Kwangho Yoo

A 16-bit ultra-thin tri-axes capacitive microaccelerometer for mobile application

A 16-bit ultra-thin tri-axes capacitive microaccelerometer is presented, where tri-axes MEMS (microrlectromechanical systems) sensing elements, capacitive readout ASIC (application specific integrated circuit), and EEPROM (electrically erasable and programmable read only memory) are integrated to an ultra-thin LGA (land grid array) package. The input range and input-output non-linearity of x/y-axis channel is measured to be plusmn1.5 g and 0.35% FSO, respectively. The input range and input-output non-linearity of z-axis accelerometer channel are measured to be plusmn1.5 g and 0.19% FSO, respectively. The fabricated microaccelerometer system is suitable for many applications, including robots, game interfaces and mobile phone input interfaces.

Development of a MEMS-based Acceleration Sensing Module for Electronic Stability Program

This paper describes our development work for acceleration sensing modules for electronic stability program (ESP) systems. The MEMS-based accelerometer is fabricated using the unique sacrificial/bulk micromachining (SBM) process by us. The sensing module is designed to measure low level accelerations accurately and be stable in an automotive environment. This paper describes the accelerometer design and fabrication, electronic circuits and PCB design, module assembly, and performances of the developed sensing module. The developed sensing module offers analog voltage output with ±1.5g dynamic range, 0.05% non-linearity, 0.2mG resolution and l295㎷/g scale factor. The module includes a CAN2.0A interface and yields good experimental performances when implemented on a CAN test server.

Modeling and Simulation of the Microgyroscope Driving Loop using SPICE

A simulation model of vibratory capacitive microgyroscope and its driving loop is designed using SPICE. The vibratory microgyroscope is basically microelectromechanical system; therefore the simulation model should be expressed mechanical and electrical properties. To modelling the microgyroscope, the Analog Behavioral Model is used. In order to design a driving loop of vibratory microgyrosope, the the Barkhausen criteria is considered. The co-simulation of MEMS sensing element and its interface circuit is performed. The SPICE simulation model of the vibratory microgyrocope is designed, and the driving loop of the microgyroscope is simulated using the designed simulation model. The simulation results demonstrate the validity of the designed model and its interface circuit

Two-chip implemented, wafer-level hermetic packaged accelerometer for tactical and inertial applications

A two chip implemented, wafer-level hermetically packaged accelerometer is presented. The accelerometer core is fabricated using the SBM (sacrificial bulk micromachining) process. The fabricated accelerometer core accomplishes high performance, high yield and high reliability by the inherent high-aspect-ratio, footing-free advantages of the SBM process. In order to protect the accelerometer core from environmental changes, a wafer-level hermetic packaging process is performed by using glass-silicon anodic bonding. The capacitive detection circuit adopts an EEPROM trimmable architecture to reduce the die-to-die variations. The fabricated accelerometer has the noise equivalent acceleration resolution of 43 /spl mu/g, input range of /spl plusmn/10 g, Output nonlinearity of 0.1% FSO, scale factor of 130 mV/g, and 4-hr bias stability of 1.10 mg.

Multi-channel capacitive readout IC for MEMS inertial sensors

A multi-channel capacitive readout IC (integrated-circuit) for MEMS (microelectromechanical systems) inertial sensor is presented. A fully differential, chopper-stabilized SC (switched capacitor) 3-channel charge amplifier is designed. A digital demodulator and a decimator are used to prevent problems of conventional analog multipliers. Performance of the fabricated IC is evaluated with MEMS sensing elements.

Wafer-level Vacuum Packaged X and Y axis Gyroscope Using the Extended SBM Process for Ubiquitous Robot applications

Abstract A wafer-level vacuum packaged x and y axis gyroscope is fabricated on a (111) SOI wafer using the extended SBM (sacrificial bulk micromachining) process. The gyroscope uses vertically offset combs to resonate the proof mass in the vertical plane, and lateral combs to sense the Coriolis force in the horizontal plane. The extended SBM process is a simple two-mask process, and because all structural parts and combs are defined in one mask level, there is no misalignment in any structural parts or comb fingers. The silicon-to-glass anodic bonding carried out in low vacuum is used for the encapsulation of the fabricated gyroscope. The fabricated x and y axis gyroscope resolves 0.7 deg/sec angular rate, and the measured bandwidth is 22 Hz. The input range and the output linearity are over ± 80 deg/sec and 1.03 %FSO, respectively. The fabricated vacuum packaged x and y axis gyroscope without align error is important component at the high performance multiple-axis gyroscopes. The multiple-axis gyroscopes are used in many applications such as recently interested ubiquitous robot, car navigation, game controller, vehicle safety system, and so on.

Estimation of angular velocity and acceleration by using 2 linear acceleration sensors

Abstract This paper presents a method to measure angular velocity with two silicon-based MEMS acceleration sensors which have the resolution of 0.08 mg. This paper proposes measurement results using the technique to compensate the alignment error and estimate an angular velocity with two acceleration sensors fabricated by sacrificial bulk micromachining (SBM) process. The technique also estimates an angular velocity of a commercial cleaning robot, which has been tried to make the unit cost of production lower, by using two acceleration sensors without using a gyroscope.

MEMS-FABRICATED GYROSCOPES WITH FEEDBACK COMPENSATION

Abstract This paper presents a lead-lag compensator design for a MEMS-fabricated microgyroscope. The microgyroscope is basically a high Q system, thus the bandwidth is limited to be narrow. To overcome the open-loop performance limitations, a feedback controller is designed to improve the resolution, bandwidth, linearity, and bias stability of the microgyroscope. The feedback controller is applied to the z-axis microgyroscope fabricated by SBM process. In MATLAB simulations, resolution, bandwidth, input range, and bias stability of closed-loop system are improved from 0.0021 deg/sec to 0.0013 deg/sec, from 14.8 Hz to 115 Hz, from ±50 deg/sec to ±200 deg/sec, and from 0.0249 deg/sec to 0.0028 deg/sec, respectively.

MEMS-FABRICATED ACCELEROMETERS WITH FEEDBACK COMPENSATION

Abstract This paper presents a feedback-controlled, MEMS-fabricated microaccelerometer. The microaccelerometer has received much commercial attraction, but its performance is generally limited. To improve the open-loop performance, a feedback controller is designed and experimentally evaluated. The feedback controller is applied to the x/y-axis microaccelerometer fabricated by sacrificial bulk micromachining (SBM) process. Even though the resolution of the closed-loop system is slightly worse than open-loop system, the bandwidth, linearity, and bias stability are significantly improved. The noise equivalent resolution of open-loop system is 0.615 mg and that of closed-loop system is 0.864 mg. The bandwidths of open-loop and closed-loop system are over 100 Hz. The input range, non-linearity and bias stability are improved from ±10 g to ±18 g, from 11.1 %FSO to 0.86 %FSO, and from 0.221 mg to 0.128 mg by feedback control, respectively.