Browsing by Author "LEE, AC"

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A CAD CAM SYSTEM FOR 3D COORDINATE MEASURING DATA
(1990-12-01)
LEE, AC
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CHEN, DP
;
LIN, CL
;
交大名義發表
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機械工程學系
A CONSISTENT FINITE-ELEMENT FORMULATION FOR NONLINEAR DYNAMIC ANALYSIS OF PLANAR BEAM
(1994-01-15)
HSIAO, KM
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YANG, RT
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LEE, AC
;
交大名義發表
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機械工程學系
A co-rotational finite element formulation for the dynamic analysis of planar Euler beam is presented. Both the internal nodal forces due to deformation and the inertia nodal forces are systematically derived by consistent linearization of the fully geometrically non-linear beam theory using the d'Alembert principle and the virtual work principle. Due to the consideration of the exact kinematics of Euler beam, some velocity coupling terms are obtained in the inertia nodal forces. An incremental-iterative method based on the Newmark direct integration method and the Newton-Raphson method is employed here for the solution of the non-linear dynamic equilibrium equations. Numerical examples are presented to investigate the effect of the velocity coupling terms on the dynamic response of the beam structures.
A MODIFIED TRANSFER-MATRIX METHOD FOR ASYMMETRIC ROTOR-BEARING SYSTEMS
(1994-07-01)
KANG, Y
;
LEE, AC
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SHIH, YP
;
交大名義發表
;
機械工程學系
A modified transfer matrix method (MTMM) is developed to analyze rotor-bearing systems with an asymmetric shaft and asymmetric disks. The rotating shaft is modeled by a Rayleigh-Euler beam considering the effects of the rotary inertia and gyroscopic moments. Specifically, a transfer matrix of the asymmetric shaft segments is derived in a continuous-system sense to give accurate solutions. The harmonic balance method is incorporated in the transfer matrix equations, so that steady-state responses of synchronous and superharmonic whirls can be determined. A numerical example is presented to demonstrate the effectiveness of this approach.
A MODIFIED TRANSFER-MATRIX METHOD FOR LINEAR ROTOR-BEARING SYSTEMS
(1991-09-01)
LEE, AC
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KANG, Y
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LIU, SL
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機械工程學系
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Department of Mechanical Engineering
The steady-state responses of linear flexible rotor-bearing systems are analyzed by the modified transfer matrix method. The transfer matrix has the advantage of solving the problems in frequency domain with fixed matrix size. This makes the method more economical in analyzing a large degree-of-freedom rotor system than many time-marching integrating methods. In this paper, the modifications of transfer matrix method include that the transfer matrix of shaft is derived from the "continuous system" concept instead of conventional "lumped system" concept, and the paper tries to extend the transfer matrix method to fit synchronous elliptical orbit and nonsynchronous multi-lobed whirling orbit. To demonstrate the applications of the method, three examples are presented; two synchronous and one nonsynchronous.
A NEW AUTOREGRESSIVE METHOD FOR HIGH-PERFORMANCE SPECTRUM ANALYSIS
(1989-07-01)
LEE, AC
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
;
Department of Mechanical Engineering
A NOVEL CONTROL ALGORITHM FOR RAPID AND PRECISE POSITIONING
(1992-12-01)
SHIEH, YS
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LEE, AC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper investigates the positioning technology of a control system using an optimal control method. In this method, the control algorithm is based on minimization of a quadratic performance index, which consists of the position error and the weighted derivative of the error during a specific time interval. Minimization of this index allows us to obtain the optimal step control input command. It is shown that the control algorithm is efficient for positioning and simple for on-line implementation. The stability of the step control system is analyzed by the root locus method, and a means of selecting both the sampling period and the weighting matrix according to the specifications of the system is presented. Comparisons of the proposed control algorithm with bang-bang control and the optimum regulator problem are made. Also, a track-seeking servo control system of an optical disk driver is used to illustrate application of the proposed control method.
ACTIVE CONTROL OF AN ASYMMETRICAL RIGID ROTOR SUPPORTED BY MAGNETIC BEARINGS
(1992-11-01)
FAN, YH
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CHEN, ST
;
LEE, AC
;
交大名義發表
;
機械工程學系
Vibration control of a horizontal rotor with an asymmetrical moment of inertia is investigated. A linear optimal control system is developed to stabilize and control the rotor system by using the mathematical model of a rotor system expressed in the rotating coordinates. An approximated dynamical equation of a long rotor system is derived and used to obtain the compensator in analytical form (which saves much computational effort in control design), and is particularly useful in hardware implementation. Simulation results show the efficiency of the proposed strategy. The influences of weighting matrices and the effects of the asymmetrical moment of inertia on system performance for different controllers are also assessed.
ADAPTIVE-CONTROL OPTIMIZATION IN END MILLING USING NEURAL NETWORKS
(1995-04-01)
CHIANG, ST
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LIU, DI
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LEE, AC
;
CHIENG, WH
;
交大名義發表
In this paper, we propose an architecture with two different kinds of neural networks for on-line determination of optimal cutting conditions. A back-propagation network with three inputs and four outputs is used to model the cutting process. A second network, which parallelizes the augmented Lagrange multiplier algorithm, determines the corresponding optimal cutting parameters by maximizing the material removal rate according to appropriate operating constraints. Due to its parallelism, this architecture can greatly reduce processing time and make real-time control possible. Numerical simulations and a series of experiments are conducted on end milling to confirm the feasibility of this architecture.
AN INVESTIGATION OF THE CHARACTERISTICS OF ELECTROMAGNETIC BEARINGS USING THE FINITE-ELEMENT METHOD
(1994-10-01)
HSIAO, FZ
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LEE, AC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
The load capacity of EMBs with a restricted air gap is usually small in comparison with that of traditional ball bearings. One possible way to overcome this limitation is to increase the operation field strength of EMBs; however, this approach unavoidably involves nonlinear characteristics of EMBs. This paper investigates the nonlinear behavior of two commonly used types of EMBs by using the finite element method, in which the nonlinear relation of the B-H curve, the flux leakage, and the fringing effect are taken into account. The behavior of the EMBs under different bias currents and gap lengths is investigated, as are the effects of geometric parameters on the bearing characteristics. The results of the paper provide a useful guide for designing EMBs when using their nonlinear characteristics.
ANALYSIS AND TESTING OF MAGNETIC BEARING WITH PERMANENT-MAGNETS FOR BIAS
(1994-12-01)
LEE, AC
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HSIAO, FZ
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KO, D
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交大名義發表
;
機械工程學系
Active magnetic bearings constructed with electromagnets only are usually bulky and power-consuming This shortcoming can be remedied by adopting permanent magnets as the source of bias flux. Satisfactory results achieved by using rare-earth permanent magnets substantiate the feasibility of using permanent magnet bias in magnetic bearings. In this paper, an analytic model for permanent-magnet-biased magnetic bearings is presented. The static characteristics of a prototype are tested and compared with values estimated using this model. Manufacturing the prototype and subsequent testing offer some technological information which is important for future improvements.
ANALYSIS OF CHATTER VIBRATION IN A CUTTER-WORKPIECE SYSTEM
(1991)
LEE, AC
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LIU, CS
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CHIANG, ST
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交大名義發表
;
機械工程學系
The phenomenon of chatter vibration in milling has been investigated by many authors, but the consideration of workpiece has never been paid any attention to. In this paper, this defect has been excluded by involving workpiece dynamic effect on chatter vibration. A general form of time domain simulation and a simplified form of frequency domain analysis referred as circle criterion will be proposed to examine such a system. The new phenomenon of chatter vibration is derived by both of these methods and experiments also demonstrate the validity of this new phenomenon.
ANALYSIS OF CHATTER VIBRATION IN THE END MILLING PROCESS
(1991)
LEE, AC
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LIU, CS
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper continues the work of a previous paper by the authors. A different approach is applied, which adopts frequency domain analysis by linearizing the nonlinear equations to investigate the dynamic behavior in the milling process. A new relationship among the limiting axial depth of cut, workpiece fundamental natural frequency and spindle speed is constructed, and the obtained stable region is also consistent with that of the previous paper.
ANALYSIS OF CUTTING FORCES IN BALL-END MILLING
(1995-01-01)
CHIANG, ST
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TSAI, CM
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LEE, AC
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機械工程學系
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Department of Mechanical Engineering
A cutting force model for ball end milling is developed, the model being based mainly on the assumption that the cutting force is equal to the product of the cutting area and the specific cutting force. The formulation of the cutting area is derived from the geometry of the mill and the workpiece, whilst the specific cutting force is obtained by third-order curve-fitting of data measured in experiments. The model established in this paper predicts the cutting forces in ball-end milling much more accurately than to previous models.
COLLOCATED SENSOR ACTUATOR POSITIONING AND FEEDBACK DESIGN IN THE CONTROL OF FLEXIBLE STRUCTURE-SYSTEM
(1994-04-01)
LEE, AC
;
CHEN, ST
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper presents a new control design method for the control of flexible systems that not only guarantees closed-loop asymptotic stability but also effectively suppresses vibration. This method allows integrated determination of actuator/sensor locations and feedback gain via minimization of an energy criterion, which is chosen as the integrated total energy stored in the system. The energy criterion is determined via an efficient solution of the Lyapunov equation and minimized with a quasi-Newton or recursive quadratic programming algorithm. The prerequisite for this optimal design method is that the controlled system be asymptotically stable. This study shows that when the controller structure is a collocated direct velocity feedback design with positive definite feedback gain, the number and placement of actuators/sensors are the only factors needed to determine necessary and sufficient conditions for ensuring closed-loop asymptotic stability. The application of this method to a simple flexible structure confirms the direct relationship between our optimization criterion and effectiveness in vibration suppression.
COMPUTER CLASSIFICATION OF THE PCG WAVE-FORM
(1990-03-01)
LEE, AC
;
CHOU, JS
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
DECENTRALIZED CONTROL OF A ROTOR SYSTEM SUPPORTED BY MAGNETIC BEARINGS
(1995-03-01)
FAN, YH
;
LEE, AC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
The controller design for a permanent/electromagnetic magnetic bearing system that suspends a high-speed rigid horizontal rotor is investigated. The key points to ensure the stability of a rotor using this type of magnetic bearing are discussed. To facilitate implementation, a decentralized state feedback algorithm is proposed to stabilize the inherently unstable magnetic suspension system. Experimental results for the controlled system show that the system operates well at rotor speeds of up to 10,000 rpm.
DESIGN FOR MANUFACTURING THE ELASTIC PIVOTS WITH SPECIAL REFERENCE TO MANUFACTURING ERROR
(1994-11-01)
YANG, YN
;
CHENG, WH
;
LEE, AC
;
交大名義發表
;
機械工程學系
The stiffness of an elastic pivot, a kind of torsional hinge, must usually be small in the direction of axial rotation and high in all other directions. In some applications, such as the gimbal suspension of the tuned gyroscope in an inertial guidance system, the size of the elastic pivot is small, and consequently the pivot becomes very sensitive to machining error. In this paper, we model the machining error in terms of the position error and roll-pitch-yaw angle error of the electrode in the electric discharge machining process. In the corresponding design problem, we recommend design procedures that allow a compromise between product performance and manufacturability. This paper introduces different types of elastic pivots, analyzes machining error due to machining inaccuracy, and treats the shape optimization. We believe that the design-for-manufacturability methodology developed here will be helpful in the design of many other precision mechanical components.
EFFECTIVE ACTIVE DAMPING DESIGN FOR SUPPRESSION OF VIBRATION IN FLEXIBLE SYSTEMS VIA DISLOCATED SENSOR ACTUATOR POSITIONING
(1994-06-01)
CHEN, ST
;
FAN, YH
;
LEE, AC
;
交大名義發表
;
機械工程學系
In this paper we present a new controller design method that effectively suppresses vibration in flexible systems. The method allows integrated determination of sensor/actuator locations and feedback gain via minimization of an energy criterion which represents the integrated total energy stored in the system. This energy criterion is characterized by an effective representation of vibration, determined via an efficient solution of the Lyapunov equation and minimized with a quasi-Newton or recursive quadratic programming algorithm. The application of this method to a simple flexible structure confirms the direct relationship between our optimization criterion and effectiveness of vibration suppression.
ESTIMATION OF LINEARIZED DYNAMIC CHARACTERISTICS OF BEARINGS USING SYNCHRONOUS RESPONSE
(1995-02-01)
CHEN, JH
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LEE, AC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper presents a new method for estimating linearized dynamic characteristics of bearings using a priori information about the rotor. The rotor-bearing systems considered here are composed of a flexible shaft, which may be changed stepwise along the axial direction, and multiple rigid disks supported on anisotropic bearings. The main feature of this estimation technique is that it eliminates the need to measure the external input force. Since the system considered here is driven by an unbalance force, the steady state of the rotor will contain only a synchronous frequency component. By applying a Fourier transform to the measured displacement, we can obtain the coefficients of the sine and cosine terms with respect to the synchronous frequency. Finally, we formulate the normal equation by using the relations between these coefficients and the known system parameters; the characteristics of the bearings are then estimated by the least-squares method. The theoretical development of the method is presented together with simulation and experimental results.
INVESTIGATION ON THE STEADY-STATE RESPONSES OF ASYMMETRIC ROTORS
(1992-04-01)
KANG, Y
;
SHIH, YP
;
LEE, AC
;
交大名義發表
;
機械工程學系
This paper is to generalize the previous work by utilizing finite element formulation to accommodate the effects of both deviatoric inertia and stiffness due to asymmetry of flexible shaft and disk. A Timoshenko beam element is employed to simulate rotor-bearing systems by taking the gyroscopic moment, rotary inertia, shear deformation of shaft and, asymmetry of disk and shaft into account. Internal damping is not included but the extension is straightforward. Eulerian angles are used to describe the orientations of shaft element and disk, by which, in opposite to the vectorial approach, the mathematical formulation will be symmetric for angular displacements in two directions. The effects of the angle between the major axes of shaft and disk, deviatoric inertia of the asymmetric shaft, and characteristics of bearing on synchronous critical and subcritical speeds are estimated in conjunction with the harmonic balance method. Numerical examples show that the resonant speeds, at which peak responses occur, change due to various angles between major axes, asymmetry of shaft, stiffness, and damping of bearing.