Morimasa Nakamura

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.

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.

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.

New Japanese Standard JIS B 1759 on load capacity of plastic gears

The present paper introduces Japanese Industrial Standard (JIS) B 1759 “Estimation of tooth bending strength of cylindrical plastic gears.” The new standard is based on ISO 6336–3. In calculation of load capacity of plastic gears, it is important that mechanical properties of plastic material are greatly affected by heat. Therefore, the standard includes consideration of the effects of frictional heat generation and ambient temperature on tooth bending strength of plastic gears. This paper also describes examples of calculating tooth bending strength from results of operating tests with POM gear pair according to the standard.

Fundamental study on detection of plastic-gear-failure signs (synchronization of a nonlinear oscillator to mesh frequency)

The present paper proposes a new method using neural oscillators to filter out the background noise of vibration in meshing plastic gear pairs for detection of failure signs of the gears. Generally, the vibration caused by the tooth-to-tooth meshing of a rotating gear pair contains various frequency components, which are due to amplitude and frequency modulation caused by eccentricity or torque variation. These modulated frequency components on the measured vibration make detection of gear failure difficult; e.g., gear tooth cracks. In this paper, these unnecessary frequency components are eliminated with a feed-forward control system in which neural oscillator’s synchronization property works. Each neural oscillator is designed to tune the natural frequency to a particular one of the components. The properly-designed neural oscillators can follow the change in the driving torque variation autonomously, because of their synchronization property. Moreover, the output phase of the oscillators is set a difference of 180 degrees from the input one, and is included in the original measured response to eliminate the amplitude of the unnecessary components. For this purpose, a simulated acceleration response of meshing gears was firstly constructed in the manner of adding shaft frequency, secondary meshing frequency and their first order sidebands to the regular meshing components (primary meshing frequency). Furthermore, the proposed noise cancellation method was applied to the simulated response, and it is concluded that the effect of gear tooth crack on a change in the tooth stiffness appears conspicuously on the filtered vibration response.

Semi-Active Vibration Control with Harmonically Varying Damping (Performance Improvement of Base Isolation for SDOF System and Vibration Control of Coupled SDOF Systems)

This study demonstrates two types of semi-active vibration control with harmonically varying damping. The first one is performance upgrade of semi-active base isolation method for single-degree-of-freedom system and the other one is a semi-active vibration control method for parallel coupled single-degree-of-freedom system. Recent researches have demonstrated a new method for the utilization of variable damping. In those studies, the damping coefficient was harmonically controlled. Previous studies have confirmed vibration mitigation of a base-isolated structure by interference cancellation with the harmonically varying damping. However the results of previous studies had still room for improvement. Consequently, this study suggests a method for the performance augmentation. However, no such study considering the multi-degree-of-freedom system has been conducted. This paper presents the effect of the harmonically varying damping on the multi-degree-of-freedom system, especially; the influence on two structures in parallel with a variable damper between the structures is discussed.

Evaluation System of Tooth Contact Patterns of Hypoid Gears Using Artificial Intelligence

Tooth contact inspection is one of the most common methods for checking qualities of hypoid gear pairs. A change in machine setting parameters for cutting and lapping processes of a hypoid gear pair enables a tooth contact pattern of a hypoid gear pair to be varied. The deviation of the pattern from the target one is represented by a grade point. In the inspection, the qualities of hypoid gear pairs are usually classified into only two grades; OK or NG. However, in order to conduct a follow-up survey on problems of the products and to be useful to be trouble shooting tasks of the end products, finer classifications and more quantitative evaluations of tooth contact patterns could be effective. Such approaches have been tried, however, only experienced and well-trained technicians for the inspection of hypoid gear pairs can determine the point of each tooth contact pattern. And it is difficult to make this evaluation method automatic. To overcome this problem, an application of artificial intelligence system must be useful. The present paper describes a computer evaluation system using the neural network, which is a kind of the artificial intelligence systems, for tooth contact patterns of hypoid gear pairs which can evaluate the results of the inspections instead of experienced hypoid gear technicians. This system with the neural network has a capability to learn relationships between evaluation grade points of tooth contact patterns given by the hypoid gear technicians and graphics of tooth contact patterns of hypoid gear pairs. Moreover, it can return the evaluation grade points when a tooth contact pattern is input into the system. The evaluation performance of the developed system was discussed. And a quality of normative tooth contact patterns, which were used as the teacher signals for training the neural network system, greatly affected its performance. The comparison of evaluated grade points obtained from developed system with the technician’s ones showed that the correct answer ratio obtained from the developed system was about 90% in the best case.Copyright