In pneumatic position and force control systems, nozzle-flapper type servo valves are usually used for the pressure control. This paper proposes a linear model for a 4-port nozzle-flapper type pneumatic servo valve, which also includes the influence of the flow force, by deriving it from a full nonlinear model. The proposed linear model had a better agreement with experimental dynamics response than the former one which neglects the flow force. Furthermore, the proposed model was applied to achieve the differential pressure control between two symmetrical control chambers. A two degree-of-freedom (TDF) controller was designed based on the proposed model. The experiment results showed that differential pressure controllability could be improved for the reference input tracking and disturbance restraining by using the proposed model.

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Seals are generally inexpensive machine elements, but in industrial fluid power systems the costs of sealing failure can be much higher than the cost of replacing the damaged seal due to, e.g., costs related to process downtime. Consequently, careful design evaluation is needed. In this study, the capability of a large diameter rotary face seal of spring-loaded type to respond to unwanted axial motion between the sealing surfaces caused by sudden changes in loading of components of the process machinery was evaluated.
Explicit fmite element analysis, well suited for highly non-linear problems involving frictional contact, was used to compute the response of the seal to forced relative axial motion of the sealing surfaces. For condition monitoring, temporal variation of the total contact force exerted on the counterface, i.e., the sealing force during excitations was recorded, representing simple virtual sensor output describing the relation between axial motion and contact situation.

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A new hydraulic transformer (named NHT) prototype has been designed and tested by Zhejiang University in China. The results show that the HT can realize the function of transforming pressure, but its parameters such as efficiency and noise should be improved further. To help optimizing it, CFD-simulation using commercial software FLUENT is introduced. And the fluid field inside this hydraulic component can be theoretically analyzed. The velocity field and pressure distributing at different places such as the oil gap between the cylinder block and the valve plate, and between the valve plate and the end cap, or inside the cylinder chamber are founded. And the flow fields were analyzed in different rotate speeds and control angles. Besides the flow field was discussed under different grid cell numbers. The conclusions contribute to the understanding of the flow conditions inside the NHT and thereby supply dependences foroptimization on the NHT.

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A spool valve as a flow direction control valve has usually been used in a hydraulic system. In recent years, some hydraulic actuator systems need high accuracy control of the spool valve in order to control the delivery precisely. For the reason, it is very important practically to know dynamic motion of the spool. To analyze the dynamic characteristics of the spool valve, it is necessary to consider the dynamic motion of the spool.
Springs, solenoids and working fluid, which is pressurized by the pump in the circuit, support the spool. The motion of the spool is governed complicatedly by pressure force, flow force, electromagnetic force and mechanical spring force acting on itself. As a result, it is difficult to analyze the dynamic motion of the spool, and therefore, any commercial code to calculate the dynamic characteristics of the spool valve dose not exist at present.
Final target of this study is to develop numerical code to predict precisely the dynamic motion of the spool valve. As the first step, dynamic characteristics of a spool valve coupled with electromagnetic and mechanical effects have been conducted in the present paper.

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OHC-Sim is a simulation package for design of an oil-hydraulic circuit and analysis of its dynamic characteristics. To make the design and the improvement processes of an oil-hydraulic circuit more effective and systematic, OHC-Sim had been developed with the support of JFPS and has been enhanced in the research committee in JFPS. OHC-Sim is executable on personal computers in Windows® environment, and provides easy design and improvement of an oil-hydraulic circuit based on the simulated results. However, in order to enhance the use of OHC-Sim, it is desirable that the simulation of the dynamic characteristics of a pneumatic circuit becomes executable on OHC-Sim. In this study, to enhance OHC-Sim to the simulation of a pneumatic circuit, the bond-graph models for pneumatic components are discussed. And, by using the user-customized function, these bond-graph models are registered to OHC-Sim, and the simulation of dynamic characteristics of a pneumatic circuit is carried out.

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The paper describes the identification of the variable critical gain and natural frequency of the pneumatic cylinder using the self-excited oscillations method. The pneumatic drives are characterized by the low stiffness of the pneumatic cylinder which depends on the piston position and determines the natural frequency of the cylinder. The variety of the stiffness in dependence on the piston position can be obtained using the curve describing the course of the critical gain and natural frequency in dependence on the piston position. This feature is a disadvantage by the closed loop control of the piston position. The low stiffness should be taken into the account by the design of the pneumatic servo system operated in the closed loop, because the natural frequency of the cylinder depends on the stiffness and limits the closed loop gain and quality of the step response of the controlled system. The identified curve can be used for the design of the adaptive controller with variable on the piston position dependent gain. The described approach is presented by the measurements and results realized on the test rig.

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Pneumatic system is applied in a wide range of industries. There are many kinds ofpneumatic circuits that are used in different applied cases, such as transportation, clamp, press, etc. Among those pneumatic circuits, pneumatic circuit with only one cylinder controlled by one valve is primary for application, while branch circuit, which is consisted of multiple cylinders controlled by one valve, and manifold circuit, which is consisted of multiple cylinders controlled by multiple valves, is commonly applied in practices. In this paper, a simulation program for complex pneumatic circuits, especially for branch circuits and manifold circuits, is developed for model selection and characteristic calculation. Firstly, outline and specifications of the simulation program is introduced; secondly, modeling and simulation method of branch circuit and manifold circuit are explained; finally, an example of application is presented to verify the accuracy of the simulation program.

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This paper deals with the dynamic characteristics of an electro-pneumatic hybrid positioning system. This system is composed of a pneumatic, an electric and a mechanical driving sub-system. The pneumatic driving system controls the pressure supporting the inertial mass, which means that the pressure is correspondent to the gravitational force acting on it. And the electric driving system with small capacity moves the inertial mass vertically through a ball screw as a mechanical driving sub-system. In the present study, in order to developing the electro-pneumatic hybrid positioning system, the mathematical model of this system has been refined by comparing calculation data with the experimental results, especially by measuring precisely frictional force of the ball screw. And the power consumption as well as the dynamic characteristics has been investigated numerically when the inertial mass is moved vertically upwards and downwards during one cycle by the electric driving system through the ball screw. The data on the power consumption during one cycle will be useful to select a suitable driving motor at the design stage.

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This paper makes modeling and simulation for some simple cylinder halfway stop systems with valves of different center configuration. Simulation gives the displacement curves of the piston in the working stroke and over-shoot values are also obtained according to each kind of halfway stop system. Furthermore, experimental systems are built and displacement curves are also achieved in these experimental systems, which has validated the simulation research. Comparison analysis and characteristic summary are dealt with different systems.

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Diffused pneumatic silencer has been widely used in pneumatic fields because of its small dimensions and high performance on noise reduction. Numerical simulation of its interior and exterior flow field is important to studying the gas flow in the silencer and the flow structure outside the silencer, understanding the mechanism of its noise reduction. Porous media model and Darcy-Forchheimer principle are used as the basic theoretical frame in this paper. The unified governing equations are used to describe the compressible flow in and out of the silencer. Robust numerical scheme is used to discritize the equations and the TDBC (Time-dependent boundary conditions) is used to treat the non-reflect boundaries. The detailed structures of the inner and outer flow field of the diffused pneumatic silencer are gotten. The results of the simulation display the characteristics of the flow in the silencer. And the structure of the flow outside the silencer that can be compared with the experimental data is gotten.

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Information concerning the flow rate of pneumatic components is essential for both selecting the right component at the design stage and validating different performances of a circuit. Recently, new procedures based on the measurement of the transient response for the charge or the discharge of a tank have been proposed. These procedures are corresponding to an inverse approach that enables the mass flow rate in a component to be identified. The presented work investigates these new approaches and discusses the problem related to the use of inverse models. The heat transfer problem, which appears to be the main difficulty, is illustrated in order to analyze the relevancy of the thermal hypothesis.

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Aspirating smoke detector uses aspirating fan to draw air from the protected area via a network of the sampling pipes and holes, analyses the air and generates warning signals when the concentration of the smoke in the air is over the limit. After the analysis from the view of hydrodynamics, the physical and mathematical models are established. By programming and calculating, the sampling holes' flow rate and the transport time in which the air is drawn from the sampling holes to the detector are got. If each sampling hole's flow rate is not balanceable or the longest calculated transport time exceed 120 seconds (according to NFPA 72), the diameters of the sampling holes are optimized. The calculated results are compared with the experiments, the errors are less than 10%. It is proved that the physical and mathematical models can be used practically.

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High servo control response and high energy-efficiency are requested in hydraulic servo systems of current hydraulic machines. This investigation concurrently implements energy-saving control and velocity-force control for simultaneously realizing high velocity-force control response and high energy-efficiency for hydraulic valve-controlled cylinder systems. The velocity-force control of the hydraulic cylinder, including 1st stage of velocity control and 2nd stage of force control, can be applied in hydraulic machines, i.e. injection moulding machines. The energy-saving control implemented here contains load-sensing control, constant supply pressure control and constant supply power control. The concurrent control of energy-saving control and velocity-force control of the hydraulic valve-controlled cylinder system becomes a two-input and two-output control problem. For that, an intelligent control strategies using fuzzy sliding mode control is developed. The experimental comparisons of the four different systems, including velocity-force control with load-sensing control, velocity-force control with constant supply pressure control, velocity-force control with constant supply power control and velocity-force control without energy-saving control, are implemented for the same velocity-force profile. The minimum consumed powers in each system are compared. The feasibility of the concurrent control of energy-saving control and velocity-force control is verified experimentally.

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Hydraulic actuation system is typical displacement control system whose performance is subjected to random inputs from noise, random disturbance from pump vibration or parameter changes. Through importing the integral item of residual error in different rank, this paper establishes the Proportion-Integral Observer (PIO) that can eliminate the influence of random input, parameter excursion and inherent disturbance and realize the fault diagnosis robustly. In order to reach the high fault coverage and low false alarm, this paper provides twin-threshold and corresponding fault decision-making strategy that not only considers the inherent noise existed in the system but also can manifest the fault information effectively. Application and simulation of hydraulic actuator system indicates that the adaptive fault diagnosis can detect the failure in high precision at the stochastic condition.

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Pump dynamic response, the speed in which a pump can build up pressure due to disturbance, system flow demand, is one of its most important characteristics. In high performance hydraulic control systems, normally we utilize a fast response, but expensive, variable displacement pressure compensated Piston Pump. Inexpensive Vane Pumps cannot be used because their very poor dynamic behavior, which is inherent from their construction and principle of operation. In this paper we apply Control Theory to analyze and investigate vane pumps and consequently suggest a possible redesign to improve their dynamic response. Performing stability, disturbance and speed of response analysis reveals that pump dynamic behavior is dominated by the parameter ratio Bvf/Ksp (Bvf-viscous coefficient, Ksp-spring constant). Upon completion of our study, we carried out a quantitative calculation of those parameters for a specific re-designed vane pump. In the re-designed vane pump speed of response was improved by factor of 35 and can now be used in high performance hydraulic servo systems, where high bandwidth is required.

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This paper deals with online parameter estimation of an electrohydraulic servo (EHS) system and with robust control of the EHS system utilizing the parameter estimated online. In this study, the natural frequency of the EHS system is estimated using pressure sensors based on the equation of motion and equation of continuity, and the estimate of the natural frequency is utilized to enhance the robustness of the EHS system combined with a parallel feed-forward compensator (PFC). The optimal value of one of the PFC parameters is strongly influenced by the natural frequency of the EHS system and is adaptively varied using the estimate of the natural frequency. It is shown that the natural frequency of the EHS system can be estimated relatively accurately using the method proposed, and that the robustness of the EHS system to the plant parameter variations can be enhanced by adapting the PFC parameter.

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In this paper, the position/pressure control of a hydraulic cylinder using a hydraulic transformer is studied. A hydraulic transformer based on FFC pump/motor is used as a control component to drive the cylinder with a load horizontally. The two-degree-of-freedom (2DOF) design technique is applied to obtain the positioning controller with tracking performance and robustness for uncertainties while the structure of pressure controller is given by internal model principle to compensate stepwise disturbance. With these controllers the nonlinear friction torque, the leakage of the transformer and the load force acting on the cylinder can be compensated and the experimental results show that the sufficient accuracy of position and pressure are obtained.

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The paper presents and discusses a R & D-view on trends in development and best practise in design of both lowpressure and high-pressure tap water hydraulic components and systems for motion control as well as open-ended solutions various industrial applications. The focus is on the advantages using ordinary tap water and the range of application areas are illustrated with examples, in particular within the food processing industry, humidification operations, water mist systems for fire fighting, high water pressure cleaners, water moisturising systems for wood processing, lumber drying process and mobile machines and equipment that operate in environmentally sensitive surroundings. Today's progress in water hydraulics includes electro-water hydraulic proportional valves and servovalves for design of motion control solutions for machines and robots. The remarkable property is that the components operate with pure water from the tap without additives of any kind. Hence water hydraulics takes the benefit of pure water as fluid being environmentally friendly, easy to clean sanitary design, non-toxic, non-flammable, inexpensive, readily available and easily disposable. The low-pressure tap water hydraulic systems cover up to around 50 bar, and 2-4kW having a strong potential to compete with pneumatic and electrical solutions in many applications. The high-pressure water hydraulic systems cover typically up to 160 bar pressure from pump and to motors and actuators 140 bar. Recently, dedicated pumps and accessories running with sea-water as fluid are available. A unique solution is to use reverse osmosis to generate drinking water from sea-water, and furthermore for several off-shore applications. Furthermore, tap water hydraulic components of the Nessie® family and examples of measured performance characteristics are presented and the trends in industrial applications and need for future are discussed.

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Water hydraulic servo system is an attractive system source for its environmentalsafety. In this system, the problem for precise control is the uncertainties and/or the unmodeled dynamics which includesparameter variations depending on driving conditions and nonlinearity of system e.g. friction force, flow equation and so on. In this paper, we discuss the control performance of adaptive positioning controller for water hydraulic servo cylinder. This controller method aims to reduce the tracking error tend to zero for given reference signal asymptotically and ensures controller parameters keep being bounded. Based on the least square method, parameter update law is given and adaptive tracking controller is constructed. The robustness is examined experimentally for supply pressure changes and load fluctuations.

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Many studies have been conducted for quantitative/qualitative analysis and comparison of various teleoperation schemes. Position-position, force-position and 4-channels are to name a few. However most of this research has been focused on electrically actuated manipulators. This paper documents the comparative study of various teleoperation schemes explicitly for hydraulic manipulators. Identical water-hydraulic actuators have been used as master and slave. Three popular schemes of teleoperation: position-position, force-position and 4-channels have been implemented and tested. The results are compared on the basis of criteria established by other researchers for electrically actuated manipulators. The study has been done using manipulators with single degree of freedom to emphasize the comparison. The research has been carried out with a goal to extend the number of degrees of freedom in future to obtain a practical water-hydraulic teleoperation system useful in industrial applications such as International Thermonuclear Experimental Reactor (ITER).

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Force output of a hydraulic cylinder can be controlled by using either load cell or cylinder pressure feedback. Both forms of feedback have good features: load cells usually give more sensitive and accurate response to the external loads while pressure cells respond faster to changes in valve input and are much easier to install. Pressure feedback can easily be used also with rotary actuators but torque sensors are not widely available. In this study, force based motion controller design for 3-DOF water hydraulic manipulator is implemented. The target of this study is to compare the performance of load-cell feedback that is almost ideal feedback for force in terms of high sensitivity and accuracy to more practical and cost affective pressure feedback. Measured results with 3-DOF water hydraulic manipulator are presented in order to verify the findings.

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In many hydraulic control applications, classic linear controllers are still employed, although there exist a number of number of nonlinear control methods, which may be better suited for handling the intrensic non-linearities often found in hydraulic systems. The focus of this paper is therefore on comparing different linear controllers, based on both simulation and experimental results, to determine what is obtainable when applying standard linear controllers to a hydraulic SISO servo system. The paper furthermore addresses how the performance may be improved by using internal pressure control and model based information to include feedforward information. The control strategies considered are all based on measurement of piston position and pressure only.

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Pneumatic positioning actuators are very commonly used in the control of process control valves in petroleum, chemist and paper industries. During the last decade several ideas have been presented howto use water hydraulics in different applications. Low-pressure water is available in some process industrial applications a little bit the same way as pneumatic power. Lately very demanding performance specification requirements havebeen presented for positioners of process valves. In this paper requirements set to control components of pneumatic and low pressure water hydraulic drives in order to fulfil these high quality performance specifications are studied. Different experimental tests have been done with both systems and results show that the specification can be fulfilled, but quite high performance components are required.

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This paper deals with dynamic characteristics of a direct-pressure sensing water hydraulic relief valve. Four hydrostatic bearings support the main valve to reduce hysteresis of static characteristics of the valve. Hence, Coulomb friction acting on the main valve is not available as damping force. A damping orifice is inserted between the main- and pilot valves to get a damping force for the main valve, while the orifice diameter affects on stability of the main valve. In addition, the motion of the pilot valve has large effects on the response of the relief valve itself To show these influences, we compute the response to a step input of relief flowrate with the MATLAB/Simulink. The results show that the design parameters affecting the stability are followings:(1) the damping orifice diameter, (2) spring stiffness for the pilot valve, and (3) volume of a chamber between the damping orifice and the pilot valve.

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This paper concerns a newly designed water hydraulic actuator to make reciprocating linear motion without any directional control valves outside. It works with only supply of low pressure water, such as from tap water network. The object of this paper is to introduce the idea of construction and working principle of the actuator and to present some experimental results gained by prototypes. Two different prototypes, with a short stroke (approx. 20 mm) and a long stroke (approx. 200 mm), are produced. Fundamental performances were tested for the two types and good results were gained. Main piston's displacement, speed, force, and supply flow rate and pressure were measured under steady working conditions. The experimental results are presented and some considerations to improve the characteristics of them are also discussed.

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Today, Remotely Operated Vehicles, or ROV's, are the dominating type of vehicles for underwater operations and very much the working horse of the North Sea, and both the military and the scientific sectors are increasing their use of ROVs. An ROV is normally designed for underwater work using oil hydraulics or electricity for propulsion and tool control. ROV's using the surrounding water itself as the energy carrier for propulsion and tool control has never been successfully developed. The paper presents research results on a new ROV with water hydraulic propulsion system is being developed at Bergen University College. The design of the propulsion system is based on components available on the market. The ROV will have two thrusters for manoeuvring in the horizontal plane, and one thruster for vertical positioning. Static calculations and dynamic simulations have been performed to investigate the performance of the water hydraulic propulsion system. The simulations have been performed applying VisSim. The flow control valve has been tested to investigate the capability of flow regulation at low flow rates. Furthermore, this paper presents the selected experimental results and performance results.

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Filtration in water hydraulic system may be problematic, due to chemical, physical and biological contamination. This contamination may cause quick increase in the pressure difference over the filter element. The aim of this research was to test different kinds of tank sizes and filter combinations and to determine their effects on water quality in a water hydraulic system. In this paper the results of these experiments are presented.
Experiments were made with pilot-scale water hydraulic systems. The systems induced no biological contamination and only a minimum amount of physical and chemical contamination. Filtered tap water was used as a pressure medium. The tested filter ratings (β>5000) were from 10 to 90 gm depth type elements and the three different tank sizes 62, 105 and 148 litres. Experiments were made with water without amendments, and water with nutrient and particle contamination. The test periods were up to four weeks. Pressure difference over the filter, fluid flow and temperature are monitored. Microbiological analyses consisted of total number of cells, heterotrophic viable plate counts and the determination of biofilm formation. In addition, dissolved organic carbon concentration and particle counts were determined.
Solving the microbiological problems of water hydraulics requires new approach to tank design methods that support the long-term working of the water hydraulic system. It is possible to (1) reduce microbial growth in water and on surfaces with a proper tank design, (2) keep microbial growth under control and (3) considerably extend the filter lifetimes by using twophased filtration in water hydraulic systems.

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In hydraulic manipulator applications effective joints movement range of above 180° is often needed. Vane actuator has maximum movement range about 270°. However, water hydraulic vane actuators are quite expensive to manufacture. Thus we investigate a possibility to use so called chain drive instead of vane actuator. Chain drive consists of two cylinders which are connected in series with a chain. Reduced model for chain-drive equals to symmetric cylinder and can be compared with a vane actuator of same size. Concerns with chain drive are the smoothness of sprocket turning around, stiffness of the chain and minimum required back-pressure level for keeping chain tension. In this paper a chain drive is designed, built and tested. We also compare chain drive's and vane actuator's properties mathematically from control point of view. We can conclude that chain drive's characteristics almost equal with vane actuator and it is much more cost effective.

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A water drive spindle for diamond turning machines is proposed. The spindle uses water flow for driving the rotor by a water drive motor, for supporting the rotor by water hydrostatic bearings, as well as for coolant. As water is not only incompressible and clean but also low viscosity fluid, it is considered that a high-speed and precise rotational motion will achieve in the clean environments for ultra-precision machinings. The present paper reports a structure of the spindle as well as the operational principle of the spindle. In the present paper, theoretical equations used for designing the spindle is derived. The characteristics of the spindle are studied theoretically and experimentally.

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As water hydraulics is more and more highlighted in wide applications, many varieties of research on design, materials and manufacturing methods of water hydraulic components have been carried out. Especially, water hydraulic piston pump used to be the subject of study in relation to its relative sliding movement. In these relative sliding parts, the leakage and friction probably took place because of the characteristics of low viscosity and poor lubrication of water. In order to reduce the leakage and friction, the relative sliding parts are filled up nearly by using engineering plastic as an anti-wear material on sliding parts. Compared with an oil hydraulic system, a water hydraulic system has fundamental disadvantages of large friction, high leakage, high wear, corrosion, etc. A mechanism of rod type piston was considered to reduce friction of the piston's movement in a water hydraulic piston pump. Friction and leakage of the rod type piston was analyzed and compared with those properties of the conventional plunger type piston. An experimental device was set up to evaluate friction and leakage of those pistons. A PEEK piston was also tested as another alternative piston of a water hydraulic pump.

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The paper presents research results using IT-Tools for CAE/CAD and dynamic modelling, simulation, analysis, and design of a water hydraulic vane actuator for motion control of robot manipulator arm. Matlab/Simulink and CATIA are used as IT-Tools. The development and design a novel water hydraulic rotary vane actuator for robot manipulators is presented. The contribution proposes mathematical modelling, control and simulation of a novel water hydraulic rotary vane actuator applied to power and control a three-links manipulator. The results include engineering design and test of the proposed simulation models compared with IHA Tampere University's presentation of research measurements from a similar robot manipulator arm driven by tap water hydraulic components. Experimental and simulation results are compared for evaluation and verification of developed mathematical models of the motion control of the manipulator. Furthermore, presents performance results of to follow trajectories of path motion control.

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This paper presents a time-dependent mathematical model of a hybrid (hydrostatic/hydrodynamic) thrust pad bearing as a slipper of swash-plate type axial piston pumps and motors for the use of tap water under mixed and fluid fihn lubrication condition. Effects are examined of the load eccentricity, time-lag of changes in the supply pressure and load, surface roughness, recess volume, and the revolution radius. The bearing's motion is simulated three-dimensionally, including roughness interaction and asperity contact. Solutions are obtained regarding the friction, flow rate, power loss, and stiffness. Calculations indicate that the eccentric load causes local contacts. The preceding change in the load poses a larger motion of the bearing. The hydrodynamic effect becomes marked as the revolution radius increases. As the recess volume increases, the bearing stiffness decreases.

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In disaster sites, the remote control of construction machinery is required to ensure the safety of the workers. However, the current remote control systems are limited in types of machines and numbers. A remote control system we have developed has advantages in portability and dexterity by using lightweight pneumatic robot arms. The effectiveness of the system has been confirmed with a small type backhoe. In this research, a system was developed to improve fl exibility. First, the moving angle of the robot arm was enlarged. Then, the sliding system was developed to move the robot back and forth so that the robot arms can operate not only the levers to control the arm of the backhoe but also that of the acceleration. Moreover, CCD camera was attached to inform the vision from the backhoe. The system was applied to an ordinary backhoe whose bucket size is 0.28 m³. Some field tests were conducted and the effectiveness of the developed system was proven.

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Active control type pneumatic isolation systems are widely used in semiconductor production processes. Most of them are actively controlled by nozzle flapper type servo valves, since they have fine characteristics as imperfect pressure integrators. But nozzle flapper type servo valves exhaust a lot of compressed air, for the sake of controllability. In this research, we firstly develop a pressure differentiator using an isothermal chamber, a cylindrical type laminar flow element and a differential pressure sensor. Then, by using the developed pressure differentiator and a spool type servo valve, an imperfect pressure integration system with much lower exhausted air flow rate compared to the system with nozzle flapper type servo valve, is constituted. Finally, the proposed pressure integration system is applied to the control of active vibration isolation system. The experimental results indicate superior performance of the developed system, especially in much lower energy consumption.

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Precise positioning system is required in the fields of semi-conductor manufacturing process. A pneumatic servo table system is one of a precise positioning system. The features of the table are little friction force and little heat generation. Generally, the controller of this system is designed by neglecting the characteristics of servo valves. However, in high frequency band, the response of this system becomes unstable because of the characteristics of the valves. In this paper, we demonstrate that by considering the characteristics of servo valves, the position control of a pneumatic servo table could be improved. First, the dynamic characteristics of servo valves were examined. It became clear that the characteristics could be described as a second-order system. Then, the servo table system was designed as a fifth-order system. It became clear that the position accuracy of this system were greatly improved.

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In this paper, a newly developed pneumatic rotary actuator is introduced, which is specially designed for angular position control. The actuator incorporates a built-in air brake and an angular displacement sensor. The basic behavior of the brake is tested. On this basis, for angular position control some control systems are proposed. The first system is the on-off valve-based position control system, which has the advantages of simple control algorithm, easy implementation and lower cost. The second system is the proportional valve position control system with simple PID algorithm, which can reach a required positioning accuracy but with a lower stiffness against disturbance. The third system is the proportional valve position control system with a composite control strategy of PID combined with brake aided positioning, which can reach the same positioning accuracy and no overshoot with disturbance takes place, as compared with the simple PID.

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Today, the technical subject for the air pump used in the offset printing machine is to reduce sliding friction and wear of vanes. If we could improve the energy efficiency, we could successfully design a smaller air pump with a longer life.
In this paper, first of all, total power consumption of the air pump was measured by axial torque and analyzed according to components of a frictional force. As a result, it was found that most of the power is consumed at the sliding face between vanes and housing cylinder in the air pump. The power increases significantly due to the sliding friction between the vanes and their guide slots of the rotor, especially when the vanes are forced to move inward. On the basis of these results, the importance of the sliding friction of the vanes was confirmed quantitatively and the arising mechanism of the sliding friction of a vane against the slot face of the rotor was investigated theoretically as well as experimentally, and finally, we proposed some counter measures to reduce the sliding friction of vanes.

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This paper shows a performance analysis for conical type sealless cylinders and rod bearings. The pistons withoutseal have partly cylindrical and conical shapes. 2 dimensional Reynolds equation and FD (finite differential) numericaltechniques are utilized for the performance analysis. The relationship among self-centering forces and leakage flows areinvestigated. Also, optimal design values for a sealless cylinder are presented. A prototype of sealless cylinder whichhad rod bearing with four pockets, five pockets, and six pockets was manufactured respectively. Leakage flow test isconducted to evaluate performance of piston and rod bearing in sealless cylinder.

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The fluidic muscle cylinder consists of an air bellows tube, flanges and lock nuts. It's fbatures are softness of materialand motion, simplicity of structure, low production cost and high power efficiency. Recently, unlikely the pneumaticcylinder, the fluidic muscle cylinder without air leakage, stick slip, friction, and seal was developed as a new conceptactuator. In this study, we carried out the finite element modeling and analysis about the main design variables such ascontraction ration and force, diameter increment of fluidic muscle cylinder. On the basis of finite element analysis, theprototype of fluidic muscle cylinder was manufactured and tested. Finally, we compared the results between the test andthe finite element analysis.

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In the case that the high compliance and high safety are required, the use of pneumatic muscle for robot joints is a goodchoice. In this paper, a bio-mimic structure of pneumatic muscle robot arm is introduced and the differential pressureprinciple is applied to control the arm. In order to solve the practical problems that difficult regulation with pneumaticmuscle and the lower accuracy of position control, a proportional stiffness regulation method with easy implementingfeature is presented through theoretical analysis and experiments. On this basis, the position control of the joint withpneumatic muscle is implemented, for which the adaptive and self-learning neural-PSD controller is adopted. Testsindicate that the joint stiffness is easy to regulate by the method and joint operation shows a quick response and highaccuracy.

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The air with certain pressure in a pneumatic cylinder is usually exhausted into the atmosphere after work process. It is ofsignificant that the air energy can be saved and re-used. In this paper, the constitution of an exhausted-air reclaimingsystem for pneumatic cylinders is studied. To find the possible influence on the cylinder work process, the effect of thesystem on the cylinder velocity characteristics is also researched and different control switch points are tested.Experimental results show that attaching a reclaiming device would not cause bad influence on the velocity stability if theswitch point could be properly controlled. Experiments also indicate that the switch control differential pressure ΔP_swvaries with P_c in the receiver and the supply pressure P_S would affect the velocity stability of cylinders. Therefore toreclaim more energy and make less influence on the cylinder velocity characteristics, the suitable differential pressureΔP_sw and switching-point are also tested and suggested.

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Soft robot inspired from natural systems is one of keywords in the robotic field in last decade. Accordingly, many typesof artificial muscle actuators are developed. On the other hand, using an electro-conjugate fluid (ECF), which generatesa powerful jet flow when subjected to a high voltage, we can construct a tiny pressure source. This paper proposes anovel micro artificial muscle actuator (<1cm³) utilizing the fluid. The essence of this study is to develop the microartificial muscle integrated with micro pressure source, which enables us to construct an autonomous system and/orartificial muscle array. The contraction characteristics and normal force characteristics of the actuator were measured.The maximum contraction rate was around 16% and the force generated was about 0.2N with applied voltage of 6kV.The experimental results confirmed the effectiveness of the proposed actuator.

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An Electro-Conjugate Fluid (ECF) is considered as a functional fluid like electro-hydro dynamics fluid, and it has a remarkable property that a jet flow is generated between two electrodes when a high voltage is applied to the electrodes. In this study two types of linear actuators consisting of the pistons and cylinders using an ECF are proposed. The one has a structure of a coil type electrodes, and the other a structure of mesh type electrodes. The proposed actuators are fabricated, and their basic characteristics such as piston velocities vs. applied voltages to electrodes and the load characteristics are examined in the experiment. The experimental results show that the proposed linear actuators have the possibilities to be used as the functional linear actuators.

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This paper presents the improvements for the performance of a micro-electrohydrodynamic (EHD) pump and the fundamental model theory based on unipolar charge conduction. The EHD pump was fabricated with thin stainless wires which are the diameter of 0.3mm. An electrode pair consisted of one emitter electrode and two collector electrodes. The distance between the emitter and the collector electrode in an electrode pair had a 0.2mm. Static pressure tests have been performed with a dielectric fluid. In order to increase the pressure performance, the electrode pair was increased from one to five at the distance between the electrode pairs, 2.0mm. As a result, it is found that the increase of the electrode pairs improve the pressure performance. The EHD pump produces a static pressure about 700 Pa with five electrode pairs using Dibutyl Sebacate. Both experimental and theoretical pressure results show a liner relationship. This linear relationship confirmed the unipolar conduction concept theoretically.

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The purpose of this study was to develop the new type actuator which has flexibility by using an EHD phenomenon for the application to the small machine or welfare system. The EHD phenomenon is a phenomenon that generates the flow in the insulating fluid by applying a high voltage electric field. Especially, rotation type actuator using an EGD phenomenon was developed by this study. And, EGD (Electro Gas Dynamics) phenomenon is a kind of the EHD phenomenon which occurs in the gas. Then, this actuator was called EGD motor. The EGD motor has one pair of electrode, one of these is a cylindrical electrode for a stator and another is L shaped electrode for a rotor. We changed the shape of electrode and measured the torque and rotation speed, to evaluate the rotational performance of the EGD motor

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An electro-rheological Gel (ERG) is developed to overcome two shortcomings of Electro-rheological Fluid (ERF): sedimentation of ER particles and the seal structure required to allow the use of ERF in machine elements. The ERG shows a wide shear stress variation in response to an applied electric field. To apply an electric field to the ERG, it is necessary to sandwich the ERG between plane-parallel electrodes. However, it is impractical to wire both electrodes to a high voltage supply. In this study, one-sided electrodes are proposed to simplify the wiring structure. The basic characteristics of ERG on one-sided electrodes are evaluated experimentally. It is found that these electrodes exhibit nearly the same performance as the conventional plane-parallel type. The one-sided ERG mechanism is especially useful in applications involving rotating or sliding parts.

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Magnetorheological (MR) fluid is a functional, smart or controllable fluid, which responds to magnetic field, changing its rheological properties. The increased resistance to flow of an MR fluid is proportional to the strength of magnetic fi eld. A typical MR fluid consists of iron particles, suspended in a carrier liquid such as synthetic oil or water. Proprietary additives, to discourage gravitational settling and promote particle suspension, are added to enhance lubricity, modify viscosity, and inhibit wear. In recent years devices and systems using MR fluid technology have been commercialized across wide industry applications, including automotive, industrial and civil engineering. In that development two key issues for the commercial success of MR fluid technology-durability and settling-have shown continual improvement as a result of formulation research. As a result, MR fluids today are strong, durable, adaptable and highly developed with fundamental material data and device design and models.

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Flow visualization of a liquid crystal mixture in mini cylinders is conducted under application of the rotating electric fi elds. The mini cylinder with the electrodes on some parts of the inner surface of the cylinders is used. The cylinder is 1.0mm or 2.0mm in length and 1.1 mm in diameter. The three-phase alternating currents and the rectangular wave voltages are used as the rotating electric fields. The frequency and the amplitude of the voltages are changed to investigate the effect of the unsteady electric fields on the flow phenomenon of the liquid crystal mixture. When the frequency and the voltage of the three-phase voltages are 60Hz and 260V the rotation speed of the liquid crystal is 14.3 r.p.m. On the other hand, when the frequency and the voltage of a rectangular wave voltage are 600Hz and 200V the rotation speed is 2.7 r.p.m.

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This paper describes the viscosity variation of a liquid crystal under electric field, and its application to a controllable sliding bearing. Liquid crystal is known as a homogeneous organic liquid characterized by the long-range order of its molecular orientation. When an electric field is applied to a liquid crystal film as lubricant, the orientational order of molecules become parallel to the applied field, whch causes apparent viscosity variation. In this paper, a controllable slinding bearing system was constructed and its dynamic characteristics were studied. When step load or sinusoidal load was applied to the bearing pad, the film thickness was successfully controlled by a conventional PID controller. The response frequency was also studied in the experiment.

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Walk training is good rehabilitation for old people and handicapped people.Then it is considered the effective measurement for decreasing bedridden people and wheelchair users. In walk training, they frequently use walkers, walking sticks, etc. It is problem that these kinds of support tools are not flexible and mobile because their handicap conditions are different. New support tools are demanded to be intelligent and personalized.
We are developing a new walking support machine for old people and handicapped people, because they expect to move easily by themselves. The machine is equipped with two ER devices which compose a elctrorheological fluid clutch (ER clutch) and a motor, and able to work with smooth power assistance or safety breaking.
In this paper, we refer a developing concept in the new walking support system, and explain a mechanism and design of the ER devices. In addition, we also report some experimental results, because we have examined on characteristics of the ER devices.

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