Key Engineering Materials Vols. 326-328

Abstract: This paper presents the design, fabrication, and performance test of a gap adjustable piezoelectrically-actuated DoD(drop-on-demand) molten metal injector for application to the 3D microstructure manufacturing or printed electronics. In the design process, we propose the gap adjustable mechanism of the piezoelectrically-actuated inkjet system to control the volume and velocity of the ejected molten metal droplets. In the experimental process, we fabricate the DoD metal injector and measure the volumes and velocities of the ejected droplets for molten metal as well as pure water to compare the ejecting performance for the different viscosity of ink and the operating temperature of the system.

Abstract: A smart material actuator is required for a smart structure having multifunctional performance. Among the smart material actuators, piezoelectric actuator is known for its excellent large force generation in broad bandwidth in a compact size. However it needs relatively large actuation voltage requiring a bulky hardware system. This study is mainly concerned to develop a self-powered miniaturized piezoelectric actuator driver (MIPAD) controlled by a radio controller for small sized piezoelectric smart structures. It can receive command from other microprocessors or a remote radio controller. We designed a real hardware and it demonstrated good performances even though the driving system was very small. The MIPAD is expected to minimize the weight and size of the piezoelectric actuator system and it can be easily embedded into mobile smart structures.

Abstract: This paper presents a computer-based tracking control approach for a piezoelectric actuator based on incorporating a feedforward loop with a PID feedback controller. The purpose of this paper is to improve the hysteresis characteristics of a stack type piezoelectric actuator using the hysteresis nonlinearity compensator. The system proposed in this study prints by spraying the molten metal, and consists of a nozzle, heating furnace, operating actuator, and an XYZ 3-axis stage. As an operating system, the piezoelectric(PZT) method has very valuable uses. The PZT actuator, however, has a hysteresis nonlinearity due to the ferroelectric characteristics of the PZT element. This causes problems in the system position control characteristics and deteriorates the performance of the system. This study proposed a inverse hysteresis model, a mathematic modeling method that can express the geometric relationship between voltage and displacement, in order to reduce the hysteresis of the PZT actuator. In addition, system identification and PID control methods were examined. Also, it was confirmed that the proposed control strategy gives good tracking performance.

Abstract: In this work, behavior of a unimorph piezoceramic actuator, LIPCA (Lightweight Piezo- Composite Actuator) has been numerically and experimentally investigated. By measuring the lateral displacement created by the compressive load, the buckling load of the LIPCA was determined. Under simply supported configuration, the measured buckling load agreed well with the geometrically nonlinear buckling load from the finite element analysis. The measured data shows that the lateral displacement of the LIPCA is significantly increased when the electric field is prescribed to the LIPCA in addition to the compressive load. The measured data was compared with the computed results from the geometrically nonlinear finite element analysis. The numerical simulation agreed well with the measurement for low compressive load and low electric field.

Abstract: In the design of piezoelectric actuator the concept of compliant mechanism combined with piezoelectric materials has been used to magnify either geometric or mechanical advantage. The polarization of piezoelectric materials is considered to improve actuation since the piezoelectric polarization has influences on the performance of the actuator. The topology design of compliant mechanism can be formulated as an optimization problem of material distribution in a fixed design domain and continuous approximation of material distribution(CAMD) method has demonstrated its effectiveness to prevent the numerical instabilities in topology optimization. The optimization problem is formulated to maximize the mean transduction ratio subject to the total volume constraints and solved using a sequential linear programming algorithm. The performance improvement of Moonie actuator design confirms an effect of polarization direction and CAMD.

Abstract: Research on piezoelectric unimorph actuators has been intensively increased during the past decade due to the wide applications of this actuator type in aerospace, vibration control, biomimetic robots, artificial muscles… Most analyses focused on the design performance with load-free actuating condition. Loading performance has not been considered adequately yet though in real application the actuators always work under certain carrying load. This paper introduces the measuring system, the experimental setup and presents the observed loading performance of the actuators with center load. Two typical kinds of piezoelectric unimorph actuator, LIPCA-C3 and THUNDER, are investigated. The numerical analyses are also conducted to illustrate the loading behavior of these devices. Some remarks and suggestions for future research activities are drawn.

Abstract: To identify a delamination crack in a CFRP laminate wirelessly, we proposed an electric resistance change method with oscillating circuit in the previous study. Although the method detects the delamination creation, it cannot monitor condition of applied strain before delamination creation because the electric resistance change due to strain changing is quite small. In the present study, a bridge circuit, two amplifiers and voltage-controlled oscillator are added to sensing circuit so that it can monitor very little change of the electric resistance change. Using proposed strain sensing system, the electric resistance change and oscillating frequency change due to strain changing are experimentally measured. As a result, the method is found to successfully monitor the applied strain.

Abstract: In the present paper, the dynamic characteristics of smart hull structure are investigated for the feasibility of Macro Fiber Composite (MFC) actuator in active vibration control of smart hull structure. MFC is an advanced anisotropic piezoceramic actuator. Finite element technique was used to ensure application to practical geometry and boundary conditions of smart hull structure. Using finite element method, modal analysis and strain distribution were first conducted to investigate dynamic characteristics of smart hull structure. Based on numerical modal analysis, the locations of MFC actuators are determined to achieve maximum control authority. Then, the MFC actuators are attached to the hull structure and natural frequencies and damping coefficients are identified through experimental modal test.

Abstract: CFRP laminate can be used itself as a sensor for detecting own damage. The authors have introduced electric resistance change method and asymmetrical dual charge electric potential change method to detect a delamination in the CFRP laminate. Although the methods showed good performance of estimation analytically and experimentally, those are sensitive to electromagnetic noise. Experimental error caused by such noise in the actual use may affect the accuracy of estimation. In this paper, influence of the noise on accuracy of estimation was investigated quantitatively using finite element analysis. It was clarified that the methods have different characteristics for experimental noise.

Abstract: Drivers are becoming more fatigued and uncomfortable as traffic densities increase, and so, can show slower reaction time. They then face the danger of traffic accidents due to their inability to cope with frequent shifting. To reduce this risk, some drivers prefer automatic transmissions to manual transmissions. However, automatic transmission requires both higher fuel consumptions and costs. For this reason, attention to automated manual transmission that can provide high efficiency, low cost and easy manufacturability has been increasing. In addition, the function and performance of the electronic control unit of automobiles has improved continually and rapidly with the growing electronics technology. The ECU is a representative embedded system in automobiles, which has to satisfy high performance and reliability under the constraints of size and cost. In this paper, the embedded system platform for automobiles is developed on the basis of MPC565, and a test rig is developed to perform the basic function test for automatic clutch actuation. The developed embedded system and clutch control algorithm are validated by the experimental results performed on the test rig.