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In this note, a scheme for the vibration suppression of a translating string using a positive real (PR) transfer function is investigated. The transverse vibration of the string is controlled by hydraulic touch-rolls located at the right end of the string. The mathematical model of the system, which consists of a hyperbolic partial differential equation (PDE) describing the dynamics of the moving string and an ordinary differential equation (ODE) for the actuator dynamics, is derived by using Hamilton's principle for translating continua. The transfer function of the proposed boundary controller is a nonproper but PR function. The asymptotic stability of the closed-loop system in the presence of output disturbance is proved. Index Terms--Axially moving string, disturbance rejection, positive real (PR) function, robust boundary control, semigroup theory.

In mobile phones of multimedia era, microspeakers of high-quality sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical, acoustical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era. Index Terms--Broadband, finite-element method (FEM), magnetic circuit, microspeaker.

This paper describes an approach to design of acoustic devices, such as microspeaker and dynamic receiver, considering the acoustic characteristics improvement in IMT-2000 mobile phones. The analysis of a newly designed microspeaker considering mechanical, electrical, and magnetic coupling effects is performed using the finite-element method (FEM) and its validity is confirmed as well by experiments. Also, a statistical approach is suggested to identify a certain relationship between a mobile phone and a newly designed microspeaker. The approach is based on the Taguchi method and utilizes the orthogonal array for design of experiments (DOE). The concept of signal-to-noise (S/N) ratio is applied to evaluate the acoustic performance in mobile phones. Index Terms--Acoustic characteristics, coupling, finite-element method, IMT-2000, microspeaker, SPL, Taguchi method.

In this paper, a road adaptive modified skyhook control for the semi-active Macpherson strut suspension system of hydraulic type is investigated. A new control-oriented model, which incorporates the rotational motion of the unsprung mass, is introduced. The control law extends the conventional skyhook-groundhook control scheme and schedules its gains for various road conditions. Using the vertical acceleration data measured, the road conditions are estimated by using the linearized new model developed. Two filters for estimating the absolute velocity of the sprung mass and the relative velocity in the rattle space are also designed. The hydraulic semi-active actuator dynamics are incorporated in the hardware-in-the-loop tuning stage of the control algorithm developed. The optimal gains for the ISO road classes are discussed. Experimental results are included. [DOI: 10.1115/1.1434265] Keywords: Macpherson Strut Suspension, Modeling, Skyhook Control Semi-Active Damper, Gain Scheduling, Rapid Control Prototyping, Road Estimation

Asymptotic behavior of a partial state of a coupled ordinary and/or partial differential equation is investigated. It is specifically shown that if a signal x(t) is a solution to a dynamic system existing for all t [greater than or equal to] 0 in an abstract Banach space and is pth (p [greater than or equal to] 1) power integrable, then x(t) [approaches] 0 as t [approaches] [infinity]. The system is allowed to be nonautonomous and assumes the existence of a Lyapunov function. Since the derivative of the Lyapunov function is negative semidefinite, stability or uniform stability in the sense of Lyapunov would be concluded. However, this paper further asserts that the partial state which remains in the time derivative of the Lyapunov function converges to zero asymptotically. Index Terms - Adaptive systems, convergence, existence, time-varying system, uniqueness.

This paper presents a model reference adaptive control of a class of distributed parameter systems described by linear, n-dimensional, parabolic partial differential equations. Unknown parameters appearing in the system equation are either constant or spatially-varying. Distributed sensing and actuation are assumed to be available. Adaptation laws are obtained by the Lyapunov redesign method. It is shown that the concept of persistency of excitation, which guarantees the parameter error convergence to zero in finite-dimensional adaptive systems, in infinite-dimensional adaptive systems should be investigated in relation to time variable, spatial variable, and also boundary conditions. Unlike the finite-dimensional case, in infinite-dimensional adaptive systems even a constant input is shown to be persistently exciting in the sense that it guarantees the convergence of parameter errors to zero. Averaging theorems for two-time scale systems which involve a finite dimensional slow system and an infinite dimensional fast system are developed. The exponential stability of the adaptive system, which is critical in finite dimensional adaptive control in terms of tolerating disturbances and unmodeled dynamics, is shown by applying averaging. A numerical example which demonstrates an averaged system and computer simulations are provided.

New conditions for the exponential stability for both linear nonautonomous finite and a class of infinite-dimensional systems described by parabolic partial differential equations (PDE's) are derived. The results for the parabolic systems are derived via semigroup approach.

In this paper we derive delay-independent exponential stability conditions for linear/nonlinear time-varying discrete delay systems. Since these conditions are of delay-independence and easily verifiable, they may provide handy tools for the stability analysis.

In the first part (1) of this work the conditions for the existence of the stabilizing vibrations for a class of distributed parameter systems governed by parabolic partial differential equations with Neumann boundary conditions were derived, and the guidelines for the choice of the vibration parameters that ensure stabilization were given. The present note addresses the transient behavior analysis of vibrationally controlled systems of the same class.

For cellular phones, high-performance microspeakers with broader frequency range are essential parts to realize various multimedia functions such as MP3 playback, speaker phones, and 64 polyharmonic melody. The operating frequency range of conventional microspeaker ranges is from 800 Hz to 10 kHz. It is very difficult to generate a lower frequency sound below 800 Hz in microspeakers. Therefore, it is necessary to develop woofer microspeakers that make higher sound pressure level (SPL) at a lower frequency band. However, in the case of microspeakers, it is hard to have good performance at a lower frequency range due to size. In this paper, a diaphragm is introduced which is attached to a copper plate to make high performance at a lower frequency range. The woofer microspeaker is developed to have high flux density by magnetic circuit with two-magnet. Index Terms--Cellular phone, magnetic circuit, sound pressure level (SPL), woofer microspeaker.

Harmonic distortion due to uneven magnetic fields is becoming more important in mobile phones to generate high quality sound. In this paper, analysis of sound pressure level and reduction of harmonic distortion is presented by considering mechanical and magnetic coupling effects. It shows that high-performance microspeakers with lower harmonic distortion is realizable with proper magnetic circuit design. Experimental verification is also followed for dual magnet-type microspeakers. Index Terms--Harmonic distortion, magnetic circuit, microspeaker, mobile phone.

Byline: Hyun-Chul Sohn, Kyung-Tae Hong, Keum-Shik Hong, Wan-Suk Yoo In this paper, a road-adaptive LQG control for the semi-active Macpherson strut suspension system of hydraulic type is investigated. A new control-oriented model, which incorporates the rotational motion of the unsprung mass, is introduced. A semi-active suspension controller adapting to road variations is proposed. First, based on the extended least squares estimation algorithm, a LQG controller adapting to the estimated road characteristics is designed. Through the computer simulations, the performance of the proposed semi-active suspension is compared with that of a non-adaptive one. The results show better control performance of the proposed system over the compared one.

Byline: Deok-Ho Kim, Kyung-Jinn Yang, Keum-Shik Hong, Jin-Oh Hahn, Kyo-Il Lee In this paper, a robust adaptive control scheme with an intelligent supervisor for vehicle powertrain systems is investigated. The control objectives are to provide smooth shift transients for passenger comfort and to improve component durability. The reaction carrier speed and the turbine speed during the inertia phase are controlled to track their desired speeds, respectively. The boundedness of all signals in the closed loop system and the convergence of the reaction carrier speed error near to zero are guaranteed by applying the Lyapunov stability analysis. The adaptive compensation controller with an intelligent supervisor is implemented to keep the turbine speed error near to zero and the deviation of the shift duration within an allowable range. The proposed control algorithm is implemented and evaluated on an experimental test setup.