非対称シリンダを有するサーボ試験機での岩石試験の制御性

1.はじめに

2.実験装置および無負荷時の応答

 2.1 実験装置

 2.2 無負荷時の応答

3.一軸圧縮試験時の制御性

 3.1 実験方法と試料岩石

 3.2 三城目安山岩 

  3.2.1 応力−歪み曲線と誤差信号の関係

  3.2.2 シリンダ室の圧力の変化

 3.3 秋吉大理石

  3.3.1 応力−歪み曲線と誤差信号の関係

  3.3.2 シリンダ室の圧力の変化

 3.4 稲田花崗岩

  3.4.1 応力−歪み曲線と誤差信号の関係

  3.4.2 シリンダ室の圧力の変化

4.サーボ弁とシリンダのモデル

5.考察

 5.1 シリンダ室の圧力の変化

 5.2 非対称シリンダでの制御性の劣化

6.まとめ

参考文献

キーワード:非対称シリンダ、サーボ試験機、岩石、制御性、載荷速度


Control Performance of Servo-Controlled Testing Machine with Asymmetrical Cylinder

Abstract

In the previous papers, control performance of servo-controlled testing machines with a symmetrical cylinder was discussed analytically and numerically. An asymmetrical cylinder is widely used to reduce the cost and size of testing machines. However the asymmetrical cylinder has nonlinear characteristics, and the control performance of it is inferior to the symmetrical cylinder. In this paper, the control performance of a servo-controlled testing machine with asymmetrical cylinder is discussed analytically on basis of the experimental results.

Uniaxial compression tests using Sanjome-andesite, Akiyoshi-marble and Inada-granite were conducted in order to clarify the control characteristics. Actually, pressures of upper and lower chambers within the cylinder were measured. It was found that the pressures changed depending on the direction of piston movement. The pressure decreased in case of moving to the loading direction, and the amount of pressure decrease was large at high piston velocity. The pressures in the cylinder were analytically examined with aid of a simple model which consisted of a cylinder and a servo-valve. These theoretical results coincided with the experimental results.

Sometimes in the post-failure region, the piston tended to move reversely. At that time, the asymmetrical cylinder showed inferior control performance caused by the followings;

1) Larger amount of oil inflow is necessary.

2) Feedback gain changes depending on the direction of piston movement.

The control performance of asymmetrical cylinder can be possibly improved by adjusting the followings; 1) large oil-leakage at the cylinder, 2) variable flow-coefficient at orifice, 3) variable feedback gain.

KEY WORDS: Asymmetrical cylinder, Servo-controlled testing machine, Rock, Control performance, Loading rate