Sung Kyung Hong

Gain-Scheduled Complementary Filter Design for a MEMS Based Attitude and Heading Reference System

This paper describes a robust and simple algorithm for an attitude and heading reference system (AHRS) based on low-cost MEMS inertial and magnetic sensors. The proposed approach relies on a gain-scheduled complementary filter, augmented by an acceleration-based switching architecture to yield robust performance, even when the vehicle is subject to strong accelerations. Experimental results are provided for a road captive test during which the vehicle dynamics are in high-acceleration mode and the performance of the proposed filter is evaluated against the output from a conventional linear complementary filter.

Trajectory-Switching Algorithm for a MEMS Gyroscope

The motion of a conventional force-balancing controlled gyroscope in a mode-matched operation does not have sufficient persistence of excitation, and as a result, all major fabrication imperfections cannot be identified and compensated for. This paper presents an adaptive force-balancing control for a microelectromechanical-system z-axis gyroscope using a trajectory-switching algorithm. The proposed adaptive force-balancing control supplies additional richness of excitation to the internal dynamics of the gyroscope by switching the trajectory of the proof mass of the gyroscope, and it provides quadrature compensation, drive- and sense-axis frequency tuning, and closed-loop identification of the angular rate without the measurement of input/output phase difference. This algorithm also identifies and compensates the cross-damping terms which cause zero-rate output.

Oscillation Control Algorithms for Resonant Sensors with Applications to Vibratory Gyroscopes

We present two oscillation control algorithms for resonant sensors such as vibratory gyroscopes. One control algorithm tracks the resonant frequency of the resonator and the other algorithm tunes it to the specified resonant frequency by altering the resonator dynamics. Both algorithms maintain the specified amplitude of oscillations. The stability of each of the control systems is analyzed using the averaging method, and quantitative guidelines are given for selecting the control gains needed to achieve stability. The effects of displacement measurement noise on the accuracy of tracking and estimation of the resonant frequency are also analyzed. The proposed control algorithms are applied to two important problems in a vibratory gyroscope. The first is the leading-following resonator problem in the drive axis of MEMS dual-mass vibratory gyroscope where there is no mechanical linkage between the two proof-masses and the second is the on-line modal frequency matching problem in a general vibratory gyroscope. Simulation results demonstrate that the proposed control algorithms are effective. They ensure the proof-masses to oscillate in an anti-phase manner with the same resonant frequency and oscillation amplitude in a dual-mass gyroscope, and two modal frequencies to match in a general vibratory gyroscope.

Force control system design for aerodynamic load simulator

A dynamic load simulator which can reproduce on-ground the aerodynamic hinge moment of control surface is an essential rig for the performance and stability test of aircraft actuation system. The hinge moment varies widely in the flight envelope depending on the specific flight condition and maneuvering status. To replicate the wide spectrum of this hinge moment variation within some accuracy bounds, a force controller is designed based on the quantitative feedback theory (QFT). A dynamic model of load actuation system is derived, and verified through the experiment. The efficacy of QFT force controller is verified by simulation, in which combined aircraft dynamics, flight control law and hydraulic actuation system dynamics of aircraft control surface are considered.

Minimal-Drift Heading Measurement using a MEMS Gyro for Indoor Mobile Robots

To meet the challenges of making low-cost MEMS yaw rate gyros for the precise self-localization of indoor mobile robots, this paper examines a practical and effective method of minimizing drift on the heading angle that relies solely on integration of rate signals from a gyro. The main idea of the proposed approach is consists of two parts; 1) self-identification of calibration coefficients that affects long-term performance, and 2) threshold filter to reject the broadband noise component that affects short-term performance. Experimental results with the proposed phased method applied to Epson XV3500 gyro demonstrate that it effectively yields minimal drift heading angle measurements getting over major error sources in the MEMS gyro output.

Angular Rate Estimation Using a Distributed Set of Accelerometers

A distributed set of accelerometers based on the minimum number of 12 accelerometers allows for computation of the magnitude of angular rate without using the integration operation. However, it is not easy to extract the magnitude of angular rate in the presence of the accelerometer noises, and even worse, it is difficult to determine the direction of a rotation because the angular rate is present in its quadratic form within the inertial measurement system equations. In this paper, an extended Kalman filter scheme to correctly estimate both the direction and magnitude of the angular rate through fusion of the angular acceleration and quadratic form of the angular rate is proposed. We also provide observability analysis for the general distributed accelerometers-based inertial measurement unit, and show that the angular rate can be correctly estimated by general nonlinear state estimators such as an extended Kalman filter, except under certain extreme conditions.

LMI-based robust flight control of an aircraft subject to CG variation

This article presents a simple and effective design method for the single robust flight controller of a highly manoeuvring aircraft subject to centre of gravity (CG) variation in flight. This methodology is based on an linear matrix inequality (LMI) regional pole-placement design framework for the polytopic models for the CG variation ranges. The application of this method for a design of stability/control augmentation system for the longitudinal flight control system of a high-performance aircraft is shown. Simulation results show that the proposed LMI-based regional pole-placement design methodology robustly yields consistent performances with adequate Level 1 flying qualities over the entire CG variation range.

T-S FUZZY GAIN-SCHEDULED CONTROL BASED ON AFFINE PARAMETER-DEPENDENT MODEL WITH APPLICATION TO AIRCRAFT ROLL CONTROL

The prevalent method of synthesizing nonlinear aircraft control is gain-scheduled linear designs based on a set of linear time invariant (LTI) model. Although this approach has proven successful in numerous applications, it has distinct limitations when it is applied to highly nonlinear systems with insufficient number of design points. Thus the desire to continually improve performance with more efficient and systematic formal design methodology suggests the need for a new design paradigm. This paper presents an alternative gain scheduling method based on Takagi-Sugeno (T-S) fuzzy framework of affine parameter-dependent system (PDS) paradigm. This theoretical development is then specialized to the problem of synthesizing a large envelope roll control for a high maneuverable aircraft. Finally the resulting fuzzy gain scheduled controller is demonstrated via nonlinear simulations, and its performance is evaluated relative to that of the conventional gain-scheduled controller.