A current two-stage servovalve is limited in its response speed for high flow-rate control. Giant magnetostrictive material (GMM) has the possibility of being used in a high-speed pilot valve instead of using torque-motors, however its displacement is too short compared to its length and loses valve compactness. For solving this issue, a new type of GMM actuator is developed. The actuator consists of two sets of GMMs which are connected serially through a Z shaped holder in one coil bobbin. Every set of GMMs consist of three pieces of small GMM rods of 30mm in length in a triangular position for getting higher stiffness compared to a single rod. The actuator controls a displacement of 50μm at a frequency of 800Hz, and the two stage valve controls a flow rate of 50L/min at 7MPa in a sinusoidal frequency of 200 Hz at -3dB point.

抄録全体を表示

This paper deals with the trajectory control of a three degree-of-freedom hydraulic parallel mechanism. A hydraulic parallel mechanism is useful in an environment where high power and high accuracy are necessary. Since this mechanism is composed of three electro-hydraulic-servo systems, the characteristics of the mechanism are influenced by many nonlinear elements or disturbances external to the servo systems. Representative examples for such disturbances are a dead time characteristic and an initial shift of the neutral position of the servo valve. In order to realize a robust system against such influences, in this study, we applied a sliding mode control using a disturbance observer to the mechanism.The dynamic performance of the trajectory control of such a mechanism was investigated by experiments. As a result, we confirmed the validity of the applied method.

抄録全体を表示

A new method of estimating wave speed in a pipe is proposed. A continuity equation of pipe flow can be arranged so that wave speed is included in a coefficient that relates the differentiation of pressure with respect to time and the differentiation of flow rate with respect to distance along the pipe axis. The differentiation signals are calculated from pressure signals using a simulation model of pipeline dynamics, that is an optimized finite element model. Bootstrap algorithms are applied to estimate wave speed included in the coefficient. Simulation and experiments are carried out to demonstrate the estimation method.

抄録全体を表示

The unsteady phenomena in cases of elastic deformation of disk-type hydrostatic thrust bearings based on the cyclic change in the supply pressures and loads are discussed theoretically. The bearing/seal parts are made up by combining stainless steel with stainless steel and stainless steel with plastics. The main results are as follows :
1) The fluid film converges more rapidly with increased supply pressure. For elastic materials, a stable fluid film shape is obtained more easily but the response is slower than that of rigid materials.
2) Due to the increase in the squeeze effect with increasing frequency of loads or supply pressures, the film shape becomes more stable but the response slower. This phenomenon is more marked with elastic materials.
3) The delay in the pocket pressure change is clearer with increased supply pressure or frequency of load change.

抄録全体を表示

In this study, we deal with a bilateral master-slave system for tele-robotics composed of electro-hydraulic servo-systems. In a teleoperated master-slave system, the master has to play two roles, firstly as a reference input device to the slave and secondly as a force display device. In order to produce a force display composed of hydraulic servo-systems, we must solve a problem called back-drivability, in which the actuator in a hydraulic servo-system cannot be operated freely by manual means. As a practical solution to this problem, we propose a driving method for the actuator that uses a force sensor attached to the actuator. Furthermore, as an application of the proposed force display, we construct a bilateral master-slave system composed of electro-hydraulic servo-systems. Experimental results of the manipulate on of motion by this system are presented and, consequently, the validity of the hydraulic force-display was confirmed.

抄録全体を表示