Yong-kyu Byun

Measurement of 6-DOF Displacement of Rigid Bodies through Splitting a Laser Beam: Experimental Investigation

12 In this paper, a new measuring system is proposed which can measure 6-DOF motion of rigid bodies. Its measurement principle is based on detection of laser beam reflected from a specially fabricated mirror whose shape is a triangular pyramid having an equilateral cross-sectional shape. The 3- facet mirror is mounted on the object whose 6-DOF displacement is to be measured. The measurement is operated by a laser-based optical system composed of a 3-facet mirror, a laser source, three position-sensitive detectors (PSD). In the sensor system, three PSDs are located at three corner points of a triangular formation, which is an equilateral triangular formation lying parallel to the reference plane. From this arrangement, 6-DOF displacement of any object can be simply determined. In this paper, we model the relationship between the 6-DOF displacement of the object and the outputs of three PSDs. A series of experiments is performed to demonstrate the effectiveness of the proposed method. The experimental results show that the proposed sensing system can be an effective means of obtaining 3D position and orientation of arbitrary objects.

Optimization of wide-bandwidth hard disk drive actuator design using statistical methods

As track density of hard disk drives is intensified, actuator dynamics has emerged as one of the most important design factors not only for high-performance models but also desktop applications. In spite of many different complex physical considerations required for successful wide-bandwidth actuator designs, most current design processes that rely purely upon designers experience-based historical approaches do not effectively account all factors to determine optimum design. A development of design optimization procedure for a high-performance actuator is presented in this paper. A position error signal (PES) estimator employing both numerical model and experimental data is developed for effective and accurate optimization process. Statistically formulated optimization method presented here delivers not only wide-bandwidth actuator design for PES reduction but higher shockproof HDA design. Furthermore the presented method incorporates volume production parameters so that designers are able to predict design tolerance and cost relations.

Measurement of vibrational motions using a three-facet mirror

A new measurement method to measure vibrational motions of objects is presented. The original principle is similar to the previous work that utilized a 3-facet mirror to obtain three dimensional positions and orientations of rigid bodies. While the previous work was presented for only stationary objects, in this paper, we newly investigate the feasibility of this method for dynamic applications. The 3-facet mirror that looks like a triangular pyramid having an equilateral cross-sectional shape. The mirror has three lateral reflective surfaces inclined 45 degrees to its bottom surface, and is mounted on the object whose motion is to be measured. As optical components, a He-Ne laser source and three position-sensitive detectors (PSD) are used. The laser beam is emitted from the He-Ne laser source located at the upright position and vertically incident to the top of the 3-facet mirror. The laser beam is reflected from the 3-facet mirror and splits into three sub-beams, each of which is reflected from the three facets and finally arrives at three PSDs, respectively. Since each PSD is a 2-dimensional sensor, we can acquire the information on the three dimensional position and orientation of the 3-facet mirror. From this principle, we can get the motion of any object simply by mounting the 3-facet mirror on the object. In this paper, the measurement principle and a series of experiments are presented. The experiments include measurements of vibrational motions of a piezoelectric actuator that moves the 3-facet mirror in a single axis. The experimental results are compared with those of a laser doppler vibrometer. Through the experiments, the proposed sensor is proven to be an effective means for measuring dynamic motions of objects.

Measurement of 3D position and orientation of rigid bodies using a three-facet mirror

In this paper, a new measuring system is proposed which can measure the 3D position and orientation of rigid bodies. Its measurement principle is based on detection of laser beam reflected from a specially fabricated mirror that looks like a triangular pyramid having an equilateral cross-sectional shape. The mirror has three lateral reflective surfaces inclined 45 degree(s) to its bottom surface. We call this mirror 3-facet mirror. The 3-facet mirror is mounted on the object whose position and orientation are to be measured. The measurement is operated by a laser-based optical system composed of a 3-facet mirror, a He-Ne laser source, three position-sensitive detectors.

suspension dynamics of HDD for high track density

As track density needs to increase to the order of 10, 000 tpi, the suspension has become a critical component in hard disk drives. One of the main obstacles to attain high track density is the structural resonances of the suspension in lateral direction. We investigate the suspension dynamics through the experimental modal analysis and the finite element method. An LDV (Laser Doppler Vibrometer) is employed to measure the response of the suspension which is excited by a shaker and an inpulse hammer for the free condition and the loaded condition, respectively. After comparing the experimental and numerical results, we study how the initial geometry of the bend region affects the suspension dynamics. It is found that the natural frequency of the sway mode decreases as the bend ratio and the bend angle increase. The shape of torsional mode changes as the mass of a slider increases, resulting in a local decrease in the natural frequency.