Ichiro Moriwaki

Evaluation method for a controller of active mass damper using central pattern generator

This paper proposes an evaluation method for a CPG controller designed for active mass dampers. Neural oscillators composing the CPG have nonlinear and entrainment properties. Therefore, the proposed controller has possibility to have flexibility, when the structural parameters, i.e. stiffness or damping, are changed by the effect of earthquakes and the like. However, there has been no study to evaluate the controller’s above-mentioned properties. For tuning into practical application, the reliability and flexibility along with the controller’s performance must be analyzed. In our previous study, the phase reduction theory was tried to appraise the synchronization between a structure and a single neural oscillator and the synchronization region of the neural oscillator was obtained as basic research. However, the information from the synchronization region was insufficient to evaluate the system, because the neural oscillator has a phase difference called a phase locking point between the structure and the neural oscillator during the synchronization. Then, in this paper, the phase locking point within the synchronization region between a structure and a single neural oscillator is focused on, and the phase locking point and the vibration mitigation effect are considered with the simple object model.

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.

Output analysis of swarm of neural oscillators stimulated by earthquake-induced acceleration responses of a structure

This paper shows input-output analysis of a neural oscillator swarm stimulated by earthquake-induced acceleration responses of a structure. We have proposed a new active mass damper system consisting of a neural oscillator and a position controller. However, the proposed system has not adapted successfully to parameter changes of the structure. Recent studies in biology have demonstrated that multiple oscillators have hierarchical network structures to ensure adaptation to environmental changes. To improve the robust performance of the proposed system by constructing of hierarchical network of neural oscillators, there is a need for a better understanding of nature of different neural oscillators. This research addressed this need by visualizing output of swarm of neural oscillators, whose natural frequencies and input gains are different. The numerical information of output is visualized by grayscale, and the relation of output of different neural oscillators is considered when input is the same. As a result, the research provides new information that predicts the instant center frequency of a structure excited by earthquakes.

Active mass damper system for high-rise buildings using neural oscillator and position controller: sinusoidally varying desired displacement of auxiliary mass intended for reduction of maximum control force

Reducing vibration of high-rise structures under earthquake load has been the subject of considerable efforts in Japan. Relevant researches about vibration energy dissipation devices for buildings have been undertaken. An active mass damper is one of the well-known vibration control devices. Despite the accumulation of much knowledge of control design methods for the system, application of the devices to high-rise structures under earthquake load is challenging, because the active mass dampers have one serious disadvantage about stroke limitation of the auxiliary mass. In this study, we have proposed a new control system, which had a neural oscillator and position controller, to solve this problem. The objective of this paper is to improve the vibration control performance of the proposed active mass damper system. The previous method generated rectangular waves as the desired displacement, whose amplitude is varied in accordance with the vibration responses of a structure excited by earthquakes. Furthermore, the gains of the position controller, which derives the auxiliary mass to the desired displacement, have been designed in consideration of response reduction of the structure. However, the generated rectangular desired displacement was not adequate to reduce the maximum acceleration responses of the structure, because the driving force for the auxiliary mass generates excessive amounts of acceleration as the direction of the desired displacement is switched. Thus, this paper proposes a new method, which generates sinusoidal varying desired displacement for the auxiliary mass of the active mass damper system to reduce the acceleration response of structures. The results of numerical simulation showed that the proposed method in this work was effective for improving the control performance.

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.

Active mass damper system for high-rise buildings using neural oscillator and position controller considering stroke limitation of the auxiliary mass

This paper proposes a problem-solving method for the stroke limitation problem, which is related to auxiliary masses of active mass damper systems for high-rise buildings. The proposed method is used in a new simple control system for the active mass dampers mimicking the motion of bipedal mammals, which has a neural oscillator synchronizing with the acceleration response of structures and a position controller. In the system, the travel distance and direction of the auxiliary mass of the active mass damper is determined by reference to the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using a PID controller. The one of the purpose of the previouslyproposed system is stroke restriction problem avoidance of the auxiliary mass during large earthquakes by the determination of the desired value within the stroke limitation of the auxiliary mass. However, only applying the limited desired value could not rigorously restrict the auxiliary mass within the limitation, because the excessive inertia force except for the control force produced by the position controller affected on the motion of the auxiliary mass. In order to eliminate the effect on the auxiliary mass by the structural absolute acceleration, a cancellation method is introduced by adding a term to the control force of the position controller. We first develop the previously-proposed system for the active mass damper and the additional term for cancellation, and verity through numerical experiments that the new system is able to operate the auxiliary mass within the restriction during large earthquakes. Based on the comparison of the proposed system with the LQ system, a conclusion was drawn regarding which the proposed neuronal system with the additional term appears to be able to limit the stroke of the auxiliary mass of the AMD.

Experimental evaluation of a control system for active mass dampers consisting of a position controller and neural oscillator

This paper shows experimental performance evaluation of a new control system for active mass dampers (AMDs). The proposed control system consists of a position controller and neural oscillator, and is designed for the solution of a stroke limitation problem of an auxiliary mass of the AMDs. The neural oscillator synchronizing with the response of a structure generates a signal, which is utilized for switching of motion direction of the auxiliary mass and for travel distances of the auxiliary mass. According to the generated signal, the position controller drives the auxiliary mass to the target values, and the reaction force resulting from the movement of the auxiliary mass is transmitted to the structure, and reduces the vibration amplitude of the structure. Our previous research results showed that the proposed system could reduce the vibration of the structure while the motion of auxiliary mass was suppressed within the restriction; however the control performance was evaluated numerically. In order to put the proposed system to practical use, the system should be evaluated experimentally. This paper starts by illustrating the relation among subsystems of the proposed system, and then, shows experimental responses of a structure model with the AMD excited by earthquakes on a shaker to confirm the validity of the system.

Calculation Model for Internal Gear Skiving With a Pinion-Type Cutter Having Pitch Deviation and a Run-Out

As the emerging economies expand, demand for low cost production of internal gears has been increasing. And skiving is in focus as a potential method than can meet this demand.Skiving was invented in 1910, since then, mechanical machine has been developed to NC machine and cutter design technologies have developed dramatically. As a result, several machine and tool manufacturer started to release their skiving machine and skiving cutter as well.Furthermore, many studies on the kinematics have been conducted both in research institutions and private companies. However, most of these studies are subject to understanding the cutting mechanisms as a basic research and establishing cutter design methods.For further improvement and boost widespread application of the process, optimization of the manufacturing process is an issue. Particularly, the effects of cutter accuracy and cutter set up deviations on the skived gear are important to ensure reliability of the process. Unfortunately, few studies on those effects can be found.In this paper, geometrical model that can predict the effect of pitch deviation and of run out of a cutter on a skived gear is proposed. Experiments were also carried out to verify the validity of the model, and the results were in good agreement with the simulated ones.Copyright

A driven active mass damper by using output of a neural oscillator (effects of position control system changes on vibration mitigation performance)

In this paper, a design method for a PD controller, which is a part of a new active mass damper system using a neural oscillator for high-rise buildings, is proposed. The new system mimicking the motion of bipedal mammals is a quite simple system, which has the neural oscillator synchronizing with the acceleration response of the structure. The travel distance and direction of the auxiliary mass of the active mass damper is decided by the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using the PD controller. Therefore, the performance of the PD controller must be evaluated by the vibration energy absorbing efficiency by the system. In order to bring the actual path driven by the PD controller in closer alignment with the ideal path, which is assumed to be a sinusoidal wave under resonance, firstly, the path of the auxiliary mass driven by the PD controller is analytically derived, and the inner product between the vector of ideal and analytical path is evaluated. And then, the PD gain is decided by the maximum value of the inner product. Finally, numerical simulations confirm the validity of the proposed design method of the PD controller.