Akihiro Torii

A method for determining the spring constant of cantilevers for atomic force microscopy

Cantilevers fabricated by means of micromachining techniques are usually used for atomic force microscopy. In this paper, the spring constant of an atomic force microscope (AFM) cantilever is determined by using a large-scale cantilever. Since the spring constant of the large-scale cantilever is calibrated accurately, the spring constant of the AFM cantilever is determined precisely by measuring the deflections of both cantilevers simultaneously using heterodyne interferometry. The slope of the force curve gives the spring constant of the AFM cantilever. It is not necessary to measure the dimensions of the AFM cantilever in the proposed method. Although this method is simple, the spring constant of the AFM cantilever is obtained accurately.

A method of current detection for an active power filter applying moving average to pq-theory

The accuracy of harmonic currents detector and characteristics of current controls are important to improve the compensation characteristics of an active power filter. This paper proposes a detector which has high accuracy and good response by applying pq-theory and moving average high-pass-filter (HPF) and good response current control by applying current-deviation code-distinction. A new modified detection system using a moving average HPF whose sampling time is changed according to the source frequency fluctuation is also proposed. The active power filter combining the proposed method of the detector and the current control can compensate harmonic currents which are generated by a three-phase rectifier with a DC filter capacitor with high accuracy and good response.

AC chopper using four switches

Several circuits were proposed as methods for adjusting AC power. In this paper, the authors propose an AC chopper circuit with four switches and examine the fundamental character of the circuit. It has a simple configuration and excellent performance. The DC snubber can be used by dividing an input filter capacitor into two parts. The proposed circuit has high efficiency for adjusting AC power, because it is composed of fewer switches and DC snubbers.

Automatic mask alignment in the theta direction using moire sensors

Automatic mask alignment in the theta direction using moire sensors is reported. The relation between small angular displacement and linear displacement is clarified. A computer-controlled angular alignment system is developed. A desired alignment position is easily set by a computer. In our experimental condition, angular accuracy of the order of 14*10-7 rad is realized by automatic computer control.

Scanning force microscope technique for adhesion distribution measurement

A scanning force microscope technique is described to study the relation between topography and the local adhesion. The drift has been a main problem in investigating this relation since a long period is required to measure force curves over the scan area. To circumvent this problem, we propose a methodology to detect the topography and the adhesion from force curves simultaneously. Since this information is obtained from the same force curve, the distribution of the tip position corresponds precisely to that of the adhesion. The detailed relation between the tip position and the adhesion is measured on a fine lithographic grating.

Motion analysis of a micro-actuator using three piezoelectric actuators

Displacement of a micro-actuator is described theoretically and experimentally. The actuator uses three stacked-type piezoelectric actuators which are connected in an equilateral triangle, and three electromagnets which are attached at all the vertexes of the triangle. The actuator, which can realize a precise motion, is developed for a flexible conveying system, such a desktop manufacturing system. The actuator is used in a micro/nano system which requires a nanometer resolution with multi degrees of freedom. The displacement of the actuator is simulated and demonstrated experimentally

Boost type three-phase diode rectifier using current resonant switch

This paper proposes a boost type single switching device three-phase diode rectifier with a current resonant switch to decrease switching loss and the total harmonic distortion (THD) of the input current. It is confirmed that a switching device in the proposed circuit operates in zero current switching by simulation. This paper also shows that the proposed circuit can decrease the THD of the input current and can improve the input current waveform compared with the conventional boost type single switching device three-phase diode rectifier.

An xy/spl theta/ actuator using piezoelectric and electromagnetic actuators

Microactuators with a micro tool and a micro sensor can provide a lot of benefits to precise engineering. Precise positioning is needed in precision engineering. A system with multi degrees of freedom is required for industrial application. A system with multi degrees of freedom is composed of some systems with one degree of freedom. Therefore, the system becomes complicated and large. We propose a new actuator which can move in x, y and /spl theta/ directions by the extension of piezoelectric actuators and the adhesion of electromagnetic actuators. The proposed actuator realizes high resolution by using the piezoelectric actuator. We describe the structure and principle of the proposed actuator. In order to demonstrate the proposed actuator, we constructed the actuator and measured the velocity in x and /spl theta/ direction. The measured fastest velocity in x direction was 190 /spl mu/m/s and that in /spl theta/ direction was 9.5 mrad/s. The resolution in x direction was obtained to be 0.24 /spl mu/m and that in /spl theta/ direction was 0.1 mrad. We are now improving the resolution of the proposed actuator.

Analysis of a Three-Phase Buck-Boost AC Chopper Controlled in Two Phases

We propose a three-phase buck-boost AC chopper controlled by two phases. Characteristics of the circuit are analyzed by the simulation considering the dissipation of semiconductor devices and inductors. Ripple and total harmonic distortion (THD) of an input current and an output voltage increase when inductive components increase in the load. Variations appear in each phase in buck-boost ratio. The resonance frequency is changed due to the inductive components in the load. The pi-connected output filter is analyzed, and it operates as the second reverse L-connected output filter. THDs in the output voltages are improved when the capacitance in the output filter is changed to adjust the resonance frequency of the output circuit. The three-phase four-wire system is analyzed, and the circuit is compared with the two phases control method. Then, the cause of unbalance at each phase for the three-wire systems is proved to be the two phase control method.

A new method for separating AC component of instantaneous real power and imaginary power suitable for active filters

In a control system of active filters, p-q theory can be used for the calculation of higher harmonic currents. A high-pass filter of the first order is usually used for separating the AC components of instantaneous real power (p) and instantaneous imaginary power (q). However, in such a system the transient response for a load change is not high enough. Here, the authors propose a new control system in which the AC components are derived from p and q using a moving average value calculation method. By the proposed system, control response and accuracy are very good-even in the case of an abrupt load change.