Cavitations inside hydraulic valves were investigated by using high-speed camera technology and noise spectrum analyzing method. The bubble flow's morphological and flowing characteristics were converted into numerical information by the employment of image process, which made the two-phase flow easily identifiable. Based on this, cavitation's distribution and shape characteristics were revealed. Combined with cavitation noise spectrum analyzing, it was found that the shedding process of cavitation had similar high frequency properties with cavitation noise spectrums. Typical noise curves of cavitations were obtained, and the second peak levels were found in low cavitation number conditions. In addition, it assumed that, the shedding frequencies played a good reflection to cavitation noise while using cavitation numbers as the only variable.

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A 2D servo valve designed with zero-overlap is proposed. First, the pilot leakage of the 2D servo valve with a zero-overlap of pilot stage is analyzed theoretically. Based on the analysis to the flow field of the clearance between two parallel plates, the overall pilot leakage is calculated through integration. Secondly, the mathematical model of the axial motion of the spool in respect to rotary motion is established and the dynamic response of 2D servo valve is investigated by simulation. Finally, to validate the analysis, the prototype of a 2D valve with flow capacity of 300L/min (at 7Mpa) is fabricated and the pilot leakage and the actual step response are measured. The results of the experimentshow that the pilot leakage is about 0.6L/min at 2 I Mpa and the response time for the step input is 7ms. It is concluded from both theoretic analysis and simulation that the 2D servo valve with a zero-overlap of pilot stage has a fairly fast dynamic response, and its pilot leakage is very small, less than 0.2%.

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The E/H servo cartridge valve is adopted to control the system of 20MN Forging Hydraulic Press. Its characteristics, such as short response time, high control accuracy and so on, are extremely fit for forging hydraulic press. As a result the high forging times and accuracy can be achieved. A new saving-energy fast forging press using accumulator is presented for the problem of power waste during forging process. The model of proportional cartridge and accumulator are found, then the mathematical model of the whole fast forging circuit is found and simulated, the results show that it performs perfect for the fast forging press by using accumulator. Finally, base on the fast forging press test with accumulator, the model validity and feasibility of this fast forging circuit are validated.

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A basic hydrostatic transmission consists of a variable hydraulic pump and variable hydraulic motor. The most popular strategy is to control the units in sequence. From standstill up to a speed limit set by the maximum pump displacement, the output speed is controlled by the pump. Further increase of the output speed is achieved by decreasing the motor displacement. This way to control of HST is not best thinking of total efficiency. Efficiency of the hydraulic pump and the hydraulic motor are function of pressure, rotating speed and control angle. If it is possible to control independently the hydraulic motor and the hydraulic pump, it can be optimized total efficiency for every operating point (torque and rotating speed of the hydraulic motor). In this study control settings of the hydraulic pump and the hydraulic motor are optimized for each operating point so that the total efficiency should be as good as possible. These optimized efficiencies are compared to efficiencies from traditional control. The entire operating band was studied (rotating speed and torque of the motor) using simulation. Exactly verified simulation models of the HST were used. The base of simulation models was measured data from earlier studies. The results show that efficiency can be improved when the load is low. Power loss decreased maximum about 1.5kW.

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This paper describes a numerical procedure for the analysis and the optimization of external gear pumps. The Fluid Power group of the University of Parma has implemented a numerical code for the simulation of external gear pumps and motors; the code is named HYGESim and it is based on a lumped parameter approach implemented in AMESim, writing proper submodels in C language. This work is focused on the optimization of the pump design with particular reference to the geometry of the recesses machined on the bushings. The procedure is based on a path search method known as Steepest Descent and optimizes the considered parameters starting from a design taken as initial reference. The objective functions defined for the optimization permit to account for the volumetric efficiency, the delivery pressure ripple, the maximum and minimum pressure peaks during the meshing process. An optimal design of the recesses has been proposed and a prototype of a pump, equipped with the proposed geometry of bearing blocks, was tested. Measured data and the comparisons with the experimental results obtained for the stock pump taken as reference are presented in the paper, confirming the potentials of the developed optimization methodology.

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In this study, a new electro-magnetic proportional actuator composed of an armature and stator with multi convex teeth to control oil hydraulic valves was designed and examined. Each of the convex teeth forms a magnetic pole, and when multiple magnetic poles produce a force simultaneously, a large thrust force is generated in the actuator. The shape of the teeth was varied and influence on the thrust force was examined. As a result, the interval between the convex teeth could be reduced. A 10-step pole type actuator was designed, and its thrust force was estimated. When the dimensions of this actuator are 52mm height, 68mm width, by 102mm length, its thrust force is constant within 2mm of the armature stroke, producing about 300N at an electric power consumption of 15W, and it generates the thrust force in proportion to the coil current. The thrust force of this actuator is about 2.5 times as large as that of conventional proportional solenoids and linear motors of the same installation area to the valve body, length and power consumption.

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Air entrainment in working fluids has great detrimental effects on function and lifetime of the fluid power components and systems. It is important to eliminate the air bubbles from the working oil to preserve oil quality, system performance, and to avoid possible damage of the components. In view point of environmental compatibility, energy saving, cost saving, and high efficiency, one trend in fluid power systems is for them to be designed in a more compact fashion, requiring less fluid in the reservoir and long lifetime of the working oil. A new device using swirl flow for bubble elimination capable of eliminating bubbles and of decreasing dissolved gases has been developed. In this paper we focus on the technical issue for the air bubbles and aging behavior of the hydraulic oil. In order to investigate the effectiveness of the developed bubble elimination device, changes of oil degradation were experimentally measured on our laboratory test bench under the pump operating conditions during 456 hours of continuous running. Oil specimens are sampled and change of a total acid number and a color is investigated as a function of the working time.

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The new generation algorithm of time domain drive signals is presented to reduce the loop time in MIMO (multi input multi output) random vibration control system. The Parks-McClellan method is used to design the FIR (finite impulse response) filter. And then the drive signals in time domain is generated by filtering a series of independent white noise with the designed filter. For avoiding the time domain randomization process in the conventional frequency-to-time transformation, the new method is favorable to improve the real-time property of the control system. Two tests are run in one 6 DOF (degree of freedom) hydraulic shaker with the conventional algorithm and the improved algorithm differently. The results demonstrate the effectiveness of the improved algorithm.

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A variable displacement axial piston pump with Pressure compensator and Load Sensing control is coupled to a diesel engine. The pump is in an open circuit topology for load control in a typical excavator, skid-steer or front loader circuit. The active torque generated by the engine is subject to overloads, due to uncontrolled priority and sum of torque requests from hydrostatic transmission, implements and upper-structure control. In order to avoid engine overload a third 2 ways proportional valve is added to the control circuit. The valve controls the delivery pressure on the load sensing valve port, and the pressure is managed by an electronic system. This circuit architecture allow the designer to use the valve as a variable load sensing system, modifying the load sensing differential pressure depending on working conditions. The control must be in real time and a feed forward control based on the valve characteristic map is useful and helpful but a feedback control is needed to correct the steady state error; a PID and a Sliding mode are superimposed, in order to react to high dynamic transient. The controls runs properly on the bench and the advantages are: more engine efficiency and continuously working capacity, adapting load sensing pressure a more efficient use of power is possible.

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In this study, the control performance of a hydraulic servo system with a feedback linearization compensator is investigated. The focus of this study is set on the quantitative investigation of the effects (sensitivities) of disturbances and system parameters' variation on control performances of the hydraulic control system. Finally, verifies the efficacy of a disturbance observer to overcome the control performances deterioration due to system parameters' variations, disturbances in the control system.

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The various hydraulic components for excavator have been developed in KYB Corporation. In early stage of the product development, we usually use calculation of static characteristics, but we do not use calculation of dynamic characteristics for the system. The dynamic characteristics of the system are tuned using actual system in middle stage of the product development. Therefore it is often necessary to extend the product development time. In order to decrease the development time, we developed a simulation model of excavator system for dynamic characteristics calculation. This paper shows case studies of the system simulation for hydraulic excavator applied to the digging-turning-loading cycle analysis.

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Up to now, several types of hybrid systems have been developed to deduce energy consumption. Switching type closed loop constant pressure system (SCL-CPS) was proposed as one of feasible hybrid systems. SCL-CPS also uses flywheel, hydraulic accumulator and hydraulic power transmission as a traditional CPS but it has two alternatively high pressure lines. At a same time, one is used as the high pressure line and the other is the low one. Switching between them to overcome large hydraulic shock and noise considered as serious problems in traditional CPS. In this paper, energy saving potential of system is evaluated by considering effect of component efficiencies in system. Recovery efficiency during deceleration the wheel is estimated by simulation. The results indicate that proper determination of recovery time and operating pressure improves significantly energy recovery potential of the system.

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Displacement-controlled actuation offers energy savings by eliminating the metering losses associated with hydraulic valves and allowing energy recovery. In a closed-circuit configuration, four-quadrant pump operation can be achieved. This paper considers displacement-controlled boom lift cylinders on a skid-steer loader. Undesirable pump mode oscillation is observed while rapidly lowering small loads. Avoiding this oscillation requires actuator pressure control, which cannot be directly achieved due to insufficient pump dynamic response. The authors propose a predictive observer to provide sufficient lead time for feedforward control of actuator pressure. Design and analysis are presented for a discrete time linear observer which predicts future system states by delaying the input signal. Successful state prediction is demonstrated through simulation and experiment.

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The most important role of a hydraulic fluid is transmission of power among various roles. A bulk modulus of the fluid is crucial for hydraulic systems, particularly for high-pressure hydraulics. In theory, compression energy losses are in diverse proportional to the effective bulk modulus of the fluid, and response speed and stability depend directly on the square root of it. Conventional mineral oils have pretty low bulk modulus, compared to water-based hydraulic fluid. On the other hand, the water-based fluids are disadvantageous in lubricity and evaporation. Under the circumstances, we've searched for available oily high bulk modulus fluid, and found organic compounds with water-level bulk modulus.

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This paper presents experimental and numerical simulation results of the electric and flow fields in a charge injection type of electrostatic oil filter. A previous work has shown that flow is generated from the tips of the projections of the emitter electrode towards the smooth electrodes because of ion drag phenomenon and that the flow may detach part of the contaminant particles captured on the smooth electrodes and may be the principal cause of the saturation of the fi ltration speed at higher applied voltages and oil temperatures. In order to minimize the bad influence of the ion drag fl ow on the filter performance, it is important to be able to predict the flow in filters of various configurations by numerical simulation. Experimental results of the flow field are compared to numerical simulation results. In addition, electric potential distribution is measured and is compared between experiment and simulation. It is shown that the magnitude of the ion drag flow is increased with increasing applied voltage, is decreased with decreasing electrode spacing and is larger for negative charge injection than for positive charge injection. Similar results can be obtained by numerical simulations but the improvement of simulation accuracy is necessary.

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Temperatures of a swash plate, cylinder block, and a valve plate of swash-plate type axial piston pumps with a rotating cylinder block and a rotating swash plate were measured. Thermocouples were embedded underneath these parts. Hydraulic mineral oils with ISO VG22, 32, 46, and 68 and a water-glycol type hydraulic fluid with VG32 were used as test fluids. The maximum discharge pressure was 20 MPa and the maximum rotational speed was 28.3 rps. The inlet oil temperatures were specified as 293-313 K. At the atmospheric pressure to the maximum discharge pressure, the temperatures, flow rates, and the torque were measured. Results support the following conclusions: i) as the discharge pressure increased, the temperatures of the swash plate, cylinder block, and the valve plate increased in almost direct relation; ii) the cylinder block temperature at the bottom dead center of the pistons increased markedly; iii) the temperature increases using the water-glycol fluid were noticeably smaller than the rises using the mineral oils; and iv) the temperature rises became large for higher fluid viscosity and lower inlet oil temperature.

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In a joint research project BMW and IFAS analyzed two well known hydraulic phenomena occurring in power steering systems, in order to reduce noises, that are caused by these phenomena.
The research project was subdivided into three tasks. The first task incorporated the analysis of the power steering system of a BMW 5 series passenger car. During this analysis an impulsive pressure pulsation phenomenon known as rattling as well as a periodic pressure oscillation called shuddering were measured. Both phenomena result in distracting noises within the passenger cabin and occur during certain different driving manoeuvres.
The second task included the construction of two test benches to reproduce rattling and shuddering independent from the car. A comparison of the measured data obtained by driving tests with the collected data from the test benches verified their functionality and accuracy. Another advantage of the test rig is that it provides easy access to the power steering system's components. Modifications can therefore be carried out in a short amount of time.
Finally an intelligent valve was designed and tested at the two test benches. The valve can detect the two different hydraulic phenomena without the need of sensor signals and without causing high pressure drops. In case of rattling the valve softens the return line of the power steering system and in case of shuddering the return line is hardened. A softer return line reduces pressure pulsations while a harder return line is insensitive to periodic pressure oscillations.
This paper describes a solution for two different hydraulic phenomena (rattling and shuddering) occurring in power steering systems. The solution is the integration of an intelligent energy efficient valve into the power steering system's return line, which changes the stiffness of the return line depending on the occurring phenomenon without affecting the sensation of the steering. The functionality of the presented valve is proven by means of the test results obtained from two test rigs designed to reproduce the described phenomena.

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A quarter wavelength side branch resonator has been widely used as a reactive type silencer to attenuate pressure pulsation in hydraulic circuit. The structure of this conventional silencer is very simple and therefore it is a useful device in terms of cost efficiency. However, it is also known as a rather narrow frequency banded resonator that only attenuates the odd order harmonics of the pressure pulsation.
In this study, the attenuation performance of side branch resonator in the hydraulic line is examined numerically by changing the parameters such as the insertion location of side branch and the length of connecting pipe between the side branch and termination load of circuits. The level of attenuation is accessed by insertion loss which is defined as the ratio of overall amplitude harmonics of pressure pulsation with and without the side branch. The paper describes the fundamental principle of side branch and the mathematical model of insertion losscharacteristics. Some calculation results for the insertion loss characteristics are carried out to show the influence of even order harmonics and the interaction of pump, termination load and all pulsation propagation characteristics of the circuit including side branch.

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Autonomous functions are a common research topic in robotics. However, the robots typically have limited operating conditions and they can only handle relatively small loads. Many autonomous control concepts are applicable to actual construction machinery. The benefits would be considerable regarding efficiency, safety, and operator comfort. The research projects of this field have often led to systems with cost and complexity too high for most applications. This paper presents an implementation of a cost-effective distributed control system that is retrofitted to a small hydraulic excavator. The system can be used to perform simple operator assisting functions but also to develop autonomous excavation.
The hardware of the system consists of cost-effective joint angle sensors and a flexible microcontroller unit. Control schemes that produce autonomous functions are discussed and tested with the excavator. These include position controllers for conventional mobile proportional hydraulics. The aim is to find computationally simple but flexible algorithms for autonomous excavation. The results of the preliminary tests are presented. Future improvements are discussed.

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Variable valve lift (VVL) system for automotive engines is one of the ke technologies to attain improvement of fuel economy and power output and reduction of emission. This paper presents a highly reliable VVL mechanism controlled by a hydraulic 3-step rotary actuator. 3-step VVL with high-, middle- and low-valve lift, is realized by the pivot shifting of an intermediate cam placed between a camshaft and valve tappet. The hydraulic actuator with no electric device is installed in a cylinder head and its rotary positioning generates 3-step rotation of a specially-designed sprag cam. The actuator can work in low supply pressure of 0.1MPa and control 3-step angles within the interval in which the valve is at rest during camshaft rotation. This paper describes the analytical simulation model of the VVL system, and the experimental evaluation for the developed VVL mechanism and hydraulic 3-step rotary actuator.

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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.

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Hydraulic excavators are the representative of field robot and have been used in various fields of construction. Since the excavator operates in the hazardous working circumstance, operators of excavator exposed in harmful environment. Therefore, hydraulic excavator automation and remote control system has been investigated to protect from the hazardous working environment. Remote control system of hydraulic excavator needs various equipments. In this paper, the method to construct the remote control system is proposed. The remote control system is consisted of a manual and auto mode. Manual mode controls a hydraulic cylinder as open loop control. and auto mode controls the end effecter of excavator using tracking control system. The efficiency of remote control system was evaluated through the field test.

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The frequency bandwidth of the electrohydraulic vibrator conventionally constructed by a servo valve and a hydraulic cylinder or a motor is to a large extent limited to fairly narrow range by the dynamic response capability of the servo valve. A 2D electrohydraulic valve is thus developed to enhance the working frequency range to a new high level. In this 2D valve, the continuous rotary motion of the spool is used to create alternated variation of the valve port areas, while the linear motion of the spool is to control the peak value of the valve port areas. The frequency excited by 2D valve is proportional to the rotary speed of the spool and thus the high-frequency can easily be achieved by increasing the rotary speed of the spool well lubricated in hydraulic oil. Experiments have been carried out to the vibrator loaded by an elastic force coming from the deformation of a frame work and the wave forms of the cylinder piston was measured. It is demonstrated that the ascent and descent slopes of the wave form show some inconsistency which alleviates with the reduction of valve linear opening. The phenomenon is explained to be caused by the changing direction of the elastic force. Nevertheless, the wave from is close to a sinusoidal one. It is concluded the development of the 2D valve does point out an access to the high-frequency excitation of the hydraulic vibration.

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In this paper, base on the operating principle of water press pull-up inlet valve, we model the mathematical model of inlet-valve and made a simulation on computer.By the method of simulation, get the curve of control pressure (up cavity pressure) and opening force in process of pull-up inlet valve opening.Changing the structural parameter of inlet valve and working pressure of water press, gain the relationship between pull-up inlet valve opening force changing tendency and the structural parameter of inlet valve and working pressure.

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This study concerns a new rotary type water hydraulic pressure intensifier. The object of this paper is to introduce the structure and the working principle of the pressure intensifier, and to present the fundamental characteristics by experimental results. The basic structure is similar to that of a water hydraulic planetary gear motor. Its main part consists of a stator, a rotor, nine planetary gears and two side plates. The inside of the stator is formed by a curve with 5 lobes and the outside of the rotor is formed by a curve with 4 lobes. Their curved surfaces have teeth like a gear. Nine displacement chambers are formed by the stator, rotor, planetary gears and side plates, and the each chamber's volume varies periodically when the rotor rotates. A side plate has 5 inlet distribute holes and 5 outlet distribute holes alternately located on its surface. Each displacement chamber connects to an inlet distribute hole during the volume is increasing, and it connects to an outlet distribute hole during the volume is decreasing. Now, one of the outlet distribute holes is separated from the other 4, the intensified higher pressure water is discharged from the separated distribute hole. It is found that the critical intensification ratio is about 2.5 by experimental results with a prototype.

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Natural gas is being hailed as alternative energy sources for a petroleum, because it is almost no emissions of pollutants in the environment. Use of equipment for liquified natural gas, along with increased demand for natural gas is also growing. Cryogenic ball valve is used to control the liquified natural gas which temperature is-196°C, supplied pressure is 168kg/cm². To acquire the safety along with durability of cryogenic ball valve, we should consider the structural mechanics such as stress, deformation and dynamic vibration characteristics and identify those important aspects in the stage of preliminary design engineering. For the cryogenic ball valve, the assurance of structural integrity and operability are essential to meet not only normal, abnormal loading conditions but also functionality during a seismic event. In this study, analytical approach and results using finite element analysis and computational method are herein presented to evaluate the aspects of structural integrity along with operability of cryogenic ball valve. Moreover, we have done the optimal design through special processing and heat treatment and so on. Finally, we designed the high pressure cryogenic ball valve that accomplishes zero leakage.

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In this paper a Ultra-high pressure (UHP) water jetting removal rust cleanout auto-robot is designed, which works with the high-pressure pump units with pressure 250MPa and the vacuum residue displaced system. It is the implement machine for the removal rust system. Three key technique questions are solved in the cleaning automation process. These are wall attaching, wall moving and wall cleaning technique. Experiments showed that the robot both remove rust efficiently and move agility.

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Aerostatic spherical bearings can operate in places which requiring three degrees of freedom in rotation with a minimum of frictional drag. It is one of the key components of aerocraft motion simulator. With the development of large-scale simulation equipment, the requirement of aerostatic bearing with heavy-duty is widely and imminent. Compared with aerostatic spherical bearing with multi-orifices compensation, the bearing with inherent compensation and integrated socket is newly developed, and it has admirable stability in large scale of supply pressure. A new type of running-in aerostatic spherical bearing with inherent compensation and large wrap angle is designed and optimized. At the same time, the pressure and velocity field distributions in region of gas film are obtained by CFD software. Experimental results are proved that the bearing capacity of the new aerostatic spherical bearing is far improved than conventional one.

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We considered the so-called Fanno flow as a model of flow through pneumatic pipe lines with a constant diameter. The flow is one dimensional, steady and adiabatic. The friction coefficient is constant. We succeeded to express the critical pressure ratio of the flow which is choking at the exit of the pipe line by three parameters, the pipe diameter, the pipe length and the friction coefficient. We compared the theoretically estimated critical pressure ratio to the experimental results. The results showed the good agreements except the case of the short pipe lines less than 10cm. It was confirmed that our method of determination of the ratio was very useful for the flow calculation using ISO choke equation. With these studies we established the simulation program for the Fanno flow on MATLAB_Simulink and show that the program was easily applied to connected pipelines in series.

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Based on the analysis of principle and structure of the gas booster, this paper studied on its charging process from low-pressure gas bottle to high-pressure one, considered the effect of some facts, including the changing of inlet and outlet pressure, clearance space, friction, according to the principle of kinematics, gas dynamics and thermodynamics, established the mathematical and dynamics model of a gas booster system, which includes pressure differential equation of each chamber, flow rate equation, as well as the temperature equation and piston acceleration equation. The system is simulated with M-File of MATLAB software, and we got the pressure change curves, flow characteristic curve and time of charging gas, and the experimental data proved the correctness of simulation result, and provide theoretical basis for model selection and overall design.

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The Pneumatic Center in Huazhong University of Science and Technology (HUST) is one of the most active research center in fluid power transmission and control in China. The main fields of Pneumatic Center in HUST are component development and control technology of fluid power. Hydraulics research is the most important part of fluid power in the Pneumatic Center in HUST. Based on several decades of the research on the hydraulics in HUST, the further research and new application in this field are made, include underwater motion platform, automatic buoyancy regulation technology and new type hydraulic valve, etc.. From 1996, the Pneumatic Center in HUST focuses on the combination of electronics, computer technology and pneumatics, and the research achievement play a very important role in some state key engineering projects successively. The pneumatic research and applications have been developed, such as the gas temperature control technology, pressure and vacuum servo control technology, leak-testing technology, pneumatic muscle platform and the high pressure pneumatic valve, etc.. In this paper the main research and application of hydraulics and pneumatic in Pneumatic Center in HUST are introduced. Also some practical examples research projects and subjects in above fields are presented.

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An importance of wearable device in the field of medical treatment has been strongly recognized. Also, the development of the power assisted system has been done to support the nursing care work for the elderly. The purpose of our study is to develop a wearable flexible displacement sensor which can measure the movement of human body by mounting on the skin surface. The tested sensor consists of two fixed electrodes, a slide electrode and a nylon string coated with carbon (NSCC). It works as a flexible potentiometer by sliding the slide electrode along NSCC while keeping the electrical contact. In order to keep a stable electrical contact even if NSCC bends flexibly, the slider is consisted of a brass cylinder filled with carbon black powder. In our previous study, we confirmed that the sensor worked well by carrying out the position control of a McKibben artificial muscle.
In this paper, we proposed and tested a skin displacement sensor using the flexible displacement sensor that can measure the bending angle of the human arm without measuring the joint angle directly. As a result, we confirmed that we can know the human motion indirectly using the tested sensor. We apply the proposed sensor to the control of the power assisted system by using a pneumatic rubber artificial muscle.

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A sound operated directional control valve (SODC-Valve) is proposed which opens and closes in response to the sound of a specific frequency propagated inside the gas supply tube and therefore needs no electric wiring to convey the control signals. By using multi-frequency sound, several valves can be controlled simultaneously and resultantly the pneumatic multi-degree wearable system can be constructed compactly. Firstly, the sound-gas pressure converter is proposed and improved so that self-excited vibration can be suppressed. Secondly, the basic characteristic of the sound-gas pressure converter is investigated to show that the back pressure is different depending on whether the sound of specific frequency is added or not. Furthermore, a pilot valve is developed. Because the pilot pressure change of the pilot valve developed is only 20kPa, a main valve is proposed and developed. Finally, a pneumatic multi-degree-of-freedom wearable power-assist system is constructed by using a Dry Ice Power Cell as the portable gas supply, wearable actuators developed in the previous study, and two sound operated directional control valves developed. Experimental results show that the sound operated directional control valve is feasible and practical in the pneumatic multi-degree-of-freedom wearable system.

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The purpose of this research is simplifying and downsizing of pneumatic system consisting of many pneumatic actuators. For this purpose a new method of multiplex pneumatic transmission for multi-pneumatic servo system is proposed. The pneumatic valve for this system has a simple structure consisting of two vibrators supported by springs. The working principle of the valve is based on vibrator resonance caused by multiplex pneumatic vibration in air supply line and this makes the valve work as an ON/OFF valve without electric wire or independent pneumatic tubes. Valve control needs superimposed only an air supply tube for its independent control, making this pneumatic system suitable for the system having many degrees of freedom.
Two prototype valves have been developed to confirm the basic function and adapted to the pneumatic system consisting of two pneumatic cylinders. The prototype valve has been designed based on the result of a dynamic simulation and it was confirmed by basic experiments. In the experiment, the independent control for two pneumatic cylinders with prototype valves has been successfully realized.

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This paper deals with a technique of repeated positioning of a long stroke pneumatic cylinder. This system is suitable for a long stroke cylinder when the desired intermediate stop positions are fixed and the same operation may be repeated as in automatic production lines. The basic control algorism is a sequential on-off action of the air valves. For one desired position, three proximity switches are installed to detect the slider passing as well as its velocity. The main experimental result with a rod-less cylinder of 1000 mm stroke is that the control accuracy converged quickly within +/-0.2mm by a learning function.

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This paper presents pressure control method using the electro-pneumatic regulator with two multilayered PZT valves. An electro-pneumatic regulator is a type of pressure control valve that is a combination of a poppet valve for main pressure control, two multilayered PZT valves for pilot pressure control, a microprocessor with a feedback controller and a pressure sensor. The benefits of bender type PZT actuator are faster response times, low energy consumption, and the ability to be used in hazardous environments and field bus systems. Solenoid actuator for electro-pneumatic regulator is widely used but this actuator has a high power consumption characteristics. So PZT actuator is required for the energy saving.
In this study, a multilayered bender type PZT actuator of 27.0mm (L) ×9.0mm (W) ×0.8 (mm) with a constant of 220e-12m/V and 20 sheets of PZT thin film was fabricated and experimented. The experiments for On-Off control and PID-PWM control of the electro-pneumatic regulator were operated under the input condition of 0.5 MPa. From the experiments, the performance characteristics of the fabricated electro-pneumatic regulator were evaluated. A new control method for precise proportional pressure control using the electro-pneumatic regulator with two PZT valves was suggested. Using this suggested model, all possible operating conditions were analyzed.

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In this paper, a new proportional pneumatic floating vacuum pad is developed and constructed. There are two features concerning this new vacuum pad. The first one is the introduced proportional solenoid, which enables the continuously variable control of the suction force output. In addition, the floating mechanism design between the vacuum pad and work-piece is the second feature, which is more preferable in real industries because it can protect the surface of the work-piece from scratching or other damages. Moreover, two control schemes are also proposed in this paper. The first one is the gap control. A pre-set constant gap is input to the controller as the command input which further drives the proportional solenoid to maintain a steady-state gap between the vacuum pad and work-piece. In the second control approach, the gap between the vacuum pad and work-piece is kept as large as possible to minimize the energy consumption. Both control schemes are successfully implemented in this study. It is expected that the newly developed prototype with two different control schemes may find some real applications in the future.

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Pneumatic servo systems are applied in several industrial applications and have also been studied extensively for the purposes of compensating the nonlinearity of pneumatic servo systems and improving the controllability with robust control. In their control system design, the transfer function of a pneumatic servo system has been a third-order time lag system, based on the assumption that servo valve dynamics is negligible because it is sufficiently faster than cylinder dynamics. However, the characteristic of a servo valve greatly influences the dynamic characteristic of the pneumatic servo and should be taken into account in the control system design. In this research, a new method of control system design, which deals with the pneumatic servo system as a fifth-order time lag system including a second-order time lag system of a servo valve, has been proposed. The experiment shows that the proposed method is effective. As a result, we can decide all of the control parameters including the proportional gain without trial and error, The obtained proportional gain can be larger, so that the performance of a pneumatic servo has been improved.

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Currently used jet vacuum ejector has a defect of high air consumption due to its requirement of continuous air supply. Focusing on this problem, a new type of piston vacuum generator (PVG for short) has been researched. The PVG has two pairs of pistons. One is for driving and another is for vacuum generating. Besides the maximum vacuum value, the vacuum response time and air consumption are the most concerning performances. Special structural design is made so as to meet all the requirements, in which the unequal diameters of pistons, using directional control valves instead of the check valves and stepped flow rate control scheme are proposed and realized. Experimental results have shown that for the prototype of piston vacuum generator its maximum vacuum is about 93kPa, the response time is about 3.7s and the air consumption is reduced by about 71.3% in time interval of 60s compared to the same level of vacuum ejector.

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There are many methods to improve actuator efficiency in pneumatic systems. In this research, the authors remodeled rotary valve of radial piston type air motor. During forward rotation, increasing Cut-off ratio of rotary valve which controls supply and exhaust timing can increase expansion process in this motor. As a result, air consumption was reduced, torque was increased and efficiency that we define as the ratio of air consumption to torque was improved. And the authors clarified the existence of an optimum angle in Cut-off ratio.
Considering practical utilizations, performance of this motor is demanded for the same forward rotation as backward rotation. But actually, increasing Cut-off ratio increases compression process andderives efficiency worse.
So the authors have proposed to remodel the casing of this motor in addition to increasing Cut-off ratio. This remodeling makes this motor the same performance forward rotation as backward rotation, but clearance volume expands. So the rate of increasing efficiency under this condition is less than under only remodeling Cut-off ratio. But we directed to possibility of improving efficiency.

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This paper deals with torque reduction control for an electro-pneumatic hybrid vertical positioning system composed of a servomotor a pneumatic and a mechanical driving sub-system. The servomotor, coupled with a ball screw connected to the load by nut, enables to position a load vertically. The servomotor with small capacity, as well as energy saving, is required for cost down. To realize its small capacity, it is important to reduce the torque of the servomotor in moving the load. In a pneumatic system, a pressure controller generates control signals for the supplied pressure equivalent to the gravitational force of the mass of the load so as to support and move the load smoothly. The torque reduction for the small: capacity servomotor needs adequate control pressure supplied to a cylinder. In the present study, a mathematical model of this system has been developed by comparing calculation data with experimental results. The controller designed by this model has succeeded in the torque reduction of the servomotor.

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The technology of on-off solenoid valves is now considered as a core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for medical applications. And on-off solenoid valves, which operate by compressed air, are characterized by high speed response, great repeatability and that the pressure on the cross sectional area of poppet is kept constant regardless of the fluctuation of the pressure exerted on the ports. The primary objective of this study is to compare the optimally designed solenoid valve with the actually produced one and to design a power saving circuit which can highly improve the efficiency by providing optimal current according to mechanical load. The power saving circuit can be adopted into the 0.35Watt micro valve which has been developed through this study and lower the power consumption of the valve to 0.1 Watt. The absorbing force at 0.3mm stroke, the initial stroke of Plunger and Core, is very large. But the absorbing force at 0mm stroke when Plunger and Core are tightly stuck to each other is several newtons lower than that at the initial stroke, the valve still performs stable and flawless though. It means that with lower current consumption, it still performs stable. Based on that, we've designed the power saving circuit.

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With the development of virtual reality technology, portable force feedback dataglove plays an important role in virtual assembly and telepresence system. Angle measurement is a basic function of force feedback dataglove, in which the measurement accuracy and calibration are often considered as unsolved problems in previous research. For solving these problems, some work is conducted with an exoskeleton force feedback dataglove using pneumatic artificial muscles as actuators. First, a measurement model of the finger flexion angle based on the theory of four-bar-linkage motion stabilization is built. The effect of structure parameter of linkage on the angle measurement and force feedback is analyzed, which has provided a help for the choice of linkage parameters and improved the accuracy of measuring angle. Then a new calibration method, which is called the “four-posture calibration” based on standard block and genetic algorithm, is proposed. Taking index finger as an example, the process of calibration is introduced in detail. Experiment has shown that with the new calibration method more accurate results can be obtained than that in previous work.

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The utilization of mobile rescue robots in dynamic environments decreases the risk to emergency personnel in the field. Recent efforts to improve rescue robot design by using new fluid-power technology provide opportunities of studying the changes in metrics of human-robot interaction (HRI), such as trust. Trust is one of the most critical factors in urban search and rescue missions because it can impact the decisions human make in uncertain conditions. This research is to develop an instrument that can be used to measure trust in human-robotic interaction, which will allow us to collect data for building a quantitative model of trust in HRI. As the first step in this effort, a pilot study was conducted to determine the validity of an instrument to measure the appropriate dimensions of trust in this new human-robot system.

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The purpose of this study is to develop a wearable master-slave lower limb training device for a trainer and a trainee. The developed device is constructed with McKibben type rubber artificial muscles and an appliance, a torque sensor. In addition, to prevent applying an excessive torque to the trainee, a reaction torque from the trainee can be transmitted to the trainer by a bilateral type master-slave control system. In this paper, the structure of the developed device is discussed, and then the validity of the proposed device is evaluated from the experiments assumed a training.

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In recent years, accidents of bone fracture with elderly people increase because of tendency to fall by a little step in a house. As one of this cause, it is considered that a center of gravity position with foot parts of elderly people is changed. Therefore, in order to solve this problem, we propose a new type of insole with high performance by making use of sponge-core-soft rubber actuator (SCSRA). In this study, we apply the actuator to an insole in order to support walking motion. That is to say, a new type of insole to distinguish the foot motion (Pitch or Roll motion) is proposed. To clear the performance of the insole, we develop a test device that is constructed with rotary actuators and a cylinder. In this paper, the mechanism of the proposed insole is explained and basic performances of the proposed mechanism are clarified through some experimental results.

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The purpose of this study was to develop a pneumatic gait training system which was consisted by Mckibben type actuators to achieve the normal gait patterns of lower limb joint angular displacements. These actuators were arranged as human musculoskeletal system; mono- and bi-articular muscles. The system provided a proportional directional control valve which controlled antagonistic actuators, and this system had PID controller and joint angular displacement feedback circuit. In the results, the output of the knee joint movement pattern had well validation for the input signal which was recorded from natural treadmill walking in healthy subjects. This system made the orthosis reproduce like the human natural walking. In conclusion, we structured a fundamental bi-articular muscle type of the gait training system using Mckibben type actuators.

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The common ways used to find leak include traditional bubbling test, ultrasonic positioning and helium mass-spectrometer detection, etc. However, each of them has deficiencies of varying degrees, especially low-efficiency in bubbling and mass spectrometry means and poor anti-jamming capability in ultrasonic means. In order to search a better approach to do this job, a new method is introduced in this paper, which is based on infrared thermography. In the experiment, test vessel is firstly aerated with absolute pressure of 0.6-0.7 Mpa and then the temperature field surround the vessel is monitored and acquired by an IR camera. On account of leakiness, compressed air expanses from the leak hole to ambient and heat-absorption effect has taken place around it on the basis of Joule-Thomson Effect, so the temperature difference between the leak area and normal area will be reflected in the thermal images. Moreover, Freon cooler is also set in the pneumatic circuit for the sake of enhancing the phenomenon. During the test, several frames of thermal images in time sequence are transferred to the computer for pre-processing and fusion operating by the use of local entropy difference algorithm. From results, it is shown that the method achieves a good resolution and sensitivity in the application of air-leakage detection and localization. Some modeling and simulating work by finite element analysis is also carried out in this paper.

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Plane externally pressurized thrust gas bearings for high speed spindles are considered. The behavior of the rotor-bearing system is studied both numerically and experimentally. A numerical model based on Reynolds equation is used to simulate the static and dynamic behavior of the system. Flow rate equation through inlet orifices is coupled with Reynolds equation. The flow rate is calculated by considering an experimentally determined discharge coefficient, that is function of holes diameter and local clearance. To increase stiffness are studied thrust bearings presenting a circumferential groove situated at the same radius of the supply holes. The influence of the groove on stiffness and stability is discussed. Simulations are made to evaluate the influence of supply holes diameter and of axial clearance on bearing characteristics.
Two thrust bearings are studied experimentally. They are composed by a symmetric couple of disks facing the rotor fl ange. The internal and external diameters of the disks are 52mm and 110mm and equipped with 8 holes of diameter 0.35mm on a circumference of diameter 65mm. A thrust bearing present a rectangular section circumferential groove, located at the same radius of the orifices, of width 0.7mm and thickness 10μm.
Comparisons between simulated and experimental stiffness are presented.

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Research on the robot hand actuated by pneumatic muscle actuators is significative for its complaisance and dexterity. In this paper, a new kind of dexterous hand is designed and produced. The layout of tendon is analyzed and optimized. Furthermore, a single finger is controlled by Fuzz-PID and the good control precision is achieved. And, the master-slave control of the whole dextrous hand is realized simulating the movement of human hand with a cyber-glove.

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