Yoshiyuki Hata

An SOI 3-axis accelerometer with a zigzag-shaped Z-electrode for differential detection

We have developed a fully-differential 3-axis accelerometer with a novel zigzag-shaped Z-electrode, which is used for motion controls of automobiles and robots.

An SOI tactile sensor with a quad seesaw electrode for 3-axis complete differential detection

This paper presents a novel SOI capacitive tactile sensor with a quad-seesaw electrode for 3-axis complete differential detection, which enables integration with a CMOS. For differentially detecting 3-axis forces, the tactile sensor is composed of four rotating plates individually suspended by torsion beams. In this study, to demonstrate the working principle, we fabricated a test device that integrates an SOI substrate with the quad-seesaw electrode and an anodically bondable LTCC substrate with fixed electrodes as an alternative to the CMOS. The experimental results of the test device successfully demonstrated the working principle as well as 3-axis differential detection with a matrix operation.

Fully-integrated, fully-differential 3-axis tactile sensor on platform LSI with TSV-based surface-mountable structure

The present paper reports a 2.8-mm-square surface-mountable MEMS-on-LSI integrated 3-axis tactile sensor for robot applications, which incorporates sensing and signal processing in a single chip. The MEMS part has a quad-seesaw-electrode structure for fully-differential capacitive 3-axis force sensing. The LSI is an original sensor platform LSI equipped with deep annular-type through silicon vias (TSVs). A multi-project LSI wafer was processed after fabrication in an LSI foundry. The MEMS part and the LSI part were integrated by Au-Au thermocompression bonding. The output is a digital packet and is transferred through the TSV and a bus line. A working test successfully demonstrated the fully-differential capacitive 3-axis force sensing of the fully-integrated tactile sensor.

A Tactile Sensor Network System Using a Multiple Sensor Platform with a Dedicated CMOS-LSI for Robot Applications

Robot tactile sensation can enhance human–robot communication in terms of safety, reliability and accuracy. The final goal of our project is to widely cover a robot body with a large number of tactile sensors, which has significant advantages such as accurate object recognition, high sensitivity and high redundancy. In this study, we developed a multi-sensor system with dedicated Complementary Metal-Oxide-Semiconductor (CMOS) Large-Scale Integration (LSI) circuit chips (referred to as “sensor platform LSI”) as a framework of a serial bus-based tactile sensor network system. The sensor platform LSI supports three types of sensors: an on-chip temperature sensor, off-chip capacitive and resistive tactile sensors, and communicates with a relay node via a bus line. The multi-sensor system was first constructed on a printed circuit board to evaluate basic functions of the sensor platform LSI, such as capacitance-to-digital and resistance-to-digital conversion. Then, two kinds of external sensors, nine sensors in total, were connected to two sensor platform LSIs, and temperature, capacitive and resistive sensing data were acquired simultaneously. Moreover, we fabricated flexible printed circuit cables to demonstrate the multi-sensor system with 15 sensor platform LSIs operating simultaneously, which showed a more realistic implementation in robots. In conclusion, the multi-sensor system with up to 15 sensor platform LSIs on a bus line supporting temperature, capacitive and resistive sensing was successfully demonstrated.

3-Axis fully-integrated surface-mountable differential capacitive tactile sensor by CMOS flip-bonding

This paper reports a 3-axis MEMS-CMOS integrated tactile sensor for surface-mounting on a flexible bus line. This 3-axis sensor uses a bran-new CMOS LSI with capacitive sensing circuit and other extended functionalities (e.g. configurability and a robust clock data recovery algorithm). The sensor is composed of a flip-bonded CMOS substrate with a sensing diaphragm and a special low temperature co-fired ceramics (LTCC) substrate with vias. These substrates are electrically and mechanically connected by Au-Au bonding, forming sealed differential capacitive gaps. The completed sensor outputs coded 3-axis digital signals according to applied 3-axis force with small cross-sensitivity and hysteresis.

Flipped CMOS-diaphragm capacitive tactile sensor surface mountable on flexible and stretchable bus line

The following novel configuration has been developed for a MEMS-CMOS integrated tactile sensor on a flexible and stretchable bus for covering a social robot body: a sensing diaphragm is formed on a CMOS substrate by backside etching, and the CMOS substrate is flip-bonded to a low temperature co-fired ceramic (LTCC) substrate. By this configuration, no through-silicon vias (TSVs) are needed, simplifying the fabrication process. The flipped CMOS substrate and the LTCC substrate were bonded and electrically connected using Au-Au bonding, which also formed differential capacitive gaps. A flexible and stretchable wire was fabricated by metal etching and polyimide laser cutting. The tactile sensors, which were mounted on the surface of the flexible bus, sent coded digital signals according to applied force.

SOI 3-axis accelerometer with a stress reduction structure

We developed a novel stress reduction structure (SRS) for a capacitive SOI 3-axis accelerometer for the advanced motion control of automobiles and robots. To improve the stability of the sensor output against temperature change, an FEM thermal stress analysis was carried out on a model with a sensor chip, a circuit board, and a package. The FEM results showed that the thermal stress caused by the different coefficients of thermal expansion bent the sensor chip and produced a change in the z-electrode gap. The zero output drift especially in the Z-axis direction by sensor chip bending should be minimized. The SRS was composed of grooves in both the lower and upper Si layers around the detection part of the sensor. Two types of low-stiffness suspensions for stress reduction and for wiring were formed in either the upper or the lower Si layer to connect both sides of the grooves. The experimental results showed that the ratio of zero output drift decreased by a factor of 8.9 by using the proposed SRS.

3-Axis Fully-Integrated Capacitive Tactile Sensor with Flip-Bonded CMOS on LTCC Interposer

This paper reports a 3-axis fully integrated differential capacitive tactile sensor surface-mountable on a bus line. The sensor integrates a flip-bonded complementary metal-oxide semiconductor (CMOS) with capacitive sensing circuits on a low temperature cofired ceramic (LTCC) interposer with Au through vias by Au-Au thermo-compression bonding. The CMOS circuit and bonding pads on the sensor backside were electrically connected through Au bumps and the LTCC interposer, and the differential capacitive gap was formed by an Au sealing frame. A diaphragm for sensing 3-axis force was formed in the CMOS substrate. The dimensions of the completed sensor are 2.5 mm in width, 2.5 mm in length, and 0.66 mm in thickness. The fabricated sensor output coded 3-axis capacitive sensing data according to applied 3-axis force by three-dimensional (3D)-printed pins. The measured sensitivity was as high as over 34 Count/mN for normal force and 14 to 15 Count/mN for shear force with small noise, which corresponds to less than 1 mN. The hysteresis and the average cross-sensitivity were also found to be less than 2% full scale and 11%, respectively.

A 2-axis gyroscope with a synchronously-driven dual mass

We report a detuned 2-axis yaw-and-roll gyroscope with a single sensor element. We designed and fabricated a novel structure composed of a synchronously driven dual mass and three types of supporting beams to limit the movable direction of each mass. The designed resonant frequencies agreed well with the measured values, which resulted in 2-axis detuning ratios of -0.7 and -2.2%. The fabricated gyroscope showed a cross-axis sensitivity of +/-2.7%. The test results demonstrated that the gyroscope simultaneously detects yaw and roll rates with low cross-axis sensitivity.

Sensor network serial communication system with high tolerance to timing and topology variations

This article presents the first wireline sensor network to use the delay window clock and data recovery (CDR) algorithm, which allows network nodes to communicate without high precision embedded clocks or a global clock. Changes in the topology of the network caused the transmission rates of the sensor nodes to vary. The mean data period measured on the network ranged from 738.79 ns to 811.25 ns and the standard deviation of periodic jitter (PJ) ranged from 0.7640 ns to 24.01 ns, depending on topology. Data sent from the sensor nodes was successfully recovered for all test cases without modifying the CDR, despite high PJ.