Lead zirconate titanate (PZT) ceramics is usually used as a piezoelectric material. However it has characteristics of not only piezoelectricity but also flexoelectricity. Piezoelectricity is a phenomenon that electric polarization is induced by strain, and flexoelectricity is the one that the polarization is induced by strain gradient. In this study, flexoelectricity in poled soft PZT ceramics is measured. In order to eliminate influence of piezoelectricity, PZT ceramic thin plates are subjected pure bending using four-point bending experimental mechanism. Strain gradient along the direction of thickness in the plate is caused by the bending motion. Electric charge between two electrodes which is set on the center of the plate surface is measured under quasi-static sinusoidal load. Even though the polarization for piezoelectric effect is eliminated by the experimental setup, the influence of piezoelectric effect still remains since polarization by piezoelectricity is much larger than the one by flexoelectricity. So the influence of piezoelectricity is eliminated using qualitative difference between piezoelectricity and flexoelectricity for poling direction. Eventually, flexoelectric coefficient of the order of 10-5 C/m is measured.
There are many important applications in printed electronics and publishing industries that use the principle of roll-to-roll manufacturing to make printed electronic devices with lower cost. Web velocity and tension control algorithm plays an important role in improving the quality of product in mass processing of using roll-to-roll web technology. Most algorithms proposed in recent years use PI or PID controllers and disturbance compensation schemes to increase the precision and the stability. Due to the increasing demand of high accuracy in printed electronics industry at micrometer-level, it is necessary to have a precise control scheme of web velocity and tension in the presence of disturbances. In this paper, a precise control algorithm is proposed for non-linear single-span roll-to-roll web control system using the back-stepping controller with the design parameters chosen optimally by using the modified genetic algorithm. The outcome of this study proves the reliability throughout simulation results in Matlab/Simulink and in comparison to the experimental results
The problems of contact, joint and connection play important roles in every field of industry. Some micro-mechanical and electronic devices have elements that create friction against each other while in contact with one another all the time. Even though a small normal load is applied on the movement or behavior, the influence of the interaction between contact surfaces in all fields of industry cannot be ignored. In this study, how contact areas are varied in the slipping range between glass substrate and micro-glass spheres with varied diameters was investigated. In order to study the variations of contact areas, micro-glass spheres (dry borosilicate glass spheres) with different diameters (D=10µm, D=20µm) were glued to stainless steel-cantilevers (spring constant k=577N/m). The experiments were performed in various normal applied loads using AFM (Atomic force microscope) and variations between contact areas were simulated using the FEM (Finite Element Method). The variations on contact areas were compared using the results of the experiment using AFM and FE analyses in the contacted range for slipping of each micro-glass sphere. In addition to that, these were considered to be based on the wear volume and roughness as parameters due to their variations. From the results of the experiment, the contact area by the surface forces is dominated by increases and decreases of the wear volume due to the contact pressure force. Also, the influence of the deformation of the contact area due to contact pressure force cannot be ignored.
In expressive bodily movement created by one person and his or her partner, they feel as if their bodies are united. In such an inseparable relationship, a process to physically feel activeness and passiveness is important. The objective of this study is to capture activeness and passiveness in bodily interaction. We focused on myoelectric (ME) potential, by which the difference in time of generation and amplitude between voluntary and reactive movements can be estimated. A system for measuring ME potential in bodily interaction was developed. This system comprises a board that slides only in a front-back direction to simplify bodily interaction, an liner encoder, active electrodes for surface electromyography, and an amplifier. Experiments showed that for active movement, the increase in ME potential was earlier and the amplitudes of the ME potential were larger when compared with those for passive movement. We also attempted to distinguish between active and passive movements using the amplitude of the ME potential in embodied interaction, with fixing the relationship between active and passive roles. The concordance rate was more than 80%; thus, the validity of this method was confirmed. Moreover we examined the degree of correspondence between the estimated active or passive status by the proposed determining method and the subjective sensation by button-report in embodied interaction without fixing active-passive roles. The concordance rate was 68%. This result suggested there is discrepancy between the subjective sensation and physical state when the roles of the pair change dynamically in creating improvised bodily-expression.
A novel slider-based micro-actuator for magnetic disk drive was designed and fabricated to improve the magnetic head positioning accuracy. The micro-actuator consists of a head slider, an actuator base, flexible hinge elements, and a pair of unimorph actuators which has piezo-electric transducers and actuator arms as components. The slider body is able to rotate around the center of mass, and the movable end of the actuator arms are contacted but not fixed to the slider body, so the arms won't constrain the slider rotation and results to a large stroke. The actuator arms are actuated by piezo-electic transducers to apply a rotation torque to the slider. The stroke of 0.16µm peak-to-peak was obtained under a drive voltage of +/-20V and the frequency response of the slider tip excited by the piezo-electric actuators was fairly well, with slider sway mode frequency of 21.8kHz. The evaluation results showed the micro-actuator is able to improve the servo bandwidth, implemented in the disk drive in the future.
This paper investigates the workspace and the orientation capability of robotic fingers with a five-bar linkage and its variance defined by the parameter of a base link. Associating with the kinematics model and the link parameter analysis of a general structure in the form of coincidence of two ground pivots, the workspace and the orientation mapping of the robotic finger are presented and singularity conditions under different link parameters are discussed. This is then extended to variant mechanisms with separate ground pivots forming a structure of a parallel mechanism for robotic fingers, leading to further singularity analysis and workspace discussion. The orientation capability is then depicted in the workspace of this variance. A robotic finger is design to show the industrial application of the Analysis.
A unique driving method of piezoelectric actuator to reduce influences of hysteresis and creep is represented in the paper. It is for point-to-point (PTP) open-loop positioning. In the method, when an object is stepwise positioned using the piezoelectric actuator, the input voltage to the actuator is raised up to maximum value and pulled down to 0V sinusoidally in order to initialize the actuator condition, and then it is returned to a constant starting point at the beginning of every step. Finally it is raised up to appropriate step height with some overshoot. Both influences of hysteresis and creep characteristics are reduced drastically using the method. Stepwise positioning of 2µm step height with 0.2µm accuracy is realized using the basic method. For nano-meter order positioning accuracy, creep behavior of the actuator is serious problem. It is found that multi-cycle large sinusoidal drive which is called initializing drive can reduce creep motion significantly. Eventually, less than 5nm accuracy for 20nm stepwise PTP positioning is realized.