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Regenerative chatter vibration is a typical machining problem during cutting. The frequency and phase shift of regenerative chatter can be used as indicators to suppress regenerative chatter. However, direct measurement of chatter vibration during cutting is difficult for end milling because the tool blade rotates. Therefore, chatter vibration is generally measured indirectly, for example, from cutting noise or vibration transmitted to the spindle. The type and position of the installed sensors must be appropriately selected to accurately measure chatter vibration with these methods. This selection must account for the machine tool structure, cutting conditions, and the position where the chatter vibration occurs, making the measurement methods not universally applicable. When chatter vibration occurs during cutting, a periodic pattern called a chatter mark is formed on the machined surface. The chatter mark is formed by vibration during cutting, i.e., vibration information during cutting is directly recorded. Therefore, this paper proposes a method to analyze the frequency and phase shift of chatter vibration using a two-dimensional discrete Fourier analysis of the chatter mark based on the modeled formation mechanism of chatter marks, and further validates the proposed method by elucidating the mechanism of chatter mark formed by chatter vibration. First, a cutting simulation was performed based on the vibration displacement of the tool during chatter cutting obtained experimentally. This simulation elucidates the mechanism by which the vibration information of chatter vibration can be analyzed from the chatter mark. Subsequently, the chatter vibration parameters were analyzed from the chatter mark using the proposed method. The parameters were consistent with those analyzed from the vibration displacement of the tool, confirming the effectiveness of the proposed method. • The formation mechanism of chatter marks was elucidated by simulation. • The waveform of chatter vibration during cutting cannot be analyzed from chatter mark. • A method was proposed to analyze the regenerative chatter vibration during cutting. • The proposed method enables direct analysis of regenerated chatter vibration. • The results of the proposed method and the conventional method are in good agreement. [ABSTRACT FROM AUTHOR]

In recent years, collaborative robots able to work together with humans have become widespread in production sites and factory automation fields. In this context, the goal is to provide a production site where cooperative robots can share various types of tools with humans. However, we have not yet reached the point where collaborative robots and humans can share tools for advanced skills. Therefore, it is very important to investigate how a collaborative robot can control advanced tools requiring human skills and the processes for realizing such control. Musical instruments are some of the most difficult tools to handle. It is important to focus on musical instruments because they allow us to evaluate the robot's manipulation not only by evaluating its movements, but also by evaluating the resultant sound. In this study, we consider a flexible and large deformable musical saw as an unknown and advanced tool difficult for humans to manipulate. In a previous report, a support method for imitating a human was adopted and provided manipulation control based on striking sound feedback using a cooperative humanoid robot. In the present paper, the support method is improved at the tip of the musical saw to realize an advanced wrist motion. In addition, we discuss skillful manipulations based on striking sound feedback control while considering the positions and postures between the collaborative humanoid robot and musical saw. [ABSTRACT FROM AUTHOR]

Nanofibers are used in various fields and applications, such as medical care, environment protection, apparel, and agriculture; it is believed that they will continue to show substantial growth in the future. In this study, we focused on the filtration application of nanofibers. The filtration performances achieved polymeric nanofiber mass production by a melt-blowing method. First, the filtration performances of the fiber were experimentally tested with different thicknesses. Then, the computational fluid dynamics flow-analyzing software was used to simulate the pressure loss and flow resistivity of the trial-produced filter under the same conditions as those used in the experiment. Then, a three-directional physical model was proposed and used to calculate the fiber's gap size with different diameters under the same filling rate and the assumption that the fibers always exhibit uniform distribution. Consequently, it was confirmed that the trial-produced non-woven filter possessed excellent filtration abilities and that the investigated data can be used as a standard to manufacture non-woven fabric for producing high-performance filters and face masks. However, the manufacturing method of non-woven fabric filters must be investigated to satisfy both high particle filtration efficiency and low pressure loss in order to develop a high-performance filter. • The paper presents the relations among filling rate, fiber diameter, filtration efficiency and flow resistivity for high-performance filters and face masks. • Our experimental results show the relations between filter thickness and filtration efficiency. • Our proposed three-directional physical model for fiber aggregate can effectively estimate the fiber's gap size under the same filling rate and fiber diameter. • The CFD analysis and proposed flow resistivity theories are useful for accurately estimating the flow resistivity. • This paper shows a standard parameters for manufacturing high-performance filters and face masks in the future. [ABSTRACT FROM AUTHOR]