This study deals with a master-slave system of a tele-operated construction robot. The system consists of an excavator as the construction robot and two joysticks for operating the robot from a remote place. A fork glove is attached to the front end of the excavator as a hand for grasping task objects. The slave and the master in this system correspond to, respectively, the fork glove and the joysticks controlled by an operator. In such a remote control system, the operator needs to feel a realistic sense of task force, which is brought about from a feedback force from the fork glove. In order to attain an effective feedback of the task force, in the previous report of this study, a control method called a variable-gain symmetric-position was proposed. After that, however, a weak point was found in this method. Namely, the operator was not able to feel a realistic sense of the task force when he was grasping a soft object at a comparatively slow velocity. In the present report, therefore, for overcoming this problem, an improved method of control is proposed.

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In this paper an alternative method for obtaining the sonic conductance and the critical pressure ratio is presented. The proposed method uses an isothermal chamber that can almost realize isothermal condition by stuffing metal wire in the chamber to produce a larger heat transfer area and heat transfer coefficient. Using this chamber, the sonic conductance and the critical pressure ratio is obtained by measuring only pressure in the chamber. And the proposed method is completed in a shorter time and consumes less energy than the ISO 6358 procedure. Furthermore, the authors have investigated the effect of supply pressure change and temperature change in the isothermal chamber. It became clear from the experiment that the proposed method can measure the sonic conductance within 3% error margin and the temperature change counteracts the effects of the supply pressure change.

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To obtain fundamental design data on bearing/seal parts made of PEEK and stainless steel, friction characteristics were tested by a pin-on-disc machine. The test parameters were mean load pressure, sliding speed, water temperature, water properties, and surface roughness. Based on the test results, a mixed lubrication model, which is applicable to rubbing parts in hydraulic equipment, was proposed.

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In the previous paper, the authors proposed a new simulation technique called the “system modal approximation” method (SMA method for short) for fluid transients in compound pipeline systems, which was able to predict fast and accurately, and verified superiority of this technique to other existing methods. There, however, detailed considerations were limited to the case whose transfer functions of output/input were of the form of pressure/pressure and flow-rate/flow-rate. This paper enhances the analytical functions of the SMA method so as to be widely applicable to compound pipeline systems with various kinds of boundary conditions. Specifically, the calculation methods of time response of the wanted output variables at any points are newly proposed for the case (i) whose transfer functions of output/input are of the form of pressure/flow-rate and flow-rate/pressure, and (ii) whose boundary conditions are given by the relation between pressure and flow-rate. For fluid transients in three kinds of compound pipeline systems, simulation results based on the methods mentioned above are compared with both the solutions from the method of characteristics and experimental results, and then the usefulness of the generalized SMA method is verified.

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