Computer machine systems employing optical technologies have been rapidly increasing in volume in our offices and homes. They are represented by image scanners, laser printers and optical memories. These systems are created by the integration of three basic hardware technologies : mechanics, electronics and optics, and software technologies. In the 1970's, the concept of mechatronics was born by integrating mechanics and electronics. With the recent progress of optical technologies, especially the development of semiconductor lasers the mechatronics concept is being advanced to opto-mechatronics. Focusing on information systems and measurement systems, the current status of the technology is described and its future trends are predicted.

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Magnetic actuators are a typical mechatronic product and are being applied now as rotor bearings or as suspension systems in aerospace, in physics, and in industry. With the intention to give a survey we will show some examples that make use of the specific advantages of the magnetic suspension principle, referring especially to vacuum techniques and to vibration control. Some conceptual choices in the design will be discussed, as the question of analogue versus digital control. Theoretical problems, related to key functions of the magnetic bearing system, will be addressed, demonstrating actual solutions and indicating future trends.

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This paper describes new systems for measuring mechanical and optical charac-teristics of optical disks. These characteristics are necessary for designing the head actuator and standard disks for high rotational speeds. The system for measuring mechanical characteristics uses a new lens actuator with high-speed servo perfor-mance. The magneto-optic (MO) signal quality is evaluated by measuring the birefrin-gence effects of the disk substrate. This paper also discusses disk stretch, which is important in considering data reliability at high rotational speeds.

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There are some projections on a surface of a magnetic disk after polishing. These projections influence the flight stability of the magnetic head. This paper describes a simple approximate method to calculate the static floating characteristic of the burnishing head. The difference between the calculated results and the experimental data is small. It is successful to design the burnishing head in the production of magnetic disk. The result experimental shows that the burnishing head can fly across the magnetic disk surface with 0.2μm height and remove projections on it.

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A new method of measuring impulsive forces arising from flying head/disk collision has been developed for tribological studies of head/medium interface. In this method it is possible to obtain impulsive forces as impulses in two directions quantitatively. The measurement results show that these impulses are in the order of 10^-6 [N.s], and that the impulse perpendicular to the disk face is proportional to the elastic coefticient of the air film. Moreover, in the case of a sputtered disk, flying head/disk contact time can be measured, so that it is possible to obtain a first approximation of contact force in one direction from the impulse. From this measurement, contact force in direction tangential to the disk surface is estimated to be in the order of 10^-3[N].

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We have developed a new control method for head positioning which improves positioning accuracy in magnetic disk drives. In the new faster and lighter head disk assemblies (HDAs), the base cannot be regarded as stationary. We analyzed the control characteristic of a conventional feedback controller exposed to different types of vibration using a model that includes disk and HDA motion. The results show that the conventional feedback controller does not have enough resistance against disturbances produced by mechanical resonances the HDA base or spindle. To improve controllability, we developed "acceleration feedforward control", which comepensates for disk motion by detecting an acceleration signal at the HDA base. Theoretically, this feedfefward can completely compensate for seek reaction and any other disturbance. Examination of the mechanical interaction between the dual actuators shows the effectiveness of this control method.

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Recently, smal1-sized rotating machinery such as turbomachines and flywheels are required to be driven at high rotational speeds and to maintain a clear environment. Active magnetic bearings can meet these requirements. The magnetic bearing system described here has been developed for high-speed rotating machinery. The model is a 4-axis-active type with a simple structure. Since the model is the so-cal1ed outer-rotor type, the resonance frequency of the rotor could be set higher than the rotating frequency, and only first-bending-mode frequency of the stator shaft is in the rotating region. In the high-frequency region, as the characteristics of the power amplifier become worse and the stability of the gyroscopic motion (nutation and precession) decreases, control of the flexible mode without adverse influence on another mode is very difficult. In this paper, a suppression method using stator's acceleration signal obtained from an observer circuit is discussed and compared to a conventional notch filter one.

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Recently, there has been an increase in the positioning accuracy required in the production processes for ULSI. For instance, in a wafer stepper for a 4-Mbit DRAM, the required positioning accuracy is said to be more than 0.04μm. There is also a requirement to reduce the positioning times in such processes. To meet these needs, a new laser measurement system which can accurately measure high speed displacement has been developed. When the target's speed is low, its displacement is measured by comparing the phase change of light reflected by the object with the phase modulated by an electro-optic crystal. When the target's speed is high, its displacement is measured using a fringe counting technique. The system achieves an accuracy of ±4nm and a maximum allowab1e measurement speed of 1OOO mm/s.

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The aim of this paper is the development of bearings with the following features : ( 1 ) ultrahigh precision, ( 2 ) infinite static stiffness, ( 3 ) high vibration damping capability, ( 4 ) new functions (axis positioning and dynamic stiffness control). For this purpose, an active air journal bearing (AAJB) is proposed. The AAJB is a new type of mechatronics bearing composed of noncontact sensors to detect the radial position of its axis, noncontact actuators (movable air pads driven by PZT actuators) to support and drive the axis, and a controller to regulate the whole system. An experimental AAJB is constructed and experiments prove that the AAJB has the following advantages : ( 1 ) an almost infinite static stiffness and an improved damping capability, ( 2 ) axis positioning over 8μm with a resolution better than l0nm, ( 3 ) an axis rotational accuracy better than 25nm at 1000rpm with an unbalanced load, ( 4 )quick and precise axis positioning at 1OOOrpm by a rectangular reference input.

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A vertical traverse wafer positioning stage was developed for X-ray stepper application in synchrotron radiation (SR) as an X-ray source. To ensure high accuracy of movement in vacuum /low-pressure helium conditions, the stage construction was split up into a coarse stepping stage and a fine positioning stage. For the coarse stepping stage, a linear air hydrostatic bearing (LAB) with a noncontact sealing device was developed to avoid lubrication problems. For the fine positioning stage, a multiaxis leaf spring guided and piezoelectric actuators employed stage was developed to attain high rigidity. The air leakage rate from each noncontact sealing device was less than 5.7x10^-4 Pa·m³/sec, so that the pressure of the vacuum chamber could reach 3 x 10^-3 Pa. Experiments on the coarse stepping stage show rotational movement error such as pitching and yawing to be less than ±6μrad with a repeatability of less than ±1μrad. The multiaxis fine positioning stage is also proved to have a sufticient small movement error.

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In order to obtain good printing quality with impact printers, a method of reducing vibration by carriage mounting printheads is investigated using a newly developed simulator for vibration analysis and experimental tests. As a result of a survey of various parameters, optimizing the carriage driving control pattern and increasing the stepper motor damping proved to be effective for decreasing carriage vibration. Consequently, significant improvement in printing quti1ity is obtained.

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In this report, practical noise reduction has been attempted for a dot-matrix impact printer. An about -5dB(A) noise reduction has been accomplished for the internal machinery noise by taking countermeasures for the internal machinery parts. The printer noise source was classified into the follwing four systems: printing head system, platen system, carriage system (stepping motor) and fans, and their contributions were estimated. The printing head and the platen system noise have much larger contributions than the others. Contermeasures for these have been taken. The noise reduction efficiency of the cover was investigated. Noise level decreases with decreasing aperture size? In an enclosed condition, average noise reduction efficiency was about -13dB(A). The dominant moise components were lower frequency noise, whose frequencies coincide with the basic printing frequency or are close to it.

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This paper investigates the dynamic characteristics of flying head sliders with ultra-thin spacing through a generalized lubrication equation based on the Boltzmann equation, and compares them with two limiting cases: approximations for bearing number ∧ → 0 and ∧ → ∞. These approximations agree well with numerical results in the limiting conditions. In particular, the approximation for ∧ → ∞ is found to quantitatively explain the characteristics of damping coefficients and correponding unstable phenomena.

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This paper describes two approaches for a development of an ultrahigh-speed serial printer. One is the development of ultrafast head carriage transport, which is controlled by a combination of feedfoward and feedback control elements. The feedforward control element is realized by a method which provides the optimal reference function with linear programming. The feedback control element is realized simultaneously by the optimal regulator theory and moda1 control theory. Printing head transport greater than 1.6 m/s velocity has been achieved by applying this control system to the experimental printer system. The second approach is the development of a generator which manipulates the printing wire drive control signal. Using this printing signal generator, precise printing (less than ±50μm dot positioning error) was accomplished while the carriage movement velocity was varied. These approaches have mode it possible for high-speed serial printers (more than 600 pica characters per second) to realize extreme improvement in printing throughput.

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The need for a high-resolution camera-type color image scanner has become much keener, because such a scanner would make good man-machine interaction and high-quality image acquisition possible. This type of scanner, however, needs a highly accurate servomechanism to scan a CCD array. We have developed a compact and highly accurate CCD array scanning servomechanism with the following features. 1) A compact scanning mechanism having magnetic circuits of the CCD array scanning linear motor in common with those of a color filter changing linear motor. 2) A color filter changing servomechanism having a color filter carriage which closely follows the CCD array scanning carriage. 3) A highly accurate (1/4000) position-sensing system employing another CCD array. By using this mechanism, a high-resolution (240 dots/inch for B4-size document) camera-type image scanner has been attained.

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This paper describes a vemier-type multiturn absolute encoder which uses a spatial filter to interpolate between encoder slit positions. The absolute angle can be derived from the optical encoder which uses an LED, photodiode array and coded disc consisting of three tracks. The accuracy of angular measurement for a prototype encoder was as high as 1/100000, and the encoder can respond up to 3000 rpm. The shaft revolutions are tallied by a magnetic bubble counter which uses a "memory wheel" principle to count up to 32487 turns. No electrical energy is used to store data or count revolutions.

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A precision automated assembly device which can carry out precision insertion is described. The device is composed of voice coil motors and is named VCM-Hand. We have developed a two = hyphen dimensional VCM-Hand operating in a plane surface with three degrees of freedom of motion for the insertion operation. The VCM-Hand realizes a unified treatment of control of forces, moment, compliances, dampings and positions by digital control. The following three major functions can be expected of the VCM-Hand : [A] a tactile sensing function of forces, moment and displacements : [B] a precision actuating function : [C] a variable compliance function (the flexible remote center compliance function). The VCM-Hand is expected to realize some advanced insertion methods by using the above three functions. It is also useful for comparing insertion methods proposed by other researchers.

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