Intrinsically, advanced engineering (or technical) ceramics are the optimum material for sea-water hydraulic systems because of their superior mechanical strength, low friction properties, resistance against abrasive, erosive and sliding wear, and corrosion resistance. However, ceramics require a different design philosophy from metallic components, and demand a probabilistic method in the design of structural components together with special attention to the manufacturing and finishing processes. The rationale behind the development of a ceramic axial piston pump for sea-water applications is described below and includes evidence that martensitic stainless steel is intrinsically susceptible to stress corrosion fatigue in such environments.

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New trends in pneumatics are described, with reference to valves, seals, actuators, controls and application.

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“Opportunities of Hydraulics versus Electromechanical Drives”
Electromechanical and hydraulic linear drives (loop structures). Hydraulic linear drives in machine tools, presses, plastic machiness and steel mills. Hydraulic rotary drive (secondary control) versus electrical rotary drive.

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We take the view that mechatronics, as it relates to fluid power, has three levels which we designate as primary, secondary and tertiary. We briefly review the current status of fluid power, hydraulic and pneumatic, and of electronic control of it. We then focus on tertiary-level mechatronic fluid power and the challenges to it being applied successfully.

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This paper deals with education of MSc and PhD students in the engineering areas fluid power and mechatronics. The Technical University of Denmark, DTU has developed a novel education structure and programs for MSc and PhD students adapted to the change and development of technologies. The MSc students may decide to specialise in one of the four classical engineering fields: Mechanical, Electrical, Civil or Chemical Engineering and/or in one of 20 specific profiles of engineering. One of these profiles is Engineering Design and Product Development that gives possibility for specialisation in fluid power system and mechatronics design. Furthermore, the paper describes how synthesis, design and self-learning competency have a very high priority in the teaching and training in industrial enterprises. Projects cover mathematical modelling, simulation, experiments, implementation and prototyping.

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From control point of view there are some serious problems in water hydraulic cylinder drives. Low viscosity of water causes low damping and bad lubrication. Friction is quite high and its behaviour is not very clear. Bulk modulus of water is high and it could cause some problems with short strokes and at the ends of cylinder. The biggest problem is however a lack of good valves. On the market there are some commercial water hydraulic servo and proportional valves, but the specification for them are not very high, especially for proportional valves. In this study experimental tests of the water hydraulic cylinder drive with different valves are presented. The characteristics of different water hydraulic cylinder drives are discussed.

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In order to construct water hydraulic systems for environmental protection, we have developed a pollution-free water hydraulic pump and a water hydraulic servo valve. With a view to secure the same efficiency as oil hydraulic systems, we used a swash plate type axial piston pump, a spool type servo valve, and all parts are lubricated with water which is the hydraulic fluid. The system is made of ceramics, plastics, and so on. The water hydraulic pump has a mechanical efficiency of 94%, a volumetric efficiency of 86%, a power-to-weight ratio 1.0kW/kgf at the pressure of 21MPa, and a rotation speed of 1800min^-1 The water hydraulic servo valve has leakage of under 760cm³/min and a response of 47Hz at a pressure of 21MPa. These components have the same performance as oil hydraulic system.

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In this paper, the water hydraulic cylinder position control system, newly developed by authors, will be discussed. First, the outline of the water hydraulic servovalve and the components for cylinder position control system, as well as the points of control method of the water hydraulic system, are introduced. Next section discuses on the basic performance of the system: a horizontal cylinder position control; synchronizing control for two horizontal cylinders; and a basic performance of synchronizing control device which moves cylinders vertically. The control performance of these water hydraulic servo system is at the same level of that of the oil hydraulic servo system. For the synchronizing control for vertical cylinders, more practical issue, such as the influence of the eccentric load, is discussed.

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A water-hydraulic servo system in which an ann is driven by a single-rod cylinder is constructed. A water-hydraulic servovalve used in the system was obtained by modifying an oil-hydraulic one. Two types of motion control are implemented. One is a motion control based on a torque control using a disturbance torque observer. The other is a motion control only based on a position signal, in which an acceleration controller designed by H^∞ control theory is used. Performance of these control methods are investigated experimentally. From the results, these motion control show better responses and robustness than a conventional PI position control.

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This paper deals with the cavitation occurrence at V-shaped groove of valve plate in an axial piston pump. The cavitating jet from V-shaped groove was visualized using high speed video camera system. The detection of cavitation was also attempted by using AE (acoustic emission) sensors. The results obtained from the tests are as follows:
1) Caviation inception/desinence at V-shaped groove was visualized under actual pump operation at the operating pressure of 3MPa.
2) It was proved that cavitation inception and desinence are detectable by AE sensors.

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The purpose of this research is to get the pressure-flow characteristics of V-notch machined on the valve plate of hydraulic pump and motor.
The changes of discharge coefficient are investigated with a basic test device by using the shapes of notch, the openings, the direction of flow, the pressure difference, the back pressure and the like as a parameter. The occurrence of cavitation is observed by means of a transparent apparatus to consider the relation with the discharge coefficient.

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Variable displacement motors fed by an impressed pressure through a pressure net require a closed loop control for stable operation.
The presented paper focuses recent research results of the speed controlled motor [9]. The linear control theory allows an easy design of the controller. In real applications operating points will vary due to changing pressures in the pressure net as Nvel 1 as changing inertias of the load. It is shown how these changes affect the performance of the speed control.
Suitable identification for the inertia is suggested and performance results by adaption techniques are demonstrated. such as on-line parameter adaption. fuzzy parameter adaption and fuzzy control.

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In this paper, we revealed a factor causing the remarkably large amplitude delivery-pressure oscillation with quite low frequency, occurring often in pressure-compensated variable displacement vane pumps under deadhead conditions. It was found experimentally and theoretically that the pump instability originates in the fact that the gradient, ∂A/∂E is significantly negative, where A is time-averaged effective area for the internal pressure compensation force and E is the cam ring eccentricity. Also this phenomenon is regarded as same as surging of the turbo-fan.

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In this paper, we propose a method of noise reduction for a variable displacement axial piston pump of even number of cylinders with two swash angle control cylinders. In the 8-piston pump, two exciting forces act on the upper and lower part of the swash plate at the same time when two of the rota cylinders come to the top and the bottom center respectively. To compensate the exciting moment and reduce the pump noise, the pressure in the upper side rota cylinder is lead to the lower control cylinder, and vice versa, for a short time through small orifices on the valve plate. Determining the orifice diameters properly, the compensating moment could be obtained and the noise level was reduced to 64.5dB from 71 dB under the condition of the delivery pressure of 6.9 MPa and the flow rate of 25l/min.

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Customers have always been increasing their desires of the capability of products and machinery. They want improved productivity and efficiency. The demands and requirements often focus on extentions of functionallity, faster response, operation capability, man-machine interface, robustness, reliability and safety in use. Today's information technology can offer both software and hardware for the engineering solutions which could satisfy such demands, requirements and regulations. This paper deals with how transputers can be applied for fast controllers for hydraulic actuator systems. A general Transputer-based Control System including a Data Acquisition Transputer Subsystem is presented. As an application case a developed mechatronic test facility consisting of a fast hydraulic robot with the Transputer-based Control System is presented. Some experimental path-tracking results with adaptive control algorithms are presented and discussed. The results confirm that transputers have significant advantages for intelligent control of actuator systems and robots for high speed and precision tasks.

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A smart digital controller for pneumatic servo positioning axis is discussed in this paper. The controller is based on a non-linear state feedback control algorithm and it has much intelligence. Through close theoretical analysis and a large amount of experiments a concept is developed, which lets the controller itself find the optimal control parameterset according to the system data given quite easily by a user. With the controller, satisfactory characteristics can always be obtained even for those pneumatic servo axes with lage variations in dimension or working under some extreme special conditions, e. g. for cylinder length from 50mm to 3000mm, diameter from 16mm to 125mm or mass load from 0.5 KG to 1500 KG.
In this paper, theories for modelling and design of the controller are given and the principles of the non-linear state feedback strategy are discussed. Some intelligent algorithms employed in the controller to further improve the dynamic and static performances of a pneumatic servo positioning axis are also reported. Finally, a brief description of some additional important features of the controller and several practical applications are introduced.

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This study is an attempt to realize a versatile robot hand that can treat a sheet of paper as example of object that is hard to grasping. For versatile hand, it is desirable that the fingers of hand have no special mechanism to separate and grasp the paper, such as human, and the grasped paper must not be damaged. In order to realize human-like soft action to separate and grasp a paper without damage, the robot hand actuated by pneumatic cylinders is proposed in this report. As a first step of realizing a automatically handling of paper craft, for example, wrapping work etc., the method of separating a paper by using robot hand which have no special mechanism for separating is presented. The proposed robot hand consists of three fingers and a pair of them is used to separate a paper from stack. To separate the top of paper in stack, the pair softly touches a surface of paper and slides it.
The separated paper is grasped by another pair of fingers, in this report. All the fingers need not special structure, therefore, this grasping method is suitable for the versatile hand of various purpose, although experimental tests are terminated when the grasping is done.

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A flexible microactuator, FMA, has potential to reproduce human friendly actuation based on its smoothness in motion. A trot-walking-robot with four FMAs moves softly like an animal. The FMAs are energized by compressed air and its motion is controlled by a combination of switching valves. The valve control expands degrees of freedom of the walking pattern. The FMA-animal has issues on walking speed and stiffness. The speed is increased by shortening the pneumatic tube length, and the stiffness is improved by using elliptic-sectional-shaped FMA. FMA-animal with 70mm in foot-length walks in the speed range from 50 to 250 cm/min under the operating pressure from 0.15 to 0.35 MPaG.

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A laboratory demonstration system has been made which enables a signal carried by an optical fibre to control the operation of either a pneumatic actuator or a fluidic flow control valve. Apart from the actuator, all functions are implemented by no-moving-part fluidic amplifiers. Notably this includes the direct fluidic detection of the signal which is done using a commercially available sub-unit originally developed in the USA for defence applications. The system demonstrates the integration of signal-fluidics and power fluidics and shows how remote control can be implemented without the use of electrical signalling or power at the site of the actuator. Signals are produced by a laser diode. Control functions are the operation of a standard 100 mm bore butterfly valve or the 4-to-1 modulation or diversion of airflow by a switched vortex valve.

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The Pneumatic BTA (Bourdon Tube Actuator) is a sticksliplew actuator which utilize a pair of spiral bourdon tubes as a functional element and obtains displacement by air pres.sure. Compared with an electric motor and so on, the BTA is smaller and lighter; moreover, it generates a high torque and accurate positioning.
Before now Alias been difficult for a cylindrical type pneumatic actuator to control accurate positioning because of sliding friction. Our laboratory developed a three-axis driving robot with 4-bar linkage utilizing a pneumatic BTA. We obtained owillating of ± 15 degrees and minimum sensitivity 0.6 × 10^-2 degree. A pneumatic BTA robot system makes posble minute action and accurate positioning.

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In this paper we propose a method for the analytical study and the definition of schemes of vehicular passive suspensions that use pneumatic devices as springs and dampers. The article carefully describes the mathematical modeling and allows an evaluation of the effect of the different physical parameters on the performances of the suspension. The study has been done in the frequency domain and in the time domain, for a more complete evaluation of the performances. It is defined an optimal solution able to give an improving behaviour in comparison with the traditional solutions of suspension.

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A pneumatic servo system has been expected to be applied to contact tasks because of the ability of collision force absorption, delicate force control and so on due to air compressibility. However, the high nonlinearity and friction in the pneumatic system make a satisfactory servo-type force control not easy. The purpose of this study is to develop a pneumatic servo-type force control system which can be applied to the system with unknown and variable parameters and environments by using a neural network controller with the capability of learning and adaptability. The controller is installed in parallel with an usual linear controller. Some experiments confirm that the neural network controller is one of effective approaches to realize the advanced force control of a pneumatic servo system.

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In tracking or position control of an electropneumatic servodrive modelling errors like the leakage mass flow rates and the gravity torque or also the dry friction, constitute a serious constraint when designing a control law. We describe in this paper a robust control approach based upon a local change of coordinates and a nonlinear sliding mode control synthesis. An integral surface is used and this allows us to overcome the use of an accelerometer. Experimental tracking results are then related.

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The natural frequency and damping are especially low in most applications of pneumatic position servos. However the steady state and dynamic specifications are demanding, because pneumatic position servos have to compete with hydraulic and electric servo systems. The only way to increase the effective natural frequency and damping is to use a controller which can move the poles of the system so that really remarkable improvements can be achieved. The state controller is the most often used controller in pneumatic position and also velocity servos. The state controller is an effective controller in a position servo system. However in the practical realization of the state controller there are some drawbacks including low robustness and the requirement of a high resolution position transducer. In this paper some alternative controllers are studied and compared with the state controller.

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Recently, pneumatic cylinders have become favorite actuators utilized as Z axis (vertical axis) actuators of indstrial robots and actuators for lifting or bringing down parts. Two degrees of freedom P1 controller is applied to the system in order to many points positioning control.
From some simulations and experiments, it is confirmed that the proposed control system is effective to improve the overshoot or undershoot and settling time for many points positioning [1], [2].

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Air powered servos are seldom explored for commercial control applications. They are mainly employed with programmable logic controllers in applications where positioning repeatability is of no importance. This paper examines the repeatability of an air powered load traverser under closed loop control. A set of controller gains is first determined experimentally based upon the desired response characteristics under various loading conditions. The repeatability of the control system is then determined statistically. The repeatability, under different start-stop positions and loading conditions is found to be less than ±0.3 mm. This value is within typical industries' requirement of ±1 mm and hence the system has great potential in many loading handling applications.

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This paper considers the application of SMC to the control of an axial displacement piston pump. The objective of the control is to maintain pump pressure independent of varying load or system parameter changes. A DC motor directly attached to the pump swash plate is used to interface the computer control signal to the pump. The results of a theoretical and experimental study are presented and show that a modified SMC algorithm can be used to provide improved dynamic and steady state performance when compared to a standard PID controller. Ripple due to “chatter” of the SMC around its steady state conditions is apparent which requires additional examination.

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Robust control of a closed-loop pressure control system is investigated in this paper. Dynamics of a pipeline which connects a control valve and an actuator affect the closed-100p system stability. A simple reduced-Order model of pipeline dynamics is preferable for control system design. Based on evaluation of modeling error of the reduced-order model by means of a finite-element model, an H∞ controller is designed. An experiment on closed-loop pressure control has been carried out, to investigate performance of the H∞ controller and to illustrate the importance of evaluating modeling error of pipeline dynamics.

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A proportional reducing valve has heen applied to an automatic transmission to control shift operation. The control system must be designed as cL robust control system considering modeling error caused by changes in characteristics of the valve and a frictional coefficient. In this study, a brake mechanisml of an automatic transmission is considered as a controlled plant. Two-degree of freedom control of rotating speed is studied in which the modeling error is took into account. A. feedback controller is designed based on μ synthesis. Adding a feedforward controller, a two-degree of freedom control system is constructed. The control system is examined experimentally using cl commercial proportional reducing valve. It is demonstrated that shift operation can be precisely controlled by the control system under the fluctuating factors.

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This study deals with a self-tuning fuzzy controller (STFC) when it is applied to an electro-hydraulic servo system. The STFC has a hierarchic structure consisting of an algorithm being identical to a fuzzy controller at the lower loop, and a tuning algorithm accommodating the performance evaluation and parameter modification function at the upper loop. As an algorithm for tuning at the upper loop, another fuzzy reasoning is adopted for constructing a fuzzy selftuner. The whole procedure of the STFC is repeatedly performed until an acceptable level of control is achieved. The basic functions of the STFC can be summarized as follows:(a) to issue appropriate control action while evaluating the performance, (b) to modify the control action based on the evaluation. It is verified by experiment and digital simulation that the STFC developed in this study is useful and effective for the control of electro-hydraulic servo system.

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In this research work, we are studying the accurate trajectory control at the end of a 6-axes hydraulic manipulator regarding r obustness with respecto changes in the system parameters that has unstable characteristics. In particular, interference in the var ious axes becomes important for improving the accurate trajectory control, and disturbance estimation and compensation by an observer are applied and evaluated by independent servo-system for each joint. As a result, it was verified by experimenthat robust, stable accurate trajectory control can always be achieved against fluctuations in the moment of inertia caused by changes in the attitude of the manipulator, and against the nonlinear disturbances, such as axis interference, that are characteristics of a multi-jointed arm.

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The DSP (digital signal processor) and the feedforward compensation called ZPETC (zero phase error tracking control) are applied to an electrohydraulic servo system with a nonsymmetrical cylinder, and frequency responses of the system are greatly improved. ZPETC is a control algorithm which renders the transfer function between an input and an actual output close to unity. To use this algorithm, it is assumed that the controlled system is linear. However the relationship between load pressure and flow rate at the servo valve is highly nonlinear. Another nonlinear factor is added when the cylinder is nonsymmetrical. Therefore these nonlinearities should be removed. The nonlinearity of the servo valve is compensated using the detected load pressure, and the effect of nonsymmetrical cylinder is compensated using the detected sign of the input. DSP performs the calculations for ZPETC and for linearization of the system. The effect of improving the frequency responses of the system by this digital signal processing technique is investigated.

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In this paper, a self-learning control stratagem based on digital control is put forward to compensate the variable dead-zone of electro-hydraulic proportional direction valves. Experiments show that the positioning accuracy together with the anti-disturbance ability and the steadiness of the electro-hydraulic proportional positioning system is improved considerably. Being used in real-time control system, the application of electro-hydraulic proportional system is widened in the field of high accurate positioning.

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The purpose of this study is to combine the good adaptability of PWM control to micro-processor with the adaptability of two-way cartridge valve to high power-level hydraulic systems. In this study, a special cartridge valve, called active cartridge valve, is used. The valve body is incorporated with a piston and the position of the piston, i.e. the opening of the valve, is controlled by the high speed on-off solenoid valve in the pilot circuit using PWM method. As a result the flow rate through the cartridge valve can be controlled by the high speed on-off solenoid valve. The effects of the design parameters on the characteristics of flow control cartridge valve using PWM metho are investigated.

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Results are presented from a study of leakage losses from a position control systemand the resulting knowledge that may be incorporated into an on-line expert system for fault diagnosis. The use of aminimum number of sensors results in leakage and position error data that have limitations for multiple-faultsituations. It is then shown how the application of an artificial neural network can give additional confidence to a fault assertion, and results are shown for a number of leakage conditions.

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In this paper, we investigate the usefulness of active stabilizing fins on ship pitching reduction under varying forward speeds, in varying wave lengths. A 4-meter self-propelled ship model and an electrohydraulically driven stabilizing fin system are used as our experimental system. Pitch angles, pitch rates, and ship forward speeds are measured and feedback to a fuzzy logic controller to calculate the deflection angle of the stabilizing fins. The effects of fin nonlinearity on achievable pitch reduction performance are discussed. It is shown that desired pitch response can only be achieved when the fin is operated in its linear region. The overall dynamic response of the ship approaches her open loop behavior when the degree of nonlinearity is high. This simple analysis to the pitch stablizing system provides basic information to ship designers. Experimental results validate this design guideline.

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In-pipe mobile micromachines have many applications including micro maintenance robots for nuclear reactors and are expected to be realized in the near future. For practical micromachines, the authors have proposed the bellows microactuator using fluid power with high power density. In this paper, an inchworm type in-pipe mobile micromachine which is traversable branched pipes using the bellows microactuators is fabricated and the performance is examined. Firstly, performance of displacement magnification mechanisms significant for micromachines is theoretically investigated and the effectiveness of a pulley type mechanism is proved. Secondly, for structure of an in-pipe mobile micromachine, a bending and propelling mechanism with 1-bending DOF using pulley type mechanisms is proposed and the traveling sequence in branched pipes is theoretically investigated. Finally, an in-pipe mobile machine with 25mm in diameter is fabricated and the traveling experiments are conducted. It is clarified that the traveling velocity in a straight pipe is increased and the fabricated machine is able to traverse a Y-shaped pipe.

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With the development of science and the improvement of technology, the industrial requirement for automation is more and more eager. The application of hydraulics and pneumatics is one of the most important parts of automation. Because of the airtightness of the pneumatic executors, using lubricator is the only way to lubricate them. Under the stable air flow condition, it has been found that quantity of oil delivered by the lubricator decreases. This leads to the damage of the executors. The phenomenon of reduction of fluid discharge often occurs in engineering when fluid flows through a narrow slit as time goes on. The mechanism and law of this phenomenon must be studied so as to solve this problem. In this paper, an experimental device on needle valve is designed, and a data-acquisition software is developed. A great many experiments have been done It has been discovered that two things account for the occurrence: adsorption and deposit of dirt. Some preliminary schemes to solve this problem are put forward in addition.

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Artificial rubber muscles were controlled by fuzzy reasoning. Based on measurement of characteristics of artificial rubber muscles, the authors designed fuzzy set, fuzzy rule, and reasoning method in fuzzy reasoning. Firstly, they controlled displacement of an artificial rubber muscle by air pressure under tensile load. Secondly, they made a one-link arm robot manipulator that had push-pull mechanism composed of two artificial rubber muscles. They succeeded in controlling the arm angle of the manipulator with fuzzy reasoning.

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A pneumatic diaphragm motor controlled by two PWM solenoid valves are studied. First, the characteristics of the PWM solenoid valve is investigated and a simplified mathematical model of the valve is presented. Second, a PWM control law is synthesized by considering the effects of the valve characteristics and the asymmetrical flowcharacteristics between the charging process and the discharging process of the system. The main parameters thatinfluences the performance of the system are analyzed and their values are optimized experimentally. At last, thefrequency response and the stiffness characteristics of the proposed system are obtained and the results show that theperformance of the proposed system is better than the traditional one. These experiments verify the theoretical designwork, and indicate that the PWM controlled pneumatic diaphragm motor is feasible for practical use.

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We have proposed a simple method to measure the flow rate of compressible fluids using an isothermaichamber. An isothermal chamber is a chamber which the steel wool is stuffed and can almost, realize isothermal condition. Therefore, the instantaneous flow rate could be measured only from the pressure response using the stateequation of gas. In this study, we propose methods for the characteristics measurement of pneumatic elementsusing this chamber. Specifically, the method for the flow characteristic measurement of regulators and valves, and for the dynamic characteristic measurement of servo valves is proposed. We confirmed effectiveness a, ndsimplicity of the proposed method by comparing the measured results obtained by proposed methods with themethods defined in the JIS and the ISO standards.

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To drive a pneumatic cylinder, meter-out circuit is used in many cases, since time to move the piston is constanteven if the load is changed. That is, the meter-out restriction method realized velocity control. However thisprinciple of velocity control has not been explained sufficiently. The purpose of this study is to make clear thevelocity control mechanism. In order to clarify this mechanism, nondimensional equations and their responses are presented. Consequently six parameters governing the cylinder response are obtained. As a result, by drawing theblock diagram of cylinder system, it is found that the compliance of a cylinder makes the feed back loop in cylinder velocity and the flow characteristics of restriction in choking compensates the constant velocity for changing a loadforce.

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In pneumatic proximity sensors of cone jet type, a high supply pressure is usually required for obtaining high output signal. Therefore, a large amount of air is consumed in this type ofsensors. We have proposed the sensing system that can be much more improved by giving swirl to the main jet of the previously reported sensing system, which is combined a proximity sensor with laminar proportional amplifiers for the purpose of lowering supply pressure and reducingair consumptions. Consequently, we have found the new sensing system made it possible to measure the gaps with high accuracy, and to detect even very light weight objects.

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Functional safety and live time of pneumatic components are considerably influenced by dynamic seals. To optimize the tribological systems, appropriate experimental methods are required. The testing method described uses a dyingout process generated by the unilateral load of a spring- mass - system. During one process of movement, various conditions of systems are passed as well as typical courses and characteristics of frictional force are provided. Suitability and flexibility of this simple, unsteady method is proved taking investigations of cylinders and valves as an example.

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In the paper, instead of using the expensive servo valves, three cheap high speed slenoid valves were applied and a fuzzy PWM controller was designed to control the linear and rotational positions of a pneumatic robot cylinder. The modified differential PWM method is proposed to eliminate the dead zone and improve the nonlinear characteristics of the relationships between the pressure difference of the cylinder and the duty ratio. The experimental results have shown that the servo pneumatic system can have both the good performance and the low cost solenoid valves with the proposed fuzzy PWM controller.

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This paper discusses automation of a small-scale hydraulic shovel and its trajectory control. To move an end-effector (grinder) along a desired trajectory, the controller uses PID control and internal pressure of hydraulic cylinder. To apply PID control to the present hydraulic system, the system model is derived physically and its system parameters are obtained by actual measurement. To show the effectiveness of the PID controller and propriety of system model, the computer simulations and experiments are performed. These results in simulations and experiments indicate that the PID trajectory control of robotic deburring by hydraulic shovel is effective.

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The authors proposed a New Wave Power Converter:-New Pendulor. The Pendulor was so considered that the system should be much simplified in order to save the investment. One of the key technologies for it was a special pump having a large displacement.
In this case, D_p-45, 900 cm³/rev was taken for the pump of a Test Pendulor and a rotary vane type was selected through a comparing studies on large pumps.
Concerning the rotary vane pump, optimization, design procedure, manufacturing, characteristics----have been studied.
The pump can improve not only the cost efficiency but also robustness though. the seal mechanism of the pump must be studied more to reduce internal leakage.

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The paper addresses an automatic procedure to define the size (i.e. displacement) of the main units within a hydrostatic transmission for mobile vehicle applications. It is developed for one pump and one or more motor, and starts from a limited number of specifications: the rated engine power and speed, the overall power ratio, the number of motors, and the choice of fixed or variable displacement motor (s). Numerical results are given over a practical range of input data, and additional constraints are discussed which come from the vehicle locomotion.

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To increase performance in a hydrostatic transmission using sequence-controlled motors one of the motors is disconnected from the other transmission at high vehicle velocities and connected again when torque demand increases. If the reconnection procedure is handled using secondary control this must be taken under extra care. A method to investigate the reconnection procedure in the early state is to use hardware-in-the-loop (HWIL) simulation. The reconnecting motor is then acting as the hardware while the rest of the system, the main transmission, is real-time-simulated. As interface between hardware and simulation a high-response servovalve is used. This acts both as a controller for the pressure upstream of the hardware, and as a flow measure orifice to serve the simulation model with input data. This paper deals with the test method and results from the HWIL simulation described above. The results are partly used for verifications of earlier simulations.

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Theoretical analysis of the steady state performance of a load sensing hydraulic flow control valve, having priority to primary circuit and an excess flow secondary outlet, is presented in this paper. Basic control system feature of such a valve with fixed displacement pump is considered. A constant flow with a priority to a primary circuit occurs irrespective of the amount of load pressure, whenever a demand is created by opening a control orifice. Analysis is carried out for variable area control orifice to find out the optimal operating conditions and parametric values. The effect of flow forces on the spool equilibrium is also investigated. In some critical situations flows through both the ports occur which are also studied. Some results are verified experimentally. Analysis helps also as a design guideline.

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