Yasuo Jimbo

Study of an active vibration isolation system: a learning control method

Improvements of performance of a vibration isolation table supported by an air-spring are attempted. A servo-control mechanism regulates the air in the air-spring so that the table can always remain immobile in spite of the vibrations of the floor. The principle of this servo-control is as follows. At the instant of upward movement of the table, the air in the air-spring is impelled to flow out. At the instant of downward movement of the table, the air is pushed to flow in. In this paper, a method of determining an optimal control-signal, which regulates the air in the air-spring, is discussed from a learning control standpoint by a microcomputer. For periodic disturbances, adjustment of control signal for both amplitude and phase is applied. For random disturbances, adjustment of control gain only is applicable.

Four-Elements Model Representation of Rubber Vibration Isolator

Three kinds of mechanical models for rubber vibration isolators are analyzed, and their transmissibilities are compared with experimental results. Two-elements model which is known as Voigt model is widly used, but its calculated value of resonance frequency does not agree with the measured one. Three-elements model is composed of two spring elements and one damping element. The characteristics of resonance can be made to agree with experimental results by using proper values of three constants. However, when the mass of the load is changed, the calculated characteristics of resonance do not agree with the measured ones. Four-elements model is composed of two spring elements and two damping elements. In this case by using proper values of the four constants, the calculated transmissibility characteristics can be made to agree with the measured ones for the wide range of load mass. It is concluded that the four-elements model is most suitable for the rubber vibration isolator.

Mechanical characteristics and functions of fishing rods. (2nd report). Deformation and jumping phenomenon of a beam inclined by about 90.DEG..

This paper deals with large deflections of thin, straight and tapered cantilever beams set up almost vertically. The results are as follows : (1) When a cantilever beam is placed almost vertically, the deformation of the beam is very small for the load lower than a certain critical value, while it becomes very large suddenly for the load exceeding the said critical value. (2) When the inclination of the beam exceeds the vertical angle, two deformation forms can exist for the load greater than the above-mentioned critical value. As the inclination increases gradually from a small value, the deformation form changes continuously, and when the inclination reaches a certain value exceeding an angle of 90°, it jumps from the 1st form to the 2nd. (3) When the load is applied slightly off-centered and more over the inclination passes through an angle of 90°, the beam turns to the direction of the eccentric load and the deformation form transfers from the 1st form to the 2nd. (4) In the actual fishing, it is experimentally known that if we incline the fishing rod by an angle of more than 90°, we often lose the control of the rod because the rod tends to turn clockwise or counterclockwise. This fact can be explained by this dynamical analysis.