Shin Asano

Micro-positioning Stage of 6 Degree-of-freedom with Nanometer Resolution

A micro-positioning stage comprising PZT actuators and consisted of monolithic flexure hinges as guides, formed by means of wire cut EDM, was developed (Fig. 1). The stage position is determined by capacitance gages with a resolution of 5nm, using the closed-loop control system. This stage can move with respect to 6 degree-of-freedom (X, Y, Z, θ x , θ y , μ z ), so it can compensate errors of generated by pitching, rolling and yawing.

Development of the integrated simulation tool for behavior and loads estimation of ocean current power plant

Owing to huge amount of kinematic energy, ocean current has the potential to be a base power source. However, ocean current power plant has to be submerged in the sea, making it difficult to maintain; therefore it must have high durability and reliability for long-term operation towards utilization. Equipment design approach considers various loads which occur during normal operation of the plant such as start-and-stop or emergency stop. Loads such as force on blade, buoyancy on float, drag force on cable and resistive force on mechanical drive-train and dynamo dynamically interact with each other and are affected by ocean current conditions. In this paper we have developed an integrated simulation tool to estimate the behaviors and loads on the components of ocean current power generator. It consists of six subsystems and each one can be simulated individually. By integrating all state function between subsystems, simulator is able to balance and converge dynamic equations and evaluates the electric-generating capacity, loads on equipment and behavior of the float. The simulator is verified for accuracy by comparing with tow tank scaled model. It was found that change in current speed and pitch angle of the float matches well with the simulation result.

Development of a new measurement system for straightness error by a heterodyne interferometer with a grating

A new straightness error measurement optical system has been developed. This system consists of three components: ( i ) A He-Ne Zeeman laser, ( ii ) A grating secured onto a slide table and (iii ) A heterodyne interferometer where a beat signal, which includes a phase shift δ φ depending on an in-plane displacement δ x of the grating, is generated. Straightness error can be measured, because δ φ is proportional to δ x In this study, using this system, straightness error of a slide table is measured experimentally. Straightness error measured by this system is good agreement with one measured by a commercial laser interferometer system. The effectiveness of this system is confirmed by this result.