Yoshiya Egashira

0.69 nm resolution ultrasonic motor for large stroke precision stage

This study reports the application of the non-resonant type ultrasonic motor (NRUSM) to a 300 mm-stroke ultra-precision stage for the future nanoelectronics manufacturing. The advantages of the NRUSM are high resolution and no magnetic noise generation due to the DC characteristics of the piezoelectric device, and high servo rigidity and no additional brake mechanism needed due to direct drive mechanism. It is confirmed that the NRUSM is suitable for ultra-precision positioning, slow and high velocity feeding at closed-loop control. The NRUSM driven stage performance results are; (1) maximum velocity 50 mm/s over the 300 mm-stroke at open-loop control; (2) positioning accuracy of /spl plusmn/0.69 nm at step and repeat response, and position accuracy at constant velocity feeding 10 nm/s /spl sim/36 mm/s below 20 nm at closed-loop control.

Development of nano-surgery system for cell organelles

A nano-surgery system has been developed for operation of minute organelles in a cell. such as chloroplast and mitochondria. For the operation, nano-pipettes, nano-manipulators, sample stage, and bellows pump were fabricated. It has been succeeded to prick a chromosphere in a plant cell and the membrane just under the nucleus of an animal cell with the tip of nano-pipette and to inject fluorescent dye into these organelles.

Development of an ultra-precision stage control system using nonresonant ultrasonic motor

This paper presents the development of an ultra-precision stage control system by introducing the nonresonant ultrasonic motor (NRUSM). System identification experiments are carried out considering the fundamental characteristic of NRUSM. The friction, which affects the accuracy of the positioning, is evaluated. Then the relation between the friction and the control bandwidth is experimentally examined. Using the frictional property as well as the identified model, the position control system with friction compensation is designed. Moreover, for its design the anti-windup-based wide band control is performed. Thus, the effectiveness of the identified model and the designed control system is verified by simulations and experiments.

Wear reduction method for frictionally fast feeding piezoactuator

A new wear reduction method, which is based on a static friction without slipping, is developed for a frictionally fast feeding piezoactuator. This method is required for overcoming the problems related to the scattering of particles due to the use of a contact type actuator. Furthermore, wear reduction result in a frictionally driving actuator with a long-term stability for various applications, such as the electron beam inspection in the next-generation semiconductor industry.

Highly Reliable Piezoelectric Actuator for Precision Stage System

A highly reliable nonresonant ultrasonic motor (NRUSM) made of cylindrical piezoelectric material is proposed in this paper. The high reliability is characterized by long lifetime and no outer gas in the vacuum environment, which are ensured by not using stack adhesives as the source of the gas emission. Positioning and tracking accuracy was better than below ±2 nm. The structural design is discussed in terms of the application to a high-speed high-precision stage system which has stable response to frequent biases without interference from resonant phenomena and the required mechanical strength.

Ultra-precision stage control based on friction model of non-resonant ultrasonic motor

This paper presents a friction model-based ultra-precision stage control that introduces the non-resonant ultrasonic motor (NRUSM). At first, the friction characteristic is experimentally evaluated as a function of the stage position. Next, the friction model is adopted for the proposed continuous-pass tracking control design, and then the efficiency of the model-based control is verified by positioning experiments. Finally, measuring the time variation of the static friction characteristics, the on-line identification method for the control system is proposed.

Slip-Free Driving Method for Nonresonant Piezoelectric Actuator

It is generally considered that in the ultrasonic motor the motion always slips and scratches. The nonresonant ultrasonic motor (NRUSM) expected for future precision stage systems should, however, overcome the difficulties of the wear of friction materials, which has been encountered in the use of conventional ultrasonic motors. The wear occurs by slipping and may be reduced by material selection. In this paper, we focus on the control method at actuation to prevent slipping. The advantages of NRUSM in the ability to control the drive frequency as well as the drive amplitude are shown, and this is effective in reducing wear and obtaining long-term stability. The drive frequency condition for no slippage under sinusoidal waveforms was calculated. The experimental results correspond to the theoretical calculated drive frequency. Because the resultant values of the frequencies are low for practical applications, we present the slip-free actuation method of using the new actuators driving waveform and time chart in order to drive the stage at constant accelerated motion.

Development of nonresonant ultrasonic motor with sub-nanometer resolution

Precise positioning, which is the base technology for ultra-precise treatments, is highly essential in semiconductor LSI circuits, bio-cells, molecular sensors, and quantum devices. Conflicting performances, high-speed, long-stroke, and high-resolution have been achieved by using die nonresonant ultrasonic motor (NRUSM) controlled under the piezoelectric effect. One of the notable features of the NRUSM is do the frequency of the driving voltage can be varied in a wide range, which means the motion control of the NRUSM can be done by both the amplitude and frequency The maximum stage feed velocity is 140 mm/s with average acceleration of 2200 mm/s/sup 2/ in the 100 mm stroke under open-loop control. 100 nm step response with /spl plusmn/0.69 nm positioning accuracy is completed in 0.35 s under closed-loop control.