Reasonable design methods of the optimum dimensions of the bearing/seal parts of hydraulic equipment are presented. The minimum power loss, minimum dimensions (maximum load carrying capacity), and maximum moment-stiffness, as well as the maximum stiffness, are established as the optimum conditions. In this study, we have used circular hydrostatic bearings as the bearing/seal parts. The basic equations considering the effects of the dynamic supply pressure, eccentric dynamic load, and elastic deformation are derived. The representative design parameters are the radius of the bearing/seal parts, pocket radius ratio, and aspect ratio of the restrictor. In this report, we discuss the optimum analytical solutions for the hydrostatic thrust bearings with the capillary restrictor under steady concentric loads. The conditions of the minimum power loss, maximum load carrying capacity, and maximum stiffness correspond to that the ratio of power losses of leakage to friction is 1/3, the pocket radius is equal to the equivalent radius of load-area, and the pocket pressure ratio is 2/3, respectively. The optimum design methods based on the minimum power loss and minimum dimensions considering the degree of freedom of design are presented. From the maximum moment-stiffness, it shows that the optimum pocket pressure ratio is given by 5/6, and this is a favorable design method for a miniaturization of the bearing/seal parts.

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Performance of the optimized bearing/seal parts of hydraulic equipment is investigated numerically. The unsteady operating conditions, physical properties of fluids, elastic deformation, and eccentric load are considered. The optimum conditions discussed in this study are the minimum power loss, minimum dimensions, maximum stiffness, and maximum moment-stiffness. The optimum dimensions are given by the maximum stiffness and maximum moment-stiffness based on the maximum load carrying capacity. For the ideally hydrostatic-balanced bearing/seal parts under concentric loads, the required stiffness is small. In the case of the high pressure operation or low viscous fluids, the radius of a restrictor and the film thickness should be small. The performance of the bearing/seal parts are influenced by the phase-shifted load. From the minimum power loss viewpoint, the bearing/seal parts under the dynamic load and constant supply pressure require high stiffness. The elastic deformation of the pad and eccentric load result in a decrease in film thickness and increase in the possibility of metallic contact.

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This method is for realizing accurate trajectory control of a horizontally jointed type robot. Generally, the dynamic characteristics of this type of robot are highly nonlinear and the electronic servomechanism has nonlinearities such that the rise times of these velocities are directly proportional to the amplitude of the input voltages. These become the causes of trajectory control errors when starting or moving the robot.
In the case where the velocity characteristics of the servomechanisms are equal to one another, the offset and transient errors will be negligibly small. Therefore, a new method of feeding back the difference between the robot servomechanism velocities is proposed. Moreover, to control a robot to move along a planned path, it has been necessary to compute the torque needed to drive all its joints accurately and a torque feed-forward method is used. This theory is applied to a robot, and the validity of its theory is proven by experiments.

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The main source of noise in hydraulic system is usually the positive displacement pump, which produces structure- and fluid-borne noise. Hence, to reduce noise in any hydraulic component, both structural and fluid vibrations must be reduced. For noise control, however, reducing noise is all very well, but improving noise into a desirable tone quality is also advisable.
This paper presents the development of an axial piston pump utilizing the irregular pitch cylinders to drastically improve the tone quality of noise generated by a pump. Irregular pitch angles of cylinders were determined within the range of 40±3° by a trial and error method so as to distribute the spectra of vibromotive force and moment as widely and uniformly as possible throughout the harmonics of pump rotational frequency (not of a piston frequency). The effectiveness of devised technique was examined mainly by the degree of dispersion and amplitude ratio of the harmonic spectrum of the sound intensity and sound pressure, and by sensory evaluation by means of hearing experiments.
It could be seen from a comparison test with a regular pitch pump that, in the case of an irregular pitch pump, the spectra of sound intensity and sound pressure as well as the vibration acceleration of the pump casing abundantly contained harmonics of small amplitude of pump rotational frequency, and that the pump noise was greatly improved from violent and harsh tone quality of standard (i.e., regular pitch) pump into a rather silent and mild tone quality. Consequently, it was confirmed that arranging cylinders irregularly in circumferential direction was extremely effective measures for quieting the noise from an axial piston pump.

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