Hsing-Cheng Yu

Design of a voice coil motor used in the focusing system of a digital video camera

This paper raises a valid method to design a voice coil motor (VCM) used in the focusing system of a digital video camera (DVC). A better VCM performance, such as lower battery consumption, higher efficiency, and shorter focusing time, can be achieved by turning the diameter of a winding coil, the thickness of the magnet, and the winding spaces in a VCM.

Low power consumption focusing actuator for a mini video camera

A novel low power consumption autofocusing actuator in a mini video camera is constructed in accordance with the result of a systematic design procedure of voice coil motors (VCM). This paper emphasizes the position control of such a VCM. The position feedback signals are provided by a magnetoresistive (MR) encoder. The position estimation algorithm (PEA) is developed to precisely decode the MR signals for the position of the moving part of the VCM. Different postures change the loading of the moving part of the VCM, so that an adaptive model-following control system based on the PEA is proposed to compensate for the loading variation. The experiments verify the fast dynamic performance and high power efficiency of the VCM.

Improved Model-Free Predictive Current Control for Synchronous Reluctance Motor Drives

An improved model-free predictive current control (IMFPCC) method for synchronous reluctance motor (SynRM) drives is presented in this paper. The main advantages of previous MFPCC are that it does not require specific SynRM models and it requires neither motor parameters nor back-EMF estimations. However, this approach has two disadvantages: 1) two current measurements are required in each sampling period, which may lead to the detection of undesirable current spikes caused by instantaneous switching inside the inverter, and 2) an unresolved problem of stagnant current-variation updates, which undermines the prediction performance. This paper intends to eliminate these two drawbacks while retaining all the merits of MFPCC. The proposed IMFPCC is simple and easy to realize. Furthermore, no pulsewidth modulation (PWM) technique is required. A 32-bit microprocessor, TMS320F2809, is utilized to implement both the proposed IMFPCC and the model-based predictive current control (MBPCC) for a performance comparison. Experiment results are provided to validate the proposed method and verify its feasibility.

Adaptive Fuzzy Logic Proportional-Integral-Derivative Control for a Miniature Autofocus Voice Coil Motor Actuator With Retaining Force

This paper presents a miniature autofocus (AF) voice coil motor (VCM) actuator with retaining force in a restricted space that can be applied in an optical AF apparatus. A position encoder consisting of a permanent magnet (PM) and a Hall-effect sensor is used to detect magnetic signals; the displacement of the AF VCM actuator can be obtained from the encoder, thus enabling closed-loop control. The proposed miniature AF VCM actuator consists of a high-permeability magnetoconductive plate and a PM on another side to generate a retaining force when the exciting current is switched off. Using a 3-D finite-element analysis simulation and the Maxwell stress tensor method, the electromagnetic Lorentz force within a movable displacement was determined to be ~16 mN. Blur caused by variable force and load disturbance was observed in images captured during AF operation. This adaptive fuzzy proportional-integral-derivative (PID) control approach compensates for the nonuniform friction, disturbance variation, and even load changes of the movable part of the AF VCM actuator that occur when a subject is photographed in various positions. The adaption mechanism reduced control effort, despite the variable force and load disturbance, and exhibited fast dynamic performance and minimal steady-state error.

Adaptive model-following control for slim voice coil motor type optical image stabilization actuator

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 10–20Hz 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 ut...

Study of electromigration in thin tin film using edge displacement method

Threshold current density and other electromigration parameters of pure Sn films were measured using edge displacement method. Sn film with a thickness of 5000A was evaporated on a 1200‐A-thick Ti film on a Si substrate. Electromigration behavior was investigated under the current densities of 2.5×104–1.5×105A∕cm2 at room temperature (RT 27–32°C), 50, 75, and 100°C. Both needle-type and hillock-type whiskers grew in the anode end when the films were stressed at RT and 50°C, but only hillock-type whiskers were observed when they were stressed at 75 and 100°C. The electromigration rate increased linearly with the applied current density for the four stressing temperatures. The threshold current density (Jc) was measured to be 1.93×104, 9.65×103, 9.57×103, and 7.93×103A∕cm2 for RT, 50, 75, and 100°C, respectively. The measured activation energy was 0.32eV. In addition, the measured critical length of the Sn film was 18μm at RT and the products of DZ* were 1.95×10−10, 4.84×10−10, 1.27×10−9, and 1.99×10−9cm2∕s...

A Dual Notched Design of Radial-Flux Permanent Magnet Motors with Low Cogging Torque and Rare Earth Material

This paper proposes a dual notched design of radial-flux permanent magnet (PM) motors with gear-shaped structures on the PM and stator teeth aiming at lowering down cogging torque and rear earth material (REM). Due to the restriction on export quotas of REM, its cost is expected to rise drastically in the near future. The low cogging torque and REM in PM motor design, therefore, are of high significance. This paper presents a design taking a big step toward that direction. Four models with different mechanical angles and depths were designed. With the aid of 3-D finite element analysis and simulation, the one that best matched objectives was selected which resulted in percentage reduction of the cogging torque and REM up to 62.8% and 6.7%, respectively. In the transient simulation, the output torque of a dual notched PM motor compared with a normal structured one was reduced to 6.5% in average. A prototype was also fabricated to validate the design.

Sliding Mode Control Using Virtual Eigenvalue Method for Compact Optical Image Stabilization Actuators

The latest research in optical image stabilization actuators (OISA) focuses on improving the image quality of high resolution cameras in a photographing optical system (POS). The focal image blur is always caused of external and environmental jitter when pictures of an image sensor are acquired by photographers. Several works concerned for OISA are emphasized mainly OISA design methods; consequently, they are devoted to minimizing dimensions and maximizing driving magnetic force with low power consumption. Although two proportional-integral-derivative controllers and lead-lag compensators have been proposed to position dual axes of OISA in a POS, they lack robustness to compensate nonuniform friction, system uncertainty, and external disturbance. Therefore, this work aims at the sliding mode control (SMC) using virtual eigenvalue method to achieve fast time response and accurate position despite vibration from external jitter and friction of a compact OISA. The sliding surface can be reached in finite time to match disturbance. Accordingly, the SMC algorithm works well despite system uncertainty and external disturbance, and then the time response of simulation and experiment are matched. In consequence, the settling time of dual axes are converged within 0.2 s when the dual axes of movable platform of a compact OISA move at 0.5 mm stroke in a POS.

Development of a miniature axial-field spindle motor

This paper presents the development of a miniature axial-field spindle motor. Such a spindle motor could play a very important role in modern storage devices, which demand increasingly large storage capacity under limited physical space, especially for the miniature hard-disk drive or small-form-factor optical (SFFO) storage drive developments. In the present paper, an axial-field motor structure was employed to facilitate the design of a miniature spindle motor of a low profile height. In addition, the axial spoolless coil windings, which eliminate the cogging torque due to slot, serve as the electromagnetic exciting source.

Output Feedback Sliding Mode Control for a Linear Focusing Actuator in Digital Video Cameras

The output feedback sliding mode control offers an effective positioning method by robustness to parameter variation and disturbance rejection. This paper presents the output feedback sliding mode control based on a position estimation algorithm written in the microprocessor for use in the focusing control system of a digital video camera to achieve fast focusing response and accurate positioning despite vibration and friction of the movable part of the linear focusing actuator. The focusing performance by utilizing the output feedback sliding mode control includes a 60-ms setting time and 7-m steady-state error, respectively, which are only half and one-third of those in proportional-integral-derivative control when the movable part of the linear focusing actuator moves at a 5-mm stroke.