dynamics of hydraulic fluid drives, corresponding to the curriculum of the discipline «Design and testing of hydraulic drives» at the mechanic faculty of the Kharkiv National Auto-Road University. Method . A review of educational literature and the mathematical models of hydraulic fluid drive of reciprocating and rotational motion is made. The package of dynamic modeling VisSim for solving the problems of dynamics in hydraulic fluid drives of road construction, hoisting and transport, utility and land reclamation machines was used on a practical example. Practical results. The study shows a mathematical model of hydraulic fluid drive with a closed circuit of working fluid circulation, including a pump with an adjustable working volume and a hydraulic motor with a constant working volume, the important effect of the pump output time on the maximum flow on the pressure fluctuations in the hydraulic system. Conclusion . The discipline «Design and testing of hydraulic actuators» is provided with methodological manuals, information about modern hydraulic devices and hydraulic drives of mobile machines. For the first time, mathematical modeling was used to study the dynamics of hydraulic fluid power using the VisSim application program. Mathematical modeling of hydraulic fluid drive is recommended for use by students when performing course and diploma works.

CALCULATION OF VOLUME HYDRAULIC DRIVE FOR FEEDING THE CHIPPER OF WOOD WASTEWITH A RETURN ON OVERLOADS

Development of recommendations on introduction of technology of "No stress" of safe automatic return of woodwastes in by hydraulic fluid power of serve of machines for growing on the basis of the use of home valve. Analysis of hydraulic fundamental charts of by hydraulic fluid power of serve of machines for growing of the woodwastes provided with the devices of automation of their return from the zone of cutting for providing of increase of safety and productivity of machine shallow. Development of methodology of calculation of by hydraulic fluid power of serve in machines for growing of woodwastes shallow. The hydraulic fundamental chart of hydraulic fluid power of serve of grinding down of woodwastes offers for realization in designer developments, in that on the basis of the use of home valve with the devices of self-reset of slide-valves the mode of safety of "No stress" will be realized in neutral position. Methodology of calculation of by hydraulic fluid power is considered, including determination КПД, choice of the swept volume of pump and hydraulic motor, leading engine and diameters of pipelines. The brought equalizations over of mathematical model for the dynamic calculation of frequency of rotation of hydraulic motor and pressure of working liquid in by hydraulic fluid power of grinding down, that can be realized as oscillograms in an application of package of VisSim package. Results undertaken studies can be drawn on at development of new by hydraulic fluid power of serve for grinding down of woodwastes or modernisation being in exploitation.

STEM Education Using Emulation Software for Hydraulic Fluid Power Applications

STEM education is an indispensable method to prepare students for future careers in engineering and manufacturing. Tools such as simulation software provide one way to explore and expand high school students’ knowledge of hydraulic fluid power systems. Traditionally, hydraulic fluid power college courses have used a physical trainer equipped with cylinders, valves and hoses that demonstrate various circuits important to the understanding of fluid flow and system characteristics. Using Simumatik3D, a free downloadable emulation software developed in Sweden, a group of high school students were able to assemble an emulated environment where they can create new hydraulic circuits, allowing them to learn outside of the classroom and preparing them for classroom activities with a real physical trainer. The software system was selected as the platform to emulate the trainer because of the ease of use, its 3D environment and the potential for future expansion into electromechanical emulations that leverage the use of Programmable Logic Controllers (PLCs) and Robotics. Preliminary results of a small sample of high school students show that students were responsive to the Simumatik3D software and that the project met several best practices for engineering STEM applications.

A Hybrid Lumped Parameters/Finite Element/Boundary Element Model to Predict the Vibroacoustic Characteristics of an Axial Piston Pump

Low noise axial piston pumps become the rapid increasing demand in modern hydraulic fluid power systems. This paper proposes a systematic approach to simulate the vibroacoustic characteristics of an axial piston pump using a hybrid lumped parameters/finite element/boundary element (LP/FE/BE) model, and large amount of experimental work was performed to validate the model. The LP model was developed to calculate the excitation forces and was validated by a comparison of outlet flow ripples. The FE model was developed to calculate the vibration of the pump, in which the modeling of main friction pairs using different spring elements was presented in detail, and the FE model was validated using experimental modal analysis and measured vibrations. The BE model was used to calculate the noise emitted from the pump, and a measurement of sound pressure level at representative field points in a hemianechoic chamber was conducted to validate the BE model. Comparisons between the simulated and measured results show that the developed LP/FE/BE model is effective in capturing the vibroacoustic characteristics of the pump. The presented approach can be extended to other types of fluid power components and contributes to the development of quieter fluid power systems.

Preliminary Design and Engineering Evaluation of a Hydraulic Ankle–Foot Orthosis

Ankle foot orthoses (AFOs) are used to correct motor impairments of the ankle. While current AFOs are passive, advances in technology and wearable robotics have opened the opportunity for a powered AFO. The hydraulic ankle foot orthosis (HAFO) is a device that takes advantage of the exceptional power-to-weight and force-to-weight of hydraulic fluid power. The device is untethered, and the power transmission chain is battery–electric motor–hydraulic pump–hose–cylinder, with the power supply worn at the waist and the cylinder actuators at the ankle. The fluid power circuit is configured as an electrohydraulic actuator (EHA) that is controlled by controlling the electric motor. The first prototype weighs 3.3 kg of which 0.97 kg is worn at the ankle. Steady-state torque–velocity performance showed that the prototype can provide 65 N·m of assistance torque and a no-load velocity of 105 deg/s. Closed-loop position control showed low steady-state error but a slow response. The current prototype demonstrates the potential of hydraulics for providing large torques in a compact, lightweight device. The speed performance of the prototype is inadequate for normal walking but can be improved by switching to servo valve control or by developing a custom hydraulic pump.