Fluid Power Research Muto and Yamada Laboratory, Department of Human and Information Systems, Faculty of Engineering, Gifu University, Japan

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FLUID POWER RESEARCH CENTRES WORLD-WIDE

General Information

Furthermore, we established in 1990 United Graduate School of Veterinary Sciences in collaboration with Obihiro University of Agriculture and Veterinary Medicine, Iwate University and Tokyo University of Agriculture and Technology.

Similarly, United Graduate School of Agricultural Science was established in 1991 jointly with Shinshu University and Shizuoka University.

We have approximately 800 teaching staffs including 283 professors and 800 technical and administrative staffs. There are approximately 6000 undergraduate students and 1500 graduate students. In addition, 46 foreign undergraduate and 220 foreign graduate currently studying are studied in our campus.

Gifu University has made the academic agreements with 23 universities in Australia, Bangladesh, Brazil, China, Hungary, Indonesia, Korea, the Philippines, Sweden, Thailand, the United Kingdom, the United States of America and Vietnam. Under these agreements, exchange programs of students and researchers are undertaken. For example, about ten students from Lund University, Sweden and Seoul National University of Technology, Korea have participated in our summer school.

Our main campus is in the Yanagido area, outskirt of Gifu City, where 4 faculties excepting School of Medicine are located at present. University Hospital and School of Medicine are presently in the Tsukasamachi campus in the center of the city, and will join the Yanagido campus in 2004.

Muto and Yamada laboratory (History)

In 1994 Associate Prof. Hironao Yamada joined the research group, enlarging its field of interest to the design of hydraulic system (in particular of development of digital valve using PZT actuator and active suspension control system) and of virtual reality.

At present we have 9 graduate students involved in our research programs, 12 master course students and one doctor course student.

Research Projects

• Simulation of Hydraulic Systems,
• Control of Hydraulic Systems,
• Development of Hydraulic Systems and
• Virtual Realty Applications.

Simulation of Hydraulic Systems

Fig. 1: Block diagram gallery of the BDSP

The Dynamic Characteristics of Tapered Fluid Lines with Viscoelastic Pipe Walls
For convenience in investigating the dynamic responses of a liquid-filled tapered line with a viscoelastic pipe wall, a transfer matrix equation, relating pressure to volumetric flow, is derived. In this derivation, it was assumed that the rate of divergence (or convergence) of the line is comparatively small. The fluid line model employed in the analysis is one of an unsteady viscous flow; that is, the frequency-dependent effect of viscosity is taken into consideration. The viscoelastic pipe wall model is a modified version of the Voigt mechanical model, and it is distributed along the pipeline. The frequency response curves are calculated from the matrix, and the accuracy of the curves is evaluated by comparing them with the response curves obtained without assuming the small tapered angle. The results verify that the transfer matrix is accurate enough for practical applications.

Simulation of Pressure Pulsation Induced in Fluid Transmission Lines Including a Viscoelastic Hose
In hydraulic systems consisting of pumps and fluid transmission lines, we frequently encounter a problem of fluid borne noise (pressure pulsation). When these systems are installed, for example, into motor vehicles or machine tools, the systems should be designed as quiet as possible. For reducing the noise, flexible hoses can be effectively introduced to several parts of fluid lines. In these designs, an optimal design is necessary under the consideration of the combination of the pipe lengths of flexible hoses and rigid lines. That is because the flexible hoses cost more than the rigid lines do. Obviously, such an optimal design is made possible by predicting the situation of pressure pulsation induced in the systems. Recently we proposed a simulation method of fluid dynamics in viscoelastic lines. It was expected that the method would be applicable for predicting the pressure pulsation induced in systems with a pump and flexible hoses.

The purpose of this study is to confirm the validity of the simulation method when it is applied to flexible hose systems with pump. The fluid lines dealt with here are composed of a flexible hose (fluid viscoelastic line) and rigid lines. As a method for simulating fluid dynamics in a flexible hose, we applied a technique of formulating rational polynomial approximations for transfer matrix elements of fluid viscoelastic lines. Two kinds of fluid line systems, one connected with a vane pump and the other with an axial piston pump, are investigated. The waveforms of pressure pulsation induced in the systems are investigated by simulation. The obtained results are compared with experimental results.

Fig. 2: Schematic diagram of vane pump

Control of Hydraulic Systems

It could be verified by experiment and digital simulation that the NSFC developed in this study was useful and effective for the control of an electro-hydraulic servo system.

Fig. 3: Neuro Self-tuning fuzzy control system

Sliding Mode Control Using a Disturbance Observer for an Electrohydraulic Servo System
In electrohydraulic servo systems which are equipped with sliding mode controls (hereafter abbreviated to SLM control), a steady-state error is sometimes encountered in their time responses, apparently due to disturbances external to the system. The disturbances in such cases include, for example, an initial shift in the neutral position of the servo valve, or an offset of the servo amplifier.

The purpose of this study is to propose a method for overcoming the problem stated above. We propose to make use of a disturbance observer in the SLM control algorithm in order to estimate a suitable input for the suppression of disturbance. Under our proposed method, the controller can be adequately designed without knowing the characteristics of disturbance, if the disturbances satisfy the matching condition. The usefulness of the method could be verified experimentally by applying it to an electrohydraulic servo system.

Fig. 4: Block diagram of the sliding mode control system

Development of Hydraulic Systems

Fig. 5: High-Speed On/Off Valve with PZT Actuator

Hydraulic Active Suspension with High-speed On/Off Valves
In this study, a new system of an active control hydro-pneumatic suspension for automobile is proposed and its dynamic performance is tested. The proposed system is composed of high speed On/Off solenoid valves, in stead of a proportional valve or servo-valve in conventional use. As a method for driving the On/Off valves, the pulse width modulation (PWM) method is adopted. Since the choice of On/Off valves driven in digital mode, such as the PWM method, leads the system to an economical and reliable one, it is expected that the proposed system can realize high reliability and cost reduction. The dynamic characteristics of the system are investigated by experiment and digital simulation. These results are compared with those obtained from a conventional system composed of a pressure control valve, and the availability of the proposed system is confirmed.

Fig. 6: Quarter car test bench system of active suspension

A Precision Driving System Composed of a Hydraulic Cylinder and High-Speed On/Off Valves
In manufacturing technology, the predominant tendency in recent years has been for machine tools, for example, turning-, milling-, and drilling-machines, to employ electrically operated actuators such as a servo-motor equipped with a ball screw. There are, however, various problems with these electric driving systems; they are excessively large-sized with complex machinery, and their application is expensive, as seen, for example, in the case of the NC-machine. In order to solve these problems, this study aims to develop a precision driving system actuated by a hydraulic cylinder. The hydraulic driving system consists of a cylinder and four ON/OFF solenoid valves. The valves are the same as those used in a fuel injector of an automobile, which are capable of high speed switching, as fast as 1.5 ms. It was confirmed in experiments that the developed system had a moving resolution of 1.2 µm and, as a result, was applicable to a precision driving table for micro-processing.

Fig. 7: A Precision Driving System

Virtual Realty Applications

Fig. 8: Construction robot system

Hydraulic Master-Slave System for Tele-Robotics
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 haptic display device. The term “haptic display” indicates a function by which the operator can feel a force fed back from the slave. In order to produce a haptic display composed of hydraulic servo-systems, we must solve a problem called back-drivability, in which an actuator in a hydraulic servo-system cannot be operated freely by manual means. As a practical solution to this problem, we proposed a driving method of actuator that uses a force sensor attached to the actuator. Furthermore, in this study we proposed an improved type of parallel control method suitable for controlling the bilateral master-slave system composed of electro-hydraulic servo-systems.

Fig. 9: Hydraulic Master-Slave System

Hands-on Wheelchair Simulator
Recently, it has become important to improve the usability and safety of public transportation for wheelchair users such as aged and people with disabilities. Thus, designers need to assess the usability of facilities in the design stage based on the available data. The present study’s objective is to develop a wheelchair simulator and control method suitable for barrier-free transportation. By controlling the hand-rims of the wheelchair, the operator can recreate traveling and turning motion in a virtual reality (VR) space. The position and attitude of the wheelchair are presented to the operator as the motion of a six-axis motion base. Through a head-mounted display, a computer graphics system provides the operator with scenery that changes in accordance with the wheelchair’s operation. To study barrier-free transportation on board a ship, the ship’s motion was recreated in VR space, and the operational ability of the wheelchair was compared between the cases including and not including the ship’s simulated motion. The experimental results demonstrated the feasibility of the developed system.

Fig. 10: Simulation system of wheelchair