Browsing by Author "Lee, An-Chen"

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A 12-Step Sensorless Drive for Brushless DC Motors Based on Back-EMF Differences
(2015-06-01)
Wang, Samuel
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Lee, An-Chen
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機械工程學系
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Department of Mechanical Engineering
This paper presents a new 12-step sensorless drive for brushless dc motor based on back-electromotive force (back-EMF) differences, which are estimated from the disturbance observer (DOB) structure. Availability of rotor position information with a resolution of 30 degrees and commutation without phase shift are the advantages of using the back-EMF differences. Unlike the conventional methods that obtain part of the back-EMF signal from the manipulation of three phase voltages, the proposed DOB structure can access the entire back-EMF profile. By designing a proper low-pass filter in the DOB structure, the back-EMF difference can be well detected with lower sensor noise. Compensation of delay commutation introduced by the filter is also discussed. Experiment results showed that the proposed sensorless drive is capable of running the motor in lower speed, and performs better under different speed and load torque as compared with the conventional method.
A Current Index Approach to Compensate Commutation Phase Error for Sensorless Brushless DC Motors With Nonideal Back EMF
(2016-06-01)
Lee, An-Chen
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Wang, Samuel
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Fan, Chia-Juei
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機械工程學系
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Department of Mechanical Engineering
Commutation phase errors during implementation are inevitable in the sensorless drive of the brushless dc (BLDC) motor. This paper analyzed the current waveform during the conducting phase under commutation phase error and nonideal back electromotive force (EMF). The relation between the elapsed time of the commutation phase error with the current waveform, the supplied voltage, and the nonideal back-EMF is derived. Based on this relationship, a reliable optimization method for commutation phase errors compensation is presented. Such method is to minimize the elapsed time of the commutation phase error with robustness properties with respect to parameter variations. In such a way, the peak values of the current at the front and back of the current waveform at each conducting period become more identical, which leads to minimum torque ripple. A digital signal processor-based sensorless BLDC motor controller to implement the proposed method is developed to verify its effectiveness experimentally. Experiment results showed that the proposed sensorless drive is capable of running in different speed and load torque with good performance.
A hybrid controller design for bi-axial inverted pendulum system
(2009-03-25)
Chang, Long-Hong
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Lee, An-Chen
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機械工程學系
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Department of Mechanical Engineering
This study presents the use of Tustin's friction model and a disturbance observer (DOB) to improve the steady-state error (SSE) of a bi-axial inverted pendulum-cart system (IPCS). Furthermore, a hybrid controller contains a feedback linearization control for pendulum angle in the region of 3-12 degrees to enlarge the angle of operation and an H(infinity) control using loop shaping design procedure (LSDP) for cart position and pendulum angle in the region of 0-3 degrees to stabilize the IPCS, respectively. Experimental results reveal that the pendulum maximum angle of operation is improved from 7 to 12; the SSE of the angle of the pendulum is reduced from 0.85 to 0.1 degrees, and the SSE of the position of the cart is reduced from 10 to 1.4 mm. Experimental results are illustrated and films are provided at the web site http://hinfinity.myweb.hinet.net to show the effectiveness and robustness of the hybrid controller with Tustin's friction model and DOB compensation. Copyright (c) 2008 John Wiley & Sons, Ltd.
A modified transfer matrix method for the coupled lateral and torsional vibrations of asymmetric rotor-bearing systems
(2008-05-20)
Hsieh, Sheng-Chung
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Chen, Juhn-Horng
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Lee, An-Chen
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機械工程學系
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Department of Mechanical Engineering
For analyzing the coupled lateral and torsional vibrations of asymmetric rotor-bearing system, an extended transfer matrix extended from one of the symmetric system is developed. Rather than the conventional "lumped system", the asymmetric rotating shaft is modeled by the Timoshenko beam in a continuous-system concept. According to our analysis, for the asymmetric isotropic rotor-bearing system, the synchronous lateral mode will split; moreover, there is a 2 x lateral mode that does not appear on symmetric isotropic rotor-bearing systems. (c) 2008 Elsevier Ltd. All rights reserved.
A New Adaptive B-spline VFC Snake for Object Contour Extraction
(2010)
Nguyen, Hoang-Nam
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Lee, An-Chen
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機械工程學系
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Department of Mechanical Engineering
We propose a new adaptive B-spline VFC Snake model for object contour extraction. Bing Li et al. proposed vector field convolution (VFC) snake which has the advantages of superior noise robustness, reducing computational cost, and large capture range. However, it suffers from slow convergence speed due to large number of control points, as well as from difficulties in determining the weight factors associated to the internal energies constraining the smoothness of the curve. There is also no relevant criterion to determine the number of control points in VFC snake method. Our alternative approach expresses the curve as a non-uniform B-spline, in which fewer parameters are required and most importantly, internal energy calculation is eliminated because the smoothness is implicitly built into the model. A novel formulation of control points' movement estimation was established based on the least square fitting of non-uniform B-spline curve and VFC external force for the snake evolution process. A novel strategy of adding control points quickly matches the snake to desired complex shapes. Experimental results demonstrate the capability of adaptive shape description with high convergence speed of the proposed model.
A New Framework of Disturbance Observer with Vidyasagar's Structure
(2018-12-01)
Chen, Yu-Xian
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Huang, Ruei-Yu
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Chang, Shih-Chung
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Pan, Yi-Ren
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Lee, An-Chen
This paper proposes a novel two degree of freedom (TDOF) control structure: a combination of Vidyasagar's structure (VS) and the doubly coprime factorization based disturbance observer (DCFDOB). The DCFDOB-VS framework is aimed at providing a control structure and design procedure for a MIMO system with good characteristics of disturbance attenuation, tracking, and decoupling property. The structure can deal with stable/unstable and minimum phase/non-minimum phase plants. The advantage of the method is that two parameters can be designed for different purposes, independently. The parameter H stabilizes the system and improves tracking property. Once the parameter H has been designed, then the Q(Y) can be implemented via a parameter Q for rejecting disturbances and improving the system robustness.
Advanced parameter identification for a linear-motor-driven motion system using disturbance observer
(2009-10-01)
Pan, Yi-Ren
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Shih, Yi-Ti
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Horng, Rong-Hwang
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Lee, An-Chen
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機械工程學系
Disturbance observer (DOB) is generally introduced into motion control systems to eliminate undesired disturbances and plant uncertainty. The DOB is also used for system identification. This work presents a novel experimental identification algorithm using disturbance observer to identify inertia, viscous coefficient, and friction of linear-motor-driven motion system. A conventionally adopted algorithm for determining the inertia of the motion system based on orthogonal relations among system responses is modified and extended to estimate the viscous coefficient and the magnitude of Coulomb friction of the underlying system. The advantages of the proposed method are high convergence rate and only one experiment needed to evaluate the system parameters. The proposed algorithm is demonstrated to be workable by both simulation and experiment.
Advanced process control of the critical dimension in photolithography
(2008-01-01)
Wu, Chien-Feng
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Hung, Chih-Ming
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Chen, Juhn-Horng
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Lee, An-Chen
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機械工程學系
This paper describes two run-to-run controllers, a nonlinear multiple exponential-weight moving-average (NMEWMA) controller and a dynamic model-tuning minimum-variance (DMTMV) controller, for photolithography processes. The relationships between the input recipes (exposure dose and focus) and output variables (critical dimensions) were formed using an experimental design method, and the photolithography process model was built using a multiple regression analysis. Both the NMEWMA and DMTMV controllers could update the process model and obtain the optimal recipes for the next run. Quantified improvements were obtained from simulations and real photolithography processes.
Analyses and experimental confirmation of removal performance of silicon oxide film in the chemical-mechanical polishing (CMP) process with pattern geometry of concentric groove pads
(2011-01-12)
Wei, Chin-Chung
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Horng, Jeng-Haur
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Lee, An-Chen
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Lin, Jen-Fin
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機械工程學系
A Reynolds equation that considers both the smoothing hydrodynamic pressure and the pattern of surface topography at the polishing pads was used to solve the distribution of the hydrodynamic field. A three-body abrasion wear model for solving the removed thickness of silicon oxide films was also introduced to obtain the removal rate of SiO(2) film in a chemical-mechanical polishing (CMP) process. The suction hydrodynamic pressure field expands its region with increasing groove width and decreasing depth of grooves. The flow rate of the slurry was thus increased, and the removal rate also increased with an increased number of abrasive particles. The solid contact pressure was much higher than the hydrodynamic pressure. The three-body abrasion for the wear depth of a particle arises from the solid contacting pressure and is hence more important than the hydrodynamic pressure. The removal rate of the SiO(2) film was dominated by the number of abrasive particles, which was affected by the variation of the hydrodynamic pressure in addition to the wear depth controlled by the solid contact pressure. The thickness of the silicon oxide films removed increased with decreasing grooving width and depth. (C) 2010 Elsevier B.V. All rights reserved.
Analyses of a new four-facet drill
(2014-10-01)
Lee, An-Chen
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Danh-Tuyen Nguyen
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Wu, Guan-Ting
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機械工程學系
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Department of Mechanical Engineering
In this paper, a new four-facet drill was presented and analyzed. For evaluating the performance of the new and conventional drills, the geometrical analyses of the rake faces and flank surfaces as well as the prediction of cutting forces and torques were conducted. The results showed that the normal rake and clearance angles along the cutting lips of the new drill are always positive and a positive constant, respectively. In contrast, those of the conventional one are negative at certain points on cutting lips close to the drill axis and variable, respectively. Therefore, the cutting forces and torques of the new drill in drilling can be reduced as compared with the conventional one. The prediction of cutting forces and torques in drilling the workpiece made of plain-carbon steel (AISI1045) showed that the reductions of the total thrust force and torque along cutting lips for the new drill over the conventional drill are up to 50.12 and 26.54 %, respectively, and hence, the tool life of the new drill is expected to be longer than the conventional one\'s.
Combined Product and Tool Disturbance Estimator for the Mix-Product Process and Its Application to the Removal Rate Estimation in CMP Process
(2012-04-01)
Lee, An-Chen
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Kuo, Tzu-Wei
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Ma, Chung-Ting
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機械工程學系
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Department of Mechanical Engineering
In this paper, we proposed a control strategy: Combined Product and Tool Disturbance Estimator (CPTDE) which combines threaded double EWMA with the drift compensation scheme, to adaptively estimate the disturbance for a mix-product situation in semiconductor processes. This approach considers the disturbances are related to the combination of the specific product and the tool, and further separates the error into an intercept term and a drift term, where the former is related to the variation of products, whereas the latter is related to the interaction between the tools and the products. The proposed method continuously updates the intercept and drift terms to obtain the recipe for the next run. The simulation case studies, i.e., the fixed schedule process, the random schedule process, and the periodical schedule process, are conducted and the results show that CPTDE control scheme has best control performance when compared with three recently published control schemes. The method is also applied to the estimation of removal rate in mix-product CMP process. The results show that the proposed method has improvements over product-based EWMA control, CF-EWMA control and threaded PCC control by 9.52%, 2523.43% and 11.71% on average, respectively, for estimating removal rate of historical data in mix-product CMP process.
Coupled lateral and torsional vibrations of the micro-drilling spindle systems
(2016-11)
Lee, An-Chen
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Tien-Dat Hoang
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機械工程學系
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Department of Mechanical Engineering
In this research, the coupled lateral and torsional micro-drilling spindle system was analyzed by the finite element method (FEM). The Timoshenko beam finite element with five degrees of freedom at each node is applied to perform dynamic analysis of the system containing cylinder, conical symmetric elements, and flute asymmetric elements. The three-dimensional flute of the Union MDS drill with 0.1 mm diameter is defined by specifying the Cartesian coordinates of the specific points. In addition, the system model comprehensively includes the effects of continuous mass eccentricity, shear deformation, gyroscopic moments, and rotational inertia with external thrust force and torque during machining. In particular, the consideration of continuous mass eccentricity gives a more realistic model for system investigation. The Hamilton\'s equations of the system involving both symmetric and asymmetric elements were established and utilized to find shape functions of each element. The transient and steady-state lateral and torsional responses of drill point were estimated by Newmark\'s method. Simulation studies were attentively conducted to investigate the coupled lateral and torsional effect on the system vibration behavior. The results show that during design stage, the coupled lateral and torsional vibration associated with the above external forces should be considered carefully to prevent unexpected damage to the spindle system.
Current Integral Method for Fine Commutation Tuning of Sensorless Brushless DC Motor
(2017-12-01)
Lee, An-Chen
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Fan, Chia-Juei
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Chen, Guan-Hong
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機械工程學系
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Department of Mechanical Engineering
This paper presents a method for fine commutation tuning of brushless direct current (BLDC) motor. First, we analyze the phase current waveform under commutation error and nonideal back-EMF. From the relationship derived, we propose a feedback compensation method in combination with a sensored BLDC motor or any sensorless drive technique to adjust commutation instant by forcing the current integrals of the two half periods in one 60 degrees conducting period to be equal. The method is robust to variations in resistance and inductance, as well as to nonideal back-EMF, pushing the peak values of the current waveform at the front and back of each conducting period to be more identical. Simulations are presented and a digital signal processor (DSP)-based sensorless scheme contingent on a disturbance observer for back electromotive force (back-EMF) estimation in combination with the proposed control method is implemented to verify its effectiveness experimentally. The results show that proposed method is capable of running the motor at different speeds, load torque, and under the speed-varying operating condition with low levels of motor vibration and power consumption.
Design of a new micro single flute drill
(2014)
Lee, An-Chen
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Horng, Jeng-Haur
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Nguyen Danh Tuyen
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Hsiao, Kuo-Mo
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機械工程學系
A new micro single flute drill was presented in this study. For the convenience of developing a solid model, and doing a geometrical analysis, its geometry including the flute and flank surfaces is presented mathematically. According to the geometrical analysis, the normal clearance angles and normal rake angles along the cutting lip of the new micro dill are always invariant, and positive, respectively. Hence its cutting force in drilling is reduced. Furthermore, with only one main flute, the new micro drill gets stronger, and its cutting torque can be also decreased. Therefore it is expected that the tool life of the new micro drill is much longer than that of the conventional drill.
Dynamic Analysis of a Micro Drilling System by the Modified Transfer Matrix Method
(2016-01-01)
Lee, An-Chen
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Danh-Tuyen Nguyen
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機械工程學系
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Department of Mechanical Engineering
Normally, breakage is the main cause of failure of a micro drilling system, of which coupling effect of lateral and torsional displacements plays the most important role. This research developed a modified transfer matrix method to investigate the dynamics of a micro drilling system focusing on displacements induced by not only lateral, shear, torsional deformations, but also the coupling effect between lateral and torsional vibrations. The micro drilling system is modeled as pre-twisted rotating Timoshenko beam elements with a continuous-system concept. Each element includes components of linear bearings, axial drilling force, gyroscopic moments, and eccentricity. The overall transfer matrix of the system is developed to determine the state vector of the system including displacements and forces. Finally, a numerical example was presented, where the lateral and torsional displacements and critical speed of the micro drilling system at the micro drill's tip were presented.
Fabrication of an asymmetric Bragg coupler-based polymeric filter with a single-grating waveguide
(2011-05-23)
Chuang, Wei-Ching
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Huang, Yu-Tai
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Lin, Hui-Chi
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Lee, An-Chen
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機械工程學系
In this work, a first report on fabricating an asymmetric Bragg coupler-based filter on polymeric waveguides without input-waveguide grating was revealed. The fabrication process we developed was using holographic interference techniques, capillary effect, soft lithography, and micro molding process. The transmission dip of about. -9.2 dB and the 3 dB transmission bandwidth of about 0.125 nm were obtained from a filter. (C) 2011 Optical Society of America
Fabrication of optical filters based on polymer asymmetric Bragg couplers
(2009-09-28)
Chuang, Wei-Ching
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Lee, An-Chen
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Chao, Ching-Kong
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Ho, Chi-Ting
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機械工程學系
In this work, we successfully developed a process to fabricate dual-channel polymeric waveguide filters based on an asymmetric Bragg coupler (ABC) using holographic interference techniques, soft lithography, and micro molding. At the cross-and self-reflection Bragg wavelengths, the transmission dips of approximately -16.4 and -11.5dB relative to the 3dB background insertion loss and the 3dB transmission bandwidths of approximately 0.6 and 0.5nm were obtained from an ABC-based filter. The transmission spectrum overlaps when the effective index difference between two single waveguides is less than 0.002. (C) 2009 Optical Society of America
FCM based hybrid evolutionary computation approach for optimization power consumption by varying cars in EGCS
(2015-10-01)
Chen, Ta-Cheng
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Lee, An-Chen
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Huang, Shih-Lun
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機械工程學系
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Department of Mechanical Engineering
Elevators are the essential transportation tools in high buildings so that elevator group control system (EGCS) is developed to dynamically layout the schedule of elevators in a group. In this study, a fuzzy cognitive map (FCM) based computation approach by using particle swarm optimization (PSO) has been applied for estimating the minimum required elevators in EGCS so as to minimize the electricity consumption with predefined service quality. In literature, most of the studies were mostly focused on the scheduling strategy in order to have more efficient elevator dispatching or energy saving. However, the minimum numbers of elevators should be activated to sustain the required service quality. In other words, the maximum average waiting time for customers should be less than the predefined length of time while the minimum numbers of elevators are working in EGCS. The experimental results show that the performance of the proposed FCM based approach is feasible to estimate the required power consumption and average waiting time so as to decide the optimal numbers of elevators in EGCS. (C) 2015 Elsevier Inc. All rights reserved.
GA BASED HYBRID FUZZY RULE OPTIMIZATION APPROACH FOR ELEVATOR GROUP CONTROL SYSTEM
(2013)
Chen, Ta-Cheng
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Hsu, Yuan-Yong
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Lee, An-Chen
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Wang, Shiang-Yu
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機械工程學系
Elevators are the essential transportation tools in high buildings so that elevator group control system (EGCS) is developed to dynamically layout the schedule of elevators in a group. In this study, a fuzzy rule based intelligent EGCS optimized by genetic algorithm has been proposed where the rules with the corresponding parameters are generated optimally so as to maximize service quality. The experimental results show that the performance of our approach is superior to these of traditional approaches in the literature.
Generalization of all stabilizing compensators for finite-dimensional linear systems
(2007-11-01)
Huang, Yuan-Yong
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Lee, An-Chen
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機械工程學系
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Department of Mechanical Engineering
For finite-dimensional linear systems, the Youla-Kucera parameterization (YKP) with a Q parameter over RH infinity is assumed to satisfy the Diophantine identity. However, the stability is guaranteed if the Diophantine equation is the "U(RH infinity)" equality, but not if it is the "identity" equality. However, Vidyasagar's structure with an H parameter over U(RH infinity) is an observer-controller configuration that satisfies the Diophantine equation. This study discusses the deficiency of the Diophantine identity; expands the YKP using an H parameter over U(RH infinity), and expands the Vidyasagar's structure using a Q(v) parameter over RH infinity so that both of the expanded parameterizations satisfy the Diophantine equation and are equivalent for all stabilizing compensators. Moreover, an equation that relates to Q, Q(v), and H will be introduced to establish relationships among the YKP, Vidyasagar's structure and both expanded parameterizations. (c) 2007 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.