The position control of a hydraulic cylinder using a constant pressure system is studied. A hydraulic transformer based on a FFC pump/motor is used as a control component to drive the cylinder with a load. The transfer function from displacement of the variable displacement pump/motor to the cylinder position is derived and a feedback controller and feedforward controller are designed and implemented. With these controllers the friction torque and the leakage of the transformer can be compensated for and sufficient accuracy of positioning is achieved.

View full abstract

A vacuum is frequently utilized for handling systems in factory automation. Because of the vacuum pressure, the change in state of air may differ from that of positive pressure systems during charge or discharge. However, pressure and temperature responses in the vacuum condition have not been examined up to now. Therefore, in this study the pressure and temperature responses of RC circuit in the vacuum condition is investigated. As a result, the research can be summarized as follows: 1) When the positive and vacuum pressure are compared in the same pressure ratio, it is found that the heat transfer rate is larger in the positive pressure case, because of the larger mixing effect.
2) The temperature responses are determined by the thermal-time constants. Since the vacuum pressure gets smaller thermal-time constants which concern the air density, the temperature responses show a smaller variation than those of positive pressure. Therefore, the pressure response is slower in the case of negative pressure.
The analysis method of pressure responses used in positive pressure conditions is feasible in the vacuum condition. This has been verified by experiment.

View full abstract

The objective of this study is to develop a wheelchair simulator suitable for barrier-free transportation. By controlling the hand-rims of the wheelchair, the operator can re-create traveling and turning motion in a virtual reality environment. The position and attitude of the wheelchair are presented to the operator with 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 operation. To study barrier-free transportation by ship, the ship’s motion was re-created in a virtual reality environment, and the operational ability of the wheelchair was compared between the cases with and without the motion. As a result of experiment the validity of the developed system was confirmed.

View full abstract