Tae Sam Kang

High Assurance GPS Integrity Monitoring System Using Particle Filtering Approach

The reliability of a navigation system is one of the critical requirements for air or automotive navigation. In order to increase the reliability of the navigation system, failures or faults resulting from the malfunctions of the system should be detected and repaired to keep the system possessing high integrity. This leads to a need for developing high assurance GPS monitoring system which should be an absolutely necessary part of the system. The particle filter (PF) is a method based on Monte Carlo technique designed for nonlinear and non- Gaussian state estimation. In this paper, the PF is employed to GPS signal integrity monitoring. The primary objective of this research is over the safety in navigation with GPS and possibility that a GPS satellite transmits an erroneous navigation signal to the user. The monitoring system has to provide timely warnings to the user and indicates when it should not be used.

A Development of Miniaturized Piezoelectric Actuator System for Mobile Smart Structures

A smart material actuator is required for a smart structure having multifunctional performance. Among the smart material actuators, piezoelectric actuator is known for its excellent large force generation in broad bandwidth in a compact size. However it needs relatively large actuation voltage requiring a bulky hardware system. This study is mainly concerned to develop a self-powered miniaturized piezoelectric actuator driver (MIPAD) controlled by a radio controller for small sized piezoelectric smart structures. It can receive command from other microprocessors or a remote radio controller. We designed a real hardware and it demonstrated good performances even though the driving system was very small. The MIPAD is expected to minimize the weight and size of the piezoelectric actuator system and it can be easily embedded into mobile smart structures.

Piezo‐composite actuated control surface system for flying vehicle

Purpose – The purpose of this paper is to develop lightweight actuators in order to replace conventional hydraulic/pneumatic actuators and to apply the actuation system to a small flying vehicle.Design/methodology/approach – A new type of control surface using a piezo‐composite actuator for a small flying vehicle has been designed and manufactured. The piezo‐composite actuator is composed of a piezoelectric ceramic layer, a carbon/epoxy layer and glass/epoxy layers. Through this, the miniaturization and weight reduction of the actuation systems for flying vehicle can be achieved. A simple model of the control surface has been manufactured and evaluated through experiments.Findings – The performance test results showed that the developed actuator can produce stable angle of attack independent of the applied loading. A radio controller for the actuator was developed to control the motions wirelessly. It was found that the piezo‐composite actuator and its integrated controller system have a possibility to be...

Identification of a Fish-Like Robot Using Inertial Sensors

The efficiency of fish swimming dynamics has motivated researchers to develop fish-like robots. As a beginning step, a fish-like robot (boat) is built to simulate the fish swimming dynamics. By using data collected from inertial sensors, a suitable mathematical model explaining fish turning dynamics is obtained through system identification method. The identified model matches well with the experimental results and thus can be used for the design of controllers.

Development of a Bulk-Micromachined Single Crystal Silicon Gyroscope of Wide Operating Range at Atmospheric Pressure

In this paper, presented are the design and the fabrication of the novel bulk-micromachined gyroscope with its detection and control circuit. The proposed structure is designed to have good properties such as heavy proof mass, a large movement and high moving velocity of the proof mass at an operating frequency. Despite of an appropriate design of the proof mass and comb electrodes, the high-Q property and the capacitance measurement scheme inevitably bring on nonlinear property and limited bandwidth of the system. Moreover, temperature variation degrades the stability of the performance. In this paper, we adopt a feedback control scheme to achieve a linear output and a less sensitive operation to the temperature variation. Through experiments, it is confirmed that the designed gyroscope and the control circuit achieve performances of wide input range of 1,000 deg/sec and bandwidth of 80 Hz.

Oscillation Loop for a Resonant Type MEMS Accelerometer and Its Performance under Noisy Condition

This paper presents an oscillation loop for an INS (Inertial Navigation System) grade, surface micro-machined resonant type accelerometer. This resonant type sensor utilizes the electrostatic stiffness changing effect of an electrostatic actuator. This device produces a frequency output upon an applied acceleration. A closed loop system called self-sustained oscillation loop is prerequisite for its operation as a resonant accelerometer. A self-sustained oscillation loop induces the system’s dynamic states into its primary mode, thus keeps track of its resonant state under applied acceleration or perturbation. For this, a simple self-sustained oscillation loop is designed and the feature of the loop is analyzed in the viewpoint of nonlinear dynamic system. From the standpoint of feedback control system, both determination of resonance point and its stability analysis are required. In the actual system, which has several noise sources, noise can affect the output resonant frequency. We analyzed the effect of a noise on oscillation frequency. Finally, simulation and experimental result is given

Development of an Oscillation Loop for a Micromachined Differential Type Resonant Accelerometer and Its Performance

This paper presents a surface micro-machined differential resonant accelerometer (DRXL) by using the epitaxially grown thick polysilicon process. The proposed DRXL utilizes the electrostatic stiffness changing effect of an electrostatic torsional actuator. This device produces a differential digital output proportional to an applied acceleration. For a self-generated and self-sustained oscillation of the resonator, a feedback oscillation loop is designed, implemented, and applied to the DRXL chip. The oscillation loop is designed using an analytical result based on the describing function method. Using the implemented self-sustaining oscillation loop, pecifications of sensor performance are obtained by various performance tests. These results show quite an improved quality factor and resolution compared to that of the sensing device only. And we obtained more stable output frequency responses.

Design and Performance Test of Digital Rebalance Loop for MEMS Gyroscope

In this paper, a digital rebalance loop for MEMS gyroscope is designed and its performance test is performed. First, the system model of MEMS gyroscope is established by dynamic analysis. Then, the digital rebalance loop is designed using modern control technique. The performance of the digital rebalance loop is compared with that of conventional PID rebalance loop. Through frequency response analysis using MATLAB and experiments using a real MEMS gyroscope and digital controller, which is realized using digital signal processor (DSP), it is confirmed that the controller improves the performance of the gyroscope.

A Design of Navigation System Using Stratospheric Airships in South Korea

For a relatively small country like Korea, a radionavigation system using airships can be considered, which is to provide the navigation service utilizing the stratospheric airships that are deployed in the stratosphere at the altitude of around 20-23㎞, and which is an independent or a back-up radionavigation system other than current GPS or GLONASS. In this paper, a feasibility study on the constellation of stratospheric airships for the navigation system has been performed. A measure of a geometrical condition between a receiver and navigation transmitters. called the DOP (Dilution of Precision), determines the resulting positioning error of the navigation system, if the error of range measurement is predictable. Therefore, with assumption that the range measurement error of the stratospheric airship navigation system is quite similar to GPS. the several DOP values have been used to evaluate the performance of the navigation system with comparing with the DOP values of GPS as the reference values. To provide the position information of the navigation transmitters to users, a receiver cluster system fixed on the ground, called an IGPS (inverted GPS), is proposed, and the error is also evaluated using the DOP values. Five areas around five major cities in South Korea have been selected, and then by numerical simulations the DOP values are compared those of GPS to assess the performance of the proposed navigation system using stratospheric airships. The possible frequency bands have been proposed. and then link budget of the navigation transmitter has been analyzed for the proposed navigation system.

Development of a Micro Gyroscope Using Epitaxial Polysilicon and Its Performance Test

This paper presents a design and performance tests of in-plane gimbal-structured Z-axis gyroscope. The device is manufactured by conventional surface micro machining process using 15µm-thickness epitaxially grown polysilicon. The total size of the device is 4.8mm x 4.8mm in area including 1mm x 1mm core gyro structure and pads for wire bonding. It is designed as two-gimbaled structure which separates inner and outer gimbals. This leads two nearly identical modes of gyroscope, i.e. driving and sensing mode, to mechanically decoupled ones, resulting in enhanced performance. Experiments are accomplished through frequency analysis and dynamic tests using a detection circuit, a vacuum chamber and a rate table. Through experiments, it is confirmed that the designed gyroscope has 0.003 deg/sec resolution, 0.00095 deg/sec/ Hz noise equivalent density, 0.57 % FSO nonlinearity error and 0.02 deg/sec bias stability.