Hydraulic Power Supply Research Articles

A systematic management and control methodology for high energy saving in applications equipped with hydraulic servo-axes

A systematic methodology for the real-time improvement of the overall efficiency of applications using hydraulic servo-axes is presented. The proposed methodology introduces three modules: a hydraulic actuator load estimator, a hydraulic energy optimizer and a controlled hydraulic power supply; these are discussed at the theoretical and application level. The proposed approach reduces the power losses across the main elements of the hydraulic circuit, leading to high energy savings and introducing a new guideline on managing and controlling the servo hydraulic actuator. The methodology is applicable to any application using hydraulic servo-axis systems, and therefore it is not tailored to a particular field. Its performances have been evaluated in different industrial case studies (a blanking press, a drawing press and a die-casting plant) through numerical simulations. Conspicuous energy savings, ranging between 59% and 88%, have been obtained in simulation, suggesting that a significant carbon footprint reduction for energy-intensive hydraulic machinery is achievable in a wide range of applications.

Downsizing the electric machines of energy-efficient electro-hydraulic drives for mobile hydraulics

The poor energy efficiency of state-of-the-art mobile hydraulics affects the carbon dioxide released into the atmosphere and the operating costs. These crucial factors require urgent improvements that can be addressed by the electrification of fluid power. This approach has already generated electro-hydraulic drives that remove flow throttling and enable energy recovery. However, the entire power managed by the actuators of conventional systems must pass through the electric machines. This characteristic is unfeasible for medium-to-high power applications since they need electric motors and electronics with high power ratings and large onboard generation of electricity. Thus, this paper applies to a hydraulic excavator’s boom the idea of splitting the power being transferred to/from the actuator between the hydraulic and electric domains (i.e., a centralized hydraulic power supply is involved). The objective is downsizing the power rating of the boom’s electric components while maintaining the high-power output of the hydraulic actuator. The results show the expected behavior of the hybrid excavator in terms of motion control, but only 57% of the boom’s peak power is now exchanged electrically. The resulting electric machine with 61% downsizing favors the system’s cost and compactness supporting the electrification process that is aligned with the low-carbon economy.

Test bench for the assessment of vibrations occurring in motorcycles

The purpose of this publication is to present the construction and adaptation of the test stand intended for motorcycle simulation research. The stand is designed to study the impact of motorcycle vibrations that act on the body of the driver and passenger. Motorcycles belong to one of the types of transport that directly affects users. Excessive vibrations transmitted to the body of the driver and passenger can make driving uncomfortable and even dangerous. The vibrations of motorcycles depend mainly on the technical condition of the vehicle, the structure of the vehicle, and the construction of the engine. The stand was built on the basis of a hydraulic power supply unit, distributor, and electrohydraulic pulsators. The purpose of the construction of the stand is to examine a given group of motorcycles to learn and eliminate vibrations that occur in various areas of motorcycles and affect the comfort, health, and safety of motorcycle travelers. Test studies of the presented stand are presented in this article. The preliminary results of the simulation tests determined the possibility of testing individual elements and motorcycles on the laboratory stand.

Validation of the safety requirements of the landing gear using fault tree analysis

We analyze the functionality of the landing system of a regional aircraft in the extension and cruise flight modes and validate safety requirements through the fault tree analysis. The main landing gear system is captured in the electromechanical–fluidic domain and system behavior is abstracted in an elementary hydraulic circuit. The functional representation is then constructed into a fault tree which allows analysis of the failure propagation originating at different branch terminals, for instance, at the main landing gear actuator which extends the gear and holds it retracted during the cruise, door actuator, door uplocks, and hydraulic power supply. Each component is assigned a failure probability. Each failure mode is abstracted as a top-level event having a probability of failure and through Boolean combinations of component failures in the lower branches. Two reliability aspects considered are the availability to fully lower the landing gear and the integrity of inadvertent gear or door extension while cruising. Architectural changes through undercarriage system reconfiguration and component redundancy have been exploited to improve system failure rates. The analysis determines the overall system failure rate against the flight cycles. The process is agile to accommodate design changes with the evolution of architecture during the systems engineering lifecycle.

A Study on the Internal Flow Analysis in Swash Plate Piston Pump for Marine Hydraulic Power Supply

A Study on the Internal Flow Analysis in Swash Plate Piston Pump for Marine Hydraulic Power Supply

A Study on the Structural Stability of the Swash Plate Piston Pump for Marine Hydraulic Power Supply

A Study on the Structural Stability of the Swash Plate Piston Pump for Marine Hydraulic Power Supply

Numerical investigation of the influence of the inlet nozzle diameter on the degree of fluid exchange process in a hydraulic cylinder

Operation of heavy-duty machines leads to an observation that seals in hydraulic cylinders are frequently subjected to thermal degradation. The basis of this research is the previously proven thesis that the temperature of the liquid in the cylinder and the cylinder itself may significantly differ from the temperature of the liquid in the system and in the tank, thus enabling the temperature in the cylinders to rise above the operating temperature of the seals. This effect is a result of limited possibility of fluid exchange in the cylinder during operation. This paper presents simulation results of the liquid mixing phenomenon in the chamber of a hydraulic cylinder with a modified hydraulic power supply system. The article focuses on determining the influence of the diameter of the supply nozzle, and thus the change of the potential energy of the stream supplying the cylinder chamber, on the liquid exchange process, which was defined by the thermal balance of the system. The proposed method allows designing of hydraulic cylinders in order to maintain constant temperature conditions in each part of a cylinder and thus eliminate thermal degradation of sealing. The research was based on an experimentally verified CFD model of the cylinder chamber.

GROUND-BASED EXPERIMENTAL TESTING OF ELEMENTS OF AUTOMATION OF PNEUMATIC-HYDRAULIC SYSTEMS OF ROCKET AND SPACE TECHNOLOGY

The design and production of sophisticated technical systems, which include modern rockets and other aircraft, requires their reliability and trouble-free operation. To achieve the required level of reliability of aerospace products, a wide variety of test methods are applied at all stages of the life cycle. One of the most important systems of the launch vehicle is the pneumatic hydraulic power system of the liquid rocket propulsion system. Development of new and improvement of existing methods of control and diagnostics is one way of increasing the design and technological reliability of products of aviation and space technology. The use of functional diagnostics systems for bench and flight tests significantly increases the reliability and efficiency of space rocket technology. Researches are directed on increase of a level of reliability of products of aerospace branch. Application of systems of functional diagnostics is described at bench tests. The results of experimental researches of elements of automatics of pneumatic hydraulic power supply systems of liquid rocket engines are considered. The technique of processing of experimental data of a pulsing-acoustic method of diagnostics with use of the mathematical technology of recognition of images is presented. Deciding rules of recognition of a technical condition of object of diagnosing by results of tests are resulted. The developed method with a high degree of accuracy allows to determine the technical condition of the object of diagnosis as defective or to detect the presence of characteristic defects. Experimental testing and the proposed method of processing the results showed the efficiency of the method.

Comparative analysis of hydraulic power systems for a powered roof support aimed at obtaining optimal power parameters

Hydraulic power systems for powered roof supports, depending on the place of installation of hydraulic aggregates, can be divided into local and central systems. Central systems are gaining popularity and a number of their features are more advanced compared to the local system. However, it is widely believed that their main disadvantage is the necessity to install pipelines with larger lengths, which can have a significant impact on the obtained hydraulic power supply parameters by occurring pressure losses on the pipeline length. This paper discusses the impact of these parameters on the correct operation of the powered roof support section, which is connected with the uninterrupted continuity of the production cycle in a longwall.

Design and Advanced Control of Intelligent Large-Scale Hydraulic Synchronization Lifting Systems

Lifting systems are in great demand since more and more massive buildings or bridges tend to be shifted or lifted integrally. Hydraulic cylinders in traditional lifting systems are usually supplied by a common pump with an oil tank, which brings long distance hydraulic pipes and signal lines. This paper designs a new architecture of an intelligent lifting system, with self-contained hydraulic power supply system, wireless communication modules, and distributed controller. Based on the designed architecture of the intelligent lifting system, an advanced iterative learning control strategy is proposed to enhance its synchronization performance. With the proposed advanced control strategy, synchronization is achieved in a finite time interval even under the effect of communication time delays and saturations. The distributed controller of a lifting subsystem only uses the delayed information received from subsystems around. This is distinguished from traditional lifting systems, in which all of the lifting subsystems are normally controlled in a centralized way.

Investigation of the Integrated Control System of a Helicopter Type Aircraft in Case of Onboard Equipment Failures

The complex control system of the helicopter-type aircraft is considered, its design is described depending on the requirements for the aircraft and interaction with the interfaced onboard equipment. The main elements of the system are the subsystems of remote and automatic control of the helicopter. In the process of developing such a system, much attention is paid to ensuring a high level of reliability and maintaining the functions necessary for the safe completion of the flight. Therefore, the main requirement for an integrated management system is the probability of its failure in backup management with improved stability of the control object is not higher than 10-9. The authors of the article conducted the analysis of the integrated management system on accutanecost in conditions of failure of the elements included in its composition. In the course of the analysis the assessment of fault safety of subsystems of remote and automatic control is carried out. At the same time, for each system, the influence of obvious and not obvious failures on the change in the controllability of the aircraft and the safety of its flight was considered. Also, the analysis of the system in the conditions of failure of the on-Board equipment of the device. Special attention is paid to the study of the dynamics of the Executive mechanism of the system in the conditions of failure of the onboard hydraulic power supply system. The paper presents the results of studies of changes in the force, speed and quality factor of the electrohydraulic drive at various failures of hydraulic power lines on Board the aircraft. The obtained results can be used in the process of designing complex control systems, studies of electrohydraulic drives and development of methods for parrying the consequences of failures of the helicopter’s onboard equipment with respect to the complex control system, including the creation of algorithms for reconfiguring the system and the logic of controlling the functioning of its elements.

Decentralized Compact Hydraulic Power Supply by High Speed Components

Decentralized Compact Hydraulic Power Supply by High Speed Components

Effects of splined shaft bending rigidity on cylinder tilt behaviour for high-speed electro-hydrostatic actuator pumps

High-speed axial piston pumps are hydraulic power supplies for electro-hydrostatic actuators (EHAs). The efficiency of a pump directly affects the operating performance of an EHA, and an understanding of the physical phenomena occurring in the cylinder/valve plate interface is essential to investigate energy dissipation. The effects of the splined shaft bending rigidity on the cylinder tilt behaviour in an EHA pump need to be considered, because the deflection and radial expansion of a steel shaft rotating at a high speed cannot be ignored. This paper proposes a new mathematical model to predict the cylinder tilt behaviour by establishing a quantitative relationship between the splined shaft deflection, the cylinder tilt angle, and the tilt azimuth angle. The moments exerted by the splined shaft are included in the equilibrium equation of the cylinder. The effects of solid and hollow splined shafts equipped in an EHA pump prototype are compared at variable speeds of 5000–10,000 r/min. With a weight saving of 29.7%, the hollow shaft is experimentally found to have almost no influence on the volumetric efficiency, but to reduce the mechanical efficiency by 0.6–2.4%. The results agree with the trivial differences of the simulated central gap heights of the interface between the two shafts and the enlargement of the simulated tilt angles by the hollow shaft. The findings could guide designs of the cylinder/valve plate interface and the splined shaft to improve both the efficiency and power density of an EHA pump.

An integrated load sensing valve-controlled actuator based on power-by-wire for aircraft structural test

The traditional loading system, for the full-sized aircraft structure test, requires the centralized hydraulic power supply and the distributed valve-controlled cylinder, which leads to complex and large pipeline systems. The layout reconfiguration process of the test platform is quite laborious. Moreover, the loading system efficiency is quiet low because of both the huge overflow loss and the huge throttling loss of the traditional valve-controlled system. In order to conduct the structure test more efficiently, this paper proposes a novel integrated Load Sensing Valve-Controlled Actuator (LSVCA) with high efficiency and low energy consumption, which can reduce the overflow loss by the intermittent operation of the motor and reduce the throttling loss by the variation of the supply pressure. It also simplifies the test platform reconfiguration due to its high-level integration and Power-By-Wire (PBW) feature. In this paper, the hydraulic working principle and the energy-saving analysis of the LSVCA is proposed. In order to verify the feasibility of the new principle and the effectiveness of the high efficiency, the mathematical model of the LSVCA is established. Furthermore, an experimental prototype of the LSVCA is tested. Test results indicate that the LSVCA is adequate to satisfy the criteria for full-sized aircraft structure test. The throttling efficiency of the LSVCA loading system is 1.75 times of the efficiency of the traditional loading system under the low-level load pressure condition.

Design and locomotion control of a hydraulic lower extremity exoskeleton for mobility augmentation

In this paper, a system design and three locomotion control algorithms are proposed for a hydraulic lower extremity exoskeleton to enhance mobility and reduce muscle fatigue caused by backpack loads. The range of motion of the exoskeleton and the capacity of the hydraulic power unit, which generates the hydraulic flow and pressure, are determined by analysing human walking data obtained using a motion capture device and force plates. For movement comfort, the mechanical structure and the joints of the exoskeleton are designed such that the motion of the wearer coincides with that of the exoskeleton. In addition, locomotion control algorithms for stable normal walking are described; these algorithms enable dual-mode control and transition control. Dual-mode control is comprised of an active mode in the stance phase and a passive mode in the swing phase. In the active mode, the exoskeleton is controlled to track the motion of the wearer, and in the passive mode, its active joints work as passive joints by blocking the hydraulic power supply from the hydraulic power unit. Transition control, which consists of a torque-shaping method and a pre-transition algorithm, is adopted to improve locomotion responses during gait phase transition. Finally, to verify the effectiveness of the locomotion control algorithms and the developed hydraulic lower limb exoskeleton, walking experiments are performed on a treadmill, at a speed of 4 km/h, while carrying 45 kg backpack loads. The assistance effect of the exoskeleton is also validated by comparing the electromyography (EMG) signals of four selected muscles, with and without the exoskeleton, for single stance and level walking while carrying the same 45 kg backpack loads.

Design and Experimental Evaluation of a Fast Torque-Controlled Hydraulic Humanoid Robot

This paper reports the design and control of a fast torque-controlled hydraulic humanoid robot, TaeMu. The robot has 15 active joints that are all driven by hydraulic servocylinders with an external hydraulic power supply. The 1377-mm tall robot has a three-axis active torso used for static and dynamic balancing. It weighs 72.3 kg including a dummy weight stand for the arms. Its lightweight design with carbon-fiber-reinforced plastic allows the legs to have a similar mass distribution to that of human legs. We present the details of the hardware design including the hydraulic actuator selection, mechanism, and control systems, as well as the passivity-based controller design for joint torque control and whole-body motion control. We present experimentally obtained results, such as speed testing, basic torque control testing, full-body compliant balancing with attitude regulation/tracking, and balanced full-squat motions. The experimentally obtained results and estimated joint specification imply the high potential of the robot to perform human-like motions if the researchers can invent proper control algorithms.

Energy Efficient Linear Drive Axis Using a Hydraulic Switching Converter

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 to proportional valve control. The hydraulic buck converter (HBC) represents an energy efficient and cost-effective switched inertance system, because its inductance is realized by a simple pipe. In this paper, a prototype for a hydraulic linear cylinder drive controlled by an HBC is presented. Characteristic for this drive axis is that the HBC is directly mounted on the cylinder, which allows a reduction of the oil transport loss between the axis and the hydraulic power supply unit. Furthermore, piston accumulators are used for decoupling and pressure attenuation. Due to their robustness regarding the prepressure to operating pressure, the load pressure can be controlled arbitrary in the piston-sided chamber. The energy performance and the tracking behavior of the axis with a flatness-based control (FBC) are investigated by steady-state measurements and dynamic trajectories, respectively. The results are discussed and an outlook about further improvements of the concept is provided.

System-mathematical simulation of engine air hydraulic power supply

Тhis article describes the concept of designing a pneumatic-hydraulic system of feeding fuel components to a liquid-propellant rocket engine based on mathematical models and the system approach. There are three levels of designing: the first level is that of designing separate components of the fuel feed system- at this level physical processes in the systems components are considered, their characteristics and external interactions are modeled; the second level is that of subsystems at this level the process of interaction between the systems elements is considered, internal connections between the elements and external interconnections of the systems subsystems are modeled; the third level is that of the fuel feed system as a whole -at this level the process of interaction between the subsystems is considered, internal connections between the subsystems and external connections with the engine and other systems are modeled. A multilevel mathematical model of the fuel feed system was constructed. On the basis of the model an emergency situation (a faulty element) is modeled and the element is replaced, with its characteristics in the subsystem of feeding the oxidizer to the engine being changed; the dependence of the damper blow-down parameters on the rate of change in the input flow to the engine in the course of its starting is obtained. The mathematical model is associated with resultant documents, which makes it possible to get a modified set of documentation automatically when changes are introduced in the engine fuel feed system.

Design of a portable hydraulic ankle-foot orthosis.

Small-scale hydraulics is ideal for powered human assistive devices including powered ankle foot orthoses because a large torque can be generated with an actuator that is small and light. A portable hydraulic ankle foot orthosis has been designed and is undergoing preliminary prototyping and engineering bench test evaluation. The device provides 90 Nm of ankle torque and has an operating pressure of 138 bar (2,000 psi). The battery-operated hydraulic power supply weighs about 3 kg and is worn at the waist. The ankle component weighs about 1.2 Kg and connects to the power supply with two hoses. Performance simulation and preliminary bench testing suggests that the device could be useful in certain rehabilitation applications.

Analysis by Simulation of Different Control Algorithms of A Digital Hydraulic Two-Actuator System

Many hydraulic systems have losses, which could be avoided with new technology. Because component efficiency can be optimized to a certain operation point, hydraulic machines are no worse than other machines. More important than the peak efficiency values of each individual component in a system is the efficiency of the whole power transfer line. In a system where the amount of required power and the velocity/force ratio are variables, components may but seldom operate at their optimal design points. A typical approach to mobile work hydraulics is to use a load-sensing pump for a hydraulic multi-actuator system. This approach is efficient but seldom, if many actuators are used simultaneously. Our recent prototype of an improved hydraulic power supply system is the Digital Hydraulic Power Management System (DHPMS), which can serve many actuators at optimised supply pressure but is also capable of motoring and transforming. This functionality holistically reduces losses in the system. Losses can be further ...