Actively controlled suspensions have been vigorously studied as to how they can simultaneously satisfy both the ride quality and the driving stability which are contrary properties. In this paper, our main purpose is to control the change of attitude on the car body caused by the pitching vibration mode, using the fabricated vehicle model equipped with the pneumatic servo type active suspension. In the case of applying the optimal control method, it is important how to select the state variable and how to determine the performance criterion. Therefore, we investigated the difference of the control performances for the several kinds of the state variables by some experiments.

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We tried to control pressure of a chamber at some constant uniform pressure by using the electro-pneumatic pressure proportional valve.
If compressed air of the chamber which is closed, is bled by disturbance, or if compressed air of the chamber which is open, is closed by disturbance, both cases we can control it at some constant uniform pressure by using method of feedback control system and learning control.
Next we provide several step inputs of pressure to the chamber. Fluctuation of pressure servo can be made smaller and faster by control based on hysteresis of the elctro-pneumatic pressure proportional valve.

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The paper is concerned with experiments and simulations of the static characteristics of the valve which is a force balance type pneumatic pressure control proportional valve with a nozzle flapper mechanism. It is recognized that the input-output characteristics of the valve has excellent linearity and the characteristics of output pressure versus nozzle flapper clearance look like those of a relay. The effects of the valve parameters on the valve pressure-load flow characteristics are discussed here also. According to the results of the simulations, it is confirmed that the fluid force influencing on the supply valve should be considered.

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A step response relating the displacement to the light intensity in a bimorph typeoptical actuator consisting of two sheets of PLZT elements is analyzed theoretically, and the experimental equations about principal parameters included in the theoretical equation of the step response are derived from the fundamental experiment on the PLZT elements with various sizes. Comparing the analytical result with the experimental result about the step response of an optical actuator manufactured as a trial, each result shows a linear and first order lag factor characteristics and agrees well each other in regard to the finalvalue of the displacement. The time constant in the analysis shows a value 0.44 times as much as that in the experiment. If the cause for the difference is taken into consideration, the dynamic characteristics of a bimorph type optical actuator may be estimated exactly by the analytical result shown in this paper.

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An effective tuning method of fuzzy controllers in the pneumatic servosystem is proposed. Our servosystem consists of the half-bridge circuit type driven by an electro-pneumatic proportional valve. A rule rotational type of fuzzy controller is used in this study. In the fuzzy controller, several parameters should be identified, those are following three ones; a scaling parameter of premise part, a consequent scaling factor of u (control quantity) and a rotational angle of control rule table. We show a simple and effective tuning algorithm of fuzzy controller and discuss the usefulness by simulation and experiments.

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This paper describes an application of electropneumatically operated servomechanism with fuzzy control intelligence to the sophisticated control of clutch engagement for an automated manual transmission. The servomechanism is assembled with a three port pneumatic pressure proportional valve and a position sensed cylinder which controls arelease lever of 25mm stroke within the position preciseness of 0.1mm under a maximum spring load of 2kN. The fuzzy system estimates driver's will only from the accelerator pedal operation. The performance of the system is evaluated from the starting characteristics by using an oil hydraulically operated engine-vehicle simulating test rig with a maximum torque capacity of 400N·Em.

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The paper outlines the growing popularity and acceptance of intelligent control and how it can be applied to fluid power systems. Two popular methods for implementing intelligent control, namely fuzzy set theory and neural networks, are discussed. Current work involving the application of neural networks to air servodrive systems, is introduced.

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Controlled by a microcomputer, a pneumatic system in which several cylinders are connected with each other in series, can realize accurate positioning. When the strokes of the cylinders in some unit vary in a sequence of 2^n-1 where n is an integer number beginning from 1, the positioning can be realized step by step in this unit from 0 to 2^N-1 where N is the number of the cylinders used in the system. Such systems have no feedback control and no electric device around the actuator, so they are usable in various working conditions even the conditions are so hazardous such as in explosive gas or in a strong magnetic field.
This research was carried out experimentally by means of a model system in which four cylinders were used. From the research, the effects of elastic external load on the system have been made clear.

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Intending to explore the possibility of the optical control robot without interposing any electrical signal, pneumatic control robot arm controlled with photofluidic interface was developed.The interface employs a light absorbing nozzle wall in a laminar proportional fluid amplifier. The fluidic output signal of the interface was amplified by a three-stage laminar proportional amplifier gain block. Robot arm has two members and two joints moved by pneumatic rotary actuators. A membrane type booster amplifier with three staged nozzle-flapper values was used to amplify the power of the output signal of the gain block so far as enough to drive the rotary actuators. Two control methods, such as proportional control employing integration compensation and model reference adaptive control were applied and the comparison of the suitability of these control methods was made.

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Selection and estimation of Bondgraph models in simulation process for a developed expert system are discussed. Simple Bondgraph models for hydraulic pipelines are presented and dimensionless transfer matrices for the pipeline models are derived and compared with the distributed parameter models including Bessel functions in frequency domains. A correlation coefficient in frequency domains between the distributed parameter modes and the simple Bondgraph models is introduced into the quantitative estimation of the pipeline models for an index. By introducing the correlation coefficient, selection and estimation of pipeline models make it easy for nonprofessional persons to perform the process to be repeatedly executed as modifying components of a hydraulic circuit.

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The hydraulic modularized modeling method is a new modeling approach for modeling hydraulic components and systems which are oriented to users, that is, engineers. The key to work out the method is related to solve the stiffness problem better and to complete the algorithm for a set ofan implicit state equations.
The authors developed methods called Regional Stiffness-Detection Approach, Stepsize Mode Convertion Approach and Variables Seperation Approach in a certain region where the stiffness problem of the hydraulic system is severe. These mehtods are effective to solve the stiffness with high efficiency. Meanwhile, the algorithm is adoped to solve the implicit equations the Modularized Modeling Method requires. Application in simulating a hydraulic relief valve is given to verify that these methods are feasible and practical.

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The successful application of hydraulic systems depends to a large extent on the skills and experience of the fluid power engineer. The acquisition of these skills, which can only be effectively obtained from appropriate specialised training, is enhanced by the use of practical demonstrations. Although test rigs provide an invaluable aid in the use and application of hydraulic equipment, there are limits to the range of applications that can be demonstrated. The BATHfp computer simulation package is used extensively in system design on the Fluid Power Centre industrial courses. This has been shown to provide considerable benefits in the training of fluid power engineers, particularly in the areas which involve complex concepts that are difficult to understand, by enabling engineers to visualise the system performance. This paper presents the results of case studies that highlight the way in which simulation techniques provide assistance in the training process.

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