Katsumasa Suzuki

Improving Zielke’s Method of Simulating Frequency-Dependent Friction in Laminar Liquid Pipe Flow

Zielke’s technique of using a method of characteristics to simulate transient phenomena of a liquid transmission line is accurate, easy to apply to complicated systems and therefore, frequently used. However, it requires a very large amount of computation time and computer storage to simulate frequency-dependent friction in a transient liquid flow. Searching for a way to counteract these disadvantages, the authors took note of the fact that the weighting function, which is the root of the above problems, is given by exponential functions or other functions depending on dimensionless time. In order to perform mathematically equivalent calculation without approximations, they have developed a new method which requires much less computation time and computer storage than Zielke’s method. The calculation process is shown by a block diagram to facilitate visual understanding of the method.

DYNAMIC CHARACTERISTICS OF PARALLEL LINK MECHANISM WITH SIX DEGREES OF FREEDOM USING ELECTRO-HYDRAULIC SERVO CYLINDERS

The Stewart platform type parallel link mechanism with 6 degrees of freedom is a structure which has arranged six single rod hydraulic cylinders parallel between the base platform and the end effecter of the controlled object. The both ends of each link are connected with the base platform and the end effecter using free joints, respectively. The terminal can rotate freely. By controlling the length of each link by the hydraulic cylinder, the position and posture of the end effecter is controlled with 6 degrees of freedom in three-dimensional space. In this report, the dynamic characteristics between the input and output of one link that comprises the parallel link mechanism is measured. The frequency response is measured for the various center position or attitude of the end effecter. The load mass and the amplitude are also changed. The interference that each link receives from one link is examined by experiment. The frequency response of the interference that each link received is presented.

Interaction between oil hammer and poppet valve.

A poppet valve is used solely as a check valve and also included as a pilot part in various kinds of control valves in oil hydraulic circuits; therefore, it is very important to clarify its characteristics.The purpose of this paper is to search the behavior during tens ms when it responds to a quick flow change. In this research, a check valve is used as one of the examples of poppet valves. The composition where an oil hammer influences the valve is treated as one of examples of a quick change in pressure and flow velocity. The composition is an important part of the intensifier using an oil hammer which the authors have been developing and also the result will provide fundamental data to clarify the dynamic characteristics of a hydraulic system with a poppet valve.The transient phenomena are researched by experiments and simulations. For the analysis by simulation, fundamental equations concerning a check valve and those by the characteristics method concerning a pipeline are presented. They are solved simultaneously using the Runge-Kutta methods. The effects of the spring, mass of the poppet, and volume and length at the connective parts on a peak generated pressure is clarified.