Browsing by Author "Liu, T. S."

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A bionic approach to mathematical modeling the fold geometry of deployable reflector antennas on satellites
(2014-10-01)
Feng, C. M.
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Liu, T. S.
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交大名義發表
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機械工程學系
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National Chiao Tung University
Inspired from biology, this study presents a method for designing the fold geometry of deployable reflectors. Since the space available inside rockets for transporting satellites with reflector antennas is typically cylindrical in shape, and its cross-sectional area is considerably smaller than the reflector antenna after deployment, the cross-sectional area of the folded reflector must be smaller than the available rocket interior space. Membrane reflectors in aerospace are a type of lightweight structure that can be packaged compactly. To design membrane reflectors from the perspective of deployment processes, bionic applications from morphological changes of plants are investigated. Creating biologically inspired reflectors, this paper deals with fold geometry of reflectors, which imitate flower buds. This study uses mathematical formulation to describe geometric profiles of flower buds. Based on the formulation, new designs for deployable membrane reflectors derived from bionics are proposed. Adjusting parameters in the formulation of these designs leads to decreases in reflector area before deployment. (C) 2014 IAA. Published by Elsevier Ltd. All rights reserved.
A graph-theory approach to designing deployable mechanism of reflector antenna
(2013-06-01)
Feng, C. M.
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
The objective of this paper is to present an exhaustive search method for designing new deployable mechanisms of reflector antennas. The procedure is based on the graph theory and a flow value method. The mechanism is composed of links and joints. Connections between links are represented by using the graph theory. Rules representing design criteria and the flow value method based on load flow are taken into account to evaluate and select mechanisms among those that are enumerated in the database. Finally, this study presents a deployable mechanism that transmits load the most efficiently. (C) 2013 IAA. Published by Elsevier Ltd. All rights reserved.
A miniature generator using piezoelectric bender with elastic base
(2011-10-01)
Li, W.
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Liu, T. S.
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Hsiao, C. C.
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機械工程學系
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Department of Mechanical Engineering
Nowadays green energy devices such as vibration generators attempt to harvest energy from environment. A lot of studies dealing with vibration generators put emphasis on mechanism designs or power generation methods, but few on lowering the resonant frequency of power generation systems. This study proposes that elastic bases attached to vibration generators can lower natural frequencies, so as to make natural frequencies closer to ambient vibration frequency. Therefore, this study investigates miniature electric generators consisting of piezoelectric benders and elastic bases. To install the elastic base, this work uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and a vibration source to make the resonant frequency of piezoelectric benders close to the frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. Accordingly, more electric power can be generated from piezoelectric generators using an elastic base with appropriate mass and stiffness. According to experimental results, using an elastic base increases 376 times generated power compared with no elastic base. In the presence of the elastic base, the power increases 132% when a point mass is added. (C) 2011 Elsevier Ltd. All rights reserved.
A NOVEL BRUSHLESS PERMANENT MAGNET MOTOR FOR ELECTRIC SCOOTERS
(2014-01-01)
Liu, T. S.
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Chung, Y. C.
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機械工程學系
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Department of Mechanical Engineering
The purpose of this study is to design brushless permanent magnet DC motors for electric vehicles based on a pole-changing method. By generating a pulse when changing the number of poles, magnetization of magnets can be changed appropriately and the principle of pole-changing motors can be applied to permanent magnet machines This kind of machine not only retains the feature of permanent magnet machines in efficiency, but also acquires wide speed range. In this study, a pole-changing method using common windings is proposed and performance of brushless permanent magnet DC pole-changing motors is investigated. According to T-N curves, the proposed brushless permanent magnet pole-changing motor yields larger starting torque and wider speed range than motors with a fixed number of poles.
A tracking motion approach for a piezotube actuator in a disk drive subject to disk deformation and disturbance
(2007-10-01)
Chang, C. S.
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Liu, T. S.
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Tang, Y. C.
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機械工程學系
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Department of Mechanical Engineering
This study investigates the disk drive dynamics when a disk surface deforms and a disturbance force is exerted on a pickup head in near-field optical disk drives. Serving as an actuator, a piezotube is connected to the suspension of the pickup head. A model is constructed to investigate the pickup head dynamics. Equations of motion for focusing and track-following are derived in the presence of disk surface deformation and the disturbance force on the pickup head. A proportional and derivative control method is carried out in numerical examples. There exists a critical proportional gain that influences the number of resonances in the frequency spectra. Numerical results show that there is only one resonance or none in the frequency spectra when the proportional gain is larger than the critical proportional gain. Hence, the tracking error ratio becomes smaller than one within a wide frequency range, if few resonances appear in the frequency spectra.
Adaptive inverse control for the pickup head flying height of near-field optical disk drives
(2006-12-01)
Hsiao, C. C.
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Liu, T. S.
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Chien, S. H.
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機械工程學系
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Department of Mechanical Engineering
Near-field optical disk drives represent a promising technique for optical data recording to achieve an even larger storage density and capacity than DVD-ROM and Blu-ray disk drives. To realize near-field optics, unlike conventional optical disk drives, a flying pickup head is required. In this study, the pickup head consists of a suspension arm, a slider and a bimorph piezoelectric bender between the suspension arm and the slider. The dynamic model of the pickup head is identified using measurement, but the whole dynamics including both pickup head and interface dynamics between the disk and slider is unmodeled. Adaptive inverse control of robustness is developed to track the vibratory deformation of rotating optical disks, so that the flying height of a pickup head can remain stable in the presence of modeling error. Experimental results demonstrate that using the proposed method the pickup head can not only track disk deformation but also maintain the flying height.
Adaptive model-following control for slim voice coil motor type optical image stabilization actuator
(2008-04-01)
Yu, Hsing-Cheng
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
An autofocusing optical image stabilization actuator (AFOISA) will become standard equipment quickly in megapixel resolution mobile phone cameras (MPCs). A slim AFOISA composed of two orthogonal directions has been developed based on magnetic analysis and it is an effective solution to address image quality of a charged coupled device to compensate 10-20 Hz hand jitter in taking photos. However, environmental disturbance often occur irregular shake, such as when a photographer holds a MPC while walking or in a vehicle. Therefore, this paper develops an adaptive model-following control (AMFC) law including two proportional-integral-derivative controllers with position and speed feedback control, which is shown to be able to compensate for irregular shake of MPCs and to obtain fast response. Although irregular environmental shake cause parameter variation, an adaptation mechanism synthesizes an auxiliary input signal to assure that an AFOISA plant exactly behaves as a reference model. The time response by utilizing AMFC includes 30 ms settling time and 5 mu m steady state error without any overshoot. Furthermore, a compensatory force can quickly cancel irregular disturbance. As a result, the present slim AFOISA satisfies the optical demands of MPCs.
An optical lever approach to photodetector measurements of the pickup-head flying height in an optical disk drive
(2006-08-01)
Hsiao, C. C.
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Peng, C. Y.
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
In order to increase the storage capacity and the density of near-field optical disk drives, a flying pickup-head has to allow a slider to fly at a stable height above the disk surface with the use of near-field optics. Since both the precision of the track pitch and the flying height are of a nanometre scale, it is necessary to increase the motion accuracy of the pickup- head. In this study, a piezoelectric bender is used as an actuator of the pickup- head, and two quadrant photodetectors are used to sense the pickup- head displacement and the rotating disk deformation. Based on an optical lever method that magnifies a small displacement, the flying height variation of the pickup- head above the disk is measured. Further results show that using the proposed measurement method in the real-time control of flying height is feasible.
Automatic Control System for Thermal Comfort Based on Predicted Mean Vote and Energy Saving
(2015-01-01)
Ku, K. L.
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Liaw, J. S.
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Tsai, M. Y.
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Liu, T. S.
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機械工程學系
For human-centered automation, this study presents a wireless sensor network using predicted mean vote (PMV) as a thermal comfort index around occupants in buildings. The network automatically controls air conditioning by means of changing temperature settings in air conditioners. Interior devices of air conditioners thus do not have to be replaced. An adaptive neurofuzzy inference system and a particle swarm algorithm are adopted for solving a nonlinear multivariable inverse PMV model so as to determine thermal comfort temperatures. In solving inverse PMV models, the particle swarm algorithm is more accurate than ANFIS according to computational results. Based on the comfort temperature, this study utilizes feedforward-feedback control and digital self-tuning control, respectively, to satisfy thermal comfort. The control methods are validated by experimental results. Compared with conventional fixed temperature settings, the present control methods effectively maintain the PMV value within the range of and energy is saved more than 30% in this study. Note to Practitioners-For advanced control of unitary air conditioners in rooms, air conditioners may have to be retrofitted or connected with extra devices by wire connection, whose processes may be difficult for users, and inappropriate installation may damage original air-conditioning units. This study hence presents a noninvasive method for indoor thermal comfort with a wireless sensor network. The present method facilitates hardware implementation without changing interior devices of the air conditioner. The wireless sensor network measures temperature, air velocity, and humidity around occupants and further transmits temperature commands for air conditioner control. Based on the measured data, a PMV model is adopted to evaluate thermal comfort. Using an inverse PMV model with feedforward-feedback control and self-tuning control, respectively, this study aims to automatically maintain human thermal comfort as well as save energy. The ANFIS model and a particle swarm algorithm are used to solve the inverse PMV model and determine the thermal comfort temperature. Based on that temperature, feedforward-feedback control, and self-tuning control are used to determine appropriate temperature settings in the air conditioner so as to change the cooling capacity and maintain thermal comfort. Experimental results show that the present control method can maintain thermal comfort and saves 30% more energy than the conventional method.
Automatic measurement of payload for heavy vehicles using strain gages
(2008-06-01)
Yang, S. K.
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Liu, T. S.
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Cheng, Y. C.
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機械工程學系
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Department of Mechanical Engineering
Accidents caused by heavy vehicles have been increasing in recent years. This is mainly due to the fact that vehicle overloading results in steering difficulty and long braking distance. Therefore, this work aims to develop an automatic payload measurement for heavy vehicles, so that drivers and police officers can monitor vehicle payload while oil board the measured vehicle. For the ease of installation, high accuracy, and low cost, this work proposes to paste strain gages onto each leaf spring in vehicle suspensions. Based oil measured output voltages of bridge circuits in each suspension, the vehicle payload is calculated. Moreover, for promoting the accuracy of calculated payload, this work develops neural network models to account for nonlinearity in measurement. Finally, this work verifies model accuracy based oil experimental data. (C) 2007 Elsevier Ltd. All rights reserved.
Control experiment on pickup head flying above rotating disk
(2007)
Liu, T. S.
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Hsiao, C. C.
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機械工程學系
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Department of Mechanical Engineering
Near-field optical disk drives represent a novel technique for optical data recording, so as to achieve large storage density and capacity. Since the pickup head is very close to the optical disk, air bearing disturbance has significant effect on flying height control. The effect is not constant and dependent on various parameters. The previous method can not effectively cancel air bearing disturbance. By contrast, this study improves the adaptive inverse control method to overcome this problem. The proposed method decreases tracking error from 27% in the previous method to 13%.
Control experiment on pickup head flying above rotating disk
(2007)
Liu, T. S.
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Hsiao, C. C.
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機械工程學系
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Department of Mechanical Engineering
Near-field optical disk drives represent a novel technique for optical data recording, so as to achieve large storage density and capacity. Since the pickup head is very close to the optical disk, air bearing disturbance has significant effect on flying height control. The effect is not constant and dependent on various parameters. The previous method can not effectively cancel air bearing disturbance. By contrast, this study improves the adaptive inverse control method to overcome this problem. The proposed method decreases tracking error from 27% in the previous method to 13%.
Deformation of Multilayer Flexible Electronics Subjected to Torque
(2014-01-01)
Lee, Y. C.
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
Flexibility is one of remarkable characteristics of flexible electronics. Therefore, the analysis of flexible electronics deformation caused by external torques will help its design. In this work, analytical derivation is conducted for flexible electronics treated as multilayer structures. In experiments, an electric motor under computer control exerts a torque to generate torsion, whose twist angles are obtained by using both optical encoder measurement and theoretical calculation. Comparisons are made between experimental and theoretical results for bare PEN (polyethylene naphthalate) substrates of different sizes, multilayer PET (polyethylene terephthalate) substrates, and ITO (indium tin oxide)-coated PET substrates. Finally, a laser displacement sensor is used to measure the out-of-plane deformation for validating the proposed theoretical model.
Design and Experiment of Vibration-Based Miniature Generator
(2008)
Li, W.
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Liu, T. S.
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Chu, Y. C.
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Lin, Heng I.
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機械工程學系
To transform endless energy from ambient vibration into useful power. We scavenge mechanical energy and transfer into electrical energy by utilizing piezoelectric materials. We compare generators performance at different situations and then let electric energy be charged to a Ni-MH battery or a capacitor through a full wave rectifier. We also obtain resonance of piezoelectric benders by system identification which can be an important reference when designing the generator. This study proposes a novel mechanism comprising a mass-spring system and magnet repulsive force. According to finite element software and experimental result, below 5 Hz the generator absorbs vibration energy more easily. We have investigated the influence of the mass magnitude and obtained the optimum result of 2.7V and 0.379 mu w when the swinging amplitude of the motor is +/- 1.8 deg at swinging frequency of 3.96 Hz.
Design of a slim optical image stabilization actuator for mobile phone cameras
(2007)
Yu, Hsing-Cheng
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
Mechanical optical image stabilization actuator (OISA) will quickly become a standard feature in a high resolution mobile phone camera (MPC) and the quantity of MPC will exceed that of digital still cameras in several years. Whenever jitter arises from shaky hands or environment in taking photos, optical images projected upon an image sensor blur. Designing a slim OISA in MPC is an effective solution that addresses image quality. Therefore, this work presents a slim OISA utilized in MPC to compensate jitter form camera shake in taking photos. Two proportional-integral-derivative controllers based on transfer functions for dual axes of the slim OISA system in MPC obtained from system identification have been designed. The settling time of dual axes are less than 0.03 sec. Furthermore, a thrust ball bearing in this study has reduced the friction force between the movable and the stationary parts, so as to minimize the driving current to be less than 5 mA. Hence, the slim OISA has satisfied low power consumption requirement, and is also possible to reduce dimension in the MPC application. (c) 2007 WILE-VCH Verlag GmbH & Co. KGaA, Weinheim.
Design of Compact Linear Electromagnetic Actuator for Auto-Focusing in Phone Camera
(2011-12-01)
Lai, L. K.
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Tsai, C. L.
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
This paper proposes a novel linear electromagnetic actuator (LEA) for auto-focusing of compact phone cameras. An LEA consists of permanent magnets, iron cores, and coils, which are all magnetic circuit components. When coils are powered, induced magnetic field generates N and S poles around iron cores. Thus, unlike voice coil motors (VCMs) that employ the Lorentz force, the motion of the moving part in this study is arisen from a property-same poles repel each other while opposite poles attract each other. When compared to conventional VCM actuators in simulation results, the proposed LEA generates larger force, whereas using smaller current.
Dual-Axis Control Using Piezotube Actuator Based on Immune Algorithm
(2016)
Liu, T. S.
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Wu, P. J.
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機械工程學系
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Department of Mechanical Engineering
Piezoelectric actuators are widely employed in micropositioning and nanopositioning due to properties of high resolution, high bandwidth, and high stiffness. This study uses an immune algorithm to control a piezotube actuator. The immune algorithm includes antigens reorganization, antigen integration and appearance, the stimulation and suppression chains between antibodies in the immune system, and immune response of artificial immune system. This study treats runout disturbance as antigens in track following whereas environment disturbance as antigens in focusing. For control robustness, we define suitable antibodies to restrain antigens. In experiments, we treat disk deformation as antigens and proportional-integral-derivative (PID) gains as antibodies. Established by PID gains, immune database helps realize the immune algorithm. In track following experiment, the closed-loop response precision is 5%.
Edge Contrast Failure Analysis on Vision Angle of Human Eyes for Curve Displays
(2012-07-01)
Wen, Bor-Jiunn
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
For curve displays, the purpose of this study is to present edge contrast failure analysis (ECFA) method on the vision angle of human eyes. In order to analyze edge contrast of curve display images, a flexible cholesteric liquid crystal display is bent for different radii of curvature by using a flexible-characteristic inspection system. To simulate the human eye factors, a charge-coupled device colorimeter is utilized based on ECFA to analyze a maximum vision angle of human eyes with respect to curve displays under different radii of curvature. According to analysis results, a designer or maker of curve displays can design large-vision-angle and comfortable curve-display products for human being.
Flexible-characteristics inspection system for flexible substrates by using image feedback control
(2011-12-01)
Wen, Bor-Jiunn
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Liu, T. S.
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機械工程學系
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Department of Mechanical Engineering
The objective of this study is to present a new flexible-characteristic inspection system (FCIS) for measuring bending characteristics of flexible substrates under different bending conditions. In order to quantize bending conditions, charge-coupled device image feedback control is utilized to control radii of curvature of the flexible substrates. As a result, the new technique successfully measures electrical characteristics of flexible polyethylene terephthalate (PET)/indium tin oxide substrates up to 11,000 bending times by using FCIS. In addition, optical-transmittance characteristic measurement of PET/hexamethyldisiloxane substrates up to 5000 bending times under the same radius of curvature is implemented by using FCIS in this study. Inspection results of bending characteristics depicted on flexible displays help a designer or maker of flexible displays design useful and comfortable flexible electronic products. (C) 2011 Elsevier B.V. All rights reserved.
Fuzzy control based on reinforcement learning for voice coil motor
(2005)
Liu, T. S.
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Chang, W. K.
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機械工程學系
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Department of Mechanical Engineering
Dealing with voice coil motors, this paper presents reinforcement learning based fuzzy control, which incorporates characteristics of reinforcement learning into fuzzy control. Fuzzy control has excellent characteristics of dealing with model uncertainty and nonlinearity. To complement and improve fuzzy control, reinforcement learning is used to process rough feedback signals. This work constructs fuzzy rules based model based on input-output data of plants and tune fuzzy membership functions by reinforcement learning.