To drive a pneumatic cylinder the meter-out circuit is ordinarily utilized. However up to now, dynamic characteristics of cylinder system have not been analyzed sufficiently. Therefore it is not verified whether the design method of a cylinder system, which determines the cylinder size from the load force, is theoretically correct.
In this study responses of pneumatic cylinder system driven by a meter-out circuit are analyzed in order to clarify its dynamic characteristics. For the analysis, nondimensional equations are derived from fundamental equations on the cylinder response considering the energy equation and the motion equation including the packing friction. Eight nondimensional parameters deciding the cylinder dynamics are found. Simulation results of nondimensional cylinder step responses are shown changing each nondimensional parameter and relations between the parameter and changes of cylinder responses are explained analytically using block diagram. It is also recognized that parameters excepting nondimensionalized load force have no effect on the time needed to move the piston, so that the cylinder design method is reasonable. Through this study the dynamic characteristics clarified made clear and available knowledge to design a pneumatic system is obtained.

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The precise intra-stroke stopping of a pneumatic cylinder is considered extremely dificult because of the time lag due to the compressibility of air and delay of the control valves. Our previous study using a labyrinth-type seal was able to precisely control both the desired intra-stroke stopping and position holding under a time-variant loading condition to a precision of 1 μm. In this study, two types of new control methods, pressure switching and re-positioning, for sub-micron intra-stroke stopping were developed. By using these methods, intra-stroke stopping of a cylinder with a precision of 0.1μm at high-speed moving could be achieved.

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This paper presents a theoretical study of the delivery flow ripple produced by a swash plate type hydraulic piston pump for the purpose of developing a computer simulation program capable of predicting the pump source flow ripple accurately at the design stage. Particular attention has been paid to the development of the theoretical model by clarifing quantitatively the design influences of key parts of valve plate such as relief groove and pre-compression/expansion, air bubbles released during the inlet phase and fluid inertia effect in the unsteady flow in the relief groove and cylinder on the pump delivery flow ripple. The theoretical model of delivery flow ripple is improved and validated by comparison with many experimental results obtained by the author's devised “2 pressures/2 systems” method over wide test conditions and by the experiment-based estimation of unknown parameters such as the discharge coefficient, fluid bulk modulus, void fraction, etc. impossible to find theoretically. The pump source impedance is also measured by the above method to obtain the pump's real flow ripple from the measured apparent value in the so-called standard “Norton” model. The simulated results from the present theoretical model agree with the experimental results with sufficient accuracy for practical use up to around the 10th harmonic (up to around 3 kHz) over a wide range of operating conditions.

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Recently, the authors have proposed a simulation method for predicting transient responses of fluid transmission lines (rigid and viscoelastic lines). The purpose of this study is to confirm the availability of a simulation method when it is applied to fluid lines connected to pumps. The fluid lines dealt with here are composed of flexible hoses (a fluid viscoelastic line) and rigid lines. As a method for simulating transient responses for fluid lines, we adopted a technique for formulating rational polynomial approximations for transfer matrix elements of fluid lines. In this study, each fluid line system connected to two kinds of pumps, consisting of a vane pump and axial piston pump, was investigated. The waveforms of the pressure pulsation induced in these systems are calculated using simulation. The results obtained are compared with the experimental results. It may be concluded that the simulation method adopted in this study can be useful for predicting the pressure pulsation induced in these systems.

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