Conventional Hydraulic Systems Research Articles

Modeling and Characterization of Rotary Electrohydrostatic Actuators

Abstract Electrohydrostatic actuators are increasingly finding applications in different fields due to their numerous advantages with respect to electromechanical and conventional hydraulic systems. To understand their behavior, potentialities, limitations, and design aspects, the present paper deals with the modeling of such devices. The discussed phenomena are experimentally validated through the stationary and dynamic characterization tests of a rotary electrohydrostatic prototype. Results emphasize the role of mechanical and hydraulic dissipative effects and the fluid bulk modulus.

High-pressure electrorheological valve with full pQ-functionality for servohydraulic applications

Stationary and mobile hydraulic systems require switching increasing velocity, power and efficiency. Usually, their performance mainly faces physical constraints by the valves. These are in particular electrical and magnetic losses as well as various flow saturation effects. Compared to conventional valves, some of these physical constraints do not appear in electrorheological valves. However, electrorheological valves being employed as valves in conventional hydraulic systems were previously unimaginable due to the small controllable pressure differences. The presented new kind of electrorheological valve obtains a significant performance enhancement by combining the potential of conventional and electrorheological systems.

Optimised design for magnetorheological brake using DOE methods

Nowadays, the automobile systems like suspension, transmission, braking and clutch systems are controlled through the wire concept. To overcome the drawbacks of the existing conventional hydraulic braking system (CHB), magnetorheological brake (MRB) is introduced in this project. CHB require complex mechanical parts to dissipate energy. A magnetorheological fluid (MRF) brake is more efficient than conventional braking system in terms of weight reduction and response time. The research work is concerned with the development of a new braking system which employs MRF as working medium. MRB design proposed in earlier studies is to be further improved according to additional practical design criteria and constraints and more in-depth electromagnetic finite element analysis. The design procedure comprises the selection of materials for MRB, creating an analytical model for finding the braking torque produced by the MRB and finite element analysis of the MRB.

Proposal of a multiple ER microactuator system using an alternating pressure source

This paper proposes and develops a multiple ER microactuator system using an alternating pressure source for in-pipe working micromachines, medical microrobots, and so on. A hydraulic microactuator is known to have high power density but also has the drawback of requiring large piping space for the supply and return of the working fluid. In this study, an alternating pressure system with synchronized control valves and a single pipe was proposed. As the control valves, simple ER microvalves were employed. The ER microvalves control an electro-rheological fluid (ERF) flow through its apparent viscosity change due to the applied electric field. In addition, a pressure transmitter is inserted between the pressure source and the ER valves, and low viscosity fluid such as water is used to transmit the alternating pressure. The use of the low viscosity fluid can reduce the diameter of the connecting pipe due to the low pressure loss. The proposed set-up is composed of multiple ER microactuators and an alternating pressure source; each ER microactuator consists of a pressure transmitter, two ER microvalves and a hydraulic microactuator. As the proposed system has half the number of pipes, of smaller diameter, compared with conventional hydraulic microactuator systems, it is suitable for a multiple actuator system. In this study, for verification of the working principle of the proposed system, we fabricated a large model of the system which consists of an ER finger 13mm×10mm×33mm in size as a kind of ER microactuator and an alternating pressure source using a voice coil motor. Through experiments, we confirmed the tip displacement of 17mm for the 16mm-long movable part of the finger. Then, we fabricated a gripper using two ER fingers and confirmed its independent motion.

Design of Traditional Hydraulic Steering System with Variable Power

Conventional hydraulic steering system has the problems of "low-speed heavy, high-speed flight" and energy-wasting when steering, the main reason is after the system is designed, the power characteristics are fixed. To solve this problem it is necessary to achieve the power characteristics of changing power steering system according to speed of vehicles, in order to offer the power that matches the speed. Using vehicle speed sensor signal to control pilot solenoid unloading valve to regulate the pressure of hydraulic system, can achieve the regulation of power characteristics, this article is based on such idea to design variable hydraulic power steering system for hydraulic power steering system of light trucks.

Coordinate Control of Electro-Hydraulic Hybrid Brake of Electric Vehicles Based on Carsim

Motor of electric vehicle is able to be used to brake regeneratively, so braking energy can be recycled. Braking stability of electric vehicles with electro-hydraulic hybrid braking system can be influenced by braking force distribution between hydraulic braking force and regenerative braking force. In order to research on braking stability and braking energy recovery, simulation platform of electro-hydraulic hybrid brake system based on Carsim and Matlab/Simulink is built, and a control strategy of electro-hydraulic hybrid brake were proposed. The vehicle simulation models with electro-hydraulic hybrid brake system and with conventional hydraulic braking system were applied the brake on different adhesion coefficient separately. The simulation results show when electric vehicle is in the conditions of low braking intensity, all vehicle braking force is provided by regenerative braking force, and braking energy can be not only recycled, but brake performance requirement can also be satisfied; when electric vehicle is in the conditions of moderate braking intensity, regenerative braking and hydraulic braking are coordinated with each other, electro-hydraulic hybrid brake can not only satisfy the same and better brake performance, but also braking energy can be recycled and demand of hydraulic pressure can be reduced.

Design and Characteristic Analysis of Variable Speed Hydraulic System

The motor variable frequency speed control technology applied to the traditional hydraulic system based on variable speed hydraulic transmission principle with The PLC technology, hydraulic control, detection technology and configuration of organic, it combine PLC as the core of the lower machine control components, PC as the control, researched the variable speed hydraulic test system hardware, software and control systems design. The experiments were performed, realized the variable speed hydraulic experimental platform for open loop control and variable speed hydraulic system parameters real-time monitoring and dynamic display. It overcomes some of the shortcomings of the conventional hydraulic system, improved the efficiency, the hydraulic system run more smoothly and reduce noise. The experiments show that the variable speed hydraulic test bench run well and achieve the purpose.

Overview of Electric Motor Technologies Used for More Electric Aircraft (MEA)

This paper presents an overview of motor drive technologies used for safety-critical aerospace applications, with a particular focus placed on the choice of candidate machines and their drive topologies. Aircraft applications demand high reliability, high availability, and high power density while aiming to reduce weight, complexity, fuel consumption, operational costs, and environmental impact. New electric driven systems can meet these requirements and also provide significant technical and economic improvements over conventional mechanical, hydraulic, or pneumatic systems. Fault-tolerant motor drives can be achieved by partitioning and redundancy through the use of multichannel three-phase systems or multiple single-phase modules. Analytical methods are adopted to compare caged induction, reluctance, and PM motor technologies and their relative merits. The analysis suggests that the dual (or triple) three-phase PMAC motor drive may be a favored choice for general aerospace applications, striking a balance between necessary redundancy and undue complexity, while maintaining a balanced operation following a failure. The modular single-phase approach offers a good compromise between size and complexity but suffers from high total harmonic distortion of the supply and high torque ripple when faulted. For each specific aircraft application, a parametrical optimization of the suitable motor configuration is needed through a coupled electromagnetic and thermal analysis, and should be verified by finite-element analysis.

Modeling and characteristics analysis of single-rod hydraulic system using electro-hydrostatic actuator

Typical hydraulic system, although it is widely applied in industry because of its high energy density, its actual operational efficiency is only 23%–25% owing to very high energy losses, such as pressure loss and fluid dynamics loss, caused by the hydraulic system. An electro-hydrostatic actuator (EHA) system is a compact system in which an electric motor and hydraulic pump are incorporated into a cylinder, which results in greater energy efficiency than conventional hydraulic systems. The EHA system also suffers from relatively less leakage than valve-operated systems. This system consists of a bidirectional pump and a hydraulic cylinder operated by an electric motor, which adjusts the discharge flow rate of the pump by controlling the speed in both directions and changes the forward or backward direction and speed of the hydraulic cylinder accordingly. In this study, the characteristics of a single-rod cylinder load operation system, an EHA hydraulic circuit, and an electric motor are analyzed using mathematical models, and the performance of a closed-loop hydraulic control system incorporating an EHA with a rotation angle of a base plate controller is investigated.

The velocity control of an electro-hydraulic displacement-controlled system using adaptive fuzzy controller with self-tuning fuzzy sliding mode compensation

Hydraulic servo control systems have been used widely in industry. Within the realm of hydraulic control systems, conventional hydraulic valve-controlled systems have higher response and lower energy efficiency, whereas hydraulic displacement-controlled servo systems have higher energy efficiency. This paper aims to investigate the velocity control performance of an electro-hydraulic displacement-controlled system (EHDCS), where the controlled hydraulic cylinder is altered by a variable displacement axial piston pump to achieve velocity control. For that, a novel adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC-STFSMC) is proposed for velocity control in EHDCS. The AFC-STFSMC approach combining adaptive fuzzy control and the self-tuning fuzzy sliding-mode control scheme, has the advantages of the capability of automatically adjusting the fuzzy rules and of reducing the fuzzy rules. The proposed AFC-STFSMC scheme can design the sliding-mode controller with no requirement on the system dynamic model, and it can be free of chattering, thereby providing stable tracking control performance and robustness against uncertainties. Moreover, the stability of the proposed scheme via the Lyapunov method is proven. Therefore, the velocity control of EHDCS controlled by AFC-STFSMC is implemented and verified experimentally in different velocity targets and loading conditions. The experimental results show that the proposed AFC-STFSMC method can achieve good velocity control performance and robustness in EHDCS with regard to parameter variations and external disturbance. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

The Force Control of a Novel Variable Rotational Speed Hydraulic Pump-Controlled System Using Adaptive Fuzzy Controller with Self-tuning Fuzzy Sliding-mode Compensation

AbstractThe conventional hydraulic valve-controlled systems have high response but low energy-efficiency. Hydraulic pump-controlled servo systems have high energy efficiency. However, the conventional pump-controlled systems, which are altered by displacement via variable displacement pumps, have lower response. This paper aims to investigate the force control performance of the high response electro-hydraulic pump-controlled systems driven by an AC servo motor with variable rotational speed. Instead of internal gear pumps, a constant displacement axial piston pump is used in this research. Thus, the new hydraulic pump-controlled system with an AC motor servo and a constant displacement axial piston pump is investigated for force control of hydraulic servo machines. For that, a novel adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC- STFSMC) is proposed for force control in the variable rotational speed pump-controlled system (VRSPCS). Thus, the developed high response variable rotational speed pump-controlled systems controlled by AFC-STFSMC are implemented and verified experimentally for force control in different force targets. The experimental results of the force control in the VRSPCS show that the proposed system and control method can achieve excellent control performance and robustness with regard to parameter variations and external disturbance.

Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods

Perfluorinated acids (PFAs) are an emerging class of environmental contaminants present in various environmental and biological matrices. Two major PFA subclasses are the perfluorinated sulfonic acids (PFSAs) and carboxylic acids (PFCAs). The physicochemical properties and partitioning behavior for the linear PFA members are poorly understood and widely debated. Even less is known about the numerous branched congeners with varying perfluoroalkyl chain lengths, leading to confounding issues around attempts to constrain the properties of PFAs. Current computational methods are not adequate for reliable multimedia modeling efforts and risk assessments. These compounds are widely present in surface, ground, marine, and drinking waters at concentrations that vary from pg L− 1 to μg L− 1. Concentration gradients of up to several orders of magnitude are observed in all types of aquatic systems and reflect proximity to known industrial sources concentrated near populated regions. Some wastewaters contain PFAs at mg L− 1 to low g L− 1 levels, or up to 10 orders of magnitude higher than present in more pristine receiving waters. With the exception of trifluoroacetic acid, which is thought to have both significant natural and anthropogenic sources, all PFSAs and PFCAs are believed to arise from human activities. Filtration and sorption technologies offer the most promising existing removal methods for PFAs in aqueous waste streams, although sonochemical approaches hold promise. Additional studies need to be conducted to better define opportunities from evaporative, extractive, thermal, advanced oxidative, direct and catalyzed photochemical, reductive, and biodegradation methods. Most PFA treatment methods exhibit slow kinetic profiles, hindering their direct application in conventional low hydraulic residence time systems.

DIRECT DRIVE ELECTRO-HYDRAULIC SERVO ROTARY VANE STEERING GEAR

This paper describes the design and prototype of a new highly reliable rotary vane steering gear of ships which combines the benefits of conventional hydraulic systems and direct drive electrical actuators, namely high torque ratio and modularity. It is referred to as the Direct Drive Electro-Hydraulic (DDEH) servo rotary vane steering gear which results from the fusion of the above mentioned technologies. The DDEH rotary vane steering Gear, including its configuration, controlling principle and specialty, is theoretically analyzed. The mathematical models are built and the simulations of the system are made. The analysis of DDEH rotary vane steering gear is supported by simulation data which explains the extremely high level of performance attained by a prototype of DDEH rotary vane steering gear. Simulation results and its unique advantages show that DDEH rotary vane steering Gear is a prospective equipment for shipping steering which can meet performance requirements.

Robust force control of a hybrid actuator using quantitative feedback theory

The use of hydraulic systems in industrial applications has become widespread due to their advantages in efficiency. In recent years, hybrid actuation systems, which combine electric and hydraulic technology into a compact unit, have been adapted to a wide variety of force, speed and torque requirements. A hybrid actuation system resolves energy consumption and noise problems characteristic of conventional hydraulic systems. A new, low-cost hybrid actuator using a DC motor is considered to be a novel linear actuator with various applications such as robotics, automation, plastic injection-molding, and metal forming technology. However, this efficiency gain is often accompanied by a degradation of system stability and control problems. In this paper, to satisfy robust performance requirements, tracking performance specifications, and disturbance attenuation requirements, the design of a robust force controller for a new hybrid actuator using Quantitative Feedback Theory (QFT) is presented. A family of plant models is obtained from measuring frequency responses of the system in the presence of significant uncertainty. Experimental results show that the hybrid actuator can achieve highly robust force tracking even when environmental stiffness set-point force varies. In addition, it is understood that the new system reduces energy use, even though its response is similar to that of a valve-controlled system.

Design of a robust force controller for the new mini motion package using quantitative feedback theory

The use of hydraulic systems in industrial applications has become widespread due to their efficiency advantages. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Mini motion package (MMP) is one type of the new low cost hybrid actuator. This MMP is considered as a novel linear actuator with various applications such as robotics, automation, plastic injection-molding and metal forming technology. However, this efficiency gain is often accompanied by a degradation of system stability and control problems. In this paper, to maintain robust performance requirement, tracking performance specification, and disturbance attenuation requirement, the design of a robust force controller for the new hybrid actuator using quantitative feedback theory (QFT) is presented. A family of plants model for MMP is obtained from experimental frequency responses of the system in the presence of significant uncertainty. Experimental results show that highly robust force tracking by the MMP actuator could be achieved even if the stiffness of environment and set-point force change. In addition, it is understood that the new system has energy-saving effect even though it has almost the same response as that of valve controlled system.

Damage mechanism of a nodular cast iron under the very high cycle fatigue regime

Fatigue behaviour in the very high cycle regime (VHCF) of 10 10 cycles were investigated with a cast iron (GS51) under ultrasonic fatigue test system (20 kHz) in ambient air at room temperature with a stress ratio R = −1. The influence of frequency was examined by comparing similar data generated on conventional servo hydraulic test systems. An advanced, high-speed, and high-sensitivity infrared imaging system was used to measure the temperature changes during ultrasonic fatigue test at various load levels caused by internal damping due to a very high frequency cycling. The temperature field on the surface specimen was determined by using a non-destructive measurement technique called infrared pyrometer. An infrared camera made up of a matrix of 320 × 240 detectors was used. The S-N curves obtained show that fatigue failure occurred beyond 10 9 cycles, fatigue limit does not exist for the cast iron and there is no evidence of frequency effect on the test results. A detailed study on fatigue specimens subjected to ultrasonic frequency shows that the temperature evolution of the cast iron specimen is very evident, the temperature increased just at the beginning of the test, the temperature increased depending on the maximum stress amplitude. Under the current test conditions, the high cycle fatigue (VHCF) behaviour of the cast iron exhibited a typical fatigue crack growth process, that is, fatigue initiation takes place always at the surface graphite or subsurface void; the distinctive stable fatigue crack growth zone can be found around the fatigue crack initiation site, the change of fatigue initiation site from surface to subsurface is associated with the complex effects of applied maximum stress level, surface condition. Under lower stress amplitude and high cycle condition, surface graphite fatigue initiation is predominantly depended on cyclic stress amplitude; subsurface void fatigue initiation is determined by maximum cyclic stress. In the process of small crack propagation, the temperature in local plastic zone increase very sharply. The temperature field of ultrasonic fatigue specimen can be changed with the cooling condition; internal heating can accelerate surface fatigue crack initiation and propagation. Fatigue properties in VHCF regime were studied for cast iron (GS51) at 20 kHz frequency and for the first time, crack initiation and propagation stages were analyzed using a high-sensitivity infrared camera. The new Paris's model for fish eye formation in the gigacycle fatigue were also confirmed by this study.

헬리콥터 시뮬레이터용 6자유도 전기식 운동구현장치의 개발

민간항공안전국 등급 2를 만족하는 헬리콥터 시뮬레이터에 사용되는 6자유도 운동구현장치 개발에 관해 기술하였다. 운동판과 제어 구동장치의 기구학적 및 구조적 해석을 통해 설계 제작된 운동구현장치의 시험 평가로부터 규정에 만족하는 결과를 보였고 이로부터 실제 헬리콥터 시뮬레이터로의 적용 타당성을 확보하였다. 또한 동품의 개발 결과로 인해 그간 유압 구동체계를 사용한 운동구현장치의 단점을 전기식 구동장치 적용을 통해 새롭게 개선함과 동시에 국내 최초로 10 톤급의 적재하중 능력을 보유한 6자유도 운동구현장치를 보급하게 되는 계기를 마련하였다. In this paper, the 6-dof electric motion platform system designed for the helicopter simulator satisfying the class of the CASA(Civil Aviation Safety Authority) level 2 is presented. From the kinematic, dynamic and structural analyses for motion base and electrical actuator systems, we show the feasibility of the developed motion platform system by producing the acceptable results of the test and evaluation according to the requirements specified in the CASA level 2. Furthermore through this development we suggest newly the adaptability of the electrical actuator system up to 10 ton class motion platform system, whose usage will be broaden rapidly, substituting with the advantage over the conventional hydraulic system.

Modelling and Control of An Electromechanical Steering System in Full Vehicle Models

In the automotive industry, electrical and electromechanical components and systems become more and more important. In comparison with commonly used mechanical and hydraulic systems they offer a large number of advantages with respect to efficiency and flexibility, for example. Therefore, conventional hydraulic steering systems are increasingly being replaced with electromechanical ones. Currently, different concepts of electromechanical steering systems are being developed. In this work an electromechanical steering system with double pinions is modelled based on a uniform theory for discrete electromechanical systems. This steering system is implemented into a multi-body full vehicle model and a control scheme has been developed. Subsequently, the performance of the whole electromechanical system, and especially the behaviour of the controller, has been tested with different handling manoeuvres.

Force control of hybrid actuator using learning vector quantization neural network

Hydraulic actuators are important in modern industry due to high power, fast response, and high stiffness. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Therefore, hybrid actuator has a wide range of application fields such as plastic injection-molding and metal forming technology, where force or pressure control is the most important technology. In this paper, the solution for force control of hybrid system is presented. However, some limitations still exist such as deterioration of the performance of transient response due to the variable environment stiffness. Therefore, intelligent switching control using Learning Vector Quantization Neural Network (LVQNN) is newly proposed in this paper in order to overcome these limitations. Experiments are carried out to evaluate the effectiveness of the proposed algorithm with large variation of stiffness of external environment. In addition, it is understood that the new system has energy saving effect even though it has almost the same response as that of valve controlled system.

Integrated control of clamping force and energy-saving in hydraulic injection moulding machines using decoupling fuzzy sliding-mode control

The objective of this research is to implement a novel parallel control of clamping force and energy-saving in hydraulic injection moulding machines (HIMMs) in order to simultaneously achieve accurate force control response and high energy efficiency. In order to verify the feasibility of the integrated control system and compare energy-saving effects, the clamping force control of HIMMs can be integrated with two different energy-saving control systems or integrated with a conventional hydraulic system without energy-saving control. The overall control system is a coupled two-input two-output system. Therefore, a decoupling fuzzy sliding-mode control (DFSMC) strategy, which can reduce the fuzzy rule numbers and counteract the coupling effects, is developed for the integrated control of HIMMs. The experimental results show the outstanding performance of the parallel control in HIMMs with DFSMC .