Pneumatic actuators are widely used as low cost actuators, but there is difficulty in controlling the precise position with the pneumatic actuator. The main reasons for this are the high compressibility of air in the cylinder and nonlinear friction of the piston rods. We made use of a dither so as to decrease the nonlinear characteristics of friction and disturbance observer to give more robustness to the change in loads to the position control of the actuators. We realized the precise position control of the pneumatic lifters which consisted of a load table and four pneumatic actuators.

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In this paper, we have proposed a bi-directional oscillatory flow rate measurement by using a drag plate-type drag force flowmeter (DPFM). We have already proposed an unsteady flow rate measurement method by using the drag platetype drag force flowmeter. To clarify the dynamic characteristics between the flow rate and the force on the circular drag plate, and using simplified dynamic mathematical modelling of the DPFM, we could confirmed that real time unsteady flow rate measurement could be realized with sufficient accuracy up to a frequency of 400 Hz which is the resonant frequency of the beam system.
In this study, we have investigated the measuring bi-directional oscillatory flow rate measurements with DPFM. In this report, as a comparing method, we employed the piston cylinder-type flow rate measurement method. In this method, we added a regulating component to the piston cylinder-type and controlled the chamber pressure so as to reduce the measurement error resulting from the internal leakage. Results obtained are as follows. As compared the flow rate of the DPFM with that of the piston cylinder-type, first, the gain and phase characteristics of the DPFM were in good agreement and within ± 0.5dB and ± 5°with the piston cylinder-type over a frequency range of 50 Hz.

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Pipes are indispensable for hydraulic systems as an element transporting hydraulic power between two components. Pipes often play an important role regarding pressure fluctuations, which are used to be analyzed by the method of characteristics. However, the methods are not often used to analyze the dynamic behavior of hydraulic systems.
On the other hand, bondgraphs, which represents systems from the viewpoint of energy flow conservation, are capable of simulating the dynamic behavior of systems being made up of hydraulic and mechanical components. It is easy to construct system bondgraphs model of an complicated oil-hydraulic system consisting of many elements. The state space equations are derived from the system model by eliminating the algebraic variables from characteristic functions on all elements and algebraic functions on all junctions. This method has been designed to handle hydraulic systems as well as providing an analysis of the dynamic characteristics.
The purpose of this study is to investigate the precision of bondgraphs regarding pressure fluctuations in a straight and joined pipes. The calculated results by bondgraphs method were compared with the experimental results and with the numerical ones calculated by the method of characteristics. As a result, it became clear that the results by the bondgraphs method agreed well with the other results.

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Pneumatic cylinders may not achieve steady motion in applications where a low velocity is required due to the stick-slip effect. However, an effective means to assess the possibility of stick-slip occurrence in pneumatic cylinders has not been reported. Despite friction characteristics is an important parameter on stick-slip motion, there are only few studies on friction force at low velocities and actual comparisons of experimental and simulation results for stick-slip motion have not been shown. As a result, it is still unknown in what extent stick-slip motion can be described by simulation and under what conditions stick-slip may occur.
In this first report, stick-slip motion in pneumatic cylinders is studied. Friction force is measured and modeled considering the Stribeck effect. Simulation results show that stick-slip motion can be described with good accuracy. The results of this first report will be used to study the occurrence conditions in the second report.

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