Hydraulics & Pneumatics 

About: Hydraulics & Pneumatics is an academic journal. The journal publishes majorly in the area(s): Pneumatic cylinder & Hydraulic machinery. It has an ISSN identifier of 0018-814X. Over the lifetime, 285 publications have been published receiving 656 citations. The journal is also known as: hydrodynamics.

PWM-digital control of hydraulic actuator utilizing 2-way solenoid valves

Abstract: The objet of this study was to propose a mathematical model for the PWM-actuator system, to control digitally each types of hydraulic systems. This PWM hydraulic actuator system was made up of two 2-way solenoid valves operated in the PWM (pulse width modulation)-digital mode by a personal computer, a hydraulic actuator and pipes. The static and dynamic characteristics of the system were verified in comparison with experimental results, simulating numerically based on the proposed model. Main results were as follows: Representing the relationship between the valve displacement and the input voltage to the solenoid as a linear function with time lage existing between the input and output signals of the valves, the behavior of the on/off action of the solenoid valves were rationally described; hydraulic transient in the pipes connected with the solenoid valve could not be ignored while the valve were operated with high speed on/off action. It is necessary to attach importance to the natural frequency decreasing caused by existing of the element of pipes in the system on the view point of the resonance oscillation at PWM-digital control system. 8 references, 8 figures, 2 tables.

Model reference adaptive control for a pneumatic cylinder servo system.

Abstract: It seems to be useful to apply the model reference adaptive control (MRAC) method for pneumatic servo systems. Since pneumatic servo systems are easily effected by the change in system parameters such as the load mass or supply pressure, etc.The MRAC method for the pneumatic cylinder position servo system using a diaphragm-type electro-pneumatic converter is proposed in this paper. The converter acts with a very short lag time and has a simple first order transfer function. So the total transfer function of the servo system can be represented to the lower order system and this is suitable for the execution of MRAC.The experimental tests were carried out by using a 200-mm stroke and 40-mm bore single rod-type air cylinder. The reference model was set to the second order system which has an optimal dumping factor. Also, the response of the MRAC was tested under the various input conditions such as a rectangular signal, sinusoidal signal or triangular signal was yielded, respectively.As a result, the accommodations for the change in load mass, supply pressure or magnification of servo amplifier could be clarified.

Measurement Method for the Effective Area using an Isothermal Chamber.

Abstract: The flow characteristics of valves and restrictions are often represented by the effective area. The effective area is often measured using a method defined in the ISO standards. The method is to measure the flow rate and differential pressure between the tested valve. Therefore, the accuracy of the method depends to a great extent on the accuracy of the flow meter.On the other hand, a more simplified method to measure the effective area is defined in the JIS standards. This method discharges air from the chamber through the tested valve, and the effective area is measured indirectly from the pressure response of the air in th chamber. The method calculates the effective area, assuming the adiabatic conditions during discharge. Though, even in-a sudden discharge, the heat is transferred into the chamber. Therefore, this causes a measurement error.In this study, the relation between the temperature change of the air and the measurement error of the JIS method owing to the chamber volume and the length of the pipeline are examined. Then, it became clear that by stuffing the steel wool into the chamber, the transfer area and heat transfer coefficient could be made larger and an isothermal condition could almost be realized. This chamber is called an “Isothermal chamber”. The method to measure the effective area has been proposed using an isothermal chamber. The proposed method can lessen the measurement error as a result of the chamber volume and length of the pipeline compared with the JIS method.