Laser irradiation in liquid etchant using optical fibers is investigated in this report for debris-less grooving of single crystalline silicon. Little debris is observed around the grooves because laser ablated materials are successfully dissolved into KOH etchant. Oxide layer formed with H₂O₂ in the etchant simultaneously prevents the workpieces from unselective silicon etching by the alkaline. The optical fibers, one end is dipped into the etchant, provide a laser beam avoiding wobble of the laser spot. Width of the produced grooves is not depends on traverse speed besides depth of them decreases as the speed increases. The fact indicates the pulse duration of the Q-switched Nd:YAG laser, 6ns, is short enough to remove the materials without excessive heating of the materials out of the laser spot.

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It is important to reduce the edge damage in cleavage of sapphire substrate for cost reduction. In this study, the internal modification technique of a sapphire substrate by picosecond pulsed fiber laser were investigated. Internal modification of sapphire with a high aspect ratio such as 5µm width and 150µm height were successfully performed by the irradiation from the epitaxial layer side. A sapphire wafer of 0.4 mm thickness could be broken from the internal modified line without less damage of the epitaxial layer.

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Micro-holes of 100 to 300 µm were drilled through on cemented tungsten carbide plates of 0.5 and 1 mm thick by ultrafast laser pulses (150 fs at 800 nm, 1 kHz repetition rate) via a galvano-scanner with an 80 mm focal length lens. Effects of scan speed and polarization were examined. It is found that circularly polarized beam results in regular holes while linearly polarized beam produces distortions on their shape. Scan speed affects the shape of drilled hole, too. Laser induced periodic surface structures (LIPSS), which are formed at a period of 300 nm and oriented perpendicular to laser incident axis, were found on whole side of the hole drilled by circular polarized light. The formation of LIPSS by linearly polarized beam was dependent on the relative angle between the incident plane on the wall surface and the polarization direction.

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The violin is played by combining the fingering and bowing. Bowing is assumed that it has a big influence on the tone.This study sees bowing and control of bow speed and bow force. Purpose of this study is development of the device that plays the violin near man's performance.

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This paper describes the driving method and the control system design for ultra-precision fine motion stage with multi-layer electrostatic actuator of which electrodes are covered by isolation film and supported by only lubrication oil. The working range of an experimental electrostatic actuator is wider than 50micrometers. When the only lubrication oil is used for lubrication between the electrodes, electrostatic attractive forces produce large friction force with time and make the working range much small. In this paper, the suitable driving method is proposed to overcome the problem. The effectiveness of the proposed driving method was first examined by experiments in open-loop. Next, the performance of closed loop system with the driving method was evaluated. The closed loop system with the driving method shows the positioning accuracy better than 15nm.

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Motion synchronization of servo systems carries great importance in various precision manufacturing operations. For double-sided (duplex) milling of thin plates, in particular, the cutting tools must engage with both sides of workpiece in a precisely synchronized manner to avoid forced vibrations. A continuous sliding mode controller (SMC) is developed to deal with the problem of position synchronization for dual spindle servo systems. Synchronization error is defined as the differential position error between the two servo systems that follow same reference motion command. Hence, developed continuous SMC penalizes 3 error states; namely the individual servo positioning errors, and the synchronization error between them. As a result, individual trajectory tracking as well as motion coupling objective is introduced. The final control law is implemented in the form of a PID controller in real time, and double-sided milling experiments are performed to verify its effectiveness.

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It has been popular to use the sampled data control in positioning a mechanical stage system. Choosing a proper sampling rate in positioning control is important to improve the positioning accuracy and responsiveness. For this purpose, we make a control system that has a high speed sampling rate in order to control the position of an air bearing lead screw stage. In this paper, the characteristics of the mechanism and the results of the positioning control are described.

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This paper shows the experimental results of friction characteristics and positioning performance for servo motors with air bearings and rolling bearings. Although rolling bearings are widely adopted as a supporting mechanism in the positioning system with servo motor, it is well known that positioning performance deteriorates by the influence of nonlinear friction on the contact surface. In order to avoid the influence of nonlinear friction, air bearings are adopted to make shaft and bearing noncontact. In this paper, the difference of the characteristic is clarified by measuring nonlinear friction of each servo motor with rolling bearings and air bearings. In addition, the influence on the positioning performance by the difference of friction is verified by experiments.

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In the previous report, Peltier modules indirectly cooled the motor of the precision positioning device whose ball screw was connected with the motor shaft. As a result, the total thermal deformation drift (ball screw elongation and stage tilting motion) could be decreased to some extent. In this report, about the normal-type positioning device whose ball screw is connected to the motor shaft by a coupling, the each part of positioning device such as the moving stage and the support unit of ball bearing were cooled by Peltier modules to decrease the temperature-rise of the ball screw as same as the room temperature.

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Thermal errors are important sources of positioning errors in precision machines and are increasingly becoming determining factors to meet increasing specifications. In this paper, we introduce our ongoing research on the reduction of transient thermal errors in precision machines using design and control methodologies based on thermal modal analysis (TMA). TMA is a modal analysis technique applied to the thermal domain to reduce model complexity by the decomposition and the reassembly of a structure's thermal modes and related deformation shapes. The basic theory of TMA, its advantages and our preliminary result on 1D beam deformation control are presented.

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