Nanako Miura

Structural design of active seismic isolation floor with a charging function

This study shows an optimum structure of a seismic isolation floor against horizontal ground motions. Although a seismic isolation floor is effective with vibration reduction, the response of the floor becomes larger when excited by long-period ground motions. It is shown that caster equipment move and suffer damage in a seismic isolation structure by an experiment. Moreover, the permissible displacement of the floor is limited. Therefore, the focus is on an active seismic isolation. About active control, the system cannot operate without power supply. To solve these problems an energy regeneration is considered in our previous study. These studies only analyze simple model and did not choose the suitable structure for active control and energy regeneration. This research propose a new structure which has regenerated energy exceeds the energy required for the active control by numerical simulation.

Development of three-axis inkjet printer for gear sensors

The long-term objective of our research is to develop sensor systems for detection of gear failure signs. As a very first step, this paper proposes a new method to create sensors directly printed on gears by a printer and conductive ink, and shows the printing system configuration and the procedure of sensor development. The developing printer system is a laser sintering system consisting of a laser and CNC machinery. The laser is able to synthesize micro conductive patterns, and introduced to the CNC machinery as a tool. In order to synthesize sensors on gears, we first design the micro-circuit pattern on a gear through the use of 3D-CAD, and create a program (G-code) for the CNC machinery by CAM. This paper shows initial experiments with the laser sintering process in order to obtain the optimal parameters for the laser setting. This new method proposed here may provide a new manufacturing process for mechanical parts, which have an additional functionality to detect failure, and possible improvements include creating more economical and sustainable systems.

Conductive ink print on PA66 gear for manufacturing condition monitoring sensors

Failures detection of rotating machine elements, such as gears, is an important issue. The purpose of this study was to try to solve this issue by printing conductive ink on gears to manufacture condition-monitoring sensors. In this work, three types of crack detection sensor were designed and the sprayed conductive ink was directly sintered on polyimide (PI) - coated polyamide (PA) 66 gears by laser. The result showed that it was possible to produce narrow circuit lines of the conductive ink including Ag by laser sintering technique and the complex shape sensors on the lateral side of the PA66 gears, module 1.0 mm and tooth number 48. A preliminary operation test was carried out for investigation of the function of the sensors. As a result of the test, the sensors printed in this work should be effective for detecting cracks at tooth root of the gears and will allow for the development of better equipment and detection techniques for health monitoring of gears.

A close inspection and vibration sensing aerial robot for steel structures with an EPM-based landing device

This paper proposes an aerial robot that can land on and cling to a steel structure using electric permanent magnets to be- have as a vibration sensor probe for use in vibration-based structural health monitoring. In the last decade, structural health monitoring techniques have been studied intensively to tackle with serious social issues that most of the infrastructures in advanced countries are being deteriorated. In the typical concept of the structural health monitoring, vibration sensors like accelerometers are installed in the structure to continuously collect the dynamical response of the operating structure to find a symptom of the structural damage. It is unreasonable, however, to permanently deploy the sensors to numerous infrastructures because most of the infrastructures except for those of primary importance do not need continuous measurement and evaluation. In this study, the aerial robot plays a role of a mobile detachable sensor unit. The design guidelines of the aerial robot that performs the vibration measurement from the analysis model of the robot is shown. Experiments to evaluate the frequency response function of the acceleration measured by the robot with respect to the acceleration at the point where the robot adheres are carried out. And the experimental results show that the prototype robot can measure the acceleration of the host structure accurately up to 150 Hz.

Development of sensing systems printed with conductive ink on gear surfaces: manufacturing of meander line antenna by laser-sintered silver nano-particles

Health monitoring methods for machines have been the subject of considerable efforts to maintain it at an appropriate timing. Failures of rotating machine elements can cause severe accidents, thus, to detect such failures is an important issue. However, health monitoring of rotating machine elements, such as gears, is challenging because of rotation at high speed in gearboxes, geometric complexity, space limitation for measurements, or another operation conditions. The long-term objective of the present research is to develop smart sensor systems for detecting gear failure signs. As the very first step, this paper proposes a new method to manufacture electrical circuits, such as sensors or antennas, on gears. We print these circuits directly on the gear surface using a laser sintering technique of conductive ink. For this purpose, we have begun to develop a 4-axis laser printing system. This paper shows the laser sintering conditions of the conductive ink splayed on steel plates insulated by polyimide layers. The conductivity of the printed lines was evaluated through observation with a miniature scanning electron microscope. Finally, according to the obtained laser sintering conditions, a meander line antenna was printed as a part of smart sensor systems.

GA-Optimized Fuzzy State Space Model of Multi Degree Freedom Structure Under Seismic Excitation

Active structural control has drawn significant attention in recent decades. In this paper, the problem of active vibration control of multi-degree-freedom structures is considered. Fuzzy logic controller combined with the genetic algorithm (GA) is designed to optimize the parameters of active tuned mass damper (ATMD) for the best results in reduction of the building response under earthquake excitation. The advantage of the fuzzy logic approach is the ability to handle the non-linear behavior of the system. Non-linear behavior of the soil is modeled in the dynamics of the structural system with nonlinear hysteric restoring forces. The building structure with eleven stories is modeled as a 2D frame, which uses tuned mass damper subsystems mounted on the top of the building. A structural system was simulated against the ground motion of the destructive earthquakes. The time history of the story displacements and accelerations, the control voltages and forces, and the frequency responses of both the uncontrolled and the controlled structures are shown in the end of this study. The performance of designed fuzzy logic control is checked using the changing mass parameters of each story and the results are discussed. The comparison between the proposed control and TMD passive control shows that the proposed fuzzy logic controller has great potential in active structural control.Copyright

Seismic isolation device having charging function by a transducer

In late years, many base isolated structures are planned as the seismic design, because they suppress vibration response significantly against large earthquake. To achieve greater safety, semi-active or active vibration control system is installed in the structures as earthquake countermeasures. Semi-active and active vibration control systems are more effective than passive vibration control system to large earthquake in terms of vibration reduction. However semi-active and active vibration control system cannot operate as required when external power supply is cut off. To solve the problem of energy consumption, we propose a self-powered active seismic isolation floor which achieve active control system using regenerated vibration energy. This device doesn’t require external energy to produce control force. The purpose of this study is to propose the seismic isolation device having charging function and to optimize the control system and passive elements such as spring coefficients and damping coefficients using genetic algorithm. As a result, optimized model shows better performance in terms of vibration reduction and electric power regeneration than the previous model. At the end of this paper, the experimental specimen of the proposed isolation device is shown.

Variable gain feedback control of a high-rise building-elevator system adjusted to ground motion intensity and response level

A control method is proposed based on frequency shaped LQG and variable gain feedback in order to choose proper control objective and prevent saturation of control force considering intensity of ground motion and level of building response. The controller examines exceedance rate of building response over a threshold and the maximum required control force estimated from ground acceleration in order to reduce response of both a building and elevator rope efficiently preventing saturation. It is demonstrated that the proposed method can suppress unpreferable response of building layers near the top induced by control force.