In this article, the IHP's research activities in four different fields are described. An adaptive control will be treated of which is capable of changing the controller parameters of a state controller with the sudden changes in the open-loop behaviour by means of a quick on-line-identification. Furthermore, two new circuit concepts for the saving of energy will be treated of. Electrohydraulic load-sensing serves to supply multiple consumers from one pressure sources. If only one consumer is fed by a variable pump, the control of a differential piston through a hydrotransformer and a pressure-ratio-valve serves to improve the static and dynamic transfer function of the system. The investigation of the contamination sensitivity of pressurecontrolled variable pumps and the analysis of the resulting increase in the leakage flow serves to increase the wear resistance and the lifetime of the components involved.

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The brief review of control laws, proposed or susceptible to proposition given in this paper, is based on the structure of linear and non-linear models adopted for the pneumatic positioning system which is under consideration. Attention is brought to relating and if possible, to justifying the control laws presented for the right field of control theory. A comparison is made between the theoretical possibilities of each control law. Also some questions open to discussion and some industrial applications are mentioned.

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This paper describes the following 4 systems developed by KOMATSU LTD. in order to improve operability and realize unmanned, automatic operation of construction equipment.
1. Laser guided automatic excavation system for hydraulic excavators
2. Shoe slip control system for bulldozers
3. Unmanned vehicle control system for dump trucks
4. Automatic operation system for wheel loaders
This paper also describes the position-detecting hydraulic cylinder, and the sensor technology developed by KOMATSU which is indispensable for realizing these systems.

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In big cities such as Tokyo, the number of urban renewal and infrastructure development projects is on the increase. Because of restrictive work site conditions in urban areas, compact construction machines with high mobility are favored.
To meet this need, we developed a new type of pile driving machine: the HITACHI RX 2000. With this machine, a piling attachment is directly connected to the tip of the multi-joined pile driver arm, and the computer-assisted guiding system allows precise piling work to be done. We call this new system “arm tip locus control.”
The system is basically a combination of proportional solenoid valves, a microcomputer, and sensors. However, many state-of-the-art innovations were employed in order to achieve precise arm tip locus control.

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The world-largest class hydlaulic mining shovel has recently been developed by Surface Mining Equipment for Coal Tecnology Research Association (SMEC). To operate with huge weight and inertia, a newly-developed electric-hydraulic control system aided microcomputer processing is adopted, resulting in superior controllability, greater production and better fuel consumption. This paper introduce the abstruct of the shovel which is fully used higher electronics control technologies.

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Pneumatics has been mainly used as main equipment for actuation and control of fluid force in manufacturing industry. For the past twenty years, it has shown its remarkable achievement by acting as the core in assembly device and material handling. Nevertheless, the continuity of the success is difficult to forecast. Thus, in our opinion the orientation of pneumatics must always be verified according to the circumstances and environment of the manufacturing industry which has changed remarkably.
This report is the contemporary approach to how pneumatics may be analyzed and how the future direction are based on.
Please note that the contents are based on the writer's personal opinion which do not necessarily reflect the orientation of our company and society.

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The automation and laborsaving in production factories becomes more and more important in the improvement of labor productivity.
This paper reviews the topics such as the progress in the automation and laborsaving of production factories by pneumatic components, the current situation and problems of the pneumatic components incorporated into electro-mechanical automation equipments, and the future problems of pneumatic components in production factories, mainly from an ecological point of view.

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The main characteristics of the hydraulics and pneumatics is that they are quite suited for the automobile. Electrohydraulic control technology has produced intelligent control and active safety of the automobile.
In recent years, various automotive hydraulic systems have been widely used. For example, for the power train, the electronic control automatic transmission, the device of driving systems of the engine cooling fan can be mentioned. The electronic control system for the automatic transmission is detailed. For the chassis, the 4-wheel power steering, the 4-wheel antilock brake, the semi active suspension, active suspension can be named. Full explanation is given to the suspension control.
Basic study of the automotive hydraulic system is advancing in the fields of system simulation and control, analysis of fluid flow, and tribology.

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Hydraulic systems are of great advantages to high-frequency controlling and high-efficient energytransforming as power transmissions. The prime characteristic is to use hydraulic fluid as lubricant. Hydraulic equipment consists of many bearing/seal parts and its performance depends deeply on them. For improvement of performance of hydraulic systems, it is important to clarify the behavior of their ‘tribology ’. In our society, the Japan Hydraulics and Pneumatics Society (JHPS), we have been organizing continuously the research committees on tribology and investigating on it. We built test apparatuses and studied experimentally. Also we reviewed the domestic and overseas papers on tribology and discussed them. In this report, we will introduce our activities and researches on tribology of hydraulic equipment, discuss these problems, and mention the trends and the future.

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This paper deals with the development of two-type ultra high speed valves, one of them is a highspeed digital valve whose switching speed is within 100 microseconds, and the other is an ultrahigh-speed servo valve with the spool displacement of 30μm and the bandwidth over 5kHz. In this study, commercially available multilayered piezo-devices are used to drive the coupled poppets of the digital valve and the spool of the servo valve directly. In the former one, by introducing a kind of feed forward control and employing some new methods, on-off-type coupled poppet valves with high-speed response to within 100 microseconds of switching speed are successfully developed. In the latter one, the hysteresis of the driving element of the valve is removed by introducing an inverse hysteresis element implemented on a microcomputers and operated in real time. As a result, a servo valve with the bandwidth over 5kHz is developed.

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The nozzle-flapper type servovalve has good characteristics (high response, compact design, low consumption), so it is used in many fields, e.g. aeroplanes, test machines, etc.
However, this type of servovalve needs first stage flow which causes leakage, and the user should take care to keep contamination levels low. For these reasons, the need for direct drive servovalves (DDV) is increasing. The DDV does not have first stage flow and is not influenced by contamination.
In this paper, a new DDV using a giant magnetostrictive material is presented. By using this material, a high performance DDV can be developed, i.e. with high output power, high response, high resistance to environmental factors (e.g. humidity, oil etc.).

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This paper deals with a new concept for constructing an optical control system with the minimum influence on operation environments and outlines the current status of the development of an optical actuator as an interface required to construct the optical control system. It describes that an optical actuator with the use of PLZT ceramics was found to be promising as a solid-state light-to-mechanic interface on the basis of the experimental results on step and on/off responses. To use the optical actuator practically, it is necessary to improve the response speed. The paper shows the possible way for the improvement.

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In the Japanese Hydraulics and Pneumatics Society, the first research committee of Pneumatics was organized in 1979. After that, six committees of pneumaitcs have been formed successively. A lot of researches on the pneumatics have been done by the committees. Some research results made by the committees are reported here.

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The root-locus showed what follows. 1) The value of the ratio has no effects on the form of the root locus, but the marginal value of the stability for the proportional gain increases as the ratio increases. 2) When the ratio exceeds the original airway resistance in the experimental system, the system becomes unstable. 3) The system remains stable but becomes more oscillatory when the lung compliance decreases, this is, the lung gets stiffer.
This paper describes the development of a soil nailing machine that is now in commercial operation, thetechnique being exploited by Soil Nailing Ltd. The machine basically consists of an electrohydraulicallyoperated mobile vehicle, both wheel and tracked types being used, to which is connected a pneumaticallyoperated air launcher capable of firing “nails” up to 38mm diameter, 6m long, at a very high exit velocity. This results in a highly manoeuvrable system that can fire nails economically, rapidly, accurately, and will be playing a vital role in a range of Civil engineering applications concerned with the strengthening of soils.

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This paper introduces a Bond Graph Simulation Program (BGSP) developed for evaluation of hydraulic systems as well as general ones. Bond graphs represent various components and systems in an unified manner. By virtue of a symbolic manipulation method to obtain state-space system equations, not only non linear characteristic functions but also user-defined outputs can be easily dealt with. Further, any reference values of state variables can be used in the definition of component functions. New features developed recently for BGSP and future problems to be solved are also presented briefly.

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Bilateral control is applied for a master-slave type electrohydraulic manipulator. Stability analysis of the master-slave type bilateral control system is very complicated. A simple design method of stability of bilateral control system is proposed. The stability characteristics of a system is represented using non dimensional parameters. Some experimental results of the manipulating motion of a master-slave servomechanism are shown.

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To produce a desired wave form, the required input control signal to a system mustbe known. If, for a repetitive duty cycle, the output and input signals of the system may be represented by quantize patterns, then the relationship between the input and output at any given point ofthe pattern can be considered as a simple gain. Thus, multiple independent gains (MIG) can be used todefine the complete pattern. If the gains at each point can be determined, the output of the system can be made to follow the desired pattern regardless of the linear or nonlinear nature of the system. This concept has been applied to direct both a linear analog system as well as an electrohydraulic system to follow a specified low frequency (0.1 Hz) repetitive pattern. The paper concludes with a discussion of the limitations and potential of the MIG concept.

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This paper deals with the control methods of electro-hydraulic speed servo control system with large power which is used in the aeroplane engine simulating rig. In order to obtain the fast response characteristics in the system, the dead beat control method combined with the fuzzy control is adopted by means of the simplified first-order and second-order mathematical models are established, and control experiments is carried out. The experimental results show that the satisfactory response characteristics are obtained by using the dead beat control method combined with the fuzzy control with the second-order model.

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Electrohydraulic servosystems are commonly employed to actuate flight control surfaces in aircraft, particularly in military aircraft. They are increasingly used in commercial aircraft to minimize pilot effort and to provide easy interface to flight control computers. In many of the applications the servoactuator is connected to a flight surface (load) through a compliant member that introduces additional dynamics. This paper addresses some of the issues related to the modeling of these kinds of systems, particularly the effect of friction in the actuator, and its effects on system performance. This paper also outlines approaches that can be adopted to reduce the effect of friction on system performance.

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The relationship was studied between compression-induced vane motion, called vane jumping, and chamber pressure in a variable displacement vane pump. To clarify vane motion character: sties, three experimental methods were applied:(1) eddy current displacement measurements, (2) capacitive displacement measurements, and (3) high-speed video filming. The x- and y-axis eccentricities of the cam ring to the rotor were specifically focused on. These measuring techniques reveal that the vane tip clearance is proportional to x-axis eccentricity, and that its maximum value is 0.8 mm. Results also indicate the vane detachment angle lagged with increases in y-axis eccentricity. We conclude that a detached vane is caused by excess pre-compression in the dead-volume zone.

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The paper reports upon numerical simulation tests carried out on a variable displacement axial piston pump equipped with multiple automatic controls. The swashplate control circuit includes three 3-way valves: the pressure compensator, the flow compensator and the torque limiter. The dynamic response of the system is evaluated for both separate and combined control functions. The effect of changes in the design parameters is discussed in terms of both sensitivity analysis and conventional discrete search.

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A measurement technique, that extends and integrates former experimental activities, has been developed to detect the variation with time of tooth space pressure in an external gear pump by use of a pressure transducer fi tted in the driver gear. The pressure signal from the miniature strain gauge sensor mounted in the bottom of the tooth space is taken out via slip-rings for acquisition and analysis. Angular phase is determined by an optical encoder connected to -the driven gear. The specific location of the sensor was selected to acquire a better insight and understanding of typical phenomena occurring within an external gear unit in operation.
Results of the investigations may lead to a more thorough treatment of aspects improperly described in the mathematical model and support interventions on the geometry features of the pump aimed at better performance and lower radiated noise from these units.

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In this paper the condition monitoring and fault diagnosing of slipper looseness failure in swash plate axial piston pumps are investigated analytically and experimentally. The paper first describes mathematical models of loose slipper failure. Then normal power spectrums and fault power spectrums are experimentally descussed. Through contrast between theoretical models and experimental models we can approximately judge quantity of loose slippers. Finally, a corresponding criterion of slipper looseness fault diagnosing is discussed.

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The influence of the piston rotation on the frictional forces between the piston and the cylinder has been studied experimentally for a swash plate type piston pump and motor. In order to measure the rotational speeds of the piston, the capacitance detecting method have been employed for the piston with the slits. The frictional forces have been measured by means of Piezo-type load washers connecting with the floating cylinder and the rotational speeds of the piston have been measured at the same time. The relations between them are discussed.

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This article deals with the control of variable displacement units connected to a constant pressure net. In particular the dynamical behaviour of two coupled secondary units in a speed- and torque control circuit is described and the decoupling of the two motors by the control technique is demonstrated. On this occasion results the possibility of recovering the energy into the hydraulic net. This onstellation is among other applications of special interest for power transmissions or testing benches, in case tension is applied to a traction mechanism or tape.

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Parametric performance of a helical coil pump, developed for operation in conjunction with wind turbines for farm irrigation, is studied experimentally. The results suggest rather promising behaviour with a wide variety of applications ranging from pumping water to chemical transport and fire-fighting. Economic considerations as well as the simplicity of design, operation and maintenance make the system particularly attractive.

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In this paper, an equation for the structural parameters of the hydrostatic bearing in a friction pair between eccentric crankshaft and connecting rod slipper-pad has been derived by means of an equivalent electrical net. A mathematical model for optimization of the slipper-pad has been established. With the aid of a computer, the optimal structural parameters have been obtained. Meanwhile, on the model for the dynamic characteristics of the bearing established, dynamic simulation has been performed. The extrusion effect of oil film on dynamic response has been discussed. Finally, the above analysis have proved that the optimum design is reasonable and reliable, and some favorable conclusions have been drawn.

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Recently, much reasearch has been done in projects seeking to dampen wind or earthquake induced vibration of tall buildings. Our particular reasearch involves the Active Mass Damper (AMD) System. This paper describes an AMD system developed for an actual structure using an electro-hydraulic servo mechanism, which controls torsional and translational vibration of the structure concurrently. The system makes use of two 36 ton AMD masses which are controlled using a single digital controller that implements optimal control theory. Following installation of the system on the building, experimental result showed the effectiveness of the system. This paper shows both simulation and experimental results.

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The performance and the versatility of a variable displacement axial piston pump are, to a large extent, determined by its controller. Upgrading of existing controllers is considered one of the major means of improving the characteristics of the pump. Sliding mode control (SMC) is proposed here for the control of such a pump. The control scheme, while showing a great potential for increasing the robustness of the control system, substantially increases the difficulties of system implementation both theoretically and physically. The success of the application will be evident when these difficulties are resolved. Pump controllers consisting of different hardware structures and actuators are considered in this paper. The feasibility of these controllers, when designed using SMC theory, is studied; necessary conditions for the use of SMC in the control of such pumps are established. Systems that are deemed to be theoretically feasible are simulated, and issues on implementation of these control systems are discussed.

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The proto-type of the world's first Hydro-Mechical Hybrid Transmission (HMHT), which is the hydro-mechanical compound transmission without any gear mechanisms. is introduced with historical back ground, its constructicn and performance.
Secondly, the plan of an improved vers; on to meet r equirements of cunstructon machAiery Wiht ths construction and the performance are discussed.

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A fuzzy logic controller, which consists of the linguistic defined fuzzy sets and the control rules, is designed and implemented in a microcomputer to control the position of an electrohydraulic servocylinder. Using the triangle shaped membership function, the normalized universe of discourse, and Tagagi and Sugeno's reasoning for the controller, the position of the servocylinder was successfully controlled.

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A digital electro-hydraulic control system was applied to machine tools and other industrial machines. The desired characteristics have been obtained, and the digital electro-hydraulic control system has been put to practical use.
Firstly, the paper discusses requirements of manufacturers of industrial machines who have used hydraulics as the back ground of developing an electrohydraulic control system. Then, it briefly outlines the digital control system mentioned above and gives an application example. Some control algorithms are also discussed for current and future developments.

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Distributed control system offer many advantages compared to centralized system. There is at least two ways to distribute systems; partly and fully. With fully distribution there is some more benefits compared to partly one, but there are some extra demands for the used network protocol and the implementation requires good planning.

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A rule-based expert system shell originally designed for consultative applications has been modified to operate on-line in conjunction with a fast data acquisition system. This paper considers some of the issues involved when considering leakage faults in a control valve/motor open-loop system. Consideration is given to establishing the knowledge base for steady-state operation of the hydraulic system.

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A neural network was applied to adaptive control of a servo system. The neural network was used to learn inverse dynamics of a controlled system. Experimental works were done using an electro-hydraulic servo motor with a digital signal processor. Two types of neural networks were tested. Simulation studies were done to investigate effects of ordering of training data, choice of input signals fed to a neural network, and number of neurons in a hidden layer.

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In the paper, intelligent control of the electrohydraulic proportional cylinder is presented. The model of the valve-controlled unsymmetrical cylinder is griven. The intelligent control method is realized by digital controller. The hardware structure of the controller based on 8098 single-chip microcomputer is presented, the self-learning intelligent control algorithm based on fuzzy logic and control knowledge are given. Simulations and experiments show that the control performance of the proportional cylinder is satisfied.

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The possibility of applying model reference adaptive control to a MIMO electrohydraulic servosystem was investigated in this paper. An adaptive algorithm was developed which requires less a priori knowledge about the transfer matrix while still insuring convergence and stability of the control system. The proposed scheme is based on the estimation of the controller parameters obtained directly from input-output data. Even if the system does not satisfy the strict positive realness as in a non-minimum phase system, it is still possible to obtain asymptotically perfect model following. System simulation results are provided to illustrate the feasibility of the proposed adaptive control scheme.

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This study deals with an HST system which is driven by differential PWM method. In this system, for achieving a linear-motion control, the hydraulic motor in generic HST was replaced with a load cylinder. Two kinds of control algorithm are employed and verified for controlling the cylinder displacement of the modified HST system.

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This paper presents a equivalent flow control system used to crude oil heating furnace. In the system, actuator is a set of electro-hydraulic servo system, and the controller is digital controller in which a Intel 8098 single-chipcomputer is the core. This paper gives a minute description of sampling, dataprocess, control algorithm, and the realizing method about whole system.

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Secondary regulation system of Hydro-Static Transmission (HST) can retrieve and reuse braking energy and potential energy of weight. So the efficiency is higher. The energy saving is very effective for the case of great power and multiple load.
To solve the problem of instability and improve the performance in open loop state for secondary regulation system, general method is to apply double feedback control circuit to it, those are the output feedback (angular velocity or angular) and the position feedback of the variable displacement cylinder of secondary element. Because of the limit of structure, it is difficult to measure the displacement of variable displacement cylinder, further the parameters of the system are time-variant For the above reason, firstly the digital PID control is applied to the system, and then the model reference adaptive control scheme is employed.
The whole control algorithm is realized with IBM-PC/XT computer, and only the output feedback of the secondary ragulation system is required. The experimental results prove that this control scheme can effectively reduce the influence of the time-variant parameters on the control performance, and that the performance is good.

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Noise from fluid power systems is still a severe problem in many applications. During the last decade we have been dealing with fluid power attenuators mainly in systems terminated by different types of valves. However, there have, with varying success, also been a number of attempts with attenuators in hydrostatic transmissions. In order to clarify this noise problem a further look is taken into the phenomena related to the use of attenuators in hydrostatic transmissions.
Previous studies have shown different methods to measure flow ripple. One of the methods, the anechoic termination method, has been the main method for our experimental research, both of fluid power attenuators and of pumps as sources of flow ripple. This method is characterized by the fact that no standing waves will occur in the measurement pipe. To verify the accuracy of this method it is compared with measurements carried out by means of the so-called 2-microphone method. The agreement has turned out to be very good.

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This paper presents analytical analysis and experimental research on the fundamental factors affecting the accurate measurement of fluidborne noise characteristics of fluid power pumps. Particular attention is paid to such factors as fluid transmission line model and parameters affecting pipeline characteristic impedance and propagation coefficient, time-shared characteristic of pressure dual-channel sampling, and high frequency dynamics and locations' measuring accuracies of the pressure sensors used in the measurement. Their influences have been clarified clearly and some effective approaches to eliminate the influences have been proposed.

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In this paper, a CAD expert system for the design of swashplate type axial piston pumps is presented by embedding expert system techniques to the conventional pump CAD system. With the help of a modern and powerful expert system developing tool CLIPS, the design knowledge base and inference engine is constructed. The system has integrated three parts-design, performance simulation and drawing output. It has been verified that the CAD expert system is practical and efficient in the design process.

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The accurate prediction of the cylinder pressure and operating moment of a swash plate type variable delivery axial piston pump is very important for the design of the pump and various hydraulic control systems. The effects of the dynamic characteristics of the swash plate supporting system on the cylinder pressure and the operating moment are investigated. With the result of the investigation and, considering the dynamic characteristics of the swash plate angle supporting system, a new prediction method of the cylinder pressure and the operating moment of the pump is developed. The predicted values show good agreement with the experimental ones.

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A test method based on the use of a simple circuit made by pump-line-load valve has been applied in order to characterize a variable displacement axial piston pump as to its hydraulic noise. The best anechoic conditions achieved, pump fluidborne noise and internal flow losses are provided by source impedance and ideal fl ow ripple evaluation. The influence of constructive parameters as pump port plate geometry and swash plate fastener has been taken into account and various working conditions on acoustic and functional performance examined. The limits of the test method identified, an alternative procedure has been proposed making use of simpler experimental data acquisition and computer programs on purpose worked out.

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This paper describes the application of a delta-operator-based model reference adaptive control scheme to the control of the delivery pressure of a variable capacity swash plate piston pump. It has been found from the simulation results that good model following performance can be achieved. The nonminimum phase problem due to fast sampling can be solved through the use of a deltaoperator-based adaptive control scheme, instead of the usual back shift operator. Disturbance rejection properties are limited by signal saturation in the pump displacement servo system.

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In the present study, the numerical and experimental flow visualization of the jet fl ow issuing from the orifice for repeated spool valve opening and closing are conducted. The discrete-vortex method is employed as the numerical simulation. A two-dimensional model of the spool valve is designed to visualize the jet flow using the hydrogen bubble method. A digital image- processing technique for the image obtained by a CCD camera is employed. The computational results and the experimental ones are compared, and jet angles and the process of jet flow development are considered.

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The valve noise due to cavitation has frequently posed serious problems with the increase of an operating pressure. For poppet valves in different shapes, we have carried out noise tests and numerically simulated oil fl ows under an assumption of non-cavitating conditions in various configurations of the valves by a finite difference method. In addition we have performed the measurements of pressure at two locations in a valve chamber and the flow visualization, employing two-dimensional models. By comparison of measured and computed results, some design criteria can be set up for the low noise valves.

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In this paper the static characteristics of composite 4-way valve composed of two 3-way 2-position high speed on-off valves or four 2-way 2-position ones are studied. Using this kind of control valve, the electrohydraulic position servo system that is controlled by an 8098 single chip computer is developed. Through the study of frequency characteristics of the servo system the methods of analysis and synthesis the system were also introduced. Its correctness is proved by experiment.

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