藤田 孝之

In order to maintain human health care, it is important to record daily activity. For recording daily human activity, monitoring system which consists of multiple microelectromechanical systems (MEMS) has been developed. Using the MEMS based monitoring system, numerical data of subject's activity can be stored into a database. For example, when subject's activity on a single day is recorded, a huge volume of data is saved. To estimate the subject's activity condition from such a huge volume data, a fuzzy rule based approach is used in our study. Our proposed method consists of two steps of abstraction. First, action primitives are defined. In the first-step abstraction, sensor data is expressed as a sequence of actions by using the defined action primitives. Next, a fuzzy rule which maps a sequence of actions to a behavior is defined for each behavior. In the second-step abstraction, each sequence of actions is expressed as a behavior. From the results of abstraction, we can estimate the subject's state. © 2010 IEEE.

Output-voltage operation on a sensor structure is proposed and a tri-axial accelerometer with low cross-axis sensitivities is designed. The output voltage between the electrodes sandwiching piezoelectric thin-films on a deforming structure is proportional to the in-plane stress of the piezoelectric thin-film. If the piezoelectric thin-film is processed to separated elements and the electrodes of the elements are connected in series, the output voltages from the series-connected piezoelectric elements are multiplied or canceled depending on the situations of the internal-stresses (i.e. compressive or tensile) of the elements. Proper design of the electrode connections by taking the deformation shape of structures into consideration can realize expected output-voltage operations on the device structure. The principle of structure-based output-voltage operation is applied to the design of a tri-axial accelerometer with low cross-axes sensitivities. Finite-element-method (FEM) simulations of the tri-axial accelerometer revealed the cross-axis sensitivity of less than 1.5 %. (C) 2010 Published by Elsevier Ltd.

Monitoring of cardiorespiratory information such as the respiration and heartbeat is very important for public healthcare. Belt-type cardiorespiratory sensors using polyvinylidene fluoride (PVDF) as the sensing material have been studied by many research groups. In order to extract the respiration and heartbeat signals from the sensor output, very complicated low-frequency filtering circuits and analysis schemes are required. In this research, we propose a PVDF-based cardiorespiratory sensor with independently optimized sensitivity to heartbeat and respiration. The sensor comprises of a bending-sensitive unit and a bending-insensitive unit. The heartbeat signal can be optimized by using the bending-insensitive mode, and the respiration signal can be maximized by using the bending sensitive mode. This principle was experimentally verified using a prototype device. A batch fabrication process for the patch-type cardiorespiratory sensor made of flexible substrate, PVDF and flexible electrode was described. (C) 2009 Published by Elsevier Ltd.

It is important to record daily activity for well-maintained human health care. For this purpose, a monitoring system based on multiple microelectromechanical systems (MEMS) has been developed. Using the MEMS based monitoring system, several kinds of numerical data of subject's activity can be stored. When subject's activity on a single day is recorded, a huge volume of data is obtained. To estimate the subject's behavior from such a huge volume data, we propose a fuzzy rule based approach. Our proposed method consists of two steps of abstraction. First, action primitives are defined. In the first-step abstraction, a fuzzy rule which maps a part of numerical data onto an action primitive are generated from sample data or human knowledge. Therefore, numerical data are expressed by a sequence of action primitives. Next, a fuzzy rule which maps a sequence of actions onto a behavior is defined by human user for each behavior. In the second-step abstraction, each action sequence is expressed as a behavior by using the defined fuzzy rules. From the results of the abstraction, we can estimate the subject's state.

In this paper, we present the concept of a microelectromechanical systems ring laser gyroscope (MEMS-RLG) and its optical components. MEMS-RLG has a semiconductor optical amplifier (SOA) enclosed with mirrors that form an optical loop for an external laser oscillator in free space. To confirm the feasibility of MEMS-RLGs, we constructed an experimental device with commercially available SOA and mirrors for external oscillation. We also show the fabrication and characteristics of optical components such as movable mirrors and a lens-positioning device, which are required for a miniaturized MEMS-RLG.

This paper presents series-connected PZT elements that yield high output voltage, and also shows complete establishment in the fabrication process. Series-connected PZT elements are realized by connecting the upper electrode of a PZT element with the lower electrode of another PZT element. Sputtered PZT thin-film has perovskite crystalline structure and piezoelectric coefficients up to 40 pC/N. To avoid troublesome wet etching, the PZT films, the electrodes, and insulation layers are dry-etched. The all dry-etching process performs multilayer wiring of the electrodes. Evaluations for the PZT elements validates that the output voltage is the sum output voltage of each single element.

This paper provides MEMS (micro-electromechanical systems) vibratory beam accelerometer (VBA) for human movement measurements, which have a digital control system. The device structure with size of 5 x 5 mm2includes a frame, heavy mass, thick suspension beams, and thin vibrating beams made of silicon single crystal. The VBA measures acceleration using the resonant frequency change of the vibrating beams, which are designed to provide little resistance to movement along the sensitive axis and stiff resistance on the off-axis. This provides low off-axis sensitivity and high shock survivability. In this study, we designed a fully digital PLL (phase-locked loop) circuitry in a FGPA (field programmable gate array) based hardware controller. By Allan deviation, we proved that our system shows an extremely high resolution of 34 μG Hz−1/2and wide dynamic range of 90 dB in a device operation at 1 mTorr ambient pressure. © 2009, TSI® Press Printed in the USA.