Uichi Nishizawa

Phase Difference Control System for TR Motor

The authors have developed a translational and rotational motor in one device by ultrasonic drive technology. This motor has two degree of freedom, that is, translational movement and rotational movement (TR motor). Two movements are controlled independently or simultaneously such as screw movement. As the motor is driven by ultrasonic vibration at the resonant frequency, the motor (stator) is designed and optimized by FEM analysis. Based on the analysis of FEM, the authors have developed a TR motor successfully. It shows good controllability in both movements.

Spherical Ultrasonic Motor for Space

In resent years, space satellites have been widely used in the world. They cause the space debris, which has become a problem because they may collide each other in space. In our study, we have developed a Spherical UltraSonic Motor (SUSM) with 3 DOF in space use to drive the satellite thruster and resolve the space debris problem. When the satellites enter the atmosphere at the end of the life, SUSM controls thrusters for the right direction in falling down to the earth to burn in the air. We have made experiments to evaluate torque, durability and lifetime. It shows that the torque and lifetime meets target value. But durability does not meet the target lifetime. To resolve it, we have applied a new stator lining materials and shifted frequency with 0.4 kHz from resonant frequency. Finally we have succeeded in durability-required specifications.

Development of underwater inspection system for dam inspection: Results of field tests

Social infrastructures in Japan are becoming aged and robotic infrastructure inspection tools are required in order to inspect the conditions for maintenance. Authors have been developing the new underwater inspection system for underwater infrastructures. It consists of an unmanned surface vehicle and a remotely operated vehicle (ROV) suspended from the surface vehicle. The system can obtain position of the inspected point without using any higher cost device. This paper explains functions of the developed experimental model and results of experiment at the pool and actual dam. In the pool experiment, the auto inspection function was verified that it can obtain the wide images of target wall with slight manual operation, and in the actual dam, the experimental model obtained the images of target wall and conduit gate. The system has high stability due to such pendant type ROV, thus the inspection was carried out with easy operations. On the other hand, the maneuverability of the experimental model was influenced by the wind, and the position accuracy from the MEMS GNSS/INS sensor became worse near the dam wall.

Development of underwater inspection system for dam inspection

Deteriorations of social infrastructures have been progresses in Japan. To prevent accident due to its failing, effective inspection system is needed. We have been developing underwater inspection system for dam inspection which is called Dam Inspection System (DIS). It is composed by Unmanned Surface Vehicle (USV), and Remotely Operated Vehicle (ROV). USV is called Surface water platform (SWP) and ROV is called Under Water Platform (UWP) in DIS. The SWP and the UWP are connected by underwater cable, the UWP is hanging from the SWP due to negative weight in water itself. Because of this, the DIS has following advantage compared to current system such as ROV: the inspection position by the UWP can be estimated without external device, operation is easy, and no thrusters blow up the sediment while ascent or descent of the UWP. The accurate positon data is necessary for periodical inspection to evaluate aged deterioration. It is obtained from the SWPs positon and length of underwater cable while the DIS is stable in static water, but the DIS is moving, it is necessary to consider dynamics for precisely position estimation. The objective of this research is to reveal dynamic characteristic and to develop inspection position estimation method and position control method for the DIS. As the first step, we carried out the simulation using simplified model of the DIS and verification experiment. This paper report simplified model of the DIS and result of simulation and experiment. Both result indicate a DISs characteristic that the longer cable and the lighter weight of the UWP in water makes slowly the response of the UWP against the motion of the SWP. On the other hands, we obtained that it is necessary to improve dynamics model of the DIS, and to measure parameter of testbed in accurate, because of the simulation is not reproduce motion of verification experiment sufficiently.

Intravascular Stent Motor

We have developed a movable stent motor in the blood vessel by applying the technique of the ultrasonic motor. We have also designed a stent motor which consists of two parts; a stator part and receiver part. The receiver unit obtains the ultrasonic wave from outside and the stator generates a driving force. The stator is the coil shape and it can move smoothly in intravascular. Adding that, we have designed the horn to provide ultrasonic energy to it from outside of human body. We have made experiments by the horn and the stent motor and we have succeeded in driving the stent motor in the water back and forth.