So-Nam Yun

A study on energy saving algorithm of electro-pneumatic regulator with modified PWM driven method

The development of an accurate and energy saving electro-pneumatic regulator that may be applied to a variety of practical pressure control applications is described in this paper. A novel modified pulse width modulation (MPWM) valve pulsing algorithm allows the electro-pneu-matic regulator to become energy saving system. A comparison between the system response of conventional PWM algorithm and that of the modified PWM (MPWM) algorithm shows that the control performance is almost the same, but energy saving is greatly improved by adopting this new MPWM algorithm. The effectiveness of the proposed control algorithm is demonstrated through experiments with various reference trajectories.

A study on high-output piezoelectric micropumps for application in DMFC

In order to supply liquid fuel in DMFC (Direct Methanol Fuel Cell) system, a small but high-output micropump is needed. This study presents a design concept, fabrication and experimental results of the newly devised piezoelectric micropump by using resonance and fluid inertia. The micropump consists of a resonantly-driven pumping unit, an inlet check valve, and a pipeline element with a small diameter employed in an outlet. The resonance mechanism is used to oscillate the pumping chamber. It simply magnifies a small displacement of the used multilayer-piezoelectric actuator. The fluid inertia effect uses a fast flow through a narrow pipeline element employed instead of the outlet check valve. First, an analysis on each element such as a diaphragm and a check valve is performed. Based on the obtained analysis results, a prototype micropump is designed, and fabricated. Then, pumping characteristics such as frequency-dependent displacement, and flow rate without load pressure are experimentally investigated. Finally, a refabrication of the micropump is carried out to improve load characteristics, and the obtained experimental results are presented and discussed.

Energy Harvesting Strategy Using Piezoelectric Element Driven by Vibration Method

This study demonstrates a method for harvesting the electrical power by the piezoelectric actuator from vibration energy. This paper presents the energy harvesting technique using the piezoelectric element of a bimorph type driven by a geared motor and a vibrator. The geared motor is a type of PWM controlled device that is a combination of an oval shape cam with five gears and a speed controller. When using the geared motor, the piezoelectric element is size of 36L×13W×0.6H. The output voltage characteristics of the piezoelectric element were investigated in terms of the displacement and vibration. When using the vibrator, the electric power harvesting is based on piezoelectric effect and piezoelectric vibrator consists of a magnetic type oscillator, a cantilever, a bimorph actuator and controllers. Low frequency operating technique using piezoelectric vibrator is very important because normal vibration sources in the environment such as building, human body, windmill and ship have low frequency characteristics. We can know from this study results that there are many energy sources such as vibration, wind power and wave power. Also, these can be used to the energy harvesting system using smart device like piezoelectric element.

Design of a Piezoelectric-Driven Tilt Mirror for a Fast Laser Scanner

Recently, laser scanners have been used for laser processing such as cutting, welding, and grooving, especially in the automotive industry. The laser scanners need a high-speed driving to minimize cracks caused by thermal shock of brittle materials. Therefore, a novel laser processing system that is composed of a laser source and a piezoelectric-driven tilt mirror to control the reflection angle of the laser beam, and a stage equipped with the tilt mirror has been investigated. In this study, a piezoelectric-driven tilt mirror is designed and analyzed for scanning performance to achieve a beam spot of 30 µm, a pattern width of 1 mm, an overlap ratio of 70% of the circle area, and a scanning speed of 1 m/s. Then, structural analysis of the tilt mirror with three piezoelectric actuators is performed to determine the maximum reflection angle and resonance frequency. Finally, a prototype tilt mirror is fabricated and its basic characteristics are experimentally investigated and discussed.

A study on the small size PZT pump for cooling water circulation

In precision machinery systems for electronic devices, due to the generation of heat, cooling system is essentially needed. Miniaturized pumps have been demanded for cooling water circulation and a low power consumption. To obtain sufficient performance for practical applications, in this paper, a piezoelectric pump composed of hinge-lever using multilayer PZT actuator to generate large displacement and two sheet type check valves to control flow direction are designed. First, hinge-lever mechanism consists of a pin hinge-lever and two multilayer PZT actuators. The metal bellows is used as a flexible pump chamber. The hinge-lever mechanism produces a 560 mum displacement with free load. Second, a check valve with high response is applied and the basic characteristics are experimentally investigated with various shapes and thickness. As a result, the maximum flow rate of 1.85 l/min and maximum pumping pressure of 25 kPa are obtained with the driving frequency of 11 Hz at 100 Vp-p

Piezoelectrically Driven Dispensing Head for Encapsulation of Light Emitting Diode Chip

This study is about an amplified piezoelectric actuator driving a noncontact dispensing head. This dispensing head is mostly used for dispensing silicone encapsulants in a light emitting diode (LED) packaging process. The dispensing head using the piezoelectric actuator is capable of precisely dispensing high-viscosity silicone encapsulants at a high speed. However, the multilayer piezoelectric actuator has a very tiny displacement as small as the order of 10 µm. Accordingly, a device for amplifying the displacement of multilayer piezoelectric actuators is needed. To this end, the authors designed and manufactured a displacement amplification device using a metal frame. The amplification device consists of two multilayer piezoelectric actuators and a metal frame for amplifying displacement. The amplification device has a 209 µm displacement at an input DC voltage of 150 V. The extension displacement and contraction displacement generate 9 and 10 N forces, respectively.

Analysis and design of LVDT

In this paper, analysis for LVDT has been performed to design and evaluate the performance of the sensor. To do this, finite element method (FEM) is used and parametric analysis is conducted. From the analysis, performance of a LVDT sensor can be investigated precisely before actual manufacturing.

New approach to design control cone for electro-magnetic proportional solenoid actuator

In this paper, steady state characteristics of the electro-magnetic proportional solenoid actuator for pressure control valve determined by the shape of control cone are analyzed using finite element method and it is confirmed that the electro-magnetic proportional solenoid actuator has a constant attraction force in the control region independently on the stroke position. And the shape of control cone is optimized using (1+1) evolution strategy to get a constant force. In the optimization algorithm, control cone length, thickness and taper length are used as design parameters. In this paper, poppet and valve body which are assembled into the electro-magnetic solenoid actuator are designed and manufactured. Also, manufactured valve is tested using the experimental setup. Through the experimental procedure, characteristics of the manufactured valve are studied and compared to the results of theoretical analysis. Finally, the attraction force of proposed model was verified to have about ±2.5% error compared with simulation value.

Pressure Control Valve using Proportional Electro-magnetic Solenoid Actuator

This paper presents an experimental characteristics of electro-hydraulic proportional pressure control valve. In this study, poppet and valve body which are assembled into the proportional solenoid were designed and manufactured. The constant force characteristics of proportional solenoid actuator in the control region should be independent of the plunger position in order to be used to control the valve position in the fluid flow control system. The stroke-force characteristics of the proportional solenoid actuator is determined by the shape (or parameters) of the control cone. In this paper, steady state and transient characteristics of the solenoid actuator for electro-hydraulic proportional valve are analyzed using finite element method and it is confirmed that the proportional solenoid actuator has a constant attraction force in the control region independently on the stroke position. The effects of the parameters such as control cone length, thickness and taper length are also discussed.

Pressure Regulator for Pneumatic Valve with a PZT Actuator

The pressure regulator which is used for controlling the reducing pressure in the piezoelectrically driven pneumatic valve has been studied. The pneumatic valve of this study object is 2-stage type and consists of a piezoelectric actuator, a controller, a poppet valve and a pressure regulator. Nominal flow of 50 1 pm, maximum operating pressure of 0.9 MPa and frequency characteristic of 10 Hz and over are required in this pneumatic valve, but the pressure regulator is needed because piezoelectric actuator has no ability to control the pressure of 0.9 MPa directly. In this study, bimorph type PZT actuator of 25.2 mm (L)times7.2 mm (W)times0.5 mm (H) with constant of -220 times10 -12 CN-1 was proposed and investigated. Maximum operating force of 0.052 N and maximum displacement of 63 mum were gotten from the fabricated PZT actuator. From the analysis results, the orifice diameter of 0.6 mm for a piezoelectric actuator was derived and then the pressure regulator which can be operated under 0.15 MPa easily was designed and manufactured. Performance and effects of design parameters were simulated by the Simulink of Matlab software, and it was confirmed that the performance characteristics of manufactured pressure regulator are superior in the common use pressure range of 0.5 MPa to 0.7 MPa. The results show that the proposed pressure regulator is suitable for the pneumatic valve with a PZT actuator