Shiro Arii

Active inherent restrictor for air-bearing spindles

Abstract An active control method for aerostatic bearings is proposed in this paper. The proposed method employs an active inherent restrictor AIR, (which was invented by the authors) to control pneumatic pressure on the bearing surface. The AIR consists of a piezoelectric actuator with a through hole, one end of which is small enough to function as an orifice when the actuator is embedded in the bearing to be controlled. Nine AIRS are incorporated into the aerostatic radial and thrust bearings of an air bearing spindle. According to the radial and/or thrust displacements of the spindle detected by sensors, a microcomputer changes the length of the piezoelectric actuators for controlling the orifice area of the AIRs and for compensating the displacements. Thus, the stiffness and the rotational accuracy in both radial and thrust directions can be improved without the occurrence of pneumatic hammer. Instead of ordinary passive inherent restrictors, the AIR can be incorporated into most conventional aerostatic bearings. An example of retrofit of the AIR to a commercially available air bearing spindle is also shown.

Binocular robot vision system with shape recognition

A binocular robot vision system having an autonomously moving active viewpoint is proposed. By using this active viewpoint, the system constructs a correspondence between the images of a feature points on the right and left retinas easily and calculates the spatial coordinates of the feature points. The system incorporates a function that detects straight lines in an image. To detect lines the system uses Hough transform. The system searches a region surrounded by 4 straight lines. Then the system recognizes the region as a quadrangle. The system constructs a correspondence between the quadrangles in the right and left images. By the use of the result of the constructed correspondence, the system calculates the spatial coordinates of an object. An experimental result shows the effect of the recognition of the surface of the object and the calculation of the spatial coordinates of the object.

Vibration control of a high-speed air-bearing spindle using an active aerodynamic bearing

A novel high speed air-bearing spindle is proposed as a tool spindle for small diameter of cutting and grinding tools. The spindle vibration at high rotational speed is suppressed by an active aerodynamic bearing incorporated into the spindle. For generating aerodynamic damping force, the wedge angle on the aerodynamic bearing surface is controlled by piezoelectric actuators. By using several control tactics, the effect of the active control of the aerodynamic bearing on the spindle vibration is analyzed. Experimental result shows that the amplitude of the spindle vibration can be suppressed to be 0.1μm at the rotational speed of 50,000 min-1 (833 Hz). Final goal of the study is to suppress the amplitude of spindle vibration less than 0.1 μm at the rotational speed of 120,000 min-1 (2 kHz).

Analysis of human glottal velocity using hot-wire anemometry and high-speed imaging.

Objectives: The aim of this study was to analyze glottal velocity and glottal opening and closure. For this purpose, we developed a miniature, flexible, hot-wire probe that can make truly instantaneous measurements of the human larynx in vivo. Methods: A miniature hot-wire tip was inserted into a flexible transnasal endoscope. Fiberscopic examination was performed transnasally so that we could observe glottal vibration using high-speed imaging. The tip of the hot-wire probe was placed just above the glottis. The position of the probe was carefully monitored and checked with another flexible endoscope. Results: Changes in velocity were recorded periodically. The velocity was higher in close proximity to the vocal folds. High-speed motion pictures were taken at a rate of 2,000 frames per second with an auxiliary light source. Conclusions: Quantitative analysis of glottal velocity is required to improve our understanding of the relationship between laryngeal physiology and acoustics in humans. To solve the problem of synchronization inaccuracy, glottal velocity was captured instantaneously in the high-speed imaging systems processor memory.

Binocular Robot Vision System with Shape Recognition

A binocular robot vision system having an autonomously moving active viewpoint is proposed. By using this active viewpoint, the system constructs a correspondence between the images of a feature points on the right and left retinas easily and calculates the spatial coordinates of the feature points. The system incorporates a function that detects straight lines in an image. To detect lines the system uses Hough transform. The system searches a region surrounded by 4 straight lines. Then the system recognizes the region as a quadrangle. The system constructs a correspondence between the quadrangles in the right and left images. By the use of the result of the constructed correspondence, the system calculates the spatial coordinates of an object. An experiment shows the effect of the line detection using Hough transform, the recognition of the surface of the object and the calculation of the spatial coordinates of the object

Sequential multipoint motion of the tympanic membrane measured by laser Doppler vibrometry: preliminary results for normal tympanic membrane.

Background Numerous studies have reported sound-induced motion of the tympanic membrane (TM). To demonstrate sequential motion characteristics of the entire TM by noncontact laser Doppler vibrometry (LDV), we have investigated multipoint TM measurement. Materials and Methods A laser Doppler vibrometer was mounted on a surgical microscope. The velocity was measured at 33 points on the TM using noncontact LDV without any reflectors. Measurements were performed with tonal stimuli of 1, 3, and 6 kHz. Amplitudes were calculated from these measurements, and time-dependent changes in TM motion were described using a graphics application. Results TM motions were detected more clearly and stably at 1 and 3 kHz than at other frequencies. This is because the external auditory canal acted as a resonant tube near 3 kHz. TM motion displayed 1 peak at 1 kHz and 2 peaks at 3 kHz. Large amplitudes were detected in the posterosuperior quadrant (PSQ) at 1 kHz and in the PSQ and anteroinferior quadrant (AIQ) at 3 kHz. The entire TM showed synchronized movement centered on the PSQ at 1 kHz, with phase-shifting between PSQ and AIQ movement at 3 kHz. Amplitude was smaller at the umbo than at other parts. In contrast, amplitudes at high frequencies were too small and complicated to detect any obvious peaks. Conclusion Sequential multipoint motion of the tympanic membrane showed that vibration characteristics of the TM differ according to the part and frequency.

Rotational Accuracy and Positioning Resolution of an Air-bearing Spindle with Active Inherent Restrictors

An active control system is incorporated into an air-bearing spindle designed for ultraprecision applications. The system uses the Active Inherent Restrictor (abbreviated AIR) for improving the rotational accuracy of the spindle. The AIR consists of a piezoelectric actuator having a hole, one end of which on the bearing surface acts as an inherent restrictor. According to the spindle vibration detected, the AIR controls the airflow rate, and reduces the amplitude of the vibration to less than 10nm. The control system also has the ability of positioning the spindle; one nanometer of step is clearly resolved. Therefore, this air-bearing spindle with the AIR can be used as an ultraprecision positioning device.

Novel Diaphragm-Control Restrictor for Precision Hydrostatic-Bearing Spindle

A novel diaphragm-control restrictor (DCR) is proposed for improving the performance of the hydrostatic-bearing spindle used in machine tools. The unique function of the proposed DCR is the wide adjustability of its restrictor characteristic. A two-step restriction system is adopted for the DCR; a spool restrictor is used as the first step restrictor. By changing the restrictor resistance of the spool restrictor, the effect of the active control in the DCR, the second step restrictor, can be altered. The proposed DCR is incorporated into a hydrostatic bearing supporting a precision spindle, and the performance of the bearing is analyzed. Numerical and experimental analyses show that the stiffness of the hydrostatic bearing with the proposed DCR can be five times as large as a conventional hydrostatic bearing of the same dimensions. Analysis of the dynamic compliance shows that the effect of the active control can be observed up to 20Hz. These results show that the proposed DCR is useful for improving the performance of the hydrostatic-bearing spindle in precision applications.

Binocular robot vision system with autonomous movement of viewpoint

A binocular robot vision system having an autonomously moving active viewpoint is proposed. By using this active viewpoint, the system constructs a correspondence between the images of a feature points on the right and left retinas easily and calculates the spatial coordinates of the feature points. The system incorporates two intelligent functions for enlarging the measuring region and increasing the accuracy of measurement. The first intelligent function is an autonomous movement of the viewpoint and the second is weighting process for measured points. These functions work when the system can recognize the solid body. As the first steps of the development of the recognition of a solid body, we incorporate these functions into the system to detect straight lines in an image. To detect lines we use Hough transform. The system searches a region surrounded by 4 straight lines. Then the system recognizes the region as a quadrangle. The system constructs a correspondence between the quadrangles in the right and left images. By the use of the result of the constructed correspondence, the system calculates the spatial coordinates of an object. An experiment shows the effect of the line detection using Hough transform, the recognition of the surface of the object and the calculation of the spatial coordinates of the object.

Sequential motion of the ossicular chain measured by laser Doppler vibrometry

Abstract Objective: In order to help a surgeon make the best decision, a more objective method of measuring ossicular motion is required. Methods: A laser Doppler vibrometer was mounted on a surgical microscope. To measure ossicular chain vibrations, eight patients with cochlear implants were investigated. To assess the motions of the ossicular chain, velocities at five points were measured with tonal stimuli of 1 and 3 kHz, which yielded reproducible results. The sequential amplitude change at each point was calculated with phase shifting from the tonal stimulus. Motion of the ossicular chain was visualized from the averaged results using the graphics application. Results: The head of the malleus and the body of the incus showed synchronized movement as one unit. In contrast, the stapes (incudostapedial joint and posterior crus) moved synchronously in opposite phase to the malleus and incus. The amplitudes at 1 kHz were almost twice those at 3 kHz. Conclusions: Our results show that the malleus and incus unit and the stapes move with a phase difference.