Browsing by Author "Ou, KY"

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Design and implementation of electromagnetic active control actuators
(2003-08-01)
Bai, MR
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Ou, KY
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機械工程學系
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Department of Mechanical Engineering
We present the modeling, parameter identification and design procedure of a linear voice-coil motor. A numerical simulation has been carried out to facilitate system integration. In particular, we use electromechanical analogy and the time-domain identification procedure with the eigensystem realization algorithm to predict the system response. In order to evaluate the performance of the voice-coil motor, we conducted an experimental investigation. Voice-coil motors mounted on a ball bearing housing are used for generating counter forces to cancel the transverse vibrations of a shaft. A controller is designed by using generalized predictive control. Multiple channel active control systems are implemented on the platform of a digital signal processor. Numerical and experimental results indicated that the designed actuators were effective in suppressing the periodic disturbances in rotors.
Experimental evaluation of adaptive predictive control for rotor vibration suppression
(2002-11-01)
Bai, MR
;
Ou, KY
;
機械工程學系
;
Department of Mechanical Engineering
An on-line active control technique for suppressing rotor vibration is proposed. Linear voice coil motors mounted on a ball bearing housing are used for generating counter forces to cancel the transverse vibrations of shaft due to imbalance, misalignment, and so forth. Controllers are designed by using the impulse response-based model predictive control (IMPC) and generalized predictive control (GPC). Recursive-least-square (RLS) method is employed for real-time system identification. Multiple channel active control systems are implemented on the platform of a digital signal processor (DSP). Experimental evaluation indicated that the proposed methods were effective in suppressing the periodic disturbances due to constant as well as variable rotor speed. In particular, GPC has achieved the most satisfactory performance in terms of vibration attenuation and convergence speed.
Head-related transfer function (HRTF) synthesis based on a three-dimensional array model and singular value decomposition
(2005-03-22)
Bai, MR
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Ou, KY
;
機械工程學系
;
Department of Mechanical Engineering
An external ear model based on a three-dimensional array beamformer is presented to synthesize the head-related transfer functions (HRTFs). The array coefficients are calculated by matching the measured HRTFs with a frequency-domain template. In light of the characteristics of human hearing, a non-uniform sampling technique is also devised to reduce the problem to a manageable size. The model-matching problem is then solved, by using singular value decomposition procedure. Numerical simulations are carried out to investigate various array configurations in relation to approximation performance. A subjective experiment of sound localization is undertaken to demonstrate the validity of the proposed technique. From the results, the proposed beamformer-based technique proves to be an effective method for modeling the HRTFs. (C) 2004 Elsevier Ltd. All rights reserved.
Synthesis of room responses using virtual source representation with application in reverberator design
(2005-04-01)
Bai, MR
;
Ou, KY
;
機械工程學系
;
Department of Mechanical Engineering
Reverberators play a vital role in immersive audio reproduction. Conventional methods for synthesizing reverberation generally are either computationally intensive or ineffective in producing a natural sensation of environmental settings. A synthesis technique is developed using discrete virtual source representation in an effort to overcome these difficulties. In comparison with the finite-element method (FEM) and the boundary-element method (BEM), which rely on complex numerical operations, the present method is based on a simple representation of the sound field with a distribution of discrete simple sources close to the boundary. The complex strengths of the virtual sources are then calculated by solving a frequency-domain least-squares problem. Parameters such as the geometry, size, and wall absorption of the room are naturally incorporated into the synthesis process. The filtering property of human hearing is also considered in a nonuniform sampling procedure to further simplify the computation. Numerical simulations are carried out for a rectangular room model and a concert hall to investigate the effects of room parameters on the synthesis performance. Subjective listening experiments demonstrate that the present technique is capable of rendering remarkable realism of reverberation.